The effect of hibernation on the morphological structure and expression of creatine kinase in the intestine of Pelodiscus sinensis

The intestinal function of hibernating animals undergoes seasonal changes, during which they are in a fasting state, which also affects the morphology, structure, and function of intestine. The aim of this study was to analyse the histological differences in the intestinal structure, goblet cells, and mucosa of the initial (ISI), anterior (ASI), middle (MSI) and posterior (PSI) of small intestine of Pelodiscus sinensis during the whole hibernation process and to investigate the role of the key enzyme creatine kinase (CK) in regulating energy homeostasis during hibernation. The results of HE staining showed that the intestinal mucosa of the P. sinensis during hibernation presented detachment and atrophy of villus, and narrowing of gaps while the villous length of the ISI, ASI, MSI, and PSI were significantly decreased than those in normal stage. As hibernation progresses, the intestinal crypt of the ISI first increased and then decreased significantly. The AB-PAS staining results revealed that as hibernation progressed, the number of type Ⅰ goblet cells in the ISI significantly increased, while the number of type Ⅲ goblet cells significantly decreased. The immunohistochemical results revealed that CK-MB was highly expressed in the intestinal villus of P. sinensis. During hibernation, the expression of CK-MB in P. sinensis continued to increase in the ISI and decrease in the PSI. In summary, the results of this study suggested that hibernation process could alter the morphological structure of the ISI and ASI of P. sinensis, making them more vulnerable. Meanwhile, the ISI may protect the mucosal tissue during hibernation by increasing type Ⅲ goblet cells and decreasing type I goblet cells. During this process, the continuously increasing expression of CK in the ISI may participate in the adaptation of P. sinensis to intestinal hibernation by regulating energy metabolism.