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

Resident cardiac fibroblasts (CFs) play crucial roles in sensing injury signals and regulating inflammatory responses post-myocardial infarction (MI). Damaged mitochondria can be transferred extracellularly via various mechanisms, including extracellular vesicles (EVs). In this study, we aimed to investigate whether CFs could transfer damaged mitochondrial components via small EVs (sEVs) and elucidate their role in regulating inflammatory responses post-MI. Left anterior descending coronary artery ligation was performed in mice. Mitochondrial components in sEVs were detected using nanoflow cytometry. Differential protein expression in sEVs from normoxia and normoglycemia CFs (CFs-Nor-sEVs) and CFs post oxygen-glucose deprivation (CFs-OGD-sEVs) was identified using label-free proteomics. CFs-sEVs were co-cultured with mouse bone marrow-derived macrophages (BMDMs) to assess macrophage inflammatory responses. Effects of intramyocardial injection of CFs-sEVs were assessed in MI mice in the absence or presence of NLRP3 inhibitor CY-09. Results demonstrated that mitochondrial components were detected in CFs-derived sEVs post-MI. Damaged mitochondrial components were enriched in CFs-OGD-sEVs (CFs-mt-sEVs), which promoted pro-inflammatory phenotype activation of BMDMs in vitro. Myocardial injection of CFs-mt-sEVs enhanced tissue inflammation, aggravated cardiac dysfunction, and exacerbated maladaptive ventricular remodeling post-MI in vivo. Mechanistically, above effects were achieved via activation of NLRP3 and above effects could be reversed by NLRP3 inhibitor CY-09. This study indicates that CFs could transfer damaged mitochondrial components via the sEVs post-MI, promote macrophage inflammatory activation and exacerbate maladaptive ventricular remodeling post MI by activating NLRP3. Our findings highlight the potential therapeutic effects of inhibiting CFs-mt-sEVs and NLRP3 to improve cardiac function and attenuate ventricular remodeling post-MI.