Species-specific in situ hybridization with fluorochrome-labeled DNA probes to study vascularization of human skin grafts on athymic mice.

The skin replacements presently used for wound coverage vascularize less well than do autologous split-thickness skin grafts. Understanding how autologous grafts vascularize can lead to methods to improve skin-replacement vascularization. Fresh human skin was grafted on athymic mice. Endothelial cells were stained by immunohistochemistry. Human and mouse cells were distinguished by in situ hybridization with fluorescent species-specific DNA probes. The number of mouse and human endothelial cells in the graft were counted. Initial vascularization of the graft is limited solely to anastamosis of severed ends of human vessels in the graft-to-mouse vessels in the recipient bed. Mouse endothelial cells gradually replace human endothelial cells in the graft. This demonstrates that initial vascularization of skin grafts is solely the result of inosculation rather than neovascularization. Skin replacements that contain vessels should vascularize like skin grafts, and methods to repopulate replacements with capillaries should be sought.