Restriction of nidogen containing bisphosphonates- related osteonecrosis (BRONJ) to the jaw bone - Immunohistochemistry and molecular biology assessment of the animal BRONJ- model in the the Wistar- rat

目前还没有公认的双膦酸盐相关性颌骨骨坏死（BRONJ）的病因。BRONJ的特点是口内骨外露，骨的骨质疏松改变，口内软组织和硬组织愈合受损和炎症。氨基二膦酸盐（BP）对组织的毒性或BP相关的局部炎症是过去提出的潜在机制。然而，这是不可能的，因为BRONJ的相同临床表现是在使用Denosumab（一种单克隆抗rank (L)抗体）治疗后出现的。颌骨独特的生物学特征体现在其与颅神经嵴细胞（CNC）发育生物学相关的起源，这意味着与CNC相关的信号转导在颌骨内骨重塑。Msx-1仅在cnc衍生的骨结构中表达，对cnc衍生的组织重塑至关重要。结果显示，bp改变的颌骨中Msx-1和Rank(L)在蛋白和mrna水平上受到抑制。此外，BP被证明可以诱导巨噬细胞向炎症相关的M1型极化。Rank(L)主要参与颌骨骨重塑和巨噬细胞分化的信号转导。因此，Msx-1/ Rank(L)信号的受损可以解释BP和Denosumab特异性颌骨骨坏死。本实验项目（模型wistar大鼠）将阐明BP治疗是否导致颌骨骨重塑和巨噬细胞分化的差异损害，并与颅外间充质测定的胫骨骨进行比较。本研究的目的是定量比较应用唑来膦酸后拔牙窝和胫骨骨折愈合过程中Msx-1、Msx-2、Bmp-2/4、Dlx-5、Runx-2、Rank(L)的表达模式。此外，需要澄清的是，如文献所述，BP是否优先与表达骨性神经嵴衍生结构的Connexin-43相互作用。该项目的结果将提供描述BRONJ正式病理的信息。此外，该项目的数据将阐明颌骨骨重构的位点特异性信号转导和可能的特异性骨免疫微环境。该研究结果可能有助于BP和Denosumab治疗颌骨特异性骨增生性和炎症性疾病，如小血管病、骨化纤维瘤和原发性慢性骨髓炎。

No accepted etiology of the Bisphosphonate related osteonecrosis of the jaw (BRONJ) is available at present. BRONJ is characterized by intraoral exposed bone, osteopetrotic changes of the bone, impaired intraoral hard- and soft tissue healing and inflammation. Aminobisphosphonate (BP)- related toxicity to tissues or BP-related local inflammation as underlying mechanisms have been proposed in the past. This is not likely, however, since the identical clinical picture of BRONJ is presented following therapy with Denosumab, a monoclonal anti-Rank(L) antibody. The unique biologic feature of jaw bone is represented by its developmental biology related origin from the cranial neural crest cells (CNC), which implies CNC-related signal transduction of osseous remodelling within jaw bones. Msx-1 is exclusively expressed in CNC-derived osseous structures and pivotal to CNC-derived tissue remodeling. Own results showed suppression of Msx-1 and Rank(L) in BP-altered jaw bone at protein- and mRNA-level. Furthermore BP were shown to induce polarization of macrophages towards the inflammation-related M1 type. Rank(L) is essentially involved in signal transduction of jaw bone osseous remodelling and macrophage differentiation. Thus, impaired Msx-1/ Rank(L)-signalling could explain BP- and Denosumab specific osteonecrosis of the jaw.This experimental project (model wistar rat) shall clarify if BP treatment leads to differential impairment of bone remodelling and macrophage differentiation in jaw bone compared with extracranial mesenchymal determined tibia bone. The aim of this study is to quantitatively compare the expression patterns of Msx-1, Msx-2, Bmp-2/4, Dlx-5, Runx-2, Rank(L) during healing of an extraction socket and a tibia fracture following application of zoledronic acid. Furthermore, it shall be clarified if BP preferentially interact with Connexin-43 expressing osseous neural crest derived structures as described in literature. The results of the project will provide information describing the formal pathology of BRONJ. Moreover, the data of the project will elucidate the site specific signal transduction of osseous remodelling in jaw bones and the possible specific osteoimmunologic microenvironment. The results of the study might help to enable the evidence based therapeutic use of BP and Denosumab treating jaw bone specific osteoproliferative and inflammatory diseases like cherubism, ossifying fibroma and primary chronic osteomyelitis.