On the other hand, elastase-induced Dio2 up-regulation did not reflect the changes in protein expression both on days 1 and 4 (Supplementary Figure S1C–F), with one showing that the intratracheal administration of T3 improved pulmonary pathology in the IPF model mice [20] and the other showing that T3 indirectly played a pulmonary protective role in the acute lung injury (ALI) model mice [25]; it is possible that the intratracheal administration of T3 to elastase-induced COPD mice improves COPD pathology. Here, DIO2 is linked to chronic obstructive pulmonary disease.