Shexiang baoxin pill ameliorates cardiac fibrosis by inhibiting fibroblast to myofibroblast transition through STAT3 phosphorylation suppression

Background: Shexiang Baoxin Pill (SBP) is a traditional Chinese medicine used to treat ischemic cardiomyopathy. It can alleviate cardiac fibrosis following myocardial ischemia/reperfusion (MI/R) injury, but its action mechanism remains unclear.

Purpose: To elucidate the mechanism by which SBP alleviates cardiac fibrosis.

Methods: snRNA-seq was employed to construct a cardiac cell atlas of MI/R mice treated with SBP, identify DEGs in fibroblasts, and analyse transcription factor activity. Molecular docking and molecular dynamics simulations were used to investigate the binding sites and binding stability of the screened SBP chemical components with the STAT3 protein. Immunohistochemistry, immunofluorescence, qRT-PCR and WB techniques were utilized to assess the impact of SBP treatment on cardiac fibrosis and myofibroblast transition, while echocardiography was used to evaluate cardiac function in mice.

Results: SBP treatment significantly improved cardiac function in mice subjected to MI/R injury: cardiac fibrosis area was reduced by 4.2 %, EF was increased by 4.5 % and FS was increased by 2.5 %. snRNA-seq revealed that SBP treatment did not alter the overall number of cardiac fibroblasts but modulated the proportional distribution of their subtypes. SCENIC-based transcription factor activity analysis suggested that the STAT3 signalling pathway might play a key role in this process. In vitro cell experiments demonstrated that H/R treatment induced the transition of fibroblasts into α-SMA-positive myofibroblasts, which SBP inhibited.

Conclusions: This study has demonstrated for the first time that SBP effectively attenuates cardiac fibrosis post-MI/R, and elucidated the mechanism by which SBP inhibits myofibroblast transdifferentiation via the STAT3 signaling pathway.

Myocardial fibrosis; Myocardial ischemia/reperfusion injury; Myofibroblast transdifferentiation; Shexiang baoxin pill; Signal transducer and activator of transcription 3.