Normal and gene-corrected dystrophic epidermolysis bullosa fibroblasts alone can produce type VII collagen at the basement membrane zone

Type VII collagen is synthesized and secreted by both human keratinocytes and fibroblasts. Although both cell types can secrete type VII collagen, it is thought that keratinocytes account for type VII collagen at the dermal-epidermal junction (DEJ). In this study, we examined if type VII collagen secreted solely by dermal fibroblasts could be transported to the DEJ. We established organotypic, skin-equivalent cultures composed of keratinocytes from patients with recessive dystrophic epidermolysis bullosa (RDEB) and normal dermal fibroblasts. Immuno-labeling of skin equivalent sections with the anti-type VII collagen antibody revealed tight linear staining at the DEJ. RDEB fibroblasts, were gene-corrected to make type VII collagen and used to regenerate human skin on immune-deficient mice. The human skin generated by gene-corrected RDEB fibroblasts or normal human fibroblasts combined with RDEB keratinocytes restored type VII collagen expression at the DEJ in vivo. Further, intradermal injection of normal human or gene-corrected RDEB fibroblasts into mouse skin resulted in the stable expression of human type VII collagen at the mouse DEJ. These data demonstrate that human dermal fibroblasts alone are capable of producing type VII collagen at the DEJ, and it is possible to restore type VII collagen gene expression in RDEB skin in vivo by direct intradermal injection of fibroblasts.