**1.5 MiR-126**

The relative levels of miR-126 in the peripheral blood of children with asthma were found to be both elevated and significantly correlated with the severity of the disease and also negatively correlated with IFN-γ levels, which has great potential for diagnosis, especially in severe asthma, with an AUC of 0.909 [41], as one of the diagnostic biomarkers for asthma. The up-regulated levels of miR-126 were positively correlated with the severity of lung function [42], which may be associated with IL-13 [41]. But they have higher small airway reversibility [43]. Concerning animal experiments, Mattes found in an ovalbumin (OVA)-induced asthma model that miR-126 blockade led to enhanced expression of POU structural domain class 2 associated factor 1, one that activates the transcription factor PU.1, which alters TH2 cell function by negatively regulating GATA3 expression [44]. GATA3 may facilitate Th0 to Th2 differentiation. During the construction of the chronic airway inflammation model, the expression of multiple miRNAs, especially miR-126, increased in the airway wall early in the model establishment, and when administered with miR-126 antagonists, inhibited airway eosinophil recruitment. In contrast, later in the model construction, miR-126 expression decreased, and continued administration of miR-126 antagonists affected longterm chronic inflammation of the airway walls with little change [45]. These results indicate that miR-126 plays a significant role early in pathological evolution and that early intervention should be of little clinical significance if it reaches a terminal stage.
