糖皮质激素诱导骨细胞脂肪化与股骨头坏死的病理机制研究

目的 探讨糖皮质激素(glucocorticoids,GCs)诱导股骨头坏死(osteonecrosis of the femoral head,ONFH)的发病机制.方法 收集激素性ONFH及骨关节炎患者股骨头离体标本,采用免疫组化染色观察两组成骨转录分化因子Runx2和成脂转录分化因子PPAR-γ表达.大鼠颅骨源性成骨细胞在地塞米松作用下培养,茜素红矿化结节染色,油红“O”染色,RT-PCR检测Runx2 、PPAR-γ、OCN 、Col Ⅰ基因转录水平表达,免疫组织化学染色Runx2和PPAR-γ表达.激素法建立大鼠ONFH模型并确认建模成功,油红“O”染色脂肪细胞,免疫组化染色观察两组Runx2和PPAR-γ表达.结果 与骨关节炎比较,ONFH患者股骨头骨小梁间隙大量脂肪细胞聚集,并且脂肪细胞体积增大,Runx2表达显著下调,PPAR-γ表达上调.大剂量GCs作用下成骨细胞分化过程中未见茜素红矿化结节,油红“O”染色脂肪细胞,RT-PCR检测基因Runx2、OCN 、Col Ⅰ表达下调,PPAR-γ基因表达上调.大鼠ONFH模型股骨头骨小梁间隙脂肪细胞积聚、增大,Runx2表达下调,PPAR-γ表达上调.结论 大剂量GCs作用下,PPAR-γ表达上调、Runx2表达下调,调控骨髓基质细胞向脂肪细胞分化并促进成骨细胞、骨细胞转分化为脂肪细胞,同时抑制成骨细胞的分化、成熟及活性表达,可能是GCs诱发ONFH的主要病理生理机制之一.

Steroid induced adipogenesis: may be the pathogenesis of osteonecrosis of the femoral head

Objective To explore the role of the steroids induced adipogenesis in pathogenesis of glucocorticoid-induced osteonecrosis of the femoral head (ONFH). Methods Femoral heads respectively diagnosed glucocortcoid-induced ONFH and osteoarthritis (OA), which were obtained during total hip arthroplasty, were made histopathological and immunohistochemistry study. Osteoblasts cultured in DMEM(H)medium with 10% FBS supplemented with dexamethasone in different concentrations(0, 1×10-8, 1×10-7, 1×10-6 mol/L) were divided into 3 groups. Three groups were received alizarin red staining and oil red O staining at different time. The expression of PPAR-γ and Runx2 were performed by immunohistochemistry study. SD rats were injected high-dose of methylprednisolone to establish a steroid-induced ONFH model. At 12th weeks after intervention, histopathological and immunohistochemistry were performed for the presence of osteonecrosis and adipogeneisis, Runx2 and PPAR-γ expression in the femoral head. Results The number and the size of adipocytes significantly increased in ONFH group by comparison with OA group. The expression of PPAR-γ was increased while Runx2 expression was decreased in ONFH group, compared to the OA group. Compared with control group, dexamethasone(1×10-6, 10-7 mol/L) significantly induced the mRNA expression of PPAR-γ, while the expression of Runx2 was significantly decreased. Osteoblasts treated with 10-6 mol/L dexamethasone can promote osteoblast transdifferentiated into adipocytes. Evidence of osteonecrosis and adipogenesis were observed in steroid treated rats. The number and the size of adipocytes were increased significantly compared with control group. At the same time, the expression of PPAR-γ was increased and the Runx2 was decreased. Conclusion The steroids stimulating the PPAR-γ expression and inhibiting the Runx2 expression, which resulted in BMSCs differentiating into adipocytes and inhibited osteoblasts differentiation activity, may be one of important pathogenesis mechanism of steroid-induced ONFH.