Membrane-free stem cell components suppress osteoclast differentiation: Implications for oral regenerative treatment

Membrane-free stem cell components (MFSCCs) have been developed by removing cell membranes with antigens to overcome the limitations associated with cell-based therapies and isolate effective peptides. MFSCCs have been reported to have effects on oral infection sites. Chronic inflammatory diseases cause excessive bone resorption. This study investigated the effects of MFSCCs on osteoclast differentiation in the context of the high prevalence of inflammatory bone resorption. Bone marrow macrophages (BMMs) were treated with macrophage colony-stimulating factor and receptor activator of nuclear factor kappa-B ligand. Osteoclast differentiation was assessed based on the MFSCC concentrations. Tartrate-resistant acid phosphatase (TRAP)-stained mature osteoclasts and multinucleated cells derived from BMMs were analyzed using light microscopy. The messenger RNA (mRNA) expression levels of genes related to osteoclast differentiation were measured using real-time polymerase chain reaction (RT-PCR). The relative expression levels of the key transcription factors c-fos and nuclear factor of activated T cells (NFATc1) were determined using quantitative RT-PCR and western blotting. After treatment with MFSCCs, the cell viability was similar, depending on the level of BMMs. As the MFSCC concentration increased, the number of TRAP-positive cells decreased. The mRNA and protein expression of cathepsin K, TRAP, dendritic cell-specific transmembrane protein, c-fos, and NFATc1 decreased as the MFSCC concentration increased. Our findings demonstrate that MFSCCs suppress osteoclast differentiation by downregulating transcription factors, particularly, c-fos and NFATc1. Therefore, MFSCCs may serve as a conservative treatment option for chronic inflammatory bone resorption diseases of the oral cavity by suppressing excessive bone resorption.