Type 2 alveolar cells are stem cells in adult lung.
Gas exchange in the lung occurs within alveoli, air-filled sacs composed of type 2 and type 1 epithelial cells (AEC2s and AEC1s), capillaries, and various resident mesenchymal cells. Here, we use a combination of in vivo clonal lineage analysis, different injury/repair systems, and in vitro culture of purified cell populations to obtain new information about the contribution of AEC2s to alveolar maintenance and repair. Genetic lineage-tracing experiments showed that surfactant protein C-positive (SFTPC-positive) AEC2s self renew and differentiate over about a year, consistent with the population containing long-term alveolar stem cells. Moreover, if many AEC2s were specifically ablated, high-resolution imaging of intact lungs showed that individual survivors undergo rapid clonal expansion and daughter cell dispersal. Individual lineage-labeled AEC2s placed into 3D culture gave rise to self-renewing "alveolospheres," which contained both AEC2s and cells expressing multiple AEC1 markers, including HOPX, a new marker for AEC1s. Growth and differentiation of the alveolospheres occurred most readily when cocultured with primary PDGFRα⁺ lung stromal cells. This population included lipofibroblasts that normally reside close to AEC2s and may therefore contribute to a stem cell niche in the murine lung. Results suggest that a similar dynamic exists between AEC2s and mesenchymal cells in the human lung.
Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA.
Christina E
CE
Barkauskas
Michael J
MJ
Cronce
Craig R
CR
Rackley
Emily J
EJ
Bowie
Douglas R
DR
Keene
Barry R
BR
Stripp
Scott H
SH
Randell
Paul W
PW
Noble
Brigid L M
BL
Hogan
D053687:Adult Stem Cells / Q000502:physiology*; D056809:Alveolar Epithelial Cells / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation; D019070:Cell Lineage; D049109:Cell Proliferation; D002478:Cells, Cultured; D018920:Coculture Techniques; D008168:Lung / Q000473:pathology*; D055370:Lung Injury / Q000139:chemically induced / Q000473:pathology; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000378:metabolism; D055153:Stem Cell Niche; D017154:Stromal Cells / Q000378:metabolism
D020796:Receptor, Platelet-Derived Growth Factor alpha