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

Abstract 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.