Factors affecting Osteoclast Formation

Chang, J S; Park, J H; Kim, J H; Kim, K Y

Abstract

Recently many kinds of osteotropic factors and cytokines were identified to be acting in the process of the osteoclast formation. However, their reported effects were so variable that it is very difficult to understand their roles and potency in different conditions. This study was performed to compare the activities of these regulating factors on the osteoclastogenesis in a concentration of usual dose. We used a co-culture system of mouse spleen and ST2 cells, in which osteoclast-like multinucleated cells were formed in response to Vitamin D and dexamethasone. Tartrate Resistant Acid Phosphatase (TRAP) positive giant cells having calcitonin receptor were regarded as osteoclast-like cells and eight"kinds of osteotropic factors were examined. The most profound increase in TRAP+ cells was found in a group of cells cultured in IL-11 treated media (about 209 TRAP+ cells), and IL-6 also induced significant increase in osteoclast formation (156 TRAP+ cells). PTH, endothelin and estrogen, which were known to affect osteoclastogenesis, showed no remarkable effect on osteoclastogenesis compared with control group which only dealt with Vit-D and dexamethasone (31-45 TRAP+ cells), but retinoic acid inhibited the osteoclast formation. The synthetic RGD protein, which had ability to interfere adehesion of mature osteoclast, didn't show any inhibitory effect in the osteoclast formation. In conclusion, IL-11 and IL-6 had the greatest ability to activate the hematopoietic cells to differentiate into osteoclast-like cells in this culture system.