title: Elevated cyclic stretch induces aortic valve calcification in a bone morphogenic protein-dependent manner.
abstract: Calcified aortic valve (AV) cusps have increased expression of bone morphogenic proteins (BMPs) and transforming growth factor-beta1 (TGF-beta1). Elevated stretch loading on the AV is known to increase expression of matrix remodeling enzymes and pro-inflammatory proteins. Little, however, is known about the mechanism by which elevated stretch might induce AV calcification. We investigated the hypothesis that elevated stretch may cause valve calcification via a BMP-dependent mechanism. Porcine AV cusps were cultured in a stretch bioreactor, at 10% (physiological) or 15% (pathological) stretch and 70 beats per minute for 3, 7, and 14 days, in osteogenic media supplemented with or without high phosphate (3.8 mmol/L), TGF-beta1 (1 ng/ml), as well as the BMP inhibitor noggin (1, 10, and 100 ng/ml). Fresh cusps served as controls. Alizarin red and von Kossa staining demonstrated that 15% stretch elicited a stronger calcification response compared with 10% stretch in a fully osteogenic medium containing high phosphate and TGF-beta1. BMP-2, -4, and Runx2 expression was observed after 3 days on the fibrosa surface of the valve cusp and was stretch magnitude-dependent. Cellular apoptosis was highest at 15% stretch. Tissue calcium content and alkaline phosphatase activity were similarly stretch-dependent and were significantly reduced by noggin in a dose dependent manner. These results underline the potential role of BMPs in valve calcification due to altered stretch.
authors.affiliation: The Wallace H. Coulter School of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Dr, Suite 1121, Atlanta, GA 30332-0535, USA.
authors.forename: Kartik
authors.initials: K
authors.lastname: Balachandran
authors.forename: Philippe
authors.initials: P
authors.lastname: Sucosky
authors.forename: Hanjoong
authors.initials: H
authors.lastname: Jo
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001021:Aortic Valve / Q000166:cytology / Q000378:metabolism / Q000473:pathology*; D017209:Apoptosis; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002114:Calcinosis / Q000378:metabolism / Q000473:pathology*; D002118:Calcium / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D010507:Periodicity; D013314:Stress, Mechanical; D013552:Swine; D013718:Tensile Strength; D046509:Tissue Culture Techniques
chemical_list: D019485:Bone Morphogenetic Proteins; D003470:Culture Media; D000469:Alkaline Phosphatase; D002118:Calcium