Production of TNF-𝛼 by macrophages stimulated with endodontic pathogens and its effect on the biological properties of stem cells of the apical papilla

Abstract

The first objective of the present study was to investigate TNF-𝛼 secretion by macrophages stimulated with endodontic pathogens and bacterial cell surface components. The second objective was to assess the in vitro effects of TNF-𝛼 on periostin, cytokine, and matrix metalloproteinase (MMP) secretion by and the viability, proliferation rate, and mineralization potential of stem cells of the apical papilla (SCAP). TNF-𝛼 secretion by macrophages stimulated with either endodontic pathogens or bacterial surface components was assessed using an enzyme-linked immunosorbent assay (ELISA). The viability and proliferation rate of SCAP treated with TNF-𝛼 were assessed using a colorimetric MTT assay. The mineralization potential of TNF-𝛼-treated SCAP was determined by Alizarin Red staining. Periostin secretion by SCAP was determined by ELISA while cytokine and MMP secretion were assessed using a multiplexing laser bead assay. TNF-𝛼 secretion by macrophages increased following a stimulation with Gram-negative and Gram-positive endodontic pathogens. Lipopolysaccharide and lipoteichoic acid also dose-dependently increased the secretion of TNF-𝛼 by macrophages. The viability, proliferation rate, and mineralization activity of SCAP were negatively affected by a TNF-𝛼 treatment. Treating SCAP with TNF-𝛼 attenuated the secretion of periostin and upregulated the secretion of several cytokines and MMPs. TNF-𝛼 exerts deleterious effects on SCAP by affecting their viability, proliferation rate, and mineralization potential. By its ability to induce the secretion of pro-inflammatory cytokines and MMPs by SCAP, TNF-𝛼 can contribute to creating an inflammatory environment, promoting tissue destruction, and consequently interfering with the success of regenerative endodontic therapy. TNF-𝛼 has deleterious impacts on stem cells of the apical papilla and may compromise the outcome of regenerative endodontic therapy.