Background: Sarcopenia, characterized by muscle loss and a decline in physical activity, is a common condition in rheumatoid arthritis (RA) patients. Muscle loss in RA is independent of the inflammatory state, with patients in remission still exhibiting a sarcopenic footprint that current treatments do not seem to manage. Adenosine and ATP levels are crucial in regulating myogenesis, muscle anabolism/catabolism, and cellular senescence. Previously, we have demonstrated that dipyridamole increases extracellular adenosine and stimulates adenosine A2B receptor preventing alterations in muscle myogenesis [1]. However, the specific interplay between the purinergic system and sarcopenia in RA remains an area warranting in-depth exploration.

Objectives: This study aims to investigate the potential of dipyridamole as therapeutic treatment for sarcopenia in experimental RA.

Methods: RA was induced in C57BL/6 mice via K/BxN serum transfer, and treatment with dipyridamole was scheduled in two different patterns: Treatment starting at the day of RA induction (preventive) or starting 7 days after disease induction (at the peak of inflammation, therapeutically). It was daily administered (25 mg/Kg) via IP injection. Body composition by DXA and motor activity tests were done before and after RA induction (day 13 and day 28). Mice were sacrificed at day 28, when paw macroscopic inflammation was no longer detectable. Inflammatory cytokines array were performed on serum and muscle. Histological analysis of tibialis anterior (TA) muscle was conducted via H&E, picrosirius red and ATPase staining. Protein expression of key markers involved in myogenesis, the purinergic system, and cellular senescence were assessed. The nucleotide content of gastrocnemius (GA) muscle was analyzed by high-performance liquid chromatography (HPLC). ELISA of C-reactive protein in serum, creatin kinase and cAMP in muscle were performed. Additionally, 3D culture of myobundles derived from C2C12 myoblasts were used to validate the anabolic response of dipyridamole (1 µM) in muscle. C2C12 cells were also silenced for A2BR expression in myoblast and myotube state and treated with dipyridamole (1µM), and key proteins were analyzed.

Results: Serum transfer (RA mice) induced an increase in joint inflammation that was maximal 2 wk after injection that was both prevented and reverted by dipyridamole. At day 28, untreated RA mice exhibited no detectable inflammatory cytokines in either serum or muscle. However, despite the resolution of inflammation, these RA mice developed progressive weight and muscle loss, physical activity decline, and increased muscle senescence (high expression of p21 and p16), atrophy (high expression of myostatin , Murf1 and Atrogin1 ), and increase in Type II muscle fibers, fibrosis and presence of myonecrosis (IgG positive staining inside the myofibers of TA). Furthermore, RA mice showed reduced adenosine levels and a decrease in the expression of adenosine A2A and A2B receptors in the RA muscle tissue. Dipyridamole treatment (both preventive or therapeutically) prevented the muscle weight and body weight loss, counteracting physical activity decline in RA mice, as well as atrophy, senescence, fibrosis and mionecrosis. Dipyridamole treatment stimulated muscle adenosine levels and A2A/A2B receptors expression, which in turn activated the cAMP/AMPK pathway. Additionally, the 3D myobundle model corroborated the in vivo findings with reduction of senescence and atrophy markers by dipyridamole. Silencing of adenosine A2B receptor in C2C12 cells blocked the therapeutic effect of dipyridamole.

Conclusion: Dipyridamole demonstrates potential as a therapeutic agent for counteracting sarcopenia in RA by modulating adenosine levels and activating A2BR signaling, offering a promising approach to managing the sarcopenic footprint in these patients.

REFERENCES: [1] Marco-Bonilla M, Herencia R, Fresnadillo M, Huete-Toral F, Carracedo G, Largo R, et al. Dipyridamole activates adenosine A2B receptor and AMPK/cAMP signaling and promotes myogenic differentiation of myoblastic C2C12 cells. Front Pharmacol 2023;14:1247664.

Acknowledgements: This study was performed in the Bone and Joint Research Unit of the IIS-Fundación Jiménez Díaz. This work was supported by grants from Instituto de Salud Carlos III through the “Miguel Servet” program (CP15/00053, CPII20/00017) co-funded by Union Europea, and a research grant from the Spanish Instituto de Salud Carlos III (PI19/00744, PI22/00347) and RICOR-RD21/0002/0025.

Disclosure of Interests: None declared.

© The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.