Human blood protein and cellular interactions in the healing responses of vascular prosthesis

Administration of granulocyte colony-stimulating factor enhances endothelialization and microvessel formation in small-caliber synthetic vascular grafts

OBJECTIVE

The purpose of this study was to determine whether systemic administration of granulocyte colony-stimulating factor (G-CSF) would promote endothelialization for small-caliber Dacron vascular grafts.

METHODS

We implanted 4-mm preclotted Dacron grafts in both carotids of 12 dogs. For a fair comparison, all dogs had a comparable platelet aggregation profile with platelet aggregation scores less than 30. Five dogs served as controls, and the others were given 7-day subcutaneous injections of G-CSF (10 microg/kg per day), starting on the seventh postoperative day. The effect of G-CSF was evaluated by white blood cell count, which showed a 3.7-fold (+/- 2.7-fold) increase at the end of treatment. Grafts were harvested at 4 weeks. All G-CSF grafts were patent, and one control occluded. Endothelial-like cell coverage averaged 80.8% on G-CSF grafts, but only 35.6% for control grafts (P <.0004). With the exclusion of the anastomotic pannus healing factor, the difference in endothelial-like cell coverage was even greater (68.5% vs 9.8%; P <.0001). Immunocytochemical staining and electron microscopy studies demonstrated endothelial cells. Light microscopy also showed that there were more microvessels on and in the G-CSF grafts than in the control grafts. This study suggests that G-CSF can enhance early endothelialization of small-caliber vascular grafts. Further studies to determine the proper dosage and timing are needed before clinical application can be recommended.

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 smooth muscle cells originating from the blood stream contribute to the endothelialization of impervious, small-caliber, long Dacron grafts used as extraanatomical bypasses in dogs. We implanted silicone-rubber-coated, permanently impervious grafts 64 to 77 cm long and 6 mm in diameter, made of externally supported knitted Dacron as unilateral carotid-femoral bypasses with distal femoral arteriovenous fistulae in 10 dogs 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 studied by stereomicroscopy with silver nitrate staining, by light microscopy with hematoxylin-eosin and immunocytochemical staining for endothelial and smooth muscle cells, and by scanning and transmission electron microscopy. Five grafts were patent for 3 months and could be included in the healing study; the five occluded grafts thrombosed within 14 days. Although there was no transinterstitial tissue ingrowth from perigraft tissues into the impervious Dacron grafts, scattered islands of endothelial cells were conclusively demonstrated on graft flow surfaces 3 months after implantation. Average endothelial-like cell coverage of the flow surfaces was 15.6% +/- 3.8%, and alpha-actin-positive smooth muscle cells and microvessels were found beneath some of the endothelial islands. These findings suggest that blood stream-derived endothelial and smooth muscle cells play a role in the healing of the inner wall of Dacron grafts in the dog.