title: Comparative proteomic analysis of hypertrophic chondrocytes in osteoarthritis.
abstract: BACKGROUND
  Osteoarthritis (OA) is a multi-factorial disease leading progressively to loss of articular cartilage and subsequently to loss of joint function. While hypertrophy of chondrocytes is a physiological process implicated in the longitudinal growth of long bones, hypertrophy-like alterations in chondrocytes play a major role in OA. We performed a quantitative proteomic analysis in osteoarthritic and normal chondrocytes followed by functional analyses to investigate proteome changes and molecular pathways involved in OA pathogenesis.
  
  
  METHODS
  Chondrocytes were isolated from articular cartilage of ten patients with primary OA undergoing knee replacement surgery and six normal donors undergoing fracture repair surgery without history of joint disease and no OA clinical manifestations. We analyzed the proteome of chondrocytes using high resolution mass spectrometry and quantified it by label-free quantification and western blot analysis. We also used WebGestalt, a web-based enrichment tool for the functional annotation and pathway analysis of the differentially synthesized proteins, using the Wikipathways database. ClueGO, a Cytoscape plug-in, is also used to compare groups of proteins and to visualize the functionally organized Gene Ontology (GO) terms and pathways in the form of dynamical network structures.
  
  
  RESULTS
  The proteomic analysis led to the identification of a total of ~2400 proteins. 269 of them showed differential synthesis levels between the two groups. Using functional annotation, we found that proteins belonging to pathways associated with regulation of the actin cytoskeleton, EGF/EGFR, TGF-β, MAPK signaling, integrin-mediated cell adhesion, and lipid metabolism were significantly enriched in the OA samples (p ≤10(-5)). We also observed that the proteins GSTP1, PLS3, MYOF, HSD17B12, PRDX2, APCS, PLA2G2A SERPINH1/HSP47 and MVP, show distinct synthesis levels, characteristic for OA or control chondrocytes.
  
  
  CONCLUSIONS
  In this study we compared the quantitative changes in proteins synthesized in osteoarthritic compared to normal chondrocytes. We identified several pathways and proteins to be associated with OA chondrocytes. This study provides evidence for further testing on the molecular mechanism of the disease and also propose proteins as candidate markers of OA chondrocyte phenotype.
authors.affiliation: Institute of Molecular Biology and Biotechnology - FoRTH, Iraklio, Greece ; Department of Microbiology and Immunology, Rega Institute for Medical Research, KULeuven, Leuven, Belgium.
authors.forename: Konstantinos C
authors.initials: KC
authors.lastname: Tsolis
authors.affiliation: School of Electronic and Computer Engineering, Technical Univ. of Crete, Chania, Greece.
authors.forename: Ekaterini S
authors.initials: ES
authors.lastname: Bei
authors.affiliation: Department of Biology, University of Thessaly, Faculty of Medicine, Larissa, Greece ; Institute for Research & Technology-Thessaly/Centre for Research & Technology-Hellas (CE.R.T.H), Larissa, Greece.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Papathanasiou
authors.affiliation: Department of Biology, University of Thessaly, Faculty of Medicine, Larissa, Greece ; Institute for Research & Technology-Thessaly/Centre for Research & Technology-Hellas (CE.R.T.H), Larissa, Greece.
authors.forename: Fotini
authors.initials: F
authors.lastname: Kostopoulou
authors.affiliation: Institute for Research & Technology-Thessaly/Centre for Research & Technology-Hellas (CE.R.T.H), Larissa, Greece.
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Gkretsi
authors.affiliation: School of Electronic and Computer Engineering, Technical Univ. of Crete, Chania, Greece.
authors.forename: Kalliopi
authors.initials: K
authors.lastname: Kalantzaki
authors.affiliation: Department of Orthopedics, University of Thessaly, Faculty of Medicine, Larissa, Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Malizos
authors.affiliation: School of Electronic and Computer Engineering, Technical Univ. of Crete, Chania, Greece.
authors.forename: Michalis
authors.initials: M
authors.lastname: Zervakis
authors.affiliation: Department of Biology, University of Thessaly, Faculty of Medicine, Larissa, Greece ; Institute for Research & Technology-Thessaly/Centre for Research & Technology-Hellas (CE.R.T.H), Larissa, Greece.
authors.forename: Aspasia
authors.initials: A
authors.lastname: Tsezou
authors.affiliation: Institute of Molecular Biology and Biotechnology - FoRTH, Iraklio, Greece ; Department of Microbiology and Immunology, Rega Institute for Medical Research, KULeuven, Leuven, Belgium.
authors.forename: Anastassios
authors.initials: A
authors.lastname: Economou
keywords: Cartilage; Chondrocytes; GSTP1; Mass spectrometry; Osteoarthritis; PLS3; Pathway analysis; Proteomics