[Study on the optimal ratio of autoskin and alloskin during mixed microskin grafting]

To investigate the influence of different amount of allogeneic microskin in mixed grafting with certain quantity of autologous microskin on wound healing in rats. Methods Male Wistar rats served as alloskin donor rats. Forty female SD rats with full thickness skin defect were enrolled in the study, and they were randomly divided into four groups, i.e. group I (n=10, with allogeneic microskin graft at area expansion rate of 10:3); group II (n=10, with autologous microskin graft at area expansion rate of 10:1); group III (n=10, with mixed grafting of autologous and allogeneic microskin at area expansion rate of 10:1, respectively); group IV (n=10, with mixed grafting of autologous and allogeneic microskin at area expansion rate of 10:1 and 10:3, respectively). The wound healing rate, wound contraction rate and histological changes were observed at the 2, 3 and 4 post graft weeks (PGW).

(1) In group I, there was mainly granulation tissue with some de novo epithelial cells appearing at the wound edge along with the rejection of grafted allogenous skin in the rat wound. In group II, there was still some granulation tissue remaining at 2 PGW due to insufficient amount of microskin. However, the wounds in the mixed grafting group appeared almost totally epithelialized. (2) Various amounts of mononuclear inflammatory cell infiltration and different degrees of angiectasis were observed in the dermal layer after the skin grafting in all groups, especially in group II and IV. There was thickening of the epithelial layer in all groups except group I. (3) The wound healing rate decreased obviously along with the development of rejection in group I at 2 to 4 PGWs. The wound healing rate was (55 +/- 26)% in group II, which was obviously lower than that in group III (88 +/- 6)% and in group IV (76 +/- 10)% at 3 PGWs (P < 0.01). (4) The contraction rate of the wound in group IV (69 +/- 7)% was much higher than that in group I (58 +/- 11)% at 3 PGWs (P < 0.05), and there was no difference among all the other groups.

Wound healing can be obviously accelerated by mixing some autologous microskin with appropriate amount of alloskin. Moreover, certain amount of autologous microskin (expansion rate 10:1) mixed with the same proportion of allogeneic microskin seems to be more beneficial in promoting wound healing.