miR-146a-3p mediates Suxiao Jiuxin Pill's enhancement of MSC-exosome efficacy in myocardial infarction

• SXJX-MSCexo is a novel cell-free therapeutic strategy for myocardial infarction. • SXJX-MSCexo boosts heart function and angiogenesis while shrinking infarct size and reducing inflammation. • SXJX-MSCexo attenuates AMI inflammation and infarct via TLR4/NF-κB pathway. • SXJX-MSCexo mediates angiogenesis through exosomal miRNA-146a-3p in AMI rats. • SXJX-MSCexo unlocks new therapeutic dimensions for Suxiao Jiuxin Pill in MI treatment. Suxiao Jiuxin Pill (SXJX) is a traditional Chinese medicine commonly used in the clinical management of acute coronary syndromes, and its cardioprotective effects have been well documented. Mesenchymal stem cell-derived exosomes (MSCexo) have also shown significant promise in myocardial repair. Nevertheless, whether SXJX functionally modulates MSCexo and whether this interaction is mediated by exosomal miRNAs remain to be elucidated. Exosomes were isolated via ultracentrifugation from control MSCs (NC-MSCexo) and MSCs preconditioned with SXJX-containing serum (SXJX-MSCexo). A rat model of myocardial infarction was established by left anterior descending coronary artery ligation to evaluate cardiac function, infarct size, inflammatory responses (focusing on the TLR4/TRAF6/NF-κB pathway), macrophage polarization, and angiogenesis. The effects of exosomes on endothelial cell function were also assessed in vitro. miRNA sequencing was performed to identify key miRNAs, and their functional role was validated using exosomes with miR-146a-3p knockdown (SXJX-MSCexo-i146). Compared to NC-MSCexo, treatment with SXJX-MSCexo significantly improved cardiac function recovery, attenuated the inflammatory response, and promoted angiogenesis following myocardial infarction. miR-146a-3p was highly enriched in SXJX-MSCexo, and knockdown of this miRNA effectively reversed the cardioprotective effects conferred by SXJX-MSCexo. Mechanistically, the downregulation of miR-146a-3p blocked the regulatory effect of SXJX-MSCexo on the TLR4/TRAF6/NF-κB signaling pathway and diminished its pro-angiogenic capacity. This study demonstrates that SXJX-MSCexo represent a promising cell-free therapeutic strategy for myocardial infarction. Compared to NC-MSCexo, SXJX-MSCexo exhibited superior efficacy in reducing myocardial injury and improving cardiac function, primarily attributed to their enhanced anti-inflammatory and pro-angiogenic properties. Mechanistic investigations revealed that SXJX preconditioning significantly enriched exosomal miR-146a-3p. Loss-of-function experiments confirmed that this miRNA is a key effector molecule mediating the cardioprotective effects of SXJX-MSCexo. Specifically, miR-146a-3p mediates myocardial repair by suppressing the TLR4/TRAF6/NF-κB pathway to attenuate inflammation and by synergistically promoting angiogenesis.