Negative regulation of Hif1a expression and TH17 differentiation by the hypoxia-regulated microRNA miR-210

The microRNA miR-210 is a signature of hypoxia. We found robust increase in the abundance of miR-210 (>100-fold) in activated T cells, especially in the TH17 lineage of helper T cells. Hypoxia acted in synergy with stimulation via the T cell antigen receptor (TCR) and coreceptor CD28 to accelerate and increase Mir210 expression. Mir210 was directly regulated by HIF-1α, a key transcriptional regulator of TH17 polarization. Unexpectedly, we identified Hif1a as a target of miR-210, which suggested negative feedback by miR-210 in inhibiting HIF-1α expression. Deletion of Mir210 promoted TH17 differentiation under conditions of limited oxygen. In experimental colitis, miR-210 reduced the abundance of Hif1a transcripts and the proportion of cells that produced inflammatory cytokines and controlled disease severity. Our study identifies miR-210 as an important regulator of T cell differentiation in hypoxia, which can limit immunopathology.