title: Expression profile of osteoprotegerin, RANK and RANKL genes in the femoral head of patients with avascular necrosis.
abstract: BACKGROUND
  Femoral head avascular necrosis (AVN) is a recalcitrant disease of the hip that leads to joint destruction. Osteoprotegerin (OPG), Receptor Activator of Nuclear Factor kappa-B (RANK) and RANK ligand (RANKL) regulate the balance between osteoclasts-osteoblasts. The expression of these genes affects the maturation and function of osteoblasts-osteoclasts and bone remodeling. In this study, we investigated the molecular pathways leading to AVN by studying the expression profile of OPG, RANK and RANKL genes.
  
  
  METHODS
  Quantitative Real Time-PCR was performed for evaluation of OPG, RANK and RANKL expression. Analysis was based on parallel evaluation of mRNA and protein levels in normal/necrotic sites of 42 osteonecrotic femoral heads (FHs). OPG and RANKL protein levels were estimated by western blotting.
  
  
  RESULTS
  The OPG mRNA levels were higher (insignificantly) in the necrotic than the normal site (p > 0.05). Although the expression of RANK and RANKL was significantly lower than OPG in both sites, RANK and RANKL mRNA levels were higher in the necrotic part than the normal (p < 0.05). Protein levels of OPG and RANKL showed no remarkable divergence.
  
  
  CONCLUSIONS
  Our results indicate that differential expression mechanisms for OPG, RANK and RANKL that could play an important role in the progress of bone remodeling in the necrotic area, disturbing bone homeostasis. This finding may have an effect on the resulting bone destruction and the subsequent collapse of the hip joint.
authors.affiliation: Laboratory of Medical Genetics and Cytogenetics, Faculty of Medicine, University of Thessalia, Larissa, Greece.
authors.forename: Stavroula
authors.initials: S
authors.lastname: Samara
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, University of Thessalia, Larissa, Greece.
authors.forename: Zoe
authors.initials: Z
authors.lastname: Dailiana
authors.affiliation: Laboratory of Medical Genetics and Cytogenetics, Faculty of Medicine, University of Thessalia, Larissa, Greece.
authors.forename: Christos
authors.initials: C
authors.lastname: Chassanidis
authors.affiliation: Department of Genetics & Biotechnology, Faculty of Biology, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Theodora
authors.initials: T
authors.lastname: Koromila
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, University of Thessalia, Larissa, Greece.
authors.forename: Loukia
authors.initials: L
authors.lastname: Papatheodorou
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, University of Thessalia, Larissa, Greece; Department of Biomedical Research and Technology, Center for Research and Technology, Thessaly (CERETETH), Larissa, Greece.
authors.forename: Konstantinos N
authors.initials: KN
authors.lastname: Malizos
authors.affiliation: Department of Genetics & Biotechnology, Faculty of Biology, National and Kapodistrian University of Athens, Athens, Greece. Electronic address: pankollia@biol.uoa.gr.
authors.forename: Panagoula
authors.initials: P
authors.lastname: Kollia
mesh_terms: D000328:Adult; D000368:Aged; D015153:Blotting, Western; D005260:Female; D005271:Femur Head Necrosis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D053244:Osteoprotegerin / Q000235:genetics* / Q000378:metabolism; D053245:RANK Ligand / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055815:Young Adult
chemical_list: D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human
keywords: Avascular necrosis of the bone; OPG; Osteoblasts; Osteoclasts; RANK; RANKL