PROLIFERATION AND DIFFERENTIATION OF CULTURED HUMAN FOLLICULAR KERATINOCYTES ARE NOT INFLUENCED BY BIOTIN

In humans and in animals, biotin deficiency causes pathological change s in the skin and its appendages, High doses of biotin may also have b eneficial effects on skin, hair and fingernails in humans and animals with normal biotin status, Therefore, we investigated the effects of l ow and high concentrations of biotin on proliferation and differentiat ion of cultured outer root sheath cells from human hair follicles as a n in vitro model for skin, The activities of biotin-dependent carboxyl ases were measured to evaluate the biotin status of the cells, In mono layer cultures of outer root sheath cells, proliferation and expressio n of the differentiation-specific keratins K1 and K10 were not influen ced by extremely low concentrations of biotin (< 2 x 10(-10) mol/l) or by pharmacological doses of biotin (10(-5) mol/l), Biotin deficiency of the cells was confirmed under the former condition by demonstrating decreased activities of the mitochondrial carboxylases, In organotypi c cocultures of outer root sheath cells and dermal fibroblasts, in whi ch stratified epithelia resembling epidermis were developed, the bioti n concentration had no effect on the expression of all tested epiderma l differentiation markers, including the suprabasal keratins K1 and K1 0, the hyperproliferation-associated keratin K16, involucrin and filag grin.