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Knudsen L, Hummel B, Wrede C, Zimmermann R, Perlman CE, Smith BJ. Acinar micromechanics in health and lung injury: what we have learned from quantitative morphology. Front Physiol 2023; 14:1142221. [PMID: 37025383 PMCID: PMC10070844 DOI: 10.3389/fphys.2023.1142221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 03/09/2023] [Indexed: 04/08/2023] Open
Abstract
Within the pulmonary acini ventilation and blood perfusion are brought together on a huge surface area separated by a very thin blood-gas barrier of tissue components to allow efficient gas exchange. During ventilation pulmonary acini are cyclically subjected to deformations which become manifest in changes of the dimensions of both alveolar and ductal airspaces as well as the interalveolar septa, composed of a dense capillary network and the delicate tissue layer forming the blood-gas barrier. These ventilation-related changes are referred to as micromechanics. In lung diseases, abnormalities in acinar micromechanics can be linked with injurious stresses and strains acting on the blood-gas barrier. The mechanisms by which interalveolar septa and the blood-gas barrier adapt to an increase in alveolar volume have been suggested to include unfolding, stretching, or changes in shape other than stretching and unfolding. Folding results in the formation of pleats in which alveolar epithelium is not exposed to air and parts of the blood-gas barrier are folded on each other. The opening of a collapsed alveolus (recruitment) can be considered as an extreme variant of septal wall unfolding. Alveolar recruitment can be detected with imaging techniques which achieve light microscopic resolution. Unfolding of pleats and stretching of the blood-gas barrier, however, require electron microscopic resolution to identify the basement membrane. While stretching results in an increase of the area of the basement membrane, unfolding of pleats and shape changes do not. Real time visualization of these processes, however, is currently not possible. In this review we provide an overview of septal wall micromechanics with focus on unfolding/folding as well as stretching. At the same time we provide a state-of-the-art design-based stereology methodology to quantify microarchitecture of alveoli and interalveolar septa based on different imaging techniques and design-based stereology.
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Affiliation(s)
- Lars Knudsen
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany
- Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Centre for Lung Research (DZL), Hannover, Germany
| | - Benjamin Hummel
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany
| | - Christoph Wrede
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany
- Research Core Unit Electron Microscopy, Hannover Medical School, Hannover, Germany
| | - Richard Zimmermann
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany
| | - Carrie E Perlman
- Department of Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, United States
| | - Bradford J Smith
- Department of Bioengineering, College of Engineering Design and Computing, University of Colorado Denver | Anschutz Medical Campus, Aurora, CO, United States
- Department of Pediatric Pulmonary and Sleep Medicine, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
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2
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Sengupta A, Roldan N, Kiener M, Froment L, Raggi G, Imler T, de Maddalena L, Rapet A, May T, Carius P, Schneider-Daum N, Lehr CM, Kruithof-de Julio M, Geiser T, Marti TM, Stucki JD, Hobi N, Guenat OT. A New Immortalized Human Alveolar Epithelial Cell Model to Study Lung Injury and Toxicity on a Breathing Lung-On-Chip System. FRONTIERS IN TOXICOLOGY 2022; 4:840606. [PMID: 35832493 PMCID: PMC9272139 DOI: 10.3389/ftox.2022.840606] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 05/09/2022] [Indexed: 12/13/2022] Open
Abstract
The evaluation of inhalation toxicity, drug safety and efficacy assessment, as well as the investigation of complex disease pathomechanisms, are increasingly relying on in vitro lung models. This is due to the progressive shift towards human-based systems for more predictive and translational research. While several cellular models are currently available for the upper airways, modelling the distal alveolar region poses several constraints that make the standardization of reliable alveolar in vitro models relatively difficult. In this work, we present a new and reproducible alveolar in vitro model, that combines a human derived immortalized alveolar epithelial cell line (AXiAEC) and organ-on-chip technology mimicking the lung alveolar biophysical environment (AXlung-on-chip). The latter mimics key features of the in vivo alveolar milieu: breathing-like 3D cyclic stretch (10% linear strain, 0.2 Hz frequency) and an ultrathin, porous and elastic membrane. AXiAECs cultured on-chip were characterized for their alveolar epithelial cell markers by gene and protein expression. Cell barrier properties were examined by TER (Transbarrier Electrical Resistance) measurement and tight junction formation. To establish a physiological model for the distal lung, AXiAECs were cultured for long-term at air-liquid interface (ALI) on-chip. To this end, different stages of alveolar damage including inflammation (via exposure to bacterial lipopolysaccharide) and the response to a profibrotic mediator (via exposure to Transforming growth factor β1) were analyzed. In addition, the expression of relevant host cell factors involved in SARS-CoV-2 infection was investigated to evaluate its potential application for COVID-19 studies. This study shows that AXiAECs cultured on the AXlung-on-chip exhibit an enhanced in vivo-like alveolar character which is reflected into: 1) Alveolar type 1 (AT1) and 2 (AT2) cell specific phenotypes, 2) tight barrier formation (with TER above 1,000 Ω cm2) and 3) reproducible long-term preservation of alveolar characteristics in nearly physiological conditions (co-culture, breathing, ALI). To the best of our knowledge, this is the first time that a primary derived alveolar epithelial cell line on-chip representing both AT1 and AT2 characteristics is reported. This distal lung model thereby represents a valuable in vitro tool to study inhalation toxicity, test safety and efficacy of drug compounds and characterization of xenobiotics.
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Affiliation(s)
- Arunima Sengupta
- Organs-on-Chip Technologies, ARTORG Center for Biomedical Engineering, University of Bern, Bern, Switzerland
| | - Nuria Roldan
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Mirjam Kiener
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, Bern, Switzerland.,Department for BioMedical Research DBMR, Urology Research Laboratory, University of Bern, Bern, Switzerland
| | - Laurène Froment
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Giulia Raggi
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Theo Imler
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | | | - Aude Rapet
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | | | - Patrick Carius
- Department of Drug Delivery (DDEL), Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Saarbrücken, Germany.,Department of Pharmacy, Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbrücken, Germany
| | - Nicole Schneider-Daum
- Department of Drug Delivery (DDEL), Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Saarbrücken, Germany.,Department of Pharmacy, Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbrücken, Germany
| | - Claus-Michael Lehr
- Department of Drug Delivery (DDEL), Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Saarbrücken, Germany.,Department of Pharmacy, Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbrücken, Germany
| | - Marianna Kruithof-de Julio
- Department for BioMedical Research DBMR, Urology Research Laboratory, University of Bern, Bern, Switzerland
| | - Thomas Geiser
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, Bern, Switzerland
| | - Thomas Michael Marti
- Department of General Thoracic Surgery, Inselspital, Bern University Hospital, Bern, Switzerland
| | - Janick D Stucki
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Nina Hobi
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Olivier T Guenat
- Organs-on-Chip Technologies, ARTORG Center for Biomedical Engineering, University of Bern, Bern, Switzerland.,Department of Pulmonary Medicine, Inselspital, Bern University Hospital, Bern, Switzerland.,Department of General Thoracic Surgery, Inselspital, Bern University Hospital, Bern, Switzerland
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3
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Novak C, Ballinger MN, Ghadiali S. Mechanobiology of Pulmonary Diseases: A Review of Engineering Tools to Understand Lung Mechanotransduction. J Biomech Eng 2021; 143:110801. [PMID: 33973005 PMCID: PMC8299813 DOI: 10.1115/1.4051118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 05/01/2021] [Indexed: 12/17/2022]
Abstract
Cells within the lung micro-environment are continuously subjected to dynamic mechanical stimuli which are converted into biochemical signaling events in a process known as mechanotransduction. In pulmonary diseases, the abrogated mechanical conditions modify the homeostatic signaling which influences cellular phenotype and disease progression. The use of in vitro models has significantly expanded our understanding of lung mechanotransduction mechanisms. However, our ability to match complex facets of the lung including three-dimensionality, multicellular interactions, and multiple simultaneous forces is limited and it has proven difficult to replicate and control these factors in vitro. The goal of this review is to (a) outline the anatomy of the pulmonary system and the mechanical stimuli that reside therein, (b) describe how disease impacts the mechanical micro-environment of the lung, and (c) summarize how existing in vitro models have contributed to our current understanding of pulmonary mechanotransduction. We also highlight critical needs in the pulmonary mechanotransduction field with an emphasis on next-generation devices that can simulate the complex mechanical and cellular environment of the lung. This review provides a comprehensive basis for understanding the current state of knowledge in pulmonary mechanotransduction and identifying the areas for future research.
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Affiliation(s)
- Caymen Novak
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, The Davis Heart and Lung Research Institute, The Ohio State University, Wexner Medical Center, 473 West 12th Avenue, Columbus, OH 43210
| | - Megan N. Ballinger
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, The Davis Heart and Lung Research Institute, The Ohio State University, Wexner Medical Center, 473 West 12th Avenue, Columbus, OH 43210
| | - Samir Ghadiali
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, The Davis Heart and Lung Research Institute, The Ohio State University, Wexner Medical Center, 473 West 12th Avenue, Columbus, OH 43210; Department of Biomedical Engineering, The Ohio State University, 2124N Fontana Labs, 140 West 19th Avenue, Columbus, OH 43210
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Kolb P, Schundner A, Frick M, Gottschalk KE. In Vitro Measurements of Cellular Forces and their Importance in the Lung-From the Sub- to the Multicellular Scale. Life (Basel) 2021; 11:691. [PMID: 34357063 PMCID: PMC8307149 DOI: 10.3390/life11070691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/09/2021] [Accepted: 07/09/2021] [Indexed: 02/07/2023] Open
Abstract
Throughout life, the body is subjected to various mechanical forces on the organ, tissue, and cellular level. Mechanical stimuli are essential for organ development and function. One organ whose function depends on the tightly connected interplay between mechanical cell properties, biochemical signaling, and external forces is the lung. However, altered mechanical properties or excessive mechanical forces can also drive the onset and progression of severe pulmonary diseases. Characterizing the mechanical properties and forces that affect cell and tissue function is therefore necessary for understanding physiological and pathophysiological mechanisms. In recent years, multiple methods have been developed for cellular force measurements at multiple length scales, from subcellular forces to measuring the collective behavior of heterogeneous cellular networks. In this short review, we give a brief overview of the mechanical forces at play on the cellular level in the lung. We then focus on the technological aspects of measuring cellular forces at many length scales. We describe tools with a subcellular resolution and elaborate measurement techniques for collective multicellular units. Many of the technologies described are by no means restricted to lung research and have already been applied successfully to cells from various other tissues. However, integrating the knowledge gained from these multi-scale measurements in a unifying framework is still a major future challenge.
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Affiliation(s)
- Peter Kolb
- Institute of Experimental Physics, Ulm University, 89069 Ulm, Germany;
| | - Annika Schundner
- Institute of General Physiology, Ulm University, 89069 Ulm, Germany;
| | - Manfred Frick
- Institute of General Physiology, Ulm University, 89069 Ulm, Germany;
| | - Kay-E. Gottschalk
- Institute of Experimental Physics, Ulm University, 89069 Ulm, Germany;
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5
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Kiener M, Roldan N, Machahua C, Sengupta A, Geiser T, Guenat OT, Funke-Chambour M, Hobi N, Kruithof-de Julio M. Human-Based Advanced in vitro Approaches to Investigate Lung Fibrosis and Pulmonary Effects of COVID-19. Front Med (Lausanne) 2021; 8:644678. [PMID: 34026781 PMCID: PMC8139419 DOI: 10.3389/fmed.2021.644678] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 04/01/2021] [Indexed: 12/15/2022] Open
Abstract
The coronavirus disease 2019 (COVID-19) pandemic has caused considerable socio-economic burden, which fueled the development of treatment strategies and vaccines at an unprecedented speed. However, our knowledge on disease recovery is sparse and concerns about long-term pulmonary impairments are increasing. Causing a broad spectrum of symptoms, COVID-19 can manifest as acute respiratory distress syndrome (ARDS) in the most severely affected patients. Notably, pulmonary infection with Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), the causing agent of COVID-19, induces diffuse alveolar damage (DAD) followed by fibrotic remodeling and persistent reduced oxygenation in some patients. It is currently not known whether tissue scaring fully resolves or progresses to interstitial pulmonary fibrosis. The most aggressive form of pulmonary fibrosis is idiopathic pulmonary fibrosis (IPF). IPF is a fatal disease that progressively destroys alveolar architecture by uncontrolled fibroblast proliferation and the deposition of collagen and extracellular matrix (ECM) proteins. It is assumed that micro-injuries to the alveolar epithelium may be induced by inhalation of micro-particles, pathophysiological mechanical stress or viral infections, which can result in abnormal wound healing response. However, the exact underlying causes and molecular mechanisms of lung fibrosis are poorly understood due to the limited availability of clinically relevant models. Recently, the emergence of SARS-CoV-2 with the urgent need to investigate its pathogenesis and address drug options, has led to the broad application of in vivo and in vitro models to study lung diseases. In particular, advanced in vitro models including precision-cut lung slices (PCLS), lung organoids, 3D in vitro tissues and lung-on-chip (LOC) models have been successfully employed for drug screens. In order to gain a deeper understanding of SARS-CoV-2 infection and ultimately alveolar tissue regeneration, it will be crucial to optimize the available models for SARS-CoV-2 infection in multicellular systems that recapitulate tissue regeneration and fibrotic remodeling. Current evidence for SARS-CoV-2 mediated pulmonary fibrosis and a selection of classical and novel lung models will be discussed in this review.
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Affiliation(s)
- Mirjam Kiener
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department for BioMedical Research DBMR, Urology Research Laboratory, University of Bern, Bern, Switzerland
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Nuria Roldan
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Carlos Machahua
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department for BioMedical Research DBMR, Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Arunima Sengupta
- Organs-on-Chip Technologies, ARTORG Center for Biomedical Engineering, University of Bern, Bern, Switzerland
| | - Thomas Geiser
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department for BioMedical Research DBMR, Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Olivier Thierry Guenat
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Organs-on-Chip Technologies, ARTORG Center for Biomedical Engineering, University of Bern, Bern, Switzerland
- Department of General Thoracic Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Manuela Funke-Chambour
- Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department for BioMedical Research DBMR, Department of Pulmonary Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Nina Hobi
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
| | - Marianna Kruithof-de Julio
- Department for BioMedical Research DBMR, Urology Research Laboratory, University of Bern, Bern, Switzerland
- Alveolix AG, Swiss Organs-on-Chip Innovation, Bern, Switzerland
- Organoid Core, Department for BioMedical Research, University of Bern, Bern, Switzerland
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6
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Hernández-Cáceres MP, Munoz L, Pradenas JM, Pena F, Lagos P, Aceiton P, Owen GI, Morselli E, Criollo A, Ravasio A, Bertocchi C. Mechanobiology of Autophagy: The Unexplored Side of Cancer. Front Oncol 2021; 11:632956. [PMID: 33718218 PMCID: PMC7952994 DOI: 10.3389/fonc.2021.632956] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 02/01/2021] [Indexed: 12/12/2022] Open
Abstract
Proper execution of cellular function, maintenance of cellular homeostasis and cell survival depend on functional integration of cellular processes and correct orchestration of cellular responses to stresses. Cancer transformation is a common negative consequence of mismanagement of coordinated response by the cell. In this scenario, by maintaining the balance among synthesis, degradation, and recycling of cytosolic components including proteins, lipids, and organelles the process of autophagy plays a central role. Several environmental stresses activate autophagy, among those hypoxia, DNA damage, inflammation, and metabolic challenges such as starvation. In addition to these chemical challenges, there is a requirement for cells to cope with mechanical stresses stemming from their microenvironment. Cells accomplish this task by activating an intrinsic mechanical response mediated by cytoskeleton active processes and through mechanosensitive protein complexes which interface the cells with their mechano-environment. Despite autophagy and cell mechanics being known to play crucial transforming roles during oncogenesis and malignant progression their interplay is largely overlooked. In this review, we highlight the role of physical forces in autophagy regulation and their potential implications in both physiological as well as pathological conditions. By taking a mechanical perspective, we wish to stimulate novel questions to further the investigation of the mechanical requirements of autophagy and appreciate the extent to which mechanical signals affect this process.
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Affiliation(s)
- Maria Paz Hernández-Cáceres
- Laboratory of Autophagy and Metabolism, Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica De Chile, Santiago, Chile
| | - Leslie Munoz
- Laboratory for Mechanobiology of Transforming Systems, Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
- Laboratory for Molecular Mechanics of Cell Adhesion, Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica De Chile, Santiago, Chile
| | - Javiera M. Pradenas
- Advanced Center for Chronic Diseases (ACCDiS), Santiago, Chile
- Laboratory of Investigation in Oncology, Faculty of Biological Sciences Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Francisco Pena
- Laboratory for Mechanobiology of Transforming Systems, Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
- Laboratory for Molecular Mechanics of Cell Adhesion, Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica De Chile, Santiago, Chile
| | - Pablo Lagos
- Laboratory of Autophagy and Metabolism, Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica De Chile, Santiago, Chile
| | - Pablo Aceiton
- Laboratory for Mechanobiology of Transforming Systems, Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
- Laboratory for Molecular Mechanics of Cell Adhesion, Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica De Chile, Santiago, Chile
| | - Gareth I. Owen
- Advanced Center for Chronic Diseases (ACCDiS), Santiago, Chile
- Laboratory of Investigation in Oncology, Faculty of Biological Sciences Pontificia Universidad Católica de Chile, Santiago, Chile
- Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
| | - Eugenia Morselli
- Laboratory of Autophagy and Metabolism, Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica De Chile, Santiago, Chile
- Autophagy Research Center, Santiago de Chile, Chile
| | - Alfredo Criollo
- Advanced Center for Chronic Diseases (ACCDiS), Santiago, Chile
- Autophagy Research Center, Santiago de Chile, Chile
- Facultad De Odontología, Instituto De Investigación En Ciencias Odontológicas (ICOD), Universidad De Chile, Santiago, Chile
| | - Andrea Ravasio
- Laboratory for Mechanobiology of Transforming Systems, Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Cristina Bertocchi
- Laboratory for Molecular Mechanics of Cell Adhesion, Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica De Chile, Santiago, Chile
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Diem K, Fauler M, Fois G, Hellmann A, Winokurow N, Schumacher S, Kranz C, Frick M. Mechanical stretch activates piezo1 in caveolae of alveolar type I cells to trigger ATP release and paracrine stimulation of surfactant secretion from alveolar type II cells. FASEB J 2020; 34:12785-12804. [PMID: 32744386 DOI: 10.1096/fj.202000613rrr] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 07/14/2020] [Accepted: 07/16/2020] [Indexed: 12/12/2022]
Abstract
Secretion of pulmonary surfactant in the alveoli of the lungs is essential to maintain lung function. Stretching of alveoli during lung inflation is the main trigger for surfactant secretion. Yet, the molecular mechanisms how mechanical distension of alveoli results in surfactant secretion are still elusive. The alveolar epithelium consists of alveolar epithelial type I (ATI) and surfactant secreting type II (ATII) cells. ATI, but not ATII cells, express caveolae, small plasma membrane invaginations that can respond to plasma membrane stresses and serve mechanotransductive roles. Within this study, we investigated the role of caveolae as mechanosensors in the alveolus. We generated a human caveolin-1 knockout ATI cell (hAELVicav-/- ) using CRISPR/Cas9. Wildtype (hAELViwt ) and hAELVicav-/- cells grown on flexible membranes responded to increasing stretch amplitudes with rises in intracellular Ca2+ . The response was less frequent and started at higher stretch amplitudes in hAELVicav-/- cells. Stretch-induced Ca2+ -signals depended on Ca2+ -entry via piezo1 channels, localized within caveolae in hAELViwt and primary ATI cells. Ca2+ -entry via piezo1 activated pannexin-1 hemichannels resulting in ATP release from ATI cells. ATP release was reduced in hAELVicav-/- cells. In co-cultures resembling the alveolar epithelium, released ATP stimulated Ca2+ signals and surfactant secretion from neighboring ATII cells when co-cultured with hAELViwt but not hAELVicav-/- cells. In summary, we propose that caveolae in ATI cells are mechanosensors within alveoli regulating stretch-induced surfactant secretion from ATII cells.
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Affiliation(s)
- Kathrin Diem
- Institute of General Physiology, Ulm University, Ulm, Germany
| | - Michael Fauler
- Institute of General Physiology, Ulm University, Ulm, Germany
| | - Giorgio Fois
- Institute of General Physiology, Ulm University, Ulm, Germany
| | - Andreas Hellmann
- Institute of Analytical and Bioanalytical Chemistry, Ulm University, Ulm, Germany
| | - Natalie Winokurow
- Institute of Molecular and Cellular Anatomy, Ulm University, Ulm, Germany
| | - Stefan Schumacher
- Institute of Molecular and Cellular Anatomy, Ulm University, Ulm, Germany
| | - Christine Kranz
- Institute of Analytical and Bioanalytical Chemistry, Ulm University, Ulm, Germany
| | - Manfred Frick
- Institute of General Physiology, Ulm University, Ulm, Germany
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Lipid-Protein and Protein-Protein Interactions in the Pulmonary Surfactant System and Their Role in Lung Homeostasis. Int J Mol Sci 2020; 21:ijms21103708. [PMID: 32466119 PMCID: PMC7279303 DOI: 10.3390/ijms21103708] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 05/22/2020] [Accepted: 05/22/2020] [Indexed: 12/12/2022] Open
Abstract
Pulmonary surfactant is a lipid/protein complex synthesized by the alveolar epithelium and secreted into the airspaces, where it coats and protects the large respiratory air–liquid interface. Surfactant, assembled as a complex network of membranous structures, integrates elements in charge of reducing surface tension to a minimum along the breathing cycle, thus maintaining a large surface open to gas exchange and also protecting the lung and the body from the entrance of a myriad of potentially pathogenic entities. Different molecules in the surfactant establish a multivalent crosstalk with the epithelium, the immune system and the lung microbiota, constituting a crucial platform to sustain homeostasis, under health and disease. This review summarizes some of the most important molecules and interactions within lung surfactant and how multiple lipid–protein and protein–protein interactions contribute to the proper maintenance of an operative respiratory surface.
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Abstract
The pulmonary blood-gas barrier represents a remarkable feat of engineering. It achieves the exquisite thinness needed for gas exchange by diffusion, the strength to withstand the stresses and strains of repetitive and changing ventilation, and the ability to actively maintain itself under varied demands. Understanding the design principles of this barrier is essential to understanding a variety of lung diseases, and to successfully regenerating or artificially recapitulating the barrier ex vivo. Many classical studies helped to elucidate the unique structure and morphology of the mammalian blood-gas barrier, and ongoing investigations have helped to refine these descriptions and to understand the biological aspects of blood-gas barrier function and regulation. This article reviews the key features of the blood-gas barrier that enable achievement of the necessary design criteria and describes the mechanical environment to which the barrier is exposed. It then focuses on the biological and mechanical components of the barrier that preserve integrity during homeostasis, but which may be compromised in certain pathophysiological states, leading to disease. Finally, this article summarizes recent key advances in efforts to engineer the blood-gas barrier ex vivo, using the platforms of lung-on-a-chip and tissue-engineered whole lungs. © 2020 American Physiological Society. Compr Physiol 10:415-452, 2020.
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Affiliation(s)
- Katherine L. Leiby
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA
- Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Micha Sam Brickman Raredon
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA
- Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Laura E. Niklason
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA
- Yale School of Medicine, Yale University, New Haven, Connecticut, USA
- Department of Anesthesiology, Yale University, New Haven, Connecticut, USA
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10
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Rühl N, Lopez-Rodriguez E, Albert K, Smith BJ, Weaver TE, Ochs M, Knudsen L. Surfactant Protein B Deficiency Induced High Surface Tension: Relationship between Alveolar Micromechanics, Alveolar Fluid Properties and Alveolar Epithelial Cell Injury. Int J Mol Sci 2019; 20:ijms20174243. [PMID: 31480246 PMCID: PMC6747270 DOI: 10.3390/ijms20174243] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 08/24/2019] [Accepted: 08/26/2019] [Indexed: 11/16/2022] Open
Abstract
High surface tension at the alveolar air-liquid interface is a typical feature of acute and chronic lung injury. However, the manner in which high surface tension contributes to lung injury is not well understood. This study investigated the relationship between abnormal alveolar micromechanics, alveolar epithelial injury, intra-alveolar fluid properties and remodeling in the conditional surfactant protein B (SP-B) knockout mouse model. Measurements of pulmonary mechanics, broncho-alveolar lavage fluid (BAL), and design-based stereology were performed as a function of time of SP-B deficiency. After one day of SP-B deficiency the volume of alveolar fluid V(alvfluid,par) as well as BAL protein and albumin levels were normal while the surface area of injured alveolar epithelium S(AEinjure,sep) was significantly increased. Alveoli and alveolar surface area could be recruited by increasing the air inflation pressure. Quasi-static pressure-volume loops were characterized by an increased hysteresis while the inspiratory capacity was reduced. After 3 days, an increase in V(alvfluid,par) as well as BAL protein and albumin levels were linked with a failure of both alveolar recruitment and airway pressure-dependent redistribution of alveolar fluid. Over time, V(alvfluid,par) increased exponentially with S(AEinjure,sep). In conclusion, high surface tension induces alveolar epithelial injury prior to edema formation. After passing a threshold, epithelial injury results in vascular leakage and exponential accumulation of alveolar fluid critically hampering alveolar recruitability.
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Affiliation(s)
- Nina Rühl
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover 30625, Germany
| | - Elena Lopez-Rodriguez
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover 30625, Germany
- Biomedical Research in Endstage and Obstructive Lung Diseases (BREATH), Member of the German Center for Lung Research (DLZ), Hannover 30625, Germany
- REBIRTH, Cluster of Excellence, Hannover 30625, Germany
- Institute of Vegetative Anatomy, Charite, Berlin 10117, Germany
| | - Karolin Albert
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover 30625, Germany
| | - Bradford J Smith
- Department of Bioengineering, University of Colorado Denver, Denver, CO 80045, USA
| | - Timothy E Weaver
- Division of Pulmonary Biology, University of Cincinnati College of Medicine, Cincinnati, OH 45221, USA
| | - Matthias Ochs
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover 30625, Germany
- Biomedical Research in Endstage and Obstructive Lung Diseases (BREATH), Member of the German Center for Lung Research (DLZ), Hannover 30625, Germany
- REBIRTH, Cluster of Excellence, Hannover 30625, Germany
- Institute of Vegetative Anatomy, Charite, Berlin 10117, Germany
| | - Lars Knudsen
- Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover 30625, Germany.
- Biomedical Research in Endstage and Obstructive Lung Diseases (BREATH), Member of the German Center for Lung Research (DLZ), Hannover 30625, Germany.
- REBIRTH, Cluster of Excellence, Hannover 30625, Germany.
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11
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Wittekindt OH, Dietl P. Aquaporins in the lung. Pflugers Arch 2018; 471:519-532. [PMID: 30397774 PMCID: PMC6435619 DOI: 10.1007/s00424-018-2232-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 10/04/2018] [Accepted: 10/25/2018] [Indexed: 12/22/2022]
Abstract
The lung is the interface between air and blood where the exchange of oxygen and carbon dioxide occurs. The surface liquid that is directly exposed to the gaseous compartment covers both conducting airways and respiratory zone and forms the air-liquid interface. The barrier that separates this lining fluid of the airways and alveoli from the extracellular compartment is the pulmonary epithelium. The volume of the lining fluid must be kept in a range that guarantees an appropriate gas exchange and other functions, such as mucociliary clearance. It is generally accepted that this is maintained by balancing resorptive and secretory fluid transport across the pulmonary epithelium. Whereas osmosis is considered as the exclusive principle of fluid transport in the airways, filtration may contribute to alveolar fluid accumulation under pathologic conditions. Aquaporins (AQP) facilitate water flux across cell membranes, and as such, they provide a transcellular route for water transport across epithelia. However, their contribution to near-isosmolar fluid conditions in the lung still remains elusive. Herein, we discuss the role of AQPs in the lung with regard to fluid homeostasis across the respiratory epithelium.
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Affiliation(s)
- Oliver H Wittekindt
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
| | - Paul Dietl
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
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12
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Knudsen L, Ochs M. The micromechanics of lung alveoli: structure and function of surfactant and tissue components. Histochem Cell Biol 2018; 150:661-676. [PMID: 30390118 PMCID: PMC6267411 DOI: 10.1007/s00418-018-1747-9] [Citation(s) in RCA: 206] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/19/2018] [Indexed: 12/14/2022]
Abstract
The mammalian lung´s structural design is optimized to serve its main function: gas exchange. It takes place in the alveolar region (parenchyma) where air and blood are brought in close proximity over a large surface. Air reaches the alveolar lumen via a conducting airway tree. Blood flows in a capillary network embedded in inter-alveolar septa. The barrier between air and blood consists of a continuous alveolar epithelium (a mosaic of type I and type II alveolar epithelial cells), a continuous capillary endothelium and the connective tissue layer in-between. By virtue of its respiratory movements, the lung has to withstand mechanical challenges throughout life. Alveoli must be protected from over-distension as well as from collapse by inherent stabilizing factors. The mechanical stability of the parenchyma is ensured by two components: a connective tissue fiber network and the surfactant system. The connective tissue fibers form a continuous tensegrity (tension + integrity) backbone consisting of axial, peripheral and septal fibers. Surfactant (surface active agent) is the secretory product of type II alveolar epithelial cells and covers the alveolar epithelium as a biophysically active thin and continuous film. Here, we briefly review the structural components relevant for gas exchange. Then we describe our current understanding of how these components function under normal conditions and how lung injury results in dysfunction of alveolar micromechanics finally leading to lung fibrosis.
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Affiliation(s)
- Lars Knudsen
- Institute of Functional and Applied Anatomy, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.,Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Center for Lung Research (DZL), Hannover, Germany.,REBIRTH Cluster of Excellence, Hannover, Germany
| | - Matthias Ochs
- Institute of Functional and Applied Anatomy, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany. .,Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Center for Lung Research (DZL), Hannover, Germany. .,REBIRTH Cluster of Excellence, Hannover, Germany.
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13
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Medium throughput breathing human primary cell alveolus-on-chip model. Sci Rep 2018; 8:14359. [PMID: 30254327 PMCID: PMC6156575 DOI: 10.1038/s41598-018-32523-x] [Citation(s) in RCA: 102] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 09/10/2018] [Indexed: 12/12/2022] Open
Abstract
Organs-on-chips have the potential to improve drug development efficiency and decrease the need for animal testing. For the successful integration of these devices in research and industry, they must reproduce in vivo contexts as closely as possible and be easy to use. Here, we describe a ‘breathing’ lung-on-chip array equipped with a passive medium exchange mechanism that provide an in vivo-like environment to primary human lung alveolar cells (hAEpCs) and primary lung endothelial cells. This configuration allows the preservation of the phenotype and the function of hAEpCs for several days, the conservation of the epithelial barrier functionality, while enabling simple sampling of the supernatant from the basal chamber. In addition, the chip design increases experimental throughput and enables trans-epithelial electrical resistance measurements using standard equipment. Biological validation revealed that human primary alveolar type I (ATI) and type II-like (ATII) epithelial cells could be successfully cultured on the chip over multiple days. Moreover, the effect of the physiological cyclic strain showed that the epithelial barrier permeability was significantly affected. Long-term co-culture of primary human lung epithelial and endothelial cells demonstrated the potential of the lung-on-chip array for reproducible cell culture under physiological conditions. Thus, this breathing lung-on-chip array, in combination with patients’ primary ATI, ATII, and lung endothelial cells, has the potential to become a valuable tool for lung research, drug discovery and precision medicine.
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14
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Martínez‐Calle M, Olmeda B, Dietl P, Frick M, Pérez‐Gil J. Pulmonary surfactant protein SP‐B promotes exocytosis of lamellar bodies in alveolar type II cells. FASEB J 2018. [DOI: 10.1096/fj.201701462rr] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Marta Martínez‐Calle
- Department of Biochemistry and Molecular BiologyFaculty of BiologyComplutense UniversityMadridSpain
- Research Institute “Hospital 12 de Octubre”Complutense UniversityMadridSpain
| | - Bárbara Olmeda
- Department of Biochemistry and Molecular BiologyFaculty of BiologyComplutense UniversityMadridSpain
- Research Institute “Hospital 12 de Octubre”Complutense UniversityMadridSpain
| | - Paul Dietl
- Institute of General PhysiologyUlm UniversityUlmGermany
| | - Manfred Frick
- Institute of General PhysiologyUlm UniversityUlmGermany
| | - Jesús Pérez‐Gil
- Department of Biochemistry and Molecular BiologyFaculty of BiologyComplutense UniversityMadridSpain
- Research Institute “Hospital 12 de Octubre”Complutense UniversityMadridSpain
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15
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Knudsen L, Ruppert C, Ochs M. Tissue remodelling in pulmonary fibrosis. Cell Tissue Res 2016; 367:607-626. [PMID: 27981380 DOI: 10.1007/s00441-016-2543-2] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 11/19/2016] [Indexed: 12/16/2022]
Abstract
Many lung diseases result in fibrotic remodelling. Fibrotic lung disorders can be divided into diseases with known and unknown aetiology. Among those with unknown aetiology, idiopathic pulmonary fibrosis (IPF) is a common diagnosis. Because of its progressive character leading to a rapid decline in lung function, it is a fatal disease with poor prognosis and limited therapeutic options. Thus, IPF has motivated many studies in the last few decades in order to increase our mechanistic understanding of the pathogenesis of the disease. The current concept suggests an ongoing injury of the alveolar epithelium, an impaired regeneration capacity, alveolar collapse and, finally, a fibroproliferative response. The origin of lung injury remains elusive but a diversity of factors, which will be discussed in this article, has been shown to be associated with IPF. Alveolar epithelial type II (AE2) cells play a key role in lung fibrosis and their crucial role for epithelial regeneration, stabilisation of alveoli and interaction with fibroblasts, all known to be responsible for collagen deposition, will be illustrated. Whereas mechanisms of collagen deposition and fibroproliferation are the focus of many studies in the field, the awareness of other mechanisms in this disease is currently limited to biochemical and imaging studies including quantitative assessments of lung structure in IPF and animal models assigning alveolar collapse and collapse induration crucial roles for the degradation of the lung resulting in de-aeration and loss of surface area. Dysfunctional AE2 cells, instable alveoli and mechanical stress trigger remodelling that consists of collapsed alveoli absorbed by fibrotic tissue (i.e., collapse induration).
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Affiliation(s)
- Lars Knudsen
- Institute of Functional and Applied Anatomy, Hannover Medical School, Carl-Neuberg Strasse 1, 30625, Hannover, Germany. .,Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Center for Lung Research (DZL), Hannover Medical School, Hannover, Germany. .,REBIRTH, Cluster of Excellence, Hannover Medical School, Hannover, Germany.
| | - Clemens Ruppert
- Department of Internal Medicine, Justus-Liebig-University Giessen, Giessen, Germany.,Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Universities of Giessen and Marburg, Giessen, Germany
| | - Matthias Ochs
- Institute of Functional and Applied Anatomy, Hannover Medical School, Carl-Neuberg Strasse 1, 30625, Hannover, Germany.,Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Center for Lung Research (DZL), Hannover Medical School, Hannover, Germany.,REBIRTH, Cluster of Excellence, Hannover Medical School, Hannover, Germany
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16
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Olmeda B, Martínez-Calle M, Pérez-Gil J. Pulmonary surfactant metabolism in the alveolar airspace: Biogenesis, extracellular conversions, recycling. Ann Anat 2016; 209:78-92. [PMID: 27773772 DOI: 10.1016/j.aanat.2016.09.008] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/22/2016] [Accepted: 09/25/2016] [Indexed: 01/03/2023]
Abstract
Pulmonary surfactant is a lipid-protein complex that lines and stabilizes the respiratory interface in the alveoli, allowing for gas exchange during the breathing cycle. At the same time, surfactant constitutes the first line of lung defense against pathogens. This review presents an updated view on the processes involved in biogenesis and intracellular processing of newly synthesized and recycled surfactant components, as well as on the extracellular surfactant transformations before and after the formation of the surface active film at the air-water interface. Special attention is paid to the crucial regulation of surfactant homeostasis, because its disruption is associated with several lung pathologies.
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Affiliation(s)
- Bárbara Olmeda
- Department of Biochemistry, Faculty of Biology, and Research Institute "Hospital 12 de Octubre", Complutense University, 28040 Madrid, Spain
| | - Marta Martínez-Calle
- Department of Biochemistry, Faculty of Biology, and Research Institute "Hospital 12 de Octubre", Complutense University, 28040 Madrid, Spain
| | - Jesus Pérez-Gil
- Department of Biochemistry, Faculty of Biology, and Research Institute "Hospital 12 de Octubre", Complutense University, 28040 Madrid, Spain.
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17
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Hobi N, Giolai M, Olmeda B, Miklavc P, Felder E, Walther P, Dietl P, Frick M, Pérez-Gil J, Haller T. A small key unlocks a heavy door: The essential function of the small hydrophobic proteins SP-B and SP-C to trigger adsorption of pulmonary surfactant lamellar bodies. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2124-34. [DOI: 10.1016/j.bbamcr.2016.04.028] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 04/15/2016] [Accepted: 04/27/2016] [Indexed: 02/07/2023]
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18
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Wu Y, Kharge AB, Perlman CE. Lung ventilation injures areas with discrete alveolar flooding, in a surface tension-dependent fashion. J Appl Physiol (1985) 2014; 117:788-96. [PMID: 25080924 DOI: 10.1152/japplphysiol.00569.2014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
With proteinaceous-liquid flooding of discrete alveoli, a model of the edema pattern in the acute respiratory distress syndrome, lung inflation over expands aerated alveoli adjacent to flooded alveoli. Theoretical considerations suggest that the overexpansion may be proportional to surface tension, T. Yet recent evidence indicates proteinaceous edema liquid may not elevate T. Thus whether the overexpansion is injurious is not known. Here, working in the isolated, perfused rat lung, we quantify fluorescence movement from the vasculature to the alveolar liquid phase as a measure of overdistension injury to the alveolar-capillary barrier. We label the perfusate with fluorescence; micropuncture a surface alveolus and instill a controlled volume of nonfluorescent liquid to obtain a micropunctured-but-aerated region (control group) or a region with discrete alveolar flooding; image the region at a constant transpulmonary pressure of 5 cmH2O; apply five ventilation cycles with a positive end-expiratory pressure of 0-20 cmH2O and tidal volume of 6 or 12 ml/kg; return the lung to a constant transpulmonary pressure of 5 cmH2O; and image for an additional 10 min. In aerated areas, ventilation is not injurious. With discrete alveolar flooding, all ventilation protocols cause sustained injury. Greater positive end-expiratory pressure or tidal volume increases injury. Furthermore, we determine T and find injury increases with T. Inclusion of either plasma proteins or Survanta in the flooding liquid does not alter T or injury. Inclusion of 2.7-10% albumin and 1% Survanta together, however, lowers T and injury. Contrary to expectation, albumin inclusion in our model facilitates exogenous surfactant activity.
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Affiliation(s)
- You Wu
- Chemistry, Chemical Biology & Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey
| | - Angana Banerjee Kharge
- Chemistry, Chemical Biology & Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey
| | - Carrie E Perlman
- Chemistry, Chemical Biology & Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey
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19
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Schürch D, Vanhecke D, Clift MJD, Raemy D, de Aberasturi DJ, Parak WJ, Gehr P, Petri-Fink A, Rothen-Rutishauser B. Modeling nanoparticle-alveolar epithelial cell interactions under breathing conditions using captive bubble surfactometry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:4924-32. [PMID: 24731173 DOI: 10.1021/la500307q] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Many advances have been made in recent years in cell culture models of the epithelial barrier of the lung from simple monolayers to complex 3-D systems employing different cell types. However, the vast majority of these models still present a static air-liquid interface which is unrealistic given the dynamic nature of breathing. We present here a method where epithelial lung cells are integrated into a system, the captive bubble surfactometer, which allows the cyclical compression and expansion of the surfactant film at the air-liquid interface, thus modeling the dynamics of breathing. We found that cellular uptake of deposited gold nanoparticles was significantly increased under the dynamic (breathing) conditions of compression and expansion as compared to static conditions. The method could be very useful for studying nanoparticle-alveolar lung cell interactions under breathing conditions for applications in nanomedicine and toxicology.
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Affiliation(s)
- David Schürch
- Adolphe Merkle Institute, University of Fribourg , Fribourg, Switzerland
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20
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Hobi N, Siber G, Bouzas V, Ravasio A, Pérez-Gil J, Haller T. Physiological variables affecting surface film formation by native lamellar body-like pulmonary surfactant particles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1842-50. [PMID: 24582711 DOI: 10.1016/j.bbamem.2014.02.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 02/14/2014] [Accepted: 02/19/2014] [Indexed: 12/17/2022]
Abstract
Pulmonary surfactant (PS) is a surface active complex of lipids and proteins that prevents the alveolar structures from collapsing and reduces the work of breathing by lowering the surface tension at the alveolar air-liquid interface (ALI). Surfactant is synthesized by the alveolar type II (AT II) cells, and it is stored in specialized organelles, the lamellar bodies (LBs), as tightly packed lipid bilayers. Upon secretion into the alveolar lining fluid, a large fraction of these particles retain most of their packed lamellar structure, giving rise to the term lamellar body like-particles (LBPs). Due to their stability in aqueous media, freshly secreted LBPs can be harvested from AT II cell preparations. However, when LBPs get in contact with an ALI, they quickly and spontaneously adsorb into a highly organized surface film. In the present study we investigated the adsorptive capacity of LBPs at an ALI under relevant physiological parameters that characterize the alveolar environment in homeostatic or in pathological conditions. Adsorption of LBPs at an ALI is highly sensitive to pH, temperature and albumin concentration and to a relatively lesser extent to changes in osmolarity or Ca(2+) concentrations in the physiological range. Furthermore, proteolysis of LBPs significantly decreases their adsorptive capacity confirming the important role of surfactant proteins in the formation of surface active films.
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Affiliation(s)
- Nina Hobi
- Department of Physiology and Medical Physics, Division of Physiology, Innsbruck Medical University, 6020 Innsbruck, Austria; Institute of General Physiology, University of Ulm, 89081 Ulm, Germany
| | - Gerlinde Siber
- Department of Physiology and Medical Physics, Division of Physiology, Innsbruck Medical University, 6020 Innsbruck, Austria
| | - Virginia Bouzas
- Department of Physiology and Medical Physics, Division of Physiology, Medical University Innsbruck, Fritz-Preglstr. 3 6020 Innsbruck, Austria
| | - Andrea Ravasio
- Department of Physiology and Medical Physics, Division of Physiology, Innsbruck Medical University, 6020 Innsbruck, Austria
| | - Jesus Pérez-Gil
- Department of Physiology and Medical Physics, Division of Physiology, Medical University Innsbruck, Fritz-Preglstr. 3 6020 Innsbruck, Austria
| | - Thomas Haller
- Department of Physiology and Medical Physics, Division of Physiology, Innsbruck Medical University, 6020 Innsbruck, Austria
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21
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Surfactant secretion in LRRK2 knock-out rats: changes in lamellar body morphology and rate of exocytosis. PLoS One 2014; 9:e84926. [PMID: 24465451 PMCID: PMC3897396 DOI: 10.1371/journal.pone.0084926] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 11/19/2013] [Indexed: 12/16/2022] Open
Abstract
Leucine-rich repeat kinase 2 (LRRK2) is known to play a role in the pathogenesis of various diseases including Parkinson disease, morbus Crohn, leprosy and cancer. LRRK2 is suggested to be involved in a number of cell biological processes such as vesicular trafficking, transcription, autophagy and lysosomal pathways. Recent histological studies of lungs of LRRK2 knock-out (LRRK2 -/-) mice revealed significantly enlarged lamellar bodies (LBs) in alveolar type II (ATII) epithelial cells. LBs are large, lysosome-related storage organelles for pulmonary surfactant, which is released into the alveolar lumen upon LB exocytosis. In this study we used high-resolution, subcellular live-cell imaging assays to investigate whether similar morphological changes can be observed in primary ATII cells from LRRK2 -/- rats and whether such changes result in altered LB exocytosis. Similarly to the report in mice, ATII cells from LRRK2 -/- rats contained significantly enlarged LBs resulting in a >50% increase in LB volume. Stimulation of ATII cells with ATP elicited LB exocytosis in a significantly increased proportion of cells from LRRK2 -/- animals. LRRK2 -/- cells also displayed increased intracellular Ca2+ release upon ATP treatment and significant triggering of LB exocytosis. These findings are in line with the strong Ca2+-dependence of LB fusion activity and suggest that LRRK2 -/- affects exocytic response in ATII cells via modulating intracellular Ca2+ signaling. Post-fusion regulation of surfactant secretion was unaltered. Actin coating of fused vesicles and subsequent vesicle compression to promote surfactant expulsion were comparable in cells from LRRK2 -/- and wt animals. Surprisingly, surfactant (phospholipid) release from LRRK2 -/- cells was reduced following stimulation of LB exocytosis possibly due to impaired LB maturation and surfactant loading of LBs. In summary our results suggest that LRRK2 -/- affects LB size, modulates intracellular Ca2+ signaling and promotes LB exocytosis upon stimulation of ATII cells with ATP.
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22
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Thompson KE, Korbmacher JP, Hecht E, Hobi N, Wittekindt OH, Dietl P, Kranz C, Frick M. Fusion-activated cation entry (FACE) via P2X₄ couples surfactant secretion and alveolar fluid transport. FASEB J 2013; 27:1772-83. [PMID: 23307836 DOI: 10.1096/fj.12-220533] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Two fundamental mechanisms within alveoli are essential for lung function: regulated fluid transport and secretion of surfactant. Surfactant is secreted via exocytosis of lamellar bodies (LBs) in alveolar type II (ATII) cells. We recently reported that LB exocytosis results in fusion-activated cation entry (FACE) via P2X₄ receptors on LBs. We propose that FACE, in addition to facilitating surfactant secretion, modulates alveolar fluid transport. Correlative fluorescence and atomic force microscopy revealed that FACE-dependent water influx correlated with individual fusion events in rat primary ATII cells. Moreover, ATII cell monolayers grown at air-liquid interface exhibited increases in short-circuit current (Isc) on stimulation with ATP or UTP. Both are potent agonists for LB exocytosis, but only ATP activates FACE. ATP, not UTP, elicited additional fusion-dependent increases in Isc. Overexpressing dominant-negative P2X₄ abrogated this effect by ∼50%, whereas potentiating P2X4 lead to ∼80% increase in Isc. Finally, we monitored changes in alveolar surface liquid (ASL) on ATII monolayers by confocal microscopy. Only stimulation with ATP, not UTP, led to a significant, fusion-dependent, 20% decrease in ASL, indicating apical-to-basolateral fluid transport across ATII monolayers. Our data support the first direct link between LB exocytosis, regulation of surfactant secretion, and transalveolar fluid resorption via FACE.
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23
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Hobi N, Ravasio A, Haller T. Interfacial stress affects rat alveolar type II cell signaling and gene expression. Am J Physiol Lung Cell Mol Physiol 2012; 303:L117-29. [PMID: 22610352 DOI: 10.1152/ajplung.00340.2011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous work from our group (Ravasio A, Hobi N, Bertocchi C, Jesacher A, Dietl P, Haller T. Am J Physiol Cell Physiol 300: C1456-C1465, 2011.) showed that contact of alveolar epithelial type II cells with an air-liquid interface (I(AL)) leads to a paradoxical situation. It is a potential threat that can cause cell injury, but also a Ca(2+)-dependent stimulus for surfactant secretion. Both events can be explained by the impact of interfacial tensile forces on cellular structures. Here, the strength of this mechanical stimulus became also apparent in microarray studies by a rapid and significant change on the transcriptional level. Cells challenged with an I(AL) in two different ways showed activation/inactivation of cellular pathways involved in stress response and defense, and a detailed Pubmatrix search identified genes associated with several lung diseases and injuries. Altogether, they suggest a close relationship of interfacial stress sensation with current models in alveolar micromechanics. Further similarities between I(AL) and cell stretch were found with respect to the underlying signaling events. The source of Ca(2+) was extracellular, and the transmembrane Ca(2+) entry pathway suggests the involvement of a mechanosensitive channel. We conclude that alveolar type II cells, due to their location and morphology, are specific sensors of the I(AL), but largely protected from interfacial stress by surfactant release.
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Affiliation(s)
- Nina Hobi
- Department of Physiology and Medical Physics, Division of Physiology, Innsbruck Medical University, Austria
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24
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Dietl P, Haller T, Frick M. Spatio-temporal aspects, pathways and actions of Ca(2+) in surfactant secreting pulmonary alveolar type II pneumocytes. Cell Calcium 2012; 52:296-302. [PMID: 22591642 DOI: 10.1016/j.ceca.2012.04.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 04/11/2012] [Accepted: 04/18/2012] [Indexed: 01/16/2023]
Abstract
The type II cell of the pulmonary alveolus is a polarized epithelial cell that secretes surfactant into the alveolar space by regulated exocytosis of lamellar bodies (LBs). This process consists of multiple sequential steps and is correlated to elevations of the cytoplasmic Ca(2+) concentration ([Ca(2+)](c)) required for extended periods of secretory activity. Both chemical (purinergic) and mechanical (cell stretch or exposure to an air-liquid interface) stimuli give rise to complex Ca(2+) signals (such as Ca(2+) peaks, spikes and plateaus) that differ in shape, origin and spatio-temporal behavior. This review summarizes current knowledge about Ca(2+) channels, including vesicular P2X4 purinoceptors, in type II cells and associated signaling cascades within the alveolar microenvironment, and relates stimulus-dependent activation of these pathways with distinct stages of surfactant secretion, including pre- and postfusion stages of LB exocytosis.
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Affiliation(s)
- Paul Dietl
- Institute of General Physiology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
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Miklavc P, Hecht E, Hobi N, Wittekindt OH, Dietl P, Kranz C, Frick M. Actin coating and compression of fused secretory vesicles are essential for surfactant secretion--a role for Rho, formins and myosin II. J Cell Sci 2012; 125:2765-74. [PMID: 22427691 DOI: 10.1242/jcs.105262] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Secretion of vesicular contents by exocytosis is a fundamental cellular process. Increasing evidence suggests that post-fusion events play an important role in determining the composition and quantity of the secretory output. In particular, regulation of fusion pore dilation and closure is considered a key regulator of the post-fusion phase. However, depending on the nature of the cargo, additional mechanisms might be essential to facilitate effective release. We have recently described that in alveolar type II (ATII) cells, lamellar bodies (LBs), which are secretory vesicles that store lung surfactant, are coated with actin following fusion with the plasma membrane. Surfactant, a lipoprotein complex, does not readily diffuse out of fused LBs following opening and dilation of the fusion pore. Using fluorescence microscopy, atomic force microscopy and biochemical assays, we present evidence that actin coating and subsequent contraction of the actin coat is essential to facilitate surfactant secretion. Latrunculin B prevents actin coating of fused LBs and inhibits surfactant secretion almost completely. Simultaneous imaging of the vesicle membrane and the actin coat revealed that contraction of the actin coat compresses the vesicle following fusion. This leads to active extrusion of vesicle contents. Initial actin coating of fused vesicles is dependent on activation of Rho and formin-dependent actin nucleation. Actin coat contraction is facilitated by myosin II. In summary, our data suggest that fusion pore opening and dilation itself is not sufficient for release of bulky vesicle cargos and that active extrusion mechanisms are required.
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Affiliation(s)
- Pika Miklavc
- Department of General Physiology, University of Ulm, Ulm, Germany
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