Revascularization of skin transplanted into the brain: source of the graft endothelium

Transplantation of tissues into the brain is becoming a feasible therapeutic approach to some neurological diseases. The fate of the graft vasculature is not well understood. The purpose of the present study was to determine the source of the endothelium in the revascularized skin grafts transplanted into the brain. We hypothesized that if the skin endothelium were replaced by brain endothelium then we should observe in the grafts the following: degenerating endothelium soon after grafting, regenerating endothelium subsequently, a time course for reestablishment of circulation that is consistent with the time required for vessel growth and invasion, and doubling of the vascular basement membrane a few weeks later. We found only a few degenerating endothelial cells soon after transplantation and no evidence of regenerating endothelium or of double layers of basement membrane even after prolonged survival. The vessels within mature grafts had morphological characteristics typical of normal skin vessels. We concluded that when tissue fragments are transplanted to the brain, native graft vessels survive and anastomose with host vessels.