Chapter 4: Lung Stem and Progenitor Cells

Both the conducting airways (the bronchiolar and tracheobronchial airways) and the gas exchange airspaces (the alveolar regions) are the two major distinct compartments of the lung. Each of these regions contains distinct types of epithelial cells with characteristic compartments of stem and progenitor cells that include epithelial and alveolar stem/progenitor cells, stem and progenitor cells of the bronchi and trachea, and lung mesenchymal stem and progenitor cells such as airway smooth muscle (ASM) stem and progenitor cells and vascular stem and progenitor cells. In addition, the cellular plasticity of different lung-specific stem cells is currently an emerging field of research. Many recent studies have, therefore, used lineage tracing to determine distinct populations of epithelial stem and progenitor cells in the lung. Moreover, stem cells are likely involved in some major lung diseases. Yet, little is known about the functions of different stem cell types in the lung, despite common agreements that lung stem cells may have a major role in the repair and regeneration of the lung. In this chapter, we describe different types of stem and progenitor cells in the lung and mechanisms that regulate both their development, including their proliferation and differentiation, and plasticity during lung morphogenesis, as well as stem cell contribution to lung repair and regeneration. Furthermore, we describe stem cell-related diseases in the lung and stem cell contributions to both the immunomodulation of lung diseases and lung repair and regeneration, as well as the potential of stem cell-based therapies in different lung diseases.