Effects of the porcine oviduct-specific glycoprotein on fertilization, polyspermy, and embryonic development in vitro

This study evaluated the effects of porcine oviduct-specific glycoprotein ( pOSP) on in vitro fertilization (IVF), polyspermy, and development to blast ocyst. Experiment 1 evaluated the effects of various concentrations (0-100 mu g/ml) of purified pOSP on fertilization parameters, including penetratio n, polyspermy, male pronuclear formation, and mean number of sperm penetrat ed per oocyte. Experiment 2 examined the ability of an anti-pOSP immunoglob ulin G to inhibit the observed effects of pOSP on fertilization parameters. Experiments 3 and 4 examined various concentrations of pOSP (0-100 mu g/ml ) on zona pellucida solubility and sperm binding, respectively. Lastly, exp eriment 5 assessed the effects of various concentrations of pOSP (0-100 mu g/ml) on the in vitro embryo cleavage rate and development to blastocyst. P ig oocytes matured and fertilized in vitro were used for all experiments. A n effect of treatment (P < 0.05) was detected for pOSP on penetration, poly spermy, and mean number of sperm per oocyte. Concentrations for pOSP of 0-5 0 mu g/ mi had no effect on sperm penetration rates; however, compared with the control, 100 mu g/ml significantly decreased the penetration rate (74% vs. 41%). Addition of 10-100 mu g/ml significantly reduced the polyspermy rate compared with the control (61% vs. 24-29%). The decrease in polyspermy achieved by addition of pOSP during preincubation and IVF was blocked with a specific antibody to pOSP. No effect of treatment was observed on zona d igestion time relative to the control; however, the number of sperm bound t o the zona pellucida was significantly decreased by treatment (P < 0.05). C ompared with the control, all concentrations of pOSP examined reduced the n umber of sperm bound per oocyte (45 vs. 19-34). A treatment effect (P < 0.0 5) was observed for pOSP on embryo development to blastocyst but not on cle avage rates. Addition of pOSP during preincubation and fertilization signif icantly increased postcleavage development to blastocyst, but a synergistic stimulation on development was not detected when pOSP was included during in vitro culture. These results indicate that exposure to pOSP before and d uring fertilization reduces the incidence of polyspermy in pig oocytes, red uces the number of bound sperm, and increases postcleavage development to b lastocyst.