Oviduct prostacyclin functions as a paracrine factor to augment the development of embryos

Recently we discovered that human oviducts produce a significant amount of prostacyclin (prostaglandin I2, PGI2) and that PGI2 enhances the potentials of live birth of mouse embryos. However, the eicosanoid profile of mouse oviducts remains unknown.

The metabolites of [14C]arachidonic acid by mouse oviducts were analysed by high-performance liquid chromatography. The expression of cyclooxygenase (COX)-1, COX-2 and PGI2 synthase (PGIS) was analysed by western blot analysis and immunohistochemistry. The PGI2 synthetic capacities and the COX transcripts during the preimplantation period were compared. The effects of COX-2 inhibitor on PGI2 production were ascertained.

Mouse oviducts produced, in order of abundance, PGI2, PGD2 and PGE2. Western blot analysis confirmed the expression of COX-1, -2 and PGIS which were expressed by luminal epithelia and smooth muscle cells. Day 2-3 post-coitus (p.c.) oviducts produced PGI2 10-fold higher than day 4 p.c. oviducts (P = 0.0087); day 1 p.c. oviducts expressed COX-2 transcript 5-fold higher than day 3 p.c. oviducts (P = 0.0004). The PGI2 production was markedly reduced by a selective COX-2 inhibitor.

Mouse oviducts synthesized maximal PGI2 during day 2-3 p.c., coinciding with the transformation of 2-cell embryos to morulae. The results suggest that oviduct-derived PGI2 may enhance embryo development in a paracrine fashion.