Zirconia/dental pulp stem cell composite scaffolds repair osteogenic defect via regulating macrophages.

BACKGROUND: Dental pulp stem cells (DPSCs) possess multilineage differentiation potential and immunomodulatory properties, making them promising candidates for bone regeneration. In this study, the regenerative potential of DPSCs combined with nitrogen-doped reduced graphene oxide/zirconia (N-Rgo/ZrO(2)) composite scaffolds was investigated in vitro and in a rat jaw injury model. METHODS: The primary human DPSCs were characterized by flow cytometry (CD90/CD29/CD45) and trilineage differentiation assays. In vitro effects on macrophage polarization (IL-6, TNF-α, CD206, Arg1, iNOS, IL-10) and MAPK signaling (p-ERK1/2, p-p38) were analyzed using qRT-PCR and Western blot. A rat bone defect model was established to evaluate mandibular bone regeneration through H&E staining, Masson's trichrome, and molecular analysis of osteogenic markers (RUNX2, ALP, Osterix, OPN, OCN) and pathway activation. RESULTS: DPSCs exhibited characteristic mesenchymal markers (CD90(+): 90.16% ± 1.00%; CD29(+): 99.27% ± 0.11%) and multilineage differentiation capacity. N-Rgo/ZrO2+DPSCs synergistically upregulated M2 macrophage markers (CD206, Arg1, IL-10) and pro-osteogenic cytokines (TNF-α) while suppressing IL-6. This combination potently activated p-ERK1/2 and p-p38 MAPK, exceeding single-treatment effects. In vivo, cotreatment restored trabecular architecture (collagen fiber density), improved rat pathological conditions, and significantly elevated osteogenic markers (RUNX2, ALP, Osterix, OPN and OCN) compared with monotherapies. CONCLUSION: The N-Rgo/ZrO2+DPSCs composite promotes bone regeneration through dual mechanisms: (1) immunomodulation through M2 macrophage polarization and MAPK pathway activation and (2) direct osteogenic differentiation. This strategy demonstrates superior efficacy to individual components, offering a novel combinatorial approach for maxillofacial bone repair.