Department of Mechanical Engineering, Polytechnique Montréal, P.O. Box 6079, Station Centre-Ville, Montréal, QC H3C 3A7, Canada; CHU Sainte-Justine Research Centre, 3175 Côte-Sainte-Catherine Road, Montréal, QC H3T 1C5, Canada.
CHU Sainte-Justine Research Centre, 3175 Côte-Sainte-Catherine Road, Montréal, QC H3T 1C5, Canada.
Bone. 2022 Jan;154:116207. doi: 10.1016/j.bone.2021.116207. Epub 2021 Sep 20.
Bone growth is an essential part of skeletal development during childhood and puberty. Accurately characterizing longitudinal bone growth helps to better understand the determining factors of peak bone mass, which has impacts on bone quality later in life. Animal models were largely used to study longitudinal bone growth. However, the commonly used histology-based method is destructive and unable to follow up the growth curve of live animals in longitudinal experiments. In this study, we validated an in vivo micro-CT-based method against the histology-based method to quantify longitudinal bone growth rates of young rats non-destructively. CD (Sprague Dawley) IGS rats aged 35, 49 and 63 days received the same treatments: two series of repeated in vivo micro-CT scans on their proximal hind limb at a five-day interval, and two calcein injections separated by three days. The longitudinal bone growth rate was quantified by registering time-lapse micro-CT images in 3D, calculating the growth distance on registered images, and dividing the distance by the five-day gap. The growth rate was also evaluated by measuring the 2D distance between consecutive calcein fluorescent bands on microscopic images, divided by the three-day gap. The two methods were both validated independently with reproducible repeated measurements, where the micro-CT-based method showed higher precision. They were also validated against each other with low relative errors and a strong Pearson sample correlation coefficient (0.998), showing a significant (p < 0.0001) linear correlation between paired results. We conclude that the micro-CT-based method can serve as an alternative to the histology-based method for the quantification of longitudinal growth. Thanks to its non-invasive nature and true 3D capability, the micro-CT-based method helps to accommodate in vivo longitudinal animal studies with highly reproducible measurements.
骨骼生长是儿童和青春期骨骼发育的重要组成部分。准确描述纵向骨生长有助于更好地了解峰值骨量的决定因素，这对以后的生活中的骨骼质量有影响。动物模型在很大程度上被用于研究纵向骨生长。然而，常用的基于组织学的方法是破坏性的，无法在纵向实验中跟踪活体动物的生长曲线。在这项研究中，我们通过活体 micro-CT 方法对年轻大鼠的纵向骨生长速率进行了非破坏性的定量，该方法与基于组织学的方法进行了验证。35、49 和 63 天大的 CD（Sprague Dawley）IGS 大鼠接受了相同的处理：在五天的间隔时间内在其近侧后肢上进行两次重复的活体 micro-CT 扫描，以及两次 calcein 注射，间隔三天。通过在 3D 中注册时移 micro-CT 图像来定量纵向骨生长率，计算注册图像上的生长距离，并用五天的间隔距离来除。通过测量在显微镜图像上连续 calcein 荧光带之间的 2D 距离，并除以三天的间隔，也可以评估生长率。两种方法都经过可重复的重复测量验证，其中基于 micro-CT 的方法显示出更高的精度。它们还通过低相对误差和强 Pearson 样本相关系数（0.998）相互验证，表明配对结果之间存在显著（p<0.0001）线性相关性。我们得出结论，基于 micro-CT 的方法可以替代基于组织学的方法来定量纵向生长。由于其非侵入性和真正的 3D 能力，基于 micro-CT 的方法有助于适应具有高度可重复性测量的活体纵向动物研究。
