Inductive capacity of irradiated dermal papillae

Abstract

MAMMALIAN hair follicles are specialised skin appendages which produce a series of hairs, one after another, in a regular cyclical fashion. The hair itself is composed of dead epithelial cells containing large amounts of keratin. During growth of the hair the epithelial cells at the bottom of the follicle surround the dermal papilla and divide rapidly. The dermal papilla is derived from mesenchyme and is composed of non-dividing cells. The importance of the dermal papilla in maintenance and control of hair cycles has been assumed for many years but little direct evidence of its function has been demonstrated. Geary¹ caused permanent removal of rat body hair by applying 1,720 rad of X irradiation. He believed that he had caused destruction of the dermal papilla which in turn resulted in permanent epilation. We report here a study on the effect of heavy doses of irradiation on the dermal papilla and epithelial elements of the hair follicle. We have found that high doses of irradiation, which cause permanent epilation, destroy the epithelium but leave the dermal papilla anatomically and functionally intact so that even on transplantation it can induce a series of new hairs.