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Introduction: Adverse extracellular matrix remodeling following hypertension is mainly attributed to activation of cardiac fibroblasts, leading to myocardial stiffening with concomitant decline of diastolic performance. Here, we developed a novel anti-fibrotic therapeutic strategy based on natural compounds library screens for the treatment of diastolic heart failure. Methods: Anti-fibrotic molecules were identified in human cardiac fibroblasts (HCF) applying a functional screen of 480 nature-derived substances and subsequent stringent selection criteria. Anti-fibrotic and fibroblast-specific actions were confirmed in vivo in a murine angiotensin II-induced model of cardiac fibrosis both in preventive and therapeutic studies. Beneficial effects of the substances on diastolic function were followed using tissue Doppler and strain imaging, assessment of mitral inflow velocities and -patterns and hemodynamic measurements. Additionally, investigations were performed using the clinically relevant Dahls rat. To investigate the mechanism underlying the anti-fibrotic potential of the lead compounds, treatment-depended changes in the miRnome in primary HCFs were analyzed by small non coding RNA deep sequencing. Results: Protective anti-fibrotic effects for substances within the library-screen were identified for the compounds bufalin and lycorine, which could be validated in HCFs in vitro and in a hypertensive murine model in preventive and in therapeutic approaches. Bufalin and lycorine were taken up by the heart upon systemic delivery. Administration of both substances did not provoke any changes in the morphology of kidney and liver, providing first promising data of toxicological assessment. Neither bufalin nor lycorine showed any impact on hypertension induced by angiotensin II. Importantly, cardio protection could be validated in the Dahls rat model for HFpEF. The highly conserved miRNA-671-5p was determined as a common and functionally important effector in the fibrotic response in HCFs after bufalin or lycorine treatment. Mechanistically, miRNA-671-5p repressed the anti-fibrotic Selenoprotein P1. Conclusions: Collectively, we provide evidence for cardio protective, anti-fibrotic and promising toxicological profile of the natural compounds bufalin and lycorine in two rodent models of diastolic dysfunction. The anti-fibrotic natural compounds negatively modulate a pro-fibrotic key-player, miRNA-671-5p, which drives fibrosis via repression of its anti-fibrotic target, Selenoprotein P1. [ABSTRACT FROM AUTHOR]

Background: Pathogenic concepts of right ventricular (RV) failure in pulmonary arterial hypertension focus on a critical loss of microvasculature. However, the methods underpinning prior studies did not take into account the 3-dimensional (3D) aspects of cardiac tissue, making accurate quantification difficult. We applied deep-tissue imaging to the pressure-overloaded RV to uncover the 3D properties of the microvascular network and determine whether deficient microvascular adaptation contributes to RV failure., Methods: Heart sections measuring 250-µm-thick were obtained from mice after pulmonary artery banding (PAB) or debanding PAB surgery and properties of the RV microvascular network were assessed using 3D imaging and quantification. Human heart tissues harvested at the time of transplantation from pulmonary arterial hypertension cases were compared with tissues from control cases with normal RV function., Results: Longitudinal 3D assessment of PAB mouse hearts uncovered complex microvascular remodeling characterized by tortuous, shorter, thicker, highly branched vessels, and overall preserved microvascular density. This remodeling process was reversible in debanding PAB mice in which the RV function recovers over time. The remodeled microvasculature tightly wrapped around the hypertrophied cardiomyocytes to maintain a stable contact surface to cardiomyocytes as an adaptation to RV pressure overload, even in end-stage RV failure. However, microvasculature-cardiomyocyte contact was impaired in areas with interstitial fibrosis where cardiomyocytes displayed signs of hypoxia. Similar to PAB animals, microvascular density in the RV was preserved in patients with end-stage pulmonary arterial hypertension, and microvascular architectural changes appeared to vary by etiology, with patients with pulmonary veno-occlusive disease displaying a lack of microvascular complexity with uniformly short segments., Conclusions: 3D deep tissue imaging of the failing RV in PAB mice, pulmonary hypertension rats, and patients with pulmonary arterial hypertension reveals complex microvascular changes to preserve the microvascular density and maintain a stable microvascular-cardiomyocyte contact. Our studies provide a novel framework to understand microvascular adaptation in the pressure-overloaded RV that focuses on cell-cell interaction and goes beyond the concept of capillary rarefaction., Competing Interests: Disclosures None.