Macrophage-derived exosomes rescue the TNF-ɑ-suppressed osteo-/cementogenic differentiation of hPDLCs

Objective Inflammatory stimuli compromise the differentiation potency of human periodontal ligament cells (hPDLCs). Macrophage-derived exosomes (M-Exo) play a role in several aspects of cellular activity. This study investigated how M-Exo contributes to the osteo-/cementogenic differentiation of hPDLCs under inflammation and the mechanism involved. Methods M-Exo was identified by transmission electron microscopy, western blotting (WB), and dynamic light scattering. The internalization of M-Exo by hPDLCs was observed. After M-Exo treatment, the osteo-/cementogenic markers were detected by RT-qPCR and WB, and alkaline phosphatase (ALP) activity by ALP staining. Tumor necrosis factor alpha (TNF-ɑ) was applied to simulate inflammation. The rescue effect of M-Exo on TNF-ɑ-suppressed differentiation was validated. The p38 MAPK pathway activity was tested and a specific inhibitor was applied to explore the mechanism. Results M-Exo was successfully isolated, identified and internalized by hPDLCs. M-Exo enhanced the osteo-/cementogenic differentiation of hPDLCs, as indicated by upregulated osteo-/cementogenic markers and elevated ALP activity. Moreover, TNF-ɑ inhibited the differentiation capabilities of hPDLCs, on which M-Exo showed a rescue effect. M-Exo activated the p38 MAPK pathway and SB203580 attenuated its promotion effect. Conclusion This study showed that M-Exo ameliorated the TNF-ɑ-suppressed osteo-/cementogenic differentiation of hPDLCs partly through the p38 MAPK pathway.