Upon myocardial infarction (MI), ischemia-induced cell death triggers an inflammatory response responsible for removing necrotic material and inducing tissue repair. TRPM4 is a Ca-activated ion channel permeable to monovalent cations. While its role in cardiomyocyte-driven hypertrophy and arrhythmia post-MI has been established, no study has yet investigated its role in the inflammatory process orchestrated by endothelial cells, immune cells and fibroblasts. This study aims to assess the role of TRPM4 in 1) survival and cardiac function, 2) inflammation, and 3) healing post-MI. We performed ligation of the left coronary artery or sham intervention on 154 Trpm4 WT or KO mice under isoflurane anesthesia. Survival and echocardiographic function was monitored up to five weeks. We collected serum during the acute post-MI phase to analyze proteomes, and performed single-cell RNA sequencing on non-myocytic cells of hearts after 24h and 72h. Lastly, we assessed chronic fibrosis and angiogenesis. We observed no significant differences in survival or cardiac function, even though our proteomics data showed significantly decreased tissue injury markers (i.e., creatine kinase M and VE-Cadherin) in KO serum after 12h. On the other hand, inflammation, characterized by serum amyloid P component in the serum, higher number of recruited granulocytes, inflammatory monocytes and macrophages, as well as expression of pro-inflammatory genes, was significantly higher in KO. This correlated with increased chronic cardiac fibrosis and angiogenesis. Since inflammation and fibrosis are closely linked to adverse remodeling, future therapeutic attempts at inhibiting TRPM4 will need to assess these parameters carefully, before proceeding with translational studies.
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