title: Expression of macrophage elastase (MMP12) in rat tail intervertebral disc and growth plate after asymmetric loading.
abstract: OBJECTIVE
  The aim of this study was to examine whether asymmetric loading influences macrophage elastase (MMP12) expression in different parts of a rat tail intervertebral disc and growth plate and if MMP12 expression is correlated with the severity of the deformity.
  
  
  METHODS
  A wedge deformity between the ninth and tenth tail vertebrae was produced with an Ilizarov-type mini external fixator in 45 female Wistar rats, matched for their age and weight. Three groups were created according to the degree of deformity (10°, 30° and 50°). A total of 30 discs and vertebrae were evaluated immunohistochemically for immunolocalisation of MMP12 expression, and 15 discs were analysed by western blot and zymography in order to detect pro- and active MMP12.
  
  
  RESULTS
  No MMP12 expression was detected in the nucleus pulposus. Expression of MMP12 in the annulus progressively increased from group I to groups II and III, mainly at the concave side. Many growth plate chondrocytes expressed MMP12 in the control group, less in group I and rare in groups II and III. Changes in cell phenotype and reduction of cell number were observed, together with disorganisation of matrix microstructure similar to disc degeneration. ProMMP12 was detected at the area of 54 kDa and active MMP12 at 22 kDa.
  
  
  CONCLUSIONS
  Expression of MMP12 after application of asymmetric loading in a rat tail increased in the intervertebral disc but decreased in the growth plate and correlated with the degree of the deformity and the side of the wedged disc. Cite this article: Bone Joint Res 2014;3:273-9.
authors.affiliation: University of Athens, Third Department of Orthopaedic Surgery, KAT Hospital and Medical School, Athens, Greece.
authors.forename: E S
authors.initials: ES
authors.lastname: Vasiliadis
authors.affiliation: University of Patras, Laboratory of Molecular Pharmacology, School of Health Sciences, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Kaspiris
authors.affiliation: Tzanio General Hospital, Department of Trauma and Orthopaedics, Piraeus, Greece.
authors.forename: T B
authors.initials: TB
authors.lastname: Grivas
authors.affiliation: University of Athens, Department of Osteopathology, Laboratory for Research of the Musculoskeletal System, School of Medicine, Athens, Greece.
authors.forename: L
authors.initials: L
authors.lastname: Khaldi
authors.affiliation: University of Patras, Laboratory of Molecular Pharmacology, School of Health Sciences, Greece.
authors.forename: M
authors.initials: M
authors.lastname: Lamprou
authors.affiliation: University of Athens, Third Department of Orthopaedic Surgery, KAT Hospital and Medical School, Athens, Greece.
authors.forename: S G
authors.initials: SG
authors.lastname: Pneumaticos
authors.affiliation: University of Athens, Third Department of Orthopaedic Surgery, KAT Hospital and Medical School, Athens, Greece.
authors.forename: K
authors.initials: K
authors.lastname: Nikolopoulos
authors.affiliation: University of Athens, Third Department of Orthopaedic Surgery, KAT Hospital and Medical School, Athens, Greece.
authors.forename: D S
authors.initials: DS
authors.lastname: Korres
authors.affiliation: University of Patras, Laboratory of Molecular Pharmacology, School of Health Sciences, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Papadimitriou
keywords: Asymmetric loading; Degeneration; Growth plate; MMP12; intervertebral disc