The pathogenesis of periapical lesions is determined by the balance between host pro-inflammatory immune response and counteracting anti-inflammatory and reparative responses, which include regulatory T cells (Tregs) as potential immunoregulatory agents. In this study, we investigated (in a cause-and-effect manner) the involvement of CCL22-CCR4 axis in Tregs migration to the periapical area and the role of Tregs in the determination of outcomes in periapical lesions.
Periapical lesions were induced in C57Bl/6 (WT) and CCR4KO mice (pulp exposure and bacterial inoculation), and treated with anti-GITR to inhibit Tregs function or alternatively with CCL22-releasing, PLGA particles to induce site-specific migration of Tregs. Post treatment, lesions were analyzed for Tregs influx and phenotype, overall periapical bone loss and inflammatory/immunological and wound healing markers expression (analyzed by RealTimePCRarray).
Tregs inhibition by anti-GITR or CCR4 depletion results in a significant increase in periapical lesions severity, associated with upregulation of proinflammatory, Th1, Th17 and tissue destruction markers in parallel with decreased Tregs and healing markers expression. The local release of CCL22 in the root canal system resulted in the promotion of Tregs migration in a CCR4-dependent manner, leading to the arrest of periapical lesions progression, associated with downregulation of pro-inflammatory, Th1, Th17 and tissue destruction markers in parallel with increased Tregs and healing markers expression.
Since the natural and CCL22 induced Tregs migration switch active lesion into inactivity phenotype, Tregs chemoattractant may be a promisor strategy for the clinical management of periapical lesions.
Francisconi, C. F., Vieira, A. E., Biguetti, C. C., Glowacki, A. J., Trombone, A. P., Letra, A., Menezes Silva, R., Sfeir, C. S., Little, S. R., & Garlet, G. P. (2016). Characterization of the Protective Role of Regulatory T Cells in Experimental Periapical Lesion Development and Their Chemoattraction Manipulation as a Therapeutic Tool. Journal of endodontics, 42(1), 120–126. https://doi.org/10.1016/j.joen.2015.09.022
Journal of endodontics