Ather Adnan

Introduction: Type 1 Diabetes (T1D) is a complex autoimmune disease characterized by T-cell driven destruction of pancreatic β-cells in the islets of Langerhans and resultant hyperglycemia¹. The pathogenesis of T1D involves presentation of normally cryptic β-cell autoantigens and aberrant activation rather than suppression of immune cells^1,2. The only treatment for T1D is exogenous insulin therapy, which does not target the etiology of the disease¹. Extracellular vesicles derived from mesenchymal stem cells (MSC-EVs) hold therapeutic potential as they retain the immunomodulatory properties of MSCs while having the advantage of being cell-free and more predictable^3,4. The mechanism by which MSC-EVs suppress T1D was investigated. Methods: MSCs and peripheral blood mononuclear cells (PBMCs) were obtained from healthy donors⁵. EVs were obtained from MSCs via ultracentrifugation^5,6. Dendritic cells (DCs) were obtained from PBMCs via immunomagnetic isolation and matured by exposure to lipopolysaccharide (LPS) in the presence or absence of MSC-EVs and DC co-stimulatory markers were quantified via flow cytometry⁵. Supernatants from co-cultures of MSC-EVs with mature DCs (mDCs), as well as T cells with mDCs or mDCs + MSC-EVs, were analyzed via ELISA to measure cytokine concentration⁵. A one-way mixed lymphocyte reaction assay was performed using splenocytes from C57BL/6 and BALB/c mice, in the presence or absence of EVs, and flow cytometry was used to quantify DC co-stimulatory markers⁶. Splenocytes vs splenocytes + MSC-EVs were transfused from NOD to NOD/scid mice and the onset to T1D (two consecutive >250 mg/dL blood glucose tests) was measured⁶. Results: mDCs co-cultured with MSC-EVs showed significant reduction in co-stimulatory molecules CD80, CD83, and CD38 compared to culturing without MSC-EVs. Co-culture of mixed splenocytes with EVs showed dose-dependent reduction of co-stimulatory molecules CD80, CD40, CD86, and MHC II compared to co-culturing without MSC-EVs⁵. Supernatants derived from co-cultures of mDCs with MSC-EVs compared to without MSC-EVs showed reduced IL-6 and IL-12 and increased TGF-β⁶. Supernatants derived from co-cultures of T cells with MSC-EV-conditioned mDCs compared to non-conditioned mDCs showed reduced IFN-γ, IL-6⁵. Infusion of NOD-derived splenocytes with, vs without NOD-derived MSC-EVs, into NOD/scid mice significantly delayed the onset of T1D⁶. Conclusions: MSC-EVs suppress the immune response in T1D by inducing a regulatory phenotype in DCs, evidenced by the reduction of co-stimulatory molecules and alterations in their secreted cytokine profiles. They have been shown to delay T1D onset in vivo. MSC-EVs are therefore a potential therapeutic agent for T1D.

1. Katsarou A, Gudbjornsdottir S, Rawshani A, et al. Type 1 diabetes mellitus. Nat Rev Dis Primers 2017;3:17016.
2. Clark M, Kroger CJ, Tisch RM. Type 1 Diabetes: A Chronic Anti-Self-Inflammatory Response. Front Immunol 2017;8:1898.
3. Xv J, Ming Q, Wang X, et al. Mesenchymal stem cells moderate immune response of type 1 diabetes. Cell Tissue Res 2017;368:239-48.
4. Wang M, Yuan Q, Xie L. Mesenchymal Stem Cell-Based Immunomodulation: Properties and Clinical Application. Stem Cells Int 2018;2018:3057624.
5. Reis M, Mavin E, Nicholson L, Green K, Dickinson AM, Wang XN. Mesenchymal Stromal Cell-Derived Extracellular Vesicles Attenuate Dendritic Cell Maturation and Function. Front Immunol 2018;9:2538.
6. Shigemoto-Kuroda T, Oh JY, Kim DK, et al. MSC-derived Extracellular Vesicles Attenuate Immune Responses in Two Autoimmune Murine Models: Type 1 Diabetes and Uveoretinitis. Stem Cell Reports 2017;8:1214-25.