Cellular and Molecular Adaptation of Bovine Granulosa Cells and Oocytes under Heat Stress

Abstract

Heat stress has long been recognized as a challenging issue that severely influences the reproductive functions of dairy cattle, disrupting oocyte development during fetal growth. These detrimental effects of heat stress are the result of either the hyperthermia associated with heat stress or the physiological adjustments made by the heat-stressed animal to regulate body temperature. In addition, elevated temperatures have been implicated in increasing the production of reactive oxygen species. Thus, understanding the impact of heat stress on reproductive functions, from a cellular to molecular level, might help in selecting heat-resilient dairy cattle and developing heat stress mitigation strategies. In the present paper, we have attempted to describe the changes in the reproductive system and function of dairy cattle in response to heat stress by reviewing the latest literature in this area. The review provides useful knowledge on the cellular and genetic basis of oocyte and granulosa cells in heat-stressed dairy cattle, which could be helpful for future research in this area.

Effects of Heat Stress on Bovine Oocytes and Early Embryonic Development—An Update

“…Heat stress leads to oxidative stress and apoptosis through the intracellular accumulation of reactive oxygen species (ROS). Research suggests that the upregulation of superoxide dismutase 2 (SOD) and catalase (CAT) may regulate forkhead box O3 (FOXO3) and kelch-like ECH-associated protein 1 (KEAP1) in granulosa cells, thereby inhibiting ROS synthesis [ 17 ]. As a result of heat stress, transcriptional changes in GCs have also been observed, including an increase in the synthesis of HSP70, HSP90, HSP27 and HSP60 [ 42 ].…”

“…Heat stress may induce epigenetic disturbances, which might impact the expression of HSP70 , which is considered a candidate heat stress biomarker [ 7 ]. The two-cell embryo is very sensitive to heat stress and may increase the transcription of Hsp70 Member 1A (HSPA1A) , Heat Shock Protein beta-1 (HSPB1) , and the synthesis of HSP70 , when exposed to HS [ 17 ].…”

“…Inappropriate cooling systems cause an increase in cows’ internal temperature during summer, leading to—among others—reduced fertility [ 17 ]. Heat stress indirectly reduces the fertility of cattle by inducing hormonal changes, affecting the uterine environment; as well as directly, causing a negative impact on oocytes and embryos [ 18 ].…”

Grado de desarrollo del folículo preovulatorio y su relación con el tamaño del cuerpo lúteo y la producción de progesterona en las razas Romosinuano (RS) y Brahman (Br)T0

“…Las CG son células somáticas y se consideran el tipo de células ováricas más importantes que rodean, apoyan y nutren al ovocito en desarrollo y proporcionan un microambiente adecuado para su maduración (Edson et al 2009); se han resaltado diversos pasos transcripcionales que las CG deben completar antes de la ovulación y se han identificado transcriptos asociados con el estado de competencia del ovocito (Gilbert 2011); cualquier alteración de la calidad de las CG y su capacidad de proliferación también puede tener efectos sobre el desarrollo del folículo y puede interrumpir la maduración de los ovocitos y, en consecuencia, dar lugar a un desarrollo embrionario deteriorado con resultados insatisfactorios, revisado por Khan et al 2020. En consecuencia, una mayor comprensión de los eventos fisiológicos que suceden en cada uno de los compartimientos foliculares en las diferentes etapas de foliculogénesis permitirá una mejora no solo en la intervención de esos procesos con fines productivos, sino que facilitará avances en los resultados de los procedimientos biotecnológicos aplicados a la reproducción de los animales domésticos de interés zootécnico, particularmente en bovinos de las razas RS (raza criolla colombiana en peligro de extinción) y Br (raza de gran participación en la ganadería colombiana), en las cuales a la fecha no se han estudiado.…”

RNAi-Mediated Silencing of Catalase Gene Promotes Apoptosis and Impairs Proliferation of Bovine Granulosa Cells under Heat Stress

“…Moreover, the recovery of fertility during the autumn months is significantly delayed after the period when the environmental temperatures are highest during the summer months, showing that HS may have long-lasting effects on reproductive processes [3][4][5]. There is considerable evidence that HS impairs folliculogenesis, granulosa cell (GC) functions, and oocyte maturation, comprising reduced hormone synthesis, increased oxidative stress and apoptosis, and disrupted mitochondrial function [6][7][8][9][10][11][12].…”