ABSTRACT
Objective To explore the role of the PI3K/Akt signaling pathway in the calvarial osteolysis induced by TCP wear particles in mice model.Methods Thirty-six male ICR mice were randomly divided into a sham group (n=12),TCP group (n=12)and a LY294002-treated group (n=12).A murine calvarial model of osteolysis was established through implanting 30 mg of TCP particles onto the surface of bilateral parietal bones following the removal of the periosteum.On the second postoperative day,LY294002 (5 mg·kg-1)was locally injected to the calvarium under the periosteum three times a week;mice in the sham group received local injection of normal saline (N.S.)in the calvarium,and the injection time was consistent with that of LY294002.Two weeks later,the calvaria and periostea were obtained after the mice were executed.The calvarial osteolysis,bone mineral density (BMD)and bone mineral content(BMC)were analyzed using Micro-CT,Hematoxylin-Eosin (HE)staining was conducted to observe the inflammatrory response and formation of osteoclasts.Real-time PCR was applied to detect the mRNA level of tartrate-resistant acid phosphatase (TRAP),the marker of osteoclasts formation,cathepsin K (CstK),receptor activator for nuclear factor-κB kigand (RANKL)and c-Fos.The release of tumor necrosis factor-α (TNF-α),interleukin-6 (IL-6)and IL-1β were measured using enzyme-linked immumsorbent assay (ELISA).Results Micro-CT and histological analysis indicated that LY294002,the specific inhibitor of PI3K,significantly prevented TCP wear particles-induced osteolysis and osteoclastogenesis,and increased BMD and BMC in the calvaria of mice.Real-time PCR data revealed LY294002 significantly suppressed the increase in mRNA level of osteoclastogenic genes such as TRAP,CstK,RANKL and c-Fos in the calvaria of TCP wear particles-implanted group.ELISA assay showed that TCP wear particles-induced release of TNF-α,IL-1β and IL-6 was significantly inhibited by LY294002 treatment.Furthermore,LY294002 significantly attenuated TCP wear particles-triggered activation of Akt,and down-regulated the level of p-AktSer473 and p-AktThr308.Conclusion PI3K/Akt signaling pathway contributes to TCP wear particle-induced osteolysis,and can be developed as a new therapeutic target for the prevention and treatment of bone destruction diseases caused by wear debris.