Tanaka-Kamioka K, Kamioka H, Ris H, Lim S S
Department of Anatomy, Indiana University Medical Center, Indianapolis 46202, USA.
J Bone Miner Res. 1998 Oct;13(10):1555-68. doi: 10.1359/jbmr.1998.13.10.1555.
Osteocytes are derived from a select group of osteoblasts that have undergone a final differentiation. Due to their inaccessibility when embedded in the bone matrix, very little is known about the osteocyte cytoskeleton. This study provides an extensive analysis of the osteocyte cytoskeleton, based on the successful isolation of osteocytes from 16-day embryonic chick calvariae. We used OB7.3, a chicken osteocyte-specific monoclonal antibody, to confirm the osteocytic phenotype of the isolated cells and established culture conditions to promote growth of cells that most resemble osteocytes in vivo. Immunofluorescence staining with antitubulin, antivimentin, and antiactin showed the relative distribution of the microtubules, intermediate filaments, and actin filaments in both osteocyte cell body and processes. Field emission scanning electron microscopy revealed the three-dimensional relationships of the cytoskeletal elements and a unique organization of actin bundles that spanned the cell body and osteocyte processes. When combined with drug studies, these experiments demonstrate that actin filaments are crucial for the maintenance of osteocyte shape. Furthermore, we identified two actin-bundling proteins, alpha-actinin and fimbrin, in osteocyte processes. The prominence and unique distribution of fimbrin in osteocyte processes provides the possibility of its use as an intracellular marker to distinguish osteocytes from osteoblasts.
骨细胞源自经过最终分化的特定成骨细胞群体。由于其嵌入骨基质后难以接近，人们对骨细胞的细胞骨架了解甚少。本研究基于从16日龄胚胎鸡颅骨成功分离出骨细胞，对骨细胞的细胞骨架进行了广泛分析。我们使用鸡骨细胞特异性单克隆抗体OB7.3来确认分离细胞的骨细胞表型，并建立培养条件以促进在体内最类似于骨细胞的细胞生长。用抗微管蛋白、抗波形蛋白和抗肌动蛋白进行免疫荧光染色，显示了微管、中间丝和肌动蛋白丝在骨细胞胞体和突起中的相对分布。场发射扫描电子显微镜揭示了细胞骨架元件的三维关系以及横跨胞体和骨细胞突起的肌动蛋白束的独特组织。当与药物研究相结合时，这些实验表明肌动蛋白丝对于维持骨细胞形状至关重要。此外，我们在骨细胞突起中鉴定出两种肌动蛋白束蛋白，α-辅肌动蛋白和丝束蛋白。丝束蛋白在骨细胞突起中的突出和独特分布为将其用作区分骨细胞和成骨细胞的细胞内标记物提供了可能性。
