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 regulated by the activity of adjacent cells. In hair, the specialized fibroblasts (dermal papilla cells) appear to play a role in the regulation of hair growth. Hair pigmentation may relate to hair growth. In skin, melanocytes are located adjacent to the basement membrane zone. As far as we are aware, direct interactions of fibroblasts with melanocytes have not previously been investigated. Accordingly, the objective of this study was to develop co-culture conditions in which to investigate whether dermal fibroblasts from skin or hair could influence melanocyte differentiation. The influence of fibroblast-conditioned media, co-culture with fibroblasts, and fibroblast-derived extracellular matrix (ECM) on normal human skin melanocyte tyrosinase activity was examined. Fibroblasts from both skin and hair were capable of altering melanocyte morphology and significantly increasing tyrosinase activity when melanocytes were cultured in the absence, but not the presence, of the major proliferative drives. Although stimulation of tyrosinase activity was detectable with conditioned medium and co-culture with fibroblasts, the most striking result was obtained with the fibroblast-produced ECM which, on average, produced a four-fold increase in tyrosinase activity within 6 days. Thus, the study describes co-culture conditions in which the stimulatory effect of the fibroblast on melanocyte differentiation can be examined.