Animal models of fibrotic lung disease.
01 Aug 2013-American Journal of Respiratory Cell and Molecular Biology (American Thoracic Society)-Vol. 49, Iss: 2, pp 167-179
TL;DR: Each of the models reviewed in this report offers a powerful tool for studying some aspect of fibrotic lung disease and has a much better understanding of the fact that the aged lung has increased susceptibility to fibrosis.
Abstract: Interstitial lung fibrosis can develop as a consequence of occupational or medical exposure, as a result of genetic defects, and after trauma or acute lung injury leading to fibroproliferative acute respiratory distress syndrome, or it can develop in an idiopathic manner. The pathogenesis of each form of lung fibrosis remains poorly understood. They each result in a progressive loss of lung function with increasing dyspnea, and most forms ultimately result in mortality. To better understand the pathogenesis of lung fibrotic disorders, multiple animal models have been developed. This review summarizes the common and emerging models of lung fibrosis to highlight their usefulness in understanding the cell–cell and soluble mediator interactions that drive fibrotic responses. Recent advances have allowed for the development of models to study targeted injuries of Type II alveolar epithelial cells, fibroblastic autonomous effects, and targeted genetic defects. Repetitive dosing in some models has more closely mimicked the pathology of human fibrotic lung disease. We also have a much better understanding of the fact that the aged lung has increased susceptibility to fibrosis. Each of the models reviewed in this report offers a powerful tool for studying some aspect of fibrotic lung disease.
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TL;DR: It is reported that a remarkable shift in epithelial cell phenotypes occurs in the peripheral lung in PF and several previously unrecognized epithelialcell phenotypes are identified, including a KRT5−/KRT17+ pathologic, ECM-producing epithel cell population that was highly enriched in PF lungs.
Abstract: Pulmonary fibrosis (PF) is a form of chronic lung disease characterized by pathologic epithelial remodeling and accumulation of extracellular matrix (ECM). To comprehensively define the cell types, mechanisms, and mediators driving fibrotic remodeling in lungs with PF, we performed single-cell RNA sequencing of single-cell suspensions from 10 nonfibrotic control and 20 PF lungs. Analysis of 114,396 cells identified 31 distinct cell subsets/states. We report that a remarkable shift in epithelial cell phenotypes occurs in the peripheral lung in PF and identify several previously unrecognized epithelial cell phenotypes, including a KRT5−/KRT17+ pathologic, ECM-producing epithelial cell population that was highly enriched in PF lungs. Multiple fibroblast subtypes were observed to contribute to ECM expansion in a spatially discrete manner. Together, these data provide high-resolution insights into the complexity and plasticity of the distal lung epithelium in human disease and indicate a diversity of epithelial and mesenchymal cells contribute to pathologic lung fibrosis.
453 citations
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TL;DR: This review summarises the available data about the structure and function of the pulmonary ECM, and highlights changes that occur in idiopathic pulmonary fibrosis (IPF), pulmonary arterial hypertension (PAH), chronic obstructive pulmonary disease (COPD), asthma and lung cancer.
Abstract: The pulmonary extracellular matrix (ECM) determines the tissue architecture of the lung, and provides mechanical stability and elastic recoil, which are essential for physiological lung function. Biochemical and biomechanical signals initiated by the ECM direct cellular function and differentiation, and thus play a decisive role in lung development, tissue remodelling processes and maintenance of adult homeostasis. Recent proteomic studies have demonstrated that at least 150 different ECM proteins, glycosaminoglycans and modifying enzymes are expressed in the lung, and these assemble into intricate composite biomaterials. These highly insoluble assemblies of interacting ECM proteins and their glycan modifications can act as a solid phase-binding interface for hundreds of secreted proteins, which creates an information-rich signalling template for cell function and differentiation. Dynamic changes within the ECM that occur upon injury or with ageing are associated with several chronic lung diseases. In this review, we summarise the available data about the structure and function of the pulmonary ECM, and highlight changes that occur in idiopathic pulmonary fibrosis (IPF), pulmonary arterial hypertension (PAH), chronic obstructive pulmonary disease (COPD), asthma and lung cancer. We discuss potential mechanisms of ECM remodelling and modification, which we believe are relevant for future diagnosis and treatment of chronic lung disease.
300 citations
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TL;DR: Targeting myofibroblast apoptosis and reprogramming these cells to become scar-resolving cells are emerging as novel therapeutic strategies to reverse established fibrosis.
Abstract: Organ fibrosis is a lethal outcome of autoimmune rheumatic diseases such as systemic sclerosis. Myofibroblasts are scar-forming cells that are ultimately responsible for the excessive synthesis, deposition and remodelling of extracellular matrix proteins in fibrosis. Advances have been made in our understanding of the mechanisms that keep myofibroblasts in an activated state and control myofibroblast functions. However, the mechanisms that help myofibroblasts to persist in fibrotic tissues remain poorly understood. Myofibroblasts evade apoptosis by activating molecular mechanisms in response to pro-survival biomechanical and growth factor signals from the fibrotic microenvironment, which can ultimately lead to the acquisition of a senescent phenotype. Growing evidence suggests that myofibroblasts and senescent myofibroblasts, rather than being resistant to apoptosis, are actually primed for apoptosis owing to concomitant activation of cell death signalling pathways; these cells are poised to apoptose when survival pathways are inhibited. This knowledge of apoptotic priming has paved the way for new therapies that trigger apoptosis in myofibroblasts by blocking pro-survival mechanisms, target senescent myofibroblast for apoptosis or promote the reprogramming of myofibroblasts into scar-resolving cells. These novel strategies are not only poised to prevent progressive tissue scarring, but also have the potential to reverse established fibrosis and to regenerate chronically injured tissues.
259 citations
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TL;DR: The consensus view is that use of the murine intratracheal bleomycin model in animals of both genders, using hydroxyproline measurements for collagen accumulation along with histologic assessments, is the best‐characterized animal model available for preclinical testing.
Abstract: Numerous compounds have shown efficacy in limiting development of pulmonary fibrosis using animal models, yet few of these compounds have replicated these beneficial effects in clinical trials. Given the challenges associated with performing clinical trials in patients with idiopathic pulmonary fibrosis (IPF), it is imperative that preclinical data packages be robust in their analyses and interpretations to have the best chance of selecting promising drug candidates to advance to clinical trials. The American Thoracic Society has convened a group of experts in lung fibrosis to discuss and formalize recommendations for preclinical assessment of antifibrotic compounds. The panel considered three major themes (choice of animal, practical considerations of fibrosis modeling, and fibrotic endpoints for evaluation). Recognizing the need for practical considerations, we have taken a pragmatic approach. The consensus view is that use of the murine intratracheal bleomycin model in animals of both genders, using hydroxyproline measurements for collagen accumulation along with histologic assessments, is the best-characterized animal model available for preclinical testing. Testing of antifibrotic compounds in this model is recommended to occur after the acute inflammatory phase has subsided (generally after Day 7). Robust analyses may also include confirmatory studies in human IPF specimens and validation of results in a second system using in vivo or in vitro approaches. The panel also strongly encourages the publication of negative results to inform the lung fibrosis community. These recommendations are for preclinical therapeutic evaluation only and are not intended to dissuade development of emerging technologies to better understand IPF pathogenesis.
221 citations
Cites background from "Animal models of fibrotic lung dise..."
...Animal models don’t fully recapitulate physiologic findings of IPF (1, 2) or histopathologic pattern of usual interstitial pneumonia....
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...Route of Delivery in Lung Fibrosis Models When considering bleomycin, most investigators use a single intratracheal administration (1), but repeated intratracheal (44) or repeated intraperitoneal (45) administrations may offer more robust and nonresolving fibrotic pathology....
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TL;DR: The present knowledge and gaps in the understanding of how matrix degradation is regulated and how myofibroblast cell fates can be manipulated are discussed, areas that may identify potential therapeutic approaches for fibrosis.
Abstract: Fibrosis is the excessive accumulation of extracellular matrix that often occurs as a wound healing response to repeated or chronic tissue injury, and may lead to the disruption of organ architecture and loss of function. Although fibrosis was previously thought to be irreversible, recent evidence indicates that certain circumstances permit the resolution of fibrosis when the underlying causes of injury are eradicated. The mechanism of fibrosis resolution encompasses degradation of the fibrotic extracellular matrix as well as elimination of fibrogenic myofibroblasts through their adaptation of various cell fates, including apoptosis, senescence, dedifferentiation, and reprogramming. In this Review, we discuss the present knowledge and gaps in our understanding of how matrix degradation is regulated and how myofibroblast cell fates can be manipulated, areas that may identify potential therapeutic approaches for fibrosis.
219 citations
References
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TL;DR: In patients with acute lung injury and the acute respiratory distress syndrome, mechanical ventilation with a lower tidal volume than is traditionally used results in decreased mortality and increases the number of days without ventilator use.
Abstract: Background Traditional approaches to mechanical ventilation use tidal volumes of 10 to 15 ml per kilogram of body weight and may cause stretch-induced lung injury in patients with acute lung injury and the acute respiratory distress syndrome. We therefore conducted a trial to determine whether ventilation with lower tidal volumes would improve the clinical outcomes in these patients. Methods Patients with acute lung injury and the acute respiratory distress syndrome were enrolled in a multicenter, randomized trial. The trial compared traditional ventilation treatment, which involved an initial tidal volume of 12 ml per kilogram of predicted body weight and an airway pressure measured after a 0.5-second pause at the end of inspiration (plateau pressure) of 50 cm of water or less, with ventilation with a lower tidal volume, which involved an initial tidal volume of 6 ml per kilogram of predicted body weight and a plateau pressure of 30 cm of water or less. The primary outcomes were death before a patient was discharged home and was breathing without assistance and the number of days without ventilator use from day 1 to day 28. Results The trial was stopped after the enrollment of 861 patients because mortality was lower in the group treated with lower tidal volumes than in the group treated with traditional tidal volumes (31.0 percent vs. 39.8 percent, P=0.007), and the number of days without ventilator use during the first 28 days after randomization was greater in this group (mean [+/-SD], 12+/-11 vs. 10+/-11; P=0.007). The mean tidal volumes on days 1 to 3 were 6.2+/-0.8 and 11.8+/-0.8 ml per kilogram of predicted body weight (P Conclusions In patients with acute lung injury and the acute respiratory distress syndrome, mechanical ventilation with a lower tidal volume than is traditionally used results in decreased mortality and increases the number of days without ventilator use.
11,028 citations
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TL;DR: The Diagnostic Process Is Dynamic Clinical Evaluation Radiological Evaluation Role of Surgical Lung Biopsy Unclassifiable Interstitial Pneumonia Bronchoalveolar Lavage Fluid Evaluation Idiopathic Pulmonary Fibrosis.
Abstract: Executive Summary Objectives Participants Evidence Validation Key Messages Introduction Rationale for a Change in the Approach to Classification of Idiopathic Interstitial Pneumonias Development of a New Classification of Idiopathic Interstitial Pneumonia Current Classification of IIP New ATS/ERS Classification Principles Guiding the Assessment of Patients with Idiopathic Interstitial Pneumonias The Diagnostic Process Is Dynamic Clinical Evaluation Radiological Evaluation Role of Surgical Lung Biopsy Unclassifiable Interstitial Pneumonia Bronchoalveolar Lavage Fluid Evaluation Idiopathic Pulmonary Fibrosis Clinical Features Radiologic Features Histologic Features IPF: Areas of Uncertainty Nonspecific Interstitial Pneumonia Clinical Features Radiologic Features Histologic Features NSIP: Areas of Uncertainty Cryptogenic Organizing Pneumonia Clinical Features Radiologic Features Histologic Features COP: Areas of Uncertainty Acute Interstitial Pneumonia Clinical Features Radiologic Features Histologic Features AIP: Areas of Uncertainty Respiratory Bronchiolitis-Associated Interstitial Lung Disease Clinical Features Radiologic Features Histologic Features RB-ILD: Areas of Uncertainty Desquamative Interstitial Pneumonia Clinical Features Radiologic Features Histologic Features DIP: Areas of Uncertainty Lymphoid Interstitial Pneumonia Clinical Features Radiologic Features Histologic Features LIP: Areas of Uncertainty References Appendix
3,591 citations
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TL;DR: Many acute and chronic lung disorders with variable degrees of pulmonary inflammation and fibrosis are collectively referred to as interstitial lung diseases (ILDs) or diffuse parenchymal lung diseases.
Abstract: Many acute and chronic lung disorders with variable degrees of pulmonary inflammation and fibrosis are collectively referred to as interstitial lung diseases (ILDs) or diffuse parenchymal lung diseases. Idiopathic pulmonary fibrosis (or cryptogenic fibrosing alveolitis) (IPF or CFA) is one of several idiopathic interstitial pneumonias. IPF is now recognized as a distinct clinical disorder. Despite major accomplishments in our understanding of the pathogenesis of lung fibrosis (l), the diagnosis and management of patients with IPF continues to pose significant challenges (24).
2,482 citations
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TL;DR: This Review discusses the development of these new generations of humanized mice, how they will facilitate translational research in several biomedical disciplines and approaches to overcome the remaining limitations of these models.
Abstract: The culmination of decades of research on humanized mice is leading to advances in our understanding of human haematopoiesis, innate and adaptive immunity, autoimmunity, infectious diseases, cancer biology and regenerative medicine. In this Review, we discuss the development of these new generations of humanized mice, how they will facilitate translational research in several biomedical disciplines and approaches to overcome the remaining limitations of these models.
1,262 citations
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TL;DR: In this paper, the authors found that mutations in the genes encoding telomerase components can appear as familial idiopathic pulmonary fibrosis, which is a rare hereditary disorder associated with premature death from aplastic anemia and lung fibrosis.
Abstract: BACKGROUND Idiopathic pulmonary fibrosis is progressive and often fatal; causes of familial clustering of the disease are unknown. Germ-line mutations in the genes hTERT and hTR, encoding telomerase reverse transcriptase and telomerase RNA, respectively, cause autosomal dominant dyskeratosis congenita, a rare hereditary disorder associated with premature death from aplastic anemia and pulmonary fibrosis. METHODS To test the hypothesis that familial idiopathic pulmonary fibrosis may be caused by short telomeres, we screened 73 probands from the Vanderbilt Familial Pulmonary Fibrosis Registry for mutations in hTERT and hTR. RESULTS Six probands (8%) had heterozygous mutations in hTERT or hTR; mutant telomerase resulted in short telomeres. Asymptomatic subjects with mutant telomerase also had short telomeres, suggesting that they may be at risk for the disease. We did not identify any of the classic features of dyskeratosis congenita in five of the six families. CONCLUSIONS Mutations in the genes encoding telomerase components can appear as familial idiopathic pulmonary fibrosis. Our findings support the idea that pathways leading to telomere shortening are involved in the pathogenesis of this disease.
1,192 citations