Stem/progenitor cell populations resident in the lung and the role of stromal support in their maintenance and differentiation

Abstract

Lungs are vital organs for respiration, being enabled by their complex three-dimensional organization [1]. Airway tubes bifurcate into millions of highly vascularized alveolar sacs, the alveoli, which are responsible for gas exchange. The gas exchange surface of the lungs makes up one of the largest surface areas of the human body. The alveoli receive air from the conducting airways, starting in the trachea, bifurcating into the bronchi and bronchioles, and ending in the terminal bronchioles, which divide into the alveolar ducts from which the alveoli arise. The aim of this chapter is to provide an overview of the progenitors in adult lung tissue and the regulation of their maintenance and differentiation by the microenvironment during lung developmental as well as repair processes, when developmental pathways are often reactivated. As most work has been done in mouse studies, the current knowledge from animal studies will be summarized and translated to what is known from human lungs. In order to understand the regenerative processes in the lung, we will first provide insight into the complex three-dimensional organization and composition of the lung, its function, and the processes involved in lung development.