title: Arthritis induces early bone high turnover, structural degradation and mechanical weakness.
abstract: BACKGROUND
  We have previously found in the chronic SKG mouse model of arthritis that long standing (5 and 8 months) inflammation directly leads to high collagen bone turnover, disorganization of the collagen network, disturbed bone microstructure and degradation of bone biomechanical properties. The main goal of the present work was to study the effects of the first days of the inflammatory process on the microarchitecture and mechanical properties of bone.
  
  
  METHODS
  Twenty eight Wistar adjuvant-induced arthritis (AIA) rats were monitored during 22 days after disease induction for the inflammatory score, ankle perimeter and body weight. Healthy non-arthritic rats were used as controls for compar-ison. After 22 days of disease progression rats were sacrificed and bone samples were collected for histomorphometrical, energy dispersive X-ray spectroscopical analysis and 3-point bending. Blood samples were also collected for bone turnover markers.
  
  
  RESULTS
  AIA rats had an increased bone turnover (as inferred from increased P1NP and CTX1, p = 0.0010 and p = 0.0002, respectively) and this was paralleled by a decreased mineral content (calcium p = 0.0046 and phos-phorus p = 0.0046). Histomorphometry showed a lower trabecular thickness (p = 0.0002) and bone volume (p = 0.0003) and higher trabecular sepa-ration (p = 0.0009) in the arthritic group as compared with controls. In addition, bone mechanical tests showed evidence of fragility as depicted by diminished values of yield stress and ultimate fracture point (p = 0.0061 and p = 0.0279, re-spectively) in the arthritic group.
  
  
  CONCLUSIONS
  We have shown in an AIA rat model that arthritis induc-es early bone high turnover, structural degradation, mineral loss and mechanical weak-ness.
authors.affiliation: Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal.
authors.forename: Bruno
authors.initials: B
authors.lastname: Vidal
authors.affiliation: Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal.
authors.forename: Rita
authors.initials: R
authors.lastname: Cascão
authors.affiliation: Instituto de Ciência e Engenharia de Materiais e Superfícies, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal.
authors.forename: Ana Catarina
authors.initials: AC
authors.lastname: Vale
authors.affiliation: Instituto Superior de Ciências da Saúde Egas Moniz-Campus Universitário, Quinta da Granja, Caparica, Portugal.
authors.forename: Inês
authors.initials: I
authors.lastname: Cavaleiro
authors.affiliation: Instituto de Ciência e Engenharia de Materiais e Superfícies, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal; Departamento de Engenharia Mecânica, Instituto Superior Técnico, UL, Lisbon, Portugal.
authors.forename: Maria Fátima
authors.initials: MF
authors.lastname: Vaz
authors.affiliation: Instituto Superior de Ciências da Saúde Egas Moniz-Campus Universitário, Quinta da Granja, Caparica, Portugal.
authors.forename: José Américo Almeida
authors.initials: JA
authors.lastname: Brito
authors.affiliation: Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal; Rheumatology Department, Lisbon Academic Medical Centre, Lisbon, Portugal.
authors.forename: Helena
authors.initials: H
authors.lastname: Canhão
authors.affiliation: Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal; Rheumatology Department, Lisbon Academic Medical Centre, Lisbon, Portugal.
authors.forename: João Eurico
authors.initials: JE
authors.lastname: Fonseca
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000473:pathology* / Q000503:physiopathology*; D015415:Biomarkers; D001696:Biomechanical Phenomena; D015519:Bone Density; D016723:Bone Remodeling; D005260:Female; D008159:Lumbar Vertebrae / Q000473:pathology / Q000503:physiopathology; D055595:Mechanical Phenomena; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015415:Biomarkers