Cultured human ectocervical epithelial cell differentiation is regulated by the combined direct actions of sex steroids, glucocorticoids, and retinoids.
During the menstrual cycle, the ectocervical epithelium undergoes a cyclic change in differentiation that is correlated with changes in the circulating levels of estrogens and progestins. To better understand the mechanisms underlying this regulation, we have developed an ectocervical epithelial cell (ECE cell) culture system that responds in a physiological manner to stimulation by estrogens and progestins. We have recently proposed that four classes of hormones (retinoids, estrogens, progestins, and glucocorticoids) may play an important role in regulating differentiation. In the present paper we test this hypothesis directly by making detailed dose-response curves. Our results demonstrate that estrogen increases ECE cell differentiation, as measured by release of cornified envelopes (superficial cells), while progesterone decreases envelope production. The effects are dose dependent and within the expected physiological range (0.01-10 nM estrogen; 0.1-100 nM progesterone). Very low concentrations of Ro 13-6298 (0.01-10 nM), a synthetic retinoid, decreased envelope production, while hydrocortisone (0.1-50 nM) increased envelope production and cell growth. Importantly, agents that enhance envelope production are neutralized by agents that reduce envelope formation and vice versa. Based on these findings we conclude 1) that the differentiation-enhancing actions of glucocorticoids and estrogens can be antagonized by either progestins or retinoids, and 2) that glucocorticoids and retinoids are likely to determine the ECE cell differentiation set-point in vivo, with the sex steroids directly modulating the phenotype of the ECE cells around this set-point during the menstrual cycle. Moreover, these results appear to explain some of the clinical descriptions of changes in ectocervical cell morphology resulting from hyper- and hypoestrogenic stimulation.