Vascular graft healing. II. FTIR analysis of polyester graft samples from implanted bi-grafts

Abstract

FTIR-ATR analysis has shown that the 4-step process for preclotting polyester vascular grafts results in a uniform and reproducible fibrin coating of the polyester fibers. Western blot analyses have shown that FN and VEGF are also present in this fibrin coating. FTIR-ATR analyses of explanted grafts indicate that, while the in vivo healing of these preclotted polyester grafts proceed through the inflammation, proliferation, and remodeling phases of normal wound healing, these phases are modified. Because the fibrin coating provides a nonporous barrier between peri-graft tissue and the flowing blood, these molecular changes are controlled by the interactions of blood-borne constituents with the lumenal surface of the preclotted graft. Also, a well prepared preclotted polyester graft shows a minimal inflammatory response. After implantation, the fibrin preclot is more than 90% gone by the fifth day. However, the proliferation phase, involving synthesis of new protein and polysaccharide materials to replace the fibrin, appears to have begun by the third day. Detection of collagen I in the 5-day explants suggests that the overlapping remodeling phase of healing has begun. Protein and saccharide materials continue to be synthesized and remodeled, and, by the tenth day, collagen IV is detected. By 14-days post-implantation, there is an increase in collagen IV and cellular membrane lipids. Because collagen IV is an indicator of the presence of endothelial cells, some of these cellular membranes must be of endothelial origin. Thus, it appears that FTIR-ATR can be a useful tool in the study of vascular healing.

Prosthetic vascular grafts: Wrong models, wrong questions and no healing

“…Until 10 years ago, approximately 90% of prostheses in large animal models were as short as 5.571.2 cm (Dacron and expended polytetrafluoroethylene (ePTFE)) and 4.571.7 cm polyurethanes (PU), with a median implantation periods of 91.8717.3 days for Dacron grafts, 60.079.36 days for polytetrafluoroethylene (PTFE) grafts [11] and 907127.1 days for PU grafts. In more recent years, slightly longer grafts were implanted (64% were still shorter than 7 cm) and observation periods became shorter (medians: 28.078.9 and 14.0718.7 for ePTFE and Dacron, respectively) [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. In the small proportion of studies where truly long prostheses were implanted, they were either aorto-aortic [30][31][32][33][34][35], aorto-iliac [36][37][38][39] or aorto-femoral [40].…”

“…Typically, almost all the vascular graft studies in the past chose graft diameters that were largely size matched or even smaller than the artery and thus did not undercut the critical cross-sectional ratio from which point intimal hyperplasia develops. For example, the estimated mean Q c s for interposition grafts ranged from 0.63 to 42.0 in dogs [14][15][16][17]23,42,[63][64][65][66] (60 cm, top) and experimental grafts in animals (in the majority of studies o6 cm; bottom). In most animal models, transanastomotic endothelial outgrowth (red) leads to complete surface endothelialization within weeks making it impossible to study transmural or blood-born endothelialization.…”

“…Therefore, experimental conditions are largely ignorant of a phenomenon that is behind a significant proportion of clinical graft occlusions. rats [14][15][16][17]23,42,[63][64][65][66], 1.65 in pigs [32] and 0.77 to 1.00 in baboons [45,67,68]. Assuming normal anatomy for each species and weight group, the estimated average Q c for all studies considered in this review (n ¼ 70) was as high as 1.5270.11(SEM) (Fig.…”

Vascular graft healing. III. FTIR analysis of ePTFE graft samples from implanted bigrafts

“…Samples of ePTFE segments, retrieved at 1 and 3 h; 3, 5, 7, 10, and 14 days; and 4 and 8 weeks postimplantation, were analyzed by FTIR‐ATR. Empirical rules coupled with a number of experimental and theoretical studies7, 9–24 were used to assist in IR band assignments for these spectra.…”

“…The growth factors measured were vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and transforming growth factor beta (TGF‐β), and the cell adhesive protein fibronectin (FN), because these have been shown to be important in angiogenesis, endothelial cell proliferation, myointimal hyperplasia, smooth muscle cell growth, and wound healing 1–6. A Fourier‐transform infrared (FTIR) attenuated total reflectance (ATR) spectroscopy study of explanted segments of the preclotted PET portion of the bigraft indicated that the in vivo healing of the preclotted PET graft proceeded through the inflammation, proliferation, and remodeling phases of normal wound healing, forming an endothelialized surface, though these phases were modified 7…”