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

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. Overall design: 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。根据全球变暖的预测结果，不利环境温度持续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排卵前后期的急性热应激对其优势卵泡（dominant follicles）的形态学、生理学及分子参数的影响。
8头处于稳定泌乳期的德国荷斯坦奶牛被分为两组，分别暴露于热应激环境（28°C）与热中性环境（thermoneutral conditions，15°C），并进行配对饲喂（pair-feeding），持续4天。
经过发情同步化处理后，通过超声成像（ultrasonography）监测优势卵泡的生长情况；在诱导产生排卵前促黄体素（LH）峰后的21小时，采集样本并测定卵泡液类固醇激素水平与颗粒细胞（granulosa cells）特异性基因表达谱。
数据显示，优势卵泡的排卵前生长以及雌二醇浓度（而非孕酮浓度）呈现出轻微受影响的趋势。
mRNA微阵列（mRNA microarray）与层级聚类分析（hierarchical cluster analysis）结果显示，与配对饲喂组相比，热应激组奶牛的颗粒细胞呈现出显著不同的表达谱。
在255个差异表达基因中，未发现热应激相关、应激相关或凋亡相关基因。
反之，本研究发现参与G蛋白偶联信号通路（G-protein coupled signaling pathways）、细胞外基质（extracellular matrix）组成的核心基因，以及多个溶质转运蛋白家族（solute carrier family）成员均出现上调表达；同时编码卵泡抑素（follistatin）的FST基因也呈现上调。
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激活，且可能通过影响激活素-抑制素-卵泡抑素系统（activin-inhibin-follistatin system）损害卵泡生长。
整体实验设计：将处于稳定泌乳期的德国荷斯坦奶牛分为两组，分别暴露于热应激环境（28°C）与热中性环境（15°C）并进行配对饲喂，持续4天。在诱导产生排卵前促黄体素峰后的21小时，测定卵泡液类固醇激素水平与颗粒细胞特异性基因表达谱。