PERMANENT SKIN REPLACEMENT USING CHIMERIC EPITHELIAL CULTURED SHEETS COMPRISING XENOGENEIC AND SYNGENEIC KERATINOCYTES

The present study was undertaken to evaluate the possibility of perman ent skin replacement using chimeric xenogeneic-syngeneic graftable she ets previously obtained in vitro. Newborn (<3 days old) BALB/c and hum an keratinocytes were isolated and cocultured in different ratios as f ollows: 50% BALB/c to 50% human and 25% BALB/c to 75% human keratinocy tes, Four to 5 days after culture and prior to their grafting, all chi meric sheets contained both cell types in ratios similar to those used to seed the initial chimeric cultures. Fourteen and 30 days after chi meric sheet grafting onto BALB/c mice dorsum, the newly generated cuta neous tissue showed a histologically well-organized epidermis presenti ng basal and suprabasal cell layers. Cutaneous cells in these structur es secreted laminin and type IV collagen in blood vessels, and at grou nd level of the dermoepidermal junction there were signs of physiologi cally active skin. Cell phenotyping revealed the presence of only syng eneic keratinocytes, whereas xenogeneic cells were passively eliminate d without a total rejection of the chimeric implant, This selective an d passive elimination of xenogeneic keratinocytes went through cellula r and humoral immunity activation. Data suggest that this chimeric cul ture method can be used for cutaneous therapies such as large congenit al nevi, skin ulcers, and extensively burned skin, Indeed, for large t hird-degree wounded skin treatment, this culture method may shorten th e time (4-5 weeks) needed for cell growth and graftable sheet producti on. Moreover, since the ultimate aim in allogeneic and xenogeneic tran splantation is to achieve an immunological acceptance and tolerance to these foreign tissues, the chimeric culture approach may provide ways to lighten tolerance phenomena on cutaneous tissue.