ADAMTSL3 knock-out (L3-/-) and WT control mice were subjected to aortic banding (AB) or sham operation for six weeks (n=92). Cardiac function was examined using echocardiography and magnetic resonance imaging (MRI), and left ventricular tissues was harvested at six weeks for RNA-sequencing.. ADAMTSL3 KO mouse +/- aortic banding LV RNA-sequencing

Background/Introduction Dilated cardiomyopathy (DCM) affects as many as 1 in 250 Europeans and is considered a main cause of systolic heart failure. Cardiac remodelling including fibrosis is a hallmark of DCM. Fibrosis is caused bv extracellular matrix (ECM) expansion by activated cardiac fibroblasts (CFBs), so-called myofibroblasts. The ADAMTSL (a disintegrin and metalloproteinase with thrombospondin motif like) protein family are secreted, ECM glycoproteins with an unknown role in the heart. Here we hypothesized that they are important regulators of myofibroblast function and pathological remodelling of the heart. Purpose The purpose of this study was to investigate the regulation and role of ADAMTSL3 in DCM, fibrosis, transforming growth factor (TGF) signalling and CFB function. Methods ADAMTSL3 mRNA was examined in left ventricular (LV) biopsies from patients with ischemic DCM (n=9) and wild-type (WT) mice with heart failure. ADAMTSL3 knock-out (L3-/-) and WT control mice were subjected to aortic banding (AB) or sham operation for six weeks (n=92). Cardiac function was examined using echocardiography and magnetic resonance imaging (MRI), and hearts were harvested at one or six weeks for organ weights and molecular analyses, including qPCR, immunoblotting, RNA-sequencing and mass spectrometry (MS). Cardiomyocytes from adult mice were analysed for size and calcium transients. ADAMTSL3 was over-expressed using adenoviral constructs in cultures of human CFBs producing a mature ECM. Cell migration, proliferation and collagen gel contraction experiments were performed, alongside molecular profiling. Results Cardiac ADAMTSL3 mRNA was increased in LVs of patients with iDCM and WT mice with hypertrophic remodelling, dilatation and contractile dysfunction. L3-/- mice did not show a cardiac phenotype at baseline. Importantly, L3-/- mice developed exacerbated DCM after AB, with decreased contractility and increased LV mass and dilatation from one week, and higher mortality from three weeks compared to WT. RNA-sequencing of LVs one week post-AB showed 233 differentially expressed genes (DEGs) comparing L3-/- to WT, where Nppa, Col1a1, Postn, Ttn and Ryr2 were among the most up-regulated, suggesting increased heart failure, fibrosis, TGF signalling, cardiomyocyte remodelling and calcium dysregulation, respectively. ADAMTSL3 over-expression in cultured human CFBs resulted in reduced migration, proliferation and collagen gel contraction, and the myofibroblast differentiation markers ACTA2 and SPP1 were reduced to 60 and 10% of controls, respectively. Conclusions We show that cardiac ADAMTSL3 levels were increased in clinical and experimental DCM. L3-/- mice developed exacerbated DCM in response to pressure overload, suggesting ADAMTSL3 to be important for DCM pathogenesis and survival. Increased ADAMTSL3 levels in cultured human CFBs resulted in an anti-fibrotic profile. Altogether, our results suggest a cardio-protective role of the ECM glycoprotein ADAMTSL3 in the failing heart.