Abstract

Abstract Cardiac fibrosis is the hallmark of cardiovascular disease (CVD), which is leading cause of death worldwide. Previously, we have shown that interleukin‐10 (IL10) reduces pressure overload (PO)‐induced cardiac fibrosis by inhibiting the recruitment of bone marrow fibroblast progenitor cells (FPCs) to the heart. However, the precise mechanism of FPC involvement in cardiac fibrosis remains unclear. Recently, exosomes and small extracellular vesicles (sEVs) have been linked to CVD progression. Thus, we hypothesized that pro‐fibrotic miRNAs enriched in sEV‐derived from IL10 KO FPCs promote cardiac fibrosis in pressure‐overloaded myocardium. Small EVs were isolated from FPCs cultured media and characterized as per MISEV‐2018 guidelines. Small EV's miRNA profiling was performed using Qiagen fibrosis‐associated miRNA profiler kit. For functional analysis, sEVs were injected in the heart following TAC surgery. Interestingly, TGFβ‐treated IL10‐KO‐FPCs sEV increased profibrotic genes expression in cardiac fibroblasts. The exosomal miRNA profiling identified miR‐21a‐5p as the key player, and its inhibition with antagomir prevented profibrotic signalling and fibrosis. At mechanistic level, miR‐21a‐5p binds and stabilizes ITGAV ( integrin av) mRNA. Finally, miR‐21a‐5p‐silenced in sEV reduced PO‐induced cardiac fibrosis and improved cardiac function. Our study elucidates the mechanism by which inflammatory FPC‐derived sEV exacerbate cardiac fibrosis through the miR‐21a‐5p/ITGAV/Col1α signalling pathway, suggesting miR‐21a‐5p as a potential therapeutic target for treating hypertrophic cardiac remodelling and heart failure.