Session Information
Session Type: Abstract Submissions (ACR)
Background/Purpose: Communication between OC and OB is critical for maintenance of bone homeostasis; both OC and OB release regulatory messengers. Among these signaling molecules are semaphorin 3A and 4D (sema3A and sema4D). During inflammatory osteolysis bone destruction is regulated by RANKL, M-CSF, TNF, among others. A2AR ligation diminishes osteolysis and expression of RANKL, M-CSF and TNF. We therefore asked whether A2AR activation modulates OB-OC crosstalk by regulating sema3A and sema4D or their receptors PlexinA1/Neuropilin1 and PlexinB1, respectively, in a model of inflammatory osteolysis.
Methods: 1cm midline sagittal incisions were made over calvaria in 6-8 wk old C57Bl/6 mice. Calvaria were exposed to 20µl of PBS containing 3mg of UHMWPE followed by daily injections of either vehicle or CGS21680 (A2AR agonist) 1µM (n=4 each) for 14 days. XenoLight Rediject Bone Probe was injected IV and fluorescence of calvaria measured (IVIS) to assay bone formation. Sema3A/PlexinA1/Neuropilin1 and Sema4D/PlexinB1 expression were studied by RT-PCR and Western Blot in primary bone marrow-derived OC and OB in the presence/absence of CGS21680 and ZM241385 (A2AR antagonist) 1µM each.
Results: XenoLight imaging revealed a 52.5±6% reduction in bone formation after exposure to UHMWPE (p<0.001, n=5) and CGS21680 completely reversed this effect (11±5% increased compare to control, p=NS, n=5). In UHMWPE-exposed calvaria there was a decreased number of cells expressing Sema3A and PlexinA1 but not Neuropilin1, effects largely reversed by CGS21680. In contrast, Sema4D/PlexinB1 expressing cells, primarily macrophages and OC, were increased in UHMWPE-exposed calvaria and CGS21680 reversed these changes as well. In marrow cell cultures RANKL induced a 2.5±0.1 fold increase in Sema4D mRNA (p<0.001,n=4) which was blocked by CGS21680 (p<0.001,n=4). In contrast, PlexinA1 mRNA was enhanced by CGS21680 (9.3±0.7 fold increase vs 4.9±0.6 for RANKL, p<0.001,n=4) but Neuropilin1 mRNA was unchanged. Sema3A mRNA increased 3.5±0.5 fold during OB differentiation and CGS21680 enhanced this to 8.7±0.2 fold, p<0.001,n=3); PlexinB1 mRNA was increased 2 fold during OB differentiation and was not altered by CGS21680 exposure. Similar changes were observed in protein expression and secretion.
Conclusion: UHMWPE-induced inflammatory osteolysis involves both bone destruction and reduction of new bone formation. A2AR stimulation diminishes secretion of inflammatory mediators and also regulates expression of AGP that likely contribute to inflammatory osteolysis and reduction in bone production.
Disclosure:
A. Mediero,
Filed a patent on use of adenosine A2AR agonists to prevent prosthesis loosening (pending). ,
9;
T. Wilder,
None;
M. Perez-Aso,
None;
B. N. Cronstein,
Canfite Pharma,
1,
NIH, Gilead, Takeda, AstraZeneca,
2,
NYU School of Medicine,
3,
Merck-SeronoBristol-Myers Squibb, Novartis, CanFite Biopharmaceuticals, Cypress Laboratories, Regeneron (Westat, DSMB), Endocyte, Protalex, Allos, Inc., Savient, Gismo Therapeutics, Antares Pharmaceutical, Medivector,
5,
Multiple patents on adenosine receptors and bone metabolism, pharmacology,
9.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/adenosine-a2a-receptor-a2ar-diminishes-wear-particle-uhmwpe-mediated-osteolysis-increases-bone-formation-and-regulates-expression-of-axonal-guidance-proteins-agp-by-macrophages-osteoclasts-oc/