Disparate consequences of heat stress exposure during meiotic maturation: embryo development after chemical activation vs fertilization of bovine oocytes

Abstract

Consequences of heat stress exposure during the first 12 h of meiotic maturation differed depending on how and when bovine oocytes were activated. If heat-stressed oocytes underwent IVF at w24 h, blastocyst development was less than for respective controls and similar to that obtained for nonheat-stressed oocytes undergoing IVF at 30 h (i.e. slightly aged). In contrast, if heat-stressed oocytes underwent chemical activation with ionomycin/6-dimethylaminopurine at 24 h, blastocyst development was not only higher than respective controls, but also equivalent to development obtained after activation of nonheat-stressed oocytes at 30 h. Developmental differences in chemically activated vs IVF-derived embryos were not related to fertilization failure or gross alterations in cytoskeletal components. Rather, ionomycin-induced calcium release and MAP kinase activity were less in heat-stressed oocytes. While underlying mechanisms are multifactorial, ability to obtain equivalent or higher development after parthenogenetic activation demonstrates that oocytes experiencing heat stress during the first 12 h of meiotic maturation have the necessary components to develop to the blastocyst stage, but fail to do so after fertilization.

Developmental competence and expression pattern of bubaline (Bubalus bubalis) oocytes subjected to elevated temperatures during meiotic maturation in vitro

“…Likewise, Payton et al [29] have reported that the physiologically relevant elevated temperature compromised the continued development of antral follicle and germinal vesicle-stage oocytes in a direct manner. It has also been reported that oocytes experiencing heat stress during first 12 h of in vitro maturation have a lower ability for blastocyst development after fertilization than non-heat-stressed oocytes [30].…”

Factors affecting the in vitro embryo production in cattle associated to ovum pick up sistem

“…On the other hand, some findings provided evidence for bovine HSO to mature faster than non-heat-stressed 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, 2005;Schrock 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-HSO. In addition, we observed that HS treatment improved the ability of the oocytes to form blastocysts.…”

“…In this regard, Pribenszky et al (2010) highlighted a number of studies in which sub-lethal stress treatments (such as high hydrostatic pressure, osmotic stress, HS or OS) might increase the morphological survival, fertilization ability, and in vitro development, both in gametes and embryos. However, in contrast to these results, it has also been shown that HS treatment during IVM had no effect (bovine: Ju et al 1999;Roth and Hansen, 2004b;Schrock et al, 2007;Roth and Hansen, 2009), or may even decrease the blastocyst rate (bovine: Lawrence et al, 2004;Roth and Hansen, 2004a, b;Edwards et al, 2005;Ju et al, 2005;pig: Tseng et al, 2006;Sugiyama et al, 2007;Soto and Smith., 2009;Zhandi et al, 2009;Rispoli et al, 2011). This seeming controversy on the effects of HS could probably be explained by the different temperatures and timing schedule of the HS treatments and the methodology used in the cited reports.…”

“…This seeming controversy on the effects of HS could probably be explained by the different temperatures and timing schedule of the HS treatments and the methodology used in the cited reports. In addition, Rispoli et al (2011) observed divergent responses on parthenogenetic and in vitro-produced bovine embryo development when oocytes were submitted to HS (41ºC) during the first 12 h of IVM.…”

“…Nevertheless, in this study, we tested higher levels of temperature, as in vitro embryos can withstand higher temperatures than those in vivo (Ozawa et al, 2002). Several authors have used the temperature of 41.0ºC with different exposure times to HSO during IVM Lawrence et al, 2004;Roth and Hansen, 2004a, b;Schrock et al, 2007;Rispoli et al, 2011). In our study, and also in the case of other studies (already mentioned), a HS treatment of 41.0ºC might not be harmful enough to compromise embryo development, and subsequently may not be good to test whether melatonin could mitigate the harmful effects of HS on embryo development from HSO.…”