The role of WAVE Complex in osteoclast-mediated bone destruction in experimental arthritis

迁移、粘附以及胞内和胞吐都依赖于肌动蛋白细胞骨架的动态重组，可能涉及肌动蛋白成核剂如Arp 2/3-复合物及其激活剂如WAVE-复合物。为了研究WAVE复合物在造血系统中的作用，我们已经产生了小鼠，其中编码WAVE复合物的唯一造血特异性亚单位Hem 1的基因被删除。到3个月大时，Hem 1-/-小鼠表现出淋巴细胞减少症、贫血和髓外骨髓生成，患有全身性炎症并过早死亡。此外，我们的初步结果表明，Hem 1-/-小鼠已开发出一个异常的骨表型。尽管Hem 1缺陷型破骨细胞在体外和体内的形成似乎得到了促进，但它们降解骨基质的能力却受到了损害。基于这些发现，结合Hem 1在慢性破坏性关节炎中表达增加的观察结果，我们想研究Hem 1如何介导破骨细胞分化和骨破坏，以及它是否在类风湿关节炎（RA）的发病机制中发挥作用。特别是，我们希望遵循的假设，即增加表达的Hem 1在关节炎关节与骨破坏在慢性炎症性关节炎。此外，我们想确定破骨细胞或巨噬细胞中Hem 1的丢失在多大程度上影响小鼠关节炎的发展。为此，我们将通过将它们与hTNF α依赖性关节炎小鼠杂交或通过K/BxN血清转移在总巨噬细胞特异性和破骨细胞特异性Hem 1-/-小鼠中诱导关节炎，并通过形态学、组织学和免疫组织化学方法分析疾病（例如炎症、滑膜增生、骨侵蚀）的发展和严重程度。此外，Hem 1对破骨细胞分化和/或破骨细胞融合的假定抑制作用将被检查。该项目将为炎症性骨破坏的机制提供新的见解，并促进慢性炎症性疾病，特别是RA的新治疗策略的发展。

Migration, adhesion as well as endo- and exocytosis all critically depend on dynamic reorganization of the actin cytoskeleton, potentially involving actin nucleators like Arp2/3-complex and its activators such as WAVE-complex. In order to investigate the role of WAVE-complex in the hematopoietic system, we have generated mice in which the gene encoding the only hematopoietic-specific subu-nit of WAVE-complex, Hem1, is deleted. By 3 months of age, Hem1-/- mice display lymphopenia, anaemia and extramedullary myelopoiesis, suffer from systemic inflammation and die prematurely. In addition, our preliminary results demonstrate that Hem1-/- mice have developed an aberrant bone-phenotype. Whereas the formation both in vitro and in vivo of Hem1-deficient osteoclasts seems to be promoted, their ability to degrade bone matrix is impaired. Based on these findings, combined with the observation that there is an increase in expression of Hem1 in chronic destructive arthritis, we want to study how Hem1 mediates osteoclast differentiation and bone destruktion and whether it plays a role in rheumatoid arthritis (RA) pathogenesis. In particular, we want to follow the hypothesis that the increased expression of Hem1 in arthritic joints is associated with bone destruction during chronic inflammatory arthritis. Moreover, we want to determine to which extent the loss of Hem1 specifically in osteoclasts or in macrophages affects arthritis development in mice. For this pur-pose, we will induce arthritis in total, macrophage-specific and osteoclast-specific Hem1-/- mice by crossing them into hTNFtg mice, that develop a TNFalpha-dependent arthritis, or by K/BxN serum transfer and analyse the development and severity of disease (e.g. inflammation, synovial hyper-plasia, bone erosion) by morphometric, histological and immunohistochemical methods. Further-more, the putative inhibitory effect of Hem1 on osteoclast differentiation and/or osteoclast cell-fusion will be examined. This project will provide new insights into the mechanisms of inflammatory bone destruction and facilitate the development of novel treatment strategies for chronic inflammatory disorders, particularly RA.