Early vascularization of syngeneic, allogeneic and xenogeneic skin grafts

The vascularization of syngeneic, allogeneic and xenogeneic skin grafts 3-4 days after grafting was studied in inbred rats by injecting hosts with 51Cr labelled red cells on the third day and counting graft radioactivity on the fourth day. Vascularization as determined by this method was quantitatively similar in syngeneic, allogeneic and mammalian xenogeneic grafts, while the vascularization of non-mammalian xenografts was significantly inferior. For any one donor-host combination, full-thickness grafts contained relatively more blood than did split-thickness grafts, presumably because of the large vessels in the deep part of the dermis in full-thickness grafts. Full-thickness neonatal grafts were vascularized similarly to full-thickness adult skin grafts. Grafted skin contained relatively more blood than did the corresponding normal skin. Reconstituted freeze dried allogeneic skin grafts contained virtually no blood, a phenomenon possibly analogous to the 'no reflow' phenomenon of microsurgery. The inferior vascularization of non-mammalian xenografts is more plausibly explained on the basis of defective self recognition than as representing a reaction to foreign determinants. These results do not necessarily indicate that one type of graft is better than another in clinical practice. But if the beneficial effects of temporary skin grafts do indeed depend on their capacity to become vascularized, fresh skin appears preferable to reconstituted freeze dried skin.