Effect of chondroitin sulfate C on sperm capacitation and fertilization parameters in vitro in pigs

The objective of this study was to determine the effects of chondroitin sulfate C (CS-C) on sperm capacitation and fertilization parameters in vitro in pigs. Frozen–thawed ejaculated pig sperm (semen S-484) were incubated with fertilization medium containing CS-C (0–2 mg/ml) for 1 h and the capacitation rate with chlorotetracycline (CTC) assay was examined, which showed that CS-C increased the rate of incapacitation F pattern spermatozoa converted to capacitation B pattern sperm cell in concentration-dependent manner and mostly increased capacitation B pattern sperm cell and decreased acrosome reaction AR pattern sperm cell in 1 mg/ml concentration. When sperm was incubated for 1, 2 and 4 h in fertilization medium containing 1 mg/ml CS-C, it showed that the capacitated B pattern sperm cell was significantly (p < 0.01) increased and the AR pattern sperm cell was significantly decreased at each time point in the presence than in the absence of CS-C. For identifying the validity of CS-C in sperm capacitation, sperm–oocyte was inseminated in fertilization medium containing CS-C (0–2 mg/ml) and the rate of fertilized oocytes was examined, which showed that the penetration rates significantly (p < 0.05) increased from 0.5 to 1.0 mg/ml concentrations (87.4–96.3%) compared with control (74.9%). For identifying the universality of CS-C in sperm capacitation, four different semens (boar S-484, S-454, D-815 and D-748) were incubated in fertilization medium containing CS-C (1 mg/ml) for 2 h, respectively, which showed that CS-C increased the rate of capacitation B pattern sperm cell and decreased acrosome reaction AR pattern sperm cell in each semen. And it showed that CS-C yielded a higher promote effect (93.9%, 83.9%, 60.7% and 44.9%, respectively) on sperm penetration compared to unaddition control (63.4%, 22.0%, 3.3% and 3.3%, respectively). Sperm–oocyte binding analysis showed that CS-C increased the number of sperm bound to oocyte compared unaddition control in each semen. These results suggested that CS-C is the efficient factor on sperm capacitation in pigs, CS-C may promote sperm from the incapacitated to capacitated state and sequentially prevent sperm from spontaneous acrosome reaction, and thus facilitate the sperm–zona binding and sperm penetration to oocyte.