title: Macrophage-specific metalloelastase (MMP-12) immunoexpression in the osteochondral unit in osteoarthritis correlates with BMI and disease severity.
abstract: BACKGROUND
  Metalloproteinase 12 (MMP-12) is induced in chondrocytes during fetal development and malignant transformation.
  
  
  OBJECTIVE
  The aim of our study is to examine the expression of MMP-12 in the cartilage and the subchondral bone of patients with osteoarthritis (OA) and to correlate its expression with disease severity and anthropometric characteristics.
  
  
  METHODS
  Overall, 60 sections from 20 patients with idiopathic OA, were examined for the immunolocalization of MMP-12. As controls, we used the femoral heads of 4 patients treated with seniarthroplasty after fracture. Demographic characteristics and Body Mass Index (BMI) were calculated for all subjects.
  
  
  RESULTS
  Specimens were divided into four groups based on the Mankin histological severity score. The immunohistochemical study showed MMP-12 expression in the cartilage and subchonral bone of OA patients, while there was no expression in normal controls. At the moderate OA changes (Mankin score: 6-7), MMP-12 was detected mainly at the matrix of fibrocartilage tissue. During disease progression, MMP-12 was expressed at the sides of the cartilage and bone erosion and in the bone cysts. Furthermore, it was traced in the osteocytes of the subchondral bone. Osteoblast-like cells and bone lining cells express MMP-12 during the stage of severe OA (Mankin: ≥8). Osteoclasts expressing MMP-12 were also detected in the group of severe OA. Interestingly, MMP-12 expression was positively correlated with the age and the BMI of OA patients.
  
  
  CONCLUSIONS
  The increased expression of MMP-12 in the bone-cartilage unit of OA patients suggests a possible role in OA pathogenesis and progression.
  
  
  METHODS
  III, prospective comparative study.
authors.affiliation: Department of Trauma and Orthopaedics, Thriasio General Hospital of Attica - NHS, G. Gennimata av., Athens, Magoula 19600, Greece; Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, Attica, Greece; Laboratory of Molecular Pharmacology, School of Health Sciences, University of Patras, Greece. Electronic address: angkaspiris@hotmail.com.
authors.forename: Angelos
authors.initials: A
authors.lastname: Kaspiris
authors.affiliation: Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, Attica, Greece.
authors.forename: Lubna
authors.initials: L
authors.lastname: Khaldi
authors.affiliation: Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, Attica, Greece.
authors.forename: Efstathios
authors.initials: E
authors.lastname: Chronopoulos
authors.affiliation: Department of Trauma and Orthopaedics, Thriasio General Hospital of Attica - NHS, G. Gennimata av., Athens, Magoula 19600, Greece.
authors.forename: Elias
authors.initials: E
authors.lastname: Vasiliadis
authors.affiliation: Department of Trauma and Orthopaedics, Tzanio General Hospital of Piraeus - NHS, Piraeus 18536, Attica, Greece.
authors.forename: Theodoros B
authors.initials: TB
authors.lastname: Grivas
authors.affiliation: Department of Trauma and Orthopaedics, Thriasio General Hospital of Attica - NHS, G. Gennimata av., Athens, Magoula 19600, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Kouvaras
authors.affiliation: Department of Trauma and Orthopaedics, Thriasio General Hospital of Attica - NHS, G. Gennimata av., Athens, Magoula 19600, Greece.
authors.forename: Spyridon
authors.initials: S
authors.lastname: Dagkas
authors.affiliation: Laboratory of Molecular Pharmacology, School of Health Sciences, University of Patras, Greece.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Papadimitriou
keywords: BMI; Immunohistochemistry; MMP-12; Osteoarthritis