Diaz F A, Gutierrez E J, Foster B A, Hardin P T, Bondioli K R
School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, USA.
School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, USA.
Theriogenology. 2025 Jul 1;240:117400. doi: 10.1016/j.theriogenology.2025.117400. Epub 2025 Mar 25.
In the bovine commercial industry, reduced reproductive performance in response to heat stress is one of the main factors causing economic losses. Several studies have shown that heat stress negatively affects oocytes and embryos at the morphological, biochemical, transcriptional, and developmental levels. Yet, there is limited information on the effect of heat stress on the epigenetic modifications of bovine oocytes and embryos. Therefore, the objective of this study was to evaluate the effect of in vivo and in vitro heat stress on the developmental competence, DNA methylation, and DNA hydroxymethylation of bovine oocytes and early embryos. Oocytes were collected through ovum pick-up from non-lactating, non-pregnant Bos taurus beef cows in February and August under Louisiana environmental conditions. The treatments evaluated were: in vivo heat stress (oocytes collected in August), in vitro heat stress (oocytes collected in February and subjected to in vitro heat stress), and control (oocytes collected in February and not subjected to in vitro heat stress). Developmental rates, DNA methylation and DNA hydroxymethylation of metaphase II oocytes (MII), 2-pronucleus embryos (2 PN) and 2-4 cell embryos were evaluated. Global DNA methylation and DNA hydroxymethylation were evaluated through fluorescence immunostaining. No differences between treatments was detected in developmental rates of MII oocytes, 2 PN embryos and 2-4 cell embryos. Similarly, no differences between treatments was detected in global DNA methylation and DNA hydroxymethylation of MII oocytes, 2 PN embryos, and 2-4 cell embryos. Importantly, no differences in global DNA methylation or DNA hydroxymethylation of paternal or maternal pronucleus was detected, indicating that the demethylation process during the 2 PN embryo stage was not altered at the global level. The results of our study showed that under our experimental conditions, in vivo and in vitro heat stress did not affect developmental rates, DNA methylation and DNA hydroxymethylation of MII oocytes and early embryos produced from oocytes obtained from non-lactating, non-pregnant Bos taurus beef cows.
在奶牛商业行业中，热应激导致繁殖性能下降是造成经济损失的主要因素之一。多项研究表明，热应激在形态、生化、转录和发育水平上对卵母细胞和胚胎产生负面影响。然而，关于热应激对牛卵母细胞和胚胎表观遗传修饰影响的信息有限。因此，本研究的目的是评估体内和体外热应激对牛卵母细胞和早期胚胎发育能力、DNA甲基化和DNA羟甲基化的影响。在路易斯安那州环境条件下，于2月和8月从非泌乳、未怀孕的金牛座肉牛中通过采卵收集卵母细胞。评估的处理方式为：体内热应激（8月收集的卵母细胞）、体外热应激（2月收集的卵母细胞并进行体外热应激处理）和对照（2月收集的卵母细胞且未进行体外热应激处理）。评估了中期II卵母细胞（MII）、双原核胚胎（2PN）和2-4细胞胚胎的发育率、DNA甲基化和DNA羟甲基化。通过荧光免疫染色评估整体DNA甲基化和DNA羟甲基化。在MII卵母细胞、2PN胚胎和2-4细胞胚胎的发育率方面，各处理之间未检测到差异。同样，在MII卵母细胞、2PN胚胎和2-4细胞胚胎的整体DNA甲基化和DNA羟甲基化方面，各处理之间也未检测到差异。重要的是，在父源或母源原核的整体DNA甲基化或DNA羟甲基化方面未检测到差异，这表明在2PN胚胎阶段的去甲基化过程在整体水平上未发生改变。我们的研究结果表明，在我们的实验条件下，体内和体外热应激不会影响从非泌乳、未怀孕的金牛座肉牛获得的卵母细胞所产生的MII卵母细胞和早期胚胎的发育率、DNA甲基化和DNA羟甲基化。
