The Mechanism of SIRT3 Regulating SRV2-Mediated Mitochondrial Fission of Fibroblasts to Inhibit Myocardial Fibrosis after Acute Myocardial Infarction.

Objective: Cardiac dysfunction can result from excessive fibrosis in cardiac fibroblasts (CFs) following an acute myocardial infarction (AMI). SIRT3 has been shown to be associated with numerous cardiovascular diseases. This study aimed to investigate the mechanism by which SIRT3 influences myocardial fibrosis following AMI.

Methods: An AMI model was established in rats and echocardiography was used to assess cardiac systolic function. Triphenyl tetrazolium chloride (TTC) and H&E staining were employed to observe the myocardial histopathological status. Masson trichrome staining was used to detect fibrosis, and the changes in expression of fibrosis-related proteins were detected by Western Blot (WB). In this study, we utilized in vitro cell models stimulated by Ang II to investigate the underlying mechanisms. We employed Transwell and CCK-8 assays to detect the function of CFs. Additionally, we used transmission electron microscopy (TEM) to observe the structural morphology of mitochondria, whereas WB was performed to quantify fibrosis-associated proteins and to assay the changes in SIRT3, SRV2, and Drp1.

Results: We observed a significant decrease in the expression of SIRT3 and an increase in mitochondrial fragmentation in rats with AMI. Additionally, we observed upregulation of fibrosis-associated signature proteins and collagen proteins expression. Through the use of vitro Ang II stimulation we observed a downregulation of SIRT3 expression, an increase in mitochondrial fragmentation, and an increase in the proliferation and migration of CFs. Opposite effects were observed when SIRT3 was overexpressed. Additive mitochondrial division agonists were found to stimulate the proliferation and migration of CFs, however, SIRT3 expression was unchanged. Interference with SRV2 and SIRT3 revealed that SIRT3 effectively prevented the expression of SRV2/Drp1, resulting in the inhibition of mitochondrial division and the suppression of CFs proliferative migration.

Conclusion: In summary, SIRT3 can suppress myocardial fibrosis after acute myocardial infarction by regulating SRV2/Drp1-mediated mitochondrial division.