The authors would like to express gratitude to Mr. Boyin Qin (Shanghai Public Health Clinical Center) for the technical assistance with the &#181;CT evaluation in this protocol.

NOTE: The OE model has been generated and used in previously reported research30,31,32. All animal experiments were approved by the Institutional Animal Care and Use Committee (IACUC) of Shanghai Jiaotong University.
1. Mice
<ol>
	<li>House pathogen-free, 7- to 9-week-old female BALB/c mice in individual ventilated cages in an animal facility under controlled temperature (20 &#176;C) and humidity (40 - 60%). Provide a 12&#160;h light and 12&#160;h dark cycle in the facility. Provide food and water ad libitum.</li>
</ol>
2. Ozone or Air Exposure
<ol>
	<li>Generate ozone with an electric generator in a sealing acrylic (e.g. Perspex) box. Blow the air out of the box using a small air blower through an air vent pipe that is connected on the inside and outside of the box. Monitor the concentration of ozone in the box using an ozone probe. Wait until the concentration of ozone in the box reaches 2.5 parts per million (ppm). 
	NOTE: The ozone probe can automatically switch the ozone generator on or off and can maintain the ozone level in the box at 2.5 ppm.</li>
	<li>Place the mice into the box when the level of ozone reaches 2.5 ppm. Keep the mice in the box for 3 h each time to expose them to ozone. 
	NOTE: The box can maintain an ozone level of 2.5 ppm during the 3 h by automatically switching the ozone generator on or off and blowing the CO2 that is produced by the mice out of the box.</li>
	<li>Give two ozone exposures (each exposure lasting 3 h) per week (once every 3 days) for 7 weeks; expose the control mice to air at the same time and for the same period.</li>
</ol>
3. Micro-computed Tomography
<ol>
	<li>At the end of week 7, anesthetize the mice with an intraperitoneal injection of pelltobarbitalum natricum (1%, 0.6 - 0.8 ml/100 g)&#160;adjust the dose according to individual situations to see that the mouse does not respond to a toe pinch.&#160;Monitor and keep the mouse at a steady breathing frequency; and make sure no voluntary motions exist during the procedures.</li>
	<li>Place the anesthetized mice in the chamber of a micro-computed tomography (&#181;CT).</li>
	<li>Calibrate the &#181;CT using the standard protocol and the manufacturer&#39;s instructions. Set the X-ray tube at 50 kV and the current at 450 &#181;A. 
	NOTE: Both the X-ray and the detector rotate around the mice.</li>
	<li>Perform the &#181;CT analysis by acquiring 515 projections with an effective pixel size of 0.092 mm, an exposure time of 300 ms for one slice, and a slice thickness of 0.093 mm.</li>
	<li>Reconstruct the lung with the acquired images using a software. Adjust the grayscale image brightness by setting the minimum and maximum of the grayscale at -750 and -550 Hounsfield units, respectively. 
	NOTE: The software will automatically calculate the volumes of the lung parenchyma and the low-attenuation area (LAA)34,35.</li>
	<li>Calculate the percentage of LAA (LAA%) by dividing the LAA volume by the total lung volume.</li>
</ol>
4. Treadmill Test
<ol>
	<li>Give the mice an adaptation test at a speed of 10 m/min for 10 min on a running treadmill machine. &#160;Note: The electricity is always off when the procedure is being conducted.&#160;</li>
	<li>Administer a fatigue test to the mice.
	<ol>
		<li>Warm up the mice at a speed of 10 m/min for 5 min.</li>
		<li>Increase the speed to 15 m/min for 10 min.</li>
		<li>Increase the exercise intensity: increasing the speed by 5 m/min, starting at 20 m/min, every 30 min until mice cannot continue to run36.</li>
	</ol>
	</li>
	<li>Record the total running distance and running time as fatigue distance and fatigue time, respectively.</li>
</ol>
5. Pulmonary Function Measurements
<ol>
	<li>Anesthetize the mice with an intraperitoneal injection of pelltobarbitalum natricum (1%, 0.6 - 0.8 ml/100 g) adjust the dose according to individual situations to see that the mouse does not respond to a toe pinch&#160;and wait until the mice have maintained spontaneous breathing.&#160;Monitor and keep the mouse at a steady breathing frequency; and make sure no voluntary motions exist during the procedures.</li>
	<li>Carefully tracheostomize the mice and place them in a body plethysmograph that is connected to a computer-controlled ventilator. 
	NOTE: Ventilation is controlled via a valve located proximally to the endotracheal tube. The setup provides different semi-automatic maneuvers, including the maneuver of the quasi-static pressure volume and the maneuver of the fast flow volume.</li>
	<li>Impose an average breathing frequency of 150 breaths/min to the anesthetized mouse via pressure-controlled ventilation until a regular breathing pattern and complete expiration at each breathing cycle is obtained.</li>
	<li>Perform the quasi-static pressure-volume maneuver with the device by using the negative pressures generated in the plethysmograph.</li>
	<li>Perform the fast flow volume maneuver within the quasi-static pressure-volume loops to record the FVC and the FEV. Inflate the lung to +30 cm H2O and immediately afterwards connect it to a highly negative pressure to enforce expiration until the residual volume is at -30 cm H2O. Record the FEV in the first 25, 50, and 75 ms of exhalation (FEV25, FEV50, and FEV75, respectively). Reject the suboptimal maneuvers. For each test with every single mouse, conduct a minimum of three acceptable maneuvers to obtain a reliable mean for all numerical parameters.</li>
</ol>
6. BALF Collection
<ol>
	<li>Following terminal anesthesia with pelltobarbitalum natricum ((1%, 1.8-2.4 ml/100 g)&#160;adjust the dose according to individual situations to see that the mouse does not respond to a toe pinch and lose breath),&#160;lavage the mice with 2 mL of PBS via a 1 mm-diameter endotracheal tube and then retrieve the BALF10.</li>
	<li>Pool the retrieved lavage aliquots and centrifuge them at 4 &#176;C and 250 x g for 10 min.</li>
	<li>Collect the supernatant for immediate use and store the remainder at -80 &#176;C or liquid nitrogen.</li>
	<li>Count the total number of cells using a hemocytometer.</li>
	<li>Resuspend the cell pellet in PBS and then spin (1,400 x g, 6 min) 250 &#181;L of resuspended cells onto slides using a slide spinner centrifuge.</li>
	<li>Apply Wright staining to cells on the slides according to the manufacturer&#39;s protocol.</li>
	<li>Count 200 cells per mouse; identify the cells as macrophages or neutrophils, according to standard morphology, under 400X magnification; and count their numbers.</li>
</ol>
7. Cardiac Blood Sampling
<ol>
	<li>Collect blood via cardiac puncture, load it into 1.5-mL tubes, and keep it on ice for 30 min.</li>
	<li>Centrifuge the blood samples for 5 min at 2,000 x g and 4 &#176;C.</li>
	<li>Transfer the supernatant (serum) to a new tube and store it at -80 &#176;C or liquid nitrogen.</li>
	<li>Prepare the serum for IL-1&#946;, IL-10, and TNF-&#945; detection tests using the respective ELISA kits.</li>
</ol>
8. Lung Morphometric Analysis
<ol>
	<li>Dissect the lungs and tracheas from the mice.
	<ol>
		<li>Position each euthanized mouse onto a surgical board immediately after sacrifice.</li>
		<li>Dissect away the platysma and anterior tracheal muscles to visualize and access the tracheal rings.</li>
		<li>Open up the thoracic cavity. Dissect the lungs and the trachea, but do not separate the heart from the lungs.</li>
	</ol>
	</li>
	<li>Connect the endotracheal catheter to a syringe containing 4% paraformaldehyde through a PE90 polyethylene tube. 
	Caution: Paraformaldehyde is toxic. Wear gloves and safety glasses and use the solution inside a fume hood.</li>
	<li>Inflate the lung completely using 4% paraformaldehyde (10 drops, ~200 &#181;L) through the endotracheal catheter. Remove the heart after the completion of inflation.</li>
	<li>Maintain the lung in a 15&#160;mL tube containing 10 mL of 4% paraformaldehyde for at least 4 h.</li>
	<li>Embed the lung in paraffin. Obtain 5-&#181;m sections by paraffin block sectioning with a rotary microtome. During the sectioning, expose the maximum surface area of lung tissue within the bronchial tree area.</li>
	<li>For morphometric analysis, perform hematoxylin and eosin (H&#38;E) staining on the sections.</li>
	<li>Image the sections with a bright-field upright microscope (objective lens, 20X; exposure time, 1.667 ms).</li>
	<li>Have two investigators blinded to the treatment protocol independently count the histological sections. Use the mean linear intercept (Lm) as a parameter for measuring the distance of the inter-alveolar septal wall. Determine the Lm using the following steps:
	<ol>
		<li>Open the images of the sections in Photoshop and draw a reticule-grid on the image with five 550 &#181;m&#160;long lines.</li>
		<li>Count the number of alveoli across the grid line.</li>
		<li>Calculate the Lm by dividing the length of the grid line by the number of alveoli. For quantification, image five sections per mouse. Acquire ten images of each section (one image per field) and assess randomly. During field selection, avoid fields of airways and vessels by moving one field ahead or in another direction. 
		Note: The data are presented as the mean &#177; S.E.M. An un-paired t-test was carried out for comparison between air-exposed mice and ozone-exposed mice. Three animals of each group were used to calculate the significant difference. A p-value of &#60;0.05 was considered significant.</li>
	</ol>
	</li>
</ol>

Z.W.S. and W.W. are current employees and stock option holders of the Cellular Biomedicine Group (NASDAQ: CBMG). The other authors declare that they have no competing interests.

In this study, we present a reliable method for generating a new COPD model. Compared to other models (i.e., LPS or PPE models), this OE model recapitulates the pathological process of COPD patients. Because cigarette smoke is the main hazardous material that causes COPD in human patients40, the CS model remains the most popular COPD model41,42. However, the CS model requires a 3- to 12-month R&#38;D period for new drugs. Compared...

It has been estimated that COPD, including emphysema and chronic bronchitis, might be the third leading cause of death in the world in 20201,2. The potential incidence of COPD in a population over 40 years old is estimated to be 12.7% in males and 8.3% in females within the next 40 years3. No medications are currently available to reverse the progressive deterioration in COPD patients4. Reliable animal models of COPD not only demand the imitation of the disease pathological process but also require a short generation period. Current COPD models, including the LPS or a PPE-induced model, can induce emphysema-like symptoms5,6. A single administration or a week-long challenge of LPS or PPE to mice or rats results in marked neutrophilia in the bronchoalveolar lavage fluid (BALF), increases pro-inflammatory mediators (e.g., TNF-&#945; and IL-1&#946;) in the BALF or serum, produces lung parenchymal destruction-enlarged air spaces, and limits airflow5,6,7,8,9,10. However, LPS or PPE are not causes of human COPD and thus do not mimic the pathological process11. A CS-induced model produced a persistent airflow limitation, lung parenchymal destruction, and reduced functional exercise capacity. However, a traditional CS protocol requires at least 3 months to generate a COPD model12,13,14,15. Thus, it is important to generate a new, more efficient animal model that meets the two requirements.
Recently, in addition to cigarette smoking, air pollution and occupational exposure have become more common causes of COPD16,17,18. Ozone, as one of the major pollutants (though not the major component of air pollution), can directly react with the respiratory tract and damage the lung tissue of both children and young adults19,20,21,22,23,24,25. Ozone, as well as other stimulators including LPS, PPE, and CS, are involved in a serious of biochemical pathways of pulmonary oxidative stress and DNA damage and are linked to the initiation and promotion of COPD26,27. Another factor is that the symptoms of some COPD patients deteriorate after being exposed to ozone, indicating that ozone can disrupt lung function18,28,29. Therefore, we generated a new COPD model by repeatedly exposing mice to high concentrations of ozone for 7 weeks; this resulted in airflow defects and lung parenchymal damage similar to those of previous investigations30,31,32. We extended the OE protocol to female mice in this study and successfully reproduced the emphysema observed in male mice in our previous studies30,31,32. Because COPD mortality has decreased in men but increased in women in many countries33, a COPD model in females is needed to study the mechanisms and to develop therapeutic methods for female COPD patients. The applicability of the OE model to all genders lends further support to its use as a COPD model.

<table><tbody><tr><td>BALB/c mice</td><td>Slac Laboratory Animal,Shanghai, China</td><td>N/A</td><td>7-to-9-week-old female BALB/c mice were used in this study.</td></tr><tr><td>Individual ventilated cages</td><td>Suhang, Shanghai, China</td><td>Model Number: MU64S7</td><td>The cages were used for housing mice in the animal facility.</td></tr><tr><td>Sealing perspex-box</td><td>Suhang, Shanghai, China</td><td>N/A</td><td>The box was used&amp;nbsp; to contain the ozone generator. Mice were exposed to ozone within the box.</td></tr><tr><td>Electric generator</td><td>Sander Ozoniser, Uetze-Eltze, Germany</td><td>Model 500&amp;nbsp;</td><td>The device was used for generating ozone.</td></tr><tr><td>Ozone probe</td><td>ATi Technologies, Ashton-U-Lyne, Greater Manchester, UK</td><td>Ozone 300</td><td>The device was used for monitoring and controlling the generation of ozone.</td></tr><tr><td>Pelltobarbitalum natricum</td><td>Sigma, St. Louis, MO, USA</td><td>P3761</td><td>Mice were anesthetized by intraperitoneal injection of pelltobarbitalum natricum.</td></tr><tr><td>Micro-Computed Tomography</td><td>GE Healthcare, London, ON, Canada</td><td>RS0800639-0075</td><td>This device was used for acquiring images of the lung.</td></tr><tr><td>Micro-view 2.01 ABA software</td><td>GE Healthcare, London, ON, Canada</td><td>Micro-view 2.01&amp;nbsp;</td><td>This device was used for reconstruct the lung and analyze volume, LAA of the lung.</td></tr><tr><td>Treadmill machine&amp;nbsp;</td><td>Duanshi, Hangzhou, Zhejiang, China</td><td>DSPT-208</td><td>This machine was usd for fatigue test.</td></tr><tr><td>Body plethysmograph</td><td>eSpira&amp;trade; Forced Manoeuvres System, EMMS, Edinburgh, UK</td><td>Forced Manoeuvres System</td><td>This device was used to test spirometry pulmonary function.</td></tr><tr><td>Ventilator</td><td>eSpira&amp;trade; Forced Manoeuvres System, EMMS, Edinburgh, UK</td><td>Forced Manoeuvres System</td><td>This device was used to test spirometry pulmonary function.</td></tr><tr><td>Slide spinner centrifuge</td><td>Denville Scientific, Holliston, MA, USA</td><td>C1183&amp;nbsp;</td><td>It was used to spin BALF cells onto slides.</td></tr><tr><td>Wright Staining</td><td>Hanhong, Shanghai, China</td><td>RE04000054</td><td>&amp;nbsp;It was used to staining macrophages, neutrophils in the suspended BALF.</td></tr><tr><td>Hemocytometer</td><td>Hausser Scientific, Horsham, PA, USA</td><td>4000</td><td>It was used to count cells.</td></tr><tr><td>IL-1&amp;beta;</td><td>Abcam, Cambridge, MA, USA</td><td>ab100704</td><td>They were used to test the respective factors in serum.</td></tr><tr><td>IL-10</td><td>Abcam, Cambridge, MA, USA</td><td>ab46103</td><td>They were used to test the respective factors in serum.</td></tr><tr><td>TNF-&amp;alpha;</td><td>Abcam, Cambridge, MA, USA</td><td>ab100747</td><td>They were used to test the respective factors in serum.</td></tr><tr><td>Paraformaldehyde&amp;nbsp;</td><td>Sigma, St. Louis, MO, USA</td><td>P6148</td><td>The lung was inflated by 4% paraformaldehyde.</td></tr><tr><td>Paraffin</td><td>Hualing, Shanghai, China</td><td>56#</td><td>It was used to embed the lung.</td></tr><tr><td>Rotary Microtome</td><td>Leica, Wetzlar,&amp;nbsp; Hesse, Germany</td><td>RM2255</td><td>It was used for sectioning the lung.</td></tr><tr><td>Hgaematoxylin and Eosin (H&amp;amp;E) staining solution</td><td>Solarbio, Beijing, China</td><td>G1120</td><td>H&amp;amp;E staining was done for morphometric analysis.</td></tr><tr><td>Upright bright field microscope</td><td>Olympus, Center Valley, PA, USA</td><td>CX41</td><td>It was used to image the H&amp;amp;E staining slides.</td></tr><tr><td>Adobe Photoshop 12</td><td>Adobe, San Jose, CA, USA</td><td>Adobe Photoshop 12</td><td>It was used to count the number of alveoli on the H&amp;amp;E stained images.</td></tr><tr><td>GraphPad prism 5</td><td>Graphpad Software Inc., San Diego, CA</td><td>GraphPad prism 5</td><td>It was used for data analysis and production of figures.</td></tr></tbody></table>

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.

Examples of 3D &#181;CT images of each group are displayed in Figure 1a. The ozone-exposed mice had a significantly larger total lung volume (Figure 1a and b) and LAA% (Figure 1c) than did the air-exposed control mice. The lung volume and LAA% remained elevated after six weeks of ozone exposure31,3...

Watch this Scientific Journal Video about Generation of a Chronic Obstructive Pulmonary Disease Model in Mice by Repeated Ozone Exposure at JoVE.com

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

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 ...

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Research

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Medicine

10.9K Views.  Cellular Biomedicine Group, Shanghai. 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.

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

Long Term Chronic Pseudomonas aeruginosa Airway Infection in Mice

A mouse model of chronic airway infection is a key asset in cystic fibrosis (CF) research, although there are a number of concerns regarding the model itself. Early phases of inflammation and infection have been widely studied by using the Pseudomonas aeruginosa agar-beads mouse model, while only few reports have focused on the long-term chronic infection in vivo. The main challenge for long term chronic infection remains the low bacterial burden by P. aeruginosa and the low percentage of infected mice weeks after challenge, indicating that bacterial cells are progressively cleared by the host.
This paper presents a method for obtaining efficient long-term chronic infection in mice. This method is based on the embedding of the P. aeruginosa clinical strains in the agar-beads in vitro, followed by intratracheal instillation in C57Bl/6NCrl mice. Bilateral lung infection is associated with several measurable read-outs including weight loss, mortality, chronic infection, and inflammatory response. The P. aeruginosa RP73 clinical strain was preferred over the PAO1 reference laboratory strain since it resulted in a comparatively lower mortality, more severe lesions, and higher chronic infection. P. aeruginosa colonization may persist in the lung for over three months. Murine lung pathology resembles that of CF patients with advanced chronic pulmonary disease.
This murine model most closely mimics the course of the human disease and can be used both for studies on the pathogenesis and for the evaluation of novel therapies.

Long Term Chronic Pseudomonas aeruginosa Airway Infection in Mice

We describe the agar-beads method to establish persistent long-term chronic Pseudomonas aeruginosa airway infection in the mouse model.

A mouse model of chronic airway infection is a key asset in cystic fibrosis (CF) research, although there are a number of concerns regarding the model ...

Immunology and Infection

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.

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 ...

Lung microRNA Profiling Across the Estrous Cycle in Ozone-exposed Mice

MicroRNA (miRNA) profiling has become of interest to researchers working in various research areas of biology and medicine. Current studies show a promising future of using miRNAs in the diagnosis and care of lung diseases. Here, we define a protocol for miRNA profiling to measure the relative abundance of a group of miRNAs predicted to regulate inflammatory genes in the lung tissue from of an ozone-induced airway inflammation mouse model. Because it has been shown that circulating sex hormone levels can affect the regulation of lung innate immunity in females, the purpose of this method is to describe an inflammatory miRNA profiling protocol in female mice, taking into consideration the estrous cycle stage of each animal at the time of ozone exposure. We also address applicable bioinformatics approaches to miRNA discovery and target identification methods using limma, an R/Bioconductor software, and functional analysis software to understand the biological context and pathways associated with differential miRNA expression.

Here we describe a method to assess lung expression of miRNAs that are predicted to regulate inflammatory genes using mice exposed to ozone or filtered air at different stages of the estrous cycle.

MicroRNA (miRNA) profiling has become of interest to researchers working in various research areas of biology and medicine. Current studies show a ...

In Vivo Assessment of Alveolar Macrophage Efferocytosis Following Ozone Exposure

Ozone (O3) is a criteria air pollutant that exacerbates and increases the incidence of chronic pulmonary diseases. O3 exposure is known to induce pulmonary inflammation, but little is known regarding how exposure alters processes important to the resolution of inflammation. Efferocytosis is a resolution process, whereby macrophages phagocytize apoptotic cells. The purpose of this protocol is to measure alveolar macrophage efferocytosis following O3-induced lung injury and inflammation. Several methods have been described for measuring efferocytosis; however, most require ex vivo manipulations. Described in detail here is a protocol to measure in vivo alveolar macrophage efferocytosis 24 h after O3 exposure, which avoids ex vivo manipulation of macrophages and serves as a simple technique that can be used to accurately represent perturbations in this resolution process. The protocol is a technically non-intensive and relatively inexpensive method that involves whole-body O3 inhalation followed by oropharyngeal aspiration of apoptotic cells (i.e., Jurkat T cells) while under general anesthesia. Alveolar macrophage efferocytosis is then measured by light microscopy evaluation of macrophages collected from bronchoalveolar (BAL) lavage. Efferocytosis is finally measured by calculating an efferocytic index. Collectively, the outlined methods quantify efferocytic activity in the lung in vivo while also serving to analyze the negative health effects of O3 or other inhaled insults.

This manuscript describes a protocol for determining whether exposure to ozone, a criteria air pollutant, impairs alveolar macrophage efferocytosis in vivo. This protocol utilizes commonly used reagents and techniques and can be adapted to multiple models of pulmonary injury to determine effects on alveolar macrophage efferocytosis.

Ozone (O3) is a criteria air pollutant that exacerbates and increases the incidence of chronic pulmonary diseases. O3 exposure is known to induce ...

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 ...

Biology

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 ...

Visualizing Lung Cellular Adaptations during Combined Ozone and LPS Induced Murine Acute Lung Injury

Lungs are continually faced with direct and indirect insults in the form of sterile (particles or reactive toxins) and infectious (bacterial, viral or fungal) inflammatory conditions. An overwhelming host response may result in compromised respiration and acute lung injury, which is characterized by lung neutrophil recruitment as a result of the patho-logical host immune, coagulative and tissue remodeling response. Sensitive microscopic methods to visualize and quantify murine lung cellular adaptations, in response to low-dose (0.05 ppm) ozone, a potent environmental pollutant in combination with bacterial lipopolysaccharide, a TLR4 agonist, are crucial in order to understand the host inflammatory and repair mechanisms. We describe a comprehensive fluorescent microscopic analysis of various lung and systemic body compartments, namely the broncho-alveolar lavage fluid, lung vascular perfusate, left lung cryosections, and sternal bone marrow perfusate. We show damage of alveolar macrophages, neutrophils, lung parenchymal tissue, as well as bone marrow cells in correlation with a delayed (up to 36-72 h) immune response that is marked by discrete chemokine gradients in the analyzed compartments. In addition, we present lung extracellular matrix and cellular cytoskeletal interactions (actin, tubulin), mitochondrial and reactive oxygen species, anti-coagulative plasminogen, its anti-angiogenic peptide fragment angiostatin, the mitochondrial ATP synthase complex V subunits, &#945; and &#946;. These surrogate markers, when supplemented with adequate in vitro cell-based assays and in vivo animal imaging techniques such as intravital microscopy, can provide vital information towards understanding the lung response to novel immunomodulatory agents.

Combined ozone and bacterial endotoxin exposed mice show wide-spread cell death, including that of neutrophils. We observed cellular adaptations such as disruption of cytoskeletal lamellipodia, increased cellular expression of complex V ATP synthase subunit &#946; and angiostatin in broncho-alveolar lavage, suppression of the lung immune response and delayed neutrophil recruitment.

Lungs are continually faced with direct and indirect insults in the form of sterile (particles or reactive toxins) and infectious (bacterial, viral or ...

Oxygen-Induced Retinopathy Model for Ischemic Retinal Diseases in Rodents

One of the commonly used models for ischemic retinopathies is the oxygen-induced retinopathy (OIR) model. Here we describe detailed protocols for the OIR model induction and its readouts in both mice and rats. Retinal neovascularization is induced in OIR by exposing rodent pups either to hyperoxia (mice) or alternating levels of hyperoxia and hypoxia (rats). The primary readouts of these models are the size of neovascular (NV) and avascular (AVA) areas in the retina. This preclinical in vivo model can be used to evaluate the efficacy of potential anti-angiogenic drugs or to address the role of specific genes in the retinal angiogenesis by using genetically manipulated animals. The model has some strain and vendor specific variation in the OIR induction which should be taken into consideration when designing the experiments.

Oxygen-induced retinopathy (OIR) can be used to model ischemic retinal diseases such as retinopathy of prematurity and proliferative diabetic retinopathy and to serve as a model for proof-of-concept studies in evaluating antiangiogenic drugs for neovascular diseases. OIR induces robust and reproducible neovascularization in the retina that can be quantified.

One of the commonly used models for ischemic retinopathies is the oxygen-induced retinopathy (OIR) model. Here we describe detailed protocols for the OIR ...

A Silicosis Mouse Model Established by Repeated Inhalation of Crystalline Silica Dust

Silicosis can be caused by exposure to respiratory crystalline silica dust (CSD) in an industrial environment. The pathophysiology, screening, and treatment of silicosis in humans have all been extensively studied using the mouse silicosis model. By repeatedly making mice inhale CSD into their lungs, the mice can mimic the clinical symptoms of human silicosis. This methodology is practical and efficient in terms of time and output and does not cause mechanical injury to the upper respiratory tract due to surgery. Furthermore, this model can successfully mimic acute/chronic transformation process of silicosis. The main procedures were as follows. The sterilized 1-5 &#181;m CSD powder was fully ground, suspended in saline, and dispersed in an ultrasonic water bath for 30 min. Mice under isoflurane-induced anesthesia switched from shallow rapid breathing to deep, slow aspiration for approximately 2 s. The mouse was placed in the palm of a hand, and the thumb tip gently touched the lip edge of the mouse's jaw to straighten the airway. After each exhalation, the mice breathed in the silica suspension drop by drop through one nostril, completing the process within 4-8 s. After the mice's breathing had stabilized, their chest was stroked and caressed to prevent the inhaled CSD from being coughed up. The mice were then returned to the cage. In conclusion, this model can quantify CSD along the typical physiological passage of tiny particles into the lung, from the upper respiratory tract to the terminal bronchioles and alveoli. It can also replicate the recurrent exposure of employees due to work. The model can be performed by one person and does not need expensive equipment. It conveniently and effectively simulates the disease features of human silicosis with high repeatability.

This protocol describes a method for establishing a mouse model of silicosis through repeated exposure to silica suspensions via a nasal drip. This model can efficiently, conveniently, and flexibly mimic the pathological process of human silicosis with high repeatability and economy.

Silicosis can be caused by exposure to respiratory crystalline silica dust (CSD) in an industrial environment. The pathophysiology, screening, and ...

A Mouse Model of Pulmonary Fibrosis Induced by Nasal Bleomycin Nebulization

Pulmonary fibrosis is characteristic of several human lung diseases that arise from various causes. Given that treatment options are fairly limited, mouse models continue to be an important tool for developing new anti-fibrotic strategies. In this study, intrapulmonary administration of bleomycin (BLM) is carried out by nasal nebulization to create a mouse model of pulmonary fibrosis that closely mimics clinical disease characteristics. C57BL/6 mice received BLM (7 U/mL, 30 min/day) by nasal nebulization for 3 consecutive days and were sacrificed on day 9, 16, or 23 to observe inflammatory and fibrotic changes in lung tissue. Nasal aerosolized BLM directly targeted the lungs, resulting in widespread and uniform lung inflammation and fibrosis. Thus, we successfully generated an experimental mouse model of typical human pulmonary fibrosis. This method could easily be used to study the effects of the administration of various nasal aerosols on lung pathophysiology and validate new anti-inflammatory and anti-fibrotic treatments.

Various animal models of pulmonary fibrosis have been established using bleomycin to clarify the pathogenesis of pulmonary fibrosis and find new drug targets. However, most pulmonary fibrosis models targeting lung tissue have uneven drug administration. Here, we propose a model of uniform pulmonary fibrosis induced by nasal bleomycin nebulization.

Pulmonary fibrosis is characteristic of several human lung diseases that arise from various causes. Given that treatment options are fairly limited, mouse ...

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

Summary

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Oxygen-Induced Retinopathy Model for Ischemic Retinal Diseases in Rodents

A Silicosis Mouse Model Established by Repeated Inhalation of Crystalline Silica Dust

A Mouse Model of Pulmonary Fibrosis Induced by Nasal Bleomycin Nebulization