Accumulating evidence indicates that treatment using extrace

Accumulating evidence indicates that treatment using extracellular vesicles (EVs) have multiple advantages over cell therapy, because EVs are stable in the circulation without losing function and exhibit a superior safety profile (Vader et al., 2016). In particular, MSCs are an attractive source of EVs because they secrete a large number of therapeutic factors, including cytokines, chemokines, and microRNAs in EVs (Aggarwal and Pittenger, 2005; Baglio et al., 2015; Jurewicz et al., 2010; Lee et al., 2011; Meisel et al., 2004; Phinney et al., 2015; Rafei et al., 2008; Sato et al., 2007; Wei et al., 2013). In addition, since MSCs have a remarkable tendency to home to injured tissues (Kidd et al., 2009; Ortiz et al., 2003; Rojas et al., 2005), the EVs produced by MSCs may retain the homing properties of their parent Volasertib (Hood et al., 2011; Lai et al., 2013). Indeed, a number of studies have shown that EVs produced by MSCs exert their therapeutic effects in several disease models (Chen et al., 2015; Doeppner et al., 2015; Heldring et al., 2015; Monsel et al., 2016; Ophelders et al., 2016; Rani et al., 2015; Vader et al., 2016; Wen et al., 2016), suggesting that MSC-derived EVs may be a promising alternative to cell therapy for immune-mediated diseases. Our group has previously demonstrated that MSCs induce immune tolerance by activating the endogenous immune regulatory system of the recipients and thereby suppress autoimmune responses in models of type 1 diabetes (T1D) (Kota et al., 2013) and experimental autoimmune uveoretinitis (EAU) (Ko et al., 2016; Lee et al., 2015; Oh et al., 2014). Therefore, here, we investigated whether MSC-derived EVs are as effective in modulating immune responses as MSCs in two models for autoimmune diseases: T1D and EAU.
Results
Discussion Here, we demonstrate the therapeutic potential of MSC-derived EVs in two mouse models of autoimmune diseases involving the pancreas and the eye. Consistent with our previous observations with MSCs (Ko et al., 2016; Kota et al., 2013), MSC-derived EVs suppressed Th1 development and inhibited activation of APCs and T cells. In addition, they also increased expression of the immunosuppressive cytokine IL-10 and suppressed Th17 cell development. IL-10 has been considered an immunosuppressive cytokine because of its association with multiple suppressive immune-cell populations, such as Tregs and regulatory DCs, as well as its inhibition of antigen presentation and immune-cell activation (Ouyang et al., 2011; Zhang et al., 2016). Given our results of increased IL-10 and the hypoactive phenotype of DCs at the early time point of the MLR (day 2), MSC-derived EVs might induce IL-10-expressing regulatory DCs, and thereby, regulatory DCs subsequently suppress Th1 and Th17 cell development without inducing Tregs. Furthermore, Th1 cytokine production is characteristic of many organ-specific autoimmune diseases (Alleva et al., 2001; Crane and Forrester, 2005; Jun et al., 1999; Weaver et al., 2001), and IL-17A and/or IL-17F are responsible for development of inflammation in many disorders, especially in autoimmune diseases (Bettelli et al., 2007; Jain et al., 2008; Langrish et al., 2005; Nakae et al., 2002). Therefore, our data raise the possibility that MSC-derived EVs might be beneficial for treating autoimmune diseases where Th1 and Th17 cells play a critical role. The immunosuppressive effect of MSCs is mediated by a range of immunosuppressive mediators such as NO, IDO, prostaglandin E2 (PGE2), TNF-α-simulated gene 6 (TSG-6), CCL-2, or PD-L1 (Aggarwal and Pittenger, 2005; Jurewicz et al., 2010; Lee et al., 2011; Meisel et al., 2004; Rafei et al., 2008; Sato et al., 2007; Wei et al., 2013). Since MSCs need to be activated to increase the expression of these therapeutic factors by inflammatory cytokines such as TNF-α or IFN-γ (Lee et al., 2009a; Wei et al., 2013), EVs isolated from unactivated MSCs are likely to express lower levels of therapeutic factors. To obtain EVs for our study, we incubated MSCs in a chemically defined protein-free medium, which activates MSCs to increase therapeutic proteins, including TSG-6, and also provides a stable environment for producing EVs (Kim et al., 2016). Therefore, the EVs produced in our study might have advantages over the EVs produced by unactivated MSCs. Moreover, MSCs cultured in serum-free media would be ideal for a clinical-grade therapeutic product.