Gingival mesenchymal stem cell-derived exosomes ameliorate human adult keratinocyte transformed cell line inflammation and apoptosis via the TLR4/NF-κB pathway.

OBJECTIVE: This study sought to elucidate the regulatory mechanisms of exosomes derived from gingival mesenchymal stem cells (GMSC-Exo) in the context of inflammation associated with oral lichen planus (OLP).

DESIGN: An in vitro OLP inflammatory model was established by stimulating the Human Adult Keratinocyte Transformed Cell Line (Hacat) with lipopolysaccharide (LPS). The cellular uptake of GMSC-Exo was detected by immunofluorescence. Enzyme-linked immunosorbent assay (ELISA) was employed to assess the levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10). Cell viability and apoptosis were measured by Cell Counting Kit-8 (CCK-8) assay and flow cytometry, respectively. The mRNA levels of Toll-like receptor 4 (TLR4) were determined via reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and the protein expression levels of TLR4, phosphorylated nuclear factor kappa B subunit p65 (p-P65), P65, phosphorylated IκBα (p-IκBα), and IκBα were further validated by Western Blot.

RESULTS: LPS stimulation significantly increased the secretion of pro-inflammatory cytokines (TNF-α, IL-6), decreased the production of the anti-inflammatory cytokine IL-10, and promoted Hacat cell apoptosis while impairing cell viability. Notably, administration of GMSC-Exo effectively alleviated these LPS-induced effects. Mechanistically, GMSC-Exo suppressed LPS-induced TLR4 overexpression and blocked downstream nuclear factor kappa B (NF-κB) signaling activation, as evidenced by decreased phosphorylation of IκBα and P65.

CONCLUSIONS: GMSC-Exo alleviates LPS-induced inflammation and apoptosis in Hacat cells by downregulating the TLR4/NF-κB signaling pathway. Our findings offer novel insights and potential therapeutic strategies for treating OLP.