Effect of mesenchymal stem cell‐derived exosomes on the induction of mouse tolerogenic dendritic cells

Dendritic cells (DCs) orchestrate innate inflammatory responses and adaptive immunity through T‐cell activation via direct cell–cell interactions and/or cytokine production. Tolerogenic DCs (tolDCs) help maintain immunological tolerance through the induction of T‐cell unresponsiveness or apoptosis, and generation of regulatory T cells. Mesenchymal stromal cells (MSCs) are adult multipotent cells located within the stroma of bone marrow (BM), but they can be isolated from virtually all organs. Extracellular vesicles and exosomes are released from inflammatory cells and act as messengers enabling communication between cells. To investigate the effects of MSC‐derived exosomes on the induction of mouse tolDCs, murine adipose‐derived MSCs were isolated from C57BL/6 mice and exosomes isolated by ExoQuick‐TC kits. BM‐derived DCs (BMDCs) were prepared and cocultured with MSCs‐derived exosomes (100 μg/ml) for 72 hr. Mature BMDCs were derived by adding lipopolysaccharide (LPS; 0.1μg/ml) at Day 8 for 24 hr. The study groups were divided into (a) immature DC (iDC, Ctrl), (b) iDC + exosome (Exo), (c) iDC + LPS (LPS), and (d) iDC + exosome + LPS (EXO + LPS). Expression of CD11c, CD83, CD86, CD40, and MHCII on DCs was analyzed at Day 9. DC proliferation was assessed by coculture with carboxyfluorescein succinimidyl ester‐labeled BALB/C‐derived splenocytes p. Interleukin‐6 (IL‐6), IL‐10, and transforming growth factor‐β (TGF‐β) release were measured by enzyme‐linked immunosorbent assay. MSC‐derived exosomes decrease DC surface marker expression in cells treated with LPS, compared with control cells ( ≤ .05). MSC‐derived exosomes decrease IL‐6 release but augment IL‐10 and TGF‐β release (p ≤ .05). Lymphocyte proliferation was decreased (p ≤ .05) in the presence of DCs treated with MSC‐derived exosomes. CMSC‐derived exosomes suppress the maturation of BMDCs, suggesting that they may be important modulators of DC‐induced immune responses.