Department of Biological Information, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan.
Dev Biol. 2011 Dec 1;360(1):96-109. doi: 10.1016/j.ydbio.2011.09.013. Epub 2011 Sep 21.
Bone modeling is the central system controlling the formation of bone including bone growth and shape in early development, in which bone is continuously resorbed by osteoclasts and formed by osteoblasts. However, this system has not been well documented, because it is difficult to trace osteoclasts and osteoblasts in vivo during development. Here we showed the important role of osteoclasts in organogenesis by establishing osteoclast-specific transgenic medaka lines and by using a zebrafish osteoclast-deficient line. Using in vivo imaging of osteoclasts in the transgenic medaka carrying an enhanced GFP (EGFP) or DsRed reporter gene driven by the medaka TRAP (Tartrate-Resistant Acid Phosphatase) or Cathepsin K promoter, respectively, we examined the maturation and migration of osteoclasts. Our results showed that mononuclear or multinucleated osteoclasts in the vertebral body were specifically localized at the inside of the neural and hemal arches, but not at the vertebral centrum. Furthermore, transmission electron microscopic (TEM) analyses revealed that osteoclasts were flat-shaped multinucleated cells, suggesting that osteoclasts initially differentiate from TRAP-positive mononuclear cells residing around bone. The zebrafish panther mutant lacks a functional c-fms (receptor for macrophage colony-stimulating factor) gene crucial for osteoclast proliferation and differentiation and thus has a low number of osteoclasts. Analysis of this mutant revealed deformities in both its neural and hemal arches, which resulted in abnormal development of the neural tube and blood vessels located inside these arches. Our results provide the first demonstration that bone resorption during bone modeling is essential for proper development of neural and vascular systems associated with fish vertebrae.
骨重建是控制骨形成的核心系统，包括早期发育过程中的骨生长和形状，在此过程中，破骨细胞不断吸收骨，成骨细胞形成骨。然而，这个系统还没有得到很好的记录，因为在发育过程中很难追踪破骨细胞和成骨细胞。在这里，我们通过建立破骨细胞特异性转基因斑马鱼系和使用破骨细胞缺陷的斑马鱼系，显示了破骨细胞在器官发生中的重要作用。利用携带增强型 GFP（EGFP）或 DsRed 报告基因的转基因斑马鱼中破骨细胞的体内成像，该报告基因分别由鱼类 TRAP（抗酒石酸酸性磷酸酶）或组织蛋白酶 K 启动子驱动，我们检查了破骨细胞的成熟和迁移。我们的结果表明，椎体中的单核或多核破骨细胞特异性定位于神经弓和血弓的内部，而不是椎体中心。此外，透射电子显微镜（TEM）分析表明，破骨细胞为扁平状多核细胞，提示破骨细胞最初从骨周围的 TRAP 阳性单核细胞分化而来。panther 突变体缺乏功能性 c-fms（巨噬细胞集落刺激因子受体）基因，该基因对于破骨细胞的增殖和分化至关重要，因此破骨细胞数量较少。对这种突变体的分析表明，其神经弓和血弓都存在畸形，导致位于这些弓内的神经管和血管异常发育。我们的结果首次证明，骨重建过程中的骨吸收对于与鱼类椎体相关的神经和血管系统的正常发育是必不可少的。
