Journal of Oral Tissue Engineering

Effect of Akt on the Differentiation into Osteoclasts Caused by RANKL Stimulation

Toshiya KAWASAKI1, Seiji GODA2 and Naoyuki MATSUMOTO3

1Graduate School of Dentistry of Department of Orthodontics,
2Department Biochemistry and 3 Department Orthodontics,
Osaka Dental University, Osaka, Japan

J Oral Tissue Engin 2012;10(2):67-76

Orthodontic therapy applies physical stimulation to the compression-side periodontium, which produces inflammatory cytokines and receptor activators of nuclear factor kappa-B ligand (RANKL). With these proteins, osteoclast precursors such as monocytes and macrophages migrate from vessels into the periodontium and then differentiate into osteoclasts, causing bone resorption. Phosphatidy-linositol 3-kinase (PI3-kinase) regulates this differentiation into osteoclasts and bone resorption. PDK1(3-phosphoinositide-dependent protein kinase 1) and Akt (protein kinase B) exist downstream of PI3-kinase. Therefore, in order to clarify the involvement of Akt in the differentiation into osteoclasts, we tested the effects of Akt Inhibitor V, RANKL, and the PDK inhibitor, OSU-03012 on the differentiation of RAW264.7 cells into osteoclasts. Both Akt Inhibitor V and OSU-03012 inhibited the differentiation into osteoclasts of RAW264.7 cells stimulated with RANKL. RANKL-induced phosphorylation of Akt (Thr308) was inhibited in RAW264.7 cells by OSU-03012, while RANKL-induced phosphorylation of Akt (Ser473) was not. These results suggest that Akt (Thr308, but not Ser473) exist upstream of the RANKL stimulation in the differentiation cascade of RAW264.7 cells into osteoclasts.

Key words: osteoclast, PI3k, Akt, RANKL