Noninvasive optical monitoring of bone quality in an arthritic mouse model

说明（由申请人提供）：意义：糖皮质激素（GC）治疗是类风湿性关节炎常用的抗炎处方，有危险的副作用：它会增加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联合试验。这些混合物的功效经常在类风湿性关节炎转基因小鼠模型中进行研究，使用x射线成像和力学测试来评估骨质量。不幸的是，放射密度与早期骨脆性的相关性很弱，机械试验需要牺牲动物，不能转化为人类患者。需要新的方法来研究动物（和人类）随着时间的推移骨退化的进展，特别是在早期阶段发现变化，干预是最有价值的。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gc处理的活体小鼠的完整肢体来监测骨质量。在初步测试中，从这些小鼠身上切除的骨骼的拉曼光谱显示出比对照动物更低的矿物质与基质比率，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，小鼠骨骼的拉曼特征可以通过完整肢体的软组织收集到。这些结果激发了RS可以在多个时间点无创地监测单个小鼠，并在各种GC治疗方案下检测到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射线吸收仪）模式。具体目标：该项目的第一个具体目标是确定离体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密切相关。各组小鼠将配对研究三个变量：野生型与转基因，gc处理与安慰剂，单独gc与加药gc。第二个具体目标是通过优化探针几何形状和数据分析来减少来自上覆软组织的干扰，在活体动物中获得相同的拉曼信息。实现这一目标将能够在几周内对单个动物的骨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脆性发病史。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：拟议的工作直接解决了NIBIB的使命，即“开发早期疾病检测和健康状况评估技术”，以及NIAMS的使命，即“支持关节炎、肌肉骨骼和皮肤疾病的病因、治疗和预防研究”。

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.