Abstract P2097: Ablation Of Fibroblast Human Antigen R (HuR) Mitigates Cardiac Fibrosis

Background: Cardiac fibrosis is a common pathology associated with various heart diseases and is attributed to the activation of resident fibroblasts. Limiting fibroblast-to-myofibroblast differentiation and proliferation could be a pragmatic approach to mitigate adverse cardiac outcomes. Recent studies have shown that RNA-binding proteins are critical in the post-transcriptional regulation of fibroblast-to-myofibroblast differentiation. Human antigen R (HuR), an RNA-binding protein, modulates post-transcriptional gene expression in various pathophysiology, including heart diseases. However, the direct role of cardiac myofibroblast HuR is largely unknown. Methods and Results: To investigate the role of myofibroblast-specific HuR in cardiac fibrosis, we generated a tamoxifen-inducible periostin-Cre-driven myofibroblast-specific HuR knockout (KO) mouse. Control and KO mice were subjected to transverse aortic constriction (TAC), and cardiac functions were assessed by echocardiography. Histological and morphometric analyses were used to evaluate cardiac fibrosis and remodeling eight weeks post-injury. Our results demonstrated that myofibroblast-specific deletion of HuR limited cardiac fibrosis and preserved cardiac functions in HuR knockout mice compared to the control group. Further, the knockdown of HuR in human cardiac fibroblasts suppressed myofibroblast differentiation after treatment with TGF-β1 (10 ng/ml), as observed by a decrease in cell migration and production of extracellular matrix-associated molecules. Interestingly, an in vivo BrdU labeling assay showed a reduction in myofibroblast proliferation in KO mice subjected to TAC compared to the control. Further investigation confirmed that HuR regulates cyclin D1 mRNA stability in TGF-β1-stimulated cardiac fibroblasts, and deletion of HuR restricts myofibroblast proliferation in a cyclin D1-dependent manner. Conclusion: Our findings indicate that HuR plays a central role in the post-transcriptional regulation of cardiac fibrosis and could be a potential therapeutic target for clinical applications.