Yamashita T, Nabeshima Y, Noda M
Department of Molecular Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
J Endocrinol. 2000 Feb;164(2):239-45. doi: 10.1677/joe.0.1640239.
Inactivation mutation of the recently discovered klotho gene in mice causes a syndrome resembling aging. Manifestations include short life span, atherosclerosis, gonadal atropy, skin atropy, emphysema, ataxia and ectopic calcification. These mice also exhibit abnormally high bone density in the epiphyses of their tibiae based on X-ray and histological analyses. However, micro-structures of the trabecular bones in arbitrary two-dimensional planes or three-dimensional regions are difficult to analyze by these techniques. Therefore, we applied high resolution micro-computed tomography (microCT) to characterize the micro-structural abnormality in the trabecular bone in long bones as well as in vertebrae of four- to six-week-old klotho mutant mice. Two-dimensional microCT analyses in the mid-sagittal plane as well as three-dimensional microCT analyses indicated that the trabecular bone volume fraction measured in the proximal metaphyses of the tibiae was increased more than twofold in klotho mutant mice compared with the wild-type mice. Similarly, the trabecular bone area fraction in the mid-sagittal plane of the lumbar vertebral bodies was also increased by about 80% at the proximal and distal ends. No significant difference was observed with regard to the cortical thickness in the mid-shaft of femora between klotho mutant and wild-type mice. Three-dimensional microCT analyses also indicated that the trabecular number and thickness of the proximal metaphyses of the tibiae were increased by about 80% and 300% respectively in the klotho mutant mice, while trabecular separation was 60% less in klotho mutant mice compared with the wild-type mice. These quantitative microCT analyses indicate that the inactivation of klotho gene expression results in an increase in three-dimensional bone volume fraction, number and thickness of the trabecular bones in these mice.
最近在小鼠中发现的klotho基因的失活突变会导致一种类似衰老的综合征。其表现包括寿命缩短、动脉粥样硬化、性腺萎缩、皮肤萎缩、肺气肿、共济失调和异位钙化。基于X射线和组织学分析，这些小鼠胫骨骨骺的骨密度也异常高。然而，通过这些技术难以分析任意二维平面或三维区域内小梁骨的微观结构。因此，我们应用高分辨率微型计算机断层扫描（microCT）来表征4至6周龄klotho突变小鼠长骨和椎骨中小梁骨的微观结构异常。在矢状中平面进行的二维microCT分析以及三维microCT分析表明，与野生型小鼠相比，klotho突变小鼠胫骨近端干骺端测得的小梁骨体积分数增加了两倍多。同样，腰椎椎体矢状中平面近端和远端的小梁骨面积分数也增加了约80%。在klotho突变小鼠和野生型小鼠之间，股骨骨干中部的皮质厚度没有观察到显著差异。三维microCT分析还表明，klotho突变小鼠胫骨近端干骺端的小梁数量和厚度分别增加了约80%和300%，而与野生型小鼠相比，klotho突变小鼠的小梁间距减少了60%。这些定量microCT分析表明，klotho基因表达的失活导致这些小鼠三维骨体积分数、小梁骨数量和厚度增加。
