title: New insights into the pathogenesis of glucocorticoid-induced avascular necrosis: microarray analysis of gene expression in a rat model.
abstract: BACKGROUND
  Avascular necrosis of the femoral head (ANFH) occurs variably after exposure to corticosteroids. Microvascular thrombosis is a common pathological finding. Since systemic thrombophilia is only weakly linked with ANFH, we propose that microvascular vessel pathology may be more related to local endothelial dysfunction and femoral head apoptosis. Corticosteroid effects on the endothelium and resultant apoptosis have been reported. We hypothesize that corticosteroids contribute to a differential gene expression in the femoral head in rats with early ANFH.
  
  
  METHODS
  Besides bone marrow necrosis, which is a common sign in ANFH and reported in the early stages, we include the presence of apoptosis in this study as a criterion for diagnosing early disease. Forty Wistar Kyoto (WKY) rats were randomized to either a corticosteroid-treated group or an age-matched control group for six months. After sacrifice, the femoral heads were examined for ANFH. Total mRNA was extracted from femoral heads. Affymetrix exon array (Santa Clara, CA, USA) was performed on 15 selected RNA samples. Validation methods included RT-PCR and immunohistochemistry (IHC).
  
  
  RESULTS
  Although rat exon array demonstrated a significant upregulation of 51 genes (corticosteroid(+)/ANFH(+) VS control), alpha-2-macroglobulin (A2M) gene was particularly over-expressed. Results were validated by RT-PCR and IHC. Importantly, A2M is known to share vascular, osteogenic and cartilage functions relevant for ANFH.
  
  
  CONCLUSIONS
  The findings suggest that corticosteroid-induced ANFH in rats might be mediated by A2M. Investigation of A2M as a potential marker, and a treatment target, for early ANFH should be carried out.
authors.affiliation: Department of Human Genetics, McGill University Health Center (MUHC), 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada.
authors.forename: Mohammad Amin
authors.initials: MA
authors.lastname: Kerachian
authors.forename: Denis
authors.initials: D
authors.lastname: Cournoyer
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Harvey
authors.forename: Terry Y
authors.initials: TY
authors.lastname: Chow
authors.forename: Louis R
authors.initials: LR
authors.lastname: Bégin
authors.forename: Ayoub
authors.initials: A
authors.lastname: Nahal
authors.forename: Chantal
authors.initials: C
authors.lastname: Séguin
mesh_terms: D000305:Adrenal Cortex Hormones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015415:Biomarkers / Q000378:metabolism; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D024043:Collagen Type II / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D005271:Femur Head Necrosis / Q000139:chemically induced* / Q000235:genetics* / Q000378:metabolism; D005938:Glucocorticoids / Q000009:adverse effects*; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000511:alpha-Macroglobulins / Q000378:metabolism
chemical_list: D000305:Adrenal Cortex Hormones; D015415:Biomarkers; C511513:COL2A1 protein, rat; D024043:Collagen Type II; D005938:Glucocorticoids; C099322:Mia protein, rat; D011506:Proteins; D000511:alpha-Macroglobulins