Assessment of animal wellbeing in bile duct ligation models

Cholestasis is one of the common causes of liver fibrosis and cirrhosis. The prevailing animal model currently used to study cholestasis is the common bile duct ligation (cBDL). A modification of this model is the ligation of the left hepatic bile duct (pBDL), which induces cholestasis only in the left liver lobe. We also simultaneously ligated the left bile duct with the corresponding left hepatic artery (pBDL+pAL). After induction of partial or total cholestasis in mice the wellbeing of these animals was evaluated by assessing burrowing behavior, body weight and a distress score. To compare pathological features of these animal models, the plasma levels of liver enzymes, necrotic areas within the liver tissue and fibrosis were assessed. The survival rate of the animals and the wellbeing was comparable between pBDL+pAL and pBDL. However, surgical intervention by pBDL+pAL caused confluent necrosis in contrast to the focal necrosis observed after pBDL. Interestingly, pBDL animals had a significantly higher survival rate and their wellbeing was significantly improved when compared to cBDL animals. On day 14 after ligation liver enzymes such as aspartate and alanine aminotransferase, alkaline phosphatase and glutamate dehydrogenase were significantly elevated after cBDL, but only glutamate dehydogenase activity was increased after pBDL. Importantly, pBDL reduced the number of mice needed and improved the wellbeing of animals. Therefore, it might be a superior animal model when studying local pathological features during cholestasis.

胆汁淤积（Cholestasis）是引发肝纤维化与肝硬化的常见病因之一。目前，用于胆汁淤积研究的主流动物模型为胆总管结扎术（common bile duct ligation, cBDL）。该模型的改良亚型为左肝胆管结扎术（pBDL），仅可在左侧肝叶诱导胆汁淤积。本研究在此基础上，同时结扎左侧胆管及其伴行的左肝动脉，构建pBDL+pAL模型。在小鼠体内诱导部分或完全性胆汁淤积后，通过挖掘行为、体重及应激评分评估实验动物的生存状态。为对比各模型的病理特征，本研究检测了血浆肝酶水平、肝组织坏死区域及纤维化程度。结果显示，pBDL+pAL组与pBDL组的动物存活率及生存状态无显著差异。但与pBDL组仅出现局灶性坏死不同，pBDL+pAL组手术干预可引发融合性坏死。值得注意的是，相较于cBDL组小鼠，pBDL组小鼠的存活率显著更高，生存状态也明显改善。结扎术后第14天，cBDL组的天冬氨酸转氨酶、丙氨酸转氨酶、碱性磷酸酶及谷氨酸脱氢酶水平均显著升高，而pBDL组仅谷氨酸脱氢酶活性有所上升。尤为关键的是，pBDL模型可减少实验所需小鼠数量，并改善动物的生存状态。因此，在研究胆汁淤积相关的局部病理特征时，pBDL模型或为更优的动物模型。