Thermotolerance of IVM-derived bovine oocytes and embryos after short-term heat shock

Abstract

A series of experiments were designed to study the effect of elevated temperatures on developmental competence of bovine oocytes and embryos produced in vitro. In experiment 1, the effect of heat shock (HS) by a mild elevated temperature (40.5°C) for 0, 30, or 60 min on the viability of in vitro matured (IVM) oocytes was tested following in vitro fertilization (IVF) and culture. No significant difference was observed between the control (39°C) and the heat‐treated groups in cleavage, blastocyst formation, or hatching (P > 0.05). In experiment 2, when the HS temperature was increased to 41.5°C, neither the cleavage rate nor blastocyst development was affected by treatment. However, the rate of blastocyst hatching appeared lower in the HS groups (13% in control group vs. 3.9% and 5.6% in 30 min and 60 min, respectively; P < 0.05). When IVM oocytes were treated at 43°C prior to IVF (experiment 3), no difference was detected in blastocyst and expanded blastocyst development following heat treatment for 0, 15, or 30 min, but heat treatment of oocytes for 45 or 60 min significantly reduced blastocyst and expanded blastocyst formation (P < 0.05). In experiment 4, the thermotolerance of day 3 and day 4 bovine IVF embryos were compared. When embryos were pre‐treated with a mild elevated temperature (40.5°C) for 1 hr, and then with a higher temperature (43°C) for 1 hr, no improvement in thermotolerance of the embryos was observed as compared to those treated at 43°C alone. However, a higher thermotolerance was observed in day 4 than day 3 embryos. In conclusion, treatment at 43°C, but not 40.5°C or 41.5°C significantly reduced oocyte developmental competence. An increase in thermotolerance was observed from day 3 to day 4 of in vitro embryonic development, which corresponds to the maternal to zygotic transition of gene expression in bovine embryos. Mol. Reprod. Dev. 53:336–340, 1999. © 1999 Wiley‐Liss, Inc.

Beneficial Effect of Melatonin on Blastocyst In Vitro Production from Heat‐Stressed Bovine Oocytes

“…On the other hand, some findings provided evidence for bovine heat-stressed oocytes to mature faster than non-heatstressed counterparts (Edwards et al 2005;Schrock et al 2007;Andreu-Vazquez et al 2010). In agreement with our results, oocytes heat-stressed during the germinal vesicle stage (bovine: Payton et al 2004;mouse: LaRosa and Downs 2007) or during maturation (bovine: Ju et al 1999Ju et al , 2005Schrock et al 2007;Edwards et al 2009;Zhandi et al 2009;Rispoli et al 2011;Payton et al 2011) have shown competence in overcoming the first cellular division similar to that found in non-heat-stressed oocytes. In addition, we observed that HS treatment improved the ability of the oocytes to form blastocysts.…”

“…However, in contrast to these results, it has also been shown that HS treatment during IVM had no effect (bovine: Ju et al. ; Roth and Hansen ; Schrock et al. ; Roth and Hansen ), or may even decrease the blastocyst rate (bovine: Lawrence et al.…”

Developmental changes in inhibitory effects of arsenic and heat shock on growth of pre‐implantation bovine embryos

“…Previous research has shown that pre-implantation embryos can acquire increased resistance to certain cellular stresses as they advance in development. For bovine embryos, this has been shown to be the case for cyanide toxicity (Donnay et al, 2000) and heat shock (Edwards and Hansen, 1997;Ju et al, 1999). Present results confirm that embryos that are !…”

Spindle dynamics in living mouse oocytes during meiotic maturation, ageing, cooling and overheating: a study by polarized light microscopy

“…However, little attention has been paid to the effects of high temperature. Previous studies using of bovine oocytes indicated that heating oocytes at M-II stage to 40.5-43 • C did not affect oocyte morphology (Kawarsky & King, 2001) and subsequent fertilization or early embryo development (Ju et al, 1999). In the present study, we heated mouse oocytes at both M-I and M-II stage up to 41 • C and found that spindle morphology and the maximum retardance of the spindles were not changed.…”

“…However, little attention has been paid to the effects of high temperature. It is probable that the thermolability of oocytes is related to the presence heat shock proteins in the oocytes (Ju et al, 1999;Kawarsky & King, 2001). In the present study, we heated mouse oocytes at both M-I and M-II stage up to 41 • C and found that spindle morphology and the maximum retardance of the spindles were not changed.…”