Skin substitutes from cultured cells and collagen-GAG polymers

Engineering skin substitutes provides a potential source of advanced therap ies for the treatment of acute and chronic wounds. Cultured skin substitute s (CSS) consisting of human keratinocytes and fibroblasts attached to colla gen-glycosaminoglycan substrates have been designed and tested in preclinic al and clinical studies. Cell culture techniques follow general principles of primary culture and cryopreservation in liquid nitrogen for long-term st orage. Biopolymer substrates are fabricated from xenogeneic (bovine) collag en and glycosaminoglycan that are lyophilised for storage until use. At mat urity in air-exposed culture, CSS develop an epidermal barrier that is not statistically different from native human skin, as measured by surface elec trical capacitance. Preclinical studies in athymic mice show rapid healing, expression of cytokines and regulation of pigmentation. Clinical studies i n burn patients demonstrate a qualitative outcome with autologous skin that is not different from 1:4 meshed, split-thickness autograft skin, and with a quantitative advantage over autograft skin in the ratio of healed skin t o biopsy areas. Chronic wounds resulting from diabetes or venous stasis hav e been closed successfully with allogeneic CSS prepared from cryopreserved skin cells. These results define the therapeutic benefits of cultured skin substitutes prepared with skin cells from the patient or from cadaver donor s. Future directions include genetic modification of transplanted cells to improve wound healing transiently or to deliver gene products systemically.