We wish to thank Francesca Polverino MD, a Research Fellow at Brigham and Women&#8217;s Hospital for her contribution to this article, and also Monica Yao, BS, and Kate Rydell, BS for their assistance with murine husbandry and exposing the mice to cigarette smoke.&#160;&#160;
This work was supported by Public Health Service, National Heart, Lung, and Blood Institute Grants HL111835, HL105339, HL114501, Flight Attendants Medical Research Institute Grant #CIA123046, the Brigham and Women&#8217;s Hospital-Lovelace Respiratory Research Institute Consortium, and the Cambridge NIHR Biomedical Research Centre.

<ol>
	<li>Murray, C. J., Lopez, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+the+global+burden+of+disease.">Measuring the global burden of disease.</a> N. Engl. J Med. 369, 448-457 (2013).</li><li>Wright, J. L., Cosio, M., Churg, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+chronic+obstructive+pulmonary+disease.">Animal models of chronic obstructive pulmonary disease.</a> Am. J Physiol Lung Cell Mol. Physiol. 295, 1-15 (2008).</li><li>Hautamaki, R. D., Kobayashi, D. K., Senior, R. M., Shapiro, S. 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We have no conflicts of interest to disclose.

Most researcher use mice to model the main chronic lung pathologies and abnormal lung physiology in COPD (airspace enlargement, SAR, and increases in lung compliance) present in the human disease. A comprehensive approach to assess the effect of molecules of interest on both emphysema development and SAR is needed in mice in order to comprehensively assess the activities of molecules of interest in these chronic disease processes. 
There are several critical steps in this protocol. First, dur...

The use of animal models to study COPD is challenging because no model can perfectly replicate all features of the human disease(2). Most investigators use mice to model COPD because of the similarities between mice and humans in their pulmonary physiology, pathology, genetics, and metabolites. Also, mice are relatively inexpensive to study, and both emphysema and small airway remodeling develop within 6 months of CS exposure(5,7-9).
Cigarette smoke-induced COPD: Several methods can induce COPD in mice. Most researchers expose mice to CS, which is the main etiologic factor for human COPD. CS exposure for 6 months causes the development of emphysema and small airway remodeling (SAR) in mice, but the severity of the disease that is induced varies depending on the murine strain studied. For example, NZWLacZ mice are resistant to the development of CS-induced emphysema whereas AKR/J mice are extremely sensitive(10). Most investigators study C57BL/6 strain mice in the CS exposure model as many gene-targeted mice are available in this strain. After 6 months of CS exposure, emphysema and small airway fibrosis develop in wild type (WT) C57BL/6 mice, and both lesions are relatively mild in severity(5,10). Researchers use two types of CS exposure: nose-only and whole-body exposures. The major disadvantages of the nose-only exposure technique are that: 1) it is a more labor-intensive method; and 2) mice have to be restrained in small chambers which can induce a stress response and hyperthermia in the animals(11). The major disadvantage of whole-body exposure (described herein) is that the animals can ingest (as well as inhale) nicotine and tar products when they clean their fur. Mice exposed to whole-body CS also have lower carboxyhemoglobin levels and reduced loss of body weight when compared with animal exposed to nose-only CS(12).
Pulmonary function test (PFTs): Measures of lung compliance and elastance are usually similar in C57BL/6 wild type (WT) mice exposed to air or CS for 6 months due to the relatively mild emphysema that develops when this strain is exposed to CS(10). However, when emphysematous destruction is more severe, increases in lung compliance and left shifts in the pressure-volume (PV) flow loops can be detected. The latter can be observed, for example, in murine strains that are more susceptible to the effects of CS(10), in CS-exposed C57BL/6 strain gene-targeted mice that have a more severe emphysema type than C57BL/6 WT mice(13), or in CS-exposed mice subjected to environmental changes that render them more susceptible to the effects of CS(14). This protocol uses a small animal ventilator to measure reductions in the elastic recoil of the lung (increases in quasistatic lung compliance [Cst] and reductions in tissue elastance [H]), PV flow loops, and changes in airway and tissue resistance in anesthetized mice(15,16).
Measures of pulmonary emphysema: Analysis of emphysema development in CS-exposed C56BL/6 strain mice is challenging because its distribution is spatially heterogeneous. Several different methods quantify airspace enlargement in mice. The first method used was the mean linear intercept (Lm)(17). However, the Lm method is a slow, manual process which may not capture the heterogeneity of the disease (unless all sections of the lung are randomly sampled) and its use may therefore introduce observer bias into the analysis. The destructive index [DI,(18)] also quantifies airspace enlargement using a transparent sheet with 50 equally distributed points placed over a printed digitized image of a hematoxylin and eosin-stained lung section. The PI method scores the area surrounding each point according to the extent to which the alveolar ducts and alveolar walls within this area are destroyed. The main disadvantage of the DI method is that it is time-consuming and not more accurate than other methods(19,20).
This protocol measures mean alveolar chord length and alveolar area on paraffin-embedded lung sections stained with Gill&#8217;s stain. Morphometry software converts images of lung sections to binary images (in which tissue is white and airspace is black), and then superimposes a uniform grid of horizontal and vertical lines (chords) and the software then quantifies the length of each chord within areas identified by software as airspace. Using this method, it is possible to measure the size of the alveoli in all parts of the lung in a standardized and relatively automated manner(21).
Small airway remodeling (SAR): The increased deposition of ECM proteins (especially interstitial collagens) around small airways occurs in CS-exposed animals and contributes to airflow obstruction. Researchers do not study SAR in animal models of COPD as frequently as emphysema development(22). To quantify SAR in CS-exposed mice, this protocol uses image analysis software to measure the thickness of the layer of ECM proteins that is deposited around the small airways (airways having a mean diameter between 300 and 899 m) in paraffin-embedded lung sections stained with Masson&#8217;s trichrome stain.

<table><tbody><tr><td>Whole-body smoke exposure device</td><td>Teague Enterprise</td><td>TE-10z</td><td>Chronic Smoke exposures to induce chronic lung disease in mice</td></tr><tr><td>Research Cigarette</td><td>University of Kentucky</td><td>3R4F reference cigarettes</td><td></td></tr><tr><td>Pallflex&amp;reg; Air Monitoring Filters, Emfab Filters TX40HI20WW, 25 mm</td><td>Pall Corporation</td><td>7219</td><td>For measurement of TPMs</td></tr><tr><td>25 mm filter holder</td><td>Pall Corporation</td><td></td><td></td></tr><tr><td>Filter sampler</td><td>Intermatic</td><td>Metal T100</td><td></td></tr><tr><td>Gas meter</td><td>AEM</td><td>Gas meters G1.6; G2.5; G4</td><td></td></tr><tr><td>Tracheal Cannula for mouse 18 gauge</td><td>Labinvention</td><td></td><td>Analysis of pulmonary function</td></tr><tr><td>Mechanical ventilator</td><td>Scireq</td><td>FlexiVent</td><td></td></tr><tr><td>Gill&#039;s hematoxylin solution&amp;nbsp;</td><td>Sigma-Aldrich</td><td>GSH316</td><td>For Gill staining, work under a fume hood</td></tr><tr><td>Hematoxylin solution, Harris modified</td><td>Sigma-Aldrich</td><td>HHS16</td><td></td></tr><tr><td>Cytoseal-60</td><td>Thermo Scientific</td><td>8310-16</td><td></td></tr><tr><td>Micro-Slide-Field-Finder</td><td>Andwin Scientific INC</td><td>50-949-582</td><td>For analysis of emphysema</td></tr><tr><td>Scion Image Program</td><td>Scion Corporation</td><td></td><td></td></tr><tr><td>Mason&#039;s trichrome stain</td><td>Sigma-Aldrich</td><td>HT15</td><td>For analysis of small airway fibrosis</td></tr><tr><td>MetaMorp Offline version 7.0</td><td>Molecullar Devices LLC</td><td>31032</td><td></td></tr></tbody></table>

automated measurement of pulmonary emphysema and small airway remodeling in cigarette smoke-exposed mice

COPD is projected to be the third most common cause of mortality world-wide by 2020(1). Animal models of COPD are used to identify molecules that contribute to the disease process and to test the efficacy of novel therapies for COPD. Researchers use a number of models of COPD employing different species including rodents, guinea-pigs, rabbits, and dogs(2). However, the most widely-used model is that in which mice are exposed to cigarette smoke. Mice are an especially useful species in which to model COPD because their genome can readily be manipulated to generate animals that are either deficient in, or over-express individual proteins. Studies of gene-targeted mice that have been exposed to cigarette smoke have provided valuable information about the contributions of individual molecules to different lung pathologies in COPD(3-5). Most studies have focused on pathways involved in emphysema development which contributes to the airflow obstruction that is characteristic of COPD. However, small airway fibrosis also contributes significantly to airflow obstruction in human COPD patients(6), but much less is known about the pathogenesis of this lesion in smoke-exposed animals. To address this knowledge gap, this protocol quantifies both emphysema development and small airway fibrosis in smoke-exposed mice. This protocol exposes mice to CS using a whole-body exposure technique, then measures respiratory mechanics in the mice, inflates the lungs of mice to a standard pressure, and fixes the lungs in formalin. The researcher then stains the lung sections with either Gill&#8217;s stain to measure the mean alveolar chord length (as a readout of emphysema severity) or Masson&#8217;s trichrome stain to measure deposition of extracellular matrix (ECM) proteins around small airways (as a readout of small airway fibrosis). Studies of the effects of molecular pathways on both of these lung pathologies will lead to a better understanding of the pathogenesis of COPD.

This protocol begins with whole-body exposure of mice for CS. Adequate oversight and maintenance of the device and monitoring of TPM counts ensure consistent smoke exposures (Figure 1). It is important that the researcher practices the lung inflation technique using the inflation device
This protocol begins with whole-body exposure of mice for CS. Adequate oversight and maintenance of the device and monitoring of TPM counts ensure consistent smoke exposures (Figure 1</...

Watch this Scientific Journal Video about Automated Measurement of Pulmonary Emphysema and Small Airway Remodeling in Cigarette Smoke-exposed Mice at JoVE.com

Automated Measurement of Pulmonary Emphysema and Small Airway Remodeling in Cigarette Smoke-exposed Mice

The goal of this protocol is to provide automated methods to quantify chronic lung pathologies in a murine model of COPD. The protocol includes exposing mice to cigarette smoke (CS), measuring pulmonary function, inflating the lungs, and using morphometry methods to measure emphysema and small airway remodeling in mice.

COPD is projected to be the third most common cause of mortality world-wide by 2020(1).  Animal models of COPD are used to identify molecules that ...

automated-measurement-pulmonary-emphysema-small-airway-remodeling

Research

JoVE Journal

Medicine

13.2K Views.  Brigham and Women's Hospital - Harvard Medical School. The goal of this protocol is to provide automated methods to quantify chronic lung pathologies in a murine model of COPD. The protocol includes exposing mice to cigarette smoke (CS), measuring pulmonary function, inflating the lungs, and using morphometry methods to measure emphysema and small airway remodeling in mice. 

Video: Automated Measurement of Pulmonary Emphysema and Small Airway Remodeling in Cigarette Smoke-exposed Mice

Isolation of Mouse Respiratory Epithelial Cells and Exposure to Experimental Cigarette Smoke at Air Liquid Interface  

Pulmonary epithelial cells can be isolated from the respiratory tract of mice and cultured at air-liquid interface (ALI) as a model of differentiated respiratory epithelium. A protocol is described for isolating and exposing these cells to mainstream cigarette smoke (CS), in order to study epithelial cell responses to CS exposure. The protocol consists of three parts: the isolation of airway epithelial cells from mouse trachea, the culturing of these cells at air-liquid interface (ALI) as fully differentiated epithelial cells, and the delivery of calibrated mainstream CS to these cells in culture. The ALI culture system allows the culture of respiratory epithelia under conditions that more closely resemble their physiological setting than ordinary liquid culture systems. The study of molecular and lung cellular responses to CS exposure is a critical component of understanding the impact of environmental air pollution on human health. Research findings in this area may ultimately contribute towards understanding the etiology of chronic obstructive pulmonary disease (COPD), and other tobacco-related diseases, which represent major global health problems.

Isolation of Mouse Respiratory Epithelial Cells and Exposure to Experimental Cigarette Smoke at Air Liquid Interface

Pulmonary epithelial cells can be isolated from the respiratory tract of mice and cultured at air-liquid interface as a model of differentiated respiratory epithelium. A protocol is described for isolating, culturing and exposing these cells to mainstream cigarette smoke, in order to study molecular responses to this environmental toxin.

Pulmonary epithelial cells can be isolated from the respiratory tract of mice and cultured at air-liquid interface (ALI) as a model of differentiated ...

Murine Model of Allergen Induced Asthma

Asthma is a major cause of morbidity and mortality, affecting some 300 million people throughout the world.1 More than 8% of the US population has asthma, with the prevalence increasing.2 As with other diseases, animal models of allergic airway disease greatly facilitate understanding of the underlying pathophysiology, help identify potential therapeutic targets, and allow preclinical testing of possible new therapies. Models of allergic airway disease have been developed in several animal species, but murine models are particularly attractive due to the low cost, ready availability, and well-characterized immune systems of these animals.3 Availability of a variety of transgenic strains further increases the attractiveness of these models.4 Here we describe two murine models of allergic airway disease, both employing ovalbumin as the antigen. Following initial sensitization by intraperitoneal injection, one model delivers the antigen challenge by nebulization, the other by intratracheal delivery. These two models offer complementary advantages, with each mimicking the major features of human asthma.5
The major features of acute asthma include an exaggerated airway response to stimuli such as methacholine (airway hyperresponsiveness; AHR) and eosinophil-rich airway inflammation. These are also prominent effects of allergen challenge in our murine models,5,6 and we describe techniques for measuring them and thus evaluating the effects of experimental manipulation. Specifically, we describe both invasive7 and non-invasive8 techniques for measuring airway hyperresponsiveness as well as methods for assessing infiltration of inflammatory cells into the airways and the lung. Airway inflammatory cells are collected by bronchoalveolar lavage while lung histopathology is used to assess markers of inflammation throughout the organ. These techniques provide powerful tools for studying asthma in ways that would not be possible in humans.

Experimental mouse models of allergic asthma offer new possibilities for studying disease pathogenesis and developing new therapeutics. These models are well suited to measuring factors governing the allergic immune response, airway inflammation, and pulmonary pathophysiology.

Asthma is a major cause of morbidity and mortality, affecting some 300 million people throughout the world.1 More than 8% of the US population has asthma, ...

Immunology and Infection

A Reversible, Non-invasive Method for Airway Resistance Measurements and Bronchoalveolar Lavage Fluid Sampling in Mice

Airway hyperreactivity (AHR) measurements and bronchoalveolar lavage (BAL) fluid sampling are essential to experimental asthma models, but repeated procedures to obtain such measurements in the same animal are generally not feasible.  Here, we demonstrate protocols for obtaining from mice repeated measurements of AHR and bronchoalveolar lavage fluid samples.  Mice were challenged intranasally seven times over 14 days with a potent allergen or sham treated.  Prior to the initial challenge, and within 24 hours following each intranasal challenge, the same animals were anesthetized, orally intubated and mechanically ventilated.  AHR, assessed by comparing dose response curves of respiratory system resistance (RRS) induced by increasing intravenous doses of acetylcholine (Ach) chloride between sham and allergen-challenged animals, were determined.  Afterwards, and via the same intubation, the left lung was lavaged so that differential enumeration of airway cells could be performed.  These studies reveal that repeated measurements of AHR and BAL fluid collection are possible from the same animals and that maximal airway hyperresponsiveness and airway eosinophilia are achieved within 7-10 days of initiating allergen challenge.  This novel technique significantly reduces the number of mice required for longitudinal experimentation and is applicable to diverse rodent species, disease models and airway physiology instruments.  

Repeated measurements of rodent respiratory physiology and sampling of airway inflammatory cells are desirable, but generally not feasible. Here we describe a repeatable method for orally intubating mice that permits repeated measurements of airway hyperreactivity and sampling of airway inflammatory cells.

Airway hyperreactivity (AHR) measurements and bronchoalveolar lavage (BAL) fluid sampling are essential to experimental asthma models, but repeated ...

Biology

Measurement of the Pressure-volume Curve in Mouse Lungs

In recent decades the mouse has become the primary animal model of a variety of lung diseases. In models of emphysema or fibrosis, the essential phenotypic changes are best assessed by measurement of the changes in lung elasticity. To best understand specific mechanisms underlying such pathologies in mice, it is essential to make functional measurements that can reflect the developing pathology. Although there are many ways to measure elasticity, the classical method is that of the total lung pressure-volume (PV) curve done over the whole range of lung volumes. This measurement has been made on adult lungs from nearly all mammalian species dating back almost 100 years, and such PV curves also played a major role in the discovery and understanding of the function of pulmonary surfactant in fetal lung development. Unfortunately, such total PV curves have not been widely reported in the mouse, despite the fact that they can provide useful information on the macroscopic effects of structural changes in the lung. Although partial PV curves measuring just the changes in lung volume are sometimes reported, without a measure of absolute volume, the nonlinear nature of the total PV curve makes these partial ones very difficult to interpret. In the present study, we describe a standardized way to measure the total PV curve. We have then tested the ability of these curves to detect changes in mouse lung structure in two common lung pathologies, emphysema and fibrosis. Results showed significant changes in several variables consistent with expected structural changes with these pathologies. This measurement of the lung PV curve in mice thus provides a straightforward means to monitor the progression of the pathophysiologic changes over time and the potential effect of therapeutic procedures.

Here we present a protocol to simply and reliably measure the lung pressure-volume curve in mice, showing that it is sufficiently sensitive to detect phenotypic parenchymal changes in two common lung pathologies, pulmonary fibrosis and emphysema. This metric provides a means to quantify the lung&#8217;s structural changes with developing pathology.

In recent decades the mouse has become the primary animal model of a variety of lung diseases. In models of emphysema or fibrosis, the essential ...

Generation of a Chronic Obstructive Pulmonary Disease Model in Mice by Repeated Ozone Exposure

Chronic obstructive pulmonary disease (COPD) is characterized by persistent airflow limitation and lung parenchymal destruction. It has a very high incidence in aging populations. The current conventional therapies for COPD focus mainly on symptom-modifying drugs; thus, the development of new therapies is urgently needed. Qualified animal models of COPD could help to characterize the underlying mechanisms and can be used for new drug screening. Current COPD models, such as lipopolysaccharide (LPS) or the porcine pancreatic elastase (PPE)-induced emphysema model, generate COPD-like lesions in the lungs and airways but do not otherwise resemble the pathogenesis of human COPD. A cigarette smoke (CS)-induced model remains one of the most popular because it not only simulates COPD-like lesions in the respiratory system, but it is also based on one of the main hazardous materials that causes COPD in humans. However, the time-consuming and labor-intensive aspects of the CS-induced model dramatically limit its application in new drug screening. In this study, we successfully generated a new COPD model by exposing mice to high levels of ozone. This model demonstrated the following: 1) decreased forced expiratory volume 25, 50, and 75/forced vital capacity (FEV25/FVC, FEV50/FVC, and FEV75/FVC), indicating the deterioration of lung function; 2) enlarged lung alveoli, with lung parenchymal destruction; 3) reduced fatigue time and distance; and 4) increased inflammation. Taken together, these data demonstrate that the ozone exposure (OE) model is a reliable animal model that is similar to humans because ozone overexposure is one of the etiological factors of COPD. Additionally, it only took 6 - 8 weeks, based on our previous work, to create an OE model, whereas it requires 3 - 12 months to induce the cigarette smoke model, indicating that the OE model might be a good choice for COPD research.

This study describes the successful generation of a new chronic obstructive pulmonary disease (COPD) animal model by repeatedly exposing mice to high concentrations of ozone.

Chronic obstructive pulmonary disease (COPD) is characterized by persistent airflow limitation and lung parenchymal destruction. It has a very high ...

Evaluation of Respiratory System Mechanics in Mice using the Forced Oscillation Technique

The forced oscillation technique (FOT) is a powerful, integrative and translational tool permitting the experimental assessment of lung function in mice in a comprehensive, detailed, precise and reproducible manner. It provides measurements of respiratory system mechanics through the analysis of pressure and volume signals acquired in reaction to predefined, small amplitude, oscillatory airflow waveforms, which are typically applied at the subject's airway opening. The present protocol details the steps required to adequately execute forced oscillation measurements in mice using a computer-controlled piston ventilator (flexiVent; SCIREQ Inc, Montreal, Qc, Canada). The description is divided into four parts: preparatory steps, mechanical ventilation, lung function measurements, and data analysis. It also includes details of how to assess airway responsiveness to inhaled methacholine in anesthetized mice, a common application of this technique which also extends to other outcomes and various lung pathologies. Measurements obtained in na&iuml;ve mice as well as from an oxidative-stress driven model of airway damage are presented to illustrate how this tool can contribute to a better characterization and understanding of studied physiological changes or disease models as well as to applications in new research areas.

The present protocol provides a detailed step-by-step description of the procedures required to execute measurements of respiratory system mechanics as well as the assessment of airway responsiveness to inhaled methacholine in mice using the forced oscillation technique (flexiVent; SCIREQ Inc, Montreal, Qc, Canada).

The  forced oscillation technique (FOT) is a powerful, integrative and translational  tool permitting the experimental assessment of lung function in mice ...

Assessment of Respiratory Function in Conscious Mice by Double-chamber Plethysmography

Air volume changes created by a conscious subject breathing spontaneously within a body box are at the basis of plethysmography, a technique used to non-invasively assess some features of the respiratory function in humans as well as in laboratory animals. The present article focuses on the application of the double-chamber plethysmography (DCP) in small animals. It provides background information on the methodology as well as a detailed step-by-step procedure to successfully assess respiratory function in conscious, spontaneously breathing animals in a non-invasive manner. The DCP can be used to monitor the respiratory function of multiple animals in parallel, as well as to identify changes induced by aerosolized substances over a chosen time period and in a repeated manner. Experiments on control and allergic mice are used herein to demonstrate the utility of the technique, explain the associated outcome parameters, as well as to discuss the related advantages and shortcomings. Overall, the DCP provides valid and theoretically sound readouts that can be trusted to evaluate the respiratory function of conscious small animals both at baseline and after challenges with aerosolized substances.

The objective of the present article is to provide a detailed description of the recommended procedures to evaluate respiratory function in conscious mice by double-chamber plethysmography.

Air volume changes created by a conscious subject breathing spontaneously within a body box are at the basis of plethysmography, a technique used to ...

Cigarette Smoke Exposure in Mice using a Whole-Body Inhalation System

Close to 14% of adults in the United States were reported to smoke cigarettes in 2018. The effects of cigarette smoke (CS) on lungs and cardiovascular diseases have been widely studied, however, the impact of CS in other tissues and organs such as blood and bone marrow remain incompletely defined. Finding the appropriate system to study the effects of CS in rodents can be prohibitively expensive and require the purchase of commercially available systems. Thus, we set out to build an affordable, reliable, and versatile system to study the pathologic effects of CS in mice. This whole-body inhalation exposure system (WBIS) set-up mimics the breathing and puffing of cigarettes by alternating exposure to CS and clean air. Here we show that this do-it-yourself (DIY) system induces airway inflammation and lung emphysema in mice after 4-months of cigarette smoke exposure. The effects of whole-body inhalation (WBI) of CS on hematopoietic stem and progenitor cells (HSPCs) in the bone marrow using this apparatus are also shown.

This protocol demonstrates the study of the pathophysiologic effects of cigarette smoke (CS) with a whole-body inhalation (WBI) exposure system (WBIS) built in-house. This system can expose animals to CS under controlled repeatable conditions for research of CS-mediated effects on lung emphysema and hematopoiesis.

Close to 14% of adults in the United States were reported to smoke cigarettes in 2018. The effects of cigarette smoke (CS) on lungs and cardiovascular ...

Lung Fixation under Constant Pressure for Evaluation of Emphysema in Mice

Emphysema is a significant feature of chronic obstructive pulmonary disease (COPD). Studies involving an emphysematous mouse model require optimal lung fixation to produce reliable histological specimens of the lung. Due to the nature of the lung&rsquo;s structural composition, which consists largely of air and tissue, there is a risk that it collapses or deflates during the fixation process. Various lung fixation methods exist, each of which has its own advantages and disadvantages. The lung fixation method presented here utilizes constant pressure to enable optimal tissue evaluation for studies using an emphysematous mouse lung model. The main advantage is that it can fix many lungs with the same condition at one time. Lung specimens are obtained from chronic cigarette smoke-exposed mice. Lung fixation is performed using specialized equipment that enables the production of constant pressure. This constant pressure maintains the lung in a reasonably inflated state. Thus, this method generates a histological specimen of the lung that is suitable to evaluate cigarette smoke-induced mild emphysema.

Presented here is a useful protocol for lung fixation that creates a stable condition for histological evaluate of lung specimens from a mouse model of emphysema. The main advantage of this model is that it can fix many lungs with the same constant pressure without lung collapse or deflation.

Emphysema is a significant feature of chronic obstructive pulmonary disease (COPD). Studies involving an emphysematous mouse model require optimal lung ...

Using Nicotine in a Silica-Exposed Mouse Model to Promote Lung Epithelial-Mesenchymal Transition

Smoking and exposure to silica are common among occupational workers, and silica is more likely to injure the lungs of smokers than non-smokers. The role of nicotine, the primary addictive ingredient in cigarettes, in silicosis development is unclear. The mouse model employed in this study was simple and easily controlled, and it effectively simulated the effects of chronic nicotine ingestion and repeated exposure to silica on lung fibrosis through epithelial-mesenchymal transition in human beings. In addition, this model can help in the direct study of the effects of nicotine on silicosis while avoiding the effects of other components in cigarette smoke.
After environmental adaptation, mice were injected subcutaneously with 0.25 mg/kg nicotine solution into the loose skin over the neck every morning and evening at 12 h intervals over 40 days. Additionally, crystalline silica powder (1-5 &#181;m) was suspended in normal saline, diluted to a suspension of 20 mg/mL, and dispersed evenly using an ultrasonic water bath. The isoflurane-anesthetized mice inhaled 50 &#181;L of this silica dust suspension through the nose and were awoken via chest massage. Silica exposure was administrated daily on days 5-19.
The double-exposed mouse model was exposed to nicotine and then silica, which matches the exposure history of workers who are exposed to both harmful factors. In addition, nicotine promoted pulmonary fibrosis through epithelial-mesenchymal transformation (EMT) in mice. This animal model can be used to study the effects of multiple factors on the development of silicosis.

This study describes a mouse model to study the synergistic effect of nicotine on the progression of pulmonary fibrosis in experimental silicosis mice. The dual-exposure mouse model simulates the pathological progression in the lung after simultaneous exposure to nicotine and silica. The methods described are simple and highly reproducible.

Smoking and exposure to silica are common among occupational workers, and silica is more likely to injure the lungs of smokers than non-smokers. The role ...

Automated Measurement of Pulmonary Emphysema and Small Airway Remodeling in Cigarette Smoke-exposed Mice

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