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 disa ggregated autologous keratinocytes and applied to full-thickness wound s in a porcine model. CGM were impregnated with 50,000 keratinocytes p er cm(2), a seeding density that produces a confluent epidermis within 19 d post-grafting and affords a 60-fold surface expansion of the don or epidermis, In this study, the temporal sequence of events in epider mal and neodermal formation was analyzed histopathologically and immun ohistochemically from 4 to 35 d postgrafting. The epidermis was observ ed to form from clonal growth of individual keratinocytes into epithel ial cords and islands that gradually enlarged, coalesced, differentiat ed to form large horn cysts, and finally reorganized at the graft surf ace to form a fully differentiated, normally oriented epidermis with r ete ridges, Simultaneously, a neodermis formed from migration of endot helial cells, fibroblasts, and macrophages into the CGM from the under lying wound bed, resulting in formation of blood vessels, the producti on of abundant extracellular matrix, and the degradation of the CGM fi bers, respectively. Gradually, the stromal cellularity of the CGM decr eased and collagen deposition and remodeling increased to form a neode rmal connective tissue matrix beneath the newly formed epidermis. Comp lete dissolution of the CGM occurred, partly as a result of degradatio n 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.