The increased in vitro osteoclastogenesis in patients with rheumatoid arthritis is due to increased percentage of precursors and decreased apoptosis — The In Vitro Osteoclast Differentiation in Arthritis (IODA) study M. Durand a , G. Boire a , S.V. Komarova b , S.J. Dixon c , S.M. Sims c , R.E. Harrison d , N. Nabavi d , O. Maria b , M.F. Manolson e , M. Mizianty f , L. Kurgan f , A.J. de Brum-Fernandes a, ⁎ a Service de rhumatologie, Faculté de médecine, Université de Sherbrooke, 3001 12e Avenue Nord, local 3858, Sherbrooke, Quebec, Canada, J1H 5N4 b Faculty of Dentistry, room 2304, McGill University, 740 Dr. Penfield Ave, Montreal, Quebec, Canada, H3A 1A4 c Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada, N6A 5C1 d Department of Cell & Systems Biology, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, Canada, M1C 1A4 e Faculty of Dentistry, room 400, University of Toronto, 124 Edward Street, Toronto, Ontario, Canada, M5G 1G6 f Department of Electrical & Computer Engineering, ECERF building, University of Alberta, 9107 116 Street, Edmonton, Alberta, Canada, T6G 2V4 abstract article info Article history: Received 27 May 2010 Revised 6 October 2010 Accepted 11 October 2010 Available online 17 October 2010 Edited by: J. Aubin Keywords: Rheumatoid arthritis Bone Osteoclast Apoptosis CD14 + Osteoclastogenesis Biomarker Diagnostic model Increases in local and systemic bone resorption are hallmarks of rheumatoid arthritis (RA). Osteoclasts are implicated in these processes and their enhanced differentiation may contribute to bone destruction. We observed that in vitro osteoclastogenesis varies among healthy individuals and hypothesized that increased osteoclastogenesis could be a marker for the presence of RA. Our objective in the present study was to determine if in vitro osteoclastogenesis from peripheral blood mononuclear cells (PBMCs) was different in patients with RA compared to healthy controls and osteoarthritis (OA) patients. Expression of CD14 in PBMCs was quantified and PBMCs were incubated for 21 days in the presence of the osteoclastogenic cytokines M- CSF and RANKL. Differentiation on cortical bone slices permitted the analysis of bone resorption while apoptotic potential was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. In vitro osteoclastogenesis was higher in PBMCs from RA patients compared to controls, and a similar increase was observed in the percentage of osteoclast precursors in RA patients. Osteoclasts from RA patients showed lower apoptotic rates than osteoclasts from healthy controls. No difference was observed in bone resorption activity between RA patients and controls. Interestingly, the difference in osteoclast number and apoptosis rate allowed the implementation of an algorithm capable of distinguishing patients with RA from controls. In conclusion, our study shows that osteoclast differentiation from PBMCs is enhanced in patients with RA, and this difference can be explained by both a higher percentage of osteoclast precursors in the blood and by the reduced apoptotic potential of mature osteoclasts. © 2010 Elsevier Inc. All rights reserved. Introduction Rheumatoid arthritis (RA) is an inflammatory disease character- ized by joint destruction and cartilage loss. Periarticular bone erosions and generalized bone loss are hallmarks of RA and indicate that osteoclasts (OCs), cells specialized in bone resorption, are important for the pathogenesis of joint destruction. In RA joints, the presence of OCs and proinflammatory cytokines lead to pathological bone destruction, irreversible joint damage, pain and loss of function [1]. The participation of OCs in the genesis of joint destruction has been clearly demonstrated by both clinical and experimental data. In RA patients, treatment with Denosumab — a monoclonal antibody that binds RANKL and inhibits osteoclastogenesis and OC activity [2] — decreases the progression of bone erosions without affecting inflammation [3]. RANKL knock-out mice with inflammatory exper- imental arthritis are protected against periarticular bone erosion, confirming the importance of OCs in this process [4,5]. The intensity of either local or generalized bone resorption by OCs depends on the number of OCs formed, on the intrinsic activity of these cells as well as on their survival. Thus, factors inducing or facilitating osteoclastogenesis, or affecting activity or apoptosis may be important in the pathophysiology of bone destruction. OCs are derived from CD34-positive hematopoietic stem cells, which give rise Bone 48 (2011) 588–596 ⁎ Corresponding author. 3001 12e Avenue Nord, Fleurimont, Quebec, Canada, J1H 5N4. Fax: +1 819 564 5265. E-mail addresses: Marianne.Durand@USherbrooke.ca (M. Durand), Gilles.Boire@USherbrooke.ca (G. Boire), Svetlana.Komarova@mcgill.ca (S.V. Komarova), Jeff.Dixon@schulich.uwo.ca (S.J. Dixon), Stephen.Sims@schulich.uwo.ca (S.M. Sims), Harrison@utsc.utoronto.ca (R.E. Harrison), n_noushin@yahoo.com (N. Nabavi), Osama.Maria@mail.mcgill.ca (O. Maria), M.Manolson@utoronto.ca (M.F. Manolson), mizianty@ualberta.ca (M. Mizianty), lkurgan@ece.ualberta.ca (L. Kurgan), Artur.Fernandes@USherbrooke.ca (A.J. de Brum-Fernandes). 8756-3282/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.bone.2010.10.167 Contents lists available at ScienceDirect Bone journal homepage: www.elsevier.com/locate/bone