Effect of the Bovine Oviductal Fluid on In Vitro Fertilization, Development and Gene Expression of In Vitro-Produced Bovine Blastocysts

Oviductal microenvironment generally provides better conditions for early embryo development than the conventional in vitro system. In an attempt to simulate the oviduct conditions or the main potentially influencing factors, the effect was studied of a bovine oviductal fluid (bOF) treatment applied prior to IVF on (i) IVF parameters, (ii) cleavage rate, (iii) blastocyst yield and (iv) blastocyst quality. Embryo quality was assessed by morphological embryo quality and relative transcript abundance of several developmental genes in bovine blastocysts. Furthermore, to study the effect of bOF without the male effect and zonasperm interaction, artificially activated metaphase II oocytes were also treated with bOF. In vitro-matured bovine oocytes from abattoir ovaries were treated or untreated with bOF for 30min and then washed prior to IVF or activation. Subsequently, in vitro-fertilized and parthenogenetic embryos were in vitro cultured for 7 to 8days. The bOF treatment had no effect on fertilization parameters, cleavage, blastocyst rates both on parthenogenetic and IVF bovine embryos and neither on morphological quality of IVF blastocysts. G6PD and SOD2 genes from IVF blastocysts showed significant changes in their expression after a bOF treatment. Significant differences were found for the expression of SCL2A1, GPX1, BAX, AKR1B1 and PLAC8 genes between excellent or good blastocysts (Grade 1) and fair blastocysts (Grade 2). To our knowledge, this is the first study that evaluates the effect of bOF oocyte treatment on fertilization parameters, development and quality of bovine embryos.