| Research Abstract |
It is essential to obtain a specific marker for preosteoclasts to investigate the mechanism of cell-cell fusion between preosteoclasts, which is one of the important steps in osteoclastogenesis, We have previously found a unique cell surface antigen expressed on rat osteoclasts and osteoclast-like multinucleated cells formed in the bone marrow culture system. This antigen designated as Kat 1-antigen is also expressed on mononuclear cells observed in bone marrow culture system for forming osteoclasts, We have obtained several lines of evidence showing that mononuclear cells expressing Kat- 1 antigen are preosteoclasts. We have analyzed the surface phenotype of the preosteoclasts by use of FACS and found an interesting evidence showing that ICAM-1 and LFA-1, well known molecules as cell adhesion molecules, were expressed on preosteoclasts. We also obtained data strongly suggesting that LFA- 1 and ICAM- 1 expressed on preosteoclasts share an important role in the direct interaction and fu
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sion among preosteoclasts, By the way, HIV infection is accomplished by the membrane fusion between the virus outer membrane and the cytoplasmic membrane of target cells, In this process, it has been reported that the chemokine receptors are essential. During the course of other project to investigate the expression of MIP- 1alpha a member of the CC chemokine family, in human bone tissues, we have obtained data suggesting an involvement of chemokine receptors in the process of fusion among preosteoclasts.
In order to analyze a detailed mechanism of the fusion process, it is essential to obtain a cell culture system consisted of only preosteoclasts. One way is to purify preosteoclasts using Magnetic Cell Separator after reacting preosteoclasts with anti-Kati monoclonal antibody folloed by conjugation with magnetic beads. The other way is to establish cell clones full-filling the criteria of preosteoclasts. Concerning the former approach, we have succeeded in enriching preosteoclasts to approximately 60 %. In respect to the latter way, we have already succeeded in preparing a gene construct for obtaining preosteoclast clones and are now performing the preparation of a panel of preosteoclast clones. Through the analysis of these various preosteoclast clones, we will be able to reach a profound understanding concerning the fusion process in osteoclastogenesis. Less
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