Department of Orthopaedic Surgery, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA.
Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, USA.
Hum Mol Genet. 2019 May 15;28(10):1738-1751. doi: 10.1093/hmg/ddz012.
The dystrophin-/-/utrophin-/-/ double knockout (dKO-Hom) mouse is a murine model of human Duchenne muscular dystrophy. This study investigated the bone and muscle abnormalities of dKO-Hom mouse and mechanisms. We collected bone and skeletal muscle samples from control mice and three muscular dystrophic mouse models at different ages and performed micro-computer tomography and histological analyses of both bone and skeletal muscle tissues. Serum receptor activator of nuclear factor kappa-Β ligand (RANKL) and sclerostin (SOST) levels, osteoclastogenesis and serum proteomics were also analyzed. Our results indicated that dKO-Hom mice developed skeletal muscle histopathologies by 5 days of age, whereas bone abnormalities developed at 4 weeks of age. Furthermore, our results indicated that the numbers of osteoblasts and osteoclasts were decreased in the proximal tibia and spine trabecular bone of dKO-Hom mice compared to wild-type (WT) mice, which correlated with a significant reduction in serum RANKL levels. The number of tibia cortical osteocytes also decreased, whereas serum SOST levels increased significantly in dKO-Hom mice than WT mice. Osteoblastic number was significantly lower, but osteoclast number increased, in the spine L6 of dKO-Hom mice than WT mice at 6 weeks of age, resulting in a decrease in bone formation and an increase in bone resorption. Serum proteomics results revealed abnormal proteome profiles in dKO-Hom mice compared to control mice. In conclusion, our study elucidated the timing of development of bone and muscle abnormalities. The bone abnormalities in dKO-Hom mice are correlated with lower serum RANKL and higher SOST levels that resulted in dysregulation of osteogenesis and osteoclastogenesis and bone loss.
肌营养不良症双敲除（dKO-Hom）小鼠是人类杜氏肌营养不良症的一种鼠模型。本研究探讨了 dKO-Hom 小鼠的骨骼和肌肉异常及其机制。我们收集了不同年龄的对照小鼠和三种肌肉营养不良小鼠模型的骨骼和骨骼肌样本，对骨骼和骨骼肌组织进行了微计算机断层扫描和组织学分析。还分析了血清核因子κB 受体激活剂配体（RANKL）和硬化蛋白（SOST）水平、破骨细胞生成和血清蛋白质组学。我们的结果表明，dKO-Hom 小鼠在 5 天大时就出现了骨骼肌组织病理学改变，而骨骼异常则在 4 周龄时发生。此外，我们的结果表明，与野生型（WT）小鼠相比，dKO-Hom 小鼠的胫骨近端和脊柱小梁骨中的成骨细胞和破骨细胞数量减少，这与血清 RANKL 水平显著降低有关。胫骨皮质骨细胞数量也减少，而 dKO-Hom 小鼠的血清 SOST 水平明显高于 WT 小鼠。与 WT 小鼠相比，dKO-Hom 小鼠在 6 周龄时的 L6 脊柱中的成骨细胞数量明显减少，但破骨细胞数量增加，导致骨形成减少和骨吸收增加。血清蛋白质组学结果表明，与对照小鼠相比，dKO-Hom 小鼠的蛋白质组谱异常。总之，我们的研究阐明了骨骼和肌肉异常的发展时间。dKO-Hom 小鼠的骨骼异常与血清 RANKL 降低和 SOST 升高有关，导致成骨和破骨细胞失调以及骨丢失。
