Genetic and pharmacological activation of Hedgehog signaling inhibits osteoclastogenesis and attenuates titanium particle-induced osteolysis partly through suppressing the JNK/c-Fos-NFATc1 cascade

• Published in: Theranostics Vol. 10; no. 15; pp. 6638 - 6660
• Main Authors: Zhang, Liwei, Yang, Yanjun, Liao, Zirui, Liu, Qingbai, Lei, Xinhuan, Li, Meng, Saijilafu, Zhang, Zunyi, Hong, Dun, Zhu, Min, Li, Bin, Yang, Huilin, Chen, Jianquan
• Format: Journal Article
• Language: English
• Published: Australia Ivyspring International Publisher Pty Ltd 01-01-2020; Ivyspring International Publisher
• Subjects: Animals; Antibodies; Arthritis; Bone marrow; Cell culture; Cell Differentiation; Cells, Cultured; Disease Models, Animal; Gene Knock-In Techniques - methods; Hedgehog Proteins - genetics; Hedgehog Proteins - metabolism; JNK Mitogen-Activated Protein Kinases; Kinases; Laboratory animals; Ligands; Macrophages - cytology; Macrophages - drug effects; Macrophages - metabolism; Male; Mice; Mice, Inbred C57BL; Morpholines - pharmacology; NFATC Transcription Factors - metabolism; Osteoclasts - cytology; Osteoclasts - drug effects; Osteoclasts - metabolism; Osteogenesis; Osteolysis - chemically induced; Osteolysis - metabolism; Osteolysis - pathology; Osteolysis - therapy; Proteins; Proto-Oncogene Proteins c-fos - metabolism; Purines - pharmacology; Rabbits; Repressor Proteins - genetics; Research Paper; Signal Transduction; Titanium - toxicity; United States > US; China; titanium particle; peri-prosthetic osteolysis; osteoclatogenesis; Hh signaling
• ISSN: 1838-7640; 1838-7640
• DOI: 10.7150/thno.44793

Wear particle-induced periprosthetic osteolysis (PPO) is a common long-term complication of total joint arthroplasty, and represents the major cause of aseptic loosening and subsequent implant failure. Previous studies have identified the central role of osteoclast-mediated bone resorption in the pathogenesis of PPO. Thus, therapeutic approaches of inhibiting osteoclast formation and activity are considered to be of great potential to prevent and treat this osteolytic disease. Hedgehog (Hh) signaling has been shown to play an important role in promoting osteoblast differentiation and bone formation. While Hh signaling is also implicated in regulating osteoclastogenesis, whether it can directly inhibit osteoclast differentiation and bone resorption remains controversial. Moreover, its potential therapeutic effects on PPO have never been assessed. In this study, we explored the cell-autonomous role of Hh signaling in regulating osteoclastogenesis and its therapeutic potential in preventing wear particle-induced osteolysis.
Hh signaling was activated in macrophages by genetically ablating
in these cells using
or by treating them with purmorphamine (PM), a pharmacological activator of Smoothened (Smo).
cell-autonomous effects of Hh pathway activation on RANKL-induced osteoclast differentiation and activity were evaluated by TRAP staining, phalloidin staining, qPCR analyses, and bone resorption assays.
evaluation of its therapeutic efficacy against PPO was performed in a murine calvarial model of titanium particle-induced osteolysis by μCT and histological analyses. Mechanistic details were explored in RANKL-treated macrophages through Western blot analyses.
We found that
deletion or PM treatment potently activated Hh signaling in macrophages, and strongly inhibited RANKL-induced TRAP
osteoclast production, F-actin ring formation, osteoclast-specific gene expression, and osteoclast activity
. Furthermore, we found that
deletion or PM administration significantly attenuated titanium particle-induced osteoclast formation and bone loss
. Our mechanistic study revealed that activation of Hh signaling suppressed RANKL-induced activation of JNK pathway and downregulated protein levels of two key osteoclastic transcriptional factors, c-Fos and its downstream target NFATc1.
Both genetic and pharmacological activation of Hh signaling can cell-autonomously inhibit RANKL-induced osteoclast differentiation and activity
and protect against titanium particle-induced osteolysis
. Mechanistically, Hh signaling hinders osteoclastogenesis partly through suppressing the JNK/c-Fos-NFATc1 cascade. Thus, Hh signaling may serve as a promising therapeutic target for the prevention and treatment of PPO and other osteolytic diseases.