WO2021163131A1 - Device, kit, and method for islet transplantation - Google Patents

Abstract

Provided herein are devices and methods useful for the treatment of islet cell transplantation. Also provided herein are devices and methods that are useful for the treatment diabetes and associated conditions, diseases, and disorders.

Description

DEVICE, KIT, AND METHOD FOR ISLET TRANSPLANTATION

CROSS REFERENCE TO RELTED APPLICATION [0001] This application claims the benefit of U.S. Provisional Application No. 62/972,558, filed February 10, 2020, which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Islet transplantation is the transplantation of isolated islets from a donor pancreas into the liver of type 1 diabetic patients with unstable glycemic control. Once transplanted, the islets begin to produce insulin and regulate the level of glucose in the blood. Islet cells must grow in a physiological environment rich in blood vessels and extracellular matrices. In order for successful engraftment, new blood vessels and supporting collagen matrix must be formed around and inside the graft to nourish and support the transplanted islet cells.

SUMMARY OF THE DISCLOSURE

[0003] In an aspect, provided herein is a method of transplanting a pancreatic islet cell population into a patient in need thereof, comprising: subcutaneously placing a removable scaffold comprising nano-sized features on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing the pancreatic islet cell population into the subcutaneous cavity.

[0004] In an aspect, provided herein is a method of transplanting a pancreatic islet cell population into a patient in need thereof, comprising: subcutaneously placing a removable scaffold comprising a biocompatible, hydrophilic polymer material at least on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing the pancreatic islet cell population into the subcutaneous cavity.

[0005] In an aspect, provided herein is a method of transplanting a pancreatic islet cell population into a patient in need thereof, comprising: subcutaneously placing a removable scaffold comprising nano-sized features formed by a biocompatible, hydrophilic polymer material on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing the pancreatic islet cell population into the subcutaneous cavity.

[0006] In an aspect, provided herein is a method of treating type 1 diabetes in a mammal, comprising: subcutaneously placing a removable scaffold comprising nano-sized features on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing a donor pancreatic islet cell population into the subcutaneous cavity, wherein the donor pancreatic islet cell population is supported by the microvasculature in or around the subcutaneous cavity to maintain survival and function of islet cells.

[0007] In an aspect, provided herein is a method of treating type 1 diabetes in a mammal, comprising: subcutaneously placing a removable scaffold comprising a biocompatible, hydrophilic polymer material at least on its exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing a donor pancreatic islet cell population into the subcutaneous cavity, wherein the donor pancreatic islet cell population is supported by the microvasculature in or around the subcutaneous cavity to maintain survival and function of islet cells.

[0008] In an aspect, provided herein is a method of treating type 1 diabetes in a mammal, comprising: subcutaneously placing a removable scaffold comprising nano-sized features formed by a biocompatible, hydrophilic polymer material on its exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing a donor pancreatic islet cell population into the subcutaneous cavity, wherein the donor pancreatic islet cell population is supported by the microvasculature in or around the subcutaneous cavity to maintain survival and function of islet cells.

[0009] In some embodiments, the function of the islet cells is insulin and/or glucagon secretion levels.

[0010] In some embodiments, the mammal recovers to normal glycemic. [0011] In some embodiments, the mean area under the curve (AUC) blood glucose is 2289 ± 107 mmol/L/120 min.

[0012] In some embodiments, the catheter does not trigger local atrophy of the subcutaneous muscle layer at the implantation site. In some embodiments, the scaffold does not trigger local atrophy of the subcutaneous muscle layer at the implantation site.

[0013] In an aspect, provided herein is a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter has nano-sized features to induce formation of microvasculature such that when catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity.

[0014] In some embodiments, the nano-sized features are formed by a material comprising a biocompatible, hydrophilic polymer.

[0015] In an aspect, provided herein is a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity.

[0016] In some embodiments, the scaffold does not trigger local atrophy of the subcutaneous muscle layer at the implantation site.

[0017] In some embodiments, the scaffold has hierarchical pore architecture.

[0018] In some embodiments, the outer diameter of the scaffold is up to about 3.0 mm.

[0019] In some embodiments, the inner diameter of the scaffold is up to about 2.0 mm.

[0020] In some embodiments, the scaffold has a length of about 2 cm.

[0021] In some embodiments, the scaffold has a nano-fiber morphology.

[0022] In an aspect, provided herein is a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises nano-sized and a biocompatible, hydrophilic polymer material that induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity.

[0023] In an aspect, provided herein is a kit, comprising: a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter has nano-sized features to induce formation of microvasculature such that when catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and an islet cell population in a pharmaceutically acceptable carrier [0024] In an aspect, provided herein is a kit, comprising: a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and an islet cell population in a pharmaceutically acceptable carrier.

[0025] In an aspect, provided herein is a kit, comprising: a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises nano-sized and a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and an islet cell population in a pharmaceutically acceptable carrier.

[0026] In some embodiments, the catheter does not trigger local atrophy of the subcutaneous muscle layer at the implantation site.

INCORPORATION BY REFERENCE

[0027] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS [0028] The novel features of the disclosure are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the disclosure are utilized, and the accompanying drawings of which: [0029] FIG. 1 is a schematic illustration of the design principle of the subcutaneous (SubQ) pre vascularized DL cellular transplant site.

[0030] FIGS. 2A-2H show the histological analysis of the islet cell implantation site. (2A) Masson’s trichrome staining of the cross-section of the pre-vascularized device-less (DL) site after removal of the PLGA nanofiber catheter that had been implanted for 2 weeks. Islets were infused into the resulting DL space (*). Collagen (blue), smooth muscle and erythrocytes (red) at 4x. (2B) Fluorescent staining of the same cross-section stained for blood vessels (green) and nuclei (blue) at 4*. (2C) Fluorescent staining at 4 ^c of an islet graft in the DL site at 2 days after transplant, stained for insulin (red), blood vessels (green) and nuclei (blue). (2D) Fluorescent staining of the same section stained for insulin (red), glucagon (green) and nuclei (blue). (2E, 2F) Masson’s trichrome staining and Hematoxylin and eosin staining of an islet graft cross-section, 100 days after transplant at 4 x, surrounded by collagen and blood vessels. (2G) Fluorescent staining of the same cross-section stained for insulin (red), blood vessels (green) and nuclei (blue) at 4x. (2H) Fluorescent staining of the same cross-section stained for insulin (red), glucagon (green) and nuclei (blue) at 4x. Scale bars, 100 pm.

[0031] FIGS. 3A-3R show the proinflammatory response elicited by angio-catheters composed of nylon (square) or PLGA (triangle) when implanted subcutaneously for 24h, 1 week, and 2 weeks. (3A-3R); the peri -implant concentrations of IL-Ib (3A-3C), IL-6 (3D-3F), IL-10 (3G- 31), TNF-a (3J-3L), KC/GRO (3M-30) and IL-12p70 (3P-3R). Data points represent mean ± s.e.m. for pg/g tissue, *p < 0.05, **p < 0.01, ***p < 0.001 (n = 3/time point). One-way ANOVA was calculated with Newman-Keuls post-hoc testing for multiple comparisons between controls and individual biomaterials tested. Y Axis labels for all graphs indicated in left margin.

[0032] FIGS. 4A-4B show long-term function of syngeneic islet grafts transplanted into the DL site. (A) Percent glycemic for kidney capsule (KC) recipients (n = 10), and DL site recipients (n = 28), and unmodified subcutaneous space (Sub-Q, n = 10) 100 days after transplant (p = 0.001, log-rank, Mantel-cox test). (B) Non-fasting blood glucose measurements. Shaded area represents a nonfasting physiological range ( < 11.1 mM). Data points represent blood glucose mean ± s.e.m. Islets transplanted were from ten separate islet isolations (n = 10).

[0033] FIGS. 5A-5B show intraperitoneal glucose tolerance tests (IPGTTs) of syngeneic mouse islets transplanted into the KC or into the DL space, 100 days after transplant. (A) Blood glucose post-dextrose bolus (B) area under the curve (AUC) analysis did not differ between the KC (n = 10) and DL space (n = 28) recipients (p > 0.05, one-way ANOVA with Newman-Keuls post-hoc testing for multiple comparison between transplant groups). Naive represents nondiabetic, non- transplanted BALB/c mice (black, n = 6), which were more tolerant to the metabolic test than the PL space recipients (**p < 0.01, p > 0.05, one-way ANOVA with Newman-Keuls post-hoc testing for multiple comparison to naive controls). Animals receiving islets in the unmodified Sub-Q (n = 6), were intolerant to the glucose challenge compared to DL space recipients (***p < 0.001 one-way ANOVA with Newman-Keuls post-hoc testing for multiple comparison between transplant groups). Mice were administered 3 g/kg 50 % dextrose i.p. Blood glucose measurements were monitored at t = 0, 15, 30, 60, 90 and 120 min. Data points represent blood glucose mean ± s.e.m. Islets transplanted were from ten separate islet isolations (n = 10). n.s., not significant.

[0034] FIGS. 6A-6G show long-term function of monkey islets transplanted into the DL space. (6A) Non-fasting blood glucose measurements showed maintenance of normoglycemia until the time of graft retrieval (arrow), at which point recipients reverted to the pretransplant hyperglycemic state (n = 2 monkey donors). (6B, 6E) Masson’s trichrome staining of a long term (>100 days) monkey islet graft in the DL site at 4x, surrounded with collagen and blood vessels. (C, F) Fluorescent staining of the same cross-section staining for insulin, glucagon and nuclei at 4*. (6D, 6G) 10* of white frame from (6C, 6F), respectively. Scale bars, 200 pm. [0035] FIGS. 7A-7F show SEM images of (7A, 7B) PLGA; (7C, 7D) nylon catheters. 7A, 7C show images of the cross-section and 7B and 7D show the outer surface morphology of the PLGA and nylon catheter, respectively. The insets in 7B and 7D indicate higher magnification of the red box. The outer surface water contact angle images of PLGA (7E) and the nylon catheter (7F). Scale bars: 7A, 7C: 500 pm; 7B, 7D: 40 pm.

[0036] FIGS. 8A-8H show an overview of the subcutaneous, pre-vascularized device-less (DL) site transplant approach. (8 A) DL transplant site where a 1.5 mm outer diameter nano-fiber textured PLGA catheter is implanted beneath the skin; (8B-8D) left for a period of 2 weeks; (8E) removed; (8F) subsequent to the implant period, the PLGA nano-fiber catheter is removed (8E) vascularized lumen where the islet transplant is infused; (8F) the islets are then infused via PE50 tubing; (8G) the incision site closed with tissue suture glue; and (8H) the islet graft.

[0037] FIGS. 9A-9F show a histological analysis of the DL site before islet cell transplantation. (9A-9C) Masson’s trichrome staining of the cross-section of the DL site after removal of the PLGA nano-fiber, Nylon and Silicone catheter. Islets were infused into the resulting DL (*). Creation of a PLGA-based DL space requires 2 weeks, while a nylon- or silicone-based DL space requires 4 weeks. Collagen (blue), smooth muscle and erythrocytes (red) at 4x magnification. (9D-9F) fluorescent staining of the same cross-section stained for blood vessels (green) and nuclei (blue) at 4 x magnification. Scale bars, 100 pm.

[0038] FIGS. 10A-10C show scatter distribution of cytokine and chemokines elicited by nylon (blue) or PLGA (red) when subcutaneously implanted for (10A) 24 hours; (10B) 1 week; and (IOC) 2 weeks. [0039] FIG. 11 shows rate of diabetes reversal, defined as percent euglycemic, in mouse recipients of syngeneic BALB/c islet grafts. Glycemic control, measured by twice weekly non fasting blood glucose levels, was monitored for 60 days post-islet transplant in chemically induced (STZ) diabetic mice. Reversal of diabetes was defined as a maintained non-fasting blood glucose level of <11.1 mM. Recipients received 50 BALC/c islets. Islet transplant groups: kidney capsule (KC-·, n=10), subcutaneous alone (Sub-Q-T, n=6), pre-vascularized ‘DL’ PLGA (PLGA-·, n=28) and pre-vascularized DL’ nylon (Nylon - A, n=18). Data points represent blood glucose mean ± s.e.m. Islets transplanted were from 10 separate isolations (n=10).

[0040] FIGS. 12A-12B show IPGTTs in syngeneic BALB/c islet recipients. Intraperitoneal glucose tolerance tests (3g/kg 50 % dextrose intraperitoneal) in syngeneic BALB/c islet recipients under the KC or DL site, at 60 days post-transplant. (12A) Blood glucose postdextrose bolus (12B) AUC analysis did not differ between the KC (n=10) and PLGA-DL (n=28) recipients (p NS, one-way Anova-Newman-keuls post-hoc). PLGA-DL profiles were significantly improved compared to Nylon-DL (n=18), (**p<0.01 one-way Anova-Newman- keuls post-hoc). Islets transplanted beneath the skin without prevascularization, (Sub-Q , n=6), demonstrated diabetic profiles (***p<0.001 one-way Anova-Newman-keuls post-hoc test, compared with PLGA-DL). Naive were normal, nondiabetic control BALB/c mice (n=6), and showed most optimal glycemic profiles (**p <0.01 and ***p<0.001 compared with Nylon-DL and KC respectively, one-way Anova-Newman-keuls post-hoc). Blood glucose was measured at 0, 15, 30, 60, 90, and 120 minutes. Data points represent blood glucose mean ± s.e.m. Islets transplanted were from 10 separate isolations (n=10).

[0041] FIGS. 13A-13C show histological analysis of representative syngeneic (BALB/c) islet grafts transplanted beneath the skin without pre-vascularization. (13A) Hematoxylin & eosin staining and (13B) Mason trichrome staining of cross-section of a subcutaneous islet graft at 4x. (13C) Fluorescent staining of the same cross-section stained for insulin (red), blood vessels (green) and nuclei (blue) at 10*. Without pre-vascularization, islet necrosis and inflammatory destructive response ensued, resulting in graft loss at 14 days post-transplant. Scale bars, 40 pm. [0042] FIGS. 14A-14C show vascular density of islet grafts post-transplantation. (14A) Islets transplanted into the unmodified subcutaneous space (green: Sub-Q Tx, n=6) had markedly less graft neovascularization compared to islets transplanted into the pre-vascularized PL site (blue: DL Tx, n=8) (p < 0.001, unpaired t-test). Vascular density was quantified by measuring percentage of islet grafts staining positive for the vascular wall marker, von Willebrand (vWF) (green), using ImageJ software (ImageJ, National Institutes of Health, Bethesda MD). Representative images of vWF positive staining within (14B) subcutaneous and (14C) DL islet grafts. Scale bar represents 100 pm. Values represent mean percentage of graft staining positive for vWF ± s.e.m.

[0043] FIG. 15 shows time to normoglycemia in C57BL/6 vs. BALB/c mouse strains. Time to normoglycemia in C57BL/6 (n=l 1) vs. BALB/c (n=28) mouse strains, using the PL subcutaneous approach. Glycemic control was measured three times per week with non-fasting glucose levels, and reversal of diabetes defined as glucose < ll.lmM. C57BL/6 mice reversed diabetes at a more rapid rate than BALB/c mice (13.6 ± 4.7 vs. 25.8 ± 0.8 days, p<0.05, unpaired t-test). Data points represent mean days post-transplant ± s.e.m. C57BL/6 transplants were conducted from 3 separate isolation isolations. BALB/c transplants were conducted from 4 separate islet isolations (n=10 pancreata per isolation).

[0044] FIG. 16 shows mice were rendered diabetic 7 days ahead of DL catheter placement, and remained diabetic for a further 2 weeks before transplantation of 50 syngeneic islets. Glycemic control, measured by three times per week, was monitored for 50 days post-islet transplant in chemically induced streptozotocin (STZ) diabetic mice. Reversal of diabetes was defined as glucose <11.1 mM. No significant difference was found between pre-existing diabetic state (n=8) vs. post DL catheter placement diabetic state (n=23), upon subsequent islet engraftment (p NS, log-rank, Kaplan-Meier). Islets were transplanted from 15 separate islet isolations (n=10 ancreata per isolation).

[0045] FIG. 17 shows Impact of an allogeneic barrier upon diabetes reversal using the DL subcutaneous site. 10 BALB/c islets were transplanted within the DL space of STZ-diabetic C57BL/6 mice, in the presence or absence of immunosuppression (I.S.). Control mice (n=6) initially reversed diabetes, but then rapidly rejected allogeneic islet grafts. By contrast, with tacrolimus-based immunosuppression (0.5mg/kg/day for 28 days, n=3, subcutaneously via Alzet® mini-osmotic pump, (Alzet Cupertino, CA), rejection was delayed, and a proportion of grafts continued to function > 60 days. Hyperglycemia occurred promptly upon graft explanation. Kidney sub-capsular allogeneic grafts (data not shown) rejected in a similar time- course.

DETAILED DESCRIPTION OF THE DISCLOSURE [0046] Provided herein are removable scaffolds for inducing formation of microvasculature to support the subcutaneous transplantation of islet cells. The removable scaffolds comprise a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter has nano-sized features and/or a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity. In some embodiments, the biocompatible, hydrophilic polymer material is poly (lactic- co-gly colic acid) (PLGA). The present disclosure recognizes the technical effects of subcutaneous placement of a removable scaffold as set forth herein, including but not limited to, formation of a subcutaneous cavity rich in microvasculature. Additionally, subcutaneous implantation of the removable scaffolds as set forth herein avoid local atrophy of the subcutaneous muscle layer at the implantation site while stimulating formation of an environment rich in blood vessels and extracellular matrices (e.g., supporting collagen matrix) to nourish and support subcutaneously transplanted islet cells. Described herein in one aspect are removable scaffolds for the treatment of diabetes, including the initial or first-line treatment of diabetes.

[0047] Provided herein is a PLGA-based biodegradable nano-fiber catheter that quickly creates an ideal subcutaneous device-less (DL) site for successful transplantation of mouse or monkey islet cells in mice. PLGA is an FDA-approved biodegradable biomaterial that can be applied to the human body. As disclosed herein, a nano-fiber PLGA catheter with hierarchical pore architecture is used to create a subcutaneous micro-vascular dense DL space, which aims to harness the innate foreign body reaction in a controlled manner to induce a microenvironment that is conducive to islet cell survival and function realization. A hollow nano-fiber PLGA catheter is implanted subcutaneously to cause a foreign body reaction and is removed after two weeks. Quickly eliminating foreign body reactions leave a space rich in new blood vessels (FIG. 1 and FIGS. 8B and 4D). Transplantation of islet cells into this site allows for the reversal of diabetes without the need for permanent encapsulation devices or exogenous growth factors. Certain Terminology

[0048] As used herein and in the appended claims, the singular forms “a,” “and,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a scaffold” includes a plurality of such scaffolds, and reference to “the catheter” includes reference to one or more catheters (or to a plurality of catheters) and equivalents thereof known to those skilled in the art, and so forth. When ranges are used herein for physical properties, such as molecular weight, or chemical properties, such as chemical formulae, all combinations and sub-combinations of ranges and specific embodiments therein are intended to be included. The term “about” when referring to a number or a numerical range means that the number or numerical range referred to is an approximation within experimental variability (or within statistical experimental error), and thus in some embodiments, the number or numerical range varies between 1% and 10% of the stated number or numerical range. The term “comprising” (and related terms such as “comprise” or “comprises” or “having” or “including”) is not intended to exclude that in other certain embodiments, for example, an embodiment of any composition of matter, composition, method, or process, or the like, described herein, may “consist of’ or “consist essentially of’ the described features.

Definitions

[0049] As used in the specification and appended claims, unless specified to the contrary, the following terms have the meaning indicated below.

[0050] “Pharmaceutically acceptable salt” as used herein includes both acid and base addition salts. In some embodiments, the pharmaceutically acceptable salt of any one of the compounds described herein is the form approved for use by the US Food and Drug Administration. Preferred pharmaceutically acceptable salts of the compounds described herein are pharmaceutically acceptable acid addition salts and pharmaceutically acceptable base addition salts.

[0051] The term “acceptable” with respect to a formulation, composition or ingredient, as used herein, means having no persistent detrimental effect on the general health of the subject being treated.

[0052] The terms “administer,” “administering,” “administration,” and the like, as used herein, refer to the methods that may be used to enable delivery of compounds or compositions to the desired site of biological action. These methods include, but are not limited to, oral routes, intraduodenal routes, parenteral injection (including intravenous, subcutaneous, intraperitoneal, intramuscular, intravascular or infusion), topical, and rectal administration. Those of skill in the art are familiar with administration techniques that can be employed with the compounds and methods described herein. In some embodiments, the compounds and compositions described herein are administered orally.

[0053] The term “subject” or “patient” encompasses mammals. Examples of mammals include, but are not limited to, any member of the Mammalian class: humans, non-human primates such as chimpanzees, and other apes and monkey species; farm animals such as cattle, horses, sheep, goats, swine; domestic animals such as rabbits, dogs, and cats; laboratory animals including rodents, such as rats, mice and guinea pigs, and the like. In one aspect, the mammal is a human. [0054] As used herein, “treatment” or “treating” or “palliating” or “ameliorating” are used interchangeably herein. These terms refer to an approach for obtaining beneficial or desired results including but not limited to anti-diabetic effect, therapeutic benefit and/or a prophylactic benefit. By “therapeutic benefit” or “anti-diabetic effect” is meant eradication or amelioration of the underlying disorder being treated. A therapeutic benefit is achieved with the eradication or amelioration of one or more of the physiological symptoms associated with the underlying disorder (e.g., an improvement in: hyperglycemia, polyuria, polydipsia, polyphagia, diabetic dermadromes, etc.) such that an improvement is observed in the patient, notwithstanding that the patient may still be afflicted with the underlying disorder. Also, a therapeutic benefit is achieved with the eradication or amelioration of one or more of the complications associated with the underlying disorder (e.g., cardiovascular disease). For prophylactic benefit, the compositions may be administered to a patient at risk of developing a particular disease, or to a patient reporting one or more of the physiological symptoms of a disease, even though a diagnosis of this disease may not have been made.

[0055] The terms “diabetes” and “diabetes mellitus” are used interchangeably herein. These terms refers to type 1 diabetes mellitus, type 2 diabetes mellitus, complications of diabetes mellitus, and of neighboring disease states. As used herein, diabetes or diabetes mellitus (DM) refers to a group of metabolic disorders in which there are high blood sugar levels over a prolonged period.

[0056] "Polymer" as used herein, refers to a series of repeating monomeric units that have been cross-linked or polymerized. Any suitable polymer can be used to carry out the present invention. It is possible that the polymers of the invention may also comprise two, three, four or more different polymers. In some embodiments, of the invention only one polymer is used. In some preferred embodiments a combination of two polymers are used. Combinations of polymers can be in varying ratios, to provide coatings with differing properties. Those of skill in the art of polymer chemistry will be familiar with the different properties of polymeric compounds. Examples of ploymers that may be used in the present invention include, but are not limited to polycarboxylic acids, cellulosic polymers, proteins, polypeptides, polyvinylpyrrolidone, maleic anhydride polymers, polyamides, polyvinyl alcohols, polyethylene oxides, glycosaminoglycans, polysaccharides, polyesters, polyurethanes, polystyrenes, copolymers, silicones, polyorthoesters, polyanhydrides, copolymers of vinyl monomers, polycarbonates, polyethylenes, polypropylenes, polylactic acids, polyglycolic acids, polycaprolactones, polyhydroxybutyrate valerates, polyacrylamides, polyethers, polyurethane dispersions, polyacrylates, acrylic latex dispersions, polyacrylic acid, mixtures and copolymers thereof. The polymers of the present invention may be natural or synthetic in origin, including gelatin, chitosan, dextrin, cyclodextrin, Poly(urethanes), Poly(siloxanes) or silicones, Poly(acrylates) such as poly(methyl methacrylate), poly(butyl methacrylate), and Poly(2- hydroxy ethyl methacrylate), Poly(vinyl alcohol) Poly(olefms) such as poly(ethylene), poly(isoprene), halogenated polymers such as Poly(tetrafluoroethylene) - and derivatives and copolymers such as those commonly sold as Teflon® products, Poly(vinylidine fluoride), Poly(vinyl acetate), Poly(vinyl pyrrolidone),. Poly(acrylic acid), Polyacrylamide, Poly(ethylene- co-vinyl acetate), Poly(ethylene glycol), Polypropylene glycol), Poly(methacrylic acid); etc. Suitable polymers also include absorbable and/or resorbable polymers including the following, combinations, copolymers and derivatives of the following: Polylactides (PLA), Polyglycolides (PGA), Poly(lactide-co-glycolides) (PLGA), Polyanhydrides, Polyorthoesters, Poly(N-(2- hydroxypropyl) methacrylamide), Poly(l-aspartamide), etc.

[0057] Removable Scaffolds/Kits

[0058] A hollow PLGA catheter with hierarchical nanofibers architecture that can quickly produce a subcutaneous pre-vascularized DL collagen matrix space, which supports islet cells transplantation, was developed. The obtained nanofibers PLGA catheter possess hydrophilic nanofiber interface and degradable acidic small molecule LA, which is helpful to the nanofibers PLGA catheter quickly induce a biocompatibility pre-vascularized DL space in a controlled foreign-body response of different mice strains. This pre-vascularized DL space induced by PLGA nanofiber catheters can provide the best living microenvironment for islet cells. The observations showed that the designed nanofibre PLGA catheter could create an optimal long term survival space for islet cell transplantation.

[0059] Described herein are removable scaffolds for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter has nano-sized features to induce formation of microvasculature such that when catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity.

[0060] In some embodiments, the nano-sized features are formed by a material comprising a biocompatible, hydrophilic polymer.

[0061] In an aspect, provided herein is a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity.

[0062] In some embodiments, the biocompatible, hydrophilic polymer comprises nano-sized features.

[0063] In an aspect, provided herein is a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises nano-sized and a biocompatible, hydrophilic polymer material that induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity.

[0064] In an aspect, provided herein is a kit, comprising: a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter has nano-sized features to induce formation of microvasculature such that when catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and an islet cell population in a pharmaceutically acceptable carrier [0065] In an aspect, provided herein is a kit, comprising: a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and an islet cell population in a pharmaceutically acceptable carrier.

[0066] In an aspect, provided herein is a kit, comprising: a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises nano-sized and a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and an islet cell population in a pharmaceutically acceptable carrier.

[0067] In some embodiments, the catheter does not trigger local atrophy of the subcutaneous muscle layer at the implantation site.

[0068] In some embodiments, the biocompatible, hydrophilic polymer material is a block co polymer. In some embodiments, the biocompatible, hydrophilic polymer material is poly (lactic- co-gly colic acid) (PLGA).

[0069] In some embodiments, the lactide/glycolide molar ratio of the PLGA is about 75:25. [0070] In some embodiments, the inherent viscosity of the PLGA is about O.ndL-¹.

[0071] In some embodiments, the catheter has hierarchical pore architecture.

[0072] In some embodiments, the outer diameter of the catheter is up to about 3.0 mm. In some embodiments, the outer diameter of the catheter is from about 0.5 mm to about 5.0 mm. In some embodiments, the outer diameter of the catheter is from about 1.0 mm to about 5.0 mm. In some embodiments, the outer diameter of the catheter is from about 1.5 mm to about 5.0 mm. In some embodiments, the outer diameter of the catheter is from about 2.0 mm to about 5.0 mm. In some embodiments, the outer diameter of the catheter is from about 2.5 mm to about 5.0 mm. In some embodiments, the outer diameter of the catheter is from about 0.5 mm to about 4.5 mm. In some embodiments, the outer diameter of the catheter is from about 0.5 mm to about 4.0 mm. In some embodiments, the outer diameter of the catheter is from about 0.5 mm to about 3.5 mm.

[0073] In some embodiments, the outer diameter of the catheter is from about 1.0 mm to about

3.5 mm. In some embodiments, the outer diameter of the catheter is from about 1.5 mm to about

3.5 mm. In some embodiments, the outer diameter of the catheter is from about 2.0 mm to about

3.5 mm. In some embodiments, the outer diameter of the catheter is from about 2.5 mm to about

5.0 mm. In some embodiments, the outer diameter of the catheter is about 0.5, about 0.6, about

0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about

1.6, about 1.7, about 1.8, about 1.9, about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, about

2.5, about 2.6, about 2.7, about 2.8, about 2.9, about 3.0, about 3.1, about 3.2, about 3.3, about

3.4, about 3.5, about 3.6, about 3.7, about 3.8, about 3.9, about 4.0, about 4.1, about 4.2, about

4.3, about 4.4, about 4.5, about 4.6, about 4.7, about 4.8, about 4.9, or about 5.0 mm.

[0074] In some embodiments, the inner diameter of the catheter is up to about 2.0 mm. In some embodiments, the inner diameter of the catheter is from about 0.5 mm to about 5.0 mm. In some embodiments, the inner diameter of the catheter is from about 1.0 mm to about 5.0 mm. In some embodiments, the inner diameter of the catheter is from about 2.0 mm to about 5.0 mm. In some embodiments, the inner diameter of the catheter is from about 2.5 mm to about 5.0 mm. In some embodiments, the inner diameter of the catheter is from about 0.5 mm to about 4.5 mm. In some embodiments, the inner diameter of the catheter is from about 0.5 mm to about 4.0 mm. In some embodiments, the inner diameter of the catheter is from about 0.5 mm to about 3.5 mm. In some embodiments, the inner diameter of the catheter is from about 0.5 mm to about 3.0 mm. In some embodiments, the inner diameter of the catheter is from about 0.5 mm to about 2.5 mm. In some embodiments, the inner diameter of the catheter is from about 1.5 mm to about 5.0 mm. In some embodiments, the inner diameter of the catheter is from about 0.1 mm to about 5.0 mm. In some embodiments, the inner diameter of the catheter is from about 0.5 mm to about 4.0 mm. In some embodiments, the inner diameter of the catheter is from about 1.0 mm to about 3.5 mm. In some embodiments, the inner diameter of the catheter is from about 1.5 mm to about 3.0 mm. In some embodiments, the inner diameter of the catheter is from about 1.5 mm to about 3.0 mm. In some embodiments, the inner diameter of the catheter is from about 2.0 mm to about 3.0 mm. In some embodiments, the inner diameter of the catheter is about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, about 2.9, about 3.0, about 3.1, about 3.2, about 3.3, about 3.4, about 3.5, about 3.6, about 3.7, about 3.8, about 3.9, about 4.0, about 4.1, about 4.2, about 4.3, about 4.4, about 4.5, about 4.6, about 4.7, about 4.8, about 4.9, or about 5.0 mm.

[0075] In some embodiments, the catheter has a length of about 2 cm. In some embodiments, the catheter has a length of from about 0.5 cm to about 6.0 cm. In some embodiments, the catheter has a length of from about 1.0 cm to about 6.0 cm. In some embodiments, the catheter has a length of from about 1.5 cm to about 6.0 cm. In some embodiments, the catheter has a length of from about 0.5 cm to about 5.5 cm. In some embodiments, the catheter has a length of from about 0.5 cm to about 5.0 cm. In some embodiments, the catheter has a length of from about 0.5 cm to about 4.5 cm. In some embodiments, the catheter has a length of from about 0.5 cm to about 4.0 cm. In some embodiments, the catheter has a length of from about 0.5 cm to about 3.5 cm. In some embodiments, the catheter has a length of from about 0.5 cm to about 3.0 cm. In some embodiments, the catheter has a length of from about 0.5 cm to about 2.5 cm.

[0076] In some embodiments, the catheter has a length of about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about

1.7, about 1.8, about 1.9, about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, about 2.5, about

2.6, about 2.7, about 2.8, about 2.9, about 3.0, about 3.1, about 3.2, about 3.3, about 3.4, about

3.5, about 3.6, about 3.7, about 3.8, about 3.9, about 4.0, about 4.1, about 4.2, about 4.3, about

4.4, about 4.5, about 4.6, about 4.7, about 4.8, about 4.9, or about 5.0 cm.

[0077] In some embodiments, the catheter has a nano-fiber morphology.

[0078] In some embodiments, the polymer is biodegradable.

[0079] In some embodiments, the scaffolds comprise catheters. In some embodiments, the scaffolds and/or catheters comprise a polymeric core layer. In some embodiments, the polymeric core layer is nylon. In some embodiments, the scaffolds and/or catheters comprise a polymeric core layer coated with a biocompatible, hydrophilic polymer. In some embodiments, the scaffolds and/or catheters comprise a polymeric core layer coated with a polymer comprising a nano-fiber morphology. In some embodiments, the scaffolds and/or catheters comprise a polymeric core layer coated with a polymer comprising hierarchical pore architecture. In some embodiments, the scaffolds and/or catheters comprise a polymeric core layer coated with a biocompatible, hydrophilic polymer comprising a nano-fiber morphology. In some embodiments, the scaffolds and/or catheters comprise a polymeric core layer coated with poly (lactic-co-gly colic acid) (PLGA). [0080] Poly (lactic-co-glycolic acid) (PLGA)

[0081] Poly(alpha-hydroxy carboxylic acids) include polymers of lactic acid, polymers of glycolic acid, and co-polymers of lactic acid and glycolic acid (PLGA). Poly (alpha- hydroxy carboxylic acids), are a group of copolymers approved for numerous therapeutic uses owing to its biodegradability and biocompatibility. PLGA is prepared by the ring-opening polymerization of the cyclic dimers (l,4-dioxane-2,5-dione) of glycolic acid and lactic acid. Catalysts used to initatiate the ring-open polymerization include tin(II) alkoxides or aluminium alkoxides. PLGA has good solubility in many organic solvents. Different forms of PLGA, with varying rates of hydrolysis, are produced by varying the ratio of glycolic acid monomer to lactic acid monomer. In addition, co-polymers in which the carboxy terminus is capped with an alkyl group have enhanced stability. Provided herein is a composition comprising a poly(alpha- hydroxy carboxylic acid) substantially free of acidic impurities.

[0082] In one embodiment is a composition comprising poly(D,L-lactic-co-gly colic acid) substantially free of acidic impurities.

[0083] In another embodiment is a composition comprising poly(L-lactic acid) substantially free of acidic impurities.

[0084] In another embodiment is a composition comprising poly(D-lactic acid) substantially free of acidic impurities.

[0085] In another embodiment is a composition comprising poly(D,L-lactic acid) substantially free of acidic impurities.

[0086] In some embodiments, the poly(D,L-lactic-co-gly colic acid) contains less than 0.5 % (wt/wt) of acidic impurity. In some embodiments, the poly(D,L-lactic-co-gly colic acid) contains less than 1.0 % (wt/wt) of acidic impurity. In some embodiments, the poly(D,L-lactic-co- gly colic acid) contains less than 1.5 % (wt/wt) of acidic impurity. In some embodiments, the poly (D,L-lactic-co-gly colic acid) has a ratio of lactic acid monomer to glycolic acid monomer ranging from 95:5 to 65:35. In some embodiments, the poly(D,L-lactic-co-gly colic acid) has a ratio of lactic acid monomer to glycolic acid monomer ranging from 85:15 to 65:35. In some embodiments, the poly(D,L-lactic-co-gly colic acid) has a ratio of lactic acid monomer to glycolic acid monomer ranging from 80:20 to 70:30.

[0087] In some embodiments, the poly(D,L-lactic-co-gly colic acid) has a weight average molecular weight of about 4,000 to about 8,000. In some embodiments, the poly(D,L-lactic-co- gly colic acid) has a weight average molecular weight of about 8,000 to about 12,000. In some embodiments, the poly(D,L-lactic-co-gly colic acid) has a weight average molecular weight of about 12,000 to about 16,000. In some embodiments, the poly(D,L-lactic-co-gly colic acid) has a weight average molecular weight of up to about 50 kDalton. In some embodiments, the poly(D,L-lactic-co-gly colic acid) has a weight average molecular weight of up to about 90 kDalton. In some embodiments, the poly(D,L-lactic-co-gly colic acid) has a weight average molecular weight of up to about 120 kDalton.

[0088] Islet Cells

[0089] Implantation of donor cells or other foreign bodies into an affected patient have successfully accomplished treatment of various conditions and diseases. For example, pancreatic islet beta-cells are known to sense blood sugar levels and secrete insulin to maintain homeostasis. In patients with diabetes, however, islet beta-cells are either lacking or ineffective. Diabetes is a disease of the pancreatic islet cells wherein those affected lack adequate levels of insulin and have difficulty controlling their blood sugar. One alternative to self-administration of medicine and insulin is islet transplantation. The procedure involves an infusion of isolated donor islets into the patient. If the donor cells are accepted, these islets will function to regulate blood glucose levels through the production of insulin. Islet transplantation is therefore a treatment strategy that allows diabetics to reduce or eliminate the need for insulin injections to control their disease.

[0090] Cellular adhesion is important to cell survival, and how well cells adhere to and grow inside an implant depends on both the physical and chemical properties of the implant, particularly the surface of the implant. Islet cells in particular show greater survival when they are cultured in extracellular matrix proteins — fibronectin, collagen IV, or laminin. Collagen IV is an abundant material, but may not be suitable for use with certain embodiments of the present disclosure because it diminishes glucose-induced insulin responses.

[0091] Alginate use is known in tissue engineering, including clinical products using alginates and Phase II clinical trials involving alginate microcapsules supporting islet cells. The use of such alginates is contemplated in applications, methods and devices of the present disclosure. Accordingly, alginate is contemplated for use with certain embodiments of the disclosure. In some embodiments, alginate is grafted with bioactive peptides such as the RGD sequence (Arg- Gly-Asp) found in ECM proteins, and cell adhesion is thereby promoted.

[0092] In various embodiments, a stiff alginate-polyacrylamide shell contains a chemical mechanism to diffuse oxygen to the cells in the hollow core. It is also contemplated that a partially polymerized alginate+RGD is mixed with the cells, which also contains the same oxygenation mechanism, thus allowing oxygen to be supplied directly next to the cells and ensuring a higher concentration than from the alginate-polyacrylamide shell alone. The oxygenation mechanism involves the following reaction:

[0093] 2Ca02+2H₂0 0 +2Ca(0H)2 [0094] To mitigate the expected production of H2O2 from a competing reaction that takes place at physiological pH, catalase, which generates O2 from H2O2, accompanies the oxygenation mechanism in both the alginate-polyacrylamide shell as well as when added with cells in the hollow core. CaCh maintains its oxygen-releasing capacity over a period of days to weeks due to its low solubility, but generation of insoluble products of CaCh and increasing alkalinity of the surrounding solution have been problematic for cell survival. To neutralize the resulting alkalinity, the alginate is crosslinked with Al³⁺, the most optimal known crosslinking ion in terms of allowing high oxygen-releasing efficiency, slow release kinetics, and good pH buffer capacity. The H₃0⁺ generation through the hydrolysis of the released trivalent cations effectively neutralizes the pH increase caused by the oxygen-releasing process, yielding a neutral species (a hydrated metal hydroxide). The target quantity of CaCh necessary to ensure adequate initial oxygenation (up to 1 week) for islet cells is estimated at 5% (w/v) with the following rationale.

It has been shown that rapid decomposition of a 0.2% (w/v) slurry of CaCh at pH 7; at this pH, H2O2 was produced more rapidly and at higher quantities than 02. A 2% (w/v) mixture has been shown to yield adequate oxygenation duration within alginate beads, at least in the absence of cells. For example, up to 10 days of O2 release has been demonstrated from 1, 5, and 10% concentrations of CaCh for 3T3 fibroblasts. The greatest cell growth occurred with the 5 wt % concentration.

[0095] Alginates with a G-content of 50% or above are recognized as not eliciting an immune response. In contrast, high-M alginates (70-80%) have been shown to stimulate immune cells in mice. This may be due to the presence of poly cations in these studies involving high-M alginates, which by themselves stimulate the complement cascade and provoke an inflammatory reaction. It has been shown that beads made of different alginates, including high-M and high-G alginates with high molecular weight, performed similarly with a low degree of fibrosis when implanted subcutaneously in Wistar rats. High-M alginates may be preferred for implantation of pancreatic islets due to observed increased angiogenesis. However, this increased angiogenesis may be due to the smaller pore size of the high-M alginate creating an immune barrier to large molecules such as IgG (150 kDa), allowing more angiogenesis to proceed undisturbed. In various embodiments of the present disclosure, the use of high-G alginates is provided to reduce the immune response. High-G alginates have the additional advantage of not complexing as well with poly cations compared to high-M alginates, reducing the chance of immune response by that route.

[0096] Methods of Treatment

[0097] The removable scaffolds for subcutaneous implantation described herein are useful for inducing formation of microvasculature, avoiding local atrophy of the subcutaneous muscle layer at the implantation site, stimulating formation of an environment rich in blood vessels and extracellular matrices (e.g., supporting collagen matrix) to nourish and support subcutaneously transplanted islet cells, and/or for treating a metabolic disorder (e.g., type 1 diabetes) in a subject in need thereof.

[0098] The high incidence of therapeutic failure in the treatment of diabetes is a major contributor to the high rate of long-term hyperglycemia-associated complications or chronic damages (including microvascular complications such as diabetic nephropathy, retinopathy or neuropathy, and macrovascular complications such as coronary heart disease, cerebrovascular disease, and peripheral vascular disease) in patients with type 1 diabetes. Therefore, there is an unmet medical need for methods and devices with a good efficacy with regard to glycemic control, with regard to disease-modifying properties and with regard to reduction of co morbidity and mortality while at the same time showing an improved safety profile.

[0099] Provided herein is a method of transplanting a pancreatic islet cell population into a patient in need thereof, comprising: subcutaneously placing a removable scaffold comprising nano-sized features on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing the pancreatic islet cell population into the subcutaneous cavity.

[0100] In an aspect, provided herein is a method of transplanting a pancreatic islet cell population into a patient in need thereof, comprising: subcutaneously placing a removable scaffold comprising a biocompatible, hydrophilic polymer material at least on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing the pancreatic islet cell population into the subcutaneous cavity.

[0101] In an aspect, provided herein is a method of transplanting a pancreatic islet cell population into a patient in need thereof, comprising: subcutaneously placing a removable scaffold comprising nano-sized features formed by a biocompatible, hydrophilic polymer material on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing the pancreatic islet cell population into the subcutaneous cavity. [0102] In an aspect, provided herein is a method of treating type 1 diabetes in a mammal, comprising: subcutaneously placing a removable scaffold comprising nano-sized features on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing a donor pancreatic islet cell population into the subcutaneous cavity, wherein the donor pancreatic islet cell population is supported by the microvasculature in or around the subcutaneous cavity to maintain survival and function of islet cells.

[0103] In an aspect, provided herein is a method of treating type 1 diabetes in a mammal, comprising: subcutaneously placing a removable scaffold comprising a biocompatible, hydrophilic polymer material at least on its exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing a donor pancreatic islet cell population into the subcutaneous cavity, wherein the donor pancreatic islet cell population is supported by the microvasculature in or around the subcutaneous cavity to maintain survival and function of islet cells.

[0104] In an aspect, provided herein is a method of treating type 1 diabetes in a mammal, comprising: subcutaneously placing a removable scaffold comprising nano-sized features formed by a biocompatible, hydrophilic polymer material on its exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing a donor pancreatic islet cell population into the subcutaneous cavity, wherein the donor pancreatic islet cell population is supported by the microvasculature in or around the subcutaneous cavity to maintain survival and function of islet cells.

[0105] In some embodiments, the function of the islet cells is insulin and/or glucagon secretion levels. In some embodiments, the mammal recovers to normal glycemic. In some embodiments, the mean area under the curve (AUC) blood glucose is 2289 ± 107 mmol/L/120 min.

[0106] In some embodiments, the biocompatible, hydrophilic polymer material is a block co polymer. In some embodiments, the biocompatible, hydrophilic polymer material is poly (lactic- co-gly colic acid) (PLGA). In some embodiments, the lactide/glycolide molar ratio of the PLGA is about 75:25. In some embodiments, the inherent viscosity of the PLGA is about O.ndL-¹. [0107] In some embodiments, the scaffold has hierarchical pore architecture.

[0108] In some embodiments, the outer diameter of the scaffold is up to about 3.0 mm. In some embodiments, the inner diameter of the scaffold is up to about 2.0 mm.

[0109] In some embodiments, the scaffold has a length of about 2 cm.

[0110] In some embodiments, the scaffold has a nano-fiber morphology.

[0111] In some embodiments, the polymer is biodegradable. In some embodiments, the scaffold comprises a catheter.

[0112] In some embodiments, the scaffold does not trigger local atrophy of the subcutaneous muscle layer at the implantation site. The disclosure will be further understood by the following non-limiting examples.

EXAMPLES

[0113] The examples set forth below are provided to give those of ordinary skill in the art with a complete disclosure and description of how to make and use the claimed embodiments, and are not intended to limit the scope of what is disclosed herein. Modifications that are obvious to persons of skill in the art are intended to be within the scope of the following claims.

[0114] Example 1: Creation and analysis of the subcutaneous pre-vascularized DL space [0115] The PLGA nano-fiber catheter with hierarchical pore architecture was prepared by electro-spinning. Scanning electron microscopy (SEM) shows a well-distributed nano-fiber structure of PLGA catheter with outer diameter of - 2.5 mm (FIGS. 7A & 8A). The obtained PLGA nanofiber catheter possesses a hydrophilic surface characteristic (FIG. 7E). Compared to nylon catheter with an inconspicuous micro-patterned surface topography, the nano-fiber morphology of the outer surface of the PLGA catheter is more steric and flexible (FIG. 7A-7B). The effect of catheters based on different materials on the subcutaneous micro-vascular collagen space (shown in FIGS. 9A-9F) was analyzed. The PLGA nano-fiber catheters quickly induce subcutaneous DL space rich in micro-vessels and moderate collagen matrix thickness (FIGS. 9A and 9D). In contrast, nylon tube-induced subcutaneous vascular DL space required about 4 or 6 weeks while silicone tube need for 6 - 8 weeks. The subcutaneous DL space induced by nylon tube has the thinnest collagen matrix and high vascular density, but the length of time required for subcutaneous implantation leads to different degrees of atrophy of the subcutaneous muscle layer (FIGS. 9C and 9F). Although a silicone tube can also induce abundant subcutaneous DL space, the collagen matrix in DL space is uneven (FIGS. 9B and 9E). The subcutaneous DL space induced by PLGA nanofiber catheters provides an optimal environment for the survival and migration of islet cells where islet cells can secrete insulin and glucagon normally by day 2 after transplantation (FIGS. 2C-2D). This suggests that the subcutaneous DL space induced by PLGA nanofibers is an environment with a stable blood supply and collagen matrix, which can meet the survival needs of islet cells. FIGS. 9A-9H show a histological analysis of the DL site before islet cell transplantation. (9A-9C) Masson’s tri chrome staining of the cross-section of the DL site after removal of the PLGA nano-fiber, Nylon and Silicone catheter. Islets were infused into the resulting DL (*). Creation of a PLGA-based DL space requires 2 weeks, while a nylon- or silicone-based DL space requires 4 weeks. Collagen (blue), smooth muscle and erythrocytes (red) at 4x magnification. (9D-9F) fluorescent staining of the same cross-section stained for blood vessels (green) and nuclei (blue) at 4 x magnification.

[0116] To further confirm that the DL space induced by PLGA nano-fiber catheter in mice can ensure the normal insulin and glucagon secretion function of islet cells, glycemic control over time was monitored, and intraperitoneal glucose tolerance tests (IPGTT) were conducted at 60 days (FIGS. 11 and 12A-12B). In the positive kidney capsule (KC) group, by 14 days, 90.8 % of the mice became euglycemic and maintained > 60 days (FIG. 11). In the PLGA-DL group, 56 % of the mice became normal glycemic by 14 days, and by day 54, 90.5 % of the mice remained normal glycemic, similar to the positive KC group. In contrast, in the nylon-DL group, 26 % of the mice became normal glycemic within 16 days, and 58 % were normal glycemic by 60 days. Conversely, no mice showed a reversal of diabetes in the control group using unmodified subcutaneous transplantation (Sub-Q). IPGTT showed that diabetic mice in KC (n=10) and PLGA DL (n=28) groups recovered rapidly to normal glycemic (FIGS. 12A-12B). There was no difference as measured by the mean area under the curve (AUC) ± s.e.m. (AUC KC: 2101 ± 179 mmol/L 120 min vs. PLGA nanofiber based DL: 2289 ± 107 mmol/L/120 min, p > 0.05, ANOVA, FIG. 12B). Nylon-DL mice (n=18) were less tolerant to glucose than PLGA-DL mice (AUC Nylon based DL: 2985 ± 60 mmol/L/120 min, compared to PLGA based DL, p < 0.01, ANOVA, FIG. 12B), and all mice in the unmodified subcutaneous group had a diabetes spectrum (AUC Sub-Q 3431 ± 100 mmol/L/120 min, compared with PLGA based DL, p < 0.01, ANOVA, FIG. 12B). These results suggest that the subcutaneous DL space induced by the PLGA catheter supports the normal survival and functional realization of isogenic islet cells. [0117] Example 2: Long term efficacy and vascularization of DL islet cells grafts [0118] PLGA non-fiber scaffolds exhibit excellent subcutaneous collagen matrix and vascular induction properties, which may be related to the appropriate immune response of host caused by the chemical composition and surface properties of PLGA nanofibers scaffolds. Cytokine expression in subcutaneous tissues of PLGA nano-fiber catheters, nylon catheters, and unmodified subcutaneous B ALB/c mice was compared at various time points after implantation (FIGS. 3A-3R & 10A-10C). Both PLGA nano-fiber tubes and nylon tubes induce strong interleukin (IL) IL-Ib, IL-10 and keratinocyte growth factor (KC/GRO) responses, but the reactions to PLGA nano-fiber catheter were much faster (24 h versus 1 week). In both groups, IL-6 expression increased within 24 h, and remained slightly elevated during the 2 week experiment. In contrast, tumor necrosis factor alpha (TNF-a) expression was elevated in both groups 1 week after implantation. Interferon (IFN)-y was analyzed but not detected in any samples. These data indicate that PLGA nanofiber catheters can rapidly induce subcutaneously transient strong cytokine and chemokine responses that contribute to host inflammatory cell recruitment (e.g., neutrophils, macrophages, and fibroblasts) and new blood vessels formation. This suggests that a time-limited foreign body response induces a favorable location for transforming the subcutaneous space into islet cell transplantation.

[0119] To evaluate the long-term efficacy of subcutaneous DL space, about 80 islets were transplanted from syngeneic mice into subcutaneous DL space (or under the KC, or in the Sub-Q space) of BALB/C mice with STZ diabetes mellitus. Furthermore, about 1x105 cynomolgus monkey islet cells were engrafted into the DL space of diabetic, immune-deficient Rag-/- mice to verify the biocompatibility of DL method with preclinical grade human-like islets.

[0120] Allogeneic islet cells transplanted under the KC reversed diabetes in 90.5 % of recipients (FIG. 4A) within 7 ± 2.3 days (FIG. 4B). Islet cells grafts in the DL space reversed diabetes in 90.5 % of mice (FIG. 4A), with a significant improvement compared to the Sub-Q group (p < 0.001). Compared to KC engraftment, there was a slight delay in the engraftment of DL space, and the mean diabetes reversal after engraftment was at 25.8 ± 1.5 days (p > 0.05, Student’s t- test, FIG. 4B). The proportion of animals that achieved euglycemia was similar in kidney capsule (KC) recipients (n = 10) and DL site recipients (n = 28) 100 days after transplant, with KC recipients reversing diabetes earlier (p = 0.001, log-rank, Mantel-cox test). Non-fasting blood glucose measurements showed that both KC and DL site recipients maintained normoglycemia until the graft was retrieved (arrow), at which point they reverted to their pretransplant hyperglycemic state. Islets transplanted in the unmodified subcutaneous space (Sub-Q, n = 10) did not provide glycemic control.

[0121] To further confirm the long-term function of DL grafts, the IPGTT tests were performed at 100 days after transplantation. Both the DL and KC groups had well-preserved glucose clearance characteristics; there was no significant difference (FIG. 5A). FIG. 5B shows that the AUCs ± s.e.m. of the two groups is similar for glucose clearance (DL: 2181 ± 207 mmol/L/120 min versus KC: 1996 ± 321 mmol/L/120 min, p > 0.05, ANOVA). By contrast, glucose profiles in the Sub-Q group were significantly worse (AUC 3578 ± 89 mmol/L/120 min, p < 0.001, ANOVA) (FIG. 5B). Normal, non-diabetic BALB/c mice had the best glycemic profiles (AUC naive: 1423 ± 135 mmol/L/120 min, versus DL recipients, p < 0.01, ANOVA) (FIG. 5B). Furthermore, FIG. 6A shows that the blood glucose profiles of Rag-/- diabetic mice receiving cynomolgus monkey islet cells in the DL site are similar to those of BALB/c mice receiving homologous islet cells. To verify that graft dependent blood glucose normal, the grafts were retrieved and it was observed that diabetes was quickly restored in all cases (FIGS. 4B and 6A). [0122] In 100 days after transplantation into the DL space, the islet cells in the PLGA based DL space exhibited excellent survival status. Histological analysis of DL grafts site revealed that islet cells were enveloped in a space rich in microvasculature and collagen matrix between muscle and skin tissue (FIGS. 2B-2G & 6B-6G). A broad network of blood vessels can be seen at a macroscopic level and penetrate the islet bundle produced by the PLGA nano-fiber catheter (FIG. 2D). It is worth noting that the capillary network is limited to the DL region, whereas outside the edge of the tract, planes were relatively avascular. Grafts in DL space stained positive for insulin, glucagon and new islet micro-vascular endothelial cells (FIGS. 2G-2H, 2F & 6B-6F). In contrast, islet cells engrafted into the unmodified subcutaneous spaces experienced extensive necrosis and destructive inflammatory responses leading to graft failure (FIGS. 13A- 13C). To confirm that islet cell function in the DL site is dependent on vascular nourishment, the vascular density of DL and unmodified subcutaneous graft sites were compared at 100 days after transplantation (FIGS. 14A-14C). The DL graft site demonstrated a significant increase in neovascularization as measured by the percentage of graft-positive staining of von Willebrand (vWF) ± s.e.m. (2.57 ± 0.77 % of the entire graft vWF+ in DL grafts versus 0.86 ± 0.48 % in Sub-Q groups, p < 0.001, Student’s t-test, FIG. 14A).

[0123] Example 3: Testing of the efficacy of DL islet cell transplantation technology in other mouse models

[0124] To verify that pre-vascularized DL islet cell grafts can treat not only BALB/c mice with STZ diabetes (normally is type I diabetes), whether it can treat C57BL/6 mice with STZ diabetes, which, unlike BALB/c mice, have a strong foreign body reaction, was also studied. After transplanting the same number of syngeneic islet cells in the DL space of type I diabetic mice, C57BL / 6 mice reversed diabetes earlier than in BALB / c mice, as calculated by mean days after transplantation ± s.e.m. (12.5 ± 4.2 days versus 25.8 ± 1.7 days, p < 0.05, Student's t- test) (FIG. 15). On the 50th day after transplantation, the proportion of diabetes reversal in the two experimental animal models was very similar (C57BL/6: 72 % (8/11) and BALB/c: 66 % (15/28), p > 0.05, Student's t-test). Since diabetes may affect wound healing, the use of PLGA nanofiber catheters to create a DL transplant space subcutaneously in diabetic mice was investigated and compared to islet cell transplantation in DL space of similar mice without diabetes. All mice were maintained for 2 weeks prior to catheter withdrawal and transplantation of isogenic islets in DL space. Pre-diabetes did not affect diabetes reversal because similar rates were observed in the two groups on day 50 (70 % (5/8) pre-DL diabetes versus 54 % (12/23) post-DL diabetes; p > 0.05, Student's t-test; FIG. 16). In order to confirm whether the DL transplantation technique is effective in a homologous immune barrier, around 50 BALB/c islet cells were transplanted into the DL site of the C57BL/6 recipients that pre-DL diabetes. Rejection occurred in mice that did not receive immunosuppressive therapy within 9 days, whereas allografts in the DL space of mice treated with tacrolimus (0.5 mg/kg, 28 days) survived longer time (FIG. 17).

[0125] Example 4: Preparation of PLGA nanofiber catheter

[0126] Materials

[0127] Poly (lactic-co-gly colic acid) (PLGA, with a lactide/glycolide molar ratio of 75:25 and an inherent viscosity of 0.17dL-l, 15.9-41.6 kDa, meilunbio®, Dalian, China) hexafluoroisopropanol (HFIP) was AR grade, purchased from Aladdin® (Shanghai, China) and used as received. Dulbecco minimum essential medium (DMEM), fetal bovine serum (FBS), penicillin-streptomycin, 0.25 % trypsin-0.02 % ethylenediaminetetraacetic acid (EDTA), 1 ^c PBS buffer with pH 7.4 (ultrapure grade) were purchased from Gibco (Thermo Fisher Scientific, Waltham, MA, USA). All other reagents were commercially available and used without further purification unless otherwise noted.

[0128] PLGA nano-fibers with a diameter of about 1.8 mm were obtained by electrospinning. Briefly, 1 gram of transparent PLGA particles are weighed transferred into 25 ml beaker, 10 ml HFIP is added to beaker, magnetic rotor is added, and finally sealed with aluminum foil. PLGA particles are dissolved in 55 degree water bath at 100 rpm speed. After about 12 hours, a well- dissolved PLGA solution is obtained. The PLGA solution is then transferred to a 15 ml syringe. The syringe is mounted on an electrospinning machine and connected to a 22-gauge size needle (blunt type) with a needle-to-collector distance of 150 mm. The distance between the needle and the receiving device is adjusted to 15 cm. The transfusion volume is 10 kV (high pressure), the flow rate of the polymer solution was set at 0.40 mL/h using a syringe pump. The receiving device is a stainless steel tube with an outer diameter of about 1.8 cm. The PLGA nanofibers with 1.8 mm inner diameter and 2.3 mm outer diameter can be obtained by electrospinning in about 15-18 hours.

[0129] The morphology of the prepared nanofiber PLGA catheters was captured on a field- emitting scanning electron microscopy (SEM, Regulus 8100, Hitachi, Japan). The method was as follows: the cross section of PLGA nanofibers with full morphology was fractured by liquid nitrogen, then adhered to conductive adhesives, sprayed gold, and placed on scanning electron microscopy.

[0130] Example 5: Creation of the pre-vascularized, device-less (DL), extracellular matrix-rich subcutaneous transplantation space [0131] Two weeks before islet transplantation, PLGA (2 cm long, 2.3 mm in diameter) nanofiber catheter approved by FDA was used to create a subcutaneous transplantation site with rich vascularization, suitable collagen thickness and no side effects such as surrounding tissue atrophy. The control group was treated with 6F Nylon radiopaque angiographic catheter (Torcon NB, Advantage catheter, Bloomington, American), and 2.2 mm diameter medical Silicone tube (Tianpinghuachang Medical Devices Co. Ltd., Suzhou, China).

[0132] Method:

[0133] Male Balb/c, C57BL/6, or C57BL/6N-Ragltmlcyagen immune-deficient mice (Saiye, Suzhou, China) were weighed. After inhalation anesthesia with isoflurane, the mice were supine on the operating board. The hair of each mouse's abdominal cavity was removed by shaving machine. The skin of the whole abdominal cavity was sterilized with 70% ethanol and iodophor. Then a 4 cm transverse incision was cut on the left lower side of the abdominal cavity with sterile surgical scissors. A 1 cm by 3 cm incision was made with blunt tweezers in the subcutaneous incision. The PLGA nanofiber catheter is then implanted into the space, parallel to the midline of the abdomen. The incision was sealed with surgical glue (Histoacryl, BiostatB, Melsungen, Germany) (FIG. 8B). After PLGA nanofibers were implanted into the catheter, the nanofibers on the outer surface of the catheter interacted with the subcutaneous hemoglobin of the host, forming a dense pre-vascularized subcutaneous tissue site with the smallest outline (FIGS. 8C-8D). During transplantation, the removal catheter was provided with a pre- vascularized, properly thick collagen layer and no device space, allowing islet or islet cell implantation (FIG. 1 and FIG. 2A).

[0134] Example 6: Cytokines and chemokines assay

[0135] At 24 hours, 1 week, and 2 weeks after catheter implantation, a hollow cavity surrounded by a pre-vascularized extracellular matrix was removed from the left subcutaneous lower side of the abdominal cavity where any source of catheter material had been implanted. The cavity tissue was peeled off and quickly placed in a pre-selected weighing micro centrifugal tube, marking samples and time points. The weight of tissue samples was recorded before detailed factor and chemokine tests. The samples were then rapidly frozen with liquid nitrogen and stored at -80 °C. After collecting enough tissue samples for each implantation period, 1 ml solution buffer (0.15 mNaCl, 1 mM Tris HC1, 0.1% SDS, 0.1% Triton X-100, 20 mM sodium deoxycholate, 5 mM EDTA) was added to every 200 mg tissue sample. Each tissue sample was homogenized on ice for 30 s x2 using a homogenizer (scientz-950, Shanghai Hai, China). Collected supernatant of each group, cell debris was removed and supernatant was collected by centrifugation at a speed of 14000 rpm for 10 minutes at 4 °C. The supernatant of cytokine and chemokine (Interleukin-ΐb (IL-Ib), IL-12p70, interferon-g (IFN-g), IL-6, keratinocyte growth factor (KC/GRO), IL-10 and tumor necrosis factor-a (TNF-a)) in each group were measured using a multi-factor mouse proinflammatory Biolegend kit (LEGENDplexTM, San Diego, CA, USA) requiring 25 pi of lysate/replicate and analyzed on a flow cytometry (FAC Scalibur, New Jersey, American). LEGENDplex (LEGENDplex, San Diego, CA, USA) imaging analysis software is used for data output.

[0136] Establishment of type I diabetic mice model

[0137] STZ intraperitoneal injection method was used to establish type I diabetic mice. Typically, mice were fasting for 12 hours before modeling, fasting blood glucose and body weight were measured. Then STZ-acetate phosphate buffer was injected intraperitoneally, 185 mg/kg, pH=4.5 (Sigma-Aldrich China Co., Shanghai, China). After 5 days, blood sugar concentration was measured for 2 consecutive days, which exceeded 15 mmol/L (350 mg/dl). [0138] Isolation and purification of mouse islets

[0139] Islets were isolated from the pancreas of healthy male mice aged 12 weeks. After the mice were euthanized, the middle incision of the upper abdomen was made into the abdomen, the common bile duct was clamped, and 0.5 mg/mL collagenase V was injected from the common bile duct. The pancreas was cut off rapidly while the pancreas was completely swollen. Islets were collected through 400 mesh screen (BD, Lake Franklin, New Jersey, USA) and washed with 4 degree Hank's solution repeatedly for 4 minutes. The suspension was transferred to 10 ml ice-bath centrifuge tube. The suspension was centrifuged for 3 minutes at 600 rpm, then the deposit discarded. The supernatant was suspended and centrifuged for 5 minutes at 2000 imp to collect islet cells.

[0140] Islet cell isolation of cynomolgus monkeys

[0141] After the euthanization of the cynomolgus monkey (Guangdong Chunsheng Bio- Biotechnology Development Co., Ltd., Guangzhou, China), the pancreas was separated from the body through the mid-upper abdominal incision, clamping the common bile duct. The pancreas was fully perfused with cold saline containing 2% penicillin-streptomycin and then injected with 1 mg/mL collagenase V solution through the main pancreatic duct and digested by a single-cell processor (gentle MACS, Miltenyibiotec, Cologne, German) at 37 °C. When more than 50% of the free islets were observed in the sample under a microscope, and about 200 microns of the free islets were observed, the digestion was discontinued. Then islet cells were purified by 400 mesh cell sieve. These studies were approved by the Health Research Ethics Committee of Guangdong Chunsheng Biotechnology Development Co., Ltd. Islet cells of cynomolgus monkeys were cultured overnight at 22 °C in a medium supplemented with insulin-selenium transferrin and insulin growth factor. The formula of culture medium was: DMEM/F12: DMEM (1:1) contained 1% penicillin-streptomycin, 10% FBS, 5 ng/mL insulin, 5.5 mg/mL transferrin and 5 pg/mL selenium.

[0142] Islet transplantation

[0143] A diabetic mouse received 2.5 healthy donor islets for islet transplantation. The group of islet transplantation was divided into PLGA group, nylon tube group, and silica gel tube group. The positive control group was renal capsule transplantation group and the negative control group was subcutaneous non-prevascularized DL site group. After inhalation of anesthesia with isoflurane, mice were supine on the operating board, wiping the abdominal surface of the implanted catheter with soap, povidone (Guangzhou Pharmaceutical Co., Ltd., Guangzhou, China) and ethanol. A small incision was made in the upper abdomen to remove the PLGA, nylon, or silica gel tubes that had been previously implanted (FIGS. 1 and 8E). Pancreatic islets were transplanted into pre-fabricated pre-vascularized spaces by connecting PE-20 hoses (BD, Franklin Lake, New Jersey, USA) with syringe heads (FIGS. 1 and 8F). The incision was then closed with surgical suture glue (Histoacryl, Biostat B, Melsungen, Germany) (FIG. 8G).

[0144] FIGS. 8A-8H show an overview of the subcutaneous, pre-vascularized device-less (DL) site transplant approach. To create the pre-vascularized the DL transplant site, a 1.5 mm outer diameter nano-fiber textured PLGA catheter is: (8A) implanted beneath the skin; (8B-8D) left for a period of 2 weeks; (8E) removed; (8F) subsequent to the implant period, the PLGA nano- fiber catheter is removed (8E) creating a vascularized lumen where the islet transplant is infused; (8F) the islets are then infused via PE50 tubing (BD, Lake Franklin, New Jersey); (8G) the incision site closed with tissue suture glue (Histoacryl, Biostat B, Melsungen, Germany); and (8H) the islet graft exhibited no visible profde up to 100 days post-transplant.

[0145] Method of renal capsule transplantation

[0146] After inhalation of anesthesia with isoflurane, the mice lay on the operating board, the defect of the left back was removed and the operating field sterilized with ethanol, the skin and muscle layer under the left costal margin was cut, the left kidney was squeezed out of the upper part with sterile cohon swab, and the capsule was slightly punctured with a needle tip in the middle of the back of the kidney to form a small hole, which was left under the capsule. A 1 ml syringe containing islets was used to penetrate its lengthened suction head through the capsule rupture to the middle and lower capsule of the kidney, and the islets transplanted to the capsule with PE-20 catheter; the catheter head was carefully pulled out, the hemostasis was pressed with cohon swabs and the wound sutured layer by layer; after operation, aureomycin eye ointment was applied to the wound, and subcutaneous fluid replacement 1 ml. Saline water. Negative control group: islet cells were subcutaneously injected into diabetic mice with a 1 ml syringe containing islets. [0147] Functional assessment

[0148] After islet transplantation, all mice were subcutaneously injected with 100 ml cefazolin sodium (Guangzhou Pharmaceutical Co., Ltd., Guangzhou, China) every 12 hours for 5 consecutive days. Blood glucose was measured with a portable blood glucose meter (One Touch Ultra Easy, Johnson & Johnson, New Jersey, USA) every 12 hours after two days implantation, and then once every three days. Glucose tolerance test was performed 60 or 100 days after operation to determine whether there was abnormal glucose metabolism in islet recipients. The method was as follows: After fasting overnight, the mice were sterilized with a disposable sterile injector through a 0.22 micron filter, and then gavaged at a dose of 2.0 mg/g. Blood sugar levels were monitored at 0, 15, 30, 60, 90 and 120 minutes after gavage to calculate and analyze AUC blood sugar between transplantation groups.

[0149] Graft retrieve

[0150] STZ-diabetic mice are irreversible diabetic models, in order to confirm that the normal blood sugar of all islet recipients is islet graft-dependent. Animals with functional islet grafts were be examined by nephrectomy or subcutaneous graft excision. In the subcutaneous pre vascularization group, after isopentane anesthesia, the left abdomen was shaved. After ethanol disinfection, the skin and pre-vascularized islet graft sites of the transplantation site were removed by surgical scissors. Renal capsule transplantation group: After isoflurane anesthesia, the left kidney was exposed. The left kidney was occluded with LT200 ligation clip (Johnson & Johnson, Inc., Ville St Laurent, QC, CA), and then the left kidney was removed. After islet graft resection, non-free blood glucose was measured within 7 days, and hyperglycemia was observed to confirm whether the normal blood glucose of all islet recipients depended on islet graft.

[0151] Histological assessment

[0152] All the above-mentioned islet grafts were removed from the body, fixed overnight in 4% polyformaldehyde (Aladdin®, Shanghai, China), washed with flowing tap water for 5 minutes, dehydrated by gradient dehydration with ethanol, transparent xylene, embedded in paraffin (Sigma- Aldrich, Shanghai, China), cut into 4 micron paraffin sections, and then stained with hematoxylin/eosin (HE, Sigma-Aldrich, Shanghai, China) and Masson's trichrome staining (Sigma- Aldrich, Shanghai, China), respectively. In order to detect the expression of vascular endothelial cell factor, insulin and glucagon in the samples, immunofluorescence and laser confocal microscopy were used for analysis. Each tissue slice was dewaxing and antigen repaired, then 0.5% TritonX-100 (Servicebio, Beijing, China) in PBS was permeable for 5 minutes, and then contained 5 % bovine serum albumin (BSA, Sigma-Aldrich, Shanghai, China) in PBS solution for 30 minutes. The specimens were stained with primary antibody of insulin antibody (710289, Thermo Fisher, Waltham, MA, USA) and Rabbit anti porcine vascular endothelial cell eighth factor antibody (53-9743-80, Thermo Fisher, Waltham, MA, USA) or rabbit anti-glucagon antibodies (abl33195, Abeam, shanghai, China) at a dilution of 1:200, respectively, overnight at 4 °C. After washing with PBS solution containing 1% BSA, the secondary antibody treatment was performed using goat anti-guinea pig Ig (H+L) antibodies (ab6906, abeam, shanghai, China) and 1:400 goat anti-mouse Ig (H+L) antibodies (A28175, Thermo Fisher, Waltham, MA, USA) at a dilution of 1 :2000 at room temperature for 45 minutes. 4’,6-diamidino-2-phenylindole (DAPI, 62248, Thermo Fisher, Waltham, MA, USA) was used to stain the nucleus. At last, PBS solution was used to wash three sections. After sealing the tablets, confocal laser scanning microscopy (CLSM, SP5, Leica, Wetzlar, German) was performed. Vascular density was quantitatively analyzed by ImageJ software (ImageJ, National Institutes of Health, Bethesda MD).

[0153] Statistical analysis

[0154] The results of all quantitative analysis are expressed as the mean ± standard deviation (SD), and tested by one-way ANOVA parameters using GraphPad Prism (GraphPad Software, La Jolla, California, USA). Newman-Keuls post-hoc tests were employed to compare the difference between the research groups. *p <0.05 was considered to have statistical significant. [0155] The PLGA nanofibers were cut into 2 cm length nanofiber catheters and sterilized with 12 kGy Co60 irradiation.

[0156] Intrahepatic, intrarenal or intrapleural islet cell transplantation is a relatively effective method for clinically curing type I diabetes. However, permanent encapsulation devices are often required to carry islet cells to specific sites within the organs, and these devices typically produce avascular fibrotic granules and chronic inflammatory reactions that result in graft failure. As disclosed herein, the use of biodegradable PLGA nanofiber catheter biomaterials can rapidly generate microvascular-rich subcutaneous DL graft sites suitable for islet cell growth, which avoids the need for a permanent cellular packaging device. A stronger early inflammatory response is conducive to the rapid formation of new blood vessels. Compared to a nylon catheter that takes about weeks or months to create a pre-vascularized subcutaneous DL graft site, the PLGA nanofiber catheter can produce subcutaneous DL space rich in blood vessels and extracellular matrix in 2 weeks. It was found that pre-vascularization subcutaneous DL sites based on PLGA nanofibers can successfully engraft islet cells in different strains of mice. Monkey islet cells transplanted into immune-deficient Rag-/- mice reversed diabetes to a limited extent. This is due to the fact that Rag-/- mice maintain intact innate immunity and also retain the neo-vascular response of foreign bodies. All cases were demonstrated to have recovered rapidly to the diabetic state after removal of the subcutaneous islet cell implants, indicating that blood glucose normal was dependent on graft function. [0157] To find conditions that yield favorable DL sites, the inflammatory responses of PLGA nanofiber catheters and nylon tubes were compared with different chemical compounds and surface properties and tested pro-inflammatory factors in tissues at different time points during the implantation period. It was found that PLGA catheters with hierarchical nanofiber surface topography induced faster and stronger pro-inflammatory responses than nylon tubes, which provided good conditions for more effective diabetes reversal. Since the nylon tube takes 4 weeks or more to induce the intensity of inflammation of new blood vessel formation, this may cause local atrophy of the implant site or trigger local chronic inflammation of the host. The optimal time for retention of PLGA nanofiber catheters in this study was slightly different between species. At 24 hours, 1 week and 2 weeks after catheter implantation, pro-inflammatory markers in tissues between before and after islet cell transplantation were tested. The study showed that a week after PLGA nanofiber catheter implantation resulted in a significant local elevation of a series of pro-inflammatory cytokines. At 2 weeks after implantation, no catheter adhesion, bleeding or significant tissue trauma occurred during the extraction of PLGA nanotubes. The advantage of the pre-vascularized subcutaneous DL site based on PLGA nanofiber catheter is that the block polymer PLGA is a biodegradable material, and the LA fragment in its chemical block structure is a lactic acid material, which can rapidly induce the inflammatory reaction of the local tissue of the host in a short time, while the GA fragment can inhibit inflammation. In contrast, nylon is a thermoplastic non-degradable resin containing repetitive amide group - [NHCO] - in the molecular backbone. The chemical structure of the resin is very stable and non-degradable, so it cannot participate in the induction of host inflammation. At the same time, due to the unobvious micro-texture of nylon tubes, PLGA catheters with relatively obvious nano-fiber microstructures could fast stimulating host immune recognition. Another advantage of biodegradable PLGA nanofiber catheters is that their degradable LA and GA fragments are small molecules that can be expelled rapidly by the host immune system. This is conducive to the rapid termination of immune recognition after neovascularization.

[0158] Although transplantation of mouse islet cells under the KC site can exert good efficacy in mice with type I diabetes, it generally does not achieve insulin independence in large animals or humans. This is because one diabetic patient needs the islets of two or more normal donors. In B ALB/c mice without strong foreign body reaction, the time to achieve diabetes reversal in PLGA nano-fiber catheter-based DL transplants is roughly similar to that of KC site, but in C57BL/6 mice with stronger foreign body reaction, the time to normoglycemia was very close to that in KC control. In contrast, the permanent implant device has traditionally failed in C57BL/6 mice, but it works well in alternative strains. [0159] It was also found that when immunosuppressants are used, the DL site supports allogeneic islet cell transplantation in mice. In addition, it was found that PLGA nanofiber catheters can produce ideal DL sites in diabetic mice, and that the DL islet cell graft does not interfere with the rate of diabetes reversal. It is not certain whether the neovascularization response in patients with long-term diabetes is similar to this study because one of the complications of end-stage diabetic patients is ischemia. Although it is predicted that the neovascularization response in patients with end-stage diabetes will not be severely limited, this remains to be confirmed by subsequent human studies.

[0160] While preferred embodiments of the present disclosure have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the disclosure. It should be understood that various alternatives to the embodiments of the disclosure described herein may be employed in practicing the disclosure. It is intended that the following claims define the scope of the disclosure and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. A method of transplanting a pancreatic islet cell population into a patient in need thereof, comprising: subcutaneously placing a removable scaffold comprising nano-sized features on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing the pancreatic islet cell population into the subcutaneous cavity.

2. A method of transplanting a pancreatic islet cell population into a patient in need thereof, comprising: subcutaneously placing a removable scaffold comprising a biocompatible, hydrophilic polymer material at least on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing the pancreatic islet cell population into the subcutaneous cavity.

3. A method of transplanting a pancreatic islet cell population into a patient in need thereof, comprising: subcutaneously placing a removable scaffold comprising nano-sized features formed by a biocompatible, hydrophilic polymer material on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing the pancreatic islet cell population into the subcutaneous cavity.

4. A method of treating type 1 diabetes in a mammal, comprising: subcutaneously placing a removable scaffold comprising nano-sized features on an exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing a donor pancreatic islet cell population into the subcutaneous cavity, wherein the donor pancreatic islet cell population is supported by the microvasculature in or around the subcutaneous cavity to maintain survival and function of islet cells.

5. The method of claim 4, wherein the function of the islet cells is insulin and/or glucagon secretion levels.

6. The method of claim 4 or 5, wherein the mammal recovers to normal glycemic.

7. The method of claim 6, wherein mean area under the curve (AUC) is 2289 ± 107 mmol/L/120 min.

8. A method of treating type 1 diabetes in a mammal, comprising: subcutaneously placing a removable scaffold comprising a biocompatible, hydrophilic polymer material at least on its exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing a donor pancreatic islet cell population into the subcutaneous cavity, wherein the donor pancreatic islet cell population is supported by the microvasculature in or around the subcutaneous cavity to maintain survival and function of islet cells.

9. The method of claim 8, wherein the function of the islet cells is insulin and/or glucagon secretion levels.

10. The method of claim 8 or 9, wherein the mammal recovers to normal glycemic.

11. The method of claim 10, wherein the mean area under the curve (AUC) blood glucose is 2289 ± 107 mmol/L/120 min.

12. A method of treating type 1 diabetes in a mammal, comprising: subcutaneously placing a removable scaffold comprising nano-sized features formed by a biocompatible, hydrophilic polymer material on its exterior surface to induce formation of microvasculature; removing the scaffold to form a subcutaneous cavity, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and placing a donor pancreatic islet cell population into the subcutaneous cavity, wherein the donor pancreatic islet cell population is supported by the microvasculature in or around the subcutaneous cavity to maintain survival and function of islet cells.

13. The method of claim 12, wherein the function of the islet cells is insulin and/or glucagon secretion levels.

14. The method of claim 12 or 13, wherein the mammal recovers to normal glycemic.

15. The method of claim 14, wherein the mean area under the curve (AUC) blood glucose is 2289 ± 107 mmol/L/120 min.

16. The method of any one of claims 1-15, wherein the scaffold does not trigger local atrophy of the subcutaneous muscle layer at the implantation site.

17. The method of any one of claims 2, 3, or 8-16, wherein the biocompatible, hydrophilic polymer material is poly (lactic-co-gly colic acid) (PLGA).

18. The method of claim 17, wherein the lactide/glycolide molar ratio of the PLGA is 75:25.

19. The method of claim 17 or 18, wherein the inherent viscosity of the PLGA is 0.17dL-l.

20. The method of any one of claims 1-19, wherein the scaffold has hierarchical pore architecture.

21. The method of any one of claims 1-20, wherein the outer diameter of the catheter is up to about 3.0 mm.

22. The method of any one of claims 1-21, wherein the inner diameter of the catheter is up to about 2.0 mm.

23. The method of any one of claims 1-22, wherein the scaffold has a length of about 2 cm.

24. The method of any one of claims 1-23, wherein the scaffold has a nano-fiber morphology.

25. The method of any one of claims 2, 3, 8-25, wherein the polymer is biodegradable.

26. A removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter has nano-sized features to induce formation of microvasculature such that when catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity.

27. The scaffold of claim 26, wherein the nano-sized features are made from a material comprising a biocompatible, hydrophilic polymer.

28. A removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity.

29. The scaffold of claim 28, wherein the biocompatible, hydrophilic polymer comprises nan- sized features.

30. A removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises nano-sized and a biocompatible, hydrophilic polymer material that induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity.

31. The scaffold of any one of claims 26-30, wherein the catheter does not trigger local atrophy of the subcutaneous muscle layer at the implantation site.

32. The scaffold of any one of claims 27-30, wherein the biocompatible, hydrophilic polymer material is poly (lactic-co-gly colic acid) (PLGA).

33. The scaffold of claim 32, wherein the lactide/glycolide molar ratio of the PLGA is 75:25.

34. The scaffold of claim 32 or 33, wherein the inherent viscosity of the PLGA is 0.17dL-l.

35. The scaffold of any one of claims 26-34, wherein the catheter has hierarchical pore architecture.

36. The scaffold of any one of claims 26-35, wherein the outer diameter of the catheter is up to about 3.0 mm.

37. The scaffold of any one of claims 26-36, wherein the inner diameter of the catheter is up to about 2.0 mm.

38. The scaffold of any one of claims 26-37, wherein the catheter has a length of about 2 cm.

39. The scaffold of any one of claims 26-38, wherein the catheter has a nano-fiber morphology.

40. The scaffold of any one of claims 27-30, wherein the polymer is biodegradable.

41. A kit, comprising: a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter has nano-sized features to induce formation of microvasculature such that when catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and an islet cell population in a pharmaceutically acceptable carrier.

42. A kit, comprising: a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and an islet cell population in a pharmaceutically acceptable carrier.

43. A kit, comprising: a removable scaffold for inducing formation of microvasculature, comprising: a catheter shaped and dimensioned for subcutaneous placement, wherein an exterior surface of the catheter comprises nano-sized and a biocompatible, hydrophilic polymer material to induce formation of microvasculature such that when the catheter is removed, a subcutaneous cavity is formed, wherein at least part of the microvasculature remains in or around the subcutaneous cavity; and an islet cell population in a pharmaceutically acceptable carrier.

44. The kit of any one of claims 41-43, wherein the catheter does not trigger local atrophy of the subcutaneous muscle layer at the implantation site.

45. The kit of claim 42 or 43, wherein the biocompatible, hydrophilic polymer material is Poly (lactic-co-gly colic acid) (PLGA).

46. The kit of claim 45, wherein the lactide/glycolide molar ratio of the PLGA is about 75:25.

47. The kit of claim 45 or 46, wherein the inherent viscosity of the PLGA is about 0. HdL-¹.

48. The kit of any one of claims 41-47, wherein the catheter has hierarchical pore architecture.

49. The kit of any one of claims 41-48, wherein the outer diameter of the catheter is up to about 3.0 mm.

50. The kit of any one of claims 41-49, wherein the inner diameter of the catheter is up to about 2.0 mm.

51. The kit of any one of claims 41-50, wherein the catheter has a length of about 2 cm.

52. The kit of any one of claims 41-51, wherein the catheter has a nano-fiber morphology.

53. The kit of any one of claims 42-47, wherein the polymer is biodegradable.