beta-catenin mediates mechanically regulated, transforming growth factor-beta1-induced myofibroblast differentiation of aortic valve interstitial cells.

摘要

OBJECTIVE: In calcific aortic valve disease, myofibroblasts and activation of the transforming growth factor-beta1 (TGF-beta1) and Wnt/beta-catenin pathways are observed in the fibrosa, the stiffer layer of the leaflet, but their association is unknown. We elucidated the roles of beta-catenin and extracellular matrix stiffness in TGF-beta1-induced myofibroblast differentiation of valve interstitial cells (VICs). METHODS AND RESULTS: TGF-beta1 induced rapid beta-catenin nuclear translocation in primary porcine aortic VICs in vitro through TGF-beta receptor I kinase. Degrading beta-catenin pharmacologically or silencing it with small interfering RNA inhibited TGF-beta1-induced myofibroblast differentiation without altering Smad2/3 activity. Conversely, increasing beta-catenin availability with Wnt3A alone did not induce differentiation. However, combining TGF-beta1 and Wnt3A caused greater myofibroblast differentiation than TGF-beta1 treatment alone. Notably, in VICs grown on collagen-coated PA gels with physiological stiffnesses, TGF-beta1-induced beta-catenin nuclear translocation and myofibroblast differentiation occurred only on matrices with fibrosa-like stiffness, but not ventricularis-like stiffness. In diseased aortic valves from pigs fed an atherogenic diet, myofibroblasts colocalized with increased protein expression of Wnt3A, beta-catenin, TGF-beta1, and phosphorylated Smad2/3 in the fibrosa. CONCLUSIONS: Myofibroblast differentiation of VICs involves matrix stiffness-dependent crosstalk between TGF-beta1 and Wnt signaling pathways and may explain in part why the stiffer fibrosa is more susceptible to disease.