Transforming growth factor β1 may play an important role in the pathogenesisof BPD so isolation of lung MSCs within the first week of life can predict thedevelopment of BPD and can serve as a biomarker for development of thisdisease that may lead to development of better therapeutic modalities intreating BPD. We are testing whether Transforming growth factor β1 assayfrom the tracheal aspirates of preterm infants during the first week of lifecorrelates with BPD which will be defined as the need for supplemental oxygento maintain acceptable oxygen saturation by pulse oximeter at 36 weekspostmenstrual age. This definition includes infants with both moderate andsevere BPD. Tracheal aspirates were detected from 121 preterm neonates onmechanical ventilation, during the first week, and were examined forTransforming growth factor β- 1 assay.Bronchopulmonary dysplasia (BPD) was detected in 23 preterms (24.5%) andTransforming growth factor β1 was positively correlated with occurrence ofBPD, where the median of TGF-β1 was 4, 173.91 (± 864.344)pg/ml in the BPDgroup and 3,705.76 (± 540.481) in the No BPD group with a significantly pvalue 0.021 .