IL-4/CCL22/CCR4 Axis Controls Regulatory T-Cell Migration That Suppresses Inflammatory Bone Loss in Murine Experimental Periodontitis

Abstract

Inflammatory bone resorption is a hallmark of periodontitis, and Tregs and Th2 cells are independently associated with disease progression attenuation. In this study, we employed an infection-triggered inflammatory osteolysis model to investigate the mechanisms underlying Treg and Th2 cell migration and the impact on disease outcome. Aggregatibacter actinomycetemcomitans–infected C57Bl/6 (wild-type [WT]) mice develop an intense inflammatory reaction and alveolar bone resorption, and Treg and Th2 cell migration is temporally associated with disease progression attenuation. Tregs extracted from the lesions preferentially express CCR4 and CCR8, whereas Th2 cells express CCR3, CCR4, and CCR8. The absence of CCR5 and CCR8 did not significantly impact the migration of Tregs and Th2 cells or affect the disease outcome. CCR4KO mice presented a minor reduction in Th2 cells in parallel with major impairment of Treg migration, which was associated with increased inflammatory bone loss and higher proinflammatory and osteoclastogenic cytokine levels. The blockade of the CCR4 ligand CCL22 in WT mice resulted in an increased inflammatory bone loss phenotype similar to that in the CCR4KO strain. Adoptive transfer of CCR4+ Tregs to the CCR4KO strain revert the increased disease phenotype to WT mice–like levels; also, the in situ production of CCL22 in the lesions is mandatory for Tregs migration and the consequent bone loss arrest. The local release of exogenous CCL22 provided by poly(lactic-co-glycolic acid) (PLGA) microparticles promotes migration of Tregs and disease arrest in the absence of endogenous CCL22 in the IL-4KO strain, characterized by the lack of endogenous CCL22 production, defective migration of Tregs, and exacerbated bone loss. In summary, our results show that the IL-4/CCL22/CCR4 axis is involved in the migration of Tregs to osteolytic lesion sites, and attenuates development of lesions by inhibiting inflammatory migration and the production of proinflammatory and osteoclastogenic mediators.

Effect of sclerostin removal <i>in vivo</i> on experimental periodontitis in mice

“…Recent studies suggest that it might be associated with a number of factors, such as higher levels of pro-inflammatory and osteoclastogenic cytokines (17). Inflammatory cytokines are considered to play a major role in disease progression as, together with WNT signaling, they can form a positive feedback loop for modulation of bone remodeling (18).…”

Characterization of the Protective Role of Regulatory T Cells in Experimental Periapical Lesion Development and Their Chemoattraction Manipulation as a Therapeutic Tool

“…Experimental groups comprised 8-week-old male C57BL/6 wild-type (WT) and CCR4 (CCR4KO) mice, treated with anti-GITR or with CCL22 releasing particles (CCL22p) (22, 23). Anti-GITR antibodies were prepared from hybridomas grown in nude mice, as previously described (26).…”

“…injection, as previously described (24). Tregs migration was induced by the CCL22-releasing PLGA microparticles (or control blank particles) (22, 23), injected (5µL of PBS/CMC solution containing 25mg/mL particles) in the root canal system at day 3 after bacterial inoculation. Animals were killed by cervical displacement after 0, 3, 7, 14 and 21 days of infection, the jaws were dissected, and independent samples were prepared for histomorphometric (right molars) or molecular (left molars) analysis.…”

“…Migration of Tregs has been associated with the chemotactic cytokine CCL22 as well as decreased severity of experimental periapical lesion in rats (21). Accordingly, CCL22 interaction with the receptor CCR4 appears to control Treg migration into mice periodontal tissues and consecutively suppresses local inflammatory bone loss (22). …”

La modulación de la expresión de IL-10 por el polimorfismo IL-10-592C/A (rs1800872) es independiente de la presencia y carga bacteriana de los periodontopatógenos clásicos

“…De forma interesante, actualmente se reconoce que puede existir una interrelación entre las respuestas Th2 y Treg (involucrando la secreción de IL-10), que resultaría en un estado de protección para la progresión de la destrucción tisular en modelos experimentales de periodontitis. En este sentido, es posible especular que la IL-10 podría ser un biomarcador de la respuesta efectora de ambos linajes de linfocitos CD4+ (Th2 y Treg) 4 .…”