Is Estrogen a Cellular Signal for Female Genital Tract Epithelium?
In vivo, the vagina and uterus, and their respective epithelial linings, are considered to be estrogen target structures. As a result of classical endocrinological studies, their dependence on estrogen for growth and differentiation is considered axiomatic. In vitro, primary cultures of epithelial cells from the vagina and uterus, grown in collagen gel matrix in a serum-free medium, proliferate independently of the presence of added estrogen. Addition of estrogen to these primary cultures does not stimulate epithelial cell proliferation, even in suboptimal conditions, but rather retards their growth. The estrogen receptor system of these cultured cells appears to be functionally intact, and the cells respond to estrogen addition by specific product synthesis (progestin receptors). Thus, estrogen has a direct modulative effect on cultured vaginal and uterine epithelia, but estrogen is not a directly-acting mitogen for these cells. It appears that stromal and possibly organismal factors are essential synergists and/or mediators for estrogen’s well-known mitogenic effect on female genital epithelia in vivo. Several alternative pathways for estrogen action on female genital epithelia are suggested.
KeywordsVaginal Epithelium Uterine Epithelium Uterine Epithelial Cell Progestin Receptor Vaginal Epithelial Cell
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