title: Association of toll-like receptor 4 signaling pathway with steroid-induced femoral head osteonecrosis in rats.
abstract: 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.
authors.affiliation: Department of Orthopedics, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Tian
authors.affiliation: Department of Orthopedics, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China.
authors.forename: Dong-Sheng
authors.initials: DS
authors.lastname: Zhou
authors.affiliation: Department of Orthopedics, The Second Affiliated Hospital, College of Medicine, Xi'an Jiaotong University, Xi'an, 710061, China. wkzh-1955@gmail.com.
authors.forename: Kun-Zheng
authors.initials: KZ
authors.lastname: Wang
authors.affiliation: Department of Orthopedics, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Orthopedics, The Second Affiliated Hospital, College of Medicine, Xi'an Jiaotong University, Xi'an, 710061, China.
authors.forename: Zhi-Bin
authors.initials: ZB
authors.lastname: Shi
authors.affiliation: Department of Orthopedics, The Second Affiliated Hospital, College of Medicine, Xi'an Jiaotong University, Xi'an, 710061, China.
authors.forename: Li-Hong
authors.initials: LH
authors.lastname: Fan
authors.affiliation: Department of Orthopedics, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China. slyysunshui@163.com.
authors.forename: Shui
authors.initials: S
authors.lastname: Sun
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D005270:Femur Head / Q000378:metabolism* / Q000473:pathology; D015870:Gene Expression; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D008775:Methylprednisolone; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D010020:Osteonecrosis / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism; D000071681:Tartrate-Resistant Acid Phosphatase; D013997:Time Factors; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism
chemical_list: C491766:Ccl2 protein, rat; D018932:Chemokine CCL2; D007527:Isoenzymes; C507781:Myd88 protein, rat; D053594:Myeloid Differentiation Factor 88; D048029:TNF Receptor-Associated Factor 6; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D051996:Transcription Factor RelA; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; D008775:Methylprednisolone