Unraveling regulatory mechanisms of atrial remodeling of mitral regurgitation pigs by gene expression profiling analysis: Role of type i angiotensin II receptor antagonist

Left atrial enlargement associated with mitral regurgitation (MR) predicts a poor prognosis. However, the underlying regulatory mechanisms of atrial remodeling remain unclear. We used high-density oligonucleotide microarrays and enrichment analysis to identify the alteration of RNA expression pattern and biological processes involved in the atrial remodeling of pigs with and without MR. Gene arrays from left atria tissues were compared in 13 pigs (iatrogenic MR pigs [n = 6], iatrogenic MR pigs treated with valsartan [n = 4], and pigs without MR [n = 3]). A total of 22 genes were differentially upregulated by altered fold change >2.0 (Log₂FC > 1), and 49 genes were differentially downregulated by altered fold change <0.5 (Log₂FC < -1) in the left atria of the MR pigs compared with the pigs without MR. Enrichment analysis showed that renin-angiotensin system was identified in the Kyoto Encyclopedia of Genes and Genomes pathway. Notably, 12 of the 22 upregulated genes were identified to be downregulated by valsartan and 10 of the 49 downregulated genes were identified to be upregulated by valsartan. The tissue concentrations of angiotensin II and gene expression of hypertrophic gene, myosin regulatory light chain 2, ventricular isoforms, and fibrosis-related genes were significantly increased in the MR pigs compared with pigs without MR. In conclusion, differentially expressed transcriptome and related biological pathways have been identified in the left atria of the MR pigs compared with pigs without MR. Additionally, some of the differentially expressed genes could be regulated by type I angiotensin II receptor blocker.