Abstract:

Objective To investigate whether c-Jun N-terminal kinase(JNK)-mediated apoptosis and autophagy is involved in osteocytes death induced by tricalciumphosphate(TCP) wear particles in the mouse calvaria. Methods Thirty-six 6-week ICR male mice were randomly divided into three groups: normal control groups (n=12), TCP wear particles groups (n=12) and SP600125-treated groups (n=12). A murine calvarial model of osteolysis was established by 30 mg of TCP wear particles implantation onto the surface of bilateral parietal bones following removal of the periosteum. On the second postoperative day, the SP600125-treated mice were locally injected with the specific inhibitor of JNK pathway (SP600125, 1.0 mg/kg) on the the calvaria under the periosteum each time every three days. After 2 weeks of continuous treatment, the animals were sacrificed and the calvaria were obtained. Calcein-AM labelling and HE staining were used to observe the morphology and viability of calvaria osteocytes; flow cytometry was performed to detected apoptosis of calvaria osteocyte obtained by enzyme digestion; Western blotting was used to examine protein expression of Bcl-2, Bax, p-JNK, Beclin-1 and LC-3 in calvaria osteocytes, respectively. Results Compared with the control group, the viability of calvaria osteocytes was significantly reduced, leading to the obvious increases in the percentage of empty lacunae and osteocyte apoptosis in the TCP group (P<0.05); protein expressions of p-JNK, Beclin-1 and LC-3, and the conversion of LC3-Ⅱ from LC3-Ⅰ were both increased remarkably (P<0.05). Compared with the TCP group, the percentage of apoptosis in calvaria osteocytes decreased, and expression of autophagyrelated protein was obviously inhibited in the SP600125 group (P<0.05). Conclusion JNK-mediated apoptosis and autophagy is involved in osteocytes death induced by TCP wear particle in the calvaria.

Key words: Tricalciumphosphate wear particles, Osteolysis, Osteocyte, c-Jun N-terminal kinase pathway, Prosthesis, Werstern blotting, Mouse