Stimulation of human keratinocyte proliferation through growth factor exchanges with dermal fibroblasts in vitro

Progress in biotechnology has led to new therapeutic approaches in various fields of human health care, such as the autologous grafting of cultured epidermal cell sheets on burned patients. These cultures depend on various parameters but growth factors are of paramount importance. Cutaneous cells are known to secrete various growth factors in vivo, although only a few have been identified. The aim of this study was to determine if such factors are secreted from human cutaneous cells in culture, to evaluate their effects on epidermal cell proliferation in vitro and to analyse them on SDS-PAGE. Human skin fibroblasts and keratinocytes were co-cultured for 8-10 days using a Costar trans-filter system. Dermo-epidermal cooperation was observed in such a co-culture system through the exchange of secretion products in the culture medium. Epidermal cell growth and metabolic activities were highly stimulated in co-culture (2-fold and 1.5-fold, respectively, P < 0.02) compared to the control. The de novo synthesis of secretion products, notably of a protein of about 40 kDa, was specifically induced in co-culture. The identification of new keratinocyte growth factors could accelerate graftable epidermal sheet production in vitro for human wound coverage and possibly enhance wound healing in vivo.