Differentiation of activated monocytes into osteoclast-like cells on a hydroxyapatite substrate: an in vitro study.
BACKGROUND
Hydroxyapatite surface coatings of dental implants have been introduced to obtain more rapid and complete osteointegration. A possible complication associated with hydroxyapatite implant surface is the release of particles. Those particles may be phagocytosed by monocytes, the first cells to colonize the inflammatory sites. The activated monocytes produce cytokines that could cause osteoclast activation.


METHODS
In order to establish the biological effect of particles released on monocyte differentiation to an osteoclast phenotype, we have used the murine monocyte/macrophage cell line, RAW 264.7 clone CRL-2278 cultured on a hydroxyapatite substrate. The direct action of hydroxyapatite on monocyte differentiation was examined using tartrate-resistant acid phosphatase (TRAP), immunohistochemistry and transmission electron microscopy (TEM) and Western Blot analysis.


RESULTS
The present study demonstrated that hydroxyapatite substrate might be able to induce a self-production of RANKL cytokine that directly stimulates a different behaviour in terms of phenotype expression from monocyte/macrophage lineage to mature and functional osteoclasts without the addition of exogenous factors.


CONCLUSIONS
These studies were designed to test a model in which osteoclasts could be formed from HA-activated monocytes via positive feedback elicited by RANKL, allowing for identification of innovative targets for therapeutic approaches.
Narducci
Paola
P
Department of Biomedicine, University of Trieste, Via Manzoni 16, Trieste, Italy.
Nicolin
Vanessa
V
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D017886:Durapatite; D015151:Immunoblotting; D007249:Inflammation / Q000473:pathology / Q000503:physiopathology; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D008858:Microscopy, Phase-Contrast / Q000379:methods; D009000:Monocytes / Q000166:cytology* / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D010010:Osteoclasts / Q000166:cytology* / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D000071681:Tartrate-Resistant Acid Phosphatase
D007527:Isoenzymes; D017886:Durapatite; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase