Micromorphological approaches to bone resorption and formation

以扫描电子显微镜（SEM）对小鼠顶骨、股骨和胫骨进行观察。用EDTA-KOH法将成骨细胞、骨细胞和破骨细胞暴露于扫描电镜下，使骨基质溶解。骨基质或类骨表面采用NaOCl浸渍法或水射流暴露。一些顶骨是用背散法检查的。注射雌激素或切断下肢神经后也检查股骨和胫骨。结果表明或建议如下。1)骨细胞和成骨细胞是功能不同的细胞，是从常见的成骨前体细胞分化而来的。成骨细胞出现在成骨细胞层。2)成骨细胞在成骨层下表面与类骨表面之间的狭窄间隙中拉长许多平行的细长细胞质突，形成平行的狭窄间隙，用于胶原纤维的生产。因此，胶原纤维的产生与骨基质平行。3)骨细胞被骨细胞的细胞质突拉入骨基质中，形成网状结构，检测骨的应力负荷，并通过附着在成骨突上的细胞质突将应力信息告知成骨细胞。4)骨细胞将形成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界。破骨细胞溶解骨基质分为两种功能阶段。骨形成和骨吸收在功能上是耦合的。7)骨表面背面的散点图像显示骨基质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.