Organized skin structure is regenerated in vivo from collagen-GAG matrices seeded with autologous keratinocytes

A well-characterized collagen-glycosaminoglycan matrix (CGM) that has been shown to function as a dermal analog was seeded with freshly disaggregated autologous keratinocytes and applied to full-thickness wounds in a porcine model. CGM were impregnated with 50,000 keratinocytes per cm², a seeding density that produces a confluent epidermis within 19 d post- grafting and affords a 60-fold surface expansion of the donor epidermis. In this study, the temporal sequence of events in epidermal and neodermal formation was analyzed histopathologically and immunohistochemically from 4 to 35 d post-grafting. The epidermis was observed to form from clonal growth of individual keratinocytes into epithelial cords and islands that gradually enlarged, coalesced, differentiated to form large horn cysts, and finally reorganized at the graft surface to form a fully differentiated, normally oriented epidermis with rete ridges. Simultaneously, a neodermis formed from migration of endothelial cells, fibroblasts, and macrophages into the CGM from the underlying wound bed, resulting in formation of blood vessels, the production of abundant extracellular matrix, and the degradation of the CGM fibers, respectively. Gradually, the stromal cellularity of the CGM decreased and collagen deposition and remodeling increased to form a neodermal connective tissue matrix beneath the newly formed epidermis. Complete dissolution of the CGM occurred, partly as a result of degradation by an ongoing foreign-body giant cell reaction that peaked at 8-12 d post-grafting, but neither acute inflammation nor evidence of immune stimulation were observed. Within 1 mo, many structural components of normal skin were reconstituted.