Abstract 15843: A Novel Role for Telomerase in Calcific Aortic Valve Disease

Abstract

Listen

Translate article

Introduction: Calcific aortic valve disease (CAVD) is a disorder characterized by the slow, but a progressive thickening of the aortic valve leaflet that develops into severe calcification. The only current therapy is aortic valve replacement. Telomerase is an enzymatic complex best known for its telomere-extending activities on the ends of chromosomes yet, the catalytic subunit (TERT) has been implicated in multiple non-canonical transcriptional and epigenetic activities, including priming of mesenchymal stem cells (MSCs) to differentiate into osteoblasts, and transcriptional regulation of inflammatory genes. Hypothesis: We hypothesize that non-canonical TERT activity contributes to the progression of CAVD. Methods: We performed biochemical assays to study the role of TERT in the calcification process using primary tissues and valve interstitial cells (VICs) from control and CAVD patients, smooth muscle cells (SMCs) from WT and Tert knockout mice, and mesenchymal stem cells (MSCs). Results: We found that TERT protein is highly expressed in calcified aortic valves and VICs isolated from patients with calcified valves, compared to healthy valves. VICs can be induced to calcify under osteogenic differentiation conditions, and we found that TERT accumulated after fourteen days in this culture, with no effect on either telomere length, proliferation, or senescence. We expanded the scope of our approach by evaluating TERT's influence on calcification of mice aortic smooth muscle cells (mSMCs). We found WT mSMCs readily calcified in vitro, but mSMCs from Tert knockout mice did not, and Tert deletion also reduced valve calcification in a Ldlr / Tert double knockout mice model compared to Ldlr knockout alone. In VICs, shRNA mediated TERT downregulation reduced expression of RUNX2 . Finally, we found that inflammatory signals intensify in vitro calcification, induce TERT expression, and we show evidence that TERT interacts with STAT5. Conclusion: Our data suggest that TERT is required for valve calcification by stimulating transcriptional pathways promoting the osteogenic transition of quiescent VICs into calcifying VICs in the aortic valve. These results indicate that TERT is an active contributor to the calcification process of valve tissues.