Does aging decrease osteocyte lacunar-canalicular bone quality?

项目摘要 骨折在衰老中是常见的，然而用于在衰老中保持骨质量的疗法是有限的。的 骨细胞参与骨质量的维持，可能是骨脆性的一个有希望的治疗靶点 在衰老。骨细胞位于骨内的骨陷窝中，骨陷窝由小管连接。骨细胞既可以 吸收和存款骨组织邻近巨大的腔隙-小管系统（LCS）。衰老减少 骨陷窝和骨小管的数量和大小也改变骨细胞行为的几个方面。 然而，这些腔隙和小管形态学的变化并没有揭示骨细胞的比例是如何变化的。 在衰老过程中参与骨吸收或沉积变化。同样，改变重塑的数量 骨陷窝和骨小管附近由于老化是未知的。因此， 了解衰老如何影响骨细胞介导的骨质量。这项研究的首要假设是 LCS重塑通过降低骨矿物质和基质成熟度来增加骨质量， 随着年龄的增长，参与LCS重塑的骨细胞减少。提出了一个目标 来研究这个假设股骨来自于成年（6个月）、中年（18个月）和 将研究老年（24个月）雌性和雄性C57 B1/6小鼠的腔隙-泪小管重塑特征。 将根据组织学评价参与骨矿物质和基质吸收的骨细胞分数 和免疫组织化学，而骨形成骨细胞的分数将通过测量 荧光标记阳性的腔隙。对于每个年龄段，矿物质和基质将被映射为骨形成 和非骨形成骨细胞陷窝使用俄歇电子能谱（AES）在亚微米分辨率。 互补的亚微米级分辨率原子力显微镜（AFM）地图相同的空隙将 确定骨细胞重塑对骨组织模量的影响。AES和AFM地图也将 为泪小管生成。骨细胞陷窝和小管形态将被测量， 股骨这个项目的完成将大大推进对骨细胞如何重塑骨骼的理解 在整个生命周期中。该项目还将回答骨细胞腔隙的变化是否与骨细胞的生长有关的问题， 老化中的小管几何形状与骨细胞附近的骨质量损失有关。的创新使用 俄歇电子能谱和互补的原子力显微镜将提供新的见解， 衰老如何改变骨质量在生理相关的决议附近的腔隙-小管 系统这种方法预计将有广泛的效用，评估疾病的影响，伤害， 治疗骨细胞介导的骨质量。这项研究的长期目标是调查是否 通过治疗干预可以改变骨细胞的行为，从而影响LCS重塑， 改善骨骼抗骨折性。

Project Summary Bone fracture is common in aging, yet therapies for maintaining bone quality in aging are limited. The osteocyte participates in bone quality maintenance and may be a promising therapeutic target for bone fragility in aging. Osteocytes reside within bone in lacunae that are connected by canaliculi. The osteocyte can both resorb and deposit bone tissue adjacent to the immense lacunar-canalicular system (LCS). Aging diminishes the number and size of lacunae and canaliculi and also changes several aspects of osteocyte behavior. However, these changes in lacunar and canalicular morphologies do not reveal how the fraction of osteocytes engaged in bone resorption or deposition change in aging. Likewise, changes to the amount of remodeled bone near lacunae and canaliculi due to aging are not known. Thus, there are critical gaps in the understanding of how aging impacts osteocyte-mediated bone quality. The overarching hypothesis of this work is that LCS remodeling increases bone quality by decreasing bone mineral and matrix maturity near osteocytes, and that with increased age, less osteocytes participate in LCS remodeling. One Aim is proposed to investigate this hypothesis. Femurs from skeletally-mature young adult (6 mo), middle-age (18 mo), and aged (24 mo) female and male C57Bl/6 mice will be studied for lacunar-canalicular remodeling characteristics. The fraction of osteocytes participating in bone mineral and matrix resorption will be evaluated from histology and immunohistochemistry, while the fraction of bone-forming osteocytes will be assessed by measuring lacunae positive for fluorochrome labels. For each age, mineral and matrix will be mapped for bone-forming and non-bone-forming osteocyte lacunae using Auger Electron Spectroscopy (AES) at submicron resolution. Complementary submicroscale-resolution Atomic Force Microscopy (AFM) maps of the same lacunae will identify the impact of osteocyte remodeling on bone tissue modulus. AES and AFM maps will also be generated for canaliculi. Osteocyte lacunar and canalicular morphologies will be measured for the same femurs. Completion of this project will significantly advance the understanding of how osteocytes remodel bone across the lifespan. The project will also answer the question of whether changes to osteocyte lacunar and canalicular geometries in aging is associated with loss of bone quality near the osteocyte. The innovative use of Auger Electron Spectroscopy and complementary Atomic Force Microscopy will provide new insights into how aging changes bone quality at physiologically-relevant resolution adjacent to the lacunar-canalicular system. This approach is expected to have broad utility for evaluating the impacts of disease, injury, and therapeutics on osteocyte-mediated bone quality. The long-term goal of this research is to investigate whether osteocyte behavior can be changed through therapeutic interventions to influence LCS remodeling and improve skeletal fracture resistance.