OR11 - C-C Motif Chemokine Ligand 2 (CCL2) Local Delivery to Contain Apical Periodontitis Development

Apical periodontitis (AP) is a sequel of root canal infection. C-C motif chemokine ligand-2 (CCL2) is a chemoattractant that induces macrophage polarization to an M2 phenotype, thereby contributing to inflammation resolution. We hypothesized that local delivery of CCL2 using controlled-release microparticles might induce an M2 phenotype and healing of AP. To test this hypothesis, we investigated the presence of differentially expressed genes (DEGs) in the subcutaneous tissues of C57BL/6NJ mice after implantation of tooth fragments filled with CCL2 or controls. 20 human single-rooted canal teeth were used for preparation of 20 root fragments (5 mm in length, canal diameter of 80/.02). Fragments were inoculated with a mixture of Prevotella intermedia, Fusobacterium nucleatum, and E. faecalis, incubated for seven days, and then filled with either CCL2 gel (n=10), or left empty (control, n=10). One CCL2 and one control fragment were then implanted in each side of the dorsal of eight-week-old mice (n=10). Mice were euthanized after 7 and 28 days (n=5 each period) post-implantation and tissues collected for further analysis. Histological analysis showed low-grade inflammation in the tissues surrounding CCL2-filled fragments whereas tissues surrounding control fragments showed severe inflammation (ANOVA; P< 0.05). RNA-sequencing revealed several DEGs between the groups ( >2-fold changes), including genes encoding inflammatory cytokines and growth factors (e.g., TNF-α, IL-1β, TGF-β1) as well as genes related to VEGF signaling pathways. These findings suggest that local delivery of CCL2 promotes a pro-healing environment by inducing the expression of multiple relevant genes and might be considered for targeted AP therapies.