FT-IR Microscopy of Mineral Structure in Osteoporosis

描述（申请人提供）：全世界每年有超过7500万女性和男性受到骨质疏松症的影响，每年的费用超过500亿美元。为了确定骨质疏松骨的成分变化，我们开创了傅里叶变换红外光谱成像（FTIRI），用于以约7 μ m的空间分辨率测量骨活检，并将该技术沿着组织学、显微CT和力学来评估骨质疏松症的治疗。双磷酸盐（BP），迄今为止，是最有效的药物用于预防脆性骨折和打击骨丢失。这些药物在骨中的半衰期可能> 10年，因为它们能够与骨矿物质结合。最近，报道的与使用BP相关的不良事件引发了“药物假期”的概念。在这个“假期”期间，BP治疗在可变的使用期后停止，随后是任意的无BP期。关于这个"药物假期"是否或何时开始或持续多久，目前还没有明确的声明。此外，“药物假期”对“骨质”的影响尚不清楚。"骨质量"定义的因素包括成分、微结构和微裂纹的存在，这些因素与"骨量"一起沿着导致骨折风险。我们的研究表明，BP治疗在微米水平上降低了骨材料的异质性。这种损失会导致裂纹扩展，从而导致断裂。我们的基本假设是，通过FTIRI和micro-CT证实的异质性丧失有助于BP治疗患者的骨折风险。我们进一步假设，单独的“药物假期”不会改变骨质量，这是由成分或异质性的变化决定的。基于这些想法，以及PTH增加异质性的初步发现，我们建议使用BP后接PTH的治疗方法。关于这种治疗在微米或纳米水平上对骨组成的影响的信息很少，但这些信息对于研究人员设计临床试验和推荐治疗方法非常重要。我们将使用2个特定的目的来解决我们的假设。1）为了表征“BP假期”前后的骨成分，使用髂嵴活检，来自：a）不同时期的BP治疗后2年的患者。“假期”或PTH治疗。B）长期BP的患者，具有可变的"假期"期。c）长期BP患者，高周转和正常周转。d）在小鼠中进行平行研究，以确定BP在什么时间点达到其对组织异质性的峰值效应，以及异质性是否随时间变化。还将在髂嵴活检中测量微裂纹。2)检验骨异质性延伸至纳米水平以及微观和纳米异质性的改变影响骨力学性能的假设。我们将i）开发和应用纳米IR来确定健康、患病和治疗的骨细胞和松质动物骨中的矿物质和基质异质性。ii）通过分析人PTH处理的组织及其对照来证实我们的发现。iii）将组织异质性（来自FTIRI和纳米IR）与宏观和纳米水平的机械性能相关联。如果成功，这些研究将解决目前关于骨质疏松症治疗方案的争论。

DESCRIPTION (provided by applicant): Osteoporosis affects more than 75 million women and men yearly, world-wide, at annual costs > $50 billion. To define compositional changes in osteoporotic bone, we pioneered Fourier transform infrared spectroscopic imaging (FTIRI) for measurement of bone biopsies at a spatial resolution of ~7um and applied this technique along with histology, micro-CT and mechanics to evaluate therapies for osteoporosis. Bisphosphonates (BP), to date, are the most effective drugs used to prevent fragility fractures and combat bone loss. These drugs can have a half-life in bone >10 years due to their ability to bind to bone mineral. Recently, reported adverse events associated with the use of BPs triggered the notion of a "drug holiday". During this "holiday", BP treatment is ceased after variable periods of usage, followed by arbitrary BP-free periods. There is no definitive statement on if, or when this "drug holiday" should start or how long it should last. Moreover, the effect ofa "drug holiday" on "bone quality" is unknown. "Bone Quality" defines those factors including composition, micro-architecture and presence of microcracks, which along with "Bone Quantity" contribute to fracture risk. Our studies showed BP treatment decreased bone material heterogeneity at the micron-level. This loss can contribute to crack propagation and hence fracture. Our underlying hypothesis is that loss of heterogeneity, evidenced through FTIRI and micro-CT, contributes to fracture risk in BP-treated patients. We further hypothesize that "Drug Holidays" alone, do not alter bone quality as determined by changes in composition or heterogeneity. Based on these ideas, and the preliminary finding that PTH increases heterogeneity, we suggest a treatment approach using a BP followed by PTH. Little information exists on the effects of such treatments on bone composition at the micro- or nano-levels, yet this information is important to enable investigators to design clinical trials and recommend therapies. We will address our hypotheses using 2 specific aims.1) To characterize the composition of bone before and after a "BP holiday", using iliac crest biopsies from: a) Patients after variable periods of BP-treatment followed by a 2 yr. "holiday" or PTH-treatment. b) Patients on long-term BP with variable "holiday" periods. c) Patients on long-term BP with high and normal turnover. d) Parallel studies in mice to determine at what point in time BPs attain their peak effect on tissue heterogeneity and whether or not heterogeneity changes with time. Microcracks will also be measured in iliac crest biopsies. 2) To test the hypothesis that bone heterogeneity extends to the nano-level, and that alterations in both micro- and nano-heterogeneity impact bone mechanical properties. We will i) Develop and apply nano- IR to define mineral and matrix heterogeneity in healthy, diseased and treated osteonal and cancellous animal bones. ii) Confirm our findings by analysis of human PTH-treated tissues and their controls. iii) Correlate tissue heterogeneity (from FTIRI and nano-IR) with mechanical performance at the macro- and nano-levels. If successful, these studies will address current debates regarding treatment protocols for osteoporosis.