In vitro maturation using αMEM with reduced NaCl enhances maturation and developmental competence of pig oocytes after somatic cell nuclear transfer

Abstract

Background Compared to medium containing 108 mM sodium chloride (NaCl), in vitro maturation (IVM) using a simple medium with reduced (61.6 mM) NaCl increases the cytoplasmic maturation and embryonic development of pig oocytes. Objectives This study determines the effect of a complex medium containing reduced NaCl on the IVM and embryonic development of pig oocytes. Methods Pig oocytes were matured in Minimum Essential Medium Eagle-alpha modification (αMEM) supplemented with 61.6 (61αMEM) or 108 (108αMEM) mM NaCl, and containing polyvinyl alcohol (PVA) (αMEMP) or pig follicular fluid (PFF) (αMEMF). Medium-199 (M199) served as the control for conventional IVM. Cumulus cell expansion, nuclear maturation, intra-oocyte glutathione (GSH) contents, size of perivitelline space (PVS), and embryonic development after parthenogenesis (PA) and somatic cell nuclear transfer (SCNT) were evaluated after IVM. Results Regardless of PVA or PFF supplementation, oocytes matured in 61αMEM showed increased intra-oocyte GSH contents and width of PVS ( p < 0.05), as well as increased blastocyst formation ( p < 0.05) after PA and SCNT, as compared to oocytes matured in 108αMEMP and M199. Under conditions of PFF-enriched αMEM, SCNT oocytes matured in 61αMEMF showed higher blastocyst formation ( p < 0.05), compared to maturation in 108αMEMF and M199, whereas PA cultured oocytes showed no significant difference. Conclusions IVM in αMEM supplemented with reduced NaCl (61.6 mM) enhances the embryonic developmental competence subsequent to PA and SCNT, which attributes toward improved oocyte maturation.