Exosomes From TNF-alpha-treated GMSCs Induce M2 Macrophage Polarization

Objectives: To date, clinical utility of stem cells for periodontal regeneration have been investigated. Besides its differentiation capacities, mesenchymal stem cells (MSCs) are also known to possess anti-inflammatory function. Macrophages plays central role in resolution of inflammation, and its phenotype can be characterized as pro-inflammatory (M1) or immunomodulatory and tissue remodeling (M2). We previously demonstrated that MSCs from human gingiva (GMSCs) can induce M2 polarization of macrophages. Recent studies have shown that the mitochondrial transfer and exosome from MSCs contribute to tissue repair. To further explore the mechanism of GMSC-induced M2 macrophage polarization, we investigated the effect of mitochondrial transfer and exosome from GMSCs on macrophage phenotype.
Methods: Macrophages were obtained by culturing human monocytic THP-1 cells with PMA, and CD14+ monocytes from PBMC with M-CSF. To confirm the mitochondrial transfer from hGMSCs to macrophages, mitochondria in GMSCs were pre-stained with MitoTracker® probe. Mitoception, an artificial mitochondrial transfer method in vitro was also utilized. After pre-treated with inflammatory (LPS and TNF-a) and anti-inflammatory (IFN-g and aspirin) stimuli, exosome from GMSCs were prepared by Exo-spin™ column purification. The expressions of M2 marker genes (CD163, 204 and 206) were analyzed by FACS.
Results: Confocal microscopy demonstrated the mitochondrial transfer from hGMSCs to macrophages. Mitoception experiments revealed that mitochondrial transfer from hGMSCs contributes to macrophage maturation, while it didn’t induce M2 macrophage polarization. However, exosome from hGMSCs enhanced the expression of M2 marker, and inflammatory stimulations in GMSCs increased the effect. Exosome from TNF-a treated GMSCs induced more M2 macrophage polarization than LPS treatment.
Conclusions: While the mitochondrial transfer from hGMSCs contributed macrophage differentiation, exosome from TNF-a stimulated GMSCs significantly elicited macrophage function toward the M2 phenotype. These results suggest new supportive background for MSC-based periodontal therapy.