Anti-bacterial factors secreted from cumulus cells of ovulated COCs enhance sperm capacitation during in vitro fertilization.

Problem: The aim of this study was to find immune-related genes expressed in cumulus cells of ovulated cumulus oocyte complexes (COCs) and to clear the functional roles during fertilization process.

Method Of Study: Ovulated COCs were collected from oviduct 16 hr after the hCG injections followed by eCG priming. The cumulus cells were used for RT-PCR or western blotting study. COCs were also used for in vitro fertilization study.

Results: Cramp, Trf, Lyz2, S100a8, and S100a9 were expressed in cumulus cells during ovulation process. The protein levels of CRAMP or transferrin were detected in ovulated COCs and then secreted into hyaluronan-rich matrix. The high dose of these factors reduced the proliferative activity of E. coli; however, the lower levels of them significantly increased the rate of fertilization in in vitro via the induction of sperm capacitation.

Conclusion: Cumulus-secreted anti-bacterial factors act on sperm to induce sperm capacitation.