Satomura K, Nagayama M
First Department of Oral and Maxillofacial Surgery, Tokushima University School of Dentistry, Japan.
Acta Anat (Basel). 1991;142(2):97-104. doi: 10.1159/000147172.
Rat bone marrow stromal cells were cultured in vitro. At days 14-15 of culture, dense clusters of polygonal cells were formed, and they mineralized 2-3 days later. The cells resembling osteoblasts or young osteocytes were histologically observed to be embedded in mineralized or unmineralized extracellular matrices of the nodules. Next, these mineralized nodules were electron-microscopically examined. The osteoblastic cells associated with the nodules had a well-developed rough endoplasmic reticulum, an evident Golgi apparatus and some mitochondria as their intracellular organellae. Some lysosomes and microfilaments were also visible in the cytoplasms. Moreover, some cells protruded cell processes toward the neighboring cells through the extracellular matrix. The extracellular matrix consisted of numerous collagen fibrils which were striated with 60-70 nm axial periodicity and which was similar to bone tissue collagen. A large number of matrix vesicles were scattered among the collagen fibrils in the unmineralized area of the nodules. In contrast, in the mineralized area, numerous matrix vesicles at different stages of maturation and many calcified spherules were observed. That is the mineralization in this culture system was considered to be initiated in association with the matrix vesicles and to progress along the collagen fibrils. From these findings, it was confirmed by the present study that the mineralized nodules formed in this bone marrow stromal cell culture were ultrastructurally similar to bone and that the mineralization also proceeded by going through the normal calcification process. This culture system is considered to be available to study osteogenic differentiation and calcification mechanisms.
大鼠骨髓基质细胞在体外培养。在培养的第14 - 15天，形成了密集的多边形细胞簇，2 - 3天后它们开始矿化。组织学观察发现，类似成骨细胞或年轻骨细胞的细胞嵌入到结节的矿化或未矿化细胞外基质中。接下来，对这些矿化结节进行电子显微镜检查。与结节相关的成骨细胞具有发达的粗面内质网、明显的高尔基体和一些线粒体作为其细胞内细胞器。细胞质中还可见一些溶酶体和微丝。此外，一些细胞通过细胞外基质向相邻细胞伸出细胞突起。细胞外基质由许多具有60 - 70 nm轴向周期性条纹的胶原纤维组成，与骨组织胶原相似。在结节的未矿化区域，大量基质小泡散布在胶原纤维之间。相比之下，在矿化区域，观察到许多处于不同成熟阶段的基质小泡和许多钙化球。也就是说，该培养系统中的矿化被认为是与基质小泡相关联开始的，并沿着胶原纤维进行。从这些发现中，本研究证实了在这种骨髓基质细胞培养中形成的矿化结节在超微结构上与骨相似，并且矿化也是通过正常的钙化过程进行的。该培养系统被认为可用于研究成骨分化和钙化机制。
