Citation

Background
Autoimmune uveitis is a sight-threatening intraocular inflammation mainly caused by immune dysregulation. The development of safe and effective therapeutic approaches is urgently needed. Small extracellular vesicles (sEVs) derived from mesenchymal stem cells (MSCs) have been demonstrated to inhibit autoimmune responses; however, the immunosuppressive effect of MSC-sEVs is too weak for clinical transfer. In the current study, we investigated the therapeutic effect of IL-10-overexpressing MSC-sEVs (sEV-IL10) on experimental autoimmune uveitis (EAU) and studied the underlying mechanism.

Methods
Mice were randomly grouped and received a single tail vein injection of different sEVs (50 μg) or PBS on day 11 post-immunization. The clinical and histological scores were graded, and the percentage of T helper cell was measured. To investigate the effect of sEVs on the proliferation of T-cells and the differentiation of Th1, Th17 and Treg cells, T-cells were cocultured with sEVs under the corresponding culture conditions. After labeled with PKH-26, sEVs were traced both in vivo and in vitro.

Results
Compared with normal or vector sEV-treated groups, mice in the sEV-IL10-treated group had lower clinical and histological scores with lower percentages of Th1 and Th17 cells in the eyes and higher percentages of Treg cells in the spleen and draining lymph nodes (LN). Furthermore, sEV-IL10 enhanced the suppressive effect of MSC-sEVs on the proliferation of T-cells and differentiation of Th1 and Th17 cells, whereas upregulated the differentiation of Treg cells. Both in vivo and in vitro experiments demonstrated that MSC-sEVs were rapidly enriched in target tissues and internalized by T-cells.

Conclusion
These results suggested that sEV-IL10 effectively ameliorates EAU by regulating the proliferation and differentiation of T-cells, indicating sEVs as a potential novel therapy for autoimmune uveitis or other autoimmune diseases.