Effects of synthetic polymers on in vitro maturation of sheep oocytes and subsequent developmental capacity after parthenogenetic activation or fertilization

Abstract

There are few studies considering functional roles of synthetic polymers on small ruminant oocytes matured in vitro. In this study, the effects of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) on in vitro maturation of sheep oocytes were evaluated and compared in order to determine whether synthetic polymers can replace serum and be used for in vitro maturation of sheep oocytes. Simultaneously, the effects of synthetic polymers presented in the maturation medium on subsequent embryonic development were also assessed. Sheep cumulus−oocyte complexes were cultured in the maturation medium supplemented with 10% fetal bovine serum (FBS), 3mg/ml PVP, or 1mg/ml PVA, respectively. The rates of oocyte maturation and embryonic development after parthenogenetic activation (PA) or in vitro fertilization (IVF) were recorded. The data indicated that the presence of PVP in the maturation medium does not have any negative effects on sheep oocytes matured in vitro when compared to FBS, as concern oocyte maturation and subsequent embryonic developmental capacity. Additionally, after PA, the embryonic developmental capability of in vitro matured sheep oocytes in the presence of PVA was not significantly different from that of oocytes matured in the presence of FBS or PVP. By contrast, when PVA was added to the maturation medium, the blastocyst formation rate after IVF (28.05%±5.42%) was significantly lower than that of oocytes matured in the presence of FBS (36.33±4.37%, P<0.05) or PVP (38.94±5.19%, P<0.05). However, there were no significant differences in the oocyte cleavage rate among the three groups. Additionally, the embryonic developmental capacity in the PVP group were similar to those in the FBS group (P>0.05). In conclusion, synthetic polymer as a serum replacement can efficiently maintain the procedure of oocyte maturation and subsequent embryonic developmental capacity in sheep. The PVP is more beneficial to in vitro maturation of sheep oocytes compared to PVA.