Perivascular cells in a skin graft are rapidly repopulated by host cells

Survival of grafted tissues is dependent upon revascularisation. This study investigated revascularisation in a murine skin graft model, using two methods. The first involved 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine (DiI) labelling of the wound bed, prior to replacing the skin graft, to allow tracking of host cells into the grafts. At time points between day 3 and day 14 post-surgery, DiI-labelled cells which had tracked into the grafts, were found to co-localise with CD31 positive endothelial cells and patent perfused vessels (fluorescein isothiocyanate (FITC)-dextran perfusion), to show possible association with the vasculature. To further differentiate between graft and host-derived cells, C57BL/6 wild-type grafts were placed on enhanced-green fluorescent protein (e-GFP) transgenic mouse hosts, and at set times post-grafting examined using confocal microscopy. Patent vessels were found at all depths of the graft by day 3. Host (DiI- or GFP-positive) cells were predominantly co-localised with graft vessels in grafts from day 3 onwards, with a similar morphology to control skin. Significantly more GFP labelled host cells were visualised in the superficial dermis at day 5 compared to day 3. Initial restoration of circulation appears to be due to linkage between existing graft and bed vessels, followed by an influx of host cells with a definite perivascular distribution. These findings have implications for skin autografts and tissue engineered skin substitutes.