title: Apoptosis associated with Wnt/β-catenin pathway leads to steroid-induced avascular necrosis of femoral head.
abstract: BACKGROUND
  The objective of the current study was to establish a rat model to investigate apoptosis in steroid-induced femoral head osteonecrosis occurring via the Wnt/β-catenin pathway.
  
  
  METHODS
  Male Sprague-Dawley (SD) rats were randomly divided into a control group (group A), model group (group B) and sFRP1 group (group C), each consisting of 24 rats, and the rats were intravenously injected with LPS (10 μg/kg body weight). After 24 h, three injections of MPS (20 mg/kg body weight) were administered intramuscularly at 24-h intervals. The rats in group C were injected intramuscularly with 1 μg/kg sFRP1 protein per day for 30 days, beginning at the time of the first MPS administration. The group A rats were fed and housed under identical conditions but received saline injection. All animals were sacrificed at weeks 2, 4 and 8 from the first MPS injection. Histopathological staining was preformed to evaluated osteonecrosis. Apoptosis was detected via quantitative terminal deoxynucleotidyl transferase (TdT) deoxyuridine triphosphate nick-end labelling (TUNEL) staining, caspase-3 activity assay, and detection of Bcl-2 and Bax protein expression by immunohistochemistry and Western blotting. Wnt/β-catenin pathway signalling molecules, including activated β-catenin and c-Myc, were detected by immunohistochemistry and Western blotting.
  
  
  RESULTS
  Typical osteonecrosis was observed in groups B and C. Apoptosis gradually increased with increasing time in both groups B and C. More severe osteonecrosis and apoptosis were observed in group C compared with group B. The expression levels of caspase-3 and Bax were higher while that of Bcl-2 was lower in group C compared with group B. The expression levels of activated β-catenin and c-Myc gradually decreased with increasing time in both groups B and C, and they were lower in group C compared with group B.
  
  
  CONCLUSIONS
  The Wnt/β-catenin pathway is involved in the pathogenesis of early stage SANFH, as we have demonstrated in an SANFH rat model, and it may act through the regulation of c-Myc, which affects the cell cycle and cell apoptosis.
authors.affiliation: The First Department of Orthopaedics, the Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, No.157 Xiwu Road, Xi'an, Shaanxi Province, 710004, P. R. China. osteozhang@163.com.
authors.forename: Chen
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Orthopaedics, Chongqing Medical University, Chongqing, 400010, P. R. China. zouyulong@stu.xjtu.edu.cn.
authors.forename: Yu-Long
authors.initials: YL
authors.lastname: Zou
authors.affiliation: The First Department of Orthopaedics, the Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, No.157 Xiwu Road, Xi'an, Shaanxi Province, 710004, P. R. China. xiaobao0579@163.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
authors.affiliation: The First Department of Orthopaedics, the Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, No.157 Xiwu Road, Xi'an, Shaanxi Province, 710004, P. R. China. dangxiaoqian@vip.163.com.
authors.forename: Xiao-Qian
authors.initials: XQ
authors.lastname: Dang
authors.affiliation: The First Department of Orthopaedics, the Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, No.157 Xiwu Road, Xi'an, Shaanxi Province, 710004, P. R. China. wkzh1955@163.com.
authors.forename: Kun-Zheng
authors.initials: KZ
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D004195:Disease Models, Animal; D005270:Femur Head / Q000378:metabolism* / Q000473:pathology; D005271:Femur Head Necrosis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008070:Lipopolysaccharides; D008297:Male; D008775:Methylprednisolone; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D060449:Wnt Signaling Pathway; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism*
chemical_list: C494828:Bax protein, rat; C495268:Ctnnb1 protein, rat; D008070:Lipopolysaccharides; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D051028:bcl-2-Associated X Protein; D051176:beta Catenin; C505410:Casp3 protein, rat; D053148:Caspase 3; D008775:Methylprednisolone