Abstract 14232: The Cathepsin D-m6pr-erk1/2 Pathway Mediates Cellular Senescence and Osteogenic Activities in Human Aortic Valve Interstitial Cells

Background: Calcific aortic valve disease (CAVD) is one of the most prevalent cardiovascular disorders in the elderly, and aortic valve interstitial cells (AVICs) play a major role in valvular calcification associated with CAVD progression. Recent studies found that pharmacological or genetic clearance of senescent cells attenuates aortic valve calcification in animal models, indicating an important role of senescent cells in promoting valvular calcification. However, the mechanism underlying cellular senescence in aortic valves is unclear. Our pilot work found that greater densities of senescent cells in AVIC isolates from diseased human aortic valves are associated with elevated levels of matrilin 2 and cathepsin D in AVICs. We tested the hypothesis that matrilin 2 and cathepsin D mediate the senescence and osteogenic responses in human AVICs. Methods and Results: AVICs were isolated from normal and diseased aortic valves. Levels of P16 were assessed by immunoblotting, and senescent changes is examined using senescence-associated β-galactosidase (SA-β-gal) staining. AVICs from diseased valves displayed higher levels of P16 and greater SA-β-gal staining. Both recombinant human matrilin 2 (2.0 μg/ml) and recombinant human cathepsin D (40 nM) promoted P16 expression and enhanced SA-β-gal staining in normal AVICs, leading to greater calcium deposition. Knockdown of cathepsin D reduced matrilin-2-induced P16 expression, SA-β-gal staining and calcium deposition in normal AVICs. Moreover, recombinant cathepsin D activated the M6PR-ERK1/2 pathway in normal AVICs. Blocking or knockdown of M6PR (M6P, 10 mM or siRNA, 1.0 nM) or inhibition of ERK1/2 (PD98059, 25 μM) attenuated the effect of cathepsin D on AVIC senescent change and associated osteogenic activation. Conclusion: AVICs of aortic valves from patients with CAVD have higher levels of senescence activity. Cathepsin D mediates AVIC senescence and associated osteogenic activation through the M6PR-ERK1/2 pathway and is involved in the mechanism by which soluble matrilin 2 promotes cellular senescence and osteogenic activity in human AVICs. Targeting the cathepsin D-M6PR-ERK1/2 cascade may suppress AVIC senescence activity and attenuate aortic valve calcification.