The neonatal ARDS mouse model was established as previously described, with minor revision [17 (link)]. Thirty neonatal C57BL/6 mice were randomly divided into a normal saline control group (n=10) and an LPS-induced group (n=20). Mice in the LPS-induced group were injected intraperitoneally with LPS (10 mg/kg) purchased from Sigma-Aldrich (St. Louis, MO). Mice in the normal saline control group were injected with an equal volume of sterile saline. Ten mice in the LPS-induced group were intraperitoneally injected with 1 μg of recombinant IL-37 (R&D Systems, Shanghai, China) per mouse [15 (link)] 2 h before LPS injection. The other 10 LPS-induced mice and the 10 control mice received the same weight-based volume of vehicle. All mice were sacrificed 72 h after LPS or saline treatment and blood samples were collected.