David Valentin, Laroche Norbert, Boudignon Benjamin, Lafage-Proust Marie-Hélène, Alexandre Christian, Ruegsegger Peter, Vico Laurence
LBTO, INSERM E0366, University of Saint-Etienne, Saint-Etienne, France.
J Bone Miner Res. 2003 Sep;18(9):1622-31. doi: 10.1359/jbmr.2003.18.9.1622.
We tested a novel microcomputed tomograph designed to longitudinally and noninvasively monitor bone alterations in hindlimb-unloaded female rats at a resolution of 26 microm over a period of 3 weeks. This prototype has a potential to detect three-dimensional trabecular microarchitectural changes induced by growth and unloading.
Until now, data concerning structural changes of cancellous bone have only been available after necropsy of animals. In this study, we tested a novel microcomputed tomography (microCT) technique designed to monitor such changes repeatedly at a resolution of 26 microm with an acquisition time of about 10 minutes to map the entire proximal tibial metaphysis.
Four-month-old female Wistar rats were randomized to seven groups of 10 animals to be either tail-suspended or to act as controls. MicroCT and DXA measurements were performed at 0, 7, 14, and 23 days in suspended and control rats. One group was killed at each of these time points, and bone samples were processed for histomorphometry and ex vivo microCT.
We verified that a good correlation was obtained between two-dimensional bone parameters evaluated in longitudinal tibial sections either by histomorphometry or microCT and microCT parameters obtained from either in vivo or ex vivo tibias. The longitudinal survey allowed earlier detection of both growth and unloading-related bone changes than the transverse survey. In controls, aging induced denser bones, reorganization of the trabecular network toward a more oriented plate-like structure, and an isotropic pattern. Unloading first inhibited cortical and cancellous bone growth and then induced bone loss characterized by fewer trabeculae, reduced connectivity density, and enhanced structure model index (SMI), revealing a lighter cancellous structure with development of rod-like characteristics.
We show for the first time that this microCT prototype has a great potential to accurately, repeatedly, reliably, and rapidly investigate alterations of three-dimensional trabecular microarchitecture.
我们测试了一种新型微型计算机断层扫描仪，该仪器旨在以26微米的分辨率纵向、无创地监测后肢卸载雌性大鼠的骨骼变化，监测期为3周。该原型机有潜力检测由生长和卸载引起的三维小梁微结构变化。
到目前为止，有关松质骨结构变化的数据仅在动物尸检后才能获得。在本研究中，我们测试了一种新型微型计算机断层扫描（microCT）技术，该技术旨在以26微米的分辨率、约10分钟的采集时间重复监测此类变化，以绘制整个胫骨近端干骺端的图谱。
将4个月大的雌性Wistar大鼠随机分为7组，每组10只，分别进行尾部悬吊或作为对照。在悬吊和对照大鼠的第0、7、14和23天进行MicroCT和DXA测量。在这些时间点的每一个时间点处死一组大鼠，并对骨样本进行组织形态计量学和离体MicroCT处理。
我们证实，通过组织形态计量学或MicroCT在纵向胫骨切片中评估的二维骨参数与从体内或离体胫骨获得的MicroCT参数之间具有良好的相关性。纵向调查比横向调查能更早地检测到与生长和卸载相关的骨骼变化。在对照组中，衰老导致骨骼密度增加，小梁网络重组为更具方向性的板状结构，并呈现各向同性模式。卸载首先抑制皮质骨和松质骨生长，然后导致骨质流失，其特征是小梁减少、连接密度降低和结构模型指数（SMI）增加，显示出具有杆状特征的较轻松质结构。
我们首次表明，这种MicroCT原型机在准确、重复、可靠和快速研究三维小梁微结构变化方面具有巨大潜力。
