Distribution and hormonal regulation of membrane progesterone receptors β and γ in ciliated epithelial cells of mouse and human fallopian tubes

Background: The controlled beating of cilia of the fallopian tube plays an important role in facilitating the meeting of gametes and subsequently transporting the fertilized egg to its implantation site. Rapid effects of progesterone on ciliary beat frequency have been reported in the fallopian tubes of cows, but the identity of the receptors mediating this non-genomic action of progesterone is not known. We recently identified a member of the non-genomic membrane progesterone receptor family, mPR gamma, as a candidate for mediating these actions of progesterone. Here, we investigated the possible presence of a related receptor, mPR beta, in the fallopian tubes of mice and women as well as the possible hormonal regulation of mPR beta and gamma. -- Methods: Western blot and immunohistochemistry with specific antibodies were used to characterize the expression and cellular localization of the mPRs in mouse and human tissues. Taqman (Quantitative Polymerase Chain Reaction) assays were used to quantify mRNA levels in the fallopian tubes of two different mouse models after injections with different hormones and specific antagonists. -- Results: In the fallopian tubes of both mouse and human, the expression of mPR beta and mPR gamma proteins was exclusively found in the ciliated cells. Whereas mPR beta was found on the cilia, mPR gamma was localized at the base of the same ciliated cells, as previously reported. In gonadotropin-primed mice, both mPRs genes were down-regulated after an injection with progesterone. Treatment with estradiol rapidly down-regulated the level of mPR beta mRNA and protein in immature mice. The mPR gamma protein was down-regulated around the time of ovulation in cycling women, similar to the regulation observed in mice stimulated to ovulate via gonadotropin injections. -- Conclusion: Our findings show the presence and hormonal regulation of two distinct mPRs associated with the cilia of the fallopian tubes in both mice and women. It is hypothesized that these receptors are involved in the control of ciliary movement and, thus, gamete transport in the fallopian tubes of mammals.