Abstract
BackgroundThe 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.MethodsMale 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.ResultsTypical 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.ConclusionsThe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-015-0606-2) contains supplementary material, which is available to authorized users.
Highlights
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
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
These findings indicate that abnormalities in the Wnt/β-catenin signalling pathway are involved in early stage steroid-induced avascular necrosis of the femoral head (SANFH)
Summary
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. Several mechanisms have been postulated, including coagulation, Studies have demonstrated the strong association of osteoblast and osteocyte apoptosis with SANFH [1,2,3,4]. Weinstein and his colleagues have studied osteocyte apoptosis in femoral head specimens of 14 patients with necrosis of the femoral head using TUNEL staining assay [5], showing the appearance of marked osteocyte apoptosis in specimens from patients with SANFH, while apoptosis was absent or rare in specimens from. Few studies have been conducted to investigate the role of this pathway in SANFH
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