The Effects of Heat Shock Protein 70 Addition in the Culture Medium on the Development and Quality of In Vitro Produced Heat Shocked Bovine Embryos

Abstract

The aims of the present study were to examine the effects of HSP70 addition in the in vitro culture medium of day 3 embryos on their developmental competence and quality. Bovine oocytes (n = 1442) were in vitro matured, inseminated and cultured for the first two days according to standardized methods. The presumptive zygotes were randomly allocated in three experimental groups: Control, C (embryos cultured at 39 °C throughout the culture period), group C41 (temperature was raised to 41 °C from the 48th to 72nd h post insemination (p.i.) and then it returned at 39 °C for the remaining culture period), and group H41 (the temperature modification was the same as in C41 and during heat exposure, HSP70 was added in the culture medium). Cleavage and embryo yield were assessed 48 h p.i. and on days 7, 8, 9, respectively and gene expression in day 7 blastocysts was assessed by RT-PCR. Blastocyst yield was the highest in group C39; and higher in group H41 compared to group C41. From the gene expression analyses, altered expression of 11 genes was detected among groups. The analysis of the orchestrated patterns of gene expression differed between groups. The results of this study confirm the devastating effects of heat stress on embryo development and provide evidence that HSP70 addition at the critical stages can partly counterbalance, without neutralizing, the negative effects of the heat insult on embryos, acting mainly through mechanisms related to energy deployment.

Heat Stress: A Serious Disruptor of the Reproductive Physiology of Dairy Cows

“…The HSP70-primed embryos developed into blastocysts in a significantly higher proportion compared to the non-primed controls. However, they still they lagged behind compared to the non-stressed controls [181]. In conjunction with the findings on the effect of HS on the maturing oocyte, these findings are indicative of two phenomena: first, the endogenous synthesis of HSPs is not sufficient for the early embryo to withstand thermal stress, and second, interventions during oocyte maturation stages are more efficient and appear to persist until the blastocysts stage.…”

“…Nevertheless, there is an agreement that the further developmental competence of these oocytes is seriously affected, as blastocyst formation rates from heat stressed oocytes are significantly suppressed. After exposure of COCs to increased temperature during in vitro maturation, a reduced embryo yield has been reported in many studies [18,54,[179][180][181][182]. In most of these studies, the heat exposure lasted for 12 to 24 h. We have shown that only six hours exposure (from the second to the eighth hour of IVM) of in vitro matured COCs to 41 • C is sufficient to cause significant reduction in cleavage and blastocyst formation rates [54].…”

“…However, it attenuates the negative effects of HS on oocyte maturation and restores the yield of blastocysts to levels close to those of oocytes matured at thermoneutral conditions [118]. The external addition of HSP70 reduces the expression of the endogenous HSPs, both in control and heat stress conditions, while increasing the expression of antioxidants as well as anti-apoptotic genes (SOD2, GPX1, BCL2) in oocytes [181]. These changes contribute to cellular protection against the stressors and are associated with improved oocyte viability and competence.…”

Heat Shock Protein 70 and Its Role in Alleviating Heat Stress and Improving Livestock Performance

“…A study conducted on dairy cattle by Cai et al [54] revealed that cattle with AC genotype expressed more HSP70 mRNA at 37.5 °C and showed lower levels of apoptosis in lymphocytes of peripheral blood. The effect may occur because HSP repairs proteins and inhibits apoptosis in damaged cells by preventing caspase 3 activation and reducing cellular protein synthesis [55,56]. In addition, single nucleotide polymorphisms (SNPs) (g.895 C/-and g.1128 G/T) in the 5'-UTR region of inducible HSP70.1 alleviate heat stress response during the exposure to heat stress at 43 °C in lactating Holstein cows [57].…”