SMAD2 and bronchopulmonary dysplasia: In a fetal sheep lung injury model induced by in utero LPS injection, it was found that the Cav-1 gene and protein levels both decreased, and the Smad2/3, Stat, and a-SMase/ceramide signaling pathways were activated, indicating that the downregulation of Cav-1 and activation of these signaling pathways may together contribute to the occurrence of BPD [30].