Porcine follicular fluid derived from > 8 mm sized follicles improves oocyte maturation and embryo development during in vitro maturation of pigs.

Ji-Eun Park,Choon-Keun Park,Sang-Hee Lee,Yong Hwangbo

doi:10.1017/s0967199420000398

Abstract

The aim of the present study was to investigate the effects of porcine follicular fluid (pFF) from large-sized (LFF; >8 mm in diameter) and medium-sized (MFF; 3-6 mm in diameter) follicles on the maturation and developmental competence of porcine oocytes. Cumulus-oocyte complexes (COCs) were collected from follicles 3-6 mm in diameter. The collected COCs were incubated for 22 h with LFF or MFF (in vitro maturation (IVM)-I stage) and were incubated subsequently for 22 h with LFF or MFF (IVM-II stage). Cumulus expansion was confirmed after the IVM-I stage and nuclear maturation was evaluated after the IVM-II stage. Intracellular glutathione (GSH) and reactive oxygen species (ROS) levels were measured and embryonic development was evaluated. Relative cumulus expansion and GSH levels were higher in the LFF group compared with in the MFF group after the IVM-I stage (P < 0.05). After the IVM-II stage, the numbers of oocytes in metaphase-II were increased in the LFF group and GSH content was higher in all of the LFF treatment groups compared with in the MFF treatment groups during both IVM stages (P < 0.05). ROS levels were reduced by LFF treatment regardless of IVM stage (P < 0.05). Blastocyst formation and the total numbers of cells in blastocysts were increased in all LFF treatment groups compared with the control group (P < 0.05). These results suggested that pFF from large follicles at the IVM stage could improve nucleic and cytoplasmic maturation status and further embryonic development through reducing ROS levels and enhancing responsiveness to gonadotropins.

Highlights

The in vitro production (IVP) system of porcine embryos is an important technique for production of transgenic pigs used as human disease and xenograft models (Jeon et al, 2014)
Intracellular GSH levels were increased by LFF treatment compared with MFF treatment (P < 0.05), there were no significant differences in reactive oxygen species (ROS) levels between the MFF and LFF groups
Intracellular GSH and ROS levels in porcine oocytes were influenced by LFF treatment during in vitro maturation (IVM)-I and/or IVM-II (Table 2)

Summary

Introduction

The in vitro production (IVP) system of porcine embryos is an important technique for production of transgenic pigs used as human disease and xenograft models (Jeon et al, 2014). Because embryo development and fertility are influenced by oocyte maturation state, in vitro maturation (IVM) is the most important step in IVP for the successful production of embryos. Maturation mediums used in IVM of mammalian oocytes are optimized to culture a variety of cell types and contain different amino acids, inorganic salts, vitamins and other components. Growth factors and hormones are supplied in the culture medium to stimulate cytoplasmic and nuclear maturation of oocytes (Guler et al, 2000), these substances are insufficient for efficient oocyte maturation in the in vitro environment. To improve the low efficiency of IVM, follicular fluid (FF), which supplies nutrients, essential amino acids, and other unknown factors and thereby supports oocyte growth in follicles, is commonly added to the culture medium. Cumulus expansion and nuclear maturation compared with non-treatment groups during IVM were increased by supplementation with pFF (Algriany et al, 2004) and mitochondrial DNA copy numbers were reduced (Mao et al, 2012)

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