COX-2 Is Downregulated in Human Stenotic Aortic Valves and Its Inhibition Promotes Dystrophic Calcification

Abstract

Calcific aortic valve disease (CAVD) is the result of maladaptive fibrocalcific processes leading to a progressive thickening and stiffening of aortic valve (AV) leaflets. CAVD is the most common cause of aortic stenosis (AS). At present, there is no effective pharmacotherapy in reducing CAVD progression; when CAVD becomes symptomatic it can only be treated with valve replacement. Inflammation has a key role in AV pathological remodeling; hence, anti-inflammatory therapy has been proposed as a strategy to prevent CAVD. Cyclooxygenase 2 (COX-2) is a key mediator of the inflammation and it is the target of widely used anti-inflammatory drugs. COX-2-inhibitor celecoxib was initially shown to reduce AV calcification in a murine model. However, in contrast to these findings, a recent retrospective clinical analysis found an association between AS and celecoxib use. In the present study, we investigated whether variations in COX-2 expression levels in human AVs may be linked to CAVD. We extracted total RNA from surgically explanted AVs from patients without CAVD or with CAVD. We found that COX-2 mRNA was higher in non-calcific AVs compared to calcific AVs (0.013 ± 0.002 vs. 0.006 ± 0.0004; p < 0.0001). Moreover, we isolated human aortic valve interstitial cells (AVICs) from AVs and found that COX-2 expression is decreased in AVICs from calcific valves compared to AVICs from non-calcific AVs. Furthermore, we observed that COX-2 inhibition with celecoxib induces AVICs trans-differentiation towards a myofibroblast phenotype, and increases the levels of TGF-β-induced apoptosis, both processes able to promote the formation of calcific nodules. We conclude that reduced COX-2 expression is a characteristic of human AVICs prone to calcification and that COX-2 inhibition may promote aortic valve calcification. Our findings support the notion that celecoxib may facilitate CAVD progression.