Mechanisms of Integrin α2β1 driven cell-matrix interaction in the course of bone regeneration and fracture healing

整合素是一类具有良好特征的异二聚体细胞粘附和信号转导蛋白，具有受体、黏附成分和机械信号转导功能。整合素α2β1是骨原纤维胶原的主要受体。最近我们可以证明，在缺乏这种蛋白质的情况下，骨形成细胞会产生更多的基质，即I型胶原蛋白，从而减轻与年龄相关的骨退化的影响。为了将其转化为临床问题，我们想研究整合素α2β1在骨折修复中的作用。在初步研究中，我们可以证明，骨折后7天，整合素α2β1缺失的骨愈合似乎更先进。骨折愈伤组织进一步发育，在骨折愈伤组织中可以检测到更多的整体胶原蛋白。该项目的目的是确定加速骨折修复是否持续到整体临床结果。进一步的研究将阐明整合素α2β1依赖性i型胶原过表达的分子机制，因此我们将研究一个众所周知的参与胶原和骨基质表达的途径，TGFβ和相应的bmp -途径。这将通过体外分析TGF-β或BMP抑制下胶原蛋白和骨靶基因的表达来完成。最后，我们将通过体外和体外外源性抑制整合素α2β1将这些发现转化为临床应用。我们选择了rhodocetin作为效应剂，rhodocetin是一种有效且稳定的蛇毒化合物，具有高度特异性的整合素α2β1抑制作用，也是整合素α2β1阻断抗体的替代方法。通过这些研究提高骨折的修复效果可能是治疗骨质疏松性和不愈合性骨折的新方法。

Integrins, a well characterized family of heterodimeric cell adhesion and signal transduction proteins, serve as receptors, focal adhesion components and transducers of mechanical signals. Integrin α2β1 is the major receptor for fibrillary collagens in bone. Recently we could show that in the absence of this protein bone forming cells are primed to produce more matrix i.e. collagen type I which alleviates the effects of age related bone degradation. To transfer this to a clinical problem, we want to investigate the role of integrin α2β1 in fracture repair. In preliminary studies we could demonstrate that 7 days after fracture healing in the integrin α2β1 deficient bone appears to be more advanced. The fracture callus is further developed, and we could detect more overall collagen in the fracture callus. The aim of this project is to determine whether the accelerated fracture repair continues to the overall clinical outcome. Further investigations will elucidate the molecular mechanisms which are involved in the integrin α2β1 dependent over-expression of collagen type I. Therefore we will investigate a well-known pathway involved in expression of collagen and bone matrix, the TGFβ and accordingly the BMP-pathway. This will be done by in-vitro analyzation of the expression of collagen and bone target genes under inhibition of either TGF-β or BMP. Finally we will translate these findings into clinical application by exogenous inhibition of integrin α2β1 in vitro as well as in vitro. As effector we have chosen rhodocetin, a potent and stable compound of snake venom with highly specific integrin α2β1 inhibition as well as an alternative approach with integrin α2β1 blocking antibody. Improving the outcome of fracture repair by these investigations could be a novel therapeutic approach to treat osteoporotic and non-healing fractures.