Abstract：
Osteocytes engage in bone resorption and mineralization surrounding their expansive lacunar-canalicular system (LCS) through peri-LCS turnover. However, fundamental questions persist about where, when, and how often osteocytes engage in peri-LCS turnover and how these processes change with aging. Furthermore, whether peri-LCS turnover is associated with natural variation in cortical tissue strain remains unexplored. To address these questions, we utilized confocal scanning microscopy, immunohistochemistry, and scanning electron microscopy to characterize osteocyte peri-LCS turnover in the cortical (mid-diaphysis) and cancellous (metaphysis) regions of femurs from young adult (5 mo) and early-old-age (22 mo) female C57BL/6JN mice. LCS bone mineralization was measured by the presence of perilacunar fluorochrome labels. LCS bone resorption was measured by immunohistochemical marker of bone resorption. The dynamics of peri-LCS turnover were estimated from serial fluorochrome labeling, where each mouse was administered two labels between 2 and 16 days before euthanasia. Osteocyte participation in mineralizing their surroundings is highly abundant in both cortical and cancellous bone of young adult mice but significantly decreases with aging. LCS bone resorption also decreases with aging. Aging has a greater impact on peri-LCS turnover dynamics in cancellous bone than in cortical bone. Lacunae with recent peri-LCS turnover are larger in both age groups. While peri-LCS turnover is associated with variation in tissue strain between cortical quadrants and intracortical location for 22 mo mice, these associations were not seen for 5 mo mice. The impact of aging on decreasing peri-LCS turnover may have significant implications for bone quality and mechanosensation.
摘要：
骨细胞通过LCS周围的周转参与其扩张性腔隙-小管系统（LCS）周围的骨吸收和矿化。然而,关于哪里的基本问题仍然存在，when,以及骨细胞参与LCS周围更替的频率以及这些过程如何随着年龄的增长而变化。此外，周围LCS的周转是否取决于组织应变仍有待探索。为了解决这些问题,我们利用共聚焦扫描显微镜，免疫组织化学，和扫描电子显微镜来表征年轻成年（5个月）和早期老年（22个月）雌性C57BL/6JN小鼠的皮质（中骨干）和松质骨（干phy端）股骨的骨细胞周围LCS更新。通过周围荧光染料标记的存在来测量LCS骨矿化。通过骨吸收的免疫组织化学标记物测量LCS骨吸收。从系列荧光染料标记中估算了LCS周周转的动态，其中每只小鼠在安乐死前2到16天之间给予两个标签。在年轻成年小鼠的皮质骨和松质骨中，骨细胞参与矿化周围环境的活动非常丰富，但随着年龄的增长而显着降低。LCS骨吸收也随着老化而减少。与皮质骨相比，衰老对松质骨周围LCS周转动力学的影响更大。在两个年龄组中，近期LCS周围更替的空隙较大。我们的数据支持以下假设：LCS周围的更新与22mo小鼠的皮质和皮质内位置有关，而与5mo小鼠无关。衰老对降低LCS周围更替的影响可能对骨质量和机械感觉具有重要意义。
