title: Effect of Tumor Necrosis Factor Inhibitor Therapy on Osteoclasts Precursors in Ankylosing Spondylitis.
abstract: BACKGROUND
  Ankylosing Spondylitis (AS) is characterized by excessive local bone formation and concomitant systemic bone loss. Tumor necrosis factor (TNF) plays a central role in the inflammation of axial skeleton and enthesis of AS patients. Despite reduction of inflammation and systemic bone loss, AS patients treated with TNF inhibitors (TNFi) have ongoing local bone formation. The aim of this study was to assess the effect of TNFi in the differentiation and activity of osteoclasts (OC) in AS patients.
  
  
  METHODS
  13 AS patients treated with TNFi were analyzed at baseline and after a minimum follow-up period of 6 months. 25 healthy donors were recruited as controls. Blood samples were collected to assess receptor activator of nuclear factor kappa-B ligand (RANKL) surface expression on circulating leukocytes and frequency and phenotype of monocyte subpopulations. Quantification of serum levels of bone turnover markers and cytokines, in vitro OC differentiation assay and qRT-PCR for OC specific genes were performed.
  
  
  RESULTS
  RANKL+ circulating lymphocytes (B and T cells) and IL-17A, IL-23 and TGF-β levels were decreased after TNFi treatment. We found no differences in the frequency of the different monocyte subpopulations, however, we found decreased expression of CCR2 and increased expression of CD62L after TNFi treatment. OC number was reduced in patients at baseline when compared to controls. OC specific gene expression was reduced in circulating OC precursors after TNFi treatment. However, when cultured in OC differentiating conditions, OC precursors from AS TNFi-treated patients showed increased activity as compared to baseline.
  
  
  CONCLUSIONS
  In AS patients, TNFi treatment reduces systemic pro osteoclastogenic stimuli. However, OC precursors from AS patients exposed to TNFi therapy have increased in vitro activity in response to osteoclastogenic stimuli.
authors.affiliation: Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon Academic Medical Centre, Lisboa, Portugal.
authors.forename: Inês P
authors.initials: IP
authors.lastname: Perpétuo
authors.affiliation: Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon Academic Medical Centre, Lisboa, Portugal.
authors.forename: Rita
authors.initials: R
authors.lastname: Raposeiro
authors.affiliation: Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon Academic Medical Centre, Lisboa, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Caetano-Lopes
authors.affiliation: Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon Academic Medical Centre, Lisboa, Portugal.|Rheumatology and bone metabolic diseases department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, EPE, Lisbon Academic Medical Centre, Lisboa, Portugal.
authors.forename: Elsa
authors.initials: E
authors.lastname: Vieira-Sousa
authors.affiliation: Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon Academic Medical Centre, Lisboa, Portugal.|Rheumatology and bone metabolic diseases department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, EPE, Lisbon Academic Medical Centre, Lisboa, Portugal.
authors.forename: Raquel
authors.initials: R
authors.lastname: Campanilho-Marques
authors.affiliation: Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon Academic Medical Centre, Lisboa, Portugal.|Rheumatology and bone metabolic diseases department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, EPE, Lisbon Academic Medical Centre, Lisboa, Portugal.
authors.forename: Cristina
authors.initials: C
authors.lastname: Ponte
authors.affiliation: Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon Academic Medical Centre, Lisboa, Portugal.|Rheumatology and bone metabolic diseases department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, EPE, Lisbon Academic Medical Centre, Lisboa, Portugal.
authors.forename: Helena
authors.initials: H
authors.lastname: Canhão
authors.affiliation: Musculoskeletal Diseases and Inflammation Research Group, Biomedicum Helsinki, Faculty of Medicine, Institute of Clinical Medicine, University of Helsinki, Helsinki, Finland.
authors.forename: Mari
authors.initials: M
authors.lastname: Ainola
authors.affiliation: Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon Academic Medical Centre, Lisboa, Portugal.|Rheumatology and bone metabolic diseases department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, EPE, Lisbon Academic Medical Centre, Lisboa, Portugal.
authors.forename: João E
authors.initials: JE
authors.lastname: Fonseca
mesh_terms: D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D015415:Biomarkers; D001862:Bone Resorption; D016207:Cytokines / Q000097:blood; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D016130:Immunophenotyping; D018836:Inflammation Mediators / Q000097:blood; D008297:Male; D008875:Middle Aged; D058990:Molecular Targeted Therapy; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism*; D010641:Phenotype; D053245:RANK Ligand / Q000378:metabolism; D013167:Spondylitis, Ankylosing / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D000079424:Tumor Necrosis Factor Inhibitors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D015415:Biomarkers; D016207:Cytokines; D018836:Inflammation Mediators; D053245:RANK Ligand; D000079424:Tumor Necrosis Factor Inhibitors