Abstract 12003: TN-C Promotes Cardiac Fibrosis and Endothelial Dysfunction in Duchenne Muscular Dystrophy

Abstract

Background: Cardiac fibrosis and heart failure are major contributors to mortality in Duchenne muscular dystrophy (DMD) patients. Recently, it has been found that Tenascin C (TN-C) plays a maladaptive role in adverse left ventricular (LV) remodelling and fibrosis. Aims: To 1) elucidate the vascular dysfunction and cardiac fibrosis in link to TN-C in a mouse model of DMD and 2) explore the effect of knocking out TN-C in dystrophic mice. Methods: Male wt, mdx and mdx TN-C KO mice were used. Echocardiography was performed, and fibrosis was assessed on cardiac tissue sections. To test the vascular reactivity wire myography was used and CD31+ endothelial cells (ECs) were isolated from mouse lung tissues and characterized for oxidative stress and inflammatory marker expression. To explore further the signalling pathways contributing to cardiac fibrosis, human cardiac fibroblasts (hCFs) were treated with TN-C or TGF-β, then fibrotic markers and epigenetic regulation of p65 were assessed. Results: Cardiac fibrosis was markedly enhanced in mdx mice compared to age-matched wt animals. This was accompanied by upregulation of TN-C in cardiac tissue and plasma. In addition, vascular endothelial function was impaired in mdx mice. In line with that, endothelial cells isolated from mdx mice also showed a marked upregulation of oxidative stress and inflammatory markers. Interestingly, mdx- TN-C KO mice showed preserved vascular function as well as reduced cardiac fibrosis compared to age-matched mdx mice. hCFs treated with TN-C or TGF-β showed increased collagen production and elevated α-SMA and matrix metalloproteinase 2, 3 and 9 (MMP-2, 3 and 9) expressions. TN-C siRNA reduced the expression of collagen and α-SMA, but not MMPs. In addition, both TN-C and TGF-β promote p65/ NF-κB promoter demethylation and subsequently stimulate pro-inflammatory and pro-fibrotic signalling. These effects were reversed by applying p38 MAPK inhibitor in hCFs. Conclusions: TN-C facilitates oxidative stress and inflammation in ECs and fibroblasts, contributing to severe endothelial dysfunction and cardiac fibrosis. In addition, activation of NF-κB p65 signalling pathway may play a role in TN-C induced fibrosis. Thus, TN-C may be a critical mediator and potential target for therapy in DMD.