Expression and significance of markers from lung epithelium cells in neonatal rats with bronchopulmonary dysplasia

Abstract

Objective To investigate the dynamic expression of mRNA and protein of surfactant protein C (SPC), E-cadherin (E-cad), N-cadherin (N-cad) and α-smooth muscle actin (α-SMA) and elucidate the significance of epithelial-mesenchymal transition (EMT) in a newborn rat model of Bronchopulmonary dysplasia(BPD). Methods A newborn rat model of BPD in hyperoxia was established, and a control group exposed to air was established.Lung tissue was collected on days 3, 7, 14, and 21, respectively.Alveolar development was evaluated by radical alveolar counts(RAC), including thickness of alveolar septum, ratio of alveolar and septa.Real-time PCR and Western-blot were used to detect levels of markers of epithelial cells (SPC, E-cad) and interstitial cells (N-cad, α-SMA) in AT2 and protein expression. Results On day 7, 14, and 21, compared with the control group, RAC(7.38±0.92, 9.25±0.70, 9.88±0.99) and alveolar area/pulmonary septal area ratios(A/S)(2.53±0.02, 3.34±0.09, 3.96±0.13) were all higher in BPD group[RAC(5.88±0.83, 5.14±0.83, 4.38±0.52) and A/S (1.88±0.03, 1.95±0.03, 1.89±0.02)](all P<0.05); the alveolar septum(8.53±0.04, 10.75±0.46, 13.55±0.84) in BPD group were thicker than those (5.77±0.09, 4.40±0.12, 3.67±0.18) in the control group (all P<0.01). The expressions of SPC and α-SMA in BPD group were significantly higher than those in the control group on day 14 and 21(all P<0.05). The level of E-cad mRNA(2.43±0.60, 2.59±0.48, 3.37±0.53) and protein(18.39±1.77, 18.29±1.52, 11.48±1.72) for E-cad were higher in the control group than those(mRNA: 1.48±0.55, 1.57±0.48, 1.12±0.45; protein: 9.50±1.38, 8.57±1.06, 8.22±1.31) in BPD group was lower(P<0.05), while the level of N-cad was significantly higher(P<0.05) on day 7, 14, and 21. Conclusions In the development of BPD, the markers of lung epithelial cells were down regulation, while the markers of interstitial cells were up-regulation, and these findings suggest that EMT from lung epithelial cells contributes to the occurrence of BPD. Key words: Alveolar epithelial type Ⅱ cell; Special marker; Epithelial-mesenchymal transition; Bronchopulmonary dysplasia; Rat, newborn