[Techniques for purification of rabbit osteoclasts and analysis of their functions]

In the process of bone remodeling or modeling, the balance between bone formation and bone resorption maintains normality of function and structures of bone. Major bone-resorbing cells, osteoclasts, are terminally differentiated from hematopoietic stem cells and multinucleate cells. However, direct effects of osteotropic factors on osteoclast function have been unclear. Attempts to obtain isolated mammalian osteoclasts of high purity have been unsuccessful so far. Initially we succeeded in isolating osteoclasts of high purity using tissue culture dishes because of their high affinity for the tissue culture dishes, but the shortcoming of this method is that it was impossible to detach osteoclasts from the dishes. Therefore, we could not estimate bone-resorbing activity of mature osteoclasts on mineralizing substratum without any influence of bone-cells other than osteoclasts. Recently we developed a method to avoid the defect in the above-described method by the use of collagen gel. Our new method may shed new light on our understanding of the cellular and molecular mechanisms of osteoclasts.