Long noncoding RNA H19 is elevated in aortic valve stenosis and governs antigenic response and valvular endothelial cell phenotypes through endothelial to mesenchymal transition

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Abstract Background Long noncoding RNAs (lncRNAs) have emerged as important regulators of cardiovascular disease, including aortic valve stenosis (AVS). Endothelial to mesenchymal transition (EndMT) is a transdifferentiation process that is associated with the development of AVS in the elderly population. Although several recent studies have reported that lncRNAs are dysregulated and might play a crucial role in EndMT, no specific role of lncRNA was reported in AVS pathogenesis. Here, we sought to investigate the role of H19 in EndMT during the pathogenesis of AVS. Methods and results High-throughput lncRNA sequencing of human aortic valve tissue explanted from patients with AVS due to severe stenosis during surgical aortic valve replacement (SAVR) demonstrated that certain lncRNAs [H19, AGAP2-AS1 (PUNISHER), GAS5, MALAT1] are significantly dysregulated compared to patients without AVS. To validate the RNA-seq data, 60 patients with AVS (n=30) or without AVS (n=30) were prospectively investigated. Among these, H19 (p=0.002), AGAP2-AS1 (p=0.002), and GAS5 (0.02) were significantly upregulated in patients with AVS, compared to non-AVS patients. Aortic valvular endothelial cells (VECs) were isolated from explanted valve tissue from AVS patients or obtained commercially. In vitro EndMT-promoting stimuli (TNFα or TGFß+IL1ß) were used for VEC stimulation for 5 days. RT-qPCR was used to quantify the expression of EndMT markers (EC markers, vWF, and NOS3, and mesenchymal markers, αSMA, SM22, Vimentin, and SNAI2). Loss of H19 led to dysregulation of the EC gene network and protein expression patterns that were analyzed by qRT-PCR, immunoblotting, and immunofluorescence, respectively. Further experiments show that silencing of H19 affects migration and proliferation, and promotes EndMT in EC. Functional assays suggested that H19 is a critical regulator of angiogenic properties. The molecular signature of angiogenesis was investigated using a RT-qPCR-based angiogenesis array to identify the regulation of angiogenesis with 84-angiogenesis-related genes. Mechanistically, the angiogenesis array revealed that H19 regulates Jagged Canonical Notch Ligand 1 (JAG1) (4.43-fold vs. control EC), an important regulator of NOTCH1 signaling, and pro-angiogenic factor in EC. Accordingly, EndMT marker expressions were dysregulated upon H19 depletion. A high-throughput luciferase reporter array demonstrated STAT3 activation upon H19 knockdown. Depletion of H19 increased the phosphorylation of STAT3 at TYR705 and pharmacological inhibition of STAT3 activation abolished the effects of H19 silencing on EndMT marker expression as well as on angiogenesis. Overexpression of H19 in VEC abrogated the H19-mediated promotion of JAG1- and VEGFA gene- and protein expression.