The Combined Effects of Recombinant Human Oviductin (rHuOVGP1) and Progesterone on Tyrosine Phosphorylation of Sperm Proteins

Abstract

Worldwide, around 15% of couples who seek to conceive suffer from infertility. Assisted reproductive technology (ART) would have never been possible without research endeavors. However, to further improve the fertilization rates of ART procedures, there is still more to be done. The mammalian oviductal cells synthesize and secrete a major glycoprotein know as oviductin, or oviduct-specific glycoprotein (OVGP1). This protein has been implicated in enhancing sperm capacitation, sperm motility, sperm penetration and fertilization. Our lab has successfully produced recombinant human oviductin (rHuOVGP1), which has been shown to enhance tyrosine phosphorylation of sperm proteins, a biochemical hallmark of capacitation that takes place in the sperm tail. Additionally, the sex hormone progesterone (P4) has been implicated in increasing the influx of calcium ions through the CatSper channel which is similarly located in the sperm tail and is an important aspect of capacitation. Here we performed a study in the hope of gaining a better understanding of the mechanism of sperm capacitation by examining if rHuOVGP1 works synergistically with P4 to regulate tyrosine phosphorylation of sperm proteins during capacitation. Fresh sperm samples were processed and capacitated at different time points in the absence or presence of rHuOVGP1 (50 mg/mL) with or without P4. The results obtained indicate that both rHuOVGP1 and P4 can enhance tyrosine phosphorylation of sperm proteins, however, the best result was obtained when rHuOVGP1 was used in combination with P4. The addition of rHuOVGP1 with P4 to the capacitation medium may improve the fertilization rates of ART procedures.