Lymphocyte-Derived Exosomal MicroRNAs Promote Pancreatic β Cell Death and May Contribute to Type 1 Diabetes Development

Type 1 diabetes is an autoimmune disease initiated by the invasion of pancreatic islets by immune cells that selectively kill the β cells. We found that rodent and human T lymphocytes release exosomes containing the microRNAs (miRNAs) miR-142-3p, miR-142-5p, and miR-155, which can be transferred in active form to β cells favoring apoptosis. Inactivation of these miRNAs in recipient β cells prevents exosome-mediated apoptosis and protects non-obese diabetic (NOD) mice from diabetes development. Islets from protected NOD mice display higher insulin levels, lower insulitis scores, and reduced inflammation. Looking at the mechanisms underlying exosome action, we found that T lymphocyte exosomes trigger apoptosis and the expression of genes involved in chemokine signaling, including Ccl2, Ccl7, and Cxcl10, exclusively in β cells. The induction of these genes may promote the recruitment of immune cells and exacerbate β cell death during the autoimmune attack. Our data point to exosomal-miRNA transfer as a communication mode between immune and insulin-secreting cells. [Display omitted] •T lymphocytes release exosomes containing specific microRNAs•T lymphocyte exosomes can transfer microRNAs to rodent and human pancreatic β cells•The transferred microRNAs trigger chemokine expression and apoptosis of β cells•Blockade of microRNAs transferred in β cells decreases diabetes incidence in NOD mice Guay et al. show that T cells release exosomes containing specific microRNAs that trigger chemokine expression and apoptosis in recipient pancreatic β cells in type 1 diabetes. Inactivation of miR-142-3p/-5p and miR-155 in β cells results in higher insulin levels, lower insulitis scores, and reduced inflammation and protects NOD mice from diabetes development.