Mir-20b-Induced Increase in Myeloid-Derived Suppressor Cells in the Lungs of Mice with Chronic Asthma.

Bronchial asthma is a common chronic airway inflammatory disease. MicroRNAs (miRNAs) play an important role in the pathogenesis of asthma. We have previously shown that miR-20b can inhibit airway inflammation in asthmatic mice, but the exact mechanism is unknown. In the present study, we show that administration of nasal drops containing miR-20b induced an increase in the percentage of Gr1(+)CD11b(+) myeloid-derived suppressor cells (MDSCs) in lung tissue from asthmatic mice, and the content of TGF-β in lung tissues also increased after treatment. However, there was no significant change in the number of Gr1(+)CD11b(+) MDSCs in bone marrow, peripheral blood, or spleens of asthmatic mice receiving the miR-20b nasal drip compared with untreated asthmatic mice. Since MDSCs originate in the bone marrow, these results suggest that miR-20b nasal drops may promote the increase of Gr1(+)CD11b(+) MDSCs in the lungs of asthmatic mice by the mechanism of inducing expansion.