Graphene quantum dots remodel osteogenesis of human periodontal ligament stem cells under inflammatory microenvironment: an in vitro and in vivo study.

OBJECTIVE: This study aims to provide experimental basis that underpins the potential application of graphene quantum dots (GQDs) as a therapeutic strategy for periodontitis. METHODS AND MATERIALS: An inflammatory circumstance was established by Porphyromonas gingivalis lipopolysaccharide (P.g-LPS). The effects of GQDs on human periodontal ligament stem cells (hPDLSCs) proliferation, migration and osteogenic differentiation in vitro were assessed using Cell Counting Kit-8 (CCK-8), Transwell assay, alkaline phosphatase (ALP) and alizarin red S (ARS) staining, ALP activity and ARS semi-quantification. The anti-inflammatory activity was evaluated by Enzyme-linked immunosorbent assay (Elisa). The underlying osteogenic mechanism was initially explored by mRNA sequencing (mRNA-Seq) and further correlated with gene and protein expression changes via quantitative real-time PCR (RT-qPCR) and Western blot (WB) analysis. Furthermore, the in vivo efficacy and biosafety of GQDs were evaluated in a rat periodontitis model using micro computed tomography (Micro-CT) and histomorphometric analysis. RESULT: In vitro, GQDs exhibited favorable cytocompatibility and enhanced the viability, migration, osteogenesis of hPDLSCs under normal conditions. In inflammatory microenvironment, GQDs significantly counteracted the suppression of P.g-LPS on hPDLSCs proliferation, migration, osteogenic differentiation, and notably reduced the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6). Mechanistically, mRNA-Seq identified the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) and mitogen-activated protein kinase (MAPK) signaling pathways as potentially associated in the osteogenic modulation of GQDs on hPDLSCs in both normal and inflammatory settings. Subsequent validation showed that GQDs upregulated the mRNA and total protein levels of p38, PI3K, and Akt. In vivo, local administration of GQDs attenuated alveolar bone resorption, suppressed osteoclast activity and formation, and reduced inflammatory infiltration with no observable systemic toxicity. CONCLUSION: GQDs possess the capacity to counteract inflammation-induced damage and promote osteogenic restoration both in vitro and in vivo, highlighting their potential dual functionality in periodontal regeneration.