Toll-like Receptor and Chemokine Profiles of Healthy Human Dental Pulp

Recent studies have demonstrated that human dental pulp cells are able to sense pathogens and to elicit innate and adaptive immunity. However, how immunosurveillance is established and regulated in the whole dental pulp remains unknown. Objective: To determine the Toll-like receptor (TLR) and chemokine gene expression profiles of healthy human dental pulp. Methods: Toll-like receptors: Ten healthy non-erupted human third molars extracted for orthodontic reasons were used. Dental pulps were collected, and then total RNA was extracted and reverse-transcribed. TLR cDNAs were amplified by conventional polymerase chain reaction using specific primers. Chemokines: Five dental pulps from healthy non-erupted human third molars were used. Total RNA was extracted and reverse-transcribed, then cDNA was added to the RT2 qPCR Master Mix (SuperArray). The mixture was aliquoted accross “Human chemokines and receptors” PCR Array plates (SuperArray) and real-time polymerase chain reaction was performed in an iCycler (Bio-Rad). Results are presented as the mean of Ct values obtained for pulps in which chemokine and/or receptor gene expression was detected (Ct < 35). Threshold cycle (Ct) values greater than 35 were considered negative (no gene expression). Results: All TLR genes (TLR1-10) were found to be expressed in healthy pulp, as well as several chemokine genes including CXCL12, CCL2, CXCL9, CX3CL1, CCL8, CXCL10, CCL16, CCL5, CXCL2, CCL4, CXCL11 and CCL3, and chemokine receptor genes including CXCR4, CCR1, CCR5, CX3CR1, CCR10 and CXCR3. Interestingly, most chemokines were expressed in the tissue together with at least one of their specific receptors. Conclusion: Healthy human dental pulp is particularly well-equipped to detect pathogens penetrating into the tooth and expresses chemokines that might play a role in the establishment and regulation of pulp immune homeostasis. Supported by the French Ministery of Higher Education and Research.