Oxygen tension during in vitro oocyte maturation and fertilization affects embryo quality in sheep and deer

Abstract

Incubation gas atmosphere affects the development of in vitro produced embryos. In this study, there was examination of effects of two different oxygen (O₂) tensions (5 % and 21 %) during in vitro maturation (M5 and M21) and/or fertilization (F5 and F21) on embryo production and quality in deer and sheep. There was assessment of the percentage of embryos with cell cleavage occurring, percentage that developed to the blastocyst stage, and analysis of the relative abundance of mRNA transcript for genes important for development to the blastocyst stage. The O₂ tension treatment did not affect (P > 0.05) percentage cleavage or blastocyst development in either species. In sheep, there was a greater abundance of SHC1, GPX1, TP53, BAX and NRF1 mRNA transcript (P < 0.05) in M21 F5-derived embryos. In deer, there was a greater abundance of SOD2 mRNA transcript (P < 0.05) when oocytes had been matured under relatively lesser O₂, regardless of the tension used during fertilization. There was a lesser abundance of SOX2 mRNA transcript (P < 0.05) in the M5F21 compared to the other three treatment groups. The AKR1B1 mRNA transcript was in greater abundance (P < 0.05) in M21 F21 as compared to M21 F5 and M5F21 group, and there was a greater abundance PLAC8 mRNA transcript (P < 0.05) in M21 F21, as compared to all other treatment groups. In conclusion, while O₂ tension had no effect on developmental rates it did affect the relative abundance of mRNA transcript of multiple genes related to important cell functions during development.

Keywords: Deer; In vitro fertilization; In vitro maturation; Oxygen tension; Sheep.