SMAD2 and acute respiratory distress syndrome: Furthermore, we thoroughly demonstrated that adipose-derived exosomal miR-122-5p promotes protection of the pulmonary endothelial barrier by inhibiting EndMT and oxidative stress through down-regulation of the TGF-β1/TGF-βR1/Smad2 pathway, which may contribute to the protective nature and underlying mechanism of the obesity paradox in ARDS and indicate promising prospects for adipose-derived modified exosomes in cell-free therapies for ARDS.