miR-4443 alleviates myocardial injury in acute myocardial infarction by targeting and regulating TIMP2.

Acute myocardial infarction (AMI) continues to be a leading cause of global morbidity and mortality, where adverse left ventricular remodeling and subsequent heart failure serve as primary determinants of long-term prognosis. This study aimed to delineate the expression pattern, clinical significance, and molecular mechanisms of miR-4443 in AMI. The study included 100 patients diagnosed with AMI and 100 normal healthy controls. Serum miR-4443 levels were measured by qRT-PCR, and their correlations with patient prognosis were analyzed by Kaplan-Meier curve and Cox regression analysis. To mimic ischemia-reperfusion injury in vitro, human AC16 cardiomyocytes underwent hypoxia/reoxygenation (H/R) treatment. MTT for cell viability, flow cytometry for apoptosis, and ELISA for TNF-α, IL-1β, and IL-6 levels were performed to determine the regulatory role of miR-4443. A bioinformatics analysis predicted the targeting relationship between miR-4443 and TIMP2, and this was validated by the dual-luciferase reporter assay. For matrix remodeling evaluation, MMP2 and MMP9 mRNA expressions were detected by qRT-PCR. The expression of miR-4443 in serum samples from AMI patients was significantly downregulated. The low levels of miR-4443 indicate a poor prognosis for AMI. During H/R injury, miR-4443 expression was downregulated in AC16 cells, its overexpression significantly rescued H/R-induced cell viability decline, increased apoptosis, inflammatory factor release, and upregulation of MMP2/MMP9 expression. TIMP2 was a direct target gene for miR-4443. Functional rescue experiments showed that overexpression of TIMP2 could reverse the protective effect of miR-4443 mimics on H/R injury in cells. Our findings demonstrate that miR-4443 is downregulated in AMI and exerts protective effects against H/R injury in cardiomyocytes, at least in part, through targeting TIMP2, suggesting that the miR-4443/TIMP2 axis may be a potential critical regulatory target in AMI. Further in vivo validation is warranted to substantiate its therapeutic potential.