Effect of superstimulatory treatments on the expression of genes related to ovulatory capacity, oocyte competence and embryo development in cattle

Abstract

Multiple ovulation (superovulation) and embryo transfer has been used extensively in cattle. In the past decade, superstimulatory treatment protocols that synchronise follicle growth and ovulation, allowing for improved donor management and fixed-time AI (FTAI), have been developed for zebu (Bos indicus) and European (Bos taurus) breeds of cattle. There is evidence that additional stimulus with LH (through the administration of exogenous LH or equine chorionic gonadotrophin (eCG)) on the last day of the superstimulatory treatment protocol, called the 'P-36 protocol' for FTAI, can increase embryo yield compared with conventional protocols that are based on the detection of oestrus. However, inconsistent results with the use of hormones that stimulate LH receptors (LHR) have prompted further studies on the roles of LH and its receptors in ovulatory capacity (acquisition of LHR in granulosa cells), oocyte competence and embryo quality in superstimulated cattle. Recent experiments have shown that superstimulation with FSH increases mRNA expression of LHR and angiotensin AT(2) receptors in granulosa cells of follicles >8 mm in diameter. In addition, FSH decreases mRNA expression of growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) in oocytes, but increases the expression of both in cumulus cells, without diminishing the capacity of cumulus-oocyte complexes to generate blastocysts. Although these results indicate that superstimulation with FSH is not detrimental to oocyte competence, supplementary studies are warranted to investigate the effects of superstimulation on embryo quality and viability. In addition, experiments comparing the cellular and/or molecular effects of adding eCG to the P-36 treatment protocol are being conducted to elucidate the effects of superstimulatory protocols on the yield of viable embryos.

Transcriptional profiles of bovine in vivo pre-implantation development

“…Readers are cautioned, however, that the in vivo oocytes/embryos used here were generated after superovulation treatment. Although superovulation can affect gene expression of oocytes/embryos [44–47], it is frequently used in both research and production [48] because naturally ovulated/developed oocytes/embryos from single-ovulatory, large animals such as cattle are not very feasible. Nonetheless, the ultimate “gold standards” for gene expression during bovine pre-implantation development can only be established using naturally ovulated/developed oocytes/embryos.…”

Granulosa cell function and oocyte competence: Super-follicles, super-moms and super-stimulation in cattle

“…The superstimulation protocol used in this study included exogenous administration of FSH over 4 days after follicular wave synchronization and LH 24 h after progesterone-device removal. Therefore, previously documented biomarker genes of early-and late-LH response (those related to vascularization, lipid synthesis, protein localization and intracellular transport) were expected to be already upregulated (Gilbert et al, 2011(Gilbert et al, , 2012Barros et al, 2012). The transcriptomic profile of granulosa cells after superstimulation, however, displayed up-regulation of only a few markers of the LH surge compared to granulosa cells from natural dominant follicles; differentially expressed genes were related to matrix remodeling (i.e., tissue proliferation), disturbance of angiogenesis, apoptosis, and oxidative stress response (Fig.…”

Prostaglandin receptors (EP2 and EP4) and angiotensin receptor (AGTR2) mRNA expression increases in the oviducts of Nelore cows submitted to ovarian superstimulation

“…Portela et al (2008) observed increased levels of AGTR2 mRNA in bovine granulosa cells cultured with FSH. Similarly, Barros et al (2013) demonstrated that the P-36 and P-36/eCG protocols increased the abundance of AGTR2 mRNA in bovine granulosa cells in vivo. The isthmus is known to be a sperm storage reservoir (Hunter and Wilmut, 1984), and studies have found ACE activity in ejaculate, which may modulate the local activity of Ang II and Please cite this article in press as: Fontes, P.K., et al, Prostaglandin receptors (EP2 and EP4) and angiotensin receptor (AGTR2) mRNA expression increases in the oviducts of Nelore cows submitted to ovarian superstimulation.…”