title: Lineage-negative progenitors mobilize to regenerate lung epithelium after major injury.
abstract: Broadly, tissue regeneration is achieved in two ways: by proliferation of common differentiated cells and/or by deployment of specialized stem/progenitor cells. Which of these pathways applies is both organ- and injury-specific. Current models in the lung posit that epithelial repair can be attributed to cells expressing mature lineage markers. By contrast, here we define the regenerative role of previously uncharacterized, rare lineage-negative epithelial stem/progenitor (LNEP) cells present within normal distal lung. Quiescent LNEPs activate a ΔNp63 (a p63 splice variant) and cytokeratin 5 remodelling program after influenza or bleomycin injury in mice. Activated cells proliferate and migrate widely to occupy heavily injured areas depleted of mature lineages, at which point they differentiate towards mature epithelium. Lineage tracing revealed scant contribution of pre-existing mature epithelial cells in such repair, whereas orthotopic transplantation of LNEPs, isolated by a definitive surface profile identified through single-cell sequencing, directly demonstrated the proliferative capacity and multipotency of this population. LNEPs require Notch signalling to activate the ΔNp63 and cytokeratin 5 program, and subsequent Notch blockade promotes an alveolar cell fate. Persistent Notch signalling after injury led to parenchymal 'micro-honeycombing' (alveolar cysts), indicative of failed regeneration. Lungs from patients with fibrosis show analogous honeycomb cysts with evidence of hyperactive Notch signalling. Our findings indicate that distinct stem/progenitor cell pools repopulate injured tissue depending on the extent of the injury, and the outcomes of regeneration or fibrosis may depend in part on the dynamics of LNEP Notch signalling.
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Vaughan
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Alexis N
authors.initials: AN
authors.lastname: Brumwell
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xi
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Gotts
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine and Howard Hughes Medical Institute, Stanford, California 94305, USA.
authors.forename: Doug G
authors.initials: DG
authors.lastname: Brownfield
authors.affiliation: Max Planck Institute for Evolutionary Anthropology, Department of Evolutionary Genetics, Deutscher Platz 6, 04103 Leipzig, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Treutlein
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Tan
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Victor
authors.initials: V
authors.lastname: Tan
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Feng Chun
authors.initials: FC
authors.lastname: Liu
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Looney
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Matthay
authors.affiliation: Department of Anatomy, School of Medicine, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Rock
authors.affiliation: Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, California 94143, USA.
authors.forename: Harold A
authors.initials: HA
authors.lastname: Chapman
mesh_terms: D000818:Animals; D001761:Bleomycin; D019070:Cell Lineage; D049109:Cell Proliferation; D002469:Cell Separation; D003560:Cysts / Q000378:metabolism / Q000473:pathology; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D053555:Keratin-5 / Q000378:metabolism; D008168:Lung / Q000166:cytology* / Q000473:pathology* / Q000502:physiology; D055370:Lung Injury / Q000139:chemically induced / Q000473:pathology* / Q000821:virology; D008297:Male; D051379:Mice; D009976:Orthomyxoviridae Infections / Q000473:pathology / Q000821:virology; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D062326:Re-Epithelialization; D051880:Receptors, Notch / Q000378:metabolism; D015398:Signal Transduction; D033581:Stem Cell Transplantation; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
chemical_list: D053555:Keratin-5; D010750:Phosphoproteins; D051880:Receptors, Notch; D015534:Trans-Activators; C486419:Trp63 protein, mouse; D001761:Bleomycin