Upside-down transfer of porcine keratinocytes from a porous, synthetic dressing to experimental full-thickness wounds.

Currently, the use of cultured epithelial autografts as an alternative to split-thickness skin autografts for coverage of full-thickness wounds is limited due to fragility of the sheet and variability in the outcome of healing. This could be circumvented by the transfer of proliferating keratinocytes, instead of differentiated sheets, to the wound bed and the "in vivo" regeneration of epidermis. The aim of this study was to achieve re-epithelialization on experimental full-thickness wounds in the pig using a porous, synthetic carrier seeded with proliferating keratinocytes. Porcine keratinocytes were isolated by enzymatic digestion and cultured in Optimem basal medium with mitogens. In a full-thickness wound model, carriers with different seeding densities were transplanted upside down onto the wound bed. Keratinocytes were labeled using a fluorescent red membrane marker, PKH-26 GL. Transfer of keratinocytes and re-epithelialization were recorded macroscopically and histologically. On day 4 after transplantation, transfer of fluorescently labeled keratinocytes was shown by their presence in the granulation tissue. An immature epidermis, as well as epithelial cords and islands, formed as early as day 8. At day 12 a stratified epidermis and wound closure were established and epithelial cysts were formed by differentiation of epithelial islands. Wounds treated with seeding densities as low as 50,000 cells/cm(2) showed wound closure within 12 days, whereas wounds treated with 10,000 cells/cm(2) or the nonseeded (acellular) carriers did not show complete re-epithelialization before day 17 after treatment. This study showed that porcine keratinocytes, transplanted "upside down" in experimental full-thickness wounds using a synthetic carrier, continued to proliferate and started to differentiate, enabling the formation of a new epidermis in a time frame of 12 days.