Pathophysiology of Biphosphonate-Induced ONJ in a Novel Animal Model

描述（由申请人提供）：近年来，颌骨骨坏死（ONJ）已被确定为双膦酸盐（BP）治疗的潜在并发症。这种骨骼疾病的特征是暴露在口腔内的坏死骨的积累持续超过6至8周。ONJ最常见于用有效的氮（N-） bp唑来膦酸盐（ZOL）或帕米膦酸盐治疗抑制骨转移的癌症患者，但也有报道称，在阿仑膦酸盐（ALN）治疗的骨质疏松患者中，ONJ的发生率要低得多。虽然多个病例报告研究表明ONJ的发生率和严重程度与n - bp抑制破骨细胞骨吸收的效力和这些药物的累积剂量有关，但尚未建立基于机制的因果关系。因此，开发动物模型来研究ONJ的病理生理将是提高我们对这种骨骼疾病认识的基本工具。我们的长期目标是阐明ONJ的病因和病理生理学，以便为新的有效预防和治疗策略奠定基础。本研究的目的是建立ONJ的动物模型，并确定不同效力的n - bp对坏死骨的去除和骨愈合的影响。我们的中心假设是ONJ是一个两阶段的过程：1)危险因素在口腔中启动导致硬组织坏死的过程；2) n - bp已被证实能抑制破骨细胞的吸收，阻碍坏死骨的清除，导致坏死骨在颌骨的积累，其本身就延迟了骨愈合的开始和后续进展。我们计划通过使用患有牙周炎的大鼠（Oryzomys palustris）来验证我们的中心假设，并确定ZOL和ALN对以下方面的影响：1)通过对牙周病进行离体评估，包括牙槽骨的放射评估，软组织受累和牙齿活动的评估，以及对牙周组织进行组织计量学分析来评估牙周损伤的进展；2)利用组织化学/组织学技术评估坏死骨的蓄积，并利用定量组织形态学测量骨吸收指标来去除坏死骨；3)利用定量组织形态学和免疫组化技术观察牙周组织新生骨形成和血管生成，作为骨愈合的指标；4)利用实时PCR技术检测骨吸收、骨形成和血管生成相关基因的表达。我们假设n - bp众所周知的和理想的抗吸收作用在ONJ的发展中起着核心作用。因此，在这个项目完成后，我们期望提供直接的证据，证明强效的BP ZOL会导致颌骨坏死骨的更多积累，与弱效的BP ALN相比，随后会导致骨愈合受损。我们也期望开发一种ONJ的动物模型，这将促进我们对这种骨骼疾病的认识和理解的进一步发展。项目描述：颌骨骨坏死（ONJ）是双膦酸盐（BP）治疗的潜在不良副作用。多个病例报告研究表明，ONJ的发生率和严重程度与BP的效力和药物的累积剂量有关。然而，由于缺乏适当的ONJ动物模型，人们对这种骨骼疾病知之甚少。本研究将为牙周炎动物模型沼泽稻大鼠ONJ样病变的组织机制提供深入的见解，并将在细胞和分子水平上阐明BP唑来膦酸钠诱导ONJ样病变的发生率高于BP阿仑膦酸钠的基础。

DESCRIPTION (provided by applicant): In recent years, osteonecrosis of the jaw (ONJ) has been identified as a potential complication of bisphosphonate (BP) treatment. This bone disorder is characterized by the accumulation of necrotic bone with exposure in the oral cavity that persists for more than 6 to 8 weeks. ONJ is observed most frequently in cancer patients treated with the potent nitrogen (N-)BPs zoledronate (ZOL) or pamidronate for inhibition of bone metastases, but it has also been reported to a much lesser extent in alendronate (ALN)-treated osteoporotic patients. While multiple case report studies suggest that the incidence and severity of ONJ are associated with the potency of N-BPs to inhibit osteoclastic bone resorption and cumulative dose of these drugs, no mechanism-based cause and effect relationship has yet been established. Therefore, the development of animal models to study the pathophysiology of ONJ will be a fundamental tool to enhance our understanding of this bone disorder. Our long-term goal is to elucidate the causes and pathophysiology of ONJ in order to create the basis for new effective strategies for prevention and treatment. The objectives of this proposal are to develop an animal model for ONJ, and to establish the effects of N-BPs of different potencies on the removal of necrotic bone and bone healing. Our central hypothesis is that ONJ is a two-stage process: 1) risk factors initiate processes in the oral cavity that cause necrosis of hard tissues; and 2) N-BPs, well-proven to inhibit osteoclastic resorption, block the removal of necrotic bone, causing an accumulation of necrotic bone in the jaw that in and of itself delays the initiation and subsequent progress of bone healing. We plan to test our central hypothesis by utilizing rice rats (Oryzomys palustris) with established periodontitis and determine the effects of ZOL and ALN on: 1) the progression of the periodontal damage by performing an ex-vivo evaluation of the periodontal disease, including a radiographic assessment of the alveolar bone, the evaluation of soft tissue involvement and tooth mobility, and by conducting a histometric analysis of the periodontal tissue; 2) the removal of necrotic bone by the assessment of necrotic bone accumulation using histochemical/histological techniques, and also on indices of bone resorption by using quantitative histomorphometry; 3) new bone formation and angiogenesis, as indices of bone healing, in the periodontium by using quantitative histomorphometry and immunohistochemical techniques; and 4) the expression of genes associated with bone resorption, bone formation, and angiogenesis using real time PCR techniques. We postulate that the well- known and desirable anti-resorptive effect of N-BPs has a central role in the development of ONJ. Consequently, at the completion of this project, it is our expectation to provide direct evidence that the potent BP ZOL will induce a higher accumulation of necrotic bone in the jaw, with subsequent impairment of bone healing as compared to that induced by the less potent BP ALN. It is also our expectation to develop an animal model for ONJ that will facilitate further advances in our knowledge and understanding of this bone disorder. Project Narrative: Osteonecrosis of the jaw (ONJ) is a potential adverse side effect of bisphosphonate (BP) treatment. Multiple case report studies suggest that the incidence and severity of ONJ are associated with the potency of BP and cumulative dose of the drug. However, this bone disorder is poorly understood, due in part to lack of appropriate animal models for ONJ. The proposed research will provide insight into a tissue-level mechanism for the development of ONJ-like lesions in marsh rice rats, an animal model for periodontitis, and will elucidate the basis, at the cellular and molecular levels, for the higher incidence of the BP zoledronate to induce ONJ- like lesions as compared with the BP alendronate.