JP4541336B2 - Arterial blood vessel for small arteries using fibroin thread - Google Patents

Description

  The present invention relates to a small-diameter artificial blood vessel using fibroin yarn and a method for producing the small-diameter artificial blood vessel.

  There are great public expectations for artificial blood vessels in the medical field. This artificial blood vessel has already reached a certain practical level for large-diameter artificial blood vessels. However, a small-diameter artificial blood vessel having a diameter of 5.0 mm or less can be obtained by using polyethylene terephthalate (for example, trade name: Dacron) or PTFE (polytetrafluoroethylene), which are typical artificial materials that are used without problems in large-diameter artificial blood vessels. When this is used, thrombotic occlusion occurs frequently and is still at a practically difficult level from the viewpoint of patency. Here, patency refers to the property that, after transplanting an artificial blood vessel, the lumen of the artificial blood vessel remains open without being blocked. Therefore, when performing revascularization of small-diameter blood vessels (such as coronary arteries and peripheral blood vessels) with a diameter of 5.0 mm or less, conventional artificial blood vessels with small diameters are used because of poor patency. Rather, they often use their own blood vessels (such as the internal thoracic artery or the great saphenous vein).

  However, the collection of own blood vessels is not only a burden on the patient, but the own blood vessels may not be used for revascularization. In particular, in the case of arterial grafts, there are many cases in which re-operation is impossible due to the limited number of blood vessels that can be used. In particular, the left and right internal thoracic arteries, gastroepiploic artery, and radial artery used for coronary artery bypass surgery can be acquired only once in the lifetime of the patient. From this point of view, there is a great expectation for an artificial blood vessel that can be supplied without depending on its own blood vessel, and the development of a small-diameter artificial blood vessel with good patency has been desired.

  In the case of surgery for congenital heart disease in children, it is necessary to change the size of the transplanted blood vessel as the patient grows, that is, to remodel. In the case of using a substitute blood vessel made of a conventional artificial material, re-operation for this remodeling is necessary. Therefore, in the case of such a pediatric patient, revascularization using an own blood vessel is currently performed while being restricted as described above. In recent years, even in the case of pediatric patients who need such remodeling, artificial blood vessels made of bioabsorbable materials can be used instead of their own blood vessels, even if they are artificial blood vessels. From this point of view, bioabsorbable artificial blood vessels such as PGA (polyglycolic acid) and PLA (polylactic acid) materials have been developed.

  However, such bioabsorbable artificial blood vessels can be clinically applied in low-pressure systems such as pulmonary arteries and veins, but in high-pressure systems such as systemic arteries, they are durable due to bioabsorbability. The problem is occurring. For this reason, it has high strength and the period until absorption in the living body is reasonably long, so there is no problem in durability, that is, it has moderate living ability and can be used even in high-pressure systems such as arteries of the systemic circulation system. Development of an artificial blood vessel has been desired.

As an attempt to produce a conventional artificial blood vessel-like structure that has left the above-mentioned problems unsolved, for example, there is a string structure described in Patent Document 1. Patent Document 1 describes a kite string structure formed by winding a kite string around a mandrel according to the braided string creation principle and a manufacturing method thereof. In this kite structure, it is described as a preferred embodiment that the kite string is glued with sericin to secure strength, and further, synthetic fibers or metal fibers are mixed. However, this string structure is a structure pursuing strength, and synthetic fibers and metal fibers used by mixing fibers have problems in terms of bioabsorbability when used as small-diameter artificial blood vessels. . Furthermore, the patency structure of this silk thread structure has not been studied, and it cannot be expected that it can be used as a small-diameter artificial blood vessel.
JP 2004-173722 A

  The present invention has good patency, high strength, a period of time until absorption in a living body is reasonably long, and does not cause a problem in durability. An object of the present invention is to provide a small-diameter artificial blood vessel that can be used in a high-pressure system such as the above, and a method for producing the small-diameter artificial blood vessel.

  The present inventors, when actually used as a small-diameter artificial blood vessel, have a good patency, have a strength that can be used even in a high-pressure system, and appropriate bioabsorbability, and a small-diameter artificial blood vessel For the purpose of obtaining a manufacturing method, an animal experiment in which a small-diameter artificial blood vessel is actually produced and transplanted into an experimental animal and observed over time has been conducted.

As a result, the present inventors are able to
A process of braiding fibroin yarn in multiple layers to form a multilayer cylindrical structure;
Coating a multi-layered cylindrical structure with fibroin;
And a small-diameter artificial blood vessel produced by coating the fibroin with a multi-layered cylindrical structure formed by braiding fibroin yarns in multiple layers. , Found to be achieved by.

  Surprisingly, the small-diameter artificial blood vessel of the present invention was anastomosed to the rat abdominal aorta as a small-diameter artificial blood vessel having a diameter of 1.5 mm, and confirmed long-term patency for 4 weeks to 32 weeks or more.

Therefore, the present invention includes the following [1] to [17].
[1] A small-diameter artificial blood vessel in which a multilayered tubular structure formed by braiding fibroin yarns in multiple layers is coated with fibroin.
[2] The small-diameter artificial blood vessel according to [1], wherein the multilayer is three layers.
[3] The small-diameter artificial blood vessel according to [1] or [2], which has an inner diameter in the range of 1.0 to 5.0 mm.
[4] The small-diameter artificial blood vessel according to any one of [1] to [3], which has an vascularization ability of an artificial blood vessel.
[5] The small-diameter artificial blood vessel according to any one of [1] to [4], which has long-term patency.
[6] The small-diameter artificial blood vessel according to any one of [1] to [5], which can be used in arteries of the systemic circulation system.
[7] The yarn according to any one of [1] to [6], wherein a warp yarn is used as the fibroin yarn, and the formed multilayer cylindrical structure is coated with fibroin after sericin is removed. Small-diameter artificial blood vessels.
[8] A step of braiding fibroin yarn in multiple layers to form a multilayer cylindrical structure;
Coating a multi-layered cylindrical structure with fibroin;
A method for producing a small-diameter artificial blood vessel, comprising:
[9] The method according to [8], wherein the multilayer is three layers.
[10] The method according to [8] or [9], wherein the small-diameter artificial blood vessel has an inner diameter in the range of 1.0 to 5.0 mm.
[11] The step of coating the multi-layered cylindrical structure with fibroin comprises:
The method according to any one of [8] to [10], wherein the method is performed by immersing the multilayer cylindrical structure in a fibroin solution.
[12] The step of braiding the fibroin yarn in multiple layers to form a multilayer cylindrical structure,
The method according to any one of [8] to [11], wherein the method is performed by using a mandrel having a diameter of 1.0 to 5.0 mm.
[13] The method according to any one of [8] to [12], wherein the fibroin solution is obtained by dissolving fibroin in an aqueous lithium bromide solution.
[14] The method according to any one of [8] to [13], wherein the fibroin solution is dialyzed after dissolving fibroin in an aqueous lithium bromide solution.
[15] The method according to any one of [8] to [14], wherein the fibroin solution has a fibroin concentration of 1 to 4%.
[16] The step of braiding the fibroin yarn into multiple layers to form a multilayered tubular structure is performed using the kite yarn as the fibroin yarn, and after the step,
Removing sericin from the multi-layered cylindrical structure formed;
The method according to any one of [8] to [15], wherein a step of coating a multi-layered cylindrical structure with fibroin is performed after the step.
[17] A small-diameter artificial blood vessel produced by the method according to any one of [8] to [16].

The present invention also includes the following [18] to [20].
[18] A method for performing revascularization using the small-diameter artificial blood vessel according to any one of [1] to [7] and [17].
[19] A method for inducing vascularization using the small-diameter artificial blood vessel according to any one of [1] to [7] and [17].
[20] An agent for inducing migration of endothelial cells and / or smooth muscle cells, comprising the small-diameter artificial blood vessel according to any one of [1] to [7] and [17].
[21] An angiogenesis inducer comprising the small-diameter artificial blood vessel according to any one of [1] to [7] and [17].

  Although the small-diameter artificial blood vessel of the present invention is a small-diameter artificial blood vessel having a diameter of 5.0 mm or less, it enables long-term patency without causing thrombotic occlusion. This long-term patency is considered to be brought about by the antithrombogenicity of the small-diameter artificial blood vessel of the present invention and vascularization by migration of endothelial cells and smooth muscle cells into the small-diameter artificial blood vessel lumen. Therefore, it can be expected to maintain a stable patency for a long time.

  And, if the small-diameter artificial blood vessel of the present invention is used, revascularization can be performed without relying on the own blood vessel, and the small-diameter artificial blood vessel of the present invention can no longer collect the own blood vessel. It greatly contributes to the lifesaving of the patient who has lost.

  Further, since the small-diameter artificial blood vessel of the present invention has moderate bioabsorbability, it can be suitably used in revascularization for pediatric patients in which remodeling due to growth is a problem. It has become. At the same time, since the small-diameter artificial blood vessel of the present invention has sufficient strength and durability due to appropriate bioabsorbability, it is suitable for a high-pressure circulatory-resistant arterial system that is difficult with conventional bioabsorbable materials. Can be used.

  The present invention will be described in further detail below while exemplifying a method for manufacturing a small-diameter artificial blood vessel according to the present invention. The present invention is not limited to the following examples.

  The small-diameter artificial blood vessel according to the present invention is a small-diameter artificial blood vessel in which a multi-layered cylindrical structure formed by fibrin yarn braided in multiple layers is coated with fibroin.

This small-diameter artificial blood vessel is produced by the following manufacturing method according to the present invention:
A process of braiding fibroin yarn in multiple layers to form a multilayer cylindrical structure;
Coating a multi-layered cylindrical structure with fibroin;
It can be manufactured by a method for manufacturing a small-diameter artificial blood vessel.

  The above-mentioned multilayer is preferably 3 layers or 4 layers, and particularly preferably 3 layers. When this is made into one layer without making it into a multilayer, the intensity | strength which can be used by a high voltage | pressure system cannot be obtained. If there are many multilayer layers, the strength is further improved, but the flexibility required for the artificial blood vessel is inferior, and the period of bioabsorption is too long.

  The small-diameter artificial blood vessel of the present invention has long-term patency. In the present invention, long-term patency means a sufficient period of time after transplantation of an artificial blood vessel (for example, several weeks or more for a rat and several months or more for a human), and the lumen of the artificial blood vessel remains open without being blocked. A certain property.

  In the production method of the present invention, the step of coating the multilayer cylindrical structure with fibroin can be performed by immersing the multilayer cylindrical structure in a fibroin solution. This fibroin solution is preferably one in which fibroin is dissolved in an aqueous lithium bromide solution, and more preferably one that is dialyzed after dissolving fibroin in an aqueous lithium bromide solution. This fibroin solution can generally be used with a fibroin concentration in the range of 0.5-8%, preferably in the range of 1-4%, particularly preferably in the range of 1-3%. Can be used. In general, the dipping time can be appropriately selected from the range of 1 second to 120 seconds, but is preferably in the range of 1 to 60 seconds, particularly preferably in the range of 1 to 30 seconds.

  The excellent characteristics of the small-diameter artificial blood vessel of the present invention are considered to be brought about by the fact that a multi-layered cylindrical structure formed by braiding fibroin yarns in multiple layers is coated with fibroin. This multi-layered, particularly preferably three-layered tubular structure is coated with fibroin to provide the ability to induce migration and colonization of vascular endothelial cells and / or smooth muscle cells as shown in the present invention. It is considered that the bioabsorbability is maintained to be moderate, and that the artificial blood vessel is changed so as to be replaced with the same blood vessel as the original blood vessel (vascularization). In addition, with this fibroin coating, the three-layered cylindrical structure has a mesh that is properly fixed, the overall shape is properly maintained, and the end of the cylindrical structure is not frayed. At the same time, it is considered that the condition after transplantation is also stabilized. In particular, the effect of stabilizing mainly the shape is a preferred embodiment of the present invention, in which a warp yarn is used as a fibroin yarn, and the formed multi-layered cylindrical structure is obtained by removing sericin. It is particularly effective.

  The inner diameter of the small-diameter artificial blood vessel is generally in the range of 1.0 to 5.0 mm, preferably in the range of 1.0 to 4.0 mm, more preferably in the range of 1.0 to 3.0 mm, particularly preferably 1.0. It can be in the range of ~ 2.0 mm. The small-diameter artificial blood vessel of the present invention has an advantageous feature that it has sufficient patency even when it has such a small inner diameter. This inner diameter can be set to a desired inner diameter in the surgical procedure, and can be smaller than this range. However, the smaller the inner diameter is, the more difficult the end-to-end anastomosis is.

  In addition, when the material used for the conventional large-diameter artificial blood vessel is used, the contribution of the present invention is that the artificial blood vessel has a small diameter that cannot be realized as a practical one. However, since the excellent characteristics of the small-diameter artificial blood vessel of the present invention are exhibited even when the large-diameter is set, the inner diameter of the small-diameter artificial blood vessel is set to a value larger than the above range. Is also possible.

  In order to obtain such an inner diameter, the step of forming a multilayered cylindrical structure by braiding fibroin yarns in multiple layers can be performed by using a mandrel having a diameter of 1.0 to 5.0 mm. . The diameter of the mandrel is generally in the range of 1.0 to 5.0 mm, preferably in the range of 1.0 to 4.0 mm, more preferably in the range of 1.0 to 3.0 mm, depending on the desired inner diameter. It can be preferable. Braid knitting can be performed by a known method and apparatus.

  In the present invention, a particularly advantageous effect is achieved by the combination of the above-mentioned multilayer structure, preferably 3 layers or 4 layers, particularly preferably 3 layers, and coating with fibroin. In other words, the initial blood leakage that cannot be sufficiently prevented by simply having a multilayer structure is prevented by the coating of fibroin, and the gap between the layers of the multilayer structure is prevented by the adhesive effect of the coating of fibroin, Furthermore, antithrombogenicity is imparted by fibroin.

  The small-diameter artificial blood vessel of the present invention has a very effective vascularization ability of an artificial blood vessel. This vascularization ability is exerted over the entire cross section of the artificial blood vessel, but is particularly favorably exhibited in the lumen of the artificial blood vessel. This ability to induce vascularization, that is, the ability to induce the artificial blood vessel to change in the same manner as the original self blood vessel, is induced by the ability to induce migration of endothelial cells and / or smooth muscle cells of the small-diameter artificial blood vessel of the present invention. It is thought that it is. From this point, it can be used as an agent for inducing migration of endothelial cells and / or smooth muscle cells, and further can be used as an agent for inducing angiogenesis.

  The small-diameter artificial blood vessel of the present invention can be used in arterial circulatory arteries, that is, has sufficient strength to enable this.

  In a preferred embodiment, the small-diameter artificial blood vessel of the present invention is one in which a kite yarn is used as a fibroin yarn, and the formed multilayered cylindrical structure is coated with fibroin after sericin is removed. . Use of the yarn yarn in this way is advantageous in that it is easy to form a cylindrical structure having a certain strength. This silk yarn contains sericin in addition to fibroin. By removing this sericin, the possibility of causing an allergic reaction as a heterologous antigen is greatly reduced. In this small-diameter artificial blood vessel, the step of forming a multilayered tubular structure by braiding fibroin yarns in multiple layers is performed using a kite yarn as the fibroin yarn, and the formed multilayer After the step of removing sericin from the cylindrical structure, the multilayer cylindrical structure can be manufactured by a manufacturing method in which the step of coating with a fibroin is performed.

  The sericin can be removed by a known method used in the scouring of silk thread, for example, by immersing in a heated alkaline aqueous solution and washing with water. Examples of such an alkaline aqueous solution include a sodium carbonate aqueous solution and a sodium hydrogen carbonate aqueous solution. The heating temperature is generally in the range of 90 ° C. or higher, preferably 98 ° C. or higher, and this can be preferably carried out by boiling at atmospheric pressure. The washing with water can be performed at room temperature, for example. Washing with water is preferably performed thoroughly. The water used for washing is preferably high-purity water such as distilled water, deionized water, or filter permeated water.

  The following examples further illustrate the present invention. The present invention is not limited to the examples shown below.

[Preparing materials]
[Production of three-layered small-diameter artificial blood vessel using fibroin] (Example)
Sixteen 27-denier yarns were used and braided using a mandrel to obtain a three-layered cylindrical structure. This cylindrical structure was refined by immersing it in a 0.02 M aqueous sodium carbonate solution heated to 100 ° C. for 30 minutes and then washing with distilled water to remove sericin. On the other hand, fibroin was dissolved in an aqueous lithium bromide solution and dialyzed to prepare a 2-3% concentration fibroin solution. The three-layered cylindrical structure from which sericin had been removed was immersed in this fibroin solution at room temperature and then dried at room temperature to obtain a three-layered small-diameter artificial blood vessel. The caliber (inner diameter) was 1.5 mm, 2.0 mm, and 3.0 mm.

[Small-diameter artificial blood vessel made of PTFE] (Comparative example)
As a comparative material, a small-diameter artificial blood vessel made of PTFE, which is commercially available for animal clinical experiments, ie, ePTFE (expanded polytetrafluoroethylene: gore-tex) (Japan Gore-Tex Co., Ltd., trade name: Gore-Tex (registered) (Trademark) artificial blood vessel).

[Manufacture of small-diameter artificial blood vessels with one-layer structure using fibroin] (Comparative example)
A small-diameter artificial blood vessel having a single-layer structure was manufactured in the same manner as in the example except that a single-layer structure was used as a material for the comparative example. However, immersion with a fibroin solution was not performed.

[Transplantation and observation of small-diameter artificial blood vessels]
A three-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE were implanted into the abdominal aorta of a rat (Sprague Dawley Rat, 10-14 weeks old, male), and the progress was observed. A small-diameter artificial blood vessel having a diameter of 1.5 mm or 2.0 mm and a length of 10 mm or 15 mm was used. The transplantation was performed by anastomosing a small-diameter artificial blood vessel to the abdominal aorta. In the observation of the course, the patency of the lumen of the artificial blood vessel was confirmed by an ultrasonic diagnostic apparatus, and the histological examination of the cross section of the artificial blood vessel was also performed.

In addition, a one-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE were implanted into the abdominal aorta of a rabbit (New Zealand White Rabbit, body weight 2.5-3 kg, male), and the progress was observed. went. The transplantation was performed by anastomosing a small-diameter artificial blood vessel to the abdominal aorta. A small-diameter artificial blood vessel having a diameter of 3.0 mm and a length of 20 mm was used. In the observation of the course, the patency of the lumen of the artificial blood vessel was confirmed by an ultrasonic diagnostic apparatus, and the histological examination of the cross section of the artificial blood vessel was also performed.
These experiments and their results were compared with the experiments of transplanting three-layered small-diameter artificial blood vessels with fibroin, transplanting experiments with three-layered small-diameter artificial blood vessels with fibroin and small-diameter artificial blood vessels made of PTFE, and one-layer structure with fibroin. This will be described in detail below in the order of transplantation experiments of small-diameter artificial blood vessels and PTFE-made small-diameter artificial blood vessels.

[Transplantation experiment of three-layered small-diameter artificial blood vessel with fibroin]
In the following, a transplantation experiment of a small-diameter artificial blood vessel having a three-layer structure with fibroin and its result will be described in detail with reference to the drawings.

  FIG. 1 shows a three-layered small-diameter artificial blood vessel (upper part of FIG. 1) (diameter 2.0 mm, length 15 mm) using fibroin used for implantation into a rat and the appearance immediately after implantation into a rat abdominal aorta. Shown (bottom of FIG. 1). Although this end-to-end anastomosis is an extremely difficult operation, an artificial blood vessel has been stably transplanted. The end of the artificial blood vessel was stable and there was no excessive bleeding from the artificial blood vessel.

  FIG. 2 shows images obtained by observing the luminal surface of a three-layered small-diameter artificial blood vessel with a transplanted fibroin with a scanning electron microscope at 2 weeks (2w) and 4 weeks (4w) after transplantation. Cells that are thought to be vascular endothelial cells have already migrated and established after 2 weeks, and after 4 weeks, the luminal surface of the three-layered small-diameter artificial blood vessel with fibroin is almost completely covered. Observed. In other words, a three-layered small-diameter artificial blood vessel made of transplanted fibroin has the ability to induce migration and colonization of these cells, and has the same luminal surface as the original blood vessel. I found out.

  FIG. 3 further shows the appearance, ultrasonic diagnostic image, and angiogram of a three-layered small-diameter artificial blood vessel with fibroin 12 weeks after transplantation. The three-layered small-diameter artificial blood vessel made of the transplanted fibroin was found to be extremely stable even after 12 weeks from the transplantation and functioned in the same manner as the original aorta.

  FIG. 4 shows histological observation images by HE staining of a cross section of a three-layered small-diameter artificial blood vessel with fibroin two weeks, four weeks, and 12 weeks after transplantation.

  FIG. 5 shows a cross-sectional appearance, a histological observation image (HE, CD31, SMA), and a transmission electron microscope image (TEM) of a three-layered small-diameter artificial blood vessel with fibroin four weeks after transplantation. In the three-layered small-diameter artificial blood vessel made of transplanted fibroin, endothelial cells (EC) and smooth muscle cells (SMC) migrate and settle, and a layer corresponding to the vascular endothelium and media is formed. It was found that the small-diameter artificial blood vessel having a three-layer structure according to the above is highly biocompatible.

  FIG. 6 shows a histological observation image (HE, CD31, CD68, SMA) of a cross-section of a three-layered small-diameter artificial blood vessel with fibroin 12 weeks after transplantation. CD68 stains monocytes around fibroin, αSMA stains smooth muscle cells, and CD31 stains endothelial cells. It was found that a three-layered small-diameter artificial blood vessel made of fibroin is highly biocompatible and forms a structure very similar to the original blood vessel wall.

  FIG. 7 shows the appearance, cross-sectional appearance, and histological observation image by HE staining of a three-layered small-diameter artificial blood vessel with fibroin 24 weeks after transplantation. The three-layered small-diameter artificial blood vessel made of transplanted fibroin has the same appearance and cross section as the original aorta 24 weeks after transplantation, has patency, and functions in the same way as the original aorta I found out. In other words, a three-layered small-diameter artificial blood vessel made of transplanted fibroin has a very effective ability to induce vascularization (angiogenic ability) in addition to the ability to induce migration of endothelial cells and smooth muscle cells. I found out.

  FIG. 8 shows polarized microscopic images by Sirius red staining of a cross-section of a three-layered small-diameter artificial blood vessel with fibroin two weeks and 24 weeks after transplantation. It is observed that many collagen fibers that were not observed at the time point after 2 weeks were formed along the fibroin fibers at the time point after 24 weeks. That is, the ability to induce vascularization (angiogenesis) of a three-layered small-diameter artificial blood vessel by fibroin extends not only to cell migration and colonization, but also to the reconstruction of the vascular structure formed by the extracellular matrix. I understood it. In addition, it is considered that the formation of such collagen fibers contributes to the provision of sufficient strength and durability over a long period, which is an advantageous characteristic of the three-layered small-diameter artificial blood vessel using fibroin of the present invention. .

  FIG. 9 shows a histological observation image (CD31, αSMA, Masson, Siriusred) of a cross section of a three-layered small-diameter artificial blood vessel with fibroin 24 weeks after transplantation. It was found that the structure similar to the blood vessel wall is closer to the blood vessel wall, and the collagen fibers contributing to the strength are denser.

[Three-layered small-diameter artificial blood vessel with fibroin and PTFE-made small-diameter artificial blood vessel]
Hereinafter, a transplantation experiment and a result of comparison between a three-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE will be described with reference to the drawings.

  FIG. 10 shows a three-layered small-diameter artificial blood vessel (upper left in FIG. 10) (diameter 1.5 mm, length 10 mm) with fibroin used for implantation into the rat and immediately after implantation into the rat abdominal aorta. Appearance (bottom left of FIG. 10), and PTFE small-diameter artificial blood vessel (upper right of FIG. 10) used for implantation into the rat (both 1.5 mm, length 10 mm) and the rat abdominal aorta The appearance immediately after transplantation (lower right of FIG. 10) is shown. Although this end-to-end anastomosis is an extremely difficult operation, an artificial blood vessel has been stably transplanted. The end of the artificial blood vessel was stable and there was no excessive bleeding from the artificial blood vessel.

  FIG. 11 shows ultrasonic diagnostic images of a three-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE two weeks after transplantation. It was found that the three-layered small-diameter artificial blood vessel made of fibroin showed good patency, whereas the small-diameter artificial blood vessel made of PTFE did not show very good patency.

  FIG. 12 shows angiograms of a three-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE 12 weeks after transplantation. It was found that the small-diameter artificial blood vessel having a three-layer structure made of fibroin showed good patency, whereas the small-diameter artificial blood vessel made of PTFE was inferior in patency.

  FIG. 13 compares the patency of a three-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE by echocardiography, and shows the proportion of individuals showing sufficient patency. Shows the graph quantified as. At 4 weeks after transplantation, the patency rate of the three-layered small-diameter artificial blood vessel by fibroin is 95%, which is 3% compared to the patency rate of 35% of the small-diameter artificial blood vessel made of PTFE. The patency rate is more than double. The 95% patency rate of the three-layered small-diameter artificial blood vessel by fibroin does not decrease even after 32 weeks from the transplantation, and the lifetime of the individual is reduced except for individuals who have had patency problems very early. As long as it continues, the results are expected to maintain excellent patency.

  FIG. 14 shows a histological observation image of a cross section of a small-diameter artificial blood vessel made of PTFE 2 weeks after transplantation (2w) and 4 weeks later (4w). It was found that the low patency of the small-diameter artificial blood vessel made of PTFE as shown in FIG. 13 is due to thrombus formation.

[Transplantation experiment of a one-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE]
Hereinafter, a transplantation experiment comparing the small-diameter artificial blood vessel having a single layer structure with fibroin and the small-diameter artificial blood vessel made of PTFE and the results thereof will be described in detail with reference to the drawings.

  FIG. 15 shows a one-layered small-diameter artificial blood vessel (upper tube in FIG. 15) (diameter 3 mm, length 20 mm) with fibroin used for transplantation into a rabbit and immediately after transplantation into the abdominal aorta of a rabbit. Appearance (upper part of FIG. 15) and PTFE small-diameter artificial blood vessel (lower tube in FIG. 15) (caliber 3 mm, length 20 mm) used for implantation into the rat, and implantation into the abdominal aorta of the rat The appearance immediately after (the lower part of FIG. 15) is shown. Although end-to-end anastomosis of the artificial blood vessel was possible, the single-layered small-diameter artificial blood vessel made of fibroin often leaked blood from the artificial blood vessel immediately after the operation, and this hemostasis was difficult.

  FIG. 16 shows a histological observation image (HE, CD31) of a cross section of a small-diameter artificial blood vessel having a single layer structure and a small-diameter artificial blood vessel made of PTFE by fibroin four weeks after transplantation.

  FIG. 17 shows an image obtained by observing the inner surface of a small-diameter artificial blood vessel having a one-layer structure and a small-diameter artificial blood vessel made of PTFE with a scanning electron microscope 4 weeks after transplantation. Only a few vascular endothelial cell migrations and colonies were observed.

  FIG. 18 shows a cross-sectional appearance and a histological observation image of a one-layered small-diameter artificial blood vessel and a small-diameter artificial blood vessel made of PTFE with fibroin three months after transplantation. In either case, cell colonization and accompanying vascularization were insufficient.

  FIG. 19 shows an image obtained by observing the inner surface of a small-diameter artificial blood vessel having a single layer structure and a small-diameter artificial blood vessel made of PTFE with fibroin three months after transplantation using a scanning electron microscope. Even at this time, vascular endothelial cells and the like were not sufficiently established.

  FIG. 20 compares the patency of a one-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE by echocardiography, and shows the percentage of individuals showing sufficient patency. Shows the graph quantified as. Despite the use of a small-diameter artificial blood vessel with a relatively large diameter of 3 mm, both the one-layered small-diameter artificial blood vessel made of fibroin and the small-diameter artificial blood vessel made of PTFE are as low as 70% after 12 weeks. It became a survival rate. The one-layered small-diameter artificial blood vessel made of fibroin showed a slightly better patency than the small-diameter artificial blood vessel made of PTFE transiently between 4 weeks and 12 weeks later. It was also found that the patency was as low as about the same.

FIG. 1 is a view showing a three-layered small-diameter artificial blood vessel made of fibroin and an appearance immediately after implantation into a rat abdominal aorta. FIG. 2 is a view showing an image obtained by observing the inner surface of a small-diameter artificial blood vessel having a three-layer structure with a transplanted fibroin with a scanning electron microscope. FIG. 3 is a view showing an appearance, an ultrasonic diagnostic image, and an angiogram of a three-layered small-diameter artificial blood vessel made of transplanted fibroin. FIG. 4 is a view showing a histological observation image of a cross section of a small-diameter artificial blood vessel having a three-layer structure with the transplanted fibroin. FIG. 5 is a view showing a cross-sectional appearance and a histological observation image of a small-diameter artificial blood vessel having a three-layer structure with a transplanted fibroin. FIG. 6 is a view showing a histological observation image of a cross section of a small-diameter artificial blood vessel having a three-layer structure by the transplanted fibroin. FIG. 7 is a diagram showing an appearance, a cross-sectional appearance, and a histological observation image of a three-layered small-diameter artificial blood vessel made of transplanted fibroin. FIG. 8 is a diagram showing a polarization microscope image of a cross section of a three-layered small-diameter artificial blood vessel made of transplanted fibroin. FIG. 9 is a view showing a histological observation image of a cross section of a small-diameter artificial blood vessel having a three-layer structure with the transplanted fibroin. FIG. 10 is a diagram showing a three-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE and the appearance immediately after transplantation into the abdominal aorta of a rat. FIG. 11 is a diagram showing an ultrasonic diagnostic image of a three-layered small-diameter artificial blood vessel made of transplanted fibroin and a small-diameter artificial blood vessel made of PTFE. FIG. 12 is a view showing an angiogram of a three-layered small-diameter artificial blood vessel made of transplanted fibroin and a small-diameter artificial blood vessel made of PTFE. FIG. 13 is a graph quantifying the patency of a three-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE. FIG. 14 is a view showing a histological observation image of a cross section of a transplanted PTFE small-diameter artificial blood vessel. FIG. 15 is a view showing a single-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE, and the appearance immediately after implantation into the abdominal aorta of a rat. FIG. 16 is a view showing a histological observation image of a cross section of a one-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE. FIG. 17 is a view showing an image obtained by observing the inner surface of a small-diameter artificial blood vessel having a one-layer structure and a small-diameter artificial blood vessel made of PTFE with a scanning electron microscope using the implanted fibroin. FIG. 18 is a view showing a cross-sectional appearance and a histological observation image of a one-layered small-diameter artificial blood vessel made of transplanted fibroin and a small-diameter artificial blood vessel made of PTFE. FIG. 19 is a diagram showing an image obtained by observing the inner surface of a small-diameter artificial blood vessel having a one-layer structure and a small-diameter artificial blood vessel made of PTFE with a scanning electron microscope using the implanted fibroin. FIG. 20 is a graph showing the quantification of the patency of a one-layered small-diameter artificial blood vessel made of fibroin and a small-diameter artificial blood vessel made of PTFE.

Claims (9)

  A multi-layered cylindrical structure formed by braiding braid yarns as fibroin yarns in three or four layers, wherein sericin is removed from the cylindrical structure, and the cylindrical structure is a fibroin A small-diameter artificial blood vessel having an inner diameter in the range of 1.0 to 5.0 mm, which is covered with 1.   The small-diameter artificial blood vessel according to claim 1, wherein the braided layer is three layers.   The small-diameter artificial blood vessel according to claim 1 or 2, wherein the kite yarn is a four-pitch kite yarn.   The small-diameter artificial blood vessel according to any one of claims 1 to 3, wherein the small-diameter artificial blood vessel has an inner diameter in a range of 1.5 to 3.0 mm.   The small-diameter artificial blood vessel according to any one of claims 1 to 4, which can be used in an artery of the systemic circulation system.   The small-bore artificial blood vessel according to claim 5, wherein the artery is an abdominal aorta. A step of braiding braid yarn as fibroin yarn into 3 or 4 layers to form a 3 or 4 layer cylindrical structure;
Removing sericin from the multi-layered cylindrical structure formed;
A step of immersing the obtained cylindrical structure in a fibroin solution and coating with fibroin,
A method for producing a small-diameter artificial blood vessel having an inner diameter in the range of 1.0 to 5.0 mm.   The method of claim 7, wherein the braided layer is three layers.   The method according to claim 7 or 8, wherein the fibroin solution used in the step of coating with fibroin is dialyzed after dissolving fibroin in an aqueous lithium bromide solution.