Interleukin-38 promotes alveolar bone repair in periodontitis by suppressing the nuclear factor kappa B pathway.

Periodontitis, characterized by chronic inflammation and alveolar bone loss, poses significant challenges to oral health. Interleukin-38 (IL-38) has emerged as a potential therapeutic agent due to its anti-inflammatory properties. This study aimed to investigate whether and how IL-38 protects against periodontitis in a ligation-induced periodontitis (LIP) mouse model and an inflammatory osteogenic model using human periodontal ligament stem cells (hPDLSCs). 40 mice were divided into 4 groups (n = 10/group): Control, LIP, LIP + phosphate-buffered saline (PBS), LIP + IL-38. The animals were euthanized and tissue samples (jaws and gingivae) were collected on day 5. Recombinant mouse IL-38 (rmIL-38) lentivirus was used for IL-38 overexpression or knockdown in hPDLSCs in vitro, and shIL-38 hPDLSCs were ultimately treated with the NF-κB inhibitor Bay11-7082. The above tissue and cellular samples were collected for micro-computed tomography (micro-CT) imaging, histological, polymerase chain reaction (qRT-PCR) and Western blot (WB) to analyze bone microstructure, inflammatory markers, osteogenic markers, and the relevant protein level of the nuclear factor kappa B (NF-κB) pathway. Correction version for Methods: Forty mice were randomized into four groups (n = 10 per group): Control, ligature-induced periodontitis (LIP), LIP + PBS, and LIP + recombinant mouse IL-38 (rmIL-38). The LIP + rmIL-38 group received daily gingival rmIL-38 injection, and all mice were euthanized on day 5 to harvest jaw and gingival tissues. In vitro, lentiviral transfection generated IL-38-overexpressing and IL-38-knockdown hPDLSCs; NF-κB inhibitor Bay11-7082 was applied to IL-38-knockdown hPDLSCs for rescue assays. All tissue and cell samples were analyzed via micro-computed tomography (micro-CT) imaging, histological, polymerase chain reaction (qRT-PCR) and Western blot (WB) to analyze bone microstructure, inflammatory markers, osteogenic markers, and the relevant protein level of the nuclear factor kappa B (NF-κB) pathway. In vivo, rmIL-38 administration significantly reduced pro-inflammatory cytokine expression (Il1b, Il17a, Il6 and Il23a) and suppressed NF-κB pathway activation, which can be evidenced by decreased phospho-p65 levels. Furthermore, micro-CT analysis showed that rmIL-38 mitigated alveolar bone loss and improved the bone microstructure assessed. In vitro, IL-38 overexpression enhanced osteogenic marker expression (ALP, RUNX2, and COL1A1) while inhibiting NF-κB signaling, whereas IL-38 knockdown produced the opposite effects. Notably, Bay11-7082 treatment rescued impaired osteogenic marker expression in IL-38 knockdown hPDLSCs. Correction version for Results: In vivo, local rmIL-38 administration markedly suppressed pro-inflammatory cytokines Il17a and Il23a and upregulated the anti-inflammatory cytokine Il10. Micro-CT, immunofluorescence and Masson staining further confirmed that rmIL-38 alleviated alveolar bone loss and exerted pro-osteogenic effects. In vitro, IL-38 overexpression elevated osteogenic markers (ALP, RUNX2, COL1A1) and repressed NF-κB signaling, whereas IL-38 knockdown exerted opposite effects. Notably, NF-κB inhibition by Bay11-7082 rescued the impaired osteogenic capacity of IL-38-knockdown hPDLSCs. Collectively, these findings suggest that IL-38 mitigates periodontitis progression by limiting inflammation and promoting osteogenic differentiation through NF-κB pathway inhibition, highlighting its potential as a therapeutic target in periodontal disease management.