Neovascularization of the intestinal graft transplanted in subcutaneous pocket in rats

Clinically, the intestinal graft can survive without blood supply through its vascular pedicle for a certain period after transplantation, which is generally considered to be due to newly formed vessels from the surrounding tissue to the graft. Vascular synthesis from the surrounding tissue to the pedicled intestinal graft, transplanted subcutaneously was studied in rat model. Both the carbon dye infusion technique and hematoxylin-eosin stain were employed. After transplantation of the intestine, the number and diameter of carbon stained vessels were scored on days 2, 5, 7, 10, 14, 28, and 56, when the pedicle was ligated. All the histological specimens of the intestinal grafts were analyzed and then classified into three phases depending on the extent of surviving mucosa: 'necrosis', no live mucosa were observed; 'incomplete take', some islands of mucosa were alive; and 'complete take', all mucosa were alive. We characterized the relationship between the changes of the newly formed (carbon-dyed) vessels and the three histological phases. At 'necrosis', the newly formed vessels were rare and did not reach the intestinal graft. At 'incomplete take', random thin vascular networks were observed and some of them reached the graft. Some specimens were in the 'incomplete take' phase. At 'complete take', regular large vascular networks were observed. This transformation of the vascular networks seemed to reduce the the resistance of the vascular flow and to finally lead to the 'complete take' of the graft.