Injectable Thermosensitive Hydrogel for Immunomodulation of Dendritic Cells to Promote Healing in Periodontitis Complicated by Metabolic Disease

Periodontitis is a multifactorial inflammatory disease that involves prolonged, dysregulated inflammation between the dysbiotic microbiota and the host immune system. Other co-morbidities, such as metabolic syndrome, can further exacerbate the progression of periodontitis through systemic inflammation. Conventional non-surgical periodontal treatment such as scaling and root planing (SRP) has shown clinical success, but it doesn’t address the inflammation contributed by metabolic syndrome. Moreover, it doesn’t actively facilitate the transition into the healing phase following treatment either. Herein, we aimed to develop a biomaterial-based adjuvant treatment that immunomodulates the oral microenvironment by targeting dendritic cells (DCs) to promote healing in periodontitis complicated by metabolic syndrome. First, a chitosan-based thermosensitive injectable self-assembled hydrogel (TISH) was developed and characterized. TISH demonstrated an interconnected porous structure that allows cell migration and adhesion. Moreover, TISH demonstrated good biocompatibility and cell penetration in its porous structure. Bioactive molecules such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and resveratrol were loaded into TISH (TISH(GR)), and they were sustainably released. Then, the immunomodulatory property of TISH(GR) on DCs and T-cells was evaluated in vitro under a hyperglycemic condition. DCs grown in TISH(GR) under hyperglycemia showed reduced maturation and activation markers such as CD80, CD83, and CD86, while simultaneously upregulating tolerogenic genes such as FOXP3, SOCS3, TGFβ, and IL10. Co-culture of these tolerogenic DCs with naïve T-cells induced regulatory T-cells (Tregs) differentiation, evidenced by elevated gene expressions of FOXP3, TGFβ, and IL-10. In vivo subcutaneous injection of TISH (GR) into the mice showed significant infiltration of DCs and Tregs. Mechanistically, TISH(GR) immunomodulates DCs by suppressing the inflammatory signaling pathways that are downstream of the toll-like receptor 4. Lastly, in a high-fat periodontitis rat model, TISH(GR) as an adjuvant treatment significantly alleviated periodontal inflammation and tissue destruction compared to the group that only received SRP treatment. TISH(GR) treatment led to a significantly lower infiltrated population of TH17 cells into the periodontium. In conclusion, TISH was developed and optimized as an injectable hydrogel to immunomodulate DCs and T-cells in the periodontium. TISH (GR) showed a promising potential to treat periodontitis in immunocompromised patients diagnosed with metabolic disorders.