Abstract
Background
Infant respiratory distress syndrome (IRDS) is a syndrome in premature infants caused by developmental insufficiency of pulmonary surfactant production and structural immaturity in the lungs. Babies born before 29 weeks of gestation have about 60% chance of developing IRDS, which is the leading cause of death in premature infants. In order to improve the survival rate of premature infants, steroid, such as dexamethasone, are widely used clinically for the pregnant women, who has an unavoidable sign of preterm birth at 24 to 34 weeks of gestation, to accelerate fetal lung maturation and producing pulmonary surfactant, effectively. However, the pharmacological rationale for the therapeutic effects of dexamethasone in lung maturation and producing pulmonary surfactant was still unclear. Therefore, establishing a model to reveal the biological function of dexamethasone in lung maturation will be necessary. Recently, we have identified a rare population of mouse pulmonary stem/progenitor cells (mPSCs) expressed with a specific cellular surface marker, coxsackievirus/adenovirus receptor (CAR), and named as CAR+/mPSCs. By our studies, CAR+/mPSCs could be effectively enriched and isolated for a pure population (>1,000,000 cell numbers), which were able to differentiate almost in synchronized pace into type-I pneumocytes in 7-9 days. We hypothesize that the differentiation process could be used to evaluate the therapeutic effects of dexamethasone in lung maturation and surfactant production, indicated by type-I pneumocytes formation.
Methods
In the timeline of the CAR+/mPSCs differentiation, dexamethasone and TGF-β inhibitors are added to investigate the α-SMA expression by IF and qPCR.
Results
Our studies showed that dexamethasone could down-regulate α-SMA expression, and promote the morphogenesis of type-I pneumocytes. Moreover, our studies also found that TGF-β inhibitor had the synergistic effects to up-regulate tight junction protein claudin-18 and ZO-1, which implies a typical epithelial phenotype for alveolar type-I pneumocytes sheet in the differentiation process.
Conclusions
TGF-β signaling pathways plays an important role in the regulation of α-SMA expression and tight junction in type-I pneumocytes. Taken together, CAR+/mPSCs differentiation cell model could help pharmacological studies to reveal the therapeutic effects of dexamethasone and to evaluate a more effective treatment combination for lung development.
