RESUMO
PURPOSE: The intracellular mechanisms that lead to periprosthetic osteolysis including impaired bone forming activity of osteoblast remain incompletely characterized. To determine the possibility that Ti-particles play a role to regulate Wnt/beta-catenin signaling pathway in impaired osteogenesis, we analyzed the stability of beta-catenin and the transcriptional changes of regulators for Wnt/beta-catenin signaling pathway in MC3T3-E1 osteoblast cells. MATERIALS AND METHODS: Ti-particles were prepared by sterilizing and counted on the microscopy. Transcriptional changes of OPG, RANKL, LRP5, LRP6, DKK1 and sFRP2 were determined by real-time RTPCR. Protein level of beta-catenin and GSK3beta was detected using Western blotting and immunofluorescence staining. RESULTS: After 4 hours of treatment of Ti-particles, OPG/RANKL mRNA ratio was significantly decreased. And also, decreased protein levels of beta-catenin and phospho-GSK3beta were detected. Using immunofluorescence stain, it was confirmed that Ti-particles suppressed nucleus staining of beta-catenin induced by Wnt3a conditioned medium. The results of real-time RT-PCR showed reduced level of LRP5 and LRP6 transcripts, and induced level of DKK1 and sFRP2 transcripts by challenging of Ti-particles CONCLUSION: Our report suggests that Ti-particles may play a crucial role in the regulation of Wnt/beta-catenin signaling pathway in osteoblast through the transcriptional changes of membrane receptors and extracellular inhibitors for Wnt.