Micromorphological approaches to bone resorption and formation

主要对小鼠顶骨、股骨和胫骨进行扫描电子显微镜观察。用EDTA-KOH方法对成骨细胞、骨细胞和破骨细胞进行扫描电子显微镜观察，以溶解骨基质。用NaOCl浸渍或水射流法暴露骨基质或类骨质的表面。对部分顶骨进行背向散射法检查。在注射雌激素或切断下肢神经后，也对股骨和胫骨进行检查。结果表明或建议了以下几点。1)骨细胞和成骨细胞是功能不同的细胞，不同于普通的成骨前体细胞。骨细胞出现在成骨细胞的层中。2)成骨细胞在成骨细胞层下表面与类骨质表面之间的狭窄空间内拉长许多平行的、细长的细胞质突起，形成平行的狭窄间隙，以产生胶原纤维。因此，胶原蛋白纤维与骨基质平行产生。3)通过骨细胞的胞质突起将骨细胞埋入骨基质中，形成网状结构，检测骨应力负荷，并通过附着在成骨细胞突起上的胞质突起将应力信息传递给成骨细胞。4)骨细胞将形成的骨板的厚度告知局部成骨细胞。5)破骨细胞呈现2种不同功能活动的褶皱边缘。破骨细胞将骨基质分解为两种功能相。6)骨形成和骨吸收在功能上是耦合的。7)骨表面的背向散射图像显示了骨基质中胶原纤维钙化的不同阶段。

The mouse parietal bone, femur and tibia were examined mainly by scanning electron microscopy (SEM). Osteoblasts, osteocytes, and osteoclasts were exposed for SEM by our EDTA-KOH method to dissolve the bone matrix. The surfaces of the bone matrix or osteoid were exposed by a NaOCl maceration method or water jet. Some of parietal bones were examined by a back scattered method. Femurs and tibias were also examined after estrogen injections or cutting nerves for lower extremities. The results indicate or suggest the followings. 1) Osteocytes and osteoblasts are functionally different cells and differentiated from common osteogenic precursor cells. Osteocytes appears in the layr of osteoblasts. 2) Osteoblasts elongate many, parallel, long and thin cytoplasmic processes in the narrow spaces between the undersurface of the osteoblastic layr and the surface of the osteoid to form parallel narrow gaps for collagen fiber production. Thus, the collagen fibers are produced running parallel for the bone matrix. 3) Osteocytes are buried into the bone matrix by pulling by cytoplasmic processes of osteocytes and form meshwork to detect the stress loading to the bone and inform this information of stress to osteoblasts through the cytoplasmic processes attaching to the osteoblast processes. 4) Osteocytes inform the thickness of the forming bone lamella to the local osteoblasts. 5) Osteoclasts show 2 kinds of ruffled borders of different functional activities. Osteoclasts dissolve the bone matrix in 2 kinds of functional phases. 6) Bone formation and resorption are functionally coupled. 7) Back scattered images of the bone surfaces demonstrate the various stages of calcification of collagen fibers for the bone matrix.