Effect of Cortisol on Bovine Oocytes Maturation and Further Embryonic Development After In vitro Fertilization

Abstract

Oocyte meiotic maturation and further embryonic development after fertilization is one of the most important physiological requirements for species survival. Herein, the aim of the study was to evaluate the effects of the stressful hormone, cortisol, on the nuclear maturation and further embryonic development of bovine oocytes after in vitro fertilization (IVF). For such purpose, 1,439 immature oocytes were collected from slaughtered cows and matured in vitro for 24 hours with different concentrations of cortisol (0 (control); 50 μM; 150 μM ;250 μM). Afterwards, 412 oocytes were denuded, dyed with aceto-orcein and evaluated for meiotic development. The other 1027 were submitted to IVF and cultured for 9 days, being evaluated on day 2, 6 and 9, for cleavage, morula and blastocyst, respectively. In the control, 85 % of oocytes reached Metaphase II, decreasing to 49, 32 and 15 % for the concentration of the cortisol (50, 150, and 250 μM, respectively). For the embryos, obtained from the oocytes submitted to IVF, in the control group, 28.3 ± 4.8% reached the stage of blastocyst, while for the concentrations of cortisol this value decreased to 22.1 ± 5.4%, 15.4 ± 6.0% and 6.5 ± 2.1% for 50, 150 and 250 μM of cortisol, respectively). Results of the present study clearly demonstrated that animal's stress and particularly high concentrations of cortisol impair bovine nuclear maturation as well as the further embryonic development after IVF.

Glucocorticoids, Stress and Delta-9 Tetrahydrocannabinol (THC) during Early Embryonic Development

“…This finding is consistent with other studies that demonstrated a similar role of ERK1/2 activation, along with AKT and their downstream phosphorylation activity during IVM of mouse and bovine oocytes [13,14,30,75,78]. identified that exposure of immature oocytes to several concentrations of cortisol in the maturation medium resulted in a concentration-dependent decrease in maturation and subsequent cleavage rate [12]. They assessed maturation progression after a 22-24 h period in which oocytes (n = 412) were incubated in cortisol at concentrations of 0 (control), 50, 150 and 250 µM [12].…”

“…Oocytes and follicular diameters were also found to be significantly reduced at all exposure concentrations of cortisol compared to controls. Contrary to da Silva et al (2018) and González et al (2010), the activation rates of oocytes increased when follicles were exposed to 1, 5 and 10 ng/mL cortisol post-culture [17]. However, findings related to oocyte quality and development potential were in support of findings from both earlier studies [12,15].…”

“…On the other hand, a more recent study by Banliat et al (2019), suggested that cortisol altered the phospholipid profiles of bovine oocytes during IVM and embryo development. In contrast to previous studies conducted in the bovine species [12,54], Banliat et al (2019) found that cortisol had no significant effect on in vitro development and only altered blastocyst cryotolerance rather than rate of development [81]. This provides further support for a relationship between cortisol concentrations and lipid content during pre-implantation development.…”

“…The hormonal microenvironment is tightly regulated throughout oocyte maturation, given that oocyte competence, quality, and capacity to produce an embryo can be altered by disruption to such processes [20][21][22]. Given the capacity of both the ECS and glucocorticoids to alter reproductive processes [12,15,23,24,31,34,49,50,54,56,57], it is important to investigate potential interactions between these molecules and their signaling pathways within reproductive tissues. Both glucocorticoids and THC have been shown to influence multiple signaling pathways involved in oocyte and embryo development including extracellular signal-regulated kinase (ERK1/2), cyclic AMP/protein kinase A (cAMP/PKA), Protein kinase B (PKB)/AKT, and mitogen-activated protein kinases (MAPK) p38 [12][13][14]30,58] (Figure 1).…”

“…They assessed maturation progression after a 22-24 h period in which oocytes (n = 412) were incubated in cortisol at concentrations of 0 (control), 50, 150 and 250 µM [12]. Therefore, the differences in the degree of inhibition found between Gonzalez et al (2010) and da Silva et al (2018) are likely due to the use of different concentrations of cortisol exposure or species differences in the regulation of oocyte maturation. Matured oocytes employed for IVF (n = 1027) displayed a negative dosedependent response to cortisol, where fewer embryos progressed to the blastocyst stage when higher cortisol concentrations were present during maturation.…”