Effect of MIP-1 delta on Osteoclast Development and Pathological Bone Resorption

描述（由申请人提供）：骨重塑是一种持续发生的骨破坏与骨形成的平衡，通过用新骨替代受损骨来维持骨强度。不幸的是，影响骨骼的疾病，如骨质疏松症、风湿性关节炎和癌症，使骨破坏和骨形成的微妙平衡倾向于前者，导致过度的骨质流失。在许多情况下，这种骨质流失会导致严重的疾病，包括严重的疼痛、关节破坏和病理性骨折。尽管我们对骨重塑过程的理解有所进步，但骨质疏松症、类风湿关节炎和癌症等骨骼疾病引发的病理性骨质流失的机制仍然知之甚少。提高对这些机制的理解对于开发更有效的治疗方法至关重要。最近的证据表明，化学信使的趋化因子家族的成员可能在介导病理性骨质流失中发挥作用。趋化因子巨噬细胞炎症蛋白(MIP)-3a，其在类风湿关节炎和牙周炎中的表达已被报道，已被证明可以促进称为破骨细胞（OCL）的骨破坏细胞的发育。有趣的是，我们最近发现MIP家族成员MIP-1d的水平在肾细胞癌骨转移（RBM）中显著升高，这经常导致过度的骨破坏。有趣的是，在类风湿性关节炎患者的滑膜组织中也检测到MIP-1d。随后的体外初步研究表明，MIP-1d不仅刺激未成熟OCL的募集，还能促进向成熟OCL的分化。基于这些初步数据，我们假设MIP-1d通过与RANKL联合增强OCL形成关键信号通路的刺激，直接介导病理性骨质流失。在初步研究中，我们发现RANKL和MIP-1d都能够刺激NF-？B和PLC？2信号通路是OCL形成的两个关键途径，而其他OCL形成的重要途径不受MIP-1d的影响。我们将通过确定MIP-1d增强NF-？B和PLC？2与RANKL联合激活。随后，我们将利用NF-？B和PLC？2 .研究各途径在体外mip -1d增强OCL形成中的功能作用。最后，使用MIP-1d产量增加或沉默的人类RBM细胞系，我们将使用RBM诱导的骨质流失小鼠模型来研究MIP-1d对体内骨破坏的影响。此外，我们将确定MIP-1d在原发性RCC中的表达与随后发生溶骨转移的临床相关性。这些研究将进一步加深我们对趋化因子在病理性骨质流失中的作用的认识，并可能为预防和治疗提供新的靶点，从而有可能极大地影响骨科医学的未来。公共卫生相关性：这项工作可能会确定MIP-1d作为预防和治疗病理性骨质流失的治疗靶点，为MIP-1d的作用如何被消除提供见解，并确定MIP-1d作为溶骨性转移发展和抗RANKL治疗反应的预后指标的潜在效用，目前正在进行3期研究，评估其对导致骨质流失的患者的影响(例如：骨质疏松、类风湿关节炎、骨转移等)。因此，这项工作是及时的，有可能影响临床预防和治疗决策，为未来的临床前和临床研究提供必要的框架，并将极大地推进我们目前对类风湿性关节炎和癌症等疾病病理性骨质流失发展的生物学机制的理解，这些疾病每年影响数百万人。如果能够在发病之前或发病早期采取更有效的药物治疗，就可以预防或延缓严重骨破坏的发展，从而提高这些经常需要手术治疗的患者的生活质量，降低护理费用，从而极大地影响公众健康。

DESCRIPTION (provided by applicant): Bone remodeling is a continuously occurring balance of bone destruction followed by bone formation, which maintains bone strength by replacing damaged bone with new bone. Unfortunately, diseases affecting the skeleton such as osteoporosis, rheumatoid arthritis, and cancer, tilt the delicate balance of bone destruction and bone formation toward the prior, leading to excessive bone loss. In many cases, this bone loss causes significant morbidity including severe pain, joint destruction, and pathological fracture. Despite advances in our comprehension of the bone remodeling process, the mechanisms responsible for pathological bone loss initiated by skeletal diseases such as osteoporosis, rheumatoid arthritis, and cancer remain poorly understood. Improved understanding of these mechanisms is vital to the development of more effective therapeutics. Recent evidence suggests that members of the chemokine family of chemical messengers may play a role in mediating pathological bone loss. The chemokine macrophage inflammatory protein (MIP)-3a, whose expression has been reported in both rheumatoid arthritis and periodontitis, has been shown to enhance the development of bone-destroying cells called osteoclasts (OCL). Interestingly, we recently found levels of the MIP family member MIP-1d to be significantly elevated in renal cell carcinoma bone metastasis (RBM), which frequently causes excessive bone destruction. Interestingly, MIP-1d has also been detected in synovial tissue from rheumatoid arthritis patients. Subsequent preliminary studies in vitro demonstrated that MIP-1d not only stimulates recruitment of immature OCL, but also enhances differentiation into mature OCL. Based on these preliminary data, we hypothesize that MIP-1d plays a direct role in mediating pathological bone loss by enhancing stimulation of key signaling pathways of OCL formation in combination with RANKL. In preliminary studies we found that both RANKL and MIP-1d were capable of stimulating NF-?B and PLC?2 signaling, two critical pathways for OCL formation, while other important pathways in OCL formation were unaffected by MIP-1d. We will initially investigate our hypothesis by determining the ability of MIP-1d to enhance NF-?B and PLC?2 activation in combination with RANKL. Subsequently, we will utilize chemical inhibitors of NF-?B and PLC?2 to examine the functional role of each pathway in MIP-1d-enhanced OCL formation in vitro. Lastly, using human RBM cell lines in which MIP-1d production has been increased or silenced, we will examine the effect of MIP-1d on bone destruction in vivo using a mouse model of RBM- induced bone loss. In addition, we will determine the clinical correlation between MIP-1d expression in primary RCC and the subsequent development of osteolytic metastasis. These studies will further our knowledge regarding the role of chemokines in pathological bone loss and may provide a novel target for prevention and therapy, thus having the potential to greatly impact the future of Orthopaedic medicine. PUBLIC HEALTH RELEVANCE: This work may identify MIP-1d as a therapeutic target for the prevention and treatment of pathological bone loss, provide insight into how the effects of MIP-1d may be abrogated, and determine the potential utility of MIP-1d as a prognostic indicator for both the development of osteolytic metastasis and the therapeutic response to anti- RANKL therapy, which is currently in phase 3 studies evaluating its effects in patients with conditions resulting in bone loss (eg. osteoporosis, rheumatoid arthritis, bone metastasis, etc.). Therefore, this work is timely and has the potential to influence both clinical prevention and treatment decisions, providing the framework necessary for future pre-clinical and clinical studies, and will greatly advance our current understanding of the biological mechanisms involved in the development of pathological bone loss in diseases such as rheumatoid arthritis and cancer, which affect millions of people each year. If more effective medical therapy can be instituted prior to or early in the course of disease, the development of severe bone destruction may be prevented or delayed, resulting in improved quality of life and decreased costs of care for these patients who often require surgical treatment, thus greatly impacting public health.