Noninvasive optical monitoring of bone quality in an arthritic mouse model

描述（由申请人提供）：意义：糖皮质激素（GC）治疗是类风湿性关节炎的常见抗炎处方，具有危险的副作用：它增加了骨质疏松症和骨折的风险。为了减少这种影响，正在测试其他药物与GC的组合。这些鸡尾酒的功效通常在类风湿性关节炎的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质量。不幸的是，放射学密度与骨脆性的早期阶段仅弱相关，并且机械测试需要牺牲动物并且不能转化为人类患者。需要新的方法来研究动物（和人类）随着时间的推移骨退化的进展，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），一种化学敏感的光散射技术，监测骨质量通过完整的四肢的生活，GC处理的小鼠。在初步测试中，这些小鼠的离体骨的拉曼光谱显示出比对照动物更低的矿物质-基质比率，并且该比率与骨强度的机械测试密切相关。单独的测试已经证实，老鼠骨骼的拉曼特征可以通过完整肢体的软组织收集。这些结果激发了RS可以在多个时间点非侵入性地监测个体小鼠并检测各种GC治疗方案下骨改变的早期迹象的假设。作为一个额外的好处，不使用电离辐射，不像常见的microCT和DXA（双X射线吸收测定法）模式。 具体目标：该项目的第一个具体目标是识别离体皮质骨的拉曼光谱特征，这些特征与骨质量的金标准测定最密切相关。将小鼠组配对以研究三个变量：野生型与转基因、GC处理的与安慰剂以及单独GC与GC加药物。第二个具体目标是在活体动物中获得相同的拉曼信息transmittance，使用优化的探针几何形状和数据分析来减少来自覆盖软组织的干扰。实现这一目标将能够在数周内对个体动物的骨质量进行强有力的监测，从而以前所未有的细节在个体小鼠中产生骨脆性发作的历史。这些病史应该是关于GC治疗如何损害骨质量和补充药物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：拟议的工作直接涉及NIBIB的使命“开发早期疾病检测和健康状况评估技术”，以及NIAMS的使命“支持对关节炎、肌肉骨骼和皮肤疾病的病因、治疗和预防的研究”。" 公共卫生相关性：类风湿性关节炎患者经常服用药物来减轻炎症。不幸的是，这些药物本身具有增加骨折风险的副作用。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，因为它们接受了抗炎药物和补充药物，试图保持骨骼健康。通过提供一种更好的方法来跟踪活体动物模型中的骨骼脆弱性，这项工作将对骨骼疾病如何发展以及药物如何在动物和人类中更有效地治疗它们产生新的理解。

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.