Tsuchida H, Wilson S E, Ishimaru S
Department of Surgery, Tokyo Medical College, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo, 160, Japan.
J Surg Res. 1997 Aug;71(2):187-95. doi: 10.1006/jsre.1997.5158.
A high-porosity structure facilitates endothelialization of polytetrafluoroethylene (PTFE) grafts. The mechanism for endothelial coverage, however, has been controversial. This study was designed to clarify the healing mechanisms of high-porosity PTFE grafts. Four types of PTFE grafts (n = 48) were studied after implantation in both carotid and femoral arteries of dogs. The grafts were standard (ST) PTFE [mean internodal distance (MID): 30 microm]; high-porosity (HP) PTFE (MID 90 microm), composite porosity (CP) PTFE (MID: inner layer, 90 microm; outer layer, 30 microm); and polyurethane-coated high-porosity (PCHP) grafts which had the outer surface covered with nonporous polyurethane. Patency rates at 18 weeks were ST 6/12, HP 8/12, CP 6/12, and PCHP 3/12 (P = 0.290). The rates of endothelialization (%, mean +/- SD) in the patent grafts were ST 25 +/- 7, HP 75 +/- 20,* CP 57 +/- 15,* and PCHP 17 +/- 5 (*P < 0.05 vs ST or PCHP). Rich transmural tissue incorporation was observed in the HP grafts. In contrast to the HP grafts, PCHP grafts had no outer tissue ingrowth, inner tissue incorporation was scant, and anastomotic intimal hyperplasia was pronounced. The edges of pannus ingrowth in the PCHP grafts were irregular, such that the anchoring of pannus was weak and easily detachable. Well-developed endothelial cells were observed in the HP and CP grafts, but nonendothelialized areas always occurred in the center of the grafts. Capillary openings were noted in the HP grafts; however, their number was small (0-8/graft) on electron microscopy and did not account for the degree of endothelialization observed. We conclude that the principal mechanism for endothelialization of PTFE grafts is ingrowth from the anastomoses rather than transmural endothelialization, even in high-porosity grafts. Transmural fibrocapillary incorporation of PTFE vascular grafts provides a key supporting structure essential to the progression and attachment of endothelial ingrowth from the anastomoses.
高孔隙率结构有助于聚四氟乙烯（PTFE）移植物的内皮化。然而，内皮覆盖的机制一直存在争议。本研究旨在阐明高孔隙率PTFE移植物的愈合机制。在将四种类型的PTFE移植物（n = 48）植入犬的颈动脉和股动脉后进行研究。这些移植物为标准（ST）PTFE[平均节间距离（MID）：30微米]；高孔隙率（HP）PTFE（MID 90微米），复合孔隙率（CP）PTFE（MID：内层90微米；外层30微米）；以及聚氨酯涂层高孔隙率（PCHP）移植物，其外表面覆盖有无孔聚氨酯。18周时的通畅率为ST 6/12、HP 8/12、CP 6/12和PCHP 3/12（P = 0.290）。通畅移植物中的内皮化率（%，平均值±标准差）为ST 25±7、HP 75±20*、CP 57±15*和PCHP 17±5（*与ST或PCHP相比，P < 0.05）。在HP移植物中观察到丰富的透壁组织长入。与HP移植物相反，PCHP移植物没有外部组织长入，内部组织长入很少，且吻合口内膜增生明显。PCHP移植物中血管翳长入的边缘不规则，使得血管翳的锚定较弱且容易分离。在HP和CP移植物中观察到发育良好的内皮细胞，但移植物中心总是存在未内皮化区域。在HP移植物中发现了毛细血管开口；然而，在电子显微镜下其数量较少（0 - 8个/移植物），且无法解释所观察到的内皮化程度。我们得出结论，即使在高孔隙率移植物中，PTFE移植物内皮化的主要机制也是来自吻合口的长入而非透壁内皮化。PTFE血管移植物的透壁纤维毛细血管长入为吻合口内皮长入的进展和附着提供了关键的支持结构。
