Inhibitory effect of titanium particles on osteoclast formation generated by treatment of mouse bone marrow cells with PGE2.
OBJECTIVE
The present study was designed to evaluate the effect of titanium (Ti) particles with no endotoxin on osteoclast differentiation and osteoclast activity in in vitro experiments.


METHODS
Osteoclast formation as well as osteoclastic bone resorbing activity were examined using the mouse bone marrow culture system and purified rabbit osteoclasts treated with Ti particles (2.5-20 microgram cm-2).


RESULTS
Ti particles, with no adherent endotoxin, inhibited osteoclastogenesis and receptor activator of NF-kappaB ligand (RANKL) expression in bone marrow cells treated with prostaglandin E2 (PGE2) (100 nM). The inhibitory effect of Ti particles was concentration-dependent (5-20 microgram cm-2), and was observed only on the generation of osteoclasts by PGE2, but not by 1,25-dihydroxyvitamin D3 or soluble RANKL. This suggests that Ti particles did not act uniformly on a common process in the generation of osteoclasts, but specifically on signal transduction for PGE2 in generating osteoclasts. In highly purified osteoclasts, Ti particles showed no effect on survival and bone resorbing activity.


CONCLUSIONS
Ti particles inhibited osteoclast differentiation and RANKL expression in mouse bone marrow cells treated with PGE2, without affecting mature osteoclast survival or activity. Thus, Ti particles may alter the osteoclastogenetic action of PGE2, which is one of the regulatory factors of bone remodeling.
Nakano
M
M
Department of Pharmacology, School of Dentistry, Aichi-Gakuin, University, Nagoya, Japan.
Tsuboi
T
T
Kato
M
M
Kurita
K
K
Togari
A
A
D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects* / Q000378:metabolism; D001862:Bone Resorption / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology*; D006023:Glycoproteins / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D010010:Osteoclasts / Q000187:drug effects*; D053244:Osteoprotegerin; D011817:Rabbits; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis; D018124:Receptors, Tumor Necrosis Factor; D014025:Titanium / Q000633:toxicity*
D006023:Glycoproteins; D053244:Osteoprotegerin; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C506031:Tnfrsf11b protein, mouse; D014025:Titanium; D015232:Dinoprostone