Maintenance of in Vivo-Like Keratin Expression, Sex Steroid Responsiveness, and Estrogen Receptor Expression in Cultured Human Ectocervical Epithelial Cells*

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Abstract
In the present manuscript we demonstrate that ectocervical epithelial cells (ECE cells) retain a high degree of differentiated function when cultured using feeder layers. We characterize the cultured cells with respect to morphology, expression of cytokeratins, responsiveness to sex steroids, and the presence of estrogen-binding sites. Like ectocervical cells in vivo, the cultured cells display a typical epithelial cell morphology and undergo extensive stratification and envelope (superficial cell) formation. Like the in vivo ectocervical epithelium, the cultured ECE cells express type I cytokeratins K13, K14, K16, K17, and K19 and type II cytokeratins K5 and K6. Under normal culture conditions, however, cytokeratins K1, K2, K4, K11, and K15, which are expressed in vivo are not expressed. An interesting finding is that ECE cells, in contrast to endocervix and epidermis in vivo and cultured epidermal keratinocytes, express very abundant levels of K13. In fact, K13 appears to be a specific marker of ECE cells in the female reproductive tract. When incubated with 10 nm diethylstilbestrol, ECE cell envelope producion increased 3-fold, while incubation with 100 nm progesterone decreased envelope formation 3,4-fold. Simultaneous incubation with progesterone antagonized the diethyl stilbestrol stimulation. Thus, in vivo-like sex steroid regulation of ECE cell differentiation is maintained in culture. In addition, the cells possess a high affinity, limited capacity binding site for estradiol that has a Kd of 1.2 .+-. 0.1 nm. This system is likely to provide a useful model for the study of sex steroid regulation of normal ectocervical epithelial cell function.