Noninvasive optical monitoring of bone quality in an arthritic mouse model

说明(申请人提供)：意义：糖皮质激素(GC)治疗，一种治疗类风湿性关节炎的常见抗炎处方，有一个危险的副作用：它增加了骨质疏松和骨折的风险。为了减少这种影响，其他药物正在与GC联合进行测试。这些鸡尾酒的疗效通常在风湿性关节炎转基因小鼠模型中进行研究，使用X射线成像和机械测试来评估骨骼质量。不幸的是，放射学密度与早期骨脆性的相关性很弱，力学测试需要牺牲动物，不能转化为人类患者。需要新的方法来研究动物(和人类)随着时间的推移骨骼退化的进程，特别是在干预最有价值的早期阶段检测变化。创新：我们建议使用拉曼光谱(RS)，一种化学敏感的光学散射技术，通过活的GC治疗的小鼠的完整肢体来监测骨骼质量。在初步测试中，来自这类小鼠的摘除骨骼的拉曼光谱显示，与对照动物相比，矿物与基质的比率较低，并且该比率与骨骼强度的机械测试密切相关。单独的测试已经证实，可以通过完整肢体的软组织收集小鼠骨骼的拉曼信号。这些结果支持这样的假设，即RS可以在多个时间点对单个小鼠进行非侵入性监测，并在不同的GC治疗方案下检测早期的骨改变迹象。另一个好处是，不使用电离辐射，这与常见的MicroCT和DXA(双X射线吸收法)模式不同。具体目标：该项目的第一个具体目标是确定体外皮质骨的拉曼光谱特征，这些特征与骨质量的金标准分析最相关。两组小鼠将配对研究三个变量：野生型与转基因，GC治疗与安慰剂，以及GC单独与GC加药物。第二个具体目标是在活体动物身上通过皮肤获得相同的拉曼信息，使用优化的探头几何形状和数据分析来减少覆盖软组织的干扰。实现这一目标将使在几周内对单个动物的骨骼质量进行强有力的监测，以前所未有的细节产生单个小鼠的骨骼脆性始发史。这样的病史应该是关于GC治疗如何影响骨骼质量以及补充药物的预防能力的丰富信息来源，为疾病管理和治疗提供反馈。相关性：这项拟议的工作直接满足了NIBIB“开发疾病早期检测和健康状况评估技术”的使命，以及NIAMS“支持关节炎、肌肉骨骼和皮肤病的病因、治疗和预防的研究”的使命。 与公共健康相关：类风湿性关节炎患者经常被给予减轻炎症的药物。不幸的是，这些药物本身也有副作用，会增加骨折的风险。这项研究将开发一种非侵入性的光学方法来测量关节炎小鼠的骨脆性，因为它们同时接受抗炎药物和试图保持骨骼健康的补充药物。通过在活体动物模型中提供一种更好的跟踪骨骼脆性的方法，这项工作将对骨骼疾病是如何发展以及药物如何在动物和人类中更有效地治疗这些疾病产生新的理解。

DESCRIPTION (provided by applicant): Significance: Glucocorticoid (GC) treatment, a common anti-inflammatory prescription for rheumatoid arthritis, has a dangerous side effect: it elevates risk for osteoporosis and bone fracture. To reduce this effect, other drugs are being tested in combination with GC. The efficacy of these cocktails is often studied in a transgenic mouse model of rheumatoid arthritis, using X-ray imaging and mechanical tests to assess bone quality. Unfortunately, radiographic density correlates only weakly with early stages of bone fragility, and mechanical tests require sacrifice of the animal and cannot be translated to human patients. New methods are needed to study the progression of bone deterioration in animals (and humans) over time, particularly to detect alterations in the early stages where intervention is most valuable. Innovation: We propose the use of Raman spectroscopy (RS), a chemically-sensitive optical scattering technique, to monitor bone quality through the intact limbs of living, GC-treated mice. In preliminary tests, Raman spectra of excised bones from such mice exhibit lower mineral-to-matrix ratios than from control animals, and the ratio correlates strongly with mechanical tests of bone strength. Separate tests have verified that Raman signatures from mouse bones can be gathered through the soft tissue of intact limbs. These results motivate the hypothesis that RS can monitor individual mice noninvasively at multiple time points and detect early signs of bone alteration under various GC treatment regimens. As an added benefit, no ionization radiation is used, unlike the common microCT and DXA (dual X-ray absorptiometry) modalities. Specific aims: The project's first specific aim is to identify the Raman spectral features from ex vivo cortical bone that correlate most strongly with gold-standard assays of bone quality. Groups of mice will be paired to study three variables: wild-type vs. transgenic, GC-treated vs. placebo, and GC-alone vs. GC-plus- drug. The second specific aim is to obtain this same Raman information transcutaneously in living animals, using optimized probe geometry and data analysis to reduce interference from overlying soft tissue. Achieving this aim will enable robust monitoring of bone quality in individual animals over several weeks, producing histories of bone fragility onset in individual mice with unprecedented detail. Such histories should be rich sources of information about how GC treatment compromises bone quality and about the preventive capabilities of complementary drugs, providing feedback for disease management and treatment. Relevance: The proposed work directly addresses NIBIB's mission of "developing technologies for early disease detection and assessment of health status," as well as NIAMS's mission to "support research into the causes, treatment, and prevention of arthritis and musculoskeletal and skin diseases." PUBLIC HEALTH RELEVANCE: People with rheumatoid arthritis are often given medications to reduce the inflammation. Unfortunately, these medications themselves have side effects that elevate risk for bone fracture. This study will develop a noninvasive optical method of measuring bone fragility in arthritic mice as they receive both anti-inflammatory medication and complementary drugs that try to preserve bone health. By providing a better way of tracking bone fragility in living animal models, this work will generate new understanding of how bone disorders develop and how medicines can treat them more effectively in both animals and humans.