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Evidence for lung barrier regeneration by differentiation prior to binucleated and stem cell division. J Cell Biol 2023; 222:e202212088. [PMID: 37843535 PMCID: PMC10579698 DOI: 10.1083/jcb.202212088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Revised: 07/17/2023] [Accepted: 10/02/2023] [Indexed: 10/17/2023] Open
Abstract
With each breath, oxygen diffuses across remarkably thin alveolar type I (AT1) cells into underlying capillaries. Interspersed cuboidal AT2 cells produce surfactant and act as stem cells. Even transient disruption of this delicate barrier can promote capillary leak. Here, we selectively ablated AT1 cells, which uncovered rapid AT2 cell flattening with near-continuous barrier preservation, culminating in AT1 differentiation. Proliferation subsequently restored depleted AT2 cells in two phases, mitosis of binucleated AT2 cells followed by replication of mononucleated AT2 cells. M phase entry of binucleated and S phase entry of mononucleated cells were both triggered by AT1-produced hbEGF signaling via EGFR to Wnt-active AT2 cells. Repeated AT1 cell killing elicited exuberant AT2 proliferation, generating aberrant daughter cells that ceased surfactant function yet failed to achieve AT1 differentiation. This hyperplasia eventually resolved, yielding normal-appearing alveoli. Overall, this specialized regenerative program confers a delicate simple epithelium with functional resiliency on par with the physical durability of thicker, pseudostratified, or stratified epithelia.
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A single-cell atlas of in vitro multiculture systems uncovers the in vivo lineage trajectory and cell state in the human lung. Exp Mol Med 2023; 55:1831-1842. [PMID: 37582976 PMCID: PMC10474282 DOI: 10.1038/s12276-023-01076-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 04/14/2023] [Accepted: 04/26/2023] [Indexed: 08/17/2023] Open
Abstract
We present an in-depth single-cell atlas of in vitro multiculture systems on human primary airway epithelium derived from normal and diseased lungs of 27 individual donors. Our large-scale single-cell profiling identified new cell states and differentiation trajectories of rare airway epithelial cell types in human distal lungs. By integrating single-cell datasets of human lung tissues, we discovered immune-primed subsets enriched in lungs and organoids derived from patients with chronic respiratory disease. To demonstrate the full potential of our platform, we further illustrate transcriptomic responses to various respiratory virus infections in vitro airway models. Our work constitutes a single-cell roadmap for the cellular and molecular characteristics of human primary lung cells in vitro and their relevance to human tissues in vivo.
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3
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KRAS(G12D) drives lepidic adenocarcinoma through stem-cell reprogramming. Nature 2023; 619:860-867. [PMID: 37468622 PMCID: PMC10423036 DOI: 10.1038/s41586-023-06324-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 06/14/2023] [Indexed: 07/21/2023]
Abstract
Many cancers originate from stem or progenitor cells hijacked by somatic mutations that drive replication, exemplified by adenomatous transformation of pulmonary alveolar epithelial type II (AT2) cells1. Here we demonstrate a different scenario: expression of KRAS(G12D) in differentiated AT1 cells reprograms them slowly and asynchronously back into AT2 stem cells that go on to generate indolent tumours. Like human lepidic adenocarcinoma, the tumour cells slowly spread along alveolar walls in a non-destructive manner and have low ERK activity. We find that AT1 and AT2 cells act as distinct cells of origin and manifest divergent responses to concomitant WNT activation and KRAS(G12D) induction, which accelerates AT2-derived but inhibits AT1-derived adenoma proliferation. Augmentation of ERK activity in KRAS(G12D)-induced AT1 cells increases transformation efficiency, proliferation and progression from lepidic to mixed tumour histology. Overall, we have identified a new cell of origin for lung adenocarcinoma, the AT1 cell, which recapitulates features of human lepidic cancer. In so doing, we also uncover a capacity for oncogenic KRAS to reprogram a differentiated and quiescent cell back into its parent stem cell en route to adenomatous transformation. Our work further reveals that irrespective of a given cancer's current molecular profile and driver oncogene, the cell of origin exerts a pervasive and perduring influence on its subsequent behaviour.
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Abstract
Single-cell technologies have transformed our understanding of human tissues. Yet, studies typically capture only a limited number of donors and disagree on cell type definitions. Integrating many single-cell datasets can address these limitations of individual studies and capture the variability present in the population. Here we present the integrated Human Lung Cell Atlas (HLCA), combining 49 datasets of the human respiratory system into a single atlas spanning over 2.4 million cells from 486 individuals. The HLCA presents a consensus cell type re-annotation with matching marker genes, including annotations of rare and previously undescribed cell types. Leveraging the number and diversity of individuals in the HLCA, we identify gene modules that are associated with demographic covariates such as age, sex and body mass index, as well as gene modules changing expression along the proximal-to-distal axis of the bronchial tree. Mapping new data to the HLCA enables rapid data annotation and interpretation. Using the HLCA as a reference for the study of disease, we identify shared cell states across multiple lung diseases, including SPP1+ profibrotic monocyte-derived macrophages in COVID-19, pulmonary fibrosis and lung carcinoma. Overall, the HLCA serves as an example for the development and use of large-scale, cross-dataset organ atlases within the Human Cell Atlas.
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Grants
- R01 HL153375 NHLBI NIH HHS
- R01 HL127349 NHLBI NIH HHS
- U54 HL165443 NHLBI NIH HHS
- P01 HL107202 NHLBI NIH HHS
- U01 HL148856 NHLBI NIH HHS
- R21 HL156124 NHLBI NIH HHS
- U54 AG075931 NIA NIH HHS
- Wellcome Trust
- R01 HL146557 NHLBI NIH HHS
- R01 HL123766 NHLBI NIH HHS
- U01 HL148861 NHLBI NIH HHS
- R01 HL141852 NHLBI NIH HHS
- R01 ES034350 NIEHS NIH HHS
- UL1 TR001863 NCATS NIH HHS
- R01 HL126176 NHLBI NIH HHS
- R21 HL161760 NHLBI NIH HHS
- R01 HL145372 NHLBI NIH HHS
- P01 AG049665 NIA NIH HHS
- K12 HD105271 NICHD NIH HHS
- U19 AI135964 NIAID NIH HHS
- P30 CA008748 NCI NIH HHS
- R01 HL142568 NHLBI NIH HHS
- R01 HL153312 NHLBI NIH HHS
- U54 AG079754 NIA NIH HHS
- R56 HL157632 NHLBI NIH HHS
- R01 HL158139 NHLBI NIH HHS
- R01 HL135156 NHLBI NIH HHS
- R01 HL153045 NHLBI NIH HHS
- U54 HL145608 NHLBI NIH HHS
- P50 AR060780 NIAMS NIH HHS
- R01 HL128439 NHLBI NIH HHS
- R01 HL146519 NHLBI NIH HHS
- R01 HL117004 NHLBI NIH HHS
- R01 HL068702 NHLBI NIH HHS
- U01 HL145567 NHLBI NIH HHS
- P01 HL132821 NHLBI NIH HHS
- MR/R015635/1 Medical Research Council
- R01 MD010443 NIMHD NIH HHS
- Chan Zuckerberg Initiative, LLC Seed Network grant (CZF2019-002438) “Lung Cell Atlas 1.0” NIH 1U54HL145608-01 CZIF2022-007488 from the Chan Zuckerberg Initiative Foundation CZIF2022-007488 from the Chan Zuckerberg Initiative Foundation
- ESPOD fellowship of EMBL-EBI and Sanger Institute
- 3IA Cote d’Azur PhD program
- The Ministry of Economic Affairs and Climate Policy by means of the PPP
- EC | Horizon 2020 Framework Programme (EU Framework Programme for Research and Innovation H2020)
- Joachim Herz Stiftung (Joachim Herz Foundation)
- P50 AR060780-06A1
- University College London, Birkbeck MRC Doctoral Training Programme
- Jikei University School of Medicine (Jikei University)
- 5R01HL14254903, 4UH3CA25513503
- R01HL127349, R01HL141852, U01HL145567 and CZI
- MRC Clinician Scientist Fellowship (MR/W00111X/1)
- Chan Zuckerberg Initiative, LLC Seed Network grant (CZF2019-002438) “Lung Cell Atlas 1.0” 2R01HL068702
- R01 HL135156, R01 MD010443, R01 HL128439, P01 HL132821, P01 HL107202, R01 HL117004, and DOD Grant W81WH-16-2-0018
- HL142568 and HL14507 from the NHLBI
- Chan Zuckerberg Initiative, LLC Seed Network grant (CZF2019-002438) “Lung Cell Atlas 1.0”, 2R01HL068702
- Wellcome (WT211276/Z/18/Z) Sanger core grant WT206194 CZIF2022-007488 from the Chan Zuckerberg Initiative Foundation
- R21HL156124, R56HL157632, and R21HL161760
- CZI, 5U01HL148856
- CZI, 5U01HL148856, R01 HL153045
- U.S. Department of Defense (United States Department of Defense)
- The National Institute of Health R01HL145372
- Fondation pour la Recherche Médicale (Foundation for Medical Research in France)
- Conseil Départemental des Alpes Maritimes
- Inserm Cross-cutting Scientific Program HuDeCA 2018, ANR SAHARRA (ANR-19-CE14–0027), ANR-19-P3IA-0002–3IA, the National Infrastructure France Génomique (ANR-10-INBS-09-03), PPIA 4D-OMICS (21-ESRE-0052), and the Chan Zuckerberg Initiative, LLC Seed Network grant (CZF2019-002438) “Lung Cell Atlas 1.0”.
- Wellcome Trust (Wellcome)
- Sanger core grant WT206194 Chan Zuckerberg Initiative, LLC Seed Network grant (CZF2019-002438) “Lung Cell Atlas 1.0” CZIF2022-007488 from the Chan Zuckerberg Initiative Foundation
- Doris Duke Charitable Foundation (DDCF)
- The National Institute of Health R01HL145372 Department of Defense W81XWH-19-1-0416
- The National Institute of Health R01HL146557 and R01HL153375 and funds from Chan Zuckerberg Initiative - Human Lung Cell Atlas-pilot award
- 1U54HL145608-01
- CZI Deep Visual Proteomics
- 1U54HL145608-01, U01HL148861-03
- 1) the Chan Zuckerberg Initiative, LLC Seed Network grant CZF2019-002438 “Lung Cell Atlas 1.0”; 2) R01 HL153312; 3) U19 AI135964; 4) P01 AG049665
- Netherlands Lung Foundation project nos. 5.1.14.020 and 4.1.18.226, LLC Seed Network grant CZF2019-002438 “Lung Cell Atlas 1.0”
- grant number 2019-002438 from the Chan Zuckerberg Foundation, by the Helmholtz Association’s Initiative and Networking Fund through Helmholtz AI [ZT-I-PF-5-01] and by the Bavarian Ministry of Science and the Arts in the framework of the Bavarian Research Association “ForInter” (Interaction of human brain cells)
- 1 U01 HL14555-01, R01 HL123766-04
- NIH U54 AG075931, 5R01 HL146519
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Relationship between impaired BMP signalling and clinical risk factors at early-stage vascular injury in the preterm infant. Thorax 2022; 77:1176-1186. [PMID: 35580897 PMCID: PMC9685723 DOI: 10.1136/thoraxjnl-2021-218083] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 04/11/2022] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Chronic lung disease, that is, bronchopulmonary dysplasia (BPD) is the most common complication in preterm infants and develops as a consequence of the misguided formation of the gas-exchange area undergoing prenatal and postnatal injury. Subsequent vascular disease and its progression into pulmonary arterial hypertension critically determines long-term outcome in the BPD infant but lacks identification of early, disease-defining changes. METHODS We link impaired bone morphogenetic protein (BMP) signalling to the earliest onset of vascular pathology in the human preterm lung and delineate the specific effects of the most prevalent prenatal and postnatal clinical risk factors for lung injury mimicking clinically relevant conditions in a multilayered animal model using wild-type and transgenic neonatal mice. RESULTS We demonstrate (1) the significant reduction in BMP receptor 2 (BMPR2) expression at the onset of vascular pathology in the lung of preterm infants, later mirrored by reduced plasma BMP protein levels in infants with developing BPD, (2) the rapid impairment (and persistent change) of BMPR2 signalling on postnatal exposure to hyperoxia and mechanical ventilation, aggravated by prenatal cigarette smoke in a preclinical mouse model and (3) a link to defective alveolar septation and matrix remodelling through platelet derived growth factor-receptor alpha deficiency. In a treatment approach, we partially reversed vascular pathology by BMPR2-targeted treatment with FK506 in vitro and in vivo. CONCLUSION We identified impaired BMP signalling as a hallmark of early vascular disease in the injured neonatal lung while outlining its promising potential as a future biomarker or therapeutic target in this growing, high-risk patient population.
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Alveolar cell fate selection and lifelong maintenance of AT2 cells by FGF signaling. Nat Commun 2022; 13:7137. [PMID: 36414616 PMCID: PMC9681748 DOI: 10.1038/s41467-022-34059-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 10/12/2022] [Indexed: 11/24/2022] Open
Abstract
The lung's gas exchange surface is comprised of alveolar AT1 and AT2 cells that are corrupted in several common and deadly diseases. They arise from a bipotent progenitor whose differentiation is thought to be dictated by differential mechanical forces. Here we show the critical determinant is FGF signaling. Fgfr2 is expressed in the developing progenitors in mouse then restricts to nascent AT2 cells and remains on throughout life. Its ligands are expressed in surrounding mesenchyme and can, in the absence of exogenous mechanical cues, induce progenitors to form alveolospheres with intermingled AT2 and AT1 cells. FGF signaling directly and cell autonomously specifies AT2 fate; progenitors lacking Fgfr2 in vitro and in vivo exclusively acquire AT1 fate. Fgfr2 loss in AT2 cells perinatally results in reprogramming to AT1 identity, whereas loss or inhibition later in life triggers AT2 apoptosis and compensatory regeneration. We propose that Fgfr2 signaling selects AT2 fate during development, induces a cell non-autonomous AT1 differentiation signal, then continuously maintains AT2 identity and survival throughout life.
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New Insights into Clinical and Mechanistic Heterogeneity of the Acute Respiratory Distress Syndrome: Summary of the Aspen Lung Conference 2021. Am J Respir Cell Mol Biol 2022; 67:284-308. [PMID: 35679511 PMCID: PMC9447141 DOI: 10.1165/rcmb.2022-0089ws] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 06/09/2022] [Indexed: 12/15/2022] Open
Abstract
Clinical and molecular heterogeneity are common features of human disease. Understanding the basis for heterogeneity has led to major advances in therapy for many cancers and pulmonary diseases such as cystic fibrosis and asthma. Although heterogeneity of risk factors, disease severity, and outcomes in survivors are common features of the acute respiratory distress syndrome (ARDS), many challenges exist in understanding the clinical and molecular basis for disease heterogeneity and using heterogeneity to tailor therapy for individual patients. This report summarizes the proceedings of the 2021 Aspen Lung Conference, which was organized to review key issues related to understanding clinical and molecular heterogeneity in ARDS. The goals were to review new information about ARDS phenotypes, to explore multicellular and multisystem mechanisms responsible for heterogeneity, and to review how best to account for clinical and molecular heterogeneity in clinical trial design and assessment of outcomes. The report concludes with recommendations for future research to understand the clinical and basic mechanisms underlying heterogeneity in ARDS to advance the development of new treatments for this life-threatening critical illness.
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8
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Proceedings of the ISCT scientific signature series symposium, "Advances in cell and gene therapies for lung diseases and critical illnesses": International Society for Cell & Gene Therapy, Burlington VT, US, July 16, 2021. Cytotherapy 2022; 24:774-788. [PMID: 35613962 DOI: 10.1016/j.jcyt.2021.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 11/05/2021] [Indexed: 11/20/2022]
Abstract
The ISCT Scientific Signature Series Symposium "Advances in Cell and Gene Therapies for Lung Diseases and Critical Illnesses" was held as an independent symposium in conjunction with the biennial meeting, "Stem Cells, Cell Therapies, and Bioengineering in Lung Biology and Diseases," which took place July 12-15, 2021, at the University of Vermont. This is the third Respiratory System-based Signature Series event; the first 2, "Tracheal Bioengineering, the Next Steps" and "Cellular Therapies for Pulmonary Diseases and Critical Illnesses: State of the Art of European Science," took place in 2014 and 2015, respectively. Cell- and gene-based therapies for respiratory diseases and critical illnesses continue to be a source of great promise and opportunity. This reflects ongoing advancements in understanding of the mechanisms by which cell-based therapies, particularly those using mesenchymal stromal cells (MSCs), can mitigate different lung injuries and the increasing sophistication with which preclinical data is translated into clinical investigations. This also reflects continuing evolution in gene transfer vectors, including those designed for in situ gene editing in parallel with those targeting gene or cell replacement. Therefore, this symposium convened global thought leaders in a forum designed to catalyze communication and collaboration to bring the greatest possible innovation and value of cell- and gene-based therapies for patients with respiratory diseases and critical illnesses.
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9
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Targeted replacement of full-length CFTR in human airway stem cells by CRISPR-Cas9 for pan-mutation correction in the endogenous locus. Mol Ther 2022; 30:223-237. [PMID: 33794364 PMCID: PMC8753290 DOI: 10.1016/j.ymthe.2021.03.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 02/23/2021] [Accepted: 03/25/2021] [Indexed: 01/07/2023] Open
Abstract
Cystic fibrosis (CF) is a monogenic disease caused by impaired production and/or function of the CF transmembrane conductance regulator (CFTR) protein. Although we have previously shown correction of the most common pathogenic mutation, there are many other pathogenic mutations throughout the CF gene. An autologous airway stem cell therapy in which the CFTR cDNA is precisely inserted into the CFTR locus may enable the development of a durable cure for almost all CF patients, irrespective of the causal mutation. Here, we use CRISPR-Cas9 and two adeno-associated viruses (AAVs) carrying the two halves of the CFTR cDNA to sequentially insert the full CFTR cDNA along with a truncated CD19 (tCD19) enrichment tag in upper airway basal stem cells (UABCs) and human bronchial epithelial cells (HBECs). The modified cells were enriched to obtain 60%-80% tCD19+ UABCs and HBECs from 11 different CF donors with a variety of mutations. Differentiated epithelial monolayers cultured at air-liquid interface showed restored CFTR function that was >70% of the CFTR function in non-CF controls. Thus, our study enables the development of a therapy for almost all CF patients, including patients who cannot be treated using recently approved modulator therapies.
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Dual inhibition of α vβ 6 and α vβ 1 reduces fibrogenesis in lung tissue explants from patients with IPF. Respir Res 2021; 22:265. [PMID: 34666752 PMCID: PMC8524858 DOI: 10.1186/s12931-021-01863-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 10/10/2021] [Indexed: 12/11/2022] Open
Abstract
RATIONALE αv integrins, key regulators of transforming growth factor-β activation and fibrogenesis in in vivo models of pulmonary fibrosis, are expressed on abnormal epithelial cells (αvβ6) and fibroblasts (αvβ1) in fibrotic lungs. OBJECTIVES We evaluated multiple αv integrin inhibition strategies to assess which most effectively reduced fibrogenesis in explanted lung tissue from patients with idiopathic pulmonary fibrosis. METHODS Selective αvβ6 and αvβ1, dual αvβ6/αvβ1, and multi-αv integrin inhibitors were characterized for potency, selectivity, and functional activity by ligand binding, cell adhesion, and transforming growth factor-β cell activation assays. Precision-cut lung slices generated from lung explants from patients with idiopathic pulmonary fibrosis or bleomycin-challenged mouse lungs were treated with integrin inhibitors or standard-of-care drugs (nintedanib or pirfenidone) and analyzed for changes in fibrotic gene expression or TGF-β signaling. Bleomycin-challenged mice treated with dual αvβ6/αvβ1 integrin inhibitor, PLN-74809, were assessed for changes in pulmonary collagen deposition and Smad3 phosphorylation. MEASUREMENTS AND MAIN RESULTS Inhibition of integrins αvβ6 and αvβ1 was additive in reducing type I collagen gene expression in explanted lung tissue slices from patients with idiopathic pulmonary fibrosis. These data were replicated in fibrotic mouse lung tissue, with no added benefit observed from inhibition of additional αv integrins. Antifibrotic efficacy of dual αvβ6/αvβ1 integrin inhibitor PLN-74809 was confirmed in vivo, where dose-dependent inhibition of pulmonary Smad3 phosphorylation and collagen deposition was observed. PLN-74809 also, more potently, reduced collagen gene expression in fibrotic human and mouse lung slices than clinically relevant concentrations of nintedanib or pirfenidone. CONCLUSIONS In the fibrotic lung, dual inhibition of integrins αvβ6 and αvβ1 offers the optimal approach for blocking fibrogenesis resulting from integrin-mediated activation of transforming growth factor-β.
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11
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First lung and kidney multi-organ transplant following COVID-19 Infection. J Heart Lung Transplant 2021; 40:856-859. [PMID: 34059432 PMCID: PMC8088330 DOI: 10.1016/j.healun.2021.02.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 02/10/2021] [Accepted: 02/15/2021] [Indexed: 12/12/2022] Open
Abstract
As the world responds to the global crisis of the COVID-19 pandemic an increasing number of patients are experiencing increased morbidity as a result of multi-organ involvement. Of these, a small proportion will progress to end-stage lung disease, become dialysis dependent, or both. Herein, we describe the first reported case of a successful combined lung and kidney transplantation in a patient with COVID-19. Lung transplantation, isolated or combined with other organs, is feasible and should be considered for select patients impacted by this deadly disease.
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Abstract
The distal lung is a honeycomb-like collection of delicate gas exchange sacs called alveoli lined by two interspersed epithelial cell types: the cuboidal, surfactant-producing alveolar type II (AT2) and the flat, gas-exchanging alveolar type I (AT1) cell. During aging, a subset of AT2 cells expressing the canonical Wnt target gene, Axin2, function as stem cells, renewing themselves while generating new AT1 and AT2 cells. Wnt activity endows AT2 cells with proliferative competency, enabling them to respond to activating cues, and simultaneously blocks AT2 to AT1 cell transdifferentiation. Acute alveolar injury rapidly expands the AT2 stem cell pool by transiently inducing Wnt signaling activity in "bulk" AT2 cells, facilitating rapid epithelial repair. AT2 cell "stemness" is thus tightly regulated by access to Wnts, supplied by a specialized single-cell fibroblast niche during maintenance and by AT2 cells themselves during injury repair. Two non-AT2 "reserve" cell populations residing in the distal airways also contribute to alveolar repair, but only after widespread epithelial injury, when they rapidly proliferate, migrate, and differentiate into airway and alveolar lineages. Here, we review alveolar renewal and repair with a focus on the niches, rather than the stem cells, highlighting what is known about the cellular and molecular mechanisms by which they control stem cell activity in vivo.
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Progenitor identification and SARS-CoV-2 infection in human distal lung organoids. Nature 2020; 588:670-675. [PMID: 33238290 PMCID: PMC8003326 DOI: 10.1038/s41586-020-3014-1] [Citation(s) in RCA: 209] [Impact Index Per Article: 52.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 11/18/2020] [Indexed: 12/17/2022]
Abstract
The distal lung contains terminal bronchioles and alveoli that facilitate gas exchange. Three-dimensional in vitro human distal lung culture systems would strongly facilitate the investigation of pathologies such as interstitial lung disease, cancer and coronavirus disease 2019 (COVID-19) pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here we describe the development of a long-term feeder-free, chemically defined culture system for distal lung progenitors as organoids derived from single adult human alveolar epithelial type II (AT2) or KRT5+ basal cells. AT2 organoids were able to differentiate into AT1 cells, and basal cell organoids developed lumens lined with differentiated club and ciliated cells. Single-cell analysis of KRT5+ cells in basal organoids revealed a distinct population of ITGA6+ITGB4+ mitotic cells, whose offspring further segregated into a TNFRSF12Ahi subfraction that comprised about ten per cent of KRT5+ basal cells. This subpopulation formed clusters within terminal bronchioles and exhibited enriched clonogenic organoid growth activity. We created distal lung organoids with apical-out polarity to present ACE2 on the exposed external surface, facilitating infection of AT2 and basal cultures with SARS-CoV-2 and identifying club cells as a target population. This long-term, feeder-free culture of human distal lung organoids, coupled with single-cell analysis, identifies functional heterogeneity among basal cells and establishes a facile in vitro organoid model of human distal lung infections, including COVID-19-associated pneumonia.
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Advances in Proximity Ligation in situ Hybridization (PLISH). Bio Protoc 2020; 10:e3808. [PMID: 33659462 PMCID: PMC7842654 DOI: 10.21769/bioprotoc.3808] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 08/25/2020] [Accepted: 09/22/2020] [Indexed: 11/02/2022] Open
Abstract
Understanding tissues in the context of development, maintenance and disease requires determining the molecular profiles of individual cells within their native in vivo spatial context. We developed a Proximity Ligation in situ Hybridization technology (PLISH) that enables quantitative measurement of single cell gene expression in intact tissues, which we have now updated. By recording spatial information for every profiled cell, PLISH enables retrospective mapping of distinct cell classes and inference of their in vivo interactions. PLISH has high sensitivity, specificity and signal to noise ratio. It is also rapid, scalable, and does not require expertise in molecular biology so it can be easily adopted by basic and clinical researchers.
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Progenitor identification and SARS-CoV-2 infection in long-term human distal lung organoid cultures. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2020:2020.07.27.212076. [PMID: 32743583 PMCID: PMC7386503 DOI: 10.1101/2020.07.27.212076] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The distal lung contains terminal bronchioles and alveoli that facilitate gas exchange and is affected by disorders including interstitial lung disease, cancer, and SARS-CoV-2-associated COVID-19 pneumonia. Investigations of these localized pathologies have been hindered by a lack of 3D in vitro human distal lung culture systems. Further, human distal lung stem cell identification has been impaired by quiescence, anatomic divergence from mouse and lack of lineage tracing and clonogenic culture. Here, we developed robust feeder-free, chemically-defined culture of distal human lung progenitors as organoids derived clonally from single adult human alveolar epithelial type II (AT2) or KRT5 + basal cells. AT2 organoids exhibited AT1 transdifferentiation potential, while basal cell organoids progressively developed lumens lined by differentiated club and ciliated cells. Organoids consisting solely of club cells were not observed. Upon single cell RNA-sequencing (scRNA-seq), alveolar organoids were composed of proliferative AT2 cells; however, basal organoid KRT5 + cells contained a distinct ITGA6 + ITGB4 + mitotic population whose proliferation segregated to a TNFRSF12A hi subfraction. Clonogenic organoid growth was markedly enriched within the TNFRSF12A hi subset of FACS-purified ITGA6 + ITGB4 + basal cells from human lung or derivative organoids. In vivo, TNFRSF12A + cells comprised ~10% of KRT5 + basal cells and resided in clusters within terminal bronchioles. To model COVID-19 distal lung disease, we everted the polarity of basal and alveolar organoids to rapidly relocate differentiated club and ciliated cells from the organoid lumen to the exterior surface, thus displaying the SARS-CoV-2 receptor ACE2 on the outwardly-facing apical aspect. Accordingly, basal and AT2 apical-out organoids were infected by SARS-CoV-2, identifying club cells as a novel target population. This long-term, feeder-free organoid culture of human distal lung alveolar and basal stem cells, coupled with single cell analysis, identifies unsuspected basal cell functional heterogeneity and exemplifies progenitor identification within a slowly proliferating human tissue. Further, our studies establish a facile in vitro organoid model for human distal lung infectious diseases including COVID-19-associated pneumonia.
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Corrigendum: Niche Cells and Signals that Regulate Lung Alveolar Stem Cells In Vivo. Cold Spring Harb Perspect Biol 2020; 12:a040303. [PMID: 32358163 PMCID: PMC7197427 DOI: 10.1101/cshperspect.a040303] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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High-Efficiency, Selection-free Gene Repair in Airway Stem Cells from Cystic Fibrosis Patients Rescues CFTR Function in Differentiated Epithelia. Cell Stem Cell 2020; 26:161-171.e4. [PMID: 31839569 PMCID: PMC10908575 DOI: 10.1016/j.stem.2019.11.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 07/29/2019] [Accepted: 11/11/2019] [Indexed: 12/19/2022]
Abstract
Cystic fibrosis (CF) is a monogenic disorder caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. Mortality in CF patients is mostly due to respiratory sequelae. Challenges with gene delivery have limited attempts to treat CF using in vivo gene therapy, and low correction levels have hindered ex vivo gene therapy efforts. We have used Cas9 and adeno-associated virus 6 to correct the ΔF508 mutation in readily accessible upper-airway basal stem cells (UABCs) obtained from CF patients. On average, we achieved 30%-50% allelic correction in UABCs and bronchial epithelial cells (HBECs) from 10 CF patients and observed 20%-50% CFTR function relative to non-CF controls in differentiated epithelia. Furthermore, we successfully embedded the corrected UABCs on an FDA-approved porcine small intestinal submucosal membrane (pSIS), and they retained differentiation capacity. This study supports further development of genetically corrected autologous airway stem cell transplant as a treatment for CF.
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Attenuated PDGF signaling drives alveolar and microvascular defects in neonatal chronic lung disease. EMBO Mol Med 2018; 9:1504-1520. [PMID: 28923828 PMCID: PMC5666314 DOI: 10.15252/emmm.201607308] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Neonatal chronic lung disease (nCLD) affects a significant number of neonates receiving mechanical ventilation with oxygen-rich gas (MV-O2). Regardless, the primary molecular driver of the disease remains elusive. We discover significant enrichment for SNPs in the PDGF-Rα gene in preterms with nCLD and directly test the effect of PDGF-Rα haploinsufficiency on the development of nCLD using a preclinical mouse model of MV-O2 In the context of MV-O2, attenuated PDGF signaling independently contributes to defective septation and endothelial cell apoptosis stemming from a PDGF-Rα-dependent reduction in lung VEGF-A. TGF-β contributes to the PDGF-Rα-dependent decrease in myofibroblast function. Remarkably, endotracheal treatment with exogenous PDGF-A rescues both the lung defects in haploinsufficient mice undergoing MV-O2 Overall, our results establish attenuated PDGF signaling as an important driver of nCLD pathology with provision of PDGF-A as a protective strategy for newborns undergoing MV-O2.
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Single-cell Wnt signaling niches maintain stemness of alveolar type 2 cells. Science 2018; 359:1118-1123. [PMID: 29420258 DOI: 10.1126/science.aam6603] [Citation(s) in RCA: 454] [Impact Index Per Article: 75.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 01/20/2017] [Accepted: 01/23/2018] [Indexed: 01/03/2023]
Abstract
Alveoli, the lung's respiratory units, are tiny sacs where oxygen enters the bloodstream. They are lined by flat alveolar type 1 (AT1) cells, which mediate gas exchange, and AT2 cells, which secrete surfactant. Rare AT2s also function as alveolar stem cells. We show that AT2 lung stem cells display active Wnt signaling, and many of them are near single, Wnt-expressing fibroblasts. Blocking Wnt secretion depletes these stem cells. Daughter cells leaving the Wnt niche transdifferentiate into AT1s: Maintaining Wnt signaling prevents transdifferentiation, whereas abrogating Wnt signaling promotes it. Injury induces AT2 autocrine Wnts, recruiting "bulk" AT2s as progenitors. Thus, individual AT2 stem cells reside in single-cell fibroblast niches providing juxtacrine Wnts that maintain them, whereas injury induces autocrine Wnts that transiently expand the progenitor pool. This simple niche maintains the gas exchange surface and is coopted in cancer.
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Automated cell-type classification in intact tissues by single-cell molecular profiling. eLife 2018; 7:30510. [PMID: 29319504 PMCID: PMC5802843 DOI: 10.7554/elife.30510] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 01/09/2018] [Indexed: 12/20/2022] Open
Abstract
A major challenge in biology is identifying distinct cell classes and mapping their interactions in vivo. Tissue-dissociative technologies enable deep single cell molecular profiling but do not provide spatial information. We developed a proximity ligation in situ hybridization technology (PLISH) with exceptional signal strength, specificity, and sensitivity in tissue. Multiplexed data sets can be acquired using barcoded probes and rapid label-image-erase cycles, with automated calculation of single cell profiles, enabling clustering and anatomical re-mapping of cells. We apply PLISH to expression profile ~2900 cells in intact mouse lung, which identifies and localizes known cell types, including rare ones. Unsupervised classification of the cells indicates differential expression of ‘housekeeping’ genes between cell types, and re-mapping of two sub-classes of Club cells highlights their segregated spatial domains in terminal airways. By enabling single cell profiling of various RNA species in situ, PLISH can impact many areas of basic and medical research. The human body contains several hundred types of specialized cells that have different roles. The cells form tissues, and each tissue can only work if it has the right cells and if they are correctly organized and distributed to build working structures. This is how the same body parts, e.g. lungs, brains, hearts, end up looking and working the same way in almost everyone. Cells organize themselves into tissues by exchanging short-range messages between nearby cells. Understanding how cells communicate to form, maintain and repair tissues is a challenge for biologists. Finding ways to examine different signals at the same time would improve our understanding of these important processes. Now, Nagendran, Riordan et al. developed a microscopy technique that can tackle this issue. The cells can be stained and tagged with already established dyes and markers to measure the location and signals of all cell groups at the same time. By calculating how these cells are distributed in space it is then possible to estimate how they interact with each other. Based on this, Nagendran, Riordan et al. then successfully tested their tool in lung tissues from mice and humans. This cheap, high-speed technology works on tissue samples from any animal, including humans, and can be easily combined with existing technologies and so be adapted for a wide range of uses. A deeper knowledge of how combinations of signals guide tissue formation and maintenance could help us to better understand what causes developmental diseases, organ failures and cancer. Tools like this could even help to identify key targets for new treatments.
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Trinucleotide repeat containing 6c (TNRC6c) is essential for microvascular maturation during distal airspace sacculation in the developing lung. Dev Biol 2017; 430:214-223. [PMID: 28811219 PMCID: PMC5634525 DOI: 10.1016/j.ydbio.2017.07.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 07/25/2017] [Accepted: 07/25/2017] [Indexed: 01/09/2023]
Abstract
GW182 (also known asTNRC6) family members are critically involved in the final effector phase of miRNA-mediated mRNA repression. The three mammalian paralogs, TNRC6a, b and c, are thought to be redundant based on Argonaute (Ago) binding, tethering assays, and RNAi silencing of individual members in cell lines. To test this idea, we generated TNRC6a, b and c knockout mice. TNRC6a mutants die at mid-gestation, while b- and c- deleted mice are born at a Mendelian ratio. However, the majority of TNRC6b and all TNRC6c mutants die within 24h after birth, the latter with respiratory failure. Necropsy of TNRC6c mutants revealed normal-appearing airways that give rise to abnormally thick-walled distal gas exchange sacs. Immunohistological analysis of mutant lungs demonstrated a normal distribution of bronchiolar and alveolar cells, indicating that loss of TNRC6c did not abrogate epithelial cell differentiation. The cellular kinetics and relative proportions of endothelial, epithelial, and mesenchymal cells were also not altered. However, the underlying capillary network was simplified and endothelial cells had failed to become tightly apposed to the surface epithelium in TNRC6c mutants, presumably causing the observed respiratory failure. TGFβ family mutant mice exhibit a similar lung phenotype of thick-walled air sacs and neonatal lethality, and qRT-PCR confirmed dynamic downregulation of TGFβ1 and TGFβR2 in TNRC6c mutant lungs during sacculation. VEGFR, but not VEGF-A ligand, was also lower, likely reflecting the overall reduced capillary density in TNRC6c mutants. Together, these results demonstrate that GW182 paralogs are not functionally redundant in vivo. Surprisingly, despite regulating a general cellular process, TNRC6c is selectively required only in the distal lung and not until late in gestation for proper expression of the TGFβ family genes that drive sacculation. These results imply a complex and indirect mode of regulation of sacculation by TNRC6c, mediated in part by dynamic transcriptional repression of an inhibitor of TGFβ family gene expression.
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Abstract
The application of in vivo genetic lineage tracing has advanced our understanding of cellular mechanisms for tissue renewal in organs with slow turnover, like the lung. These studies have identified an adult stem cell with very different properties than classically understood ones that maintain continuously cycling tissues such as the intestine. A portrait has emerged of an ensemble of cellular programs that replenish the cells that line the gas exchange (alveolar) surface, enabling a response tailored to the extent of cell loss. A capacity for differentiated cells to undergo direct lineage transitions allows for local restoration of proper cell balance at sites of injury. We present these recent findings as a paradigm for how a relatively quiescent tissue compartment can maintain homeostasis throughout a lifetime punctuated by injuries ranging from mild to life-threatening, and discuss how dysfunction or insufficiency of alveolar repair programs produce serious health consequences like cancer and fibrosis.
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Alveolar progenitor and stem cells in lung development, renewal and cancer. Nature 2014; 507:190-4. [PMID: 24499815 DOI: 10.1038/nature12930] [Citation(s) in RCA: 671] [Impact Index Per Article: 67.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 12/03/2013] [Indexed: 12/28/2022]
Abstract
Alveoli are gas-exchange sacs lined by squamous alveolar type (AT) 1 cells and cuboidal, surfactant-secreting AT2 cells. Classical studies suggested that AT1 arise from AT2 cells, but recent studies propose other sources. Here we use molecular markers, lineage tracing and clonal analysis to map alveolar progenitors throughout the mouse lifespan. We show that, during development, AT1 and AT2 cells arise directly from a bipotent progenitor, whereas after birth new AT1 cells derive from rare, self-renewing, long-lived, mature AT2 cells that produce slowly expanding clonal foci of alveolar renewal. This stem-cell function is broadly activated by AT1 injury, and AT2 self-renewal is selectively induced by EGFR (epidermal growth factor receptor) ligands in vitro and oncogenic Kras(G12D) in vivo, efficiently generating multifocal, clonal adenomas. Thus, there is a switch after birth, when AT2 cells function as stem cells that contribute to alveolar renewal, repair and cancer. We propose that local signals regulate AT2 stem-cell activity: a signal transduced by EGFR-KRAS controls self-renewal and is hijacked during oncogenesis, whereas another signal controls reprogramming to AT1 fate.
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Inhibition of Tgf beta signaling by endogenous retinoic acid is essential for primary lung bud induction. Development 2007; 134:2969-79. [PMID: 17634193 DOI: 10.1242/dev.006221] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Disruption of retinoic acid (RA) signaling during early development results in severe respiratory tract abnormalities, including lung agenesis. Previous studies suggest that this might result from failure to selectively induce fibroblast growth factor 10 (Fgf10) in the prospective lung region of the foregut. Little is known about the RA-dependent pathways present in the foregut that may be crucial for lung formation. By performing global gene expression analysis of RA-deficient foreguts from a genetic [retinaldehyde dehydrogenase 2 (Raldh2)-null] and a pharmacological (BMS493-treated) mouse model, we found upregulation of a large number of Tgfbeta targets. Increased Smad2 phosphorylation further suggested that Tgfbeta signaling was hyperactive in these foreguts when lung agenesis was observed. RA rescue of the lung phenotype was associated with low levels of Smad2 phosphorylation and downregulation of Tgfbeta targets in Raldh2-null foreguts. Interestingly, the lung defect that resulted from RA-deficiency could be reproduced in RA-sufficient foreguts by hyperactivating Tgfbeta signaling with exogenous TGF beta 1. Preventing activation of endogenous Tgfbeta signaling with a pan-specific TGFbeta-blocking antibody allowed bud formation and gene expression in the lung field of both Raldh2-null and BMS493-treated foreguts. Our data support a novel mechanism of RA-Tgfbeta-Fgf10 interactions in the developing foregut, in which endogenous RA controls Tgfbeta activity in the prospective lung field to allow local expression of Fgf10 and induction of lung buds.
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Distinct roles for retinoic acid receptors alpha and beta in early lung morphogenesis. Dev Biol 2006; 291:12-24. [PMID: 16427040 DOI: 10.1016/j.ydbio.2005.10.045] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Revised: 09/05/2005] [Accepted: 10/03/2005] [Indexed: 12/01/2022]
Abstract
Retinoic acid (RA) signaling is required for normal development of multiple organs. However, little is known about how RA influences the initial stages of lung development. Here, we used a combination of genetic, pharmacological and explant culture approaches to address this issue, and to investigate how signaling by different RA receptors (RAR) mediates the RA effects. We analyzed initiation of lung development in retinaldehyde dehydrogenase-2 (Raldh2) null mice, a model in which RA signaling is absent from the foregut from its earliest developmental stages. We provide evidence that RA is dispensable for specification of lung cell fate in the endoderm. By using synthetic retinoids to selectively activate RAR alpha or beta signaling in this model, we demonstrate novel and unique functions of these receptors in the early lung. We show that activation of RAR beta, but not alpha, induces expression of the fibroblast growth factor Fgf10 and bud morphogenesis in the lung field. Similar analysis of wild type foregut shows that endogenous RAR alpha activity is required to maintain overall RA signaling, and to refine the RAR beta effects in the lung field. Our data support the idea that balanced activation of RAR alpha and beta is critical for proper lung bud initiation and endodermal differentiation.
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Retinoic acid selectively regulates Fgf10 expression and maintains cell identity in the prospective lung field of the developing foregut. Dev Biol 2004; 273:402-15. [PMID: 15328022 DOI: 10.1016/j.ydbio.2004.04.039] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2004] [Revised: 04/21/2004] [Accepted: 04/21/2004] [Indexed: 01/26/2023]
Abstract
Although respiratory tract defects that result from disruption of retinoic acid (RA) signaling have been widely reported, the mechanism by which endogenous RA regulates early lung morphogenesis is unknown. Here, we provide novel evidence that a major role for RA is to selectively maintain mesodermal proliferation and induce fibroblast growth factor 10 (Fgf10) expression in the foregut region where the lung forms. By using a pan-RAR antagonist (BMS493) in foregut explant cultures, we show that bud initiation is selectively blocked in the prospective respiratory region by failure to induce Fgf10 in the corresponding mesoderm. The RA regulation of Fgf10 expression occurs only in this region, within a defined developmental window, and is not seen in other foregut derivatives such as thyroid and pancreas where Fgf10 is also required for normal development. Furthermore, we show that RA activity is essential in the lung field to maintain lung cell identity in the endoderm; RAR antagonism disrupts expression of thyroid transcription factor 1 (Ttf1), an early marker of the respiratory region in the endoderm, and surfactant protein C (Sp-C) mRNAs. Our observations in mouse foregut cultures are corroborated by data from an in vivo model of vitamin A deficiency in rats. Our study supports RA as an essential regulator of gene expression and cellular activities during primary bud formation.
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Growth factors in lung development and disease: friends or foe? Respir Res 2002; 3:2. [PMID: 11806837 PMCID: PMC64813 DOI: 10.1186/rr169] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2001] [Revised: 08/07/2001] [Accepted: 08/09/2001] [Indexed: 11/18/2022] Open
Abstract
Growth factors mediate tissue interactions and regulate a variety of cellular functions that are critical for normal lung development and homeostasis. Besides their involvement in lung pattern formation, growth and cell differentiation during organogenesis, these factors have been also implicated in modulating injury-repair responses of the adult lung. Altered expression of growth factors, such as transforming growth factor beta1, vascular endothelial growth factor and epidermal growth factor, and/or their receptors, has been found in a number of pathological lung conditions. In this paper, we discuss the dual role of these molecules in mediating beneficial feedback responses or responses that can further damage lung integrity; we shall also discuss the basis for their prospective use as therapeutic agents.
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Participation of urokinase-type plasminogen activator receptor in the clearance of fibrin from the lung. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:L573-9. [PMID: 10484465 DOI: 10.1152/ajplung.1999.277.3.l573] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In vitro studies have demonstrated that the binding of urokinase-type plasminogen activator (uPA) to its cell surface receptor (uPAR) greatly accelerates plasminogen activation. However, the role of uPAR in clearing abnormal fibrin deposits from the lung is uncertain. Knowing that uPA binding to uPAR is species specific, we used adenoviral vectors to transfer human or murine uPA genes into human or mouse epithelial cells in vitro and to mouse lungs in vivo. By measuring degradation of fluorescein-labeled fibrin, we found that uPA lysed fibrin matrices more efficiently when expressed in cells of the same species. A monoclonal antibody that blocks the binding of human uPA to human uPAR suppressed fibrin degradation by human cells expressing human uPA but not murine uPA. Importantly, 3 days after intratracheal delivery of the vectors, mice receiving murine uPA transgenes degraded fibrin matrices formed within their air spaces more efficiently than animals transduced with human uPA genes. These results show that uPA bound to uPAR increases the efficiency of fibrinolysis on epithelial cell surfaces in a biologically relevant fashion.
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