Serum RANKL levels associate with anti- citrullinated protein antibodies in early untreated rheumatoid arthritis and are modulated following methotrexate.
BACKGROUND
Receptor activator of nuclear factor kappa B ligand (RANKL) is a key regulator of bone metabolism. Anti-citrullinated protein antibodies (ACPA) have been suggested to cause bone destruction by osteoclast activation. We investigated the relationship between RANKL and ACPA in patients with early untreated rheumatoid arthritis (RA).


METHODS
Patients with newly diagnosed untreated RA (n = 183) were analyzed at baseline and 3 months after initiating methotrexate (MTX) treatment. Serum RANKL (total RANKL), ACPA (anti-CCP2) and ACPA specificities (anti-citrullinated (cit)-vimentin, anti-cit-enolase and anti-cit-fibrinogen) were determined by enzyme-linked immunosorbent assay (ELISA). Synovial RANKL expression was evaluated by immunohistochemistry in a small group of patients (n = 15). The relationship between anti-cit-vim antibodies and bone destruction was further validated in 1116 RA patients included in the EIRA cohort. Pearson's chi-square test, Wilcoxon rank sum test, Wilcoxon signed rank test and linear regression models were used.


RESULTS
Serum RANKL concentration was significantly higher (p <0.05) in ACPA-positive (median: 689 pmol/L, IQR 342-1253) compared with ACPA-negative (median: 159 pmol/L, IQR 96-243) patients and this difference was also seen for synovial RANKL expression. Serum RANKL associated with ACPA (p <0.05) and bone erosions in rheumatoid factor (RF)-negative patients (n = 59). Among ACPA specificites, anti-cit-vimentin (amino acids 60-75) was associated with higher RANKL concentration and higher prevalence of bone erosion (p <0.05). Significant reductions in both serum RANKL and ACPA levels were observed after 3 months of MTX treatment (p <0.05).


CONCLUSIONS
RANKL was elevated in ACPA-positive and in anti-cit-vimentin-positive patients with early untreated RA and associated with bone erosions. These findings give further support for an early direct pathogenic link between ACPA and bone destruction in RA.
Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, L8:04 CMM, 171 76, Stockholm, Sweden. aase.hensvold@ki.se.
Aase Haj
AH
Hensvold
Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, L8:04 CMM, 171 76, Stockholm, Sweden. vijay.joshua.balasingh@ki.se.
Vijay
V
Joshua
Crescendo Bioscience, 341 Oyster Point Boulevard, South San Francisco, CA, 94080, USA. wli@crescendobio.com.
Wanying
W
Li
Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, L8:04 CMM, 171 76, Stockholm, Sweden. larkinmf@tcd.ie.
Michaela
M
Larkin
Crescendo Bioscience, 341 Oyster Point Boulevard, South San Francisco, CA, 94080, USA. FQureshi@crescendobio.com.
Ferhan
F
Qureshi
Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, L8:04 CMM, 171 76, Stockholm, Sweden. Lena.Israelsson@ki.se.
Lena
L
Israelsson
Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, L8:04 CMM, 171 76, Stockholm, Sweden. leonid.padyukov@ki.se.
Leonid
L
Padyukov
Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, L8:04 CMM, 171 76, Stockholm, Sweden. karin.lundberg@ki.se.
Karin
K
Lundberg
Crescendo Bioscience, 341 Oyster Point Boulevard, South San Francisco, CA, 94080, USA. ndefranoux@crescendobio.com.
Nadine
N
Defranoux
Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, L8:04 CMM, 171 76, Stockholm, Sweden. saedis.saevarsdottir@ki.se.|Institute of Environmental Medicine, Karolinska Institutet, Solnavägen 1, 171 77, Stockholm, Sweden. saedis.saevarsdottir@ki.se.
Saedis
S
Saevarsdottir
Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, L8:04 CMM, 171 76, Stockholm, Sweden. anca.catrina@ki.se.
Anca Irinel
AI
Catrina
D000328:Adult; D000368:Aged; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000188:drug therapy* / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D002956:Citrulline / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D016014:Linear Models; D008297:Male; D008727:Methotrexate / Q000627:therapeutic use*; D008875:Middle Aged; D010751:Phosphopyruvate Hydratase / Q000276:immunology; D053245:RANK Ligand / Q000097:blood / Q000276:immunology* / Q000378:metabolism; D013583:Synovial Membrane / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D013997:Time Factors; D014746:Vimentin / Q000276:immunology
D018501:Antirheumatic Agents; D001323:Autoantibodies; D053245:RANK Ligand; C505688:TNFSF11 protein, human; D014746:Vimentin; D002956:Citrulline; D010751:Phosphopyruvate Hydratase; D008727:Methotrexate