Isolation of osteoclast-forming factor produced by stromal cells and mechanism of osteoclast differentiation

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I have succeeded to isolate the stromal cell line, which can support osteoclast formation from spleen cells and named as TMS-14 and 14. Using these stromal cells we studied the mechanism of osteoclast formation. As a result, osteoclast formation will be necessary for cAMP elevation in the stromal cells and an activation of A-kinase. And also the contact between spleen cells and stromal cells is also needed. Therefore, we next studied what adhesion molecule is important for osteoclast formation. In stromal cells ICAM-1 was expressed and in osteoclast progenitor cells LFA-1 and ICAM-1 were expressed. The antibodies for ICAM-1 and LFA-1 was added in the osteoclast formation system, the formation of osteoclast was significantly suppressed. However, the inhibition rate was only 50%. These results suggest that the other adhesion molecules was involved for osteoclast formation.Stromal cells release osteoclast formation-stimulating factors as well as inhibiting factors. We failed to isolate the stimulators, but succeeded to characterize the inhibitory factors for osteoclast formation. The inhibitor was released from osteoblasts as well as stromal cells and the moleculr weight will be over 10000. The inhibitor can be regulated by some anti-osteoporosis drugs. This means that some drugs for osteoporosis affects via a production of this inhibitor for osteoclast formation.