Early flow surface endothelialization before microvessel ingrowth in accelerated graft healing, with BrdU identification of cellular proliferation.

The purpose of this report was to determine if flow surface endothelialization could precede microvessel ingrowth from the perigraft area in porous Dacron grafts, by using an accelerated graft healing model with short implant periods. Dacron grafts were implanted in the abdominal aorta of 22 dogs and wrapped in autogenous inferior vena cava (IVC), which provided excellent conditions for extramural angiogenesis, microvessel development, and ingrowth toward the graft. Retrieval times were 7 days (n = 4), 8 days (n = 5), 9 days (n = 4), 10 days (n = 3), 11 days (n = 4) and 12 days (n = 3) postoperatively. Graft surfaces were evaluated for thrombus coverage, cell coverage, and the number of micro-ostia. Components and cellular types in the graft wall and on the surface were studied and characterized with H&E, histochemical, and immunocytochemical staining. BrdU labeling was also used, to identify the areas where cells were actively proliferating. All grafts were patent. Although the degree of IVC/graft attachment varied, isolated islands of endothelial-like cells were found at the midgraft areas at each time period, and immunocytochemically confirmed as endothelial cells. There were two healing patterns: (1) surface endothelialization before microvessel/tissue ingrowth from the perigraft areas, and (2) surface endothelialization with full wall microvessel and tissue presence. Surface endothelialization was observed before perigraft tissue ingrowth, indicating that fallout healing is an independent source of endothelialization for porous grafts.