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Synthetic vascular prostheses are foreign bodies, so that blood coagulation can occur on their luminal surfaces, causing graft occlusion very frequently in prostheses of small diameter. A vascular prosthesis needs angiogenesis for endothelialization of the luminal surface, as endothelial cells have natural and permanent antithrombogenic properties. To induce capillary growth into the graft, we developed a method of transplanting bone marrow cells, which are primitive, strong enough to survive, and create blood cells, resulting in the inducement of capillary growth. In an animal experiment, marrow cells were infiltrated into the walls of long-fibril expanded polytetrafluoroethylene (ePTFE) vascular grafts. The grafts were implanted in the abdominal aortic position of 24 dogs autologously. Marrow cells survived and continued exogenous hemopoiesis for up to six months and were immunohistochemically reactive to basic fibroblast growth factor (bFGF). All the grafts older than three weeks had complete endothelialization and maintained their patency. Twenty grafts without bone marrow were implanted as controls. Endothelialization was present at anastomotic sites, but other areas were covered with fresh thrombi. Four out of seven control grafts were patent with endothelial cell lining at six months, but three were occluded and one of the four grafts was still covered with a thrombus layer. Bone marrow with its unique native properties produced autocrine angiogenicity in the graft.

As a three-dimensional carrier for cell culture, a honeycomb structure cell scaffold was created from atelopeptide collagen Types I, II, and III. The diameter of the honeycomb pores ranged from 100 to 1,000 microm. The depth of the pores was from 10 to 3,000 mm. The scaffold was elastic and hard. Creation of various shapes was easy, and these shapes were easily maintained. Human fibroblasts, CHO-K1, BHK-21, and bovine endothelial cells were cultured with the scaffold. The growth curves of these cells were satisfactory. These results suggest that this carrier is a suitable scaffold for cell culture and will be useful as a three-dimensional tissue engineering scaffold.

A segment of silk polyfilament suture [No. 2-0(USP)], ca. 10 cm long, was coated with a thin membrane (2-6 micron) of chitosan, N-acetylchitosan, or N-hexanoylchitosan. The suture was directly inserted into the lumen of dog's peripheral veins. The in vivo blood compatibility of these membranes was macroscopically determined from the blood coagulum formed on the membrane surface at 2 h. An intense thick blood coagulum formed on the chitosan membrane surface and a thin blood coagulum formed on N-acetylchitosan membrane surface, but no blood coagulum formed on N-hexanoylchitosan membrane surface.

Blood compatibility of regenerated silk fibroin was examined by in vivo blood tests. In vivo tests were made by a method of peripheral vein indwelling suture. The coating of sample fibroin on the polyester suture was made by casting either from aqueous or from formic acid solution. The fibroin-coated sutures from aqueous solution were treated with methanolic aqueous solution in order to denature the silk fibroin, and implanted into a jugular and femoral vein of a dog. The results of the test method employed in this work indicate that the regenerated silk fibroin is nonthrombogenic.

The epoxy group of the epoxy compounds has an oxygen arm that can work as a flexible joint in a cross‐linking bridge and can block not only the amino group but also the carboxy group of collagen peptide. The purpose of this study is to evaluate the anticalcification efficacy of the epoxy compounds as a cross‐linking agent for xenograft bioprostheses. Porcine aortic leaflets were treated with 2% epoxy compounds and implanted in subcutaneous layer of 4‐week‐old rats. Measurement of calcium content showed that epoxy‐treated implants received a minimal calcification: mean 0.64μg/mg dry weight leaflet tissue (range 0.5–0.8;N=7) at 1 month; mean 0.94μg/mg (range 0.3–1.3;N=9) at 2 months; and mean 1.2μg/mg (range 0.5–2.1;N=10) at 3 months. Natural leaflets contained calcium of mean 0.43μg/mg. By contrast, glutaraldehyde‐preserved implants were severely calcified: mean 91μg/mg (range 41–130;N=11) at 1 month; mean 136μg/mg (range 73–205;N=16) at 2 months; and mean 170μg/mg (range 90–214;N=21) at 3 months. The epoxy compounds provide more pronounced anticalcification effects than the glutaraldehyde under pressure load‐free subcutaneous circumstances.

Collagen from a native tissue is fixed with a polyepoxy compound (PC) for use as a new biologic prosthetic material. Prior studies have shown that this biomaterial has comparable properties with collagen fixed with glutaraldehyde (GA), and thus has great promise for biomedical applications. A prior kinetic study indicated that the reaction between the functional groups of collagen and the multifunctional epoxy EX-313 is a 2.5th-order reaction. The purpose of this study was to understand the mechanism of the amino acid-PC reactions in a fixation process. Bovine arteries were fixed with a monofunctional PC (EX-131) and a multifunctional PC (EX-313) as a function of fixation time. A sequential fixation with a second fixative was used to identify the available remaining reactive sites from a prior fixation. The denaturation temperature (Td) was measured on each sample. Because the denaturation temperature is a direct indication of crosslinking of individual amino acids with the fixative, the increase in Td of a subsequent fixation may be indicative of the available remaining amino acids. The fixation index was measured on each sample to reflect the increase of fixation completion in a sequential fixation process. The fixation index and crosslink data also revealed that the reactive amino acids for EX-131 and EX-313 may not be exactly the same. The data in this study suggest that a monofunctional fixative can pre-react with the amino acids of collagen to effectively block further fixation of collagen with a second fixative. This amino acid masking may be associated with collagen branching. Collagen branching and its effect on denaturation temperature are described.

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