Physiological and molecular aspects of heat-treated cultured granulosa cells of Egyptian buffalo (Bubalus bubalis)

Vitamin C Alleviates the Negative Effects of Heat Stress on Reproductive Processes by Regulating Amino Acid Metabolism in Granulosa Cells

Heat stress-induced biochemical alterations in ovarian follicles compromise the function of granulosa cells (GCs) and the developmental competence of oocytes. Summer heat stress can have a far-reaching negative impact on overall fertility and reproductive success. Together with the heat stress, the rise of assisted reproductive technologies (ART), potential confounding hazards of in vitro handling and the absence of systemic body support in ART makes it imperative to study the heat stress ameliorative effects of vitamin C under in vitro conditions. Using in vitro heat stress treatment of 43 °C for two hours in bovine GCs, we studied the effects of vitamin C on cell growth, oxidative stress, apoptosis and cell cycle progression together with a comprehensive metabolomics profiling. This study investigates the molecular milieu underlying the vitamin C (VC)-led alleviation of heat-related disruptions to metabolic processes in bovine GCs. The supplementation of VC ameliorated the detrimental effects of heat stress by reducing oxidative stress and apoptosis while restoring cell proliferation. Normal cell function restoration in treated GCs was demonstrated through the finding of significantly high levels of progesterone. We observed a shift in the metabolome from biosynthesis to catabolism, mostly dominated by the metabolism of amino acids (decreased tryptophan, methionine and tyrosine) and the active TCA cycle through increased Succinic acid. The Glutathione and tryptophan metabolism were important in ameliorating the inflammation and metabolism nexus under heat stress. Two significant enzymes were identified, namely tryptophan 2,3-dioxygenase (TDO2) and mitochondrial phenylalanyl-tRNA synthetase (FARS2). Furthermore, our findings provide insight into the significance of B-complex vitamins in the context of heat stress during VC supplementation. This study underscores the importance of VC supplementation in heat stress and designates multiple metabolic intervention faucets in the context of ameliorating heat stress and enhancing reproductive efficiency.

Molecular, enzymatic responses and in vitro embryonic developmental competency of heat-shocked buffalo embryos co-cultured with granulosa cells monolayer

The present study was designed to establish a suitable alternative approach to mitigate the adverse effect of high culture temperature on in vitro embryo development and the related molecular response in buffalo. Pre-cultured granulosa cells (GCs) were used as a monolayer during in vitro embryo culture until day 8 (day of fertilization = D0). Post fertilization, presumptive embryos were randomly assigned into two culture conditions: embryos cultured in the presence of GCs monolayer under normal culture temperature (N: 38.5 °C; GEN group) or heat shock (H: 40.5 °C; GEH group) and their counterpart groups of embryos cultured without GCs (EN and EH groups). Additionally, two groups of GCs monolayer were cultured without embryos up to day 8 under 38.5 °C (GN) or 40.5 °C (GH) for further spent culture media enzymatic analyses. Heat shock was administered for the first 2 h of culture then continued at 38.5 °C until day 8. The results indicated that under heat treatment, GCs enhanced (P ≤ 0.05) embryo cleavage and development (day 8) rates, which were comparable to the embryos cultured at 38.5 °C. On the molecular level, blastocysts of the GEH group showed similar expressions of metabolism-regulating genes (CPT2 and SlC2A1/GLUT1) and an antioxidant gene (SOD2) when compared to the blastocysts of the EN group. The relative expression of HSP90 was significantly up-regulated under heat shock and/or co-culture conditions. However, HSF1 expression was increased (P ≤ 0.05) in the GEH group. No statistical differences were observed among the study groups for the pluripotency gene NANOG, and stress resistance transcript NFE2L2. Regarding the enzymatic profile, the concentrations of SOD, total protein, and MDA were decreased (P ≤ 0.05) in the GEH group compared to the cultured GCs without embryos (GH group). In conclusion, GCs as a monolayer have a beneficial impact on alleviating heat stress at the zygote stage through the regulatory mechanisms of metabolic activity, defense system, and heat shock response genes.

Adaptive and Biological Responses of Buffalo Granulosa Cells Exposed to Heat Stress under In Vitro Condition

Simple Summary

The pertinent consequences of global warming substantially affect both animal productivity and fertility. Noteworthy, tropical and subtropical animal breeds are productively suited to hot climate conditions. Therefore studying the physiological changes accompanying high temperature, especially in tropically adapted species such as buffalo, will help in understanding the mechanisms that the animal use to accomplish the necessary functions efficiently. Concerning fertility-related activity, granulosa cells are important for the regulation of ovarian function and the completion of oocyte maturation. In this study, the buffalo granulosa cells were examined for their viability, physiological and molecular responses under in vitro heat stress conditions. Buffalo granulosa cells displayed different adaptive responses, at the physiological and molecular levels, to the different heat stress conditions. At 40.5 °C, granulosa cells exhibited a functional persistence compared to the control and other heat-treated groups. These results will provide insights into ways that tropically adapted breeds may be able to maintain better reproductive function when exposed to heat stress compared to temperate breeds.

Abstract

The steroidogenesis capacity and adaptive response of follicular granulosa cells (GCs) to heat stress were assessed together with the underlying regulating molecular mechanisms in Egyptian buffalo. In vitro cultured GCs were exposed to heat stress treatments at 39.5, 40.5, or 41.5 °C for the final 24 h of the culture period (7 days), while the control group was kept under normal conditions (37 °C). Comparable viability was observed between the control and heat-treated GCs at 39.5 and 40.5 °C. A higher release of E2, P4 and IGF-1 was observed in the 40.5 °C group compared with the 39.5 or 41.5 °C groups. The total antioxidant capacity was higher in response to heat stress at 39.5 °C. At 40.5 °C, a significant upregulation pattern was found in the expression of the stress resistance transcripts (SOD2 and NFE2L2) and of CPT2. The relative abundance of ATP5F1A was significantly downregulated for all heat-treated groups compared to the control, while TNFα was downregulated in GCs at 39.5 °C. Expression analyses of stress-related miRNAs (miR-1246, miR-181a and miR-27b) exhibited a significant downregulation in the 40.5 °C group compared to the control, whereas miR-708 was upregulated in the 39.5 and 40.5 °C groups. In conclusion, buffalo GCs exhibited different adaptive responses, to the different heat stress conditions. The integration mechanism between the molecular and secretory actions of the GCs cultured at 40.5 °C might provide possible insights into the biological mechanism through which buffalo GCs react to heat stress.