INVOLVEMENT OF FAS IN REGRESSION OF VAGINAL EPITHELIA AFTER OVARIECTOMY AND DURING AN ESTROUS-CYCLE

Fas, also called APO-1, belongs to the tumor necrosis factor/nerve gro wth factor receptor family and transmits an apoptotic signal within th e cell by binding to the Fas ligand. Fas has been implicated in the ac tivation-induced suicide of T cells and cytotoxic T cell activity in t he immune system, Non-immune cells such as those in liver, lung and ov ary also express Fas, but its role in these cells remains unclear. Ova riectomy has been used to study homeostasis of female reproductive org ans, which is regulated by sex hormones, Here we analyzed Fas function in the ovariectomy-induced regression of mouse vaginal epithelial cel ls, Fas expression was detected in vagina and was elevated after ovari ectomy, Fas-deficient lpr and lpr(cg) mice did not exhibit ovariectomy -induced regression of vaginal epithelia, whereas uterine regression i nduced by ovariectomy was not affected in these mice. The vaginas of l pr and lpr(cg) mice were in a persistent estrous stage with cornificat ion of vaginal epithelia, as judged from the cell types in the vaginal fluid, Thus, Fas appears to be involved directly in the regression of vaginal epithelia induced by ovariectomy and during the estrous cycle , suggesting that the physiological role of this receptor extends beyo nd that exerted on immune cells, This is the first evidence of a role for Fas in inducing physiological apoptosis in non-immune cells.