O30 Long non-coding RNA HOTAIR induces beta catenin expression in systemic sclerosis through EZH2 dependent repression of Axin-2

Abstract

Abstract Background Fibroblasts explanted from affected tissues in systemic sclerosis (SSc) maintain their pro-fibrotic phenotype in vitro. This includes increased secretion of collagens and other extracellular matrix proteins and increased proportion of α-Smooth Muscle Actin (α-SMA) positive cells (myofibroblasts). It has been previously shown that among their profibrotic features, myofibroblasts display activation of WNT signalling, which is linked to a decreased basal expression of AXIN2. Here we aimed to determine whether specific long non-coding RNA (lncRNAs) expressed in myofibroblasts could drive the epigenetically stable decreased expression of Axin 2 in vitro. Methods Full thickness skin biopsies were surgically obtained from the forearms of twelve adult patients with SSc of recent onset. Fibroblasts were isolated and cultured in monolayers and protein and RNA extracted from the fibroblast cultures. Laser capture was performed to isolate cells expressing or not α-SMA as a marker of myofibroblast differentiation. LncRNA HOTAIR was overexpressed in healthy dermal fibroblasts by lentiviral induction. EZH2 was blocked in cultured fibroblasts with the specific inhibitor GSK126. Results HOTAIR expression was increased in SSc patients’ skin (100 fold) and in SSc explanted fibroblasts (5 fold; p < 0.001 for both). Further, laser captured α-SMA expressing fibroblasts expressed in average 2.5 fold higher HOTAIR RNA levels compared to α -SMA negative cells from the same donors (P < 0.05). In vitro, lentiviral induced stable overexpression of HOTAIR in healthy dermal fibroblasts led to their profibrotic activation, including significantly increased expression of Col1A1 and α-SMA both at mRNA and protein levels (2.8 and 1.8 fold respectively, p < 0.05). We further showed that HOTAIR-induced profibrotic activation was due to EZH2 dependent spread of H3k27me3 methylation marker, as demonstrated by complete inhibition by treatment with GSK126. HOTAIR driven EZH2 histone methylation suppressed the expression of Axin 2 in SSc fibroblasts. The reduced Axin 2 levels led to stabilisation of beta catenin and WNT signalling pathway activation. Conclusion Here we show that the epigenetically stable activation of SSc dermal fibroblasts is due to HOTAIR. We also identified a major downstream target of HOTAIR is Axin-2. The results of these studies identify a new venue to modulate fibroblasts biology which could inform clinical research to resolve chronic fibrosis and re-establish tissue homeostasis in SSc. Disclosures C.W. Wasson None. G. Abignano None. R. Ross None. F. Del Galdo Consultancies; AstraZeneca, GSK, Boehringer-Ingelheim, Actelion, Capella Biosciences, Chemomab.