title: TiAl6V4particles promote osteoclast formation via autophagy-mediated downregulation of interferon-beta in osteocytes.
abstract: Wear debris-induced osteolysis is the leading cause of aseptic loosening, which is the most common reason for total hip arthroplasty (THA) failure in the medium and long term. Although osteocytes are the most abundant cells in bone and make direct contact with implants, the interaction between osteocytes and wear debris remains largely unknown. In the present study, we investigated the effect of TiAl6V4alloy particles (TiPs) on osteocytes and the subsequent effects on osteoclast formation. Our study demonstrated that osteocyte-conditioned medium (CM) inhibited osteoclast differentiation from bone marrow monocytes (BMMs) to osteoclasts. However, TiPs attenuated this inhibitory effect. The expression of several osteoclastogenesis-associated factors, including receptor activator of nuclear factor-kappaB ligand (RANKL), osteoprotegerin (OPG), nitric oxide (NO) and interferon-beta (IFN-β), was examined, and we found that TiPs markedly decreased the expression of IFN-β, but not the other factors. In an osteoclastogenesis assay, our results suggested that the downregulation of IFN-β mediated the stimulatory effect of TiPs on osteoclastogenesis. Additional evidence suggested that TiPs decreased the expression of IFN-β in osteocytes via macroautophagy (hereinafter referred to as "autophagy"). Moreover, inhibiting autophagy with Atg5 siRNA prevented the increase in osteoclastogenesis induced by TiPs. Collectively, these results suggested a possible mechanism underlying wear debris-induced osteolysis.
  
  
  
  For the first time, our study demonstrated that Ti-alloy particles attenuated the inhibitory effect of osteocytes-conditioned medium on osteoclast formation. With an osteoclastogenesis assay, we found that the downregulation of IFN-β in osteocytes mediated the promoting effect of TiPs on osteoclast formation. Furthermore, our results suggested that TiPs-induced autophagy mediated the downregulation of IFN-β in osteocytes. Inhibition of autophagy recovered the expression of IFN-β and ameliorated the promoting effect of TiPs on osteoclast formation. Collectively, these findings suggest a possible mechanism underlying wear debris-induced osteolysis and identified autophagy inhibition in osteocytes as a potential therapeutic approach for wear debris induced osteolysis.
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China; Department of Orthopaedics, The First Affiliated Hospital of Nanjing Medical University, 210029, China.
authors.forename: Zhenheng
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Zhantao
authors.initials: Z
authors.lastname: Deng
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Gan
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Tongguo
authors.initials: T
authors.lastname: Shi
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Qian
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Nirong
authors.initials: N
authors.lastname: Bao
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Guo
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Jiangning
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China; Department of Orthopaedics, The First Affiliated Hospital of Nanjing Medical University, 210029, China. Electronic address: njliuf@163.com.
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China. Electronic address: leidong@nju.edu.cn.
authors.forename: Lei
authors.initials: L
authors.lastname: Dong
authors.affiliation: Department of Orthopaedics, Jinling Hospital, School of Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 210093, China. Electronic address: zhaojianning.0207@163.com.
authors.forename: Jianning
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000497:Alloys; D000818:Animals; D001343:Autophagy / Q000187:drug effects*; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects*; D016899:Interferon-beta / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010011:Osteocytes / Q000187:drug effects / Q000378:metabolism*; D014025:Titanium / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000497:Alloys; D017077:Culture Media, Conditioned; C031462:titanium alloy (TiAl6V4); D016899:Interferon-beta; D014025:Titanium
keywords: IFN-β; Nanotoxicity; Osteoclastogenesis; Osteocytes; Wear particles