Hunter Randee L, Agnew Amanda M
Skeletal Biology Research Laboratory, School of Health and Rehabilitation Sciences, The Ohio State University, Columbus, OH, United States.
Division of Radiologic Sciences and Therapy, School of Health and Rehabilitation Sciences, The Ohio State University, Columbus, OH, United States.
Bone Rep. 2016 Sep 12;5:252-261. doi: 10.1016/j.bonr.2016.09.002. eCollection 2016 Dec.
Osteocytes and their lacunocanalicular network have been identified as the regulator of bone quality and function by exerting extensive influence over metabolic processes, mechanical adaptation, and mineral homeostasis. Recent research has shown that osteocyte apoptosis leads to a decrease in bone quality and increase in bone fragility mediated through its effects on remodeling. The purpose of this study is to investigate variation in cortical bone osteocyte lacunar density with respect to major factors including sex, age, and intracortical porosity to establish both regional and systemic trends. Samples from the midshaft femur, midshaft rib and distal one-third diaphysis of the radius were recovered from 30 modern cadaveric individuals (15 males and 15 females) ranging from 49 to 100 years old. Thick ground undecalcified histological (80 μm) cross-sections were made and imaged under bright field microscopy. Osteocyte lacunar density (Ot.Lc.N/B.Ar) and intracortical porosity (%Po.Ar) were quantified. No significant sex differences in Ot.Lc.N/B.Ar or %Po.Ar were found in any element. Linear regressions demonstrated a significant decrease in osteocyte lacunar density (Ot.Lc.N/B.Ar) and increase in intracortical porosity (%Po.Ar) with age for the sex-pooled sample in the femur (R = 0.208, 0.297 respectively) and radius (R = 0.108, 0.545 respectively). Age was unable to significantly predict osteocyte lacunar density or intracortical porosity in the rib (R = 0.058, 0.114 respectively). Comparisons of regression coefficients demonstrated a systemic trend in the decrease in osteocyte lacunar density (Ot.Lc.N/B.Ar) and increase in intracortical porosity (%Po.Ar) with age. In each element, intracortical porosity was significantly negatively correlated with lacunar density for which the radius demonstrated the strongest relationship (r = - 0.746). Using pore number (Po.N) as a proxy for available vascularity to support the osteocyte population, Po.N was able to predict 61.8% of variation in osteocyte lacunar number (Ot.Lc.N) in the rib. The femur and radius also demonstrated significant relationships between these variables (R = 0.560 and 0.397 respectively). The results from this study indicate that although the femur, radius and rib may be experiencing systemically influenced declines in osteocyte lacunar density, there may be differential effects at each anatomical site potentially due to age related changes in mechanical loading. With decreasing osteocyte lacunar density in each element, intracortical porosity increased with likely direct impacts on gross bone strength. This study provides a foundation upon which to build interpretations of osteocyte lacunar density values and their effect on differential fracture risk for aging individuals.
骨细胞及其骨陷窝-小管网络已被确认为骨质量和功能的调节因子，因为它们对代谢过程、机械适应和矿物质稳态具有广泛影响。最近的研究表明，骨细胞凋亡会导致骨质量下降和骨脆性增加，这是通过其对重塑的影响介导的。本研究的目的是调查皮质骨骨细胞陷窝密度相对于性别、年龄和皮质内孔隙率等主要因素的变化，以确定区域和全身趋势。从30名年龄在49至100岁的现代尸体个体（15名男性和15名女性）中获取股骨中段、肋骨中段和桡骨骨干远端三分之一处的样本。制作了厚80μm的未脱钙组织学切片，并在明场显微镜下成像。对骨细胞陷窝密度（Ot.Lc.N/B.Ar）和皮质内孔隙率（%Po.Ar）进行了量化。在任何一个部位均未发现Ot.Lc.N/B.Ar或%Po.Ar存在显著性别差异。线性回归表明，在股骨（R分别为0.208和0.297）和桡骨（R分别为0.108和0.545）中，合并性别样本的骨细胞陷窝密度（Ot.Lc.N/B.Ar）随年龄显著降低，皮质内孔隙率（%Po.Ar）随年龄显著增加。年龄无法显著预测肋骨中的骨细胞陷窝密度或皮质内孔隙率（R分别为0.058和0.114）。回归系数比较表明，骨细胞陷窝密度（Ot.Lc.N/B.Ar）随年龄降低和皮质内孔隙率（%Po.Ar）随年龄增加存在全身趋势。在每个部位，皮质内孔隙率与陷窝密度显著负相关，其中桡骨的相关性最强（r = -0.746）。使用孔隙数量（Po.N）作为支持骨细胞群体的可用血管的指标，Po.N能够预测肋骨中骨细胞陷窝数量（Ot.Lc.N）变化的61.8%。股骨和桡骨在这些变量之间也显示出显著关系（R分别为0.560和0.397）。本研究结果表明，尽管股骨、桡骨和肋骨可能在全身受到影响，骨细胞陷窝密度下降，但由于机械负荷的年龄相关变化，每个解剖部位可能存在不同影响。随着每个部位骨细胞陷窝密度降低，皮质内孔隙率增加，这可能对骨的整体强度产生直接影响。本研究为解释骨细胞陷窝密度值及其对老年人骨折风险差异的影响奠定了基础。
