Abstract 5844: Cyclic Stretch and TGF-β1 Induce Aortic Valve Calcification via a Bone Morphogenic Protein Moderated Pathway
Introduction Calcified aortic valve (AV) cusps express high amounts of TGF-β1. We sought to understand if cyclic stretch in the presence of TGF-β1 initiates AV calcification through a BMP dependent pathway.
Methods Porcine AV cusps were stretched to 10% or 15% in osteogenic medium with 1 ng/mL TGF-β1 and with or without 100 ng/mL noggin, for 3 or 7 days. Samples were assayed for alkaline phosphatase (ALP) activity, Alizarin Red (AR) and von Kossa (vK). BMP-4 expression was analyzed by immunohistochemistry. Fresh and statically incubated cusps served as controls.
Results Tissue was viable under all conditions. All controls and 10% stretch groups were negative for AR and vK staining. At 15% stretch, AR and vK (see figure⇓) showed positive staining for calcification after 7 days in the presence of TGF-β1 only, but not in the presence of TGF-β1 and noggin. BMP-4 expression was higher on leaflets stretched at 15% compared to controls. ALP activities (in nmol/min/mg protein) are tabulated below:
Conclusion Stretch increased osteogenic differentiation of the AV cells and triggered calcification at the higher stretch level. Noggin inhibited these events. This study underlines the potential role of BMPs in valve calcification due to abnormal stretch loading, and as potential targets for pharmacological treatment of valve calcification.