RANK/RANKL/OPG signaling pathways in necrotic jaw bone from bisphosphonate-treated subjects

Area of Science:

• Oral pathology
• Bone biology
• Pharmacology

Background:

• Osteonecrosis of the jaw (ONJ) is a serious complication in patients on long-term bisphosphonate therapy.
• The exact mechanisms driving ONJ pathogenesis remain unclear.
• Understanding these mechanisms is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the role of the RANK/RANKL/OPG signaling pathway in bisphosphonate-related ONJ.
• To evaluate angiogenic and matrix mineralization processes in ONJ bone samples.
• To explore potential triggers and host responses in ONJ development.

Main Methods:

• Analysis of necrotic and healthy jaw bone samples using Light and Field Emission in Lens Scanning Electron Microscopy (FEISEM).
• Real-Time RT-PCR to assess gene expression of RANK, RANKL, and OPG.
• Immunohistochemical analysis for VEGF and Bone Sialoprotein (BSP) expression.

Main Results:

• Necrotic bone exhibited empty osteocytic lacunae, altered lamellar organization, and degraded mineralized matrix.
• Significant upregulation of RANK, RANKL, TRAF6, and NFAT2 gene expression was observed in ONJ samples.
• A decrease in OPG gene transcription and lower BSP expression were noted in necrotic bone compared to controls; VEGF expression showed no significant difference.

Conclusions:

• While bisphosphonate-associated ONJ pathogenesis is not fully understood, oral pathogens appear to play a role.
• Bacterial lipopolysaccharides may activate the RANK/RANKL/OPG pathway in ONJ.
• Osteoclast activation might serve as a host defense mechanism to contain necrotic bone and combat infection.