Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476, Potsdam, Germany.
Department of Operative and Preventive Dentistry, Charité-Universitätsmedizin - Berlin, Berlin, Germany.
Calcif Tissue Int. 2024 Nov;115(5):744-758. doi: 10.1007/s00223-024-01289-y. Epub 2024 Oct 16.
The lacunocanalicular network (LCN) is an intricate arrangement of cavities (lacunae) and channels (canaliculi), which permeates the mineralized bone matrix. In its porosity, the LCN accommodates the cell network of osteocytes. These two nested networks are attributed a variety of essential functions including transport, signaling, and mechanosensitivity due to load-induced fluid flow through the LCN. For a more quantitative assessment of the networks' function, the three-dimensional architecture has to be known. For this reason, we aimed (i) to quantitatively characterize spatial heterogeneities of the LCN in whole mouse tibial cross-sections of BALB/c mice and (ii) to analyze differences in LCN architecture by comparison with another commonly used inbred mouse strain, the C57BL/6 mouse. Both tibiae of five BALB/c mice (female, 26-week-old) were stained using rhodamine 6G and whole tibiae cross-sections were imaged using confocal laser scanning microscopy. Using image analysis, the LCN was quantified in terms of density and connectivity and lacunar parameters, such as lacunar degree, volume, and shape. In the same tibial cross-sections, the calcium content was measured using quantitative backscattered electron imaging (qBEI). A structural analysis of the LCN properties showed that spatially denser parts of the LCN are mainly due to a higher density of branching points in the network. While a high intra-individual variability of network density was detected within the cortex, the inter-individual variability between different mice was low. In comparison to C57BL/6J mice, BALB/c mice showed a distinct lower canalicular density. This reduced network was already detectable on a local network level with fewer canaliculi emanating from lacunae. Spatial correlation with qBEI images demonstrated that bone modeling resulted in disruptions in the network architecture. The spatial heterogeneity and differences in density of the LCN likely affects the fluid flow within the network and therefore bone's mechanoresponse to loading.
板层管网（LCN）是由腔隙（陷窝）和通道（小管）组成的复杂网络，贯穿矿化骨基质。在其孔隙中，LCN 容纳了骨细胞的细胞网络。由于 LCN 内的流体流动引起的负载诱导，这两个嵌套网络具有多种基本功能，包括运输、信号传递和机械敏感性。为了更定量地评估网络的功能，必须了解其三维结构。出于这个原因，我们的目的是：（i）定量描述 BALB/c 小鼠整个胫骨横截面中 LCN 的空间异质性；（ii）通过与另一种常用近交系小鼠，C57BL/6 小鼠进行比较，分析 LCN 结构的差异。对五只 BALB/c 小鼠（雌性，26 周龄）的两只胫骨进行罗丹明 6G 染色，并使用共聚焦激光扫描显微镜对整个胫骨横截面进行成像。使用图像分析，以密度和连通性以及陷窝参数（如陷窝程度、体积和形状）来量化 LCN。在相同的胫骨横截面上，使用定量背散射电子成像（qBEI）测量钙含量。LCN 结构的分析表明，LCN 中空间更密集的部分主要是由于网络中的分支点密度更高。虽然在皮质内检测到网络密度的个体内变异性很大，但不同小鼠之间的个体间变异性较低。与 C57BL/6J 小鼠相比，BALB/c 小鼠的小管密度明显较低。这种减少的网络已经可以在局部网络水平上检测到，从陷窝中发出的小管较少。与 qBEI 图像的空间相关性表明，骨建模导致网络结构的中断。LCN 的空间异质性和密度差异可能会影响网络内的流体流动，从而影响骨对加载的机械反应。
