In vitro maturation on an agarose matrix improves the developmental competence of porcine oocytes

Abstract

Oocytes in vivo generally mature in ovarian follicles that are soft, whereas oocytes that mature in vitro are on the hard surface of culture dishes. Embryonic ontogeny through organogenesis has greater ability in in vivo matured oocytes than it does in in vitro matured oocytes, indicating the importance of a soft culture matrix. In this study, we report the effect of using an agarose matrix as a culture substrate on the development of pig oocytes derived from medium antral follicles. The cumulus-oocyte complexes (COCs) retrieved from medium antral follicles were matured on noncoated (control) culture dishes or dishes coated with 1% and 2% (w/v) agarose matrices. Subsequently, the effect of the soft culture matrix on the developmental competence of porcine oocytes was assessed by analyzing cumulus expansion, blastocyst formation after parthenogenetic activation (PA), gene expression levels (ACTN4, BMP15, BAX, HIF1A, PFKP and VEGFA), TUNEL indices, BMP15 protein expression levels, cortical granule (CG) distribution, and intraoocyte ATP levels. In vitro maturation (IVM) of pig COCs using a 1% (w/v) agarose matrix resulted in significantly higher blastocyst formation, cumulus expansion, gene expression of BMP15, HIF1A and VEGFA, protein expression of BMP15, and intraoocyte ATP levels, and there was significantly reduced expression of a pro-apoptotic gene and ACTN4 gene and a reduction in TUNEL indices. These results demonstrate that the developmental competence of porcine oocytes can be effectively improved through IVM on a soft culture matrix made of agarose over what is observed using hard culture dishes.

Keywords: Agarose; Embryonic development; Microenvironment; Oocyte maturation; Stiffness.