Expression profiling of mural granulosa cells after heat-stress (HS) vs. pair-fed (PF) conditions

High environmental temperatures induce detrimental effects on various reproductive processes in cattle. According to the predicted global warming the number of days with unfavorable ambient temperatures will further increase. The objective of this study was to investigate effects of acute heat stress during the late pre-ovulatory phase on morphological, physiological and molecular parameters of dominant follicles in cycling cows during lactation. Eight German Holstein cows in established lactation were exposed to heat stress (28°C) or thermoneutral conditions (15°C) with pair-feeding for four days. After synchronization growth of dominant follicles was monitored by ultrasonogrphy, and 21 hrs after an induced pre-ovulatory LH surge antral steroid hormones and granulosa cell-specific gene expression profiles were determined. The data showed that the pre-ovulatory growth of dominant follicles and the estradiol, but not the progesterone concentrations tended to be slightly affected. mRNA microarray and hierarchical cluster analysis revealed distinct expression profiles in granulosa cells derived from heat stressed compared to pair-fed animals. Among the 255 affected genes heatstress-, stress- or apoptosis associated genes were not present. But instead, we found up-regulation of genes essentially involved in G-protein coupled signaling pathways, extracellular matrix composition, and several members of the solute carrier family as well as up-regulation of FST encoding follistatin. In summary, the data of the present study show that acute pre-ovulatory heat stress can specifically alter gene expression profiles in granulosa cells, however without inducing stress related genes and pathways and suggestively can impair follicular growth due to affecting the activin-inhibin-follistatin system. German Holstein cows in established lactation were exposed to heat stress (28°C) or thermoneutral conditions (15°C) with pair-feeding for four days. 21 hrs after an induced pre-ovulatory LH surge antral steroid hormones and granulosa cell-specific gene expression profiles were determined.

环境高温会对奶牛的多种生殖过程产生不利影响。据全球变暖预测，不利环境温度的天数将进一步增加。
本研究旨在探究泌乳期发情周期奶牛在排卵前晚期遭遇急性热应激时，其优势卵泡的形态学、生理学及分子参数所受的影响。
选取8头处于稳定泌乳阶段的德国荷斯坦奶牛，分别置于热应激（28℃）或热中性环境（15℃）中，并进行配对饲喂，持续4天。
在对优势卵泡生长进行超声监测（ultrasonography）并同步化处理后，于诱导排卵前促黄体生成素（LH）峰出现后的21小时，测定卵泡液类固醇激素水平及颗粒细胞特异性基因表达谱。
数据显示，优势卵泡的排卵前生长及雌二醇浓度呈现出轻微受影响的趋势，但孕酮浓度未受明显影响。
mRNA微阵列（mRNA microarray）及层次聚类分析（hierarchical cluster analysis）结果显示，与配对饲喂组奶牛相比，热应激组奶牛的颗粒细胞呈现出显著不同的基因表达谱。
在受影响的255个基因中，并未发现与热应激、应激或细胞凋亡相关的基因。
与之相反，本研究发现了多个基因的上调表达，这些基因主要参与G蛋白偶联信号通路（G-protein coupled signaling pathway）、细胞外基质（extracellular matrix）组成，以及溶质载体家族（solute carrier family）的多个成员，同时编码卵泡抑素的FST基因也呈现上调表达。
综上，本研究数据表明，排卵前急性热应激可特异性改变颗粒细胞的基因表达谱，但不会诱导应激相关基因及通路的表达，且提示该应激可能通过影响激活素-抑制素-卵泡抑素系统而损害卵泡生长。
选取8头处于稳定泌乳阶段的德国荷斯坦奶牛，分别置于热应激（28℃）或热中性环境（15℃）中，并进行配对饲喂，持续4天。于诱导排卵前促黄体生成素（LH）峰出现后的21小时，测定卵泡液类固醇激素水平及颗粒细胞特异性基因表达谱。