Effects of EGF on the morphology and patterns of DNA synthesis in isolated human hair follicles.

We have previously reported that human hair grows at a normal rate in vitro for up to 10 d. We have also reported that, on gross observation, epidermal growth factor appears to induce a catagen-like effect on cultured hair follicles, but we have not characterized the details of this. We now report that when isolated human hair follicles are maintained in the presence of epidermal growth factor, the rate of hair follicle elongation is significantly stimulated but hair fiber production is inhibited. Light microscopy showed that epidermal growth factor stimulated a thickening and vacuolation of the cells of the lower outer root sheath of the hair follicle and that the matrix cells of the hair follicle underwent an upward migration resulting in the formation of a 'club hair'-like structure that remained connected to the dermal papilla by a thin strand of epithelial cells. [Methyl-3H] thymidine autoradiography was carried out to investigate the patterns of DNA synthesis and showed that epidermal growth factor inhibited DNA synthesis in the hair follicle matrix cells but dramatically stimulated DNA synthesis in the outer root sheath. We conclude from these studies that epidermal growth factor may be inducing an artificial 'catagen-like' effect by stimulating outer root sheath proliferation, which uncouples the normal patterns of proliferation and migration that occur in the anagen hair follicle and that result in an anagen-to-catagen-like transition. Moreover, these results also suggest that, under certain conditions, outer root sheath cells in the hair follicle may be capable of downward migration.