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A number of types of stem cells have been shown to be effective in wound repair. In the present study the effect of homeobox A4 (HOXA4) overexpression by human umbilical cord mesenchymal stem cells (hUMSCs) on full-thickness skin repair was evaluated. Isolated hUMSCs were transfected with a lentivirus expressing HOXA4 and cultured for 21 days. Expression of the epidermal cell-specific markers, cytokeratins 14 and 18, was detected by immunohistochemistry and flow cytometry. Full-thickness skin defects (1.5 cm x 1.5 cm) were made on the backs of 45 nude mice, which were randomly divided into the following three treatment groups: Collagen membrane with lenti-HOXA4 hUMSC seed cells; collagen membrane with lentivirus expressing green fluorescent protein; and collagen membrane alone. On days 7, 14 and 21 following transplantation, tissue samples were harvested and examined by histology and western blot analysis. Flow cytometry showed that the transfection efficiency was 95.41% at a multiplicity of infection of 100, and that the lenti-HOXA4 hUMSCs differentiated into epidermal cells, expressing cytokeratins 14 and 18. In addition, re-epithelialization of wounds treated with lenti-HOXA4 hUMSCs was significantly greater than that in the control groups in the first week. By week three the epidermis was significantly thicker in the lenti-HOXA4 group than the control groups. Thus, transplantation of hUMSCs modified with Ad-HOXA4 promoted wound healing. [ABSTRACT FROM AUTHOR]