Abstract: Pyometra, a common canine disease accompanied by bacterial contamination in the uterus, is a major cause of canine death worldwide. However, the underlying mechanism of pyometra remains poorly understood. The purpose of this study is to identify the gene expression changes associated with canine pyometra, and to screen differentially expressed genes, regulatory pathways and hub genes to further understand the molecular mechanism of pyometra. RNA sequencing (RNA-seq) was uesd to study the gene expression profile of canines with pyometra compared with those with benign uterus. The results showed a discrepancy of 11 812 gene expressions, among which 7 086 genes were up-regulated while 4 726 genes were down-regulated in the uteri of diseased animals. GO analysis showed that differentially expressed genes were mainly involved in biological processes such as immune system processes, cytokine activity, chemokine activity, and cytokine receptor binding. KEGG-Pathway analysis found that differentially expressed genes were involved in the signaling pathways of inflammation and immune response activation, such as NF-κB signaling pathway, PI3K-Akt signaling pathway, B cell receptor signaling pathway, phagosome and natural killer cell-mediated cytotoxicity, revealing that inflammation and immune response activation are the main pathological stages of canine pyometra. Eleven key hub genes were identified by STRING database network, such as CDK1, ESR1 and SHC1, which can be used as biomarkers for early diagnosis of pyometra. In conclusion, the current study presents a comprehensive landscape of the gene expression in pyometra canines and contribute to a better understanding of the molecular mechanisms of canine pyometra.

Key words: canine, pyometra, RNA-seq, inflammation, immune system