Cardiac fibroblast-derived mitochondria-enriched sEVs regulate tissue inflammation and ventricular remodeling post-myocardial infarction through NLRP3 pathway

Resident cardiac fibroblasts (CFs) play a critical role in sensing injury signals and regulating inflammatory responses following myocardial infarction (MI). Damaged mitochondria can be released into the extracellular environment through various mechanisms, including via extracellular vesicles (EVs). This study aimed to determine whether CFs can transfer damaged mitochondrial components through small EVs (sEVs) and to elucidate their role in modulating inflammatory responses post-MI.

MI was induced in mice by ligating the left anterior descending coronary artery. Nanoflow cytometry was used to detect mitochondrial components within sEVs. Label-free proteomics identified differential protein expression in sEVs derived from CFs under normoxia and normoglycemia conditions (CFs-Nor-sEVs) and from CFs subjected to oxygen-glucose deprivation (CFs-OGD-sEVs). To evaluate macrophage inflammatory responses, CF-derived sEVs were co-cultured with mouse bone marrow-derived macrophages (BMDMs). Additionally, the effects of intramyocardial injection of CF-derived sEVs were assessed in MI mice with or without the NLRP3 inhibitor CY-09.

The results demonstrated the presence of mitochondrial components within CF-derived sEVs post-MI. Damaged mitochondrial components were enriched in CFs-OGD-sEVs (CFs-mt-sEVs), which promoted the activation of a pro-inflammatory phenotype in BMDMs in vitro. In vivo, intramyocardial injection of CFs-mt-sEVs exacerbated tissue inflammation, worsened cardiac dysfunction, and aggravated maladaptive ventricular remodeling following MI. Mechanistically, these effects were mediated through the activation of NLRP3, and treatment with the NLRP3 inhibitor CY-09 reversed these outcomes.

This study reveals that CFs can transfer damaged mitochondrial components via sEVs following MI, thereby promoting macrophage inflammatory activation and contributing to maladaptive ventricular remodeling through NLRP3 activation. These findings suggest that targeting CF-derived mt-sEVs and NLRP3 may offer therapeutic potential to improve cardiac function and mitigate ventricular remodeling after MI.