Proliferation and differentiation of mouse uterine epithelial cells in primary serum-free culture: estradiol-17 beta suppresses uterine epithelial proliferation cultured on a basement membrane-like substratum.

The effects of different substrata and estradiol-17 beta (E2) on proliferation and differentiation of mouse uterine epithelial cells was examined in a serum-free primary culture system. When cultured on rat-tail collagen gels, the epithelial cells rapidly increased in number to form a simple squamous cell layer that exhibited a relatively undifferentiated state (a few short microvilli, no secretory granules, and poorly developed endoplasmic reticulum). Addition of E2 into the culture medium did not affect the proliferation of epithelial cells on collagen gel. Uterine epithelial cells grown on a reconstituted basement membrane-like substratum (Matrigel) formed a simple columnar/cuboidal cell layer exhibiting fully developed characteristics (many long microvilli, many secretory granules, and fully developed endoplasmic reticulum). Examination of epithelial proliferation by counting substratum-attached cell number revealed only a slow increase in cell growth on Matrigel, and E2 did not significantly affect it. However, measurement of proliferating cells by labeling cells with 5-bromo-2'-deoxyuridine revealed that cells on Matrigel were replicating and that E2 (10(-7) to 10(-11) M) actually significantly suppressed epithelial proliferation. However, there was not an effect of E2 on total cell number, indicating that the cells in control medium replicate faster and detach more readily from the substratum than those in E2-supplemented medium on Matrigel. Thus, it is probable that E2 significantly reduces the rate of cell detachment from the substratum, which may mimic the in vivo condition where significant decrease in apoptosis or cell death is induced by E2.