Inhibitive effect of icariin on titanium particle-induced inflammatory osteolysis

Abstract

Objective To determine the therapeutic effect of icariin in the treatment of titanium particle-induced inflammatory osteolysis and examine the relationship between icariin and receptor activator of NF-κB ligand (RANKL)/ osteoprotegerin (OPG). Methods Eighty-four male C57BL/J6 mice were divided into four groups (21 animals for each) according to the random number table: black group, control group (titanium particles only), low-dosage icariin group (0. 1 mg·g-1·d-1, L group), and high-dosage icariin group (0. 3 mg·g-1·d-1, H group). The animal model of titanium particle-induced calvaria osteolysis was used in this study. After 2 weeks mice calvariae were harvested for micro-CT, histological and molecular analysis. Results As assessed by the micro-CT, icariin reduced particle-induced osteolysis: bone mineral density and bone volume fraction in L group was (89.44±18.51)mg/cm2 and (48.32±9.54)% and was (144.85±19.49)mg/ cm2 and (65.67±6.80)% in H group as compared to (61.23±13.41)mg/cm2 and (27.83±7.51)% in control group (P<0.05). HE staining demonstrated diminished inflammation after treatment with icariin while intensive macrophage infiltration into the calvariae in control group. Histomorphometric results demonstrated the area of eroded bone surface (EBS) was reduced to (0.07±0.01)mm2 and (0.04±0.01)mm2 respectively in L and H groups compared to (0.14±0.03)mm2 in control group (P<0.05). Tartrate resistant acid phosphatase (TRAP) staining revealed multiple TRAP-positive cells accumulated along the EBS in control group, whereas the number of TRAP-positive cells was reduced by icariin. Immunohistological examination showed titanium particle up-regulated expressions of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6. In contrast, low expressions were noted after icariin treatment. RT-PCR showed titanium particle stimulation could enhance mRNA expressions of calcitonin receptor (CTR), TRAP, cathepsin-K (Cath-K) and nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) in the clavariae tissues. However, the mRNA levels of these genes were markedly reduced after icariin treatment. ELISA results showed levels of RANKL and OPG were (23.02±4.39)pg/ml and (1 360.52±514.08)pg/ml in control group, but secretion of RANKL was reduced together with an increase in OPG by icariin[L group: (16.87±4.75), (1 890.54±550.94)pg/ml; H group: (12.80±5.77), (2 001.67±325.01)pg/ml, P<0.05]. Conclusion Icariin can effectively inhibit titanium particle-induced inflammatory osteolysis by suppressing osteoclast activity and attenuating osteolysis. Key words: Arthroplasty, replacement; Osteolysis; Osteoclasts; Titanium