Martin E A, Ritman E L, Turner R T
Mayo Graduate School, Mayo Clinic, Rochester, MN 55905, USA.
Bone. 2003 Mar;32(3):261-7. doi: 10.1016/s8756-3282(02)00983-3.
Although the rat is the most common animal model used in studying osteoporosis, it is often used inappropriately. Osteoporosis is a disease that most commonly occurs in humans long after growth plate fusion with the associated cessation of longitudinal bone growth, but there has been a question as to when or to what extent the rat growth plate fuses. To investigate this question, we used microcomputed X-ray tomography, at voxel resolutions ranging from (5.7 micro m)(3) to (11 micro m)(3), to image the proximal epiphyseal growth plates of both male (n = 19) and female (n = 15) rat tibiae, ranging in age from 2 to 25 months. The three-dimensional images were used to evaluate fusion of the epiphyseal growth plate by quantitating the amount of cancellous bone that has bridged across the growth plate. The results suggest that the time course of fusion of the epiphyseal growth plate follows a sigmoidal pattern, with 10% of the maximum number of bridges having formed by 3.9 months in the male tibiae and 5.8 months in the female tibiae, 50% of the maximum number of bridges having formed by 5.6 months in the male tibiae and 5.9 months in the female tibiae, and 90% of the total maximum of bridges have formed by 7.4 months for the males and 6.5 months for the females. The total volume of bridges per tibia at the age at which the maximum number of bridges per tibia has first formed is 0.99 mm(3)/tibia for the males and 0.40 mm(3)/tibia for the females. After the maximum number of bridges (-290 for females, -360 for males) have formed the total volume of bridges per tibia continues to increase for an additional 7.0 months in the males and 17.0 months for the females until they reach maximum values (-1.5 mm(3)/tibia for the males and -2.2 mm(3)/tibia for the females).
尽管大鼠是研究骨质疏松症时最常用的动物模型，但它的使用常常并不恰当。骨质疏松症是一种最常见于人类生长板融合且纵向骨生长停止很久之后的疾病，但大鼠生长板何时融合或融合到何种程度一直存在疑问。为了研究这个问题，我们使用了微计算机断层扫描技术，体素分辨率范围从(5.7微米)³到(11微米)³，对年龄在2至25个月的雄性(n = 19)和雌性(n = 15)大鼠胫骨的近端骨骺生长板进行成像。通过量化跨越生长板的松质骨量，利用三维图像评估骨骺生长板的融合情况。结果表明，骨骺生长板的融合时间进程呈S形模式，雄性胫骨在3.9个月时形成的桥接数量达到最大值的10%，雌性胫骨在5.8个月时达到；雄性胫骨在5.6个月时形成的桥接数量达到最大值的50%，雌性胫骨在5.9个月时达到；雄性在7.4个月时、雌性在6.5个月时形成的桥接数量达到总量最大值的90%。雄性胫骨首次形成每根胫骨桥接数量最大值时的每根胫骨桥接总体积为0.99立方毫米/胫骨，雌性为0.40立方毫米/胫骨。在形成最大桥接数量后（雌性约为290个，雄性约为360个），雄性胫骨每根胫骨桥接的总体积在接下来的7.0个月内持续增加，雌性则在17.0个月内持续增加，直至达到最大值（雄性为-1.5立方毫米/胫骨，雌性为-2.2立方毫米/胫骨）。
