ABSTRACT
OBJECTIVE: Aortic valve disease, including calcification, affects >2% of the human population and is caused by complex interactions between multiple risk factors, including genetic mutations, the environment, and biomechanics. At present, there are no effective treatments other than surgery, and this is because of the limited understanding of the mechanisms that underlie the condition. Previous work has shown that valve interstitial cells within the aortic valve cusps differentiate toward an osteoblast-like cell and deposit bone-like matrix that leads to leaflet stiffening and calcific aortic valve stenosis. However, the mechanisms that promote pathological phenotypes in valve interstitial cells are unknown. APPROACH AND RESULTS: Using a combination of in vitro and in vivo tools with mouse, porcine, and human tissue, we show that in valve interstitial cells, reduced Sox9 expression and nuclear localization precedes the onset of calcification. In vitro, Sox9 nuclear export and calcific nodule formation is prevented by valve endothelial cells. However, in vivo, loss of Tgfß1 in the endothelium leads to reduced Sox9 expression and calcific aortic valve disease. CONCLUSIONS: Together, these findings suggest that reduced nuclear localization of Sox9 in valve interstitial cells is an early indicator of calcification, and therefore, pharmacological targeting to prevent nuclear export could serve as a novel therapeutic tool in the prevention of calcification and stenosis.
Subject(s)
Aortic Valve Stenosis/metabolism , Aortic Valve/metabolism , Aortic Valve/pathology , Calcinosis/metabolism , Endothelial Cells/metabolism , Paracrine Communication , SOX9 Transcription Factor/metabolism , Signal Transduction , Transforming Growth Factor beta1/metabolism , Active Transport, Cell Nucleus , Animals , Aortic Valve Stenosis/genetics , Aortic Valve Stenosis/pathology , Aortic Valve Stenosis/prevention & control , Calcinosis/genetics , Calcinosis/pathology , Calcinosis/prevention & control , Cells, Cultured , Collagen Type II/genetics , Collagen Type II/metabolism , Endothelial Cells/pathology , Humans , Mice , Mice, Inbred C57BL , Mice, Knockout , SOX9 Transcription Factor/genetics , Swine , Time Factors , Tissue Culture Techniques , Transfection , Transforming Growth Factor beta1/genetics , rho-Associated Kinases/metabolismABSTRACT
Decellularized allograft heart valves have been used as tissue-engineered heart valve (TEHV) scaffolds with promising results; however, little is known about the cellular mechanisms underlying TEHV neotissue formation. To better understand this phenomenon, we developed a murine model of decellularized pulmonary heart valve transplantation using a hemodynamically unloaded heart transplant model. Furthermore, because the hemodynamics of blood flow through a heart valve may influence morphology and subsequent function, we describe a modified loaded heterotopic heart transplant model that led to an increase in blood flow through the pulmonary valve. We report host cell infiltration and endothelialization of implanted decellularized pulmonary valves (dPV) and provide an experimental approach for the study of TEHVs using mouse models.