Vascular endothelial growth factor enhances vascularization in microporous small caliber polyurethane grafts

Neoarterial regeneration in an implanted small caliber vascular prosthesis is complexly controlled by many structural and biologic factors, such as cytokines. The authors designed an artificial graft, which was prepared as follows. Segmented polyurethane tubular film (inner diameter, 1.5 mm; wall thickness, 100 microns; length, 20 mm), in which micropores (pore size, 100 microns) were fabricated by an excimer laser ablation technique, were coated with a mixed solution of photoreactive gelatin and heparin with or without cytokines (vascular endothelial growth factor [VEGF]: 5 or 50 micrograms/ml, basic fibroblast growth factor [bFGF]: 1 microgram/ml). These coated grafts were irradiated by ultraviolet light, and were implanted in aortas of rats for 4 weeks; the VEGF (5 micrograms/ml) group, n = 6; the bFGF group, n = 6; the VEGF (5 micrograms/ml)/bFGF group, n = 11; the VEGF (50 micrograms/ml)/bFGF group, n = 5; and the control group, n = 9. Control grafts were treated without cytokines. Endothelial coverage was greater for the cytokine immobilized groups (approximately equal to 50-60%) than for the control group (approximately equal to 30%). At the midportion of the triple VEGF immobilized group, many capillaries were seen in the neoarterial intima, and in the micropores, although such capillaries were rarely observed in the bFGF and control groups. Thus, impregnation of VEGF in the gelatinous layer of grafts enhanced transanastomotic tissue ingrowth and transmural capillary ingrowth.