Does aging decrease osteocyte lacunar-canalicular bone quality?

项目摘要 骨折在衰老中很常见，但在衰老过程中保持骨骼质量的治疗方法有限。这个 骨细胞参与维持骨质量，有望成为治疗骨脆性疾病的靶点 在衰老过程中。骨细胞位于骨陷窝内，骨陷窝之间由小管连接。骨细胞既可以 吸收和沉积巨大陷窝-小管系统(LCS)附近的骨组织。衰老会减退 骨陷窝和骨小管的数量和大小也改变了骨细胞行为的几个方面。 然而，这些骨陷窝和骨管形态的变化并不能揭示骨细胞的比例 在衰老过程中从事骨吸收或沉积的变化。同样，对改建的 因年龄增长而导致的骨陷窝和小管附近的骨质尚不清楚。因此，在以下方面存在严重差距 了解衰老如何影响骨细胞介导的骨质量。这部作品的主要假设是 LCS重塑是通过降低骨矿物质和基质成熟度来提高骨质量的 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 来研究这一假说。骨骼成熟的青年(6个月)、中年(18个月)和 老年(24mo)雌性和雄性C57BL/6小鼠将研究腔隙-小管重构的特征。 骨细胞参与骨矿物质和基质吸收的比例将从组织学的角度进行评估。 和免疫组织化学，而骨形成骨细胞的比例将通过测量 荧光标记为阳性的腔隙。对于每个年龄，矿物质和基质将被绘制成骨形成的地图 和非骨形成骨细胞陷窝在亚微米分辨率下使用俄歇电子能谱(AES)。 相同腔隙的互补亚微米级分辨率原子力显微镜(AFM)图 确定骨细胞重塑对骨组织模数的影响。AES和AFM地图也将 为小管生成的。将对骨细胞陷窝和骨管形态进行同样的测量 大腿骨。该项目的完成将极大地促进对骨细胞如何重塑骨骼的理解 在整个生命周期内。该项目还将回答这样一个问题，即骨细胞的变化是否存在缺陷和 随着年龄的增长，骨小管的几何形状与骨细胞附近骨质量的丧失有关。创新使用 俄歇电子能谱和互补原子力显微镜将提供新的见解 增龄如何改变腔隙管旁生理分辨率下的骨质量 系统。这种方法有望在评估疾病、伤害和疾病的影响方面具有广泛的实用性 骨细胞介导的骨质量的治疗。这项研究的长期目标是调查 通过治疗干预可以改变骨细胞的行为，以影响LCS重塑和 提高骨骼抗折性。

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.