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Title: Cellular and Molecular Mechanisms of Aortic Valve Calcification
Author: Osman, Lana
ISNI:       0000 0001 3460 699X
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2008
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Aortic valve calcification is an active inflammatory condition characterised by thickening and calcification of the leaflets. The cellular and molecular mechanisms of the disease are unknown. We hypothesised that valve interstitial cells (lCs) playa key role in the calcification process by acting as a target for inflammatory cytokines that are involved in initiating signalling cascades to promote osteogenic differentiation of the cells, a mechanism that could be manipulated phannacologically. Calcified human aortic valve leaflets were characterised with the presence of calcium nodules and bone lesions. Cultured human aortic valve ICs had the capacity to release a number of inflammatory cytokines and undergo osteogenic differentiation in response to osteogenic mediators, including bone morphogenetic proteins (BMPs) and transforming growth factor-beta (TOF-P). In addition, extracellular nucleotides played an important role in regulating this differentiation process, whereby ATP increased the expression of osteoblast markers, while adenosine had an opposite effect. Activation of major signalling pathways including Wnt3a, were partially responsible for promoting this osteogenic differentiation of valve ICs, leading to upregulation of p-catenin and/or Cbfa-l. These mechanisms were counteracted by HMO-CoA reductase inhibitors (statins), where atorvastatin blocked the induction of osteoblast markers in valve ICs and inhibited the effects of Wnt3a on proliferation and differentiation. In addition, we demonstrated a novel role of pz-adrenergic receptors (Pz-ARs) in aortic valve calcification, whereby stimulation of pz-ARs prevented osteogenic differentiation of valve ICs in response to osteogenic medium. Our findings suggests that valve ICs play an important role in the calcification process and that activation of Wnt3a signalling pathway may present a possible mechanism for bone fonnation in the valve. This study also identifies potential pharmacological targets to prevent the onset or progression of aortic valve calcification.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available