Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan.
Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
Biomech Model Mechanobiol. 2019 Apr;18(2):375-385. doi: 10.1007/s10237-018-1088-6. Epub 2018 Nov 1.
In this study, based on the measurements of intracortical vascular canal structure, we investigated the disuse effect on local O supply in the cortical bones of growing rats. Hindlimb disuse was produced by unilateral sciatic neurectomy (SN) at 4 weeks age. The canal network structures within tibial cortical bone were evaluated in 8- and 12-week-old rats undergoing SN or no treatment (control) by synchrotron radiation micro-CT. Additionally, we developed an intracortical network model by combining the imaged-based canal network with a bone matrix containing theoretical lacunar-canalicular network, and determined the distribution of O concentration in bone tissue numerically. In the control bone, canal network was reduced with growth, resulting in decreased blood flow and averaged O concentration and increased spatial heterogeneity in tissue O concentration. Disuse reduced the canal network, leading to a lower flow rate, lower average O concentration and higher heterogeneity of O concentrations. However, the rarefaction of the canal network with growth was smaller under the disuse condition, and accordingly, the flow rate, the average O concentration and the heterogeneity of O concentrations remained stable. In particular, although the fraction of the canal volume was smaller, the densities of canal segments and bifurcation points under disuse condition tended to be higher than those of the control bone. The heterogeneity of O concentration was lower. Our results indicated that the disuse may lead to more uniformity in the canal network structure and thereby uniform O, possibly contributing to O supply efficiency.
在这项研究中，我们基于皮质骨内血管管腔结构的测量结果，研究了废用对生长大鼠皮质骨局部氧供应的影响。在 4 周龄时通过单侧坐骨神经切断术（SN）产生下肢废用。通过同步辐射微 CT 对接受 SN 或不接受治疗（对照）的 8 周和 12 周龄大鼠的胫骨皮质骨内管腔网络结构进行了评估。此外，我们通过将基于成像的管腔网络与包含理论腔隙-管腔网络的骨基质相结合，开发了一种皮质内网络模型，并通过数值方法确定了骨组织中氧浓度的分布。在对照骨中，随着生长，管腔网络减少，导致血流和平均氧浓度降低，组织氧浓度的空间异质性增加。废用减少了管腔网络，导致流速降低、平均氧浓度降低和氧浓度异质性增加。然而，在废用条件下，管腔网络的稀疏化程度较小，因此流速、平均氧浓度和氧浓度的异质性保持稳定。特别是，尽管管腔体积分数较小，但在废用条件下管腔段和分叉点的密度趋于高于对照骨，氧浓度的异质性较低。我们的结果表明，废用可能导致管腔网络结构更加均匀，从而提供更均匀的氧，可能有助于提高氧供应效率。
