In contrast to a prior emphasis on the finality of cell fate decisions in developmental systems, cellular plasticity is now emerging as a general theme in the biology of multiple adult organ systems. In the lung, lineage tracing has been used to identify distinct epithelial stem and progenitor cell populations. These cells, together with their differentiated progeny, maintain a stable identity during steady state conditions, but can display remarkable lineage plasticity following injury. This Review summarizes our current understanding of the different cell lineages of the adult mammalian lung and their responses to injury. In the lung, which is constantly exposed to infection and aerosolized toxins, epithelial plasticity might be more of a rule than an exception, and it is likely that different injuries elicit different facultative responses.
The authors declare no competing or financial interests.
J.R. is a Howard Hughes Medical Institute Faculty Scholar, a New York Stem Cell Foundation Robertson Investigator, a Maroni Research Scholar at Massachusetts General Hospital, and a member of the Ludwig Institute for Cancer Research of Harvard Medical School. This research was supported by grants from the National Heart, Lung, and Blood Institute (J.R. and P.R.T.). Deposited in PMC for release after 12 months.