Compressive mechanical stress promotes osteoclast formation through RANKL expression on synovial cells.
OBJECTIVE
We investigated the effects of compressive mechanical stress on osteoclastogenesis of synovial cells to clarify the mechanism of osteoclast formation by those cells in temporomandibular joint (TMJ) disorders.


METHODS
Synovial cells were isolated from rat knee joints and continuously compressed using a conventional method. The expression of receptor activator nuclear factor kappaB ligand (RANKL) mRNA and protein in synovial cells was analyzed by reverse transcriptase-polymerase chain reaction, immunoblotting, and immunofluorescence staining. Mouse bone marrow cells were cultured with synovial cells for 7 days to detect osteoclasts.


RESULTS
The expressions of RANKL mRNA and protein in synovial cells were increased with compressive force. When mouse bone marrow cells were cultured with continuously compressed synovial cells, tartrate-resistant acid phosphatase-positive multinucleated cells were formed. Osteoprotegerin completely inhibited osteoclast formation induced by culturing with compressed synovial cells.


CONCLUSIONS
Our results indicated that the expression of RANKL in compressed synovial cells enhanced osteoclast formation, whereas continuous compressive force may induce osteoclastic bone destruction in the TMJ.
Ichimiya
Hisashi
H
Division of Oral and Maxillofacial Reconstructive Surgery, Department of Oral and Maxillofacial Surgery, Kyushu dental college, Kita-Kyushu, Japan.
Takahashi
Tetsu
T
Ariyoshi
Wataru
W
Takano
Hiroshi
H
Matayoshi
Takaaki
T
Nishihara
Tatsuji
T
D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology; D002454:Cell Differentiation; D002478:Cells, Cultured; D018920:Coculture Techniques; D019245:Compressive Strength; D003799:Dental Stress Analysis; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008856:Microscopy, Fluorescence; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects; D053244:Osteoprotegerin / Q000494:pharmacology; D053245:RANK Ligand / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D013583:Synovial Membrane / Q000166:cytology / Q000378:metabolism*; D013705:Temporomandibular Joint Disorders / Q000473:pathology*
D053244:Osteoprotegerin; D053245:RANK Ligand