Effect of porcine luteinizing hormone on intrafollicular milieu and gene expression in granulosa cells and oocytes in dairy cows

Abstract

In previous research, the use of porcine luteinizing hormone (pLH) in lieu of gonadotropin-releasing hormone (GnRH) for synchronizing ovulation in a fixed-timed artificial insemination protocol in dairy cows improved pregnancy rates (42 vs 28%) without increasing progesterone concentrations. The mechanisms associated with this increase in pregnancy rates are not known. We hypothesized that exposure to pLH alters intrafollicular protein/gene expression compared to GnRH treatment, particularly the oocyte-expressed members of the TGF-β superfamily, and EGF-like growth factor, which regulate oocyte competence. To address this, two studies were conducted to determine whether replacing pLH with GnRH to synchronize ovulation in dairy cows altered intrafollicular milieu and gene expression in mural granulosa cells and oocyte cumulus complexes. The results indicated that the relative abundance of BMP-15, GDF-9 and TGF-β1 were greatly increased in pLH-treated cows. Since these factors promote cumulus expansion and oocyte competence, they may have contributed to the pregnancy increase previously reported.