Mechanisms involved in the enhancement of osteoclast formation by enamel matrix derivative.
OBJECTIVE
Enamel matrix derivative (EMD) is used clinically to promote periodontal tissue regeneration, and it has been reported that EMD can induce the formation of osteoclasts in mouse marrow cultures. In the present study, we investigated the mechanisms of EMD-induced osteoclast formation using a mouse monocytic cell line, RAW 264.7.


METHODS
Bioactive fractions were purified from EMD by reverse-phase HPLC using a C18 hydrophobic support, following which RAW 264.7 cells were cultured with EMD or its purified fractions in the presence of receptor activator of nuclear factor-kappaB ligand (RANKL) for 8 d. Following staining with tartrate-resistant acid phosphatase (TRAP), TRAP-positive multinucleated cells were counted. The expression of receptor activator of nuclear factor-kappaB (RANK), as well as phosphorylation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein (MAP) kinase, in RAW 264.7 cells were detected using immunoblotting. To determine whether EMD has an effect on osteoclast function, differentiated RAW 264.7 cells were cultured on Osteologic Multitest slides with RANKL in the presence of EMD.


RESULTS
Purified EMD fractions (fraction numbers 21-25; EMD peak 2) were found to enhance the formation and function of RAW 264.7 cells induced by RANKL. Moreover, EMD peak 2 enhanced the levels of phosphorylation of ERK p38 and RANK in RAW 264.7 cells stimulated with RANKL.


CONCLUSIONS
Our results indicate that EMD induces the formation of osteoclasts through interaction with RANKL, while ERK and p38 MAPK may play a critical role in the enhancement of osteoclast formation in RAW 264.7 cells.
Itoh
N
N
Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental College, Kitakyushu, Japan.
Kasai
H
H
Ariyoshi
W
W
Harada
E
E
Yokota
M
M
Nishihara
T
T
D000818:Animals; D015153:Blotting, Western; D001861:Bone Regeneration / Q000187:drug effects*; D002352:Carrier Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D003746:Dental Enamel Proteins / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000494:pharmacology; D051379:Mice; D008815:Mice, Inbred Strains; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects*; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D002352:Carrier Proteins; D003746:Dental Enamel Proteins; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; C109069:enamel matrix proteins; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases