Biocompatibility and Biofunctionality of a Gelatin Impregnated Polyester Arterial Prosthesis

Abstract

The gelatin-impregnated vascular graft Gelseal® and its parent Triaxial® graft were evaluated in terms of biocompatibility in rats and in vivo biofunctionality as a thoraco-abdominal bypass in dogs. The biocompatibility study was performed by implantation of small segments of graft in the peritoneal cavity of rats for scheduled periods of upto 4 weeks. Peripheral total T cells (CD3), T helper cells (CD4) and T suppressor cells (CD8) and activated T cells expressing IL-2 receptors were quantified by cytofluorometry. Enzymatic and histopathological analyses of the tissue at the implant site were also performed. In the rat, the Gelseal® graft induced a significant reduction of CD4 cells at 3 days, 1 and 4 weeks post-implantation when compared to the control group (wounded rats without prosthesis). On the other hand, the Triaxial® graft showed similar results to the control group except for a significant reduction of CD4 cells after 1 week. The percentage of CD3, CD8 and activated T cells expressing IL-2 receptors were similar to the control group. There was no statistical difference in acid phosphatase activity in the tissue surrounding the Gelseal® and the Triaxial® grafts. Histological studies of the impregnated graft have revealed an inflammatory reaction with polymorphonuclear cells which lasted slightly longer than the 2 weeks observed for the non-impregnated polyester control. Thereafter, the inflammatory response of both grafts became chronic and moderate. The investigation of in vivo biofunctionality was carried out by implanting the grafts as a thoraco-abdominal bypass in dogs for prescheduled periods of up to 6 months. The grafts were investigated for patency, morphology, healing sequerice, fibrin and platelet uptake and prostaglandin secretion. The healing characteristics of the Gelseal® graft were similar to the preclotted control. All grafts remained patent, and the small differences in platelet and fibrin uptake on the luminal surface between the impregnated and non-impregnated grafts were not statistically significant. The two healing sequences were also similar with the development of a collagenous internal capsule at 2 weeks post-implantation followed by the laying-down of endothelial-like cells at 1 month. The gelatin coating had completely eroded within the first month, at which time the PGI 2/ TXA 2 ratios determined on whole segments of grafts was higher than one. The Gelseal® graft has shown good biocompatibility and excellent healing characteristics as a thoraco-abdominal bypass in dogs and compares favourably with its parent graft the Triaxial® polyester prosthesis.