Mechanotransduction of bovine articular cartilage superficial zone protein by transforming growth factor β signaling
Mechanotransduction of bovine articular cartilage superficial zone protein by transforming growth factor β signaling
复制标题
DOI：
10.1002/art.23024
复制
发表时间：
2007-11-01
影响因子：
--
通讯作者：
Reddi, A. Hari
中科院分区：
文献类型：
--
作者：
Neu, Corey P.;Khalafi, Afshin;Reddi, A. Hari
目标。机械信号是再生医学中组织形态发生、维持和恢复策略的关键决定因素，尽管机械转导的分子机制仍有待阐明。本研究旨在探讨关节关键润滑剂浅带蛋白（SZP）的机械转导表达过程。SZP在未成熟牛股骨髁软骨中的区域表达首先通过免疫印迹法进行量化，并通过免疫组织化学可视化。采用压敏膜和载荷加载系统完成了整个接头的接触压力映射。在边界润滑条件下，使用用于往复滑动的销盘摩擦计测量软骨塞的摩擦。通过剪切载荷对关节软骨外植体进行直接机械刺激，同时抑制和不抑制转化生长因子β (TGF β)信号，并采用酶联免疫吸附法定量培养基中SZP的含量。一种意想不到的SZP定位于膝关节软骨的模式最初被发现，前区显示出高水平的SZP表达。区域SZP模式受机械信号调控，并与摩擦学行为相关。高水平的SZP表达、最大接触压力和低摩擦系数之间存在直接关系。SZP的表达和积累水平通过施加剪切应力而增加，这取决于膝关节内的位置，并通过使用TGF β受体I型激酶的特异性抑制剂和随后的phospho-Smad2/3活性将其降低到控制水平。这些发现提示了TGF β信号在细胞力学转导机制中的新作用，特别是在关节润滑中。
Objective. Mechanical signals are key determinants in tissue morphogenesis, maintenance, and restoration strategies in regenerative medicine, although molecular mechanisms of mechanotransduction remain to be elucidated. This study was undertaken to investigate the mechanotransduction process of expression of superficial zone protein (SZP), a critical joint lubricant.Methods. Regional expression of SZP was first quantified in cartilage obtained from the femoral condyles of immature bovines, using immunoblotting, and visualized by immunohistochemistry. Contact pressure mapping in whole joints was accomplished using pressure-sensitive film and a load application system for joint testing. Friction measurements on cartilage plugs were acquired under boundary lubrication conditions using a pin-on-disk tribometer modified for reciprocating sliding. Direct mechanical stimulation by shear loading of articular cartilage explants was performed with and without inhibition of transforming growth factor beta (TGF beta) signaling, and SZP content in media was quantified by enzyme-linked immunosorbent assay.Results. An unexpected pattern of SZP localization in knee cartilage was initially identified, with anterior regions exhibiting high levels of SZP expression. Regional SZP patterns were regulated by mechanical signals and correlated with tribological behavior. Direct relationships were demonstrated between high levels of SZP expression, maximum contact pressures, and low friction coefficients. Levels of SZP expression and accumulation were increased by applying shear stress, depending on location within the knee, and were decreased to control levels with the use of a specific inhibitor of TGF beta receptor type I kinase and subsequent phospho-Smad2/3 activity.Conclusion. These findings indicate a new role for TGF beta signaling in the mechanism of cellular mechanotransduction that is especially significant for joint lubrication.