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J Cell Biochem. 2018 Sep 6. doi: 10.1002/jcb.27468. [Epub ahead of print]

Osteoprotegerin inhibit osteoclast differentiation and bone resorption by enhancing autophagy via AMPK/mTOR/p70S6K signaling pathway in vitro.

Tong X1,2,3,4, Gu J1,2,3,4, Song R1,2,3,4, Wang D1,2,3,4, Sun Z1,2,3,4, Sui C1,2,3,4, Zhang C1,2,3,4, Liu X1,2,3,4, Bian J1,2,3,4, Liu Z1,2,3,4.

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College of Veterinary Medicine, Yangzhou University, Yangzhou, China.
Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China.
Jiangsu Key Laboratory of Zoonosis, Yangzhou, China.
Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, China.


Osteoclasts are highly differentiated terminal cells formed by fusion of hematopoietic stem cells. Previously, osteoprotegerin (OPG) inhibit osteoclast differentiation and bone resorption by blocking receptor activator of nuclear factor-κB ligand (RANKL) binding to RANK indirect mechanism. Furthermore, autophagy plays an important role during osteoclast differentiation and function. However, whether autophagy is involved in OPG-inhibited osteoclast formation and bone resorption is not known. To elucidate the role of autophagy in OPG-inhibited osteoclast differentiation and bone resorption, we used primary osteoclast derived from mice bone marrow monocytes/macrophages (BMM) by induced M-CSF and RANKL. The results showed that autophagy-related proteins expression were upregulated; tartrate-resistant acid phosphatase-positive osteoclast number and bone resorption activity were decreased; LC3 puncta and autophagosomes number were increased and activated AMPK/mTOR/p70S6K signaling pathway. In addition, chloroquine (as the autophagy/lysosome inhibitor, CQ) or rapamycin (as the autophagy/lysosome inhibitor, Rap) attenuated osteoclast differentiation and bone resorption activity by OPG treatment via AMPK/mTOR/p70S6K signaling pathway. Our data demonstrated that autophagy plays a critical role in OPG inhibiting osteoclast differentiation and bone resorption via AMPK/mTOR/p70S6K signaling pathway in vitro.


70‐kDa ribosomal protein S6 kinase; AMP‐activated protein kinase; mammalian target of rapamycin; osteoclast; osteoprotegerin


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