Abstract:

BACKGROUND: Under wear particles stimulation, mononuclear macrophages, fibroblasts, and osteoblasts can produce a large amount of inflammatory factors, leading to periprosthetic osteolysis. But the precise mechanisms remain unclear.

OBJECTIVE: To analyze the molecular biological mechanism underlying osteolysis induced by titanium wear particles .

METHODS: Macrophages were separately cultured with cleaned titanium particles, lipoplysaccharide (LPS)-bound titanium particles, and LPS solution. At 4, 8, 16, and 32 hours, mRNA expression levels of receptor activator of nuclear factor kappa B (RANK) and osteoprotegerin (OPG) were detected by reverse transcription-polymerase chain reaction and nuclear factor kappa B (NF-кB) binding activity was analyzed using electrophoretic mobility shift assay (EMSA).

RESULTS AND CONCLUSION: Cleaned titanium particles stimulation induced an unbalanced ratio of RANK mRNA to OPG mRNA. Over-expressed RANK bound to RANK ligand and promoted osteolysis. No RANK mRNA expression was detected in the LPS group, but OPG mRNA expression was transiently increased at 4 hours. NF-κB/inflammatory cytokine, rather than RANK/OPG, is the main signal pathway for LPS to induce osteolysis. After LPS binding to titanium particles, these two signal mechanisms, RANK/OPG and NF-κB/inflammatory cytokine, have synergistic effects during artificial joint loosening.