Conjugated linoleic acid improves meiotic spindle morphology and developmental competence of heat-stressed bovine oocyte

Abstract

This study was conducted to elucidate the effects of introducing conjugated linoleic acid (CLA) on meiotic spindle organization of heat stressed (HS) matured oocytes and the resulting blastocysts DNA methylation as well as the expression of the genes involved in DNA methylation (DNMT3a, DNMT3b and DNMT1). Immature bovine oocytes were cultured at 41 °C for the first 12 h and 38.5 °C for the second 12 h of maturation time in the presence of 0 and 50 μM of CLA (HS and HS + CLA groups, respectively). A group of oocytes cultured in medium with no CLA supplementation at normal temperature (38.5 °C for 24 h) was considered as negative control (C). Percentage of normal spindle, and cleavage and blastocyst rates were significantly decreased in the HS group compared to the C group (P < 0.05). The global DNA methylation and expression level of DNMT3a gene were increased in HS group compared to the C groups (P < 0.05), while the expression level of DNMT3b was decreased. The CLA supplementation improved the percentage of normal microtubules shape in MII oocytes as well as the developmental competence in the HS + CLA group compared to the HS group (P < 0.05). However, global DNA methylation and expression level of DNMT3a/b were not ameliorated by CLA supplementation (P > 0.05). Based on the obtained results, CLA proved to be capable of improving the oocyte developmental competence as well as decreased the aberrant spindle organization of heat-stressed oocytes and it would not cause epigenetic alteration in the obtained blastocysts.