Mouse primary uterine cell coculture system revisited: ovarian hormones mimic the aspects of in vivo uterine cell proliferation.

Previously, the uterine epithelial-stromal coculture system had limited success mimicking in vivo ovarian hormone-dependent cell-specific proliferation. Here, we established a mouse primary uterine coculture system, in which cells collected in pseudopregnancy specifically on d 4 are conducive to supporting hormone-induced cell-specific proliferation. When two cell types are placed in coculture without direct contact via cell culture inserts (nonadjacent), as opposed to with contact (adjacent), epithelial cells exhibit significant proliferation by estradiol-17β (E2), whereas progesterone in combination with E2 caused inhibition of epithelial cell proliferation and a major shift in proliferation from epithelial to stromal cells. Epithelial cell integrity, with respect to E-cadherin expression, persisted in nonadjacent, but not adjacent, conditions. In subsequent studies of nonadjacent cocultures, localization of estrogen receptor (ER)α and progesterone receptor (PR), but not ERβ, appeared to be abundant, presumably indicating that specific ER or PR coregulator expression might be responsible for this difference. Consistently, an agonist of ERα, but not ERβ, was supportive of proliferation, and antagonists of ER or PR totally eliminated cell-specific proliferation by hormones. RT-PCR analyses also revealed that hormone-responsive genes primarily exhibit appropriate regulation. Finally, suppression of immunoglobulin heavy chain binding protein, a critical regulator of ERα signaling, in epithelial and/or stromal cells caused dramatic inhibition of E2-dependent epithelial cell proliferation, suggesting that a molecular perturbation approach is applicable to mimic in vivo uterine control. In conclusion, our established coculture system may serve as a useful alternative model to explore in vivo aspects of cell proliferation via communication between the epithelial and stromal compartments under the direction of ovarian hormones.