EXTRACELLULAR-MATRIX DERIVED FROM HAIR AND SKIN FIBROBLASTS STIMULATES HUMAN SKIN MELANOCYTE TYROSINASE ACTIVITY

There is indirect evidence that both skin and hair melanocytes are reg ulated by the activity of adjacent cells. In hair, the specialized fib roblasts (dermal papilla cells) appear to play a role in the regulatio n of hair growth. Hair pigmentation may relate to hair growth. In skin , melanocytes are located adjacent to the basement membrane zone. As f ar as we are aware, direct interactions of fibroblasts with melanocyte s have not previously been investigated. Accordingly, the objective of this study was to develop co-culture conditions in which to investiga te whether dermal fibroblasts from skin or hair could influence melano cyte differentiation. The influence of fibroblast-conditioned media, c o-culture with fibroblasts, and fibroblast-derived extracellular matri x (ECM) on normal human skin melanocyte tyrosinase activity was examin ed. Fibroblasts from both skin and hair were capable of altering melan ocyte morphology and significantly increasing tyrosinase activity when melanocytes were cultured in the absence, but not the presence, of th e major proliferative drives. Although stimulation of tyrosinase activ ity was detectable with conditioned medium and co-culture with fibrobl asts, the most striking result was obtained with the fibroblast-produc ed ECM which, on average, produced a four-fold increase in tyrosinase activity within 6 days. Thus, the study describes co-culture condition s in which the stimulatory effect of the fibroblast on melanocyte diff erentiation can be examined.