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

描述（由申请人提供）：骨重塑是骨破坏和骨形成之间持续发生的平衡，其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、类风湿性关节炎和癌症，使骨质破坏和骨质形成的微妙平衡向先前倾斜，导致骨质流失过多。在许多情况下，这种骨质流失会导致严重的发病率，包括剧烈疼痛、关节破坏和病理性骨折。尽管我们对骨重塑过程的理解取得了进展，但对骨质疏松症、类风湿性关节炎和癌症等骨骼疾病引发的病理性骨丢失的机制仍然知之甚少。加深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。据报道，趋化因子巨噬细胞炎症蛋白 (MIP)-3a 在类风湿性关节炎和牙周炎中都有表达，已被证明可以增强称为破骨细胞 (OCL) 的骨质破坏细胞的发育。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) 中显着升高，这经常导致过度的骨破坏。有趣的是，在类风湿关节炎患者的滑膜组织中也检测到了 MIP-1d。随后的体外初步研究表明，MIP-1d不仅可以刺激未成熟OCL的募集，还可以增强向成熟OCL的分化。基于这些初步数据，我们假设 MIP-1d 与 RANKL 结合增强对 OCL 形成关键信号通路的刺激，从而在介导病理性骨丢失中发挥直接作用。 在初步研究中，我们发现 RANKL 和 MIP-1d 都能够刺激 NF-κB 和 PLC?2 信号传导，这是 OCL 形成的两个关键途径，而 OCL 形成中的其他重要途径不受 MIP-1d 影响。我们将首先通过确定 MIP-1d 与 RANKL 结合增强 NF-κB 和 PLC?2 激活的能力来研究我们的假设。随后，我们将利用 NF-κB 和 PLC?2 的化学抑制剂来检查每个途径在 MIP-1d 增强的体外 OCL 形成中的功能作用。最后，我们将使用 MIP-1d 产生增加或沉默的人 RBM 细胞系，使用 RBM 诱导的骨质流失小鼠模型来检查 MIP-1d 对体内骨质破坏的影响。此外，我们将确定原发性肾细胞癌中 MIP-1d 表达与随后发生的溶骨性转移之间的临床相关性。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。 公共健康相关性：这项工作可能会将 MIP-1d 确定为预防和治疗病理性骨质流失的治疗靶点，深入了解如何消除 MIP-1d 的影响，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用途，该疗法目前正在进行 3 期研究，评估其对患有导致骨质流失的疾病（例如骨质流失）患者的影响。骨质疏松症、类风湿性关节炎、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，并将极大地促进我们目前对类风湿性关节炎和癌症等每年影响数百万人的疾病中病理性骨质流失发展的生物学机制的理解。如果可以在病程之前或病程早期采取更有效的药物治疗，则可以预防或延缓严重骨质破坏的发生，从而提高这些经常需要手术治疗的患者的生活质量并降低护理成本，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.