APPARENT BLOOD-STREAM ORIGIN OF ENDOTHELIAL AND SMOOTH-MUSCLE CELLS IN THE NEOINTIMA OF LONG, IMPERVIOUS CAROTID-FEMORAL GRAFTS IN THE DOG

The purpose of this study was to determine whether endothelial and smo oth muscle cells originating from the blood stream contribute to the e ndothelialization of impervious, small-caliber, long Dacron grafts use d as extraanatomical bypasses in dogs. We implanted silicone-rubber-co ated, permanently impervious grafts 64 to 77 cm long and 6 mm in diame ter, made of externally supported knitted Dacron as unilateral carotid -femoral bypasses with distal femoral arteriovenous fistulae in 10 dog s for 3 months; sides were alternated between cases. Subjects received 162 mg/day of aspirin, and its effectiveness on platelet aggregation (PA) was evaluated and expressed as a PA score. Graft healing was stud ied by stereomicroscopy with silver nitrate staining, by light microsc opy with hematoxylin-eosin and immunocytochemical staining for endothe lial and smooth muscle cells, and by scanning and transmission electro n microscopy. Five grafts were patent for 3 months and could be includ ed in the healing study; the five occluded grafts thrombosed within 14 days. Although there was no transinterstitial tissue ingrowth from pe rigraft tissues into the impervious Dacron grafts, scattered islands o f endothelial cells were conclusively demonstrated on graft flow surfa ces 3 months after implantation, Average endothelial-like cell coverag e of the flow surfaces was 15.6% +/- 3.8%, and alpha-actin-positive sm ooth muscle cells and microvessels were found beneath some of the endo thelial islands. These findings suggest that blood stream-derived endo thelial and smooth muscle cells play a role in the healing of the inne r wall of Dacron grafts in the dog.