Capacitation status and in vitro fertility of boar spermatozoa: effects of seminal plasma, cumulus‐oocyte‐complexes‐conditioned medium and hyaluronan

Abstract

In the present study, the effects of seminal plasma (SP), cumulus-oocyte-complexes (COCs) conditioned medium (CCM) and hyaluronan (HA) on functional changes and in vitro fertilizing ability of porcine spermatozoa were examined. In in vitro fertilization (IVF) experiments, 10% (v/v) of exogenous SP in the fertilization medium prevented sperm penetration (using fresh-extended and frozen-thawed ejaculated spermatozoa). Analysis of frozen-thawed CCM revealed a HA content to levels of 30 ng/mL per incubated COC. Presence of frozen-thawed CCM did not, however, prove effective to increase (furthermore decreasing) oocyte penetration in vitro, and neither did supplementation with exogenous HA at the same concentration as that present in the CCM (secreted by COCs). Analysis of sperm capacitation using the chlortetracycline (CTC) assay showed that frozen-thawed CCM had no elevating effect on 'B-pattern' spermatozoa (implying capacitation-like changes) and that addition of 10% (v/v) SP held spermatozoa in the 'F-pattern' (intact) status. Dose of 500 microg/mL HA and freshly prepared CCM increased, however, the frequency of capacitated spermatozoa (B-pattern) without resulting in increased rates of 'AR-pattern' (acrosome-reacted) spermatozoa, compared with controls. The present results confirm the decapacitating effect of SP and suggest capacitating actions of HA (dose-related) and CCM (freshly prepared) on boar spermatozoa in vitro. The unclear effects of frozen-thawed CCM and a low dose of HA on penetration rates of boar spermatozoa call for further researches of their function in vivo.