SMAD2 and bronchopulmonary dysplasia: The structural changes were associated with elevated expressions of TGFβ3 and SMAD2 proteins in lung tissue samples of rat pups exposed to hyperoxia and these elevations were restored by VPA treatment which is in line with clinical data where increased levels of TGFβ isoforms in bronchoalveolar lavage fluid of preterm infants were associated with the severity of BPD [22].