The goal of the research proposed in this project is to identify the molecular mechanisms underlying aortic valve disease (AoVD) and potential therapeutic targets for the development of early medical treatment to halt AoVD progression and prevent the need for surgery. AoVD affects 2% of the United States population. In the aged, the prevalence of AoVD increases to greater than 10%.1 AoV replacement surgery is the most recommended treatment option for severe AoVD. Replacement valves are associated with complications. To date, there are no pharmacological treatment options that have been proven to prevent or delay the progression of AoVD in humans. In preliminary studies, COX2 (cyclooxygenase 2/prostaglandin- endoperoxide synthase 2) expression is increased in both human diseased AoV tissues as well as in AoV tissues from a mouse model of AoVD. Although COX2 is traditionally associated with the inflammatory process, it also plays a critical role in osteoblast differentiation and endochondral bone repair. COX2-/- mice have delayed fracture healing and defects in osteoblastogenesis. In bone, COX2 catalyzes the first committed step in the synthesis of prostaglandin E2, which signals via the EP2 receptor to phosphorylate p-38 MAPK, which subsequently activates an osteogenic pathway necessary for new bone formation. To test the hypothesis that increased expression of COX2 mediates an osteogenic-like differentiation of the aortic valvular interstitial cells (VICs), leading to pathogenic AoV calcification, three specific aims are proposed. (1) Determine if COX2 expression in aortic VICs is coincident with the induction of an osteogenic gene expression profile. (2) Determine if COX2 expression is necessary and sufficient to promote osteogenic differentiation in mouse VICs via the EP2/p-p38 MAPK pathway. (3) Determine if COX2 inhibition prevents the onset of, and halts the progression of existing, AoVD calcification in vivo. The proposed studies will determine whether COX2 is necessary for the process of pathologic AoVD calcification and if inhibition of COX2 prevents, or halts the progression of, AoV calcification. Understanding the molecular basis of AoV calcification will provide insight into AoVD progression and will identify potential pharmacological therapeutic targets, which may have future clinical implications in non-invasive treatment of AoVD.