Cardiac fibrosis is a commonly seen pathophysiological process in various cardiovascular disorders, such as coronary heart disorder, hypertension, and cardiomyopathy. Cardiac fibroblast trans-differentiation into myofibroblasts (MFs) is a key link in myocardial fibrosis. LncRNA PVT1 participates in fibrotic diseases in multiple organs; however, its role and mechanism in cardiac fibrosis remain largely unknown. Human cardiac fibroblasts (HCFs) were stimulated with TGF-β1 to induce myofibroblast; Immunofluorescent staining, Immunoblotting, and fluorescence in situ hybridization were used to detect the myofibroblasts phenotypes and lnc PVT1 expression. Cell biological phenotypes induced by lnc PVT1 knockdown or overexpression were detected by CCK-8, flow cytometry, and Immunoblotting. A mouse model of myocardial fibrosis was induced using isoproterenol (ISO), and the cardiac functions were examined by echocardiography measurements, cardiac tissues by H&E, and Masson trichrome staining. In this study, TGF-β1 induced HCF transformation into myofibroblasts, as manifested as significantly increased levels of α-SMA, vimentin, collagen I, and collagen III; the expression level of lnc PVT1 expression showed to be significantly increased by TGF-β1 stimulation. The protein levels of TGF-β1, TGFBR1, and TGFBR2 were also decreased by lnc PVT1 knockdown. Under TGF-β1 stimulation, lnc PVT1 knockdown decreased FN1, α-SMA, collagen I, and collagen III protein contents, inhibited HCF cell viability and enhanced cell apoptosis, and inhibited Smad2/3 phosphorylation. Lnc PVT1 positively regulated MYC expression with or without TGF-β1 stimulation; MYC overexpression in TGF-β1-stimulated HCFs significantly attenuated the effects of lnc PVT1 knockdown on HCF proliferation and trans-differentiation to MFs. In the ISO-induced myocardial fibrosis model, lnc PVT1 knockdown partially reduced fibrotic area, improved cardiac functions, and decreased the levels of fibrotic markers. In addition, lnc PVT1 knockdown decreased MYC and CDK4 levels but increased E-cadherin in mice heart tissues. lnc PVT1 is up-regulated in cardiac fibrosis and TGF-β1-stimulated HCFs. Lnc PVT1 knockdown partially ameliorates TGF-β1-induced HCF activation and trans-differentiation into MFs in vitro and ISO-induced myocardial fibrosis in vivo, potentially through interacting with MYC and up-regulating MYC.

Cardiac fibrosis is a common pathological feature of cardiac remodelling process with disordered expression of multiple genes and eventually lead to heart failure. Emerging evidence suggests that long noncoding RNAs (lncRNAs) have emerged as critical regulators of various biological processes. However, the exact mechanisms of lncRNAs as mediators in cardiac fibrosis have not been fully elucidated. This study aimed to profile the lncRNA expression pattern in human cardiac fibroblasts (HCFs) with cardiac fibrosis. We treated HCFs with transforming growth factor-β (TGF-β) to induce their activation. Then, strand-specific RNA-seq was performed to profile and classify lncRNAs; and perform functional analysis in HCFs. We study the transformation of HCFs with molecular and cell biology methods. Among all identified lncRNA candidates, 176 and 526 lncRNAs were upregulated and downregulated respectively in TGF-β-stimulated HCFs compared with controls. Functional analyses revealed that the target genes of differentially expressed lncRNAs were mainly related to focal adhesion, metabolic pathways, Hippo signaling pathway, PI3K-Akt signaling pathway, regulation of actin cytoskeleton, and hypertrophic cardiomyopathy. As a representative, novel lncRNAs NONHSAG005537 and NONHSAG017620 inhibited the proliferation, migration, invasion, and transformation of HCFs induced by TGF-β. Collectively, our study established the expression signature of lncRNAs in cardiac fibrosis and demonstrated the cardioprotective role of NONHSAG005537 and NONHSAG017620 in cardiac fibrosis, providing a promising target for anti-fibrotic therapy.