34Cardiorenal syndrome is defined by primary heart failure conditions influencing or 35 leading to renal injury or dysfunction. Dilated cardiomyopathy (DCM) is a major co-36 existing form of heart failure (HF) with renal diseases. Myocardin (MYOCD), a 37 cardiac-specific co-activator of serum response factor (SRF), is increased in DCM 38 mice and patient cardiac tissues and plays a crucial role in the pathophysiology of 39 DCM. Inhibiting the increased MYOCD has shown to be partially rescuing the DCM 40 mice phenotype. However, expression levels of MYOCD in the cardiac tissues of the 41 cardiorenal syndromic patients and the beneficial effect of inhibiting MYOCD in a 42 cardiorenal syndrome model remains to be explored. 43Here, we analyzed the expression levels of MYOCD in the DCM patients with and 44 without renal diseases. We also explored, whether cardiac specific silencing of 45 MYOCD expression could ameliorate the cardiac remodeling and improve cardiac 46 function in a renal artery ligated rat model (RAL). We observed an increase in 47 homing peptide conjugated MYOCD siRNA resulted in attenuation of cardiac 50 hypertrophy, fibrosis and restoration of the left ventricular functions. 51Our data suggest hyper-activation of MYOCD in the pathogenesis of the cardiorenal 52 failure cases. Also, MYOCD silencing showed beneficial effects by rescuing cardiac 53 hypertrophy, fibrosis, size and function in a cardiorenal rat model. 54
55Introduction 56 DCM is a major cause of HF, 1 accounting for nearly 1/3rd of total cases. Many of 57 these patients subsequently display kidney dysfunction or injury leading to 58 cardiorenal syndrome. More than half of the heart failure patients show renal 59 diseases. Co-existence of cardiac and renal dysfunction in the patients increases the 60 mortality significantly compared to cardiac or renal disease alone patients. 61Various molecular pathways including Renin-angiotensin-aldosterone system (RAAS) 62 are shown to be influencing the cardiorenal syndrome. Notably, circulating Ang II (an 63 essential component of RAAS) affects cardiac function by, increasing systemic 64 arteriolar vasoconstriction, vascular resistance, and cardiac afterload through AT1 65 receptor-mediated endothelial dysfunction 2 . 66Ang II has been shown to induce MYOCD under hypoxic condition 3 . MYOCD is a 67 cardiac-specific transcriptional co-activator present in cardiomyocytes and smooth 68 muscle cells. MYOCD is involved in heart development and cardiomyocyte 69 differentiation 4,5 . Also, MYOCD is required for maintenance of structural integrity, 70 cardiomyocyte survival, and heart function 5-7 . Besides, cardiomyocytes and smooth 71 muscle cells MYOCD expression has been detected in fibroblasts 8 . MYOCD has 72 been shown to promote fibroblast to myofibroblast differentiation and to inhibit cell 73 proliferation 9 . Forced expression of MYOCD in fibroblasts induces cardio-myogenic 74 4 properties alone 8 and/or in combination with other factors 10 . Transforming growth 75 factor (TGF-β) was shown to induc...