Periovulatory oviductal fluid decreases sperm protein kinase A activity, tyrosine phosphorylation, and in vitro fertilization in pig.

Abstract

Molecules from the female reproductive tract modulate capacitation and function of sperm cells in vivo. These molecules vary in a quantitative and qualitative manner throughout the estrous cycle. This work evaluates the effect of using various female reproductive fluids on capacitation and fertilization of pig spermatozoa in vitro. The effects of culturing spermatozoa in different fluids on the levels of sperm protein kinase A (pPKA), tyrosine phosphorylation, acrosome reaction, and in vitro fertilization (IVF) were evaluated. The fluids tested were as follows: oviductal fluid (OF) from five phases of the estrous cycle, namely early and late follicular (OF-EF, OF-LF), early and late luteal (OF-EL, OF-LL) and periovulatory (pOF), follicular fluid from medium-sized follicles, and secretions of cumulus-oocyte complexes (conditioned medium). The pPKAs and tyrosine phosphorylation were decreased by OF-EF, OF-LF, OF-EL, and pOF but not by follicular fluid and conditioned medium. OF-EF, OF-LF, and pOF also decreased the sperm acrosome reaction. Moreover, the effect of pOF on pPKAs and tyrosine phosphorylation was reversible. In in vitro fertilization, OF-EF, OF-LF, OF-EL, and pOF reduced the percentage of penetrated oocytes, the mean number of spermatozoa per penetrated oocyte, and increased monospermy. OF from follicular, early luteal, and periovulatory phases of the estrous cycle modulates the sperm protein phosphorylation as well as the acrosome reaction involved in capacitation and increases monospermic fertilization in in vitro fertilization. Our findings suggest that fluids from the female reproductive tract could be used as additives in porcine IVF systems to modulate sperm-oocyte interaction.