| Research Abstract |
The basic objection of this study is to elucidate the fine structural and cytochemical characteristics of the coupling phenomena between bone resorption and formation. The first objective was designed to elucidate The cyto chemical events between the osteoclastic bone resorption and subsequent osteoblastic bone formation. The ACPase positive resorbed bone surface continued to the cement line, on which osteoblasts were induced and formed a new bone. This suggests that the osyteoclasts may move as a resorbing bone and form a cement line, which may be a responsible for the coupling of the bone resorption and formation. The second objective was to reveal fine structural and cytochemical details on relationships between osteoclastic and osteoblastic cells in the differentiation and activation processes of osteoclasts. At first, LM and EM autoradiography(A.R) was performed on an organ culture using [^<125>I] calcitonin(CT) to identify osteoclastic cells.
Developed silver grains of [^<125>I]-C
… More
T were located on the TRACP-positive mono and multinucleated cells. In the EM-A.R, silver grains could be observed on the Golgi bodies and plasma membranes of both osteoblast progenitors and osteoclasts, suggesting that[^<125>I]-CT binds to receptors of plasma memoranes of osteoclastic cells, then internalized and turned to reach to the Goligi bodies. Ultrastructural and lectin-cytochemical observations were then carried out. Osteoblastic cells had close contact with differentiating osteoclasts, where focal connections and coated pits could frequently be observed in both osteoclastic and osteoblastic cells facing each other.
When mouse spleen cells were co-cultured with freshly isolated osteoblasts in the presence of 1,25-(OH)_2D_3, TRACF-positive multinuclear cells were formed. In this case, osteoblasts had also close contact with spleen cells in the same way as shown in vivo. These results indicate that osteoblastic cells are required for the differentiation of osteoclast orogenitors into osteoclasts by way of direct cell-cell contact, and this intimate cell contact presumably enables the osteoclast progenitors to respond to stimuli present on the osteoblastic cell surface. Lectin reaction was seen on Plasma membranes both in developing osteoclastic and adjacent osteoblastic cells suggesting that sugar residues on the plasma membrane may play a role in the cellular recognition via receptors, and also may be involved in concentrating appropriate amount of several local factors. Less
|
