Changes in microRNA expression related to ischemia-reperfusion injury in the kidney of the thirteen-lined ground squirrel during torpor

During the hibernation season, the thirteen-lined ground squirrel undergoes cyclical torpor and arousal periods. The decrease and restoration of metabolic rate and oxygen delivery during torpor and arousal, respectively, may cause reperfusion-ischemia injury in the kidneys. In order to maintain the structural integrity of the kidneys necessary for renal function resumption during arousal, the thirteen-lined ground squirrel has developed adaptive methods to prevent and repair kidney injury. In this present study, computational methods were used to clean and analyze sequenced kidney RNA samples. Significantly differentially expressed microRNAs and enriched gene sets were also determined. From the gene set analysis, the results showed an increase in ubiquitin-related processes and p53 signaling pathways which suggested the occurrence of kidney damage during torpor. There was also an observed increase in cell cycle processes and the anchoring junction cellular compartment which may lend to the prevention of kidney injury. From the differentially expressed microRNAs, miR-27a (log₂FC = 1.639; p-value = 0.023), miR-129 (log₂FC = 2.516; p-value = 0.023), miR-let-7b (log₂FC = 2.360; p-value = 0.025), miR-let-7c (log₂FC = 2.291; p-value = 0.037) and miR-let-7i (log₂FC = 1.564; p-value = 0.039) were found to be significantly upregulated. These biochemical adaptations may allow the thirteen-lined ground squirrel to maintain kidney structure and function during hibernation.