Dynamic and comparative vascular graft healing studies using multiple sequential biopsies.

In order to follow the dynamic healing processes of vascular grafts and to minimize the possible animal-to-animal variables involved in study results, we developed a carotid-femoral bypass model with multiple sequential biopsies. After bilateral implantation of 70 cm x 6 mm gelatin-impregnated carotid-femoral bypass grafts in 5 dogs, we biopsied and replaced three 10-cm-long segments of each bypass at 2, 4, and 6 weeks, with final retrieval at 8 weeks after the initial implant. The first surgery and later biopsy procedures were well tolerated with no mortality or morbidity, except for some seroma formation. We observed a dynamic progression of healing processes related to the time course, including perigraft tissue reaction to the graft material and surgical trauma, gradual absorption of the impregnated gelatin, tissue ingrowth into the graft wall, and changes in and healing of the graft surface. Because of the sizeable tissue sample generated from each biopsy, this model also allowed various study approaches to be performed on the same specimen. This experimental model enables study of the continuous dynamic healing processes of the same graft in the same animal, providing the practical advantage of reduction of the number of animals required.