Common Handling Procedures Conducted in Preclinical Safety Studies Results in Minimal Hepatic Gene Expression Changes in Sprague-Dawley Rats

Gene expression profiling has been used as a tool to gain mechanistic understanding of adverse effects in response to compound exposure. However, little is known about how the common handling procedures of experimental animals during a preclinical study alter their baseline gene expression. We report on gene expression changes in the livers of female Sprague-Dawley rats following common handling procedures. Insight on baseline gene expression changes obtained in this study will allow us to evaluate how these changes may affect interpretation of gene expression profiles following compound exposure. Rats were divided into three groups (n = 10 per group): one group was not subjected to handling procedures, euthanized on day 2, and served as controls for both handled groups. Animals in the other two groups were weighed, subjected to restraint in Broome restrainers, and administered water via oral gavage daily for 1 or 4 days with tail vein blood collections at 1, 2, 4, and 8 hours postdose on days 1 and 4 followed by euthanasia on day 2 or 5. Significantly altered genes were identified in livers of animals following 1 or 4 days of handling when compared to the unhandled animals. Gene changes in animals handled for 4 days were similar to those handled for 1 day, suggesting a lack of habituation. The altered genes were primarily immune function related genes. These findings, along with a correlating increase in corticosterone levels suggest that common handling procedures may cause a minor immune system perturbance.基因表达谱分析已被用作解析化合物暴露所致不良反应分子机制的研究工具。然而，目前对于临床前研究中实验动物的常规操作流程如何改变其基线基因表达水平，尚缺乏系统认知。本研究针对经常规操作流程处理后的雌性斯普拉格-道利（Sprague-Dawley）大鼠肝脏中的基因表达变化展开报道。本研究获得的基线基因表达变化相关数据，将有助于评估此类改变如何影响化合物暴露后基因表达谱的解读结果。实验大鼠被分为3组（每组n=10）：其中1组未接受任何操作流程，于第2天实施安乐死，作为两组处理组的共同对照。其余两组大鼠均接受称重、使用布鲁姆（Broome）固定器进行固定，并每日经口灌胃给予纯水，分别持续1天或4天；分别于给药后1、2、4、8小时采集尾静脉血样，采血时间点为第1天和第4天，最终分别于第2天或第5天实施安乐死。与未接受操作的对照组大鼠相比，经1天或4天操作处理的大鼠肝脏中均检测到显著差异表达基因。持续接受操作4天的大鼠，其基因表达变化与仅接受1天操作的大鼠高度相似，表明未出现适应性习惯化。差异表达基因主要与免疫功能相关。结合血清皮质酮水平的相关性升高，本研究结果表明，常规实验动物操作流程可能会引发轻度的免疫系统扰动。