Respiratory stem cells and progenitors: overview, derivation, differentiation, carcinogenesis, regeneration and therapeutic application.

Recently, research of stem cells has garnered great attention and has shown promise by changing the view of traditional therapeutics, with broad impact on gene therapy, carcinogenesis, organ development, tissue injury, regeneration and almost all aspects of the life cycle and all living systems. A century's scientific progress has significantly improved controls for infectious diseases and many other disorders. However, many remaining problems (i.e. cancer, AIDS, diabetes, Parkinson's disease and Marburg infection) appear to be even harder than those that have already been solved. In particular, respiratory stem cell research has been less active and has moved more slowly than that of many other organs. This is probably due to the complexity of the lung and airway system, particularly owing to the many types of cells (>40), unique structures and functions, and technical difficulty in analyzing this system at the genetic, biochemical, molecular and cellular level. Compared with other epithelial cells (i.e., gastrointestinal epithelium), respiratory epithelia have a very low turnover rate and minimal regenerative activity. This review will discuss the current state of pulmonary stem cells, their origin, development, differentiation, and regenerative application, with a particular focus on potential impact on cancer development and lung injury repair.