title: Direct or indirect stimulation of adenosine A2A receptors enhances bone regeneration as well as bone morphogenetic protein-2.
abstract: Promoting bone regeneration and repair of bone defects is a need that has not been well met to date. We have previously found that adenosine, acting via A2A receptors (A2AR) promotes wound healing and inhibits inflammatory osteolysis and hypothesized that A2AR might be a novel target to promote bone regeneration. Therefore, we determined whether direct A2AR stimulation or increasing endogenous adenosine concentrations via purine transport blockade with dipyridamole regulates bone formation. We determined whether coverage of a 3 mm trephine defect in a mouse skull with a collagen scaffold soaked in saline, bone morphogenetic protein-2 (BMP-2; 200 ng), 1 μM CGS21680 (A2AR agonist, EC50 = 160 nM), or 1 μM dipyridamole (EC50 = 32 nM) promoted bone regeneration. Microcomputed tomography examination demonstrated that CGS21680 and dipyridamole markedly enhanced bone regeneration as well as BMP-2 8 wk after surgery (60 ± 2%, 79 ± 2%, and 75 ± 1% bone regeneration, respectively, vs. 32 ± 2% in control, P < 0.001). Blockade by a selective A2AR antagonist (ZM241385, 1 μM) or deletion of A2AR abrogated the effect of CGS21680 and dipyridamole on bone regeneration. Both CGS21680 and dipyridamole treatment increased alkaline phosphatase-positive osteoblasts and diminished tartrate resistance acid phosphatase-positive osteoclasts in the defects. In vivo imaging with a fluorescent dye for new bone formation revealed a strong fluorescent signal in treated animals that was equivalent to BMP-2. In conclusion, stimulation of A2AR by specific agonists or by increasing endogenous adenosine levels stimulates new bone formation as well as BMP-2 and represents a novel approach to stimulating bone regeneration.
authors.affiliation: Divisions of Translational Medicine and Rheumatology, Department of Medicine, New York University Langone Medical Center, New York, New York, USA.
authors.forename: Aránzazu
authors.initials: A
authors.lastname: Mediero
authors.affiliation: Divisions of Translational Medicine and Rheumatology, Department of Medicine, New York University Langone Medical Center, New York, New York, USA.
authors.forename: Tuere
authors.initials: T
authors.lastname: Wilder
authors.affiliation: Divisions of Translational Medicine and Rheumatology, Department of Medicine, New York University Langone Medical Center, New York, New York, USA.
authors.forename: Miguel
authors.initials: M
authors.lastname: Perez-Aso
authors.affiliation: Divisions of Translational Medicine and Rheumatology, Department of Medicine, New York University Langone Medical Center, New York, New York, USA bruce.cronstein@nyumc.org.
authors.forename: Bruce N
authors.initials: BN
authors.lastname: Cronstein
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D058908:Adenosine A2 Receptor Agonists / Q000494:pharmacology*; D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism*; D001861:Bone Regeneration / Q000187:drug effects* / Q000502:physiology*; D002452:Cell Count; D004176:Dipyridamole / Q000494:pharmacology; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010627:Phenethylamines / Q000494:pharmacology; D043705:Receptor, Adenosine A2A / Q000378:metabolism*
chemical_list: D058908:Adenosine A2 Receptor Agonists; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D010627:Phenethylamines; D043705:Receptor, Adenosine A2A; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D004176:Dipyridamole; D000241:Adenosine
keywords: CGS21680; bone formation; dipyridamole; osteoblast; osteoclast