Tian Lei, Zhou Dong-Sheng, Wang Kun-Zheng, Zhang Wei, Shi Zhi-Bin, Fan Li-Hong, Sun Shui
Department of Orthopedics, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China.
Department of Orthopedics, The Second Affiliated Hospital, College of Medicine, Xi'an Jiaotong University, Xi'an, 710061, China.
J Huazhong Univ Sci Technolog Med Sci. 2014 Oct;34(5):679-686. doi: 10.1007/s11596-014-1336-7. Epub 2014 Oct 16.
Osteonecrosis of the femoral head is frequently observed in patients treated with excessive corticosteroids. However, the pathogenesis of corticosteroid-induced osteonecrosis remains unclear. The purpose of this study was to investigate the role of Toll-like receptor 4 (TLR4) signaling pathway in steroid-induced femoral head osteonecrosis in rats. Male Sprague-Dawley rats were injected intramuscularly with 20 mg/kg methylprednisolone (MP) for 8 weeks, twice per week. The animals were sacrificed at 2, 4 and 8 weeks after the last MP injection, respectively, and then allocated to the 2-, 4- and 8-week model groups (n=24 each). Rats in the control group (n=12) were not given any treatment. Histopathological analysis was performed and the concentration of tartrate-resistant acid phosphatase (TRAP) in plasma was determined. The activation of osteoclasts in the femoral head was assessed by TRAP staining. The expression of TLR4, MyD88, TRAF6 and NF-κB p65 that are involved in TLR4 signaling, and MCP-1 production were detected by using real-time PCR (RT-PCR) and Western blotting. The results showed that the osteonecrosis in the femoral head was clearly observed and the concentration of TRAP in the plasma was increased in the model rats. The femoral head tissues in MP-treated rats were positive for TRAP and the intensity of TRAP staining was greater in MP-treated rats than in control rats. As compared with the control group, the mRNA expression of TLR4 signaling-related factors was enhanced significantly at 4 and 8 weeks, and the protein levels of these factors increased significantly with time. It was concluded that MP could induce the femoral head osteonecrosis in rats, which was associated with osteoclast activation via the TLR4 signaling pathway. These findings suggest that TLR4 signaling pathway plays a pivotal role in the pathogenesis of steroid-induced osteonecrosis.
在接受大量皮质类固醇治疗的患者中，股骨头坏死较为常见。然而，皮质类固醇诱导的股骨头坏死的发病机制仍不清楚。本研究的目的是探讨Toll样受体4（TLR4）信号通路在大鼠类固醇诱导的股骨头坏死中的作用。雄性Sprague-Dawley大鼠每周两次肌肉注射20mg/kg甲泼尼龙（MP），共8周。分别在最后一次MP注射后2周、4周和8周处死动物，然后分为2周、4周和8周模型组（每组n = 24）。对照组大鼠（n = 12）不给予任何处理。进行组织病理学分析并测定血浆中抗酒石酸酸性磷酸酶（TRAP）的浓度。通过TRAP染色评估股骨头中破骨细胞的活化情况。采用实时定量聚合酶链反应（RT-PCR）和蛋白质免疫印迹法检测参与TLR4信号传导的TLR4、MyD88、TRAF6和NF-κB p65的表达以及单核细胞趋化蛋白-1（MCP-1）的产生。结果显示，模型大鼠股骨头出现明显坏死，血浆中TRAP浓度升高。MP处理大鼠的股骨头组织TRAP染色呈阳性，且MP处理大鼠的TRAP染色强度高于对照大鼠。与对照组相比，TLR4信号相关因子的mRNA表达在4周和8周时显著增强，且这些因子的蛋白水平随时间显著升高。结论是，MP可诱导大鼠股骨头坏死，这与通过TLR4信号通路激活破骨细胞有关。这些发现表明，TLR4信号通路在类固醇诱导的骨坏死发病机制中起关键作用。
