Objective      To analyze G protein-coupled receptor 48 (GPR48) and toll-like receptor 4 (TLR4) expression changes and regulation activities in steroid-induced a

vascular necrosis of the femoral head in rats.        Methods      Sixty-eight SD rats were randomly divided into 2 groups

an experimental group (44 rats injected with dexamethasone sodium phosphate 10 mg/kg weekly) and a control group (22 rats injected with an equal volume of normal saline). At week 2

6

8

and 10

rats were sacrificed (11 rats in the experimental group and 6 rats in the control group at each time point) to obtain femoral heads

followed by histological observation

immunohistochemistry assay and RT-PCR detection.        Results      (1) HE staining results revealed that the experimental group showed occasionally small micro-fractures at week 2 and displayed a wide range of trabecular bone fracture at week 10. Masson trichrome staining results revealed that the per unit area of collagen content in the experimental group was significantly higher at weeks 6

8 and 10 than that in the control group (

P

0.05). (2) Compared with the control group at weeks 6

8 and 10

the experimental group showed significantly decreased GPR48 level (5.87±0.53

4.82±0.52

and 3.94±0.49

respectively

P

0.05) and increased TLR4 level (6.93±0.58

8.10±0.46 and 8.70±0.95

respectively

P

0.05). It displayed a negative correlation between GPR48 and TLR4 expression (r=-0.821

P

0.05) at different time points. (4) Compared with the control group

GPR48 mRNA expression in the experimental group was markedly decreased while TLR4 mRNA was increased in a time-dependent manner (

P

0.05). It also displayed a negative correlation between GPR48 and TLR4 mRNA levels (r=-0.791

P

0.05) at different time points.       Conclusion      GPR48 and TLR4 expression is negatively correlated and mediates the inflammation and immune reaction in the progression of steroid-induced avascular necrosis of the femoral head in rats.