Inhibition of osteoclastogenesis by RNA interference targeting RANK.
BACKGROUND
Osteoclasts and osteoblasts regulate bone resorption and formation to allow bone remodeling and homeostasis. The balance between bone resorption and formation is disturbed by abnormal recruitment of osteoclasts. Osteoclast differentiation is dependent on the receptor activator of nuclear factor NF-kappa B (RANK) ligand (RANKL) as well as the macrophage colony-stimulating factor (M-CSF). The RANKL/RANK system and RANK signaling induce osteoclast formation mediated by various cytokines. The RANK/RANKL pathway has been primarily implicated in metabolic, degenerative and neoplastic bone disorders or osteolysis. The central role of RANK/RANKL interaction in osteoclastogenesis makes RANK an attractive target for potential therapies in treatment of osteolysis. The purpose of this study was to assess the effect of inhibition of RANK expression in mouse bone marrow macrophages on osteoclast differentiation and bone resorption.


METHODS
Three pairs of short hairpin RNAs (shRNA) targeting RANK were designed and synthesized. The optimal shRNA was selected among three pairs of shRNAs by RANK expression analyzed by Western blot and Real-time PCR. We investigated suppression of osteoclastogenesis of mouse bone marrow macrophages (BMMs) using the optimal shRNA by targeting RANK.


RESULTS
Among the three shRANKs examined, shRANK-3 significantly suppressed [88.3%] the RANK expression (p < 0.01). shRANK-3 also brought about a marked inhibition of osteoclast formation and bone resorption as demonstrated by tartrate-resistant acid phosphatase (TRAP) staining and osteoclast resorption assay. The results of our study show that retrovirus-mediated shRANK-3 suppresses osteoclast differentiation and osteolysis of BMMs.


CONCLUSIONS
These findings suggest that retrovirus-mediated shRNA targeting RANK inhibits osteoclast differentiation and osteolysis. It may appear an attractive target for preventing osteolysis in humans with a potential clinical application.
Department of Orthopaedics, University of Duisburg-Essen, Essen, Germany.
Ruofan
R
Ma
Jie
J
Xu
Bin
B
Dong
Max Daniel
MD
Kauther
Marcus
M
Jäger
Christian
C
Wedemeyer
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics; D002478:Cells, Cultured; D005822:Genetic Vectors; D007527:Isoenzymes / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D008807:Mice, Inbred BALB C; D010010:Osteoclasts / Q000378:metabolism* / Q000648:ultrastructure; D010014:Osteolysis / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000235:genetics / Q000378:metabolism*; D012190:Retroviridae / Q000235:genetics; D000071681:Tartrate-Resistant Acid Phosphatase; D014162:Transfection
D015415:Biomarkers; D007527:Isoenzymes; D034741:RNA, Small Interfering; D053246:Receptor Activator of Nuclear Factor-kappa B; C505687:Tnfrsf11a protein, mouse; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase