Mesenchymal stem cell exosomes promote immunosuppression of regulatory T cells in asthma

Mesenchymal stem cells (MSCs) and regulatory T cells (Tregs) are both potent immune-modulators. The aberrant proliferation and function of Tregs plays an important role in the development of asthma. Our previous studies have demonstrated the role of MSCs in promoting proliferation and immune-modulating of Tregs, as well as alleviating airway inflammation of asthmatic mice. In the present study, we isolated exosomes secreted by MSCs and investigated their immunomodulation effect on peripheral blood mononuclear cells (PBMCs) of asthmatic patient. We found that MSC exosomes upregulated IL-10 and TGF-β1 from PBMCs, thus promoting proliferation and immune-suppression capacity of Tregs. Furthermore, antigen presenting cells (APCs) but not CD4+ T cells-dependent pathway was shown to be possible mechanism involved in MSC exosome-mediated regulation. Our data elucidated the key role of exosomes in immune-modulation of MSCs, and suggested the therapeutic potential of MSC exosomes for asthma.