Dental Pulp Stem Cells Orchestrate Macrophage Polarisation in Pulpitis via Mitochondrial Transfer.

AIM: Pulpitis represents a prevalent clinical condition in dentistry. Macrophages play pivotal roles in pulpitis immunopathology, while dental pulp stem cells (DPSCs) serve as key effectors in pulp tissue repair and immune regulation. Although mesenchymal stem cells are known to regulate immunity through mitochondrial transfer, this mechanism remains unexplored in pulpitis. This study investigated how mitochondrial transfer influences pulpitis progression and resolution.

METHODOLOGY: To investigate DPSC-macrophage mitochondrial transfer and its role in polarisation of macrophages, Lipopolysaccharide-stimulated cocultures were established. Transfer dynamics were analysed by fluorescence microscopy and flow cytometry. Macrophage polarisation (assessed via quantitative real-time polymerase chain reaction (qRT-PCR)/flow cytometry) in the cocultures was detected after mitochondrial transfer agonist/inhibitor treatment. Macrophage polarisation (assessed via qRT-PCR/flow cytometry) and mitochondrial function (reactive oxygen species production, membrane potential) were compared between mitochondria-receiving (Mito+) and non-receiving (Mito-) macrophages. Immunometabolic profiles (itaconate/succinate) were evaluated by qRT-PCR/immunofluorescence. Human dental pulp explants and experimental rat pulpitis models demonstrated the anti-inflammatory and reparative effects of mitochondrial transfer agonists. Data were analysed by one-way ANOVA and unpaired t-tests (α = 0.05).

RESULTS

Mitochondrial transfer from DPSCs to macrophages reduced during inflammation. Pharmacological inhibition of mitochondrial transfer exacerbated M1 macrophage polarisation, whereas its enhancement promoted M2 polarisation. Mito+ macrophages exhibited stronger M2 polarisation, improved mitochondrial function, and reduced itaconate/succinate metabolism compared to Mito- cells. Notably, using the inflamed dental pulp explant and the experimental rat pulpitis model, we demonstrated that augmenting mitochondrial transfer can effectively alleviate pulpitis and promote repair.

CONCLUSIONS

Mitochondrial transfer from dental pulp stem cells to macrophages via tunnelling nanotubes improved macrophage metabolic profiles. Enhanced mitochondrial transfer promoted M2 macrophage polarisation, thereby alleviating pulpal inflammation and promoting repair.