Heat shock protein 27 downregulation attenuates isoprenaline-induced myocardial fibrosis and diastolic dysfunction by modulating the endothelial-mesenchymal transition.

Heart failure (HF), an end-stage clinical syndrome secondary to cardiac impairment, significantly affects patients' quality of life and long-term prognosis. Myocardial fibrosis leads to systolic and diastolic dysfunction, and promotes the progression of HF. Several studies involving the modulation of myocardial fibrosis have been conducted in an effort to improve cardiac function. Heat shock protein 27 (HSP27) is a small chaperone protein that is overexpressed in cellular stress states. HSP27 modulates epithelial-mesenchymal transition, playing a crucial role in the pathology of several fibrotic diseases. However, its association with myocardial fibrosis regulation is unknown. This study aimed to investigate the mechanisms by which HSP27 regulates myocardial fibrosis. We created cardiac-specific HSP25 (the murine ortholog of human HSP27) knockout mice and found that HSP25 knockdown inhibited endothelial-mesenchymal transition (EndMT), attenuated myocardial fibrosis, and ameliorated diastolic dysfunction in isoproterenol-induced HF mice via echocardiography, histology, and western bloting. In vitro, HSP27 knockdown attenuated transforming growth factor beta-induced EndMT, whereas HSP27 overexpression promoted EndMT. Furthermore, the SMAD3/SNAIL1 pathway was found to be crucial for HSP27-mediated EndMT regulation. As an essential molecule in EndMT regulation and myocardial fibrosis modulation, HSP27 may hold promise as a therapeutic target for patients with HF.