Abstract 17021: A Novel Human Relaxin Receptor Agonist, ML290, Attenuates Atherosclerosis- and Chronic Kidney Disease-Induced Vascular Calcification in Mice

Abstract

Introduction: Vascular calcification is the most significant predictor of cardiovascular morbidity and mortality, but therapeutic options are unavailable. Relaxin has emerged as a vasoprotective molecule, but several drawbacks prevent therapeutic translation. Targeting the relaxin receptor, RXFP1, is safe and well-tolerated in animal models of vascular disease and humans. We identified a biased allosteric agonist of human RXFP1, ML290, and aimed to test the hypothesis that ML290 arrests the progression of vascular calcification in mouse models of atherosclerosis and chronic kidney disease (CKD). Methods and Results: Recurrent treatment with ML290 significantly prevented ( P = 0.0422, n = 8) and reversed ( P = 0.0489, n = 6) atherosclerotic calcification in humanized ( hRXFP1/hRXFP1 ) Apoe -/- mice fed an atherogenic diet. Longitudinal tracing of mineral formation in the aortic arch of these mice revealed the presence of mineral in vehicle- but not ML290-treated mice after 15 weeks of diet. Accelerated mineral growth was observed in vehicle-treated mice after 20 weeks of the diet, which was reduced by ML290 treatment. In humanized mice with CKD, ML290 significantly prevented ( P = 0.0344, n = 9) medial calcification. In vitro , ML290 reduced ( P = 0.0005, n = 3) superoxide production under osteogenic conditions in vascular smooth muscle cells (VSMCs). Osteogenic changes in VSMC phenotype associate with a release of alkaline phosphatase (ALP) in extracellular vesicles (EVs), which promote mineralization. ML290 treatment significantly ( P = 0.0001, n = 3) suppressed the formation of ALP-loaded EVs in vitro . Bone morphogenetic protein-4, an inducer of osteogenic transitions, and caveolin-1, a scaffolding protein required for calcifying EV formation, were significantly ( P = 0.0059, n = 4) down-regulated after 24 h treatment with ML290 compared to vehicle-treated VSMCs under osteogenic conditions. Conclusions: We demonstrate the therapeutic potential for ML290 to mitigate atherosclerosis and CKD-induced vascular calcification in vivo . The actions of ML290 to prevent medial calcification are in part attributed to its ability to limit the release of calcifying EVs as a result of osteogenic differentiation, and to reduce vascular superoxide production.