Runx3 expression and its roles in mouse endometrial cells.

Runx3 is a transcription factor that belongs to the Runx family. We studied the localization of Runx3 mRNA in the mouse uterus, and its function in the mouse endometrium using Runx3 knockout (Runx3(-/-)) mice. Runx3 mRNA was detected in the endometrial luminal epithelial cells, glandular epithelial cells and stromal cells below the epithelial cell layer on the luminal side. The uteri of Runx3(-/-) mice were smaller than those of wt mice. The endometrial layer and uterine glands of Runx3(-/-) mice were less developed than those of wild-type mice, and the endometrial stromal layer was thinner. Transforming growth factor β1 and β3 (TGFβ1 and β3) mRNA levels in endometrial stromal cells of Runx3(-/-) mice were low compared with those of wild-type mice. Estradiol-17β (E2) increased Tgfb2 mRNA levels in endometrial stromal cells of Runx3(-/-) mice, but not in those of wild-type mice. E2 increased epidermal growth factor (EGF) mRNA levels in endometrial stromal cells of wild-type mice, but did not increase those of Runx3(-/-) mice. The diminished Tgfb1 and Tgfb3 mRNA expressions may lead to the reduced proliferation of endometrial stromal cells. Alterations of E2-associated expressions of Tgfb2 and Egf mRNA in endometrial stromal cells of Runx3(-/-) mice may be associated with suppression of E2-dependent endometrial epithelial cell proliferation in Runx3(-/-) mice. Thus, Runx3 is likely to be a regulatory factor responsible for endometrial growth.