Progesterone’s effect on gamete transport in the fallopian tube

The fallopian tube plays an important role in successful female reproduction because it transport gametes to the fertilisation site, nourishes the developing embryo and transports the embryo to the uterus at a suitable time for implantation. The overall aim of this thesis was to investigate the role of progesterone in the control of gamete transport. Ciliary cells are important for the transport of gametes and embryos through the fallopian tube. In paper I, we developed a method to measure ciliary movement in mouse fallopian tubes. Using a high-speed camera connected to a microscope, we were able to document the rapid effects of progesterone on the ciliary beat frequency in vitro. In ciliary cells from a mouse fallopian tube treated with progesterone at concentrations of 20 μM and a more physiologically relevant concentration of 100 nM, we found a rapid reduction in the ciliary beat frequency by 10 % and 15 %, respectively, within 30 minutes of the addition of progesterone. In paper II, we investigated the possible involvement of the classical progesterone receptor in mediating the rapid effect of progesterone. The ciliary beat frequency was significantly reduced within 10-30 minutes by low concentrations of progesterone (10-100 nM) and by another more specific agonist. Co-exposure to an antagonist completely blocked the effect of progesterone. In mice lacking a functional progesterone receptor, we found no effect of progesterone. These findings strongly indicate that progesterone reduces the ciliary beat frequency by acting on the classical progesterone receptor. The rapid onset of the effects suggests that a non-genomic mechanism is involved. In paper III, we used a microarray to investigate possible changes in the gene expression in mouse fallopian tubes after in vitro exposure to progesterone for 20 minutes or 2 hours. We could not detect any change in the gene expression with the microarray after 20 minutes of exposure to progesterone, which is consistent with the hypothesis that the rapid reduction in the ciliary beat frequency is not dependent on transcription. In fallopian tubes exposed to progesterone for 2 hours, 11 genes were differentially expressed compared with the controls. This change was confirmed by quantitative PCR at 2 h and 8 h. The most interesting gene regulated by progesterone was endothelin-1, a signal peptide known to induce muscle contraction in the fallopian tube. In this paper, we also studied the role of the progesterone receptor in the transport of the oocyte-cumulus complex. Gonadotropin-treated mice were given a single injection of one of the progesterone receptor antagonists Org 31710 or CDB2194 or vehicle 6 hours before ovulation. In the mice treated with both antagonists, the oocyte-cumulus complex travelled faster through the fallopian tube than in the mice only given vehicle. In conclusion, we found that progesterone rapidly reduces the ciliary beat frequency in ciliary cells from mouse fallopian tubes and that this reduction is mediated through the classical progesterone receptor, most likely via a non-transcriptional mechanism. We show that progesterone regulates endothelin-1, a peptide known to induce muscle contractions in the fallopian tube. This finding suggests that endothelin-1 is a mediator of the previously shown effects of progesterone on tubal contractility. We confirm earlier studies by demonstrating that progesterone and the progesterone receptor are important for normal tubal transport. Taken together, the results presented in this thesis contribute to a deeper understanding of the role of progesterone and the progesterone receptor in the regulation of gamete and embryo transport along the fallopian tube.