Department of Maxillofacial Biomedical Engineering and Institute of Oral Biology, School of Dentistry, Kyung Hee University, Seoul 130-701, South Korea.
J Cell Biochem. 2011 Jul;112(7):1880-9. doi: 10.1002/jcb.23108.
Wnt/β-catenin signaling regulates various cellular events involved in the proliferation and differentiation and these events are affected sensitively by applying to mechanical stimuli. However, the mechanisms by which mechanical force stimulates cardiomyogenesis are not extensively explored. In this study we investigated the cellular mechanisms by which β-catenin signaling regulates cardiac differentiation of strain-subjected embryonic stem (ES) cells. The application of cells to cyclic strain increased beating cardiomyocyte foci with the attendant increases of Cx 43 and Nkx 2.5 proteins. Anti-oxidants such as vitamin C or N-acetyl cysteine (NAC) blocked the strain-mediated increases of Cx 43, Nkx 2.5, and α5/β1 integrins. These anti-oxidants also suppressed the activation of phosphoinositide 3-kinase (PI3K) and Akt in cyclic strain-subjected cells. Western blot analysis revealed that PI3K is a critical downstream effector of β1 integrin signaling and mediates Cx 43 and Nkx 2.5 expression in cyclic strain-applied ES cells. Cyclic strain increased the expression of β-catenin and stimulated its nuclear translocation from the cytosol, which was prevented by anti-oxidant treatment. In addition, the application to cyclic strain increased mRNA expression of β-catenin target genes, Axin2 and c-myc, as well as the phosphorylation of glycogen synthase kinase-3β. Furthermore, the blockage of β-catenin by its specific siRNA transfection diminished the cellular levels of Cx 43 and Nkx 2.5 proteins and the number of beating cardiomyocyte foci. Collectively, these results suggest that β-catenin-mediated signaling is required for cyclic strain-stimulated cardiomyogenesis through ROS-dependent and integrin-mediated PI3K-Akt signaling cascades.
Wnt/β-catenin 信号通路调节细胞的增殖和分化等各种细胞事件，这些事件对外力刺激非常敏感。然而，机械力刺激心肌发生的机制尚未得到广泛研究。在这项研究中，我们研究了β-catenin 信号通路调节应变诱导的胚胎干细胞（ES）细胞向心肌分化的细胞机制。细胞施加循环应变会增加搏动性心肌焦点，同时增加 Cx 43 和 Nkx 2.5 蛋白。抗氧化剂，如维生素 C 或 N-乙酰半胱氨酸（NAC），阻断了应变介导的 Cx 43、Nkx 2.5 和α5/β1 整合素的增加。这些抗氧化剂还抑制了循环应变细胞中磷酸肌醇 3-激酶（PI3K）和 Akt 的激活。Western blot 分析显示，PI3K 是β1 整合素信号的关键下游效应物，介导循环应变应用 ES 细胞中 Cx 43 和 Nkx 2.5 的表达。循环应变增加了β-catenin 的表达，并刺激其从细胞质向核内易位，抗氧化剂处理可阻止这一过程。此外，施加循环应变增加了β-catenin 靶基因 Axin2 和 c-myc 的 mRNA 表达，以及糖原合酶激酶-3β的磷酸化。此外，通过其特异性 siRNA 转染阻断β-catenin 减少了 Cx 43 和 Nkx 2.5 蛋白的细胞水平和搏动性心肌焦点的数量。总之，这些结果表明，β-catenin 介导的信号通路通过 ROS 依赖和整合素介导的 PI3K-Akt 信号级联反应，是循环应变刺激心肌发生所必需的。
