WO2015128826A1

WO2015128826A1 - Cell-protected implant

Info

Publication number: WO2015128826A1
Application number: PCT/IB2015/051427
Authority: WO
Inventors: Uriel Barkai; Itamar WEISMAN; Jacob ROMANO; Boaz Brill
Original assignee: Glusense Ltd.
Priority date: 2014-02-26
Filing date: 2015-02-26
Publication date: 2015-09-03

Abstract

Apparatus is provided, comprising (a) a tubular structure (912) comprising a circumferential wall (912) that (i) defines a lumen, and (ii) has a molecular weight cut-off of 10-100 kDa; (b) a hydrogel (920, 926), disposed within the lumen; (c) a plurality of producer cells (36), suspended within the hydrogel, the producer cells containing exogenous genetic material that encodes an extracellular molecule; and (d) a plurality of mesenchymal stem cells (26), suspended within the hydrogel. Other embodiments are also described.

Description

CELL-PROTECTED IMPLANT

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority from US Provisional Patent Application 61/944,936 to Barkai et al., filed February 26, 2014, and entitled "Cell-protected implant," which is incorporated herein by reference.

FIELD OF THE INVENTION

Some applications of the present invention relate in general to implantable devices. More specifically, some applications of the present invention relate to improving long- term functionality of implantable devices by modulating responses of the body to the device.

BACKGROUND

A challenge in maintaining cell-based implantable devices for extended periods of time in the body is overcoming the aggression of the host immune system. Two related immune responses that may be elicited against the implant include graft rejection and foreign body response (FBR). Graft rejection is a progressive set of reactions launched by host leukocytes aiming to destroy foreign tissue. FBR is the end-stage response of the inflammatory and wound healing responses following implantation of a medical device. Eventually both the graft and the surrounding tissue may be damaged and the device may finally be encapsulated in a dense fibrotic tissue. This may cause malfunction of the medical device, either by damaging the device or by fibrotic tissue isolating the device from the body, and thereby reducing electrical and/or chemical communication between the device and the body.

The following references are incorporated herein by reference:

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SUMMARY OF THE INVENTION

Applications of the invention relate to providing an implant comprising (1) a sensor, configured to detect a parameter of the subject in which the implant is implanted, (2) an interface surface, configured to provide a communication between the sensor and the body of the subject, and (3) a plurality of cells, immobilized with respect to the sensor and/or the interface surface, and configured to maintain functionality of the implant by modulating, at least locally, one or more cellular functions of the body of the subject, e.g., that may otherwise inhibit the functionality of the implant. More than one example of cell types that may be used for this "protector" function is provided herein, so for clarity, these cells are referred to herein as "protector cells."

For some applications, the protector cells are mesenchymal stem cells (MSC). For some applications, the protector cells are regulatory T cells (Treg). For some applications, the protector cells are dermal fibroblasts (DF). For some applications, the protector cells are fusion cells of MSC and another cell type, as described in more detail hereinbelow. For some applications, the protector cells are regulatory T cells.

Typically, at least part of the implant is covered with a selectively-permeable covering (e.g., a membrane). There is therefore provided, in accordance with an application of the present invention, apparatus including an implant, the implant including:

a structure including a wall that is shaped to define a cavity;

a plurality of producer cells, disposed within the cavity, the producer cells containing exogenous genetic material that encodes an extracellular molecule; and

a plurality of mesenchymal stem cells (MSC), immobilized with respect to the structure.

In an application, the MSC include MSC that have been derived from a human tissue selected from the group consisting of: bone marrow, placental blood, cord blood, Wharton's jelly, dental pulp and adipose tissue. In an application, the MSC have been selected based on a cell-surface presence of

CD73, CD90 and CD 105.

In an application, the MSC have been selected based on a cell- surface absence of (1) CD34; (2) CD45; (3) HLA-DR; (4) at least one marker selected from the group consisting of: CD 14 and CD l ib; and (5) at least one marker selected from the group consisting of: CD79alpha and CD19.

In an application, the MSC have been selected based on a cell-surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276.

In an application, the MSC have been selected based on a cell-surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD106, CD140b, CD271, MSCA-1, Stro-1, SSEA4 and CD146. In an application, the MSC have been selected based on a cell- surface absence of CD40, CD80 and CD86.

In an application, the MSC have low cell-surface levels of Major Histocompatibility Complex class I molecules and Major Histocompatibility Complex class II molecules.

In an application, the MSC are disposed on an outside of the structure.

In an application, the implant includes a hydrogel disposed within the cavity, and the producer cells are suspended within the hydrogel.

In an application, the implant includes a hydrogel, and the MSC are suspended within the hydrogel.

In an application, the hydrogel and the MSC are disposed within the cavity.

In an application, the hydrogel and the MSC are disposed on an outside of the structure.

In an application, the wall is selectively permeable and has a molecular weight cut- off of 10-100 kDa.

In an application, the wall is selectively permeable and has a molecular weight cutoff of 10-50 kDa.

In an application, the producer cells are disposed in a first compartment within the cavity, and the MSC are disposed in a second compartment within the cavity. In an application, the second compartment is disposed between the first compartment and the circumferential wall.

In an application, the second compartment circumscribes the first compartment.

In an application, the producer cells are interspersed with the MSC.

In an application, the structure is tubular, and the wall is a circumferential wall that circumscribes the cavity.

In an application, the structure is tubular, the wall is a circumferential wall that shapes the cavity as a lumen, and the lumen has a diameter of 0.5-1.5 mm.

In an application, the structure is tubular, the wall is a circumferential wall that shapes the cavity as a lumen, and the lumen has a diameter of up to 5 mm. In an application, the wall includes modified polyethersulfone.

In an application, the implant further includes a coating, disposed on an outer surface of the wall, and including platelet material.

In an application, the coating includes platelet-rich plasma. In an application, the coating includes platelet microparticles.

In an application, the coating is water-permeable.

In an application, the coating includes a hydrogel.

In an application, the coating includes polyethylene glycol.

In an application, the coating includes alginate. In an application, the coating has a thickness of 50-700 microns.

In an application, the coating has a thickness of 100-500 microns.

There is further provided, in accordance with an application of the present invention, a method, including:

providing a structure having a wall that is shaped to define a cavity;

introducing a cell suspension of mesenchymal stem cells (MSC) into the cavity; and

subsequently, setting the cell suspension by placing the structure in a setting solution.

In an application, introducing the cell suspension of MSC includes introducing a cell suspension of MSC that have been derived from a human tissue selected from the group consisting of: bone marrow, placental blood, cord blood, Wharton's jelly, dental pulp and adipose tissue.

In an application, introducing the cell suspension of MSC includes introducing a cell suspension of selected MSC that have been selected based on a cell-surface presence of CD73 , CD90 and CD 105.

In an application, the method further includes preparing the selected MSC by selecting the selected MSC based on the cell-surface presence of CD73, CD90, and CD105. In an application, introducing the cell suspension of selected MSC includes introducing a cell suspension of selected MSC that have been selected based on a cell- surface absence of (1) CD34; (2) CD45; (3) HLA-DR; (4) at least one marker selected from the group consisting of: CD 14 and CD l ib; and (5) at least one marker selected from the group consisting of: CD79alpha and CD 19.

In an application, the method further includes preparing the selected MSC by selecting the selected MSC based on the cell-surface absence of (1) CD34; (2) CD45; (3) HLA-DR; (4) at least one marker selected from the group consisting of: CD 14 and CD l ib; and (5) at least one marker selected from the group consisting of: CD79alpha and CD19.

In an application, introducing the cell suspension of selected MSC includes introducing a cell suspension of selected MSC that have been selected based on a cell- surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276. In an application, the method further includes preparing the selected MSC by selecting the selected MSC based on the cell-surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276.

In an application, introducing the cell suspension of selected MSC includes introducing a cell suspension of selected MSC that have been selected based on a cell- surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD106, CD140b, CD271, MSCA-1, Stro-1, SSEA4 and CD146.

In an application, the method further includes preparing the selected MSC by selecting the selected MSC based on the cell-surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD106, CD 140b, CD271, MSCA-1, Stro-1, SSEA4 and CD 146.

In an application, introducing the cell suspension of selected MSC includes introducing a cell suspension of selected MSC that have been selected based on a cell- surface absence of CD40, CD80 and CD86. In an application, the method further includes preparing the selected MSC by selecting the selected MSC based on the cell-surface absence of CD40, CD80 and CD86. In an application, introducing the cell suspension of selected MSC includes introducing a cell suspension of selected MSC that have low cell-surface levels of Major Histocompatibility Complex class I molecules and Major Histocompatibility Complex class II molecules. In an application, the method further includes preparing the selected MSC by selecting the selected MSC based on the low cell-surface levels of Major Histocompatibility Complex class I molecules and Major Histocompatibility Complex class II molecules.

In an application, the cell suspension is a cell suspension of MSC and producer cells, the producer cells containing exogenous genetic material that encodes an extracellular sensor molecule, and introducing the cell suspension includes introducing the cell suspension of MSC and producer cells.

In an application:

the structure is tubular,

the wall shapes the cavity as a lumen having a diameter of 0.5-1.5 mm, and introducing the cell suspension includes introducing the cell suspension into the lumen.

In an application:

the structure is tubular,

the wall shapes the cavity as a lumen having a diameter of up to 5 mm, and introducing the cell suspension includes introducing the cell suspension into the lumen.

In an application, the cell suspension is a suspension of MSC in a hydrocolloid solution, introducing the cell suspension includes introducing the suspension of MSC that is in the hydrocolloid solution, and setting the cell suspension includes setting the suspension of MSC that is in the hydrocolloid solution

In an application, the wall is selectively permeable and has a molecular weight cutoff of 10-100 kDa, and providing the tubular structure includes providing the tubular structure that has the selectively-permeable wall. In an application, the wall is selectively permeable and has a molecular weight cutoff of 10-50 kDa, and providing the tubular structure includes providing the tubular structure that has the selectively-permeable wall. In an application, the hydrocolloid solution includes alginate, the setting solution contains a divalent cation salt, introducing the cell suspension of MSC in the hydrocolloid solution includes introducing the cell suspension of MSC in the hydrocolloid solution that includes alginate, and setting the cell suspension by placing the structure in a setting solution includes setting the cell suspension by placing the structure in the setting solution that contains the divalent cation salt.

In an application, the structure is a tubular structure, the wall circumscribes the cavity and shapes the cavity as a lumen, and introducing the cell suspension includes introducing the cell suspension into the lumen. In an application, introducing the cell suspension into the lumen includes introducing the cell suspension into the lumen via an open proximal end of the lumen, and the method further includes plugging the open end of the lumen subsequently to the step of introducing and prior to the step of setting.

In an application, the tubular structure is coupled to an optical fiber that plugs and extends away from a distal end of the lumen, and providing the tubular structure includes providing the tubular structure that is coupled to the optical fiber that plugs and extends away from the distal end of the lumen.

In an application:

the cell suspension is a first cell suspension,

the method further includes prior to introducing the first cell suspension, introducing into the cavity a core including producer cells in a gel, the producer cells containing exogenous genetic material that encodes an extracellular sensor molecule, and introducing the first cell suspension into the cavity includes introducing the first cell suspension into the cavity such that at least part of the first cell suspension is disposed between the core and the wall.

In an application, introducing the cell suspension includes advancing a tube through an open proximal end of the cavity toward a distal end of the cavity, and injecting the cell suspension into the cavity while progressively withdrawing the tube from the cavity. In an application, the cell suspension is a first cell suspension, and the method further includes: introducing a second cell suspension into the cavity, the second cell suspension being a suspension of producer cells in a hydrocolloid solution, the producer cells containing exogenous genetic material that encodes an extracellular sensor molecule, and subsequently, setting the second cell suspension. In an application:

the structure includes a selectively-permeable divider within the cavity, introducing the first cell suspension into the cavity includes introducing the first cell suspension on a first side of the divider, and

introducing the second cell suspension into the cavity includes introducing the second cell suspension on a second side of the divider.

In an application, introducing the second cell suspension includes introducing the second cell suspension after the step of setting the first cell suspension.

In an application, introducing the first cell suspension includes introducing the first cell suspension after the step of setting the second cell suspension. In an application, introducing the second cell suspension includes introducing the second cell suspension subsequently to the step of introducing the first cell suspension, and prior to the step of setting the first cell suspension.

In an application:

setting the first cell suspension includes setting the first cell suspension while a core is disposed within the cavity,

the method further includes removing the core from the cavity after the step of setting the first cell suspension, and

introducing the second cell suspension into the lumen includes introducing the second cell suspension into a space that remains within the set first cell suspension as a result of the removal of the core.

There is further provided, in accordance with an application of the present invention, apparatus, configured to be implanted in a body of a subject, the apparatus including:

a sensor, configured to detect a parameter of the subject;

an interface surface, configured to provide communication between the sensor and the body; and a plurality of cells selected from the group consisting of: mesenchymal stem cells (MSC), dermal fibroblasts (DF), and fusion cells including MSC fused with another cell type, the selected cells being immobilized with respect to at least one element selected from the group consisting of: the sensor and the interface surface, and being positioned to modulate a cellular function of the body of the subject with respect to the at least one selected element,

the apparatus being implantable in the body of the subject.

In an application, the selected cells include the DF.

In an application, the selected cells are autologous to the subject. In an application, the selected cells are allogeneic to the subject.

In an application, the interface surface includes a substance-exchange surface, configured to facilitate movement of a body substance through the substance-exchange surface to the sensor.

In an application, the interface surface is configured to provide chemical communication between the sensor and the body.

In an application, the selected cells include the fusion cells.

In an application, the selected cells include the MSC.

In an application, the MSC include MSC that have been derived from a human tissue selected from the group consisting of: bone marrow, placental blood, cord blood, Wharton's jelly, dental pulp and adipose tissue.

In an application, the MSC have been selected based on a cell-surface presence of CD73, CD90 and CD 105.

In an application, the MSC have been selected based on a cell-surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276. In an application, the MSC have been selected based on a cell-surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD106, CD140b, CD271, MSCA-1, Stro-1, SSEA4 and CD146.

In an application, the MSC have been selected based on a cell- surface absence of CD40, CD80 and CD86.

In an application, the sensor is configured to detect an analyte of the body of the subject, and the interface surface is configured to provide the communication by facilitating movement of the analyte through the interface surface.

In an application, the apparatus is configured to synthesize a sensor molecule, configured to bind the analyte.

In an application, the selected cells are configured to express the sensor molecule. In an application, the selected cells contain exogenous genetic material that encodes the sensor molecule.

In an application, the plurality of selected cells includes a first plurality of cells, and the apparatus further includes a second plurality of cells, configured to express the sensor molecule. In an application, the first plurality of cells and the second plurality of cells are interspersed with each other.

In an application, the first plurality of cells is coupled to a first plurality of carriers, the second plurality of cells is coupled to a second plurality of carriers, and the first and second pluralities of carriers are interspersed with each other. In an application, the first plurality of cells is disposed in a first cell compartment of the apparatus, and the second plurality of cells is disposed in a second cell compartment of the apparatus.

In an application, the second cell compartment at least partly surrounds the first cell compartment. In an application, at least one of the compartments contains a hydrogel. In an application, at least one of the compartments contains a three-dimensional scaffold to which the respective plurality cells is coupled.

In an application, the apparatus further includes a selectively-permeable barrier that surrounds at least one cell compartment selected from the group consisting of: the first cell compartment and the second cell compartment.

In an application, the sensor includes a chamber containing a sensor molecule, configured to bind the analyte.

In an application, the selected cells are disposed at least in part around an outer surface of the chamber. In an application, the sensor includes circuitry in optical communication with the chamber.

In an application, the sensor is configured to detect the analyte by detecting light from the chamber.

a sensor, configured to detect a parameter of the subject;

an interface surface, configured to provide communication between the sensor and the body; and

a plurality of regulatory T cells, immobilized with respect to at least one element selected from the group consisting of: the sensor and the interface surface, and being positioned to modulate a cellular function of the body of the subject with respect to the at least one selected element,

the apparatus being implantable in the body of the subject. There is further provided, in accordance with an application of the present invention, apparatus, including:

a tubular structure including a circumferential wall that (i) defines a lumen, and (ii) has a molecular weight cut-off of 10-100 kDa;

a hydrogel, disposed within the lumen;

a plurality of producer cells, suspended within the hydrogel, the producer cells containing exogenous genetic material that encodes an extracellular molecule; and a plurality of regulatory T cells, suspended within the hydrogel.

providing a tubular structure having a circumferential wall that (i) defines a lumen, and (ii) has a molecular weight cut-off of 10-100 kDa;

introducing a cell suspension into the lumen, the cell suspension being a suspension of regulatory T cells in a hydrocolloid solution; and

subsequently, setting the cell suspension by placing the tubular structure in a setting solution. There is further provided, in accordance with an application of the present invention, a method, including:

providing a human tissue selected from the group consisting of: bone marrow, placental blood, cord blood, Wharton's jelly, dental pulp and adipose tissue;

extracting a cell population from the selected human tissue;

enriching the cell population based on cell-surface expression of CD73, CD90, and

CD105; and

subsequently, coupling the enriched cell population to an implant.

In an application, enriching the cell population includes enriching the cell population based on cell-surface absence of (1) CD34; (2) CD45; (3) HLA-DR; (4) at least one marker selected from the group consisting of: CD 14 and CD l ib; and (5) at least one marker selected from the group consisting of: CD79alpha and CD19.

In an application, enriching the cell population includes enriching the cell population based on cell-surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276. In an application, enriching the cell population includes enriching the cell population based on cell-surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD106, CD140b, CD271, MSCA-1, Stro-1, SSEA4 and CD 146.

In an application, enriching the cell population includes enriching the cell population based on cell-surface absence of CD40, CD80 and CD86. In an application, enriching the cell population includes enriching the cell population based on low cell-surface expression of Major Histocompatibility Complex class I molecules and Major Histocompatibility Complex class II molecules.

providing a structure having a wall that is shaped to define a cavity;

immobilizing a plurality of mesenchymal stem cells (MSC) on an outside of the structure; and

immobilizing a plurality of producer cells within the cavity, the producer cells containing exogenous genetic material that encodes an extracellular molecule.

There is further provided, in accordance with an application of the present invention, apparatus for use with a subject, the apparatus including a sensor, the sensor: being configured to detect a parameter of the subject,

including an implantable element, implantable in the subject, and including:

an interface surface, configured to provide communication between the implant and the body; and

a plurality of cells selected from the group consisting of: mesenchymal stem cells (MSC), dermal fibroblasts (DF), and fusion cells including MSC fused with another cell type, the selected cells being immobilized with respect to the implantable element, and being positioned to modulate a cellular function of the body of the subject with respect to the implantable element.

There is further provided, in accordance with an application of the present invention, apparatus for use with a subject, the apparatus including:

an implant, including a wall having an external surface; and

a coating, disposed on the external surface, and including platelet material.

In an application, the coating includes platelet-rich plasma.

In an application, the coating includes platelet microparticles.

In an application, the coating includes a hydrogel.

In an application, the coating includes polyethylene glycol.

In an application, the coating includes alginate. In an application, the coating has a thickness of 50-700 microns. In an application, the coating has a thickness of 100-500 microns. In an application, the coating is water-permeable.

In an application, at least a portion of the wall is selectively-permeable, and the wall is shaped to define a cavity.

In an application, the coating is disposed at least on the external surface of the portion of the wall.

In an application, the implant includes living cells disposed within the cavity.

providing platelet-rich plasma (PRP);

preparing a mixture by mixing a hydrogel precursor with the PRP; and

subsequently, forming a hydrogel by crosslinking the hydrogel precursor.

In an application, the method further includes, prior to forming the hydrogel, coating the mixture onto an external surface of an implant.

In an application, the hydrogel precursor includes polyethylene glycol (PEG), and mixing the hydrogel precursor with the PRP includes mixing the PEG with the PRP.

In an application, the hydrogel precursor includes alginate, and mixing the hydrogel precursor with the PRP includes mixing the alginate with the PRP.

The present invention will be more fully understood from the following detailed description of applications thereof, taken together with the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic illustration of an implant comprising a sensor and a plurality of protector cells, in accordance with some applications of the invention;

Fig. 2 is a schematic illustration of an implant comprising a sensor and a plurality of protector cells, in accordance with some applications of the invention;

Fig. 3 is a schematic illustration of an implant comprising a sensor and a plurality of protector cells, in accordance with some applications of the invention; Fig. 4 is a schematic illustration of an implant comprising a sensor and a plurality of protector cells, in accordance with some applications of the invention;

Fig. 5 is a schematic illustration of an implant comprising a sensor, in accordance with some applications of the invention; Fig. 6 is a schematic illustration of an implant comprising a sensor and a plurality of protector cells, in accordance with some applications of the invention;

Fig. 7 is a schematic illustration of an implant comprising a sensor, in accordance with some applications of the invention;

Figs. 8-9 are schematic illustrations of implants, in accordance with some applications of the invention;

Figs. 10-11 are schematic illustrations showing at least some steps in respective techniques for preparing implants, in accordance with some applications of the invention;

Figs. 12A-B are schematic illustrations showing results from experiments performed in order to determine the effectiveness of mesenchymal stem cells in increasing in vivo survival of producer cells, in accordance with some applications of the invention;

Fig. 13 is a schematic illustration of an implant having a coating comprising platelet material, in accordance with some applications of the invention; and

Fig. 14 is a schematic illustration showing results from experiments in which implants having the coating were implanted, in order to determine the effect of the platelet material on vascularization around the implants, in accordance with some applications of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Protector cells may provide one or more advantages to an implant compared to an identical implant that does not comprise protector cells. Following implantation of such an identical implant that does not comprise protector cells, graft rejection and foreign body response (FBR) may occur, resulting in a degree of isolation of the implant from the body of the subject. Such isolation may reduce the functionality of the implant, e.g., by inhibiting chemical and/or electrical communication between the interface surface and the body of the subject. For example, movement (e.g., diffusion or pumping) of an analyte into the implant, and/or a therapeutic substance out of the implant, may be inhibited. For implants that comprise live cells, such as producer cells described hereinbelow, this isolation may also result in the death of the producer cells, e.g., due to reduced supply of nutrients and/or oxygen, reduced removal of waste products, and/or direct damage by the host immune system. The protector cells typically modify (e.g., inhibit) one or more of these cellular functions, thereby protecting the implant and preserving its functionality. For example, protector cells 26 may (1) inhibit rejection of the implant, e.g., via secretion of soluble immunomodulatory (e.g., immunosuppressive) factors, such as immunomodulatory cytokines, (2) inhibit a foreign body response, and/or (3) stimulate angiogenesis in tissue surrounding the implant, thereby increasing blood supply to the implant. For some applications, the protector cells are mesenchymal stem cells (MSC). For some applications, the protector cells are dermal fibroblasts (DF). For some applications, the protector cells are fusion cells of MSC and another cell type, as described in more detail hereinbelow. For some applications, the protector cells are regulatory T cells, such as lymphocytes selected on the basis of expression of CD4 and CD25, and low or absent expression of CD127 (CD4(+)CD25(+)CD127(low/-)).

Reference is made to Fig. 1, which is a schematic illustration of an implant 20 comprising a sensor 22, and a plurality of protector cells 26, in accordance with some applications of the invention. Implant 20 (e.g., sensor 22 thereof, comprising an implantable element) comprises a chamber 28 containing at least one sensor molecule 30. (Molecule 30 may comprise a single molecule type or more than one molecule type, such as a complex.) Molecule 30 typically comprises a protein. Molecule 30 is replenished by a plurality of producer cells 36, disposed within a producer-cell compartment 38, which is separated from chamber 28 by a selectively-permeable divider 40 (e.g., a selectively- permeable barrier, such as a membrane) that allows passage therethrough of the detector protein, but not the producer cells, from the compartment into the chamber. Producer cells 36 typically contain exogenous genetic material that encodes sensor molecule 30 (e.g., the producer cells are genetically modified to synthesize the sensor molecule). Compartment 38, cells 36 and divider 40 thereby serve as a replenishment unit.

Chamber 28 has a covering 29 that separates at least part of chamber 28 from the outside of the chamber (e.g., the covering defines an outer surface of at least part of the chamber), and serves as an interface surface 24 of the implant. Covering 29 comprises a selectively-permeable barrier (e.g., a membrane) that allows passage therethrough of at least one analyte of the body of the subject, but not of sensor molecule 30. Interface surface 24 thereby provides chemical communication between the sensor and the body of the subject (e.g., serves as a substance-exchange surface). Typically, covering 29 and divider 40 are selectively permeable by inhibiting passage therethrough of molecules that have a molecular weight above a respective threshold molecular weight. Typically, covering 29 has a lower threshold than does divider 40.

Fluorescence resonance energy transfer (FRET) involves the transfer of photon energy from an excited fluorophore (the donor) to another fluorophore (the acceptor), when the donor and acceptor molecules are in close proximity to each other. FRET enables the determination of the relative proximity of the molecules, for investigating, for example, molecular interactions between two protein partners, structural changes within one molecule, and ion concentrations. Fluorescent proteins (FPs) can be genetically fused to proteins of interest and expressed in cells. Examples of FP pairs useful for performing FRET measurements in living cells include, but are not limited to, those in the following table:

Sensor 22 detects a concentration of the analyte of the subject using FRET. Sensor

22 comprises a light source 32 (e.g., an LED or a laser), an optical detector 42 (e.g., a CCD or other suitable detector), and circuitry 50 in electrical communication with the light source and optical detector. Typically, the analyte is glucose, sensor 22 is configured to detect a glucose concentration (e.g., a blood glucose concentration) of the subject using FRET, and sensor molecule 30 comprises a fluorescent protein donor, a fluorescent protein acceptor, and a binding protein for glucose. Covering 29 (e.g., interface surface 24) is configured to allow passage of glucose therethrough, and glucose from the body of the subject diffuses through the covering into chamber 28, where it becomes bound to sensor molecule 30. Light source 32 and detector 42 are in optical communication with chamber 28. For some applications, and as shown, light source 32 and detector 42 are in optimal communication with chamber 28 via an optical fiber 48. Alternatively, light source 32 and detector 42 may be disposed on and/or within chamber 28. Circuitry 50 drives light source 32 to provide light to chamber 28, and detects light emitted by molecule 30 using optical detector 42. Molecule 30 is configured such that binding of glucose thereto changes the conformation of the sensor molecule from an unbound conformation to a bound conformation, and thereby changes the distance between the donor and acceptor. Using the signal from optical detector 42, circuitry 50 detects this change in distance and determines the quantity of the signal resulting from subsets of sensor molecule 30 that are in each of the two conformations, thereby enabling a calculation of the concentration of the analyte.

This detection is described in more detail, mutatis mutandis, in US Patent 7,951,357 to Gross et al.; US Patent Application Publication 2010/0202966 to Gross et al.; US Patent Application Publication 2012/0059232 to Gross et al.; US Provisional Patent Application 61/746,691 to Brill et al., filed December 28, 2012, and entitled "Apparatus for facilitating cell growth in an implantable sensor"; and PCT application IB/2013/061368 to Brill et al., filed December 27, 2013, and entitled "Apparatus for facilitating cell growth in an implantable sensor", all of which are incorporated herein by reference.

For some applications, implant 20 comprises a control unit 34 that comprises circuitry 50, light source 32, and optical detector 42. For some such applications, control unit 34 comprises a power source 52, such as a battery and/or a wireless power-receiver (e.g., a rectifying antenna or an induction antenna). For some applications, control unit 34 comprises a substance dispenser 54 (e.g., comprising a reservoir and a pump), which is driven by circuitry 50 at least in part responsively to the detected parameter of the subject. For example, dispenser 54 may contain insulin, and be driven to dispense the insulin by circuitry 50 at least in part responsively to detected blood glucose concentration.

For some such applications, control unit 34 is distinct from chamber 28 and compartment 38 (e.g., to facilitate implantation of the control unit at a site different site from that of chamber 28, or extracorporeal placement of the control unit). For example, optical fiber 48 may be flexible and/or longer than 1 cm (e.g., longer than 3 cm). Alternatively, control unit 34 may be integral with and/or directly coupled to the rest of implant 20 (e.g., optical fiber 48 may be very short or may be replaced with a window, and/or as described hereinabove, light source 32 and detector 42 may be disposed on and/or within chamber 28).

Implant 20 comprises protector cells 26, immobilized with respect to the device (e.g., with respect to sensor 22 and/or interface surface 24) by being stored within a protector-cell compartment 44 that is disposed between producer-cell compartment 38 and the outside of the device, e.g., surrounding compartment 38 on all sides except where compartment 38 meets chamber 28 (e.g., at divider 40). Compartment 44 may be a hollow space, such as a chamber, and/or may comprise a hydrogel in which the protector cells are encapsulated. Typically, compartment 44 is at least partly covered in a selectively- permeable covering 49 (e.g., a membrane). That is, the covering 49 defines at least part of an outer surface of the compartment. For some applications, a continuous covering (e.g., a continuous membrane) serves as covering 29 (and thereby interface surface 24), and covering 49. Typically, another selectively-permeable covering 46 covers at least part of compartment 38 (e.g., separates at least part of compartment 44 from at least part of compartment 38). Covering 46 may be identical in nature to divider 40, covering 49, and/or covering 29, or may be different in nature.

As described hereinabove, protector cells 26 typically modify one or more cellular functions of the body of the subject, thereby protecting implant 20 and preserving its functionality. Cells 26 typically provide this protective effect via secretion of immunomodulatory (e.g., immunosuppressive) factors, which diffuse out of compartment 44, inhibit rejection of the implant and/or producer cells 36, and thereby inhibit isolation of the implant from the body of the subject. As also described hereinabove, cells 26 may alternatively or additionally stimulate angiogenesis, thereby maintaining, or even enhancing, blood supply in the vicinity of implant 20, and thereby maintaining, or even enhancing, glucose diffusion into the implant via interface surface 24.

Reference is made to Fig. 2, which is a schematic illustration of an implant 120 comprising a sensor 122 and a plurality of protector cells 26, in accordance with some applications of the invention. Implant 120 is typically identical to implant 20 described hereinabove, except where noted, and elements of implant 120 typically have identical characteristics and functions to identically-named elements of implant 20, mutatis mutandis, except where noted. Implant 120 (e.g., sensor 122 thereof) comprises a chamber 128 containing sensor molecule 30, a producer-cell compartment 138 containing producer cells 36, and a selectively-permeable divider 140 through which molecule 30 passes from compartment 138 into chamber 128. In contrast to implant 20, a protector-cell compartment 144 containing protector cells 26 surrounds both producer-cell compartment 138 and chamber 128.

A selectively-permeable covering 149 covers (e.g., defines an outer surface of) at least part of compartment 144, and thereby serves as an interface surface 124 of the implant. A selectively-permeable covering 129 covers (e.g., defines an outer surface of) at least part of chamber 128. A selectively-permeable covering 146 covers (e.g., defines an outer surface of) at least part of compartment 138. For some applications, coverings 129 and 146 are defined by a single continuous covering.

Coverings 129 and 146 have a lower threshold than does divider 140. That is, the divider allows passage therethrough of molecules having a higher molecular weight than those allowed by coverings 129 and 146. Covering 149 may have the same threshold as coverings 129 and 146.

Reference is made to Fig. 3, which is a schematic illustration of an implant 220 comprising a sensor 222 and a plurality of protector cells 26, in accordance with some applications of the invention. Implant 220 is typically identical to implant 20 described hereinabove, except where noted, and elements of implant 220 typically have identical characteristics and functions to identically-named elements of implant 20, mutatis mutandis, except where noted.

Implant 220 (e.g., sensor 222 thereof) comprises a chamber 228 containing sensor molecule 30, a producer-cell compartment 238 containing producer cells 36, and a selectively-permeable divider 240 through which molecule 30 passes from compartment 238 into chamber 228. Compartment 238 surrounds at least part of chamber 228, and divider 240 typically serves as a covering 229, which covers (e.g., defines an outer surface of) at least part of chamber 228. A protector-cell compartment 244 containing protector cells 26 surrounds at least part of producer-cell compartment 238 (and thereby typically also surrounds at least part of chamber 228).

A selectively-permeable covering 249 covers (e.g., defines an outer surface of) at least part of compartment 244, and thereby serves as an interface surface 224 of the implant. A selectively-permeable covering 246 covers (e.g., defines an outer surface of) at least part of compartment 238.

Covering 246 has a lower threshold than does divider 240 (which serves as covering 229). That is, divider 240 allows passage therethrough of molecules having a higher molecular weight than those allowed by covering 246. Covering 249 may have the same threshold as covering 246.

Reference is made to Fig. 4, which is a schematic illustration of an implant 320 comprising a sensor 322 and a plurality of protector cells 26, in accordance with some applications of the invention. Implant 320 is typically identical to implant 20 described hereinabove, except where noted, and elements of implant 320 typically have identical characteristics and functions to identically-named elements of implant 20, mutatis mutandis, except where noted.

Implant 320 (e.g., sensor 322 thereof) comprises a chamber 328 containing sensor molecule 30. In contrast to implants 20, 120, and 220, implant 320 comprises a unified cell compartment 356 that contains producer cells 36 and protector cells 26, and thereby serves both as a producer-cell compartment 338 and as a protector-cell compartment 344. Implant 320 comprises a selectively-permeable divider 340 that separates unified cell compartment 356 from chamber 328, and through which molecule 30 passes from compartment 356 into chamber 328. A selectively-permeable covering 329 covers (e.g., defines an outer surface of) at least part of chamber 328, and thereby serves as an interface surface 324 of the implant. A selectively-permeable covering 349 covers (e.g., defines an outer surface of) at least part of compartment 356. For some applications, coverings 329 and 349 are defined by a single continuous covering. Coverings 329 and 349 have a lower threshold than does divider 340. That is, the divider allows passage therethrough of molecules having a higher molecular weight than those allowed by coverings 329 and 349.

As described hereinabove, unified cell compartment 356 contains both producer cells 36 and protector cells 26. Producer cells 36 and protector cells 26 are typically interspersed within compartment 356. For some applications, cells 36 are disposed on and/or in (e.g., are coupled to) a first plurality of carriers 358 (e.g., carrier beads), cells 26 are disposed on and/or in a second plurality of carriers 360, and the two pluralities of carriers are interspersed within compartment 356. Alternatively, cells 36 and 26 may be mixed together within a medium (e.g., a hydrogel).

Reference is made to Fig. 5, which is a schematic illustration of an implant 420 comprising a sensor 422, in accordance with some applications of the invention. Implant 420 is typically identical to implant 320 described hereinabove, except where noted, and elements of implant 420 typically have identical characteristics and functions to identically-named elements of implant 320, mutatis mutandis, except where noted.

Implant 420 (e.g., sensor 422 thereof) comprises a chamber 428 containing sensor molecule 30. Similarly to implant 320, and in contrast to implants 20, 120, and 220, implant 420 comprises a unified cell compartment 456 that serves both as a producer-cell compartment 438 and as a protector-cell compartment 444. In contrast to unified cell compartment 356 of implant 320, unified cell compartment 456 of implant 420 does not contain distinct producer cells and protector cells. Rather, compartment 456 contains dual-function cells 426, which serve both as producer cells and as protector cells. For some applications, dual-function cells 426 are protector cells that are configured to produce the sensor molecule. For example, the protector cells may contain exogenous genetic material that encodes the sensor molecule (e.g., the protector cells may be transfected with the genetic material or otherwise genetically engineered to contain and/or express the genetic material). For some applications, dual-function cells 426 comprise fusion cells of protector cells and producer cells. For example, each dual- function cell 426 may comprise an MSC that has fused with a respective producer cell. Example publications that describe fusion between MSC and other cells include: Kouris NA et al. (2012) Stem Cells Int. 2012:414038 (PMID 22701126); Nygren JM. et al., Nat Med. 2004 May;10(5):494 (PMID 15107841); Rizvi AZ. et al., Proc Natl Acad Sci U S A. 2006 Apr 18;103(16):6321 (PMID 16606845); Bae JS. et al., Stem Cells. 2007 May;25(5): 1307 (PMID 17470534); Wang Y. et al., Int J Oncol. 2012 Feb;40(2):370 (PMID 22002183); Yanai G. et al., PLoS One. 2013 May 28;8(5):e64499 (PMID 23724055); Kemp K. et al., Neuropathol Appl Neurobiol. 2011 Feb;37(2): 166 (PMID 20819172); and Goncalves MA. et al., Hum Mol Genet. 2006 Jan 15;15(2):213 (PMID 16321987).

Implant 320 comprises a selectively-permeable divider 440 that separates unified cell compartment 456 from chamber 428, and through which molecule 30 passes from compartment 456 into chamber 428. A selectively-permeable covering 429 covers (e.g., defines an outer surface of) at least part of chamber 428, and thereby serves as an interface surface 424 of the implant. A selectively-permeable covering 449 covers (e.g., defines an outer surface of) at least part of compartment 456. For some applications, coverings 429 and 449 are defined by a single continuous covering.

Coverings 429 and 449 have a lower threshold than does divider 340. That is, the divider allows passage therethrough of molecules having a higher molecular weight than those allowed by coverings 429 and 449.

Reference is made to Fig. 6, which is a schematic illustration of an implant 520 comprising a sensor 522 and a plurality of protector cells 26, in accordance with some applications of the invention. Implant 520 is typically identical to implant 220 described hereinabove, except where noted, and elements of implant 520 typically have identical characteristics and functions to identically-named elements of implant 220, mutatis mutandis, except where noted. Implant 520 (e.g., sensor 522 thereof) comprises a chamber 528 containing sensor molecule 30. Similarly to implant 320, and in contrast to implants 20, 120 and 220, implant 520 comprises a unified cell compartment 556 that contains producer cells 36 and protector cells 26, and thereby serves both as a producer-cell compartment 538 and as a protector-cell compartment 544. Implant 520 comprises a selectively-permeable divider 540 that separates unified cell compartment 556 from chamber 528, and through which molecule 30 passes from compartment 556 into chamber 528. Compartment 556 surrounds at least part of chamber 528, and divider 540 typically serves as a covering 529, which covers (e.g., defines an outer surface of) at least part of chamber 528. A selectively-permeable covering 549 covers (e.g., defines an outer surface of) at least part of compartment 556, and thereby serves as an interface surface 524 of the implant.

Covering 549 has a lower threshold than does divider 540 (which serves as covering 529). That is, divider 540 allows passage therethrough of molecules having a higher molecular weight than those allowed by covering 549. For some applications, implant 520 combines (1) the general structure described with reference to implant 220, in which cell compartments surround at least part of the chamber containing molecule 30, and (2) the unified cell compartment described with reference to implant 320. In implant 520, producer cells 36 and protector cells 26 are interspersed within unified cell compartment 556, as described hereinabove for unified cell compartment 356 of implant 320, mutatis mutandis.

Reference is made to Fig. 7, which is a schematic illustration of an implant 620 comprising a sensor 622, in accordance with some applications of the invention. Implant 620 is typically identical to implant 520 described hereinabove, except where noted, and elements of implant 620 typically have identical characteristics and functions to identically-named elements of implant 520, mutatis mutandis, except where noted.

Implant 620 (e.g., sensor 622 thereof) comprises a chamber 628 containing sensor molecule 30. Similarly to implant 520, implant 620 comprises a unified cell compartment 656 that serves both as a producer-cell compartment 638 and as a protector-cell compartment 644. In contrast to unified cell compartment 556 of implant 520, (and similarly to unified cell compartment 456 of implant 420) unified cell compartment 656 of implant 620 does not contain distinct producer cells and protector cells. Rather, compartment 656 contains dual-function cells 426, which serve both as producer cells and as protector cells, as described hereinabove.

Implant 620 comprises a selectively-permeable divider 640 that separates unified cell compartment 656 from chamber 628, and through which molecule 30 passes from compartment 656 into chamber 628. Compartment 656 surrounds at least part of chamber 628, and divider 640 typically serves as a covering 629, which covers (e.g., defines an outer surface of) at least part of chamber 628. A selectively-permeable covering 649 covers (e.g., defines an outer surface of) at least part of compartment 656, and thereby serves as an interface surface 624 of the implant.

Covering 649 has a lower threshold than does divider 640 (which serves as covering 629). That is, divider 640 allows passage therethrough of molecules having a higher molecular weight than those allowed by covering 649.

For some applications, implant 620 combines (1) the general structure described with reference to implant 520, in which a unified cell compartment surrounds at least part of the chamber containing molecule 30, and (2) the dual-function cells described with reference to implant 420, mutatis mutandis.

Reference is made to Figs. 8-9, which are schematic illustrations of implants 720 and 820, respectively, in accordance with some applications of the invention. The implants described with reference to Figs. 1-7 are described as each comprising a chamber containing sensor molecule 30. For some applications, the implants described with reference to Figs. 1-7 do not comprise a dedicated chamber for sensor molecule 30. Two examples of such applications are illustrated by Figs. 8 and 9. Implant 720 (Fig. 8) comprises a sensor 722, and is typically identical to implant

120 described hereinabove, except where noted, and elements of implant 720 typically have identical characteristics and functions to identically-named elements of implant 120, mutatis mutandis, except where noted. A producer-cell compartment 738, containing producer cells 36, also serves as a chamber 728 that contains sensor molecule 30. That is, sensor molecule 30 typically performs its function within compartment 738. For example, optical fiber 48 may be in optical communication with compartment 738. A protector cell compartment 744 is disposed between compartment 738 and a selectively-permeable covering 749 of the implant (e.g., compartment 744 may circumscribe compartment 738). Covering 749 may serve as an interface surface 724 of implant 720. For some applications, a selectively-permeable covering 746 separates compartment 738 from chamber 728.

Implant 820 (Fig. 9) comprises a sensor 822, and is typically identical to implant 320 described hereinabove, except where noted, and elements of implant 820 typically have identical characteristics and functions to identically-named elements of implant 320, mutatis mutandis, except where noted. A unified cell compartment 856, containing producer cells 36 and protector cells 26, also serves as a chamber 828 that contains sensor molecule 30. That is, sensor molecule 30 typically performs its function within compartment 838. For example, optical fiber 48 may be in optical communication with compartment 838. A selectively-permeable covering 849 covers at least part of compartment 856, and may serve as an interface surface 824 of implant 820.

Reference is made to Figs. 10 and 11, which are schematic illustrations showing at least some steps in respective techniques for preparing implants described herein, in accordance with some applications of the invention. For illustrative purposes, Figs. 10 and 11 show steps in the preparation of an implant similar to implant 720, but it is to be noted that the techniques (and/or steps thereof) may be used in the preparation of other implants described herein, mutatis mutandis.

A structure, e.g., a tubular structure 910, is provided, comprising a wall, e.g., a circumferential wall 912, which defines a cavity (e.g., a lumen). Wall 912 is selectively permeable, and typically serves as an interface surface 914 of the implant. Wall 912 thereby typically serves as a semi -permeable covering of the implant (e.g., such as covering 749, shown in Fig. 8). Wall 912 typically has a molecular weight cut-off (MWCO) (e.g., a pore size) of greater than 10 kDa and/or less than 100 kDa, such as 10- 100 kDa (e.g., 10-50 kDa, e.g., 20-40 kDa, such as 30 kDa).

In both Fig. 10 and Fig. 11, a suspension 920 of MSC is introduced into the cavity of structure 910, and is subsequently set. Typically, the MSC are suspended in a hydrocoUoid solution, such as alginate. Further typically, the MSC suspension is set (e.g., into a hydrogel) by placing structure 910 in a setting solution, such as a solution of a divalent cation salt, such as a salt of calcium, magnesium, strontium, or barium. In both Fig. 10 and Fig. 11, a core is disposed in the cavity of tubular structure 910 during setting of the MSC suspension. In Fig. 10, the core is a temporary core 916, which is removed subsequently to setting the MSC suspension. In Fig. 11, the core comprises a set suspension of producer cells, which remains in place subsequently to setting the MSC suspension.

Reference is now made to Fig. 10. In frame A, an introducer 918 is introduced via an open proximal end 922 into the cavity of structure 910, around a core 916, which has previously been placed in the cavity. Introducer 918 is used to introduce the MSC suspension into the cavity. Alternatively, core 916 is introduced subsequently to introducing the MSC suspension (but prior to setting the MSC suspension). The MSC suspension is then set (frame B), such as by placing structure 910 in a bath of the setting solution (not shown). In frame C, core 916 has been removed, and an introducer 919 is introduced into the remaining space. A suspension 926 of producer cells (e.g., in a hydrocoUoid solution) is introduced into the space via introducer 919, and is subsequently set (e.g., into a hydrogel), such as by returning structure 910 to the setting solution. Frame D shows the resulting state. Typically, proximal end 922 is subsequently plugged with a plug 928 (e.g., comprising silicone).

For some applications, at least proximal end 922 is reinforced (e.g., with a liner) into which plug 928 is inserted, e.g., so as to reduce a likelihood of damage to tubular structure 910 due to radial forces from the plug.

For some applications in which the implant comprises optical fiber 48, the optical fiber plugs and extends away from a distal end 924 of the cavity of structure 910. For example, structure 910 may be provided with optical fiber 48 already in place. Alternatively, optical fiber 48 may be inserted after the introduction (and optionally after the setting) of the hydrocolloid solutions.

Reference is now made to Fig. 11. In frame A, a core 917 comprising set suspension 926 of producer cells is disposed within the cavity of structure 910. For some applications, core 917 is produced outside of structure 910 (e.g., in a separate mold) and is introduced pre-set. For some applications, core 917 is produced within structure 910, such as by temporarily placing a mold (not shown) within the cavity, introducing suspension 926 as a liquid, and setting it in situ. Frame B shows introducer 918 being used to subsequently introduce MSC suspension 920, which is then set as described hereinabove. Frame C shows the resulting state. Frame D shows proximal end 922 having been plugged with plug 928, as described hereinabove.

Reference is again made to Figs. 10-11. As described hereinabove, for some applications a selectively-permeable covering or divider separates the compartment in which the protector cells are disposed from the compartment in which the producer cells are disposed. For such applications, the techniques described with reference to Figs. 10- 11 may be adapted accordingly, e.g., by introducing the MSC suspension on one side of the covering or divider, and introducing the producer cell suspension on the other side.

Reference is made to Figs. 12A-B, which are schematic illustrations showing results from experiments performed in order to determine the effectiveness of MSC in increasing in vivo survival of producer cells within tubular structure 910, in accordance with some applications of the invention.

The experiment was performed as follows: The circumferential wall of the tubular structure used comprised selectively-permeable PES, having a MWCO of 30 kDa. 15,000 producer cells (transgenic human ARPE19 cells, transfected with exogenous DNA encoding a FRET-based glucose biosensor) were formed into a core in 0.5 microliter of alginate which was set in a solution of 70 mM SrCl.sub.2. 1 microliter of a suspension of MSC (human umbilical cord cells; ATCC (Virginia, USA) cat# PCS 500.010) in alginate was introduced around the core, and set. Each tubular structure contained either 1000, 3000 or 9000 MSC, and a control group had no MSC. Five tubular structures of each group were then subcutaneously inserted into a healthy pig, in clusters containing one tubular structure of each group.

After one month, the tubular structures were retrieved, and the survival of the producer cells was tested. Fig. 12A shows quantitative results of testing with PrestoBlue (R) (Life Technologies cat # A-13261). Fig. 12B shows semi-quantitative results of testing with Propidium Iodide and Acridine Orange (staining was ranked on a scale of 0-5, where 0 = red or no staining only, and 5 = green staining only).

MSC appear to enhance in vivo survival of the producer cells, and an increased number of MSC appears to increase the statistical significance of this effect (e.g., reducing variability between each implant).

Reference is made to Figs. 13-14. Fig. 13 is a schematic illustration of an implant 780 having a coating 782 comprising platelet material, in accordance with some applications of the invention. Fig. 14 is a schematic illustration showing results from experiments in which implants having coating 782 were implanted, in order to determine the effect of the platelet material on vascularization around the implants, in accordance with some applications of the invention.

Implant 780 is shown in Fig. 13 as being identical to implant 720 (described hereinabove), with the addition of coating 782. For example, implant 780 may comprise implant 720 and coating 782. It is to be noted that the scope of the invention includes the use of coating 782 with any of the implants described herein. The scope of the invention also includes the use of coating 782 with an implant similar to those described herein, but without protector cells (such as an implant described in one or more of the references incorporated herein by reference). The scope of the invention also includes the use of coating 782 with any other implant.

For some applications, coating 782 comprises platelet-rich plasma (PRP). For some applications, coating 782 comprises platelet microparticles (PMP). Both PRP and PMP are hypothesized to promote vascularization in tissue surrounding the implant.

Coating 782 is disposed on an external surface of a wall of the implant. For example, coating 782 may be disposed on an interface surface of the implant, such as selectively-permeable covering 749. Coating 782 is typically water-permeable and therefore does not significantly inhibit the above-described movement of molecules through covering 749. Typically, coating 782 comprises a hydrogel, such as an alginate hydrogel (e.g., as described hereinabove, mutatis mutandis), or a polyethylene glycol hydrogel. For some applications, the coating has a thickness of 50-700 microns (e.g., 100- 500 microns). For some applications in which coating 782 comprises PRP and a hydrogel, the coating is prepared by mixing a hydrogel precursor with PRP, and subsequently forming the hydrogel by crosslinking the hydrogel precursor. For example, for some applications sodium alginate is added directly to PRP, and the resulting mixture is coated onto an external surface of the implant prior to forming the hydrogel (e.g., by immersing the coated implant in a solution of a divalent cation salt).

Fig. 14 shows results from experiments performed to determine the effect of the platelet material on vascularization around the implants. Implants similar to those shown in Fig. 13 (without optical fiber 48 or control unit 34) were implanted subcutaneously in rats, and vascularization in the tissue surrounding the implants was examined 1 and 3 weeks post-implantation. For the experiment, coating 782 comprised PEG and PRP. For control implants, coating 782 comprised PEG with no PRP. At 1 week, 4 implants were examined per group, and at 3 weeks, 2 implants were examined per group. Vascularization was determined by scoring histological images (two images per implant). For each image, a "near" zone (0-150 microns from the implant surface) and a "far" zone (150-300 microns from the implant surface) were scored as follows: A score of 0 was given for a zone in which 0-1 significant blood vessels were observed. A score of 1 was given for a zone in which 2-3 significant blood vessels were observed. A score of 2 was given for a zone in which 4-9 significant blood vessels were observed (counting large vessels as 2 or 3). A score of 3 was given for a zone in which more than 10 significant blood vessels were observed (counting large vessels as 2 or 3). The "near" zone and the "far" zone were each 1 mm long (measured along the surface of the implant), thus each of the zones was 0.15 mm^A2.

The presence of PRP in coating 782 increased vascularization in both the near and far zones. This effect appears to be greater at 3 weeks post-implantation than at 1 week post-implantation. This effect also appears to be greater in the near zone than in the far zone.

Reference is again made to Figs. 1-14. For each implant, the selectively- permeable divider (which separates the chamber that contains the detector molecule from the compartment that contains the cells that produce the detector molecule) typically has a MWCO (i.e., a threshold) of greater than 100 kDa (e.g., greater than 150 kDa, such as greater than 200 kDa); molecules smaller than this threshold are passable through the divider. The threshold is typically sufficiently small so as to prevent passage therethrough of the cells that produce the detector molecule. For example, the divider may define pores that have a diameter of less than 1 micron, such as less than 0.5 microns.

For each implant, the selectively-permeable covering that serves as the interface surface of the implant (e.g., the covering that defines at least part of the chamber containing detector molecule 30) typically has a MWCO (i.e., a threshold) of greater than 10 kDa and/or less than 100 kDa, such as 10-100 kDa (e.g., 10-50 kDa, e.g., 20-40 kDa, such as 30 kDa). The selectively-permeable covering that defines at least part of the chamber containing the protector cells (or the dual-function cells) typically has the same threshold. One or more of these selectively-permeable coverings may comprise a rigid material (e.g., polysulfone and/or polyethersulfone) and/or a hydrogel. For example, one or more of these selectively-permeable coverings may comprise a hollow fiber having (i) a circumferential wall comprising modified polyethersulfone (PES) having a MWCO of greater than 10 kDa and/or less than 100 kDa, such as 10-100 kDa (e.g., 10-50 kDa, e.g., 20-40 kDa, such as 30 kDa), and (ii) an internal diameter of 0.5-1.5 mm (e.g., 1 mm). For some applications, the internal diameter is up to 5 mm. For example, covering 749, covering 849, and circumferential wall 912 typically comprise such a hollow fiber.

For some applications, cells within a compartment are embedded within and/or supported by a three-dimensional scaffold such as a hydrogel or matrix. That is, the compartment is not necessarily a hollow space, but rather a zone in which the cells are disposed. For some such applications, the selectively-permeable covering of that compartment is defined simply by the surface of the three-dimensional scaffold. Alternatively, the selectively-permeable covering of that compartment may comprise a distinct covering that covers the three-dimensional scaffold. For some applications, the carriers described with reference to Figs. 4 and 6 comprise this three-dimensional scaffold. Non-limiting examples of materials that may be used for the three-dimensional scaffold include: proteins (e.g., collagen, silk), polysaccharides (e.g., agar, agarose, alginate, hyaluronan), polymers (e.g., PLGA, polyurethane), and ceramics (e.g., bioactive glass, hydroxyapatite). For some applications, the three-dimensional scaffold is biodegradable and/or bioabsorbable. For some applications, the cells (e.g., the producer cells, the protector cells, and/or the dual-function cells) are cultured and/or expanded on the scaffold.

Reference is again made to Figs. 1-14. It is to be noted that, although the figures show the implant (e.g., an implantable element of the sensor) as being generally tubular, and the cavity of the implant as being shaped as a lumen, the scope of the invention includes implants of other shapes, and implants having cavities of other shapes. Also, for some applications, the sensor has two portions: (1) an implantable element, and (2) an extracorporeal element in communication with the implantable element. Reference is again made to Figs. 1-14. The analyte detected by the implants may include another analyte in addition or alternatively to glucose. For example, the analyte may include a hormone or a metal ion. Furthermore, the techniques described herein may be used to augment (e.g., to protect) implants that do not contain cells other than the protector cells. For example, the techniques may be used to augment (1) implants that detect a parameter of the subject via an electrochemical reaction, (2) implants that detect an electrical parameter of the subject, and/or (3) implants that apply an electrical current to the body of the subject. For such applications, the interface surface of the implants may comprise one or more electrodes (i.e., is configured to provide electrical communication between the sensor and the body of the subject). Reference is again made to Figs. 1-14. As described hereinabove, for some applications the protector cells comprise MSC. For some applications, the MSC are derived from a human tissue such as (but not limited to) bone marrow, placental tissue (e.g., blood), cord tissue (e.g., blood), Wharton's jelly, dental pulp, and/or adipose tissue. Typically, MSC are purified by selecting for cells that are plastic-adherent, express CD73, CD90, and CD 105, and lack cell-surface expression of (1) CD34, (2) CD45, (3) HLA-DR, (4) CD14 or CDl lb, and (5) CD79alpha or CD19. That is, the MSC are defined as such by these characteristics. Alternatively or additionally, MSC may be purified by selecting for cells that express CD49a, CD56, CD63, Cd73, CD105, CD106, CD140b, CD271, MSCA-1, Stro-1, SSEA4 and CD 146. That is, the MSC are defined as such by these alternative characteristics.

The MSC may be further purified by selecting for cells that express CD200, CD271, CD274 and/or CD276 (e.g., by selecting for cell-surface expression of at least two of these molecules). It is to be noted that in this application, "at least two of these molecules" means at least two of these molecule types, for example, CD200 and CD276, rather than at least two individual molecules. This comment applies as well to all similar references in the application, whether for two molecules, eight molecules, or any other number. Alternatively or additionally, the MSC may be further purified by selecting for cells that express CD49a, CD56, CD63, Cd73, CD105, Cdl06, CD140b, CD271, MSCA- 1, Stro-1, SSEA4 and/or CD146 (e.g., by selecting for cell-surface expression of at least eight of these molecules). Alternatively or additionally, the MSC may be further purified by selecting for cells that do not express, or express only low levels of CD40, CD80 and CD86.

Alternatively or additionally, the MSC may be further purified by selecting for cells that do not express, or express only low levels of Major Histocompatibility Complex (MHC) class I molecules and MHC class II molecules. As described hereinabove, for some applications the protector cells comprise DF.

For some applications, the DF are derived from a human tissue such as foreskin and/or a dermatome section. Typically, DF are purified by selecting for cells that are plastic- adherent, express CD73 and/or CD54, and lack cell-surface expression of CD45.

As described hereinabove, for some applications the protector cells comprise regulatory T cells. For some applications, the regulatory T cells are selected on the basis of cell-surface expression of CD4 and CD25, and low or absent expression of CD 127 (CD4(+)CD25(+)CD127(low/-)). It is hypothesized that such cells express the FoxP3 transcription factor, and that this selection of the regulatory T cells based on their expression of cell-surface markers facilitates selection of FoxP3+ cells while retaining the viability of the cells.

For some applications, the protector cells are autologous (e.g., are derived from previously-obtained cells of the subject). For some applications, the protector cells are allogeneic (e.g., are derived from a donor, or from a cell bank). For some applications in which the protector cells are autologous, the protector-cell compartment of the implant is not covered in a selectively -permeable covering. For example, for such applications in which the protector-cell compartment comprises a hydrogel, the hydrogel may be the exterior of the implant, such that, after implantation, it is in direct contact with tissue of the subject. For some such applications a selectively-permeable covering or divider separates the protector-cell compartment from the producer-cell compartment. Techniques described herein may be practiced in combination with techniques described in one or more of the following references, which are incorporated herein by reference: US Patent Application Publication 2010/0160749 to Gross et al.; US Patent Application Publication 2010/0202966 to Gross et al.; US Patent Application Publication 2013/0006069 to Gil et al.; US Patent Application Publication 2011/0251471 to Gross et al.; US Patent Application Publication 2012/0059232 to Gross et al.;

US Patent 7,951,357 to Gross et al.;

PCT Patent Application Publication WO/2006/006166 to Gross et al.;

PCT Patent Application Publication WO/2007/110867 to Gross et al.;

PCT Patent Application Publication WO/2010/073249 to Gross et al.; PCT Patent Application Publication WO/2013/001532 to Gil et al.; and

PCT Patent Application PCT/IB2013/061368, to Brill et al., entitled "Apparatus for facilitating cell growth in an implantable sensor", filed December 27, 2013.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.

Claims

1. Apparatus comprising an implant, the implant comprising:

a structure comprising a wall that is shaped to define a cavity;

2. The apparatus according to claim 1, wherein the MSC comprise MSC that have been derived from a human tissue selected from the group consisting of: bone marrow, placental blood, cord blood, Wharton's jelly, dental pulp and adipose tissue.

3. The apparatus according to claim 1, wherein the MSC have been selected based on a cell-surface presence of CD73, CD90 and CD105.

4. The apparatus according to claim 3, wherein the MSC have been selected based on a cell-surface absence of (1) CD34; (2) CD45; (3) HLA-DR; (4) at least one marker selected from the group consisting of: CD14 and CDl lb; and (5) at least one marker selected from the group consisting of: CD79alpha and CD19.

5. The apparatus according to claim 3, wherein the MSC have been selected based on a cell-surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276.

6. The apparatus according to claim 3, wherein the MSC have been selected based on a cell-surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD106, CD140b, CD271, MSCA-1, Stro-1, SSEA4 and CD 146.

7. The apparatus according to claim 3, wherein the MSC have been selected based on a cell-surface absence of CD40, CD80 and CD86.

8. The apparatus according to claim 1, wherein the MSC have low cell-surface levels of Major Histocompatibility Complex class I molecules and Major Histocompatibility Complex class II molecules.

9. The apparatus according to any one of claims 1-8, wherein the MSC are disposed on an outside of the structure.

10. The apparatus according to any one of claims 1-8, wherein the implant comprises a hydrogel disposed within the cavity, and the producer cells are suspended within the hydrogel.

11. The apparatus according to any one of claims 1-8, wherein the implant comprises a hydrogel, and the MSC are suspended within the hydrogel.

12. The apparatus according to claim 11, wherein the hydrogel and the MSC are disposed within the cavity.

13. The apparatus according to claim 11, wherein the hydrogel and the MSC are disposed on an outside of the structure.

14. The apparatus according to any one of claims 1-8, wherein the wall is selectively permeable and has a molecular weight cut-off of 10-100 kDa.

15. The apparatus according to any one of claims 1-8, wherein the wall is selectively permeable and has a molecular weight cut-off of 10-50 kDa.

16. The apparatus according to any one of claims 1-8, wherein the producer cells are disposed in a first compartment within the cavity, and the MSC are disposed in a second compartment within the cavity.

17. The apparatus according to claim 16, wherein the second compartment is disposed between the first compartment and the circumferential wall.

18. The apparatus according to claim 17, wherein the second compartment circumscribes the first compartment.

19. The apparatus according to claim 16, wherein the producer cells are interspersed with the MSC.

20. The apparatus according to any one of claims 1-8, wherein the structure is tubular, and the wall is a circumferential wall that circumscribes the cavity.

21. The apparatus according to any one of claims 1-8, wherein the structure is tubular, the wall is a circumferential wall that shapes the cavity as a lumen, and the lumen has a diameter of 0.5-1.5 mm.

22. The apparatus according to any one of claims 1-8, wherein the structure is tubular, the wall is a circumferential wall that shapes the cavity as a lumen, and the lumen has a diameter of up to 5 mm.

23. The apparatus according to any one of claims 1-8, wherein the wall comprises modified polyethersulfone.

24. The apparatus according to any one of claims 1-8, wherein the implant further comprises a coating, disposed on an outer surface of the wall, and comprising platelet material.

25. The apparatus according to claim 24, wherein the coating comprises platelet-rich plasma.

26. The apparatus according to claim 24, wherein the coating comprises platelet microparticles.

27. The apparatus according to claim 24, wherein the coating is water-permeable.

28. The apparatus according to claim 24, wherein the coating comprises a hydrogel.

29. The apparatus according to claim 28, wherein the coating comprises polyethylene glycol.

30. The apparatus according to claim 28, wherein the coating comprises alginate.

31. The apparatus according to claim 24, wherein the coating has a thickness of 50-700 microns.

32. The apparatus according to claim 31, wherein the coating has a thickness of 100- 500 microns.

33. A method, comprising:

providing a structure having a wall that is shaped to define a cavity;

34. The method according to claim 33, wherein introducing the cell suspension of MSC comprises introducing a cell suspension of MSC that have been derived from a human tissue selected from the group consisting of: bone marrow, placental blood, cord blood, Wharton's jelly, dental pulp and adipose tissue.

35. The method according to claim 33, wherein introducing the cell suspension of MSC comprises introducing a cell suspension of selected MSC that have been selected based on a cell-surface presence of CD73, CD90 and CD105.

36. The method according to claim 35, further comprising preparing the selected MSC by selecting the selected MSC based on the cell-surface presence of CD73, CD90, and

CD105.

37. The method according to claim 35, wherein introducing the cell suspension of selected MSC comprises introducing a cell suspension of selected MSC that have been selected based on a cell-surface absence of (1) CD34; (2) CD45; (3) HLA-DR; (4) at least one marker selected from the group consisting of: CD 14 and CD l ib; and (5) at least one marker selected from the group consisting of: CD79alpha and CD19.

38. The method according to claim 37, further comprising preparing the selected MSC by selecting the selected MSC based on the cell-surface absence of (1) CD34; (2) CD45; (3) HLA-DR; (4) at least one marker selected from the group consisting of: CD 14 and CDl lb; and (5) at least one marker selected from the group consisting of: CD79alpha and CD19.

39. The method according to claim 35, wherein introducing the cell suspension of selected MSC comprises introducing a cell suspension of selected MSC that have been selected based on a cell-surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276.

40. The method according to claim 39, further comprising preparing the selected MSC by selecting the selected MSC based on the cell-surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276.

41. The method according to claim 35, wherein introducing the cell suspension of selected MSC comprises introducing a cell suspension of selected MSC that have been selected based on a cell- surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD106, CD140b, CD271, MSCA-1, Stro-1, SSEA4 and CD 146.

42. The method according to claim 41, further comprising preparing the selected MSC by selecting the selected MSC based on the cell-surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD 106, CD 140b, CD271, MSCA-1, Stro-1, SSEA4 and CD 146.

43. The method according to claim 35, wherein introducing the cell suspension of selected MSC comprises introducing a cell suspension of selected MSC that have been selected based on a cell-surface absence of CD40, CD80 and CD86.

44. The method according to claim 43, further comprising preparing the selected MSC by selecting the selected MSC based on the cell-surface absence of CD40, CD80 and CD86.

45. The method according to claim 35, wherein introducing the cell suspension of selected MSC comprises introducing a cell suspension of selected MSC that have low cell- surface levels of Major Histocompatibility Complex class I molecules and Major Histocompatibility Complex class II molecules.

46. The method according to claim 45, further comprising preparing the selected MSC by selecting the selected MSC based on the low cell-surface levels of Major Histocompatibility Complex class I molecules and Major Histocompatibility Complex class II molecules.

47. The method according to any one of claims 33-46, wherein the cell suspension is a cell suspension of MSC and producer cells, the producer cells containing exogenous genetic material that encodes an extracellular sensor molecule, and introducing the cell suspension comprises introducing the cell suspension of MSC and producer cells.

48. The method according to any one of claims 33-46, wherein:

the structure is tubular,

the wall shapes the cavity as a lumen having a diameter of 0.5-1.5 mm, and introducing the cell suspension comprises introducing the cell suspension into the lumen.

49. The method according to any one of claims 33-46, wherein:

the structure is tubular,

the wall shapes the cavity as a lumen having a diameter of up to 5 mm, and introducing the cell suspension comprises introducing the cell suspension into the lumen.

50. The method according to any one of claims 33-46, wherein the cell suspension is a suspension of MSC in a hydrocolloid solution, introducing the cell suspension comprises introducing the suspension of MSC that is in the hydrocolloid solution, and setting the cell suspension comprises setting the suspension of MSC that is in the hydrocolloid solution

51. The method according to any one of claims 33-46, wherein the wall is selectively permeable and has a molecular weight cut-off of 10-100 kDa, and providing the tubular structure comprises providing the tubular structure that has the selectively-permeable wall.

52. The method according to any one of claims 33-46, wherein the wall is selectively permeable and has a molecular weight cut-off of 10-50 kDa, and providing the tubular structure comprises providing the tubular structure that has the selectively-permeable wall.

53. The method according to any one of claims 33-46, wherein the hydrocolloid solution includes alginate, the setting solution contains a divalent cation salt, introducing the cell suspension of MSC in the hydrocolloid solution comprises introducing the cell suspension of MSC in the hydrocolloid solution that includes alginate, and setting the cell suspension by placing the structure in a setting solution comprises setting the cell suspension by placing the structure in the setting solution that contains the divalent cation salt.

54. The method according to any one of claims 33-46, wherein the structure is a tubular structure, the wall circumscribes the cavity and shapes the cavity as a lumen, and introducing the cell suspension comprises introducing the cell suspension into the lumen.

55. The method according to claim 54, wherein introducing the cell suspension into the lumen comprises introducing the cell suspension into the lumen via an open proximal end of the lumen, and the method further comprises plugging the open end of the lumen subsequently to the step of introducing and prior to the step of setting.

56. The method according to any one of claims 33-46, wherein the tubular structure is coupled to an optical fiber that plugs and extends away from a distal end of the lumen, and providing the tubular structure comprises providing the tubular structure that is coupled to the optical fiber that plugs and extends away from the distal end of the lumen.

57. The method according to any one of claims 33-46, wherein:

the cell suspension is a first cell suspension,

the method further comprises prior to introducing the first cell suspension, introducing into the cavity a core comprising producer cells in a gel, the producer cells containing exogenous genetic material that encodes an extracellular sensor molecule, and introducing the first cell suspension into the cavity comprises introducing the first cell suspension into the cavity such that at least part of the first cell suspension is disposed between the core and the wall.

58. The method according to any one of claims 33-46, wherein introducing the cell suspension comprises advancing a tube through an open proximal end of the cavity toward a distal end of the cavity, and injecting the cell suspension into the cavity while progressively withdrawing the tube from the cavity.

59. The method according to any one of claims 33-46, wherein the cell suspension is a first cell suspension, and the method further comprises:

introducing a second cell suspension into the cavity, the second cell suspension being a suspension of producer cells in a hydrocolloid solution, the producer cells containing exogenous genetic material that encodes an extracellular sensor molecule, and subsequently, setting the second cell suspension.

60. The method according to claim 59, wherein:

the structure includes a selectively-permeable divider within the cavity, introducing the first cell suspension into the cavity comprises introducing the first cell suspension on a first side of the divider, and

introducing the second cell suspension into the cavity comprises introducing the second cell suspension on a second side of the divider.

61. The method according to claim 60, wherein introducing the second cell suspension comprises introducing the second cell suspension after the step of setting the first cell suspension.

62. The method according to claim 60, wherein introducing the first cell suspension comprises introducing the first cell suspension after the step of setting the second cell suspension.

63. The method according to claim 60, wherein introducing the second cell suspension comprises introducing the second cell suspension subsequently to the step of introducing the first cell suspension, and prior to the step of setting the first cell suspension.

64. The method according to claim 59, wherein:

setting the first cell suspension comprises setting the first cell suspension while a core is disposed within the cavity,

the method further comprises removing the core from the cavity after the step of setting the first cell suspension, and introducing the second cell suspension into the lumen comprises introducing the second cell suspension into a space that remains within the set first cell suspension as a result of the removal of the core.

65. Apparatus, configured to be implanted in a body of a subject, the apparatus comprising:

a sensor, configured to detect a parameter of the subject;

a plurality of cells selected from the group consisting of: mesenchymal stem cells (MSC), dermal fibroblasts (DF), and fusion cells comprising MSC fused with another cell type, the selected cells being immobilized with respect to at least one element selected from the group consisting of: the sensor and the interface surface, and being positioned to modulate a cellular function of the body of the subject with respect to the at least one selected element,

the apparatus being implantable in the body of the subject.

66. The apparatus according to claim 65, wherein the selected cells comprise the DF.

67. The apparatus according to claim 65, wherein the selected cells are autologous to the subject.

68. The apparatus according to claim 65, wherein the selected cells are allogeneic to the subject.

69. The apparatus according to claim 65, wherein the interface surface comprises a substance-exchange surface, configured to facilitate movement of a body substance through the substance-exchange surface to the sensor.

70. The apparatus according to claim 65, wherein the interface surface is configured to provide chemical communication between the sensor and the body.

71. The apparatus according to claim 65, wherein the selected cells comprise the fusion cells.

72. The apparatus according to any one of claims 65-71, wherein the selected cells comprise the MSC.

73. The apparatus according to claim 72, wherein the MSC comprise MSC that have been derived from a human tissue selected from the group consisting of: bone marrow, placental blood, cord blood, Wharton's jelly, dental pulp and adipose tissue.

74. The apparatus according to claim 73, wherein the MSC have been selected based on a cell-surface presence of CD73, CD90 and CD105.

75. The apparatus according to claim 74, wherein the MSC have been selected based on a cell-surface absence of (1) CD34; (2) CD45; (3) HLA-DR; (4) at least one marker selected from the group consisting of: CD 14 and CD l ib; and (5) at least one marker selected from the group consisting of: CD79alpha and CD19.

76. The apparatus according to claim 74, wherein the MSC have been selected based on a cell-surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276.

77. The apparatus according to claim 74, wherein the MSC have been selected based on a cell- surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD106, CD140b, CD271, MSCA-1, Stro-1, SSEA4 and CD 146.

78. The apparatus according to claim 74, wherein the MSC have been selected based on a cell-surface absence of CD40, CD80 and CD86.

79. The apparatus according to claim 73, wherein the MSC have low cell-surface levels of Major Histocompatibility Complex class I molecules and Major

Histocompatibility Complex class II molecules.

80. The apparatus according to any one of claims 65-71, wherein the sensor is configured to detect an analyte of the body of the subject, and the interface surface is configured to provide the communication by facilitating movement of the analyte through the interface surface.

81. The apparatus according to claim 80, wherein the apparatus is configured to synthesize a sensor molecule, configured to bind the analyte.

82. The apparatus according to claim 81, wherein the selected cells are configured to express the sensor molecule.

83. The apparatus according to claim 81, wherein the selected cells contain exogenous genetic material that encodes the sensor molecule.

84. The apparatus according to claim 81, wherein the plurality of selected cells comprises a first plurality of cells, and the apparatus further comprises a second plurality of cells, configured to express the sensor molecule.

85. The apparatus according to claim 84, wherein the first plurality of cells and the second plurality of cells are interspersed with each other.

86. The apparatus according to claim 85, wherein the first plurality of cells is coupled to a first plurality of carriers, the second plurality of cells is coupled to a second plurality of carriers, and the first and second pluralities of carriers are interspersed with each other.

87. The apparatus according to claim 84, wherein the first plurality of cells is disposed in a first cell compartment of the apparatus, and the second plurality of cells is disposed in a second cell compartment of the apparatus.

88. The apparatus according to claim 87, wherein the second cell compartment at least partly surrounds the first cell compartment.

89. The apparatus according to claim 87, wherein at least one of the compartments contains a hydrogel.

90. The apparatus according to claim 87, wherein at least one of the compartments contains a three-dimensional scaffold to which the respective plurality cells is coupled.

91. The apparatus according to claim 87, further comprising a selectively-permeable barrier that surrounds at least one cell compartment selected from the group consisting of: the first cell compartment and the second cell compartment.

92. The apparatus according to claim 80, wherein the sensor comprises a chamber containing a sensor molecule, configured to bind the analyte.

93. The apparatus according to claim 92, wherein the selected cells are disposed at least in part around an outer surface of the chamber.

94. The apparatus according to claim 92, wherein the sensor comprises circuitry in optical communication with the chamber.

95. The apparatus according to claim 94, wherein the sensor is configured to detect the analyte by detecting light from the chamber.

96. Apparatus, configured to be implanted in a body of a subject, the apparatus comprising: a sensor, configured to detect a parameter of the subject;

the apparatus being implantable in the body of the subject.

97. Apparatus, comprising:

a tubular structure comprising a circumferential wall that (i) defines a lumen, and

(ii) has a molecular weight cut-off of 10-100 kDa;

a hydrogel, disposed within the lumen;

a plurality of producer cells, suspended within the hydrogel, the producer cells containing exogenous genetic material that encodes an extracellular molecule; and

a plurality of regulatory T cells, suspended within the hydrogel.

98. A method, comprising:

subsequently, setting the cell suspension by placing the tubular structure in a setting solution.

99. A method, comprising:

extracting a cell population from the selected human tissue;

enriching the cell population based on cell-surface expression of CD73, CD90, and CD105; and

subsequently, coupling the enriched cell population to an implant.

100. The method according to claim 99, wherein enriching the cell population comprises enriching the cell population based on cell-surface absence of (1) CD34; (2) CD45; (3) HLA-DR; (4) at least one marker selected from the group consisting of: CD14 and CD l ib; and (5) at least one marker selected from the group consisting of: CD79alpha and CD19.

101. The method according to claim 99, wherein enriching the cell population comprises enriching the cell population based on cell- surface presence of at least two molecules selected from the group consisting of: CD200, CD271, CD274 and CD276.

102. The method according to claim 99, wherein enriching the cell population comprises enriching the cell population based on cell-surface presence of at least eight molecules selected from the group consisting of: CD49a, CD56, CD63, CD73, CD105, CD 106, CD 140b, CD271, MSCA-1, Stro-1, SSEA4 and CD 146.

103. The method according to claim 99, wherein enriching the cell population comprises enriching the cell population based on cell-surface absence of CD40, CD80 and CD86.

104. The method according to any one of claims 99-103, wherein enriching the cell population comprises enriching the cell population based on low cell-surface expression of

Major Histocompatibility Complex class I molecules and Major Histocompatibility Complex class II molecules.

105. A method, comprising:

providing a structure having a wall that is shaped to define a cavity;

106. Apparatus for use with a subject, the apparatus comprising a sensor, the sensor: being configured to detect a parameter of the subject,

comprising an implantable element, implantable in the subject, and comprising: an interface surface, configured to provide communication between the implant and the body; and

a plurality of cells selected from the group consisting of: mesenchymal stem cells (MSC), dermal fibroblasts (DF), and fusion cells comprising MSC fused with another cell type, the selected cells being immobilized with respect to the implantable element, and being positioned to modulate a cellular function of the body of the subject with respect to the implantable element.

107. Apparatus for use with a subject, the apparatus comprising:

an implant, comprising a wall having an external surface; and

a coating, disposed on the external surface, and comprising platelet material.

108. The apparatus according to claim 107, wherein the coating comprises platelet-rich plasma.

109. The apparatus according to claim 107, wherein the coating comprises platelet microparticles.

110. The apparatus according to any one of claims 107-109, wherein the coating comprises a hydrogel.

111. The apparatus according to claim 110, wherein the coating comprises polyethylene glycol.

112. The apparatus according to claim 110, wherein the coating comprises alginate.

113. The apparatus according to any one of claims 107-109, wherein the coating has a thickness of 50-700 microns.

114. The apparatus according to claim 113, wherein the coating has a thickness of 100- 500 microns.

115. The apparatus according to any one of claims 107-109, wherein the coating is water-permeable .

116. The apparatus according to claim 115, wherein at least a portion of the wall is selectively-permeable, and the wall is shaped to define a cavity.

117. The apparatus according to claim 116, wherein the coating is disposed at least on the external surface of the portion of the wall.

118. The apparatus according to claim 116, wherein the implant comprises living cells disposed within the cavity.

119. A method, comprising:

providing platelet-rich plasma (PRP);

preparing a mixture by mixing a hydrogel precursor with the PRP; and subsequently, forming a hydrogel by crosslinking the hydrogel precursor.

120. The method according to claim 119, further comprising, prior to forming the hydrogel, coating the mixture onto an external surface of an implant.

121. The method according to any one of claims 119-120, wherein the hydrogel precursor comprises polyethylene glycol (PEG), and mixing the hydrogel precursor with the PRP comprises mixing the PEG with the PRP.

122. The method according to any one of claims 119-120, wherein the hydrogel precursor comprises alginate, and mixing the hydrogel precursor with the PRP comprises mixing the alginate with the PRP.