Hedgehog signaling plays roles in epithelial cell proliferation in neonatal mouse uterus and vagina.

Both the uterus and vagina develop from the Müllerian duct but are quite distinct in morphology and function. To investigate factors controlling epithelial differentiation and cell proliferation in neonatal uterus and vagina, we focused on Hedgehog (HH) signaling. In neonatal mice, Sonic hh (Shh) was localized in the vaginal epithelium and Indian hh (Ihh) was slightly expressed in the uterus and vagina, whereas all Glioma-associated oncogene homolog (Gli) genes were mainly expressed in the stroma. The expression of target genes of HH signaling was high in the neonatal vagina and in the uterus, it increased with growth. Thus, in neonatal mice, Shh in the vaginal epithelium and Ihh in the uterus and vagina activated HH signaling in the stroma. Tissue recombinants showed that vaginal Shh expression was inhibited by the vaginal stroma and uterine Ihh expression was stimulated by the uterine stroma. Addition of a HH signaling inhibitor decreased epithelial cell proliferation in organ-cultured uterus and vagina and increased stromal cell proliferation in organ-cultured uterus. However, it did not affect epithelial differentiation or the expression of growth factors in organ-cultured uterus and vagina. Thus, activated HH signaling stimulates epithelial cell proliferation in neonatal uterus and vagina but inhibits stromal cell proliferation in neonatal uterus.