Total RNA from freshly frozen lungs was extracted with TRIzol reagent (Invitrogen) according to the manufacturer's instructions. Then the RNA concentration and purity of each sample were assessed using NanoDrop 2000, and their integrity was verified via Agilent2100/LabChip GX Assay, with an OD260/OD280 ratio of 1.8 to 2.0 deemed suitable for further experimentation.RNA-seq library was prepared and sequencing was carried out on an Illumina platform.