Alveolar epithelial cell differentiation and apoptosis: effects of preterm birth, corticosteroids and stretch.

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In the lung, gas exchange takes place in small terminal airsacs called alveoli. The internal surface of the alveoli are lined with 2 types of specialist cells, the type-I and type-II cells. Both cells are essential for the normal functioning of the lung; type-I cells provide a thin barrier for the gas exchange, whereas type-II cells produce the surface-active material, surfactant. In order to survive after birth, the lungs of the newborn must have appropriate numbers of each of these cell types. However, babies that are born very prematurely have few, if any, mature cells as most are non-specialised cells that possess none of the characteristics of mature type-I and type-II cells. Therefore, the lungs of very preterm babies have low levels of surfactant, are prone to injury and infection and are not efficient in the exchange of oxygen and carbon dioxide. As such, these infants are at high risk of developing chronic lung disease which is a serious debilitating disease that has long term health implications. We believe that the non-specialised cells are more prone to injury and cell death than mature cells which makes the very premature infant more susceptible to the development of chronic lung disease. As the survival and respiratory health of these infants depends upon most type-I and type-II cells maturing after birth, it is critical to understand the factors that regulate their maturation. This information will allow the development of treatments that can enhance the maturation of these cell types. This application is focused towards understanding the factors that control maturation of type-I and type-II cells, as well as the role of the non-specialised cells in the development of chronic lung disease in babies that are born very prematurely.