Immune Cells and Molecular Networks in Experimentally Induced Pulpitis

• Published in: Journal of dental research 2016-02, Vol.95 (2), p.196-205
• Main Authors: Renard, E., Gaudin, A., Bienvenu, G., Amiaud, J., Farges, J.C., Cuturi, M.C., Moreau, A., Alliot-Licht, B.
• Format: Article
• Language: English
• Subjects: Animals; Bacteria; Chemokine CCL2; Chemokine CCL2 - analysis; Chemokine CXCL1; Chemokine CXCL1 - analysis; Chemokines; Chemokines - analysis; Cytokines; Cytokines - analysis; Data analysis; Dendritic Cells; Dendritic Cells - pathology; Dental Pulp; Dental Pulp - enzymology; Dental Pulp - immunology; Dentin; Dentin, Secondary; Dentin, Secondary - immunology; Dentistry; Disease Models, Animal; Female; Gelatinase B; Gene expression; Gram-Negative Bacteria; Gram-Negative Bacteria - immunology; Gram-positive bacteria; Growth factors; Immunoregulation; Incisors; Inflammation; Inflammation Mediators; Inflammation Mediators - analysis; Interleukin 1; Interleukin 10; Interleukin 6; Interleukin-10 - analysis; Interleukin-1beta; Interleukin-1beta - analysis; Interleukin-6 - analysis; Irritation; Leukocyte migration; Leukocytes; Leukocytes - classification; Life Sciences; Lipopolysaccharides; Lipopolysaccharides - immunology; Matrix Metalloproteinase 9; Matrix Metalloproteinase 9 - analysis; Monocyte chemoattractant protein 1; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type II - analysis; Nitric-oxide synthase; Population; Pulpitis; Pulpitis - enzymology; Pulpitis - immunology; Rats; Rats, Sprague-Dawley; T-Lymphocytes; T-Lymphocytes - immunology; T-Lymphocytes, Regulatory; T-Lymphocytes, Regulatory - pathology; Teeth; Time Factors; Transcription; Tumor Necrosis Factor-alpha; Tumor Necrosis Factor-alpha - analysis; Tumor necrosis factor-α; Wound healing
• ISSN: 0022-0345; 1544-0591
• DOI: 10.1177/0022034515612086

Dental pulp is a dynamic tissue able to resist external irritation during tooth decay by using immunocompetent cells involved in innate and adaptive responses. To better understand the immune response of pulp toward gram-negative bacteria, we analyzed biological mediators and immunocompetent cells in rat incisor pulp experimentally inflamed by either lipopolysaccharide (LPS) or saline solution (phosphate-buffered saline [PBS]). Untreated teeth were used as control. Expression of pro- and anti-inflammatory cytokines, chemokine ligands, growth factors, and enzymes were evaluated at the transcript level, and the recruitment of the different leukocytes in pulp was measured by fluorescence-activated cell-sorting analysis after 3 h, 9 h, and 3 d post-PBS or post-LPS treatment. After 3 d, injured rat incisors showed pulp wound healing and production of reparative dentin in both LPS and PBS conditions, testifying to the reversible pulpitis status of this model. IL6, IL1-β, TNF-α, CCL2, CXCL1, CXCL2, MMP9, and iNOS gene expression were significantly upregulated after 3 h of LPS stimulation as compared with PBS. The immunoregulatory cytokine IL10 was also upregulated after 3 h, suggesting that LPS stimulates not only inflammation but also immunoregulation. Fluorescence-activated cell-sorting analysis revealed a significant, rapid, and transient increase in leukocyte levels 9 h after PBS and LPS stimulation. The quantity of dendritic cells was significantly upregulated with LPS versus PBS. Interestingly, we identified a myeloid-derived suppressor cell–enriched cell population in noninjured rodent incisor dental pulp. The percentage of this population, known to regulate immune response, was higher 9 h after inflammation triggered with PBS and LPS as compared with the control. Taken together, these data offer a better understanding of the mechanisms involved in the regulation of dental pulp immunity that may be elicited by gram-negative bacteria.