The enlargement of osteocyte lacunae via osteocytic osteolysis was previously detected in situations of increased calcium demand (e.g., lactation, vitamin D deficiency). However, it is unclear whether similar processes occur also in the growing infantile skeleton and how this is linked to the mineral distribution within the bone matrix. Human iliac crest biopsies of 30 subjects (0-6 months, n = 14; 2-8 years, n = 6 and 18-25 years, n = 10) were acquired. Bone microarchitecture was assessed by micro-CT, while cellular bone histomorphometry was performed on undecalcified histological sections. Quantitative backscattered electron imaging (qBEI) was conducted to determine the bone mineral density distribution (BMDD) as well as osteocyte lacunar size and density. We additionally evaluated cathepsin K positive osteocytes using immunohistochemistry. Infantile bone was characterized by various signs of ongoing bone development such as higher bone (re)modeling, lower cortical and trabecular thickness compared to young adults. Importantly, a significantly higher osteocyte lacunar density and increased lacunar area were detected. Large osteocyte lacunae were associated with a more heterogeneous bone mineral density distribution of the trabecular bone matrix due to the presence of hypermineralized cartilage remnants, whereas the mean mineralization (i.e., CaMean) was not different in infantile bone. Absence of cathepsin K expression in osteocyte lacunae indicated nonexistent osteocytic osteolysis. Taken together, we demonstrated that the overall mineralization distribution in infantile bone is not altered compared to young adults besides high trabecular mineralization heterogeneity. Our study also provides important reference values for bone microstructure, BMDD and osteocyte characteristics in infants, children and young adults. Infantile bone displays large osteocyte lacunae indicating a developmental phenomenon rather than osteocytic osteolysis. Larger osteocytes may have superior mechanosensory abilities to enable bone adaption during growth.

中文翻译：

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髂嵴婴儿骨中的大骨细胞腔隙与矿物质分布受损或骨细胞溶骨迹象无关

先前在钙需求增加的情况下（例如，哺乳期、维生素 D 缺乏）检测到通过骨细胞溶骨作用导致的骨细胞陷窝扩大。然而，目前尚不清楚类似的过程是否也发生在正在生长的婴儿骨骼中，以及这与骨基质内矿物质分布的关系。获得了 30 名受试者（0-6 个月，n = 14；2-8 岁，n = 6 和 18-25 岁，n = 10）的人体髂嵴活检。通过显微 CT 评估骨微结构，而在未脱钙的组织切片上进行细胞骨组织形态测量。进行定量背散射电子成像 (qBEI) 以确定骨矿物质密度分布 (BMDD) 以及骨细胞腔隙大小和密度。我们还使用免疫组织化学评估了组织蛋白酶 K 阳性骨细胞。与年轻人相比，婴儿骨骼的特征在于持续骨骼发育的各种迹象，例如更高的骨骼（重新）建模、更低的皮质和小梁厚度。重要的是，检测到显着更高的骨细胞腔隙密度和增加的腔隙面积。由于高矿化软骨残余物的存在，大的骨细胞腔隙与骨小梁基质的更不均匀的骨矿物质密度分布相关，而婴儿骨中的平均矿化（即 CaMean）没有不同。骨细胞腔隙中组织蛋白酶 K 表达的缺失表明不存在骨细胞溶骨症。综上所述，我们证明除了高小梁矿化异质性之外，与年轻人相比，婴儿骨骼的整体矿化分布没有改变。我们的研究还为婴儿、儿童和年轻人的骨微结构、BMDD 和骨细胞特征提供了重要的参考价值。婴儿骨显示大的骨细胞腔隙，表明发育现象而不是骨细胞溶骨。较大的骨细胞可能具有优越的机械感觉能力，使骨骼在生长过程中适应。