Abstract 12316: Carnitine O-octanoyltransferase Inhibition Attenuates Human Aortic Valve Interstitial Cell Calcification by Correcting Energetic Mitochondrial State

Abstract

Background: Cardiovascular calcification is a critical pathology associated with increased cardiovascular risk, but there are no FDA-approved anti-calcification therapies. Through an unbiased screening approach, we previously identified carnitine O-octanoyltransferase (CROT) as a novel contributing factor to vascular calcification, but whether it can inhibit calcification in cardiac valves remains unknown. Here we investigated CROT-associated mechanisms of calcification in human valvular interstitial cells (VICs). Methods and Results: Human VICs were isolated from aortic valve leaflets of patients undergoing valve replacement surgeries at Brigham and Women’s Hospital, and cultured in osteogenic medium (OM) to induce calcification. OM increased CROT mRNA expression (1.83±0.41 fold-change; p<0.05). Tissue-nonspecific alkaline phosphatase activity, a key regulator of calcification, was also increased by OM (8.80±3.81 fold-change; p<0.001) and reduced by CROT siRNA treatment (0.48±0.19 fold-change; p<0.01). CROT siRNA decreased calcium deposition (Alizarin red staining; >99.9%; p<0.001). We previously showed that mitochondria dysfunction contributes to vascular calcification. We therefore, assessed mitochondrial function in VICs by measuring oxygen consumption rate and extracellular acidification rate. Basal and maximal respiration, spare respiratory capacity and ATP production increased in VICs after OM stimulation (1.73±0.48, p<0.01; 1.75±0.34, p<0.01; 2.11±0.63, p<0.05; 1.75±0.38, p<0.05; respectively), indicating mitochondrial dysfunction. These parameters were corrected to normal state followed by CROT siRNA treatment. The combined data of oxygen consumption and extracellular acidification rates indicated that osteogenic condition induced mitochondria energetic state that was corrected to quiescent state by CROT siRNA treatment. Conclusions: CROT promotes calcification of human aortic VICs. CROT inhibition attenuates the calcification of VICs via correcting mitochondrial dysfunction induced by osteogenic environment. CROT inhibition is an attractive approach as a therapy for aortic valve calcification, a major unmet medical need.