Hypoxic stem cells from apical papilla-derived exosomes enhance dental pulp stem cells migration and differentiation via mitochondrial activation.

BACKGROUND/PURPOSE: Stem cells from apical papilla (SCAPs) and dental pulp stem cells (DPSCs) play critical roles in dental tissue regeneration. Although intercellular communication through exosomes is known to influence stem cell regulation, the effects of exosomes derived from hypoxic SCAPs on the migration and odontogenic differentiation of DPSCs have not been elucidated. This study aimed to investigate SCAPs derived exosomes mediated modulation of DPSCs biological functions under hypoxic conditions. MATERIALS AND METHODS: Exosomes were obtained from SCAPs cultured under normoxic or hypoxic conditions. DPSCs were treated with these exosomes, and their migration capacity was evaluated using scratch and transwell assays. Odontogenic differentiation was assessed via gene/protein expression analysis and alizarin red / alkaline phosphatase (ALP) staining. Mitochondrial dynamics and energy metabolism were analyzed using transmission electron microscopy, seahorse assays, and Mitotracker red staining. RESULTS: Hypoxic SCAPs-derived exosomes exhibited comparable morphology and size to normoxic exosomes but enhanced DPSCs migration and odontogenic differentiation. Hypo-Exo promoted mitochondrial fusion in DPSCs, evidenced by increased mitofusin 2 (MFN2) / translocator of the outer mitochondrial membrane 20 (TOM20) expression and augmented mitochondrial oxygen consumption rates. Rotenone inhibition of mitochondrial metabolism abrogated Hypo-Exo-induced migration and differentiation, confirming the critical role of mitochondrial fusionmediated energy metabolism in this process. CONCLUSION: Hypoxic SCAPs-derived exosomes enhance DPSCs migration and odontogenic differentiation through mitochondrial fusion. These findings reveal a novel "exosome-mitochondria" regulatory axis, providing a mechanistic basis for developing hypoxia-engineered exosome therapies in dental regenerative medicine.