AUTHOR=Liu Yamin , Afzal Junaid , Vakrou Styliani , Greenland Gabriela V. , Talbot C. Conover , Hebl Virginia B. , Guan Yufan , Karmali Rehan , Tardiff Jil C. , Leinwand Leslie A. , Olgin Jeffrey E. , Das Samarjit , Fukunaga Ryuya , Abraham M. Roselle 

TITLE=Differences in microRNA-29 and Pro-fibrotic Gene Expression in Mouse and Human Hypertrophic Cardiomyopathy

JOURNAL=Frontiers in Cardiovascular Medicine

VOLUME=6

YEAR=2019

URL=https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2019.00170

DOI=10.3389/fcvm.2019.00170

ISSN=2297-055X

ABSTRACT=<p><bold>Background:</bold> Hypertrophic cardiomyopathy (HCM) is characterized by myocyte hypertrophy and fibrosis. Studies in two mouse models (R92W-TnT/R403Q-MyHC) at early HCM stage revealed upregulation of endothelin (ET1) signaling in both mutants, but TGFβ signaling only in TnT mutants. Dysregulation of miR-29 expression has been implicated in cardiac fibrosis. But it is unknown whether expression of miR-29a/b/c and profibrotic genes is commonly regulated in mouse and human HCM.</p><p><bold>Methods:</bold> In order to understand mechanisms underlying fibrosis in HCM, and examine similarities/differences in expression of miR-29a/b/c and several profibrotic genes in mouse and human HCM, we performed parallel studies in rat cardiac myocyte/fibroblast cultures, examined gene expression in two mouse models of (<italic>non-obstructive</italic>) HCM (R92W-TnT, R403Q-MyHC)/controls at early (5 weeks) and established (24 weeks) disease stage, and analyzed publicly available mRNA/miRNA expression data from <italic>obstructive</italic>-HCM patients undergoing septal myectomy/controls (unused donor hearts).</p><p><bold>Results:</bold> Myocyte cultures: ET1 increased superoxide/H<sub>2</sub>O<sub>2</sub>, stimulated TGFβ expression/secretion, and suppressed miR-29a expression in myocytes. The effect of ET1 on miR-29 and TGFβ expression/secretion was antagonized by N-acetyl-cysteine, a reactive oxygen species scavenger. Fibroblast cultures: ET1 had no effect on pro-fibrotic gene expression in fibroblasts. TGFβ1/TGFβ2 suppressed miR-29a and increased collagen expression, which was abolished by miR-29a overexpression. Mouse and human HCM: Expression of miR-29a/b/c was lower, and <italic>TGFB1</italic>/collagen gene expression was higher in TnT mutant-LV at 5 and 24 weeks; no difference was observed in expression of these genes in MyHC mutant-LV and in human myectomy tissue. <italic>TGFB2</italic> expression was higher in LV of both mutant mice and human myectomy tissue. <italic>ACE2</italic>, a negative regulator of the renin-angiotensin-aldosterone system, was the most upregulated transcript in human myectomy tissue. Pathway analysis predicted upregulation of the anti-hypertrophic/anti-fibrotic liver X receptor/retinoid X receptor (LXR/RXR) pathway only in human myectomy tissue.</p><p><bold>Conclusions:</bold> Our <italic>in vitro</italic> studies suggest that activation of ET1 signaling in cardiac myocytes increases reactive oxygen species and stimulates TGFβ secretion, which downregulates miR-29a and increases collagen in fibroblasts, thus contributing to fibrosis. Our gene expression studies in mouse and human HCM reveal allele-specific differences in miR-29 family/profibrotic gene expression in mouse HCM, and activation of anti-hypertrophic/anti-fibrotic genes and pathways in human HCM.</p>