K15 - Effects of Relaxin Receptor Agonism on Medial and Intimal Vascular Calcification

Introduction: : Vascular calcification, a hallmark of advanced cardiovascular disease, contributes to the rupture of atherosclerotic plaques—the primary cause of heart attacks. In addition to intimal calcification associated with atherosclerosis, medial calcification occurs in the smooth muscle-rich medial layer of arteries, particularly in patients with chronic kidney disease and diabetes, and is associated with vascular stiffening and increased cardiovascular risk. Despite its clinical importance, no approved therapeutics currently exist to treat or reverse vascular calcification. We previously proposed that relaxin, a vasoprotective and anti-fibrotic peptide hormone of the insulin/relaxin family, may represent a promising therapeutic strategy. However, recombinant relaxin suffers from poor bioavailability, short in vivo half-life, and high production costs, limiting its use in chronic conditions such as vascular calcification.

Materials and

Methods: : To overcome these limitations, we tested ML290, a small-molecule allosteric agonist of the human relaxin receptor (hRXFP1), previously shown to inhibit vascular calcification in vitro. This study evaluated the effects of ML290 on both medial and intimal vascular calcification using two distinct in vivo mouse models. Medial calcification was induced in humanized (hRXFP1/hRXFP1) mice through a high-adenine (0.2%) diet for 6 weeks, followed by a combined high-adenine (0.2%) and high-phosphate (1.8%) diet for the final 2 weeks. ML290 was administered daily via oral gavage (10 or 30 mg/kg) during the last 2 weeks. Intimal calcification was modeled via repeated injections of poloxamer-407 (P-407), a lipoprotein lipase inhibitor that induces hyperlipidemia and promotes atherosclerotic plaque formation. Humanized mice received P-407 (0.5 g/kg) every three days for 25 weeks, with ML290 administered orally every other day during the final 10 weeks.

Results, Conclusions, and Discussions:: ML290 treatment significantly (P = 0.0365) reduced medial vascular calcification in male mice with chronic kidney disease at a dosage of 30 mg/kg. In the P-407 mouse model of atherosclerosis, there was also a significant (P = 0.0152) reduction in intimal vascular calcification in male mice. These findings support the therapeutic potential of small-molecule relaxin agonists in preventing or treating multiple forms of vascular calcification.

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