Adenoviral down-regulation of osteopontin inhibits human osteoclast differentiation in vitro.
Although osteopontin (OPN) is highly expressed in osteoclasts, OPN-deficient mice have a near-normal bone phenotype and its role in osteoclast differentiation and function remains uncertain. We used an adenoviral OPN-antisense vector (AdOPN-AS) to down-regulate OPN expression in a human in vitro osteoclastogenesis model employing CFU-GM precursors treated with RANKL and M-CSF. Cultures infected with AdOPN-AS showed reduced secretion of OPN compared to cultures infected with a control adenoviral vector expressing beta-galactosidase. Infection with AdOPN-AS co-incident with exposure to RANKL was associated with substantial (approximately 50%) inhibition of osteoclast formation with a concomitant reduction in dentine resorption. There was also a small reduction in the size of generated osteoclasts but no significant effect on the size of resorption pits/tracks nor on the amount of resorption per osteoclast. When the cultures were infected with AdOPN-AS after 4 days exposure to RANKL only minor effects on osteoclastogenesis were seen. Our data demonstrate that early down-regulation of OPN in vitro inhibits human osteoclastogenesis. Since mice totally lacking OPN do not have reduced osteoclast numbers our results imply the existence in vivo of an alternative molecular pathway(s).
Aitken
Cathy J
CJ
The University of Melbourne, Department of Clinical and Biomedical Sciences, Barwon Health, Geelong, Victoria 3220, Australia.
Hodge
Jason M
JM
Nicholson
Geoffrey C
GC
D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D015536:Down-Regulation; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D016376:Oligonucleotides, Antisense; D010010:Osteoclasts / Q000166:cytology / Q000502:physiology*; D053495:Osteopontin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D012795:Sialoglycoproteins / Q000235:genetics / Q000378:metabolism*
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D016376:Oligonucleotides, Antisense; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D053495:Osteopontin