This work was supported by National Institutes of Health grants HL105947-01 (YL), HL07829-16 (AM), HL090152 (AM).

The animal experiments were approved by the Animal Care Committee and Institutional Biosafety Committees of the University of Illinois at Chicago.
NOTE: All procedures involving pseudomonas should be performed with Biosafety Level 2 (BSL2) practices, which include but are not limited to: mask, eye protection, gown or jumpsuit, and double gloves. Work in certified Biosafety Cabinet. Treat instruments in contact with bacteria with bleach or chlorine dioxide based disinfectant. Use a sealed box for transport samples.
1. P. aeruginosa Culture and Growth
<ol>
	<li>Store P. aeruginosa PA103 as a bacterial stock in a screw cap cryovial at -80 &#176;C.</li>
	<li>Place the vial in a rack in a box with 70% ethanol wetted paper towels and take to the Biosafety Level 2 (BSL2) laboratory.</li>
	<li>Streak the bacteria onto sheep blood agar plates and grow at 37 &#176;C for ~15 hr in an incubator.</li>
	<li>In a BSL2 hood, scratch the bacteria from plate with bacteria loop and resuspend in 5 ml PBS.</li>
	<li>Store the stock at 4 &#176;C for up to 3 months. However, determine the titer every 2 weeks.</li>
	<li>Serially dilute the bacteria in PBS (usually from 1:104 to 1:107) and plate out the known dilution on sheep blood agar plates.</li>
	<li>Incubate the plates for ~15 hr. Count colonies and calculate Colony Forming Unit (CFU) to determine bacteria concentration.</li>
	<li>Resuspend the appropriate concentrations (~5 x 103 CFU/&#181;l) in 0.5 ml PBS in 1.5 ml sterile screw cap cryovials. Seal the cryovials and place them in a cryovial rack on disinfectant laden paper towels in a snap lid box.</li>
	<li>Transport the box to BSL2 animal facility. Once there, open the box in the BSL2 cabinet.</li>
</ol>
2. P. aeruginosa Instillation
<ol>
	<li>Perform survival surgery aseptically (sterile gloves, sterile instruments, and aseptic techniques). Use a sterile drape to provide a working surface for sterile (autoclaved) surgical instruments. Sterilize instruments using a hot bead sterilizer between each tracheal instillation procedure.</li>
	<li>Weigh mice prior to anesthetization. Anesthetize mice with ketamine (100 mg/kg), xylazine (5 mg/kg), in 0.1 - 0.2 ml PBS intraperitoneally (i.p.). Determine the effectiveness of the anesthetic by non-responsiveness to toe pinch. Use a vet ointment on eyes to prevent dryness under anesthesia.</li>
	<li>Restrain mice on a surgical board in BSL2 cabinet.</li>
	<li>Identify the area for the cut down. Shave this area and prepare the skin using alternating alcohol and povidone iodine swabs 3 times.</li>
	<li>Treat the incision area with local anesthetic (lidocaine) as this anesthesia is sufficient for a minor surgery such as a skin incision to access the trachea.</li>
	<li>Make a small incision (approximately 5 mm) at the midline of the neck, and use blunt forceps to gently move the muscle for access to the trachea. Expose the trachea by surgical dissection.</li>
	<li>Draw bacteria solution into a 1 ml disposable syringe with 27 G needle. For each mouse, administer 20-30 &#181;l of bacteria at the appropriate concentration (up to 105 CFU each mouse).</li>
	<li>Insert needle into the trachea. Inject solution slowly into the tracheal.</li>
	<li>Ensure that the animal gasps, which usually indicates that solution has reached into the lung.</li>
	<li>Close the wound with sterile sutures (6-0 monofilament) under aseptic conditions.</li>
	<li>Use 0.1 mg/kg buprenorphine by subcutaneous injection as post-op analgesia to control post-surgical pain.</li>
	<li>Ensure that the time required from initial anesthetic induction to incision closure is less than 15 min.</li>
	<li>After injection, dispose of syringes and needles in an appropriate biohazard sharps container.</li>
	<li>Treat the surgical instruments with chlorine dioxide based disinfectant for 15 min, rinse and return to the lab for sterilization and reuse as necessary.</li>
	<li>House the mice singly in clean cages at warm environment.</li>
	<li>Check on the animal every 30 min until it regains consciousness and starts to move; and later at 12 hr intervals for the first 3 days post-surgery.</li>
	<li>Keep the mice in the animal BSL2 facility throughout the experiment. Ensure that only tissue contained in sealed box leaves the animal BSL2 facility. If the mice express any of the moribund behaviors (defined as respiratory distress, lethargy, failure to ambulate in response to gentle stimulation) at any point in the study, euthanize the mice by CO2 inhalation from a bottled source followed by cervical dislocation.</li>
	<li>Euthanize the experimental subject by exsanguination under anesthesia.
	<ol>
		<li>Collect lung tissue from euthanized mice. Carry out these procedures in a BSL2 hood. If needed, transfer the sample using sealed tubes placed in a rack on disinfectant laden paper towels in a snap lid box for further process.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Ware, L. B., Matthay, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+acute+respiratory+distress+syndrome.">The acute respiratory distress syndrome.</a> N Engl J Med. 342, 1334-1349 (2000).</li><li>Matthay, M. A., Ware, L. B., Zimmerman, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+acute+respiratory+distress+syndrome.">The acute respiratory distress syndrome.</a> J Clin Invest. 122, 2731-2740 (2012).</li><li>Shimabukuro, D. W., Sawa, T., Gropper, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Injury+and+repair+in+lung+and+airways.">Injury and repair in lung and airways.</a> Crit Care Med. 31 (8), 524-531 (2003).</li><li>Wansleeben, C., Barkauskas, C. E., Rock, J. R., Hogan, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stem+cells+of+the+adult+lung:+Their+development+and+role+in+homeostasis,+regeneration,+and+disease.">Stem cells of the adult lung: Their development and role in homeostasis, regeneration, and disease.</a> Wiley Interdiscip Rev Dev Biol. 2, 131-148 (2013).</li><li>Singleton, P. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamin+2+and+c-abl+are+novel+regulators+of+hyperoxia-mediated+nadph+oxidase+activation+and+reactive+oxygen+species+production+in+caveolin-enriched+microdomains+of+the+endothelium.">Dynamin 2 and c-abl are novel regulators of hyperoxia-mediated nadph oxidase activation and reactive oxygen species production in caveolin-enriched microdomains of the endothelium.</a> J Biol Chem. 284, 34964-34975 (2009).</li><li>Sadikot, R. T., Blackwell, T. S., Christman, J. W., Prince, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathogen-host+interactions+in+pseudomonas+aeruginosa+pneumonia.">Pathogen-host interactions in pseudomonas aeruginosa pneumonia.</a> Am J Respir Crit Care Med. 171, 1209-1223 (2005).</li><li>Liu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Foxm1+mediates+the+progenitor+function+of+type+ii+epithelial+cells+in+repairing+alveolar+injury+induced+by+pseudomonas+aeruginosa.">Foxm1 mediates the progenitor function of type ii epithelial cells in repairing alveolar injury induced by pseudomonas aeruginosa.</a> J Exp Med. 208, 1473-1484 (2011).</li><li>Kurahashi, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathogenesis+of+septic+shock+in+pseudomonas+aeruginosa+pneumonia.">Pathogenesis of septic shock in pseudomonas aeruginosa pneumonia.</a> J Clin Invest. 104, 743-750 (1999).</li><li>Kumar, P. 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J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sepsis+induces+early+alterations+in+innate+immunity+that+impact+mortality+to+secondary+infection.">Sepsis induces early alterations in innate immunity that impact mortality to secondary infection.</a> J Immunology. 186, 195-202 (2011).</li><li>Lange, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+murine+model+of+sepsis+following+smoke+inhalation+injury.">A murine model of sepsis following smoke inhalation injury.</a> Biochem Biophys Res Commun. 391 (3), 1555-1560 (2010).</li><li>Kobayashi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+chemokines+in+neutrophil+biology.">The role of chemokines in neutrophil biology.</a> Front Biosci. 13, 2400-2407 (2008).</li><li>Matute-Bello, G., et al. <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+acute+lung+injury.">Animal models of acute lung injury.</a> Am J Physiol Lung Cell Mol Physiol. 295, L379-L399 (2008).</li><li>Sadikot, R. 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The authors have nothing to disclose.

The Pseudomonas mouse lung injury model that we describe here mimics the whole process of inflammation, lung injury, repair, and resolution that occur following acute lung injury or pneumonia. It has unique advantages comparing with several other injury models in that it is clinically relevant and relatively safe and easy to handle.
The critical step in the procedure is that the injection of bacteria solution needs to be very slow. If injection is too fast, the mice are likely to die by choke....

Lungs are exposed to environmental pathogens and are susceptible to inflammation and injury1-3. During pathological conditions such as pneumonia or Adult Respiratory Distress Syndrome (ARDS), pathogens as well as inflammatory factors released by leukocytes induce injury and death of alveolar cells1-3. It is important to develop animal models of acute lung injury to facilitate the study of pathology of injury as well as mechanism of repair.
Currently, most people use hyperoxia and bleomycin induced mouse lung injury models4. However, the mechanisms of hyperoxia caused injury are not the same as most common lung injuries that occur during pneumonia or ARDS5. Bleomycin induced acute injury is rare in a clinical context4. Here we report a mouse lung injury model using intra-tracheal injection of P. aeruginosa 6,7. This model is clinically relevant, and mimics the processes that happen following pneumonia8.
As an opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa typically infects the pulmonary tract, urinary tract, burns, wounds, and also causes other blood infections6. The bacteria release virulence factor exotoxin A, multiply and trigger immune responses6. Intra-trachael administration of P. aeruginosa reflects the situation in human exposure to the bacteria which cause pneumonia and the pathology is likely to be different from the recently reported influenza virus H1N1 induced lung injury model9. Since P. aeruginosa is an opportunistic pathogen, it is relatively safe to handle as compared to some of the more virulent pathogens. &#160;Here we used intra-tracheal injection to administer the bacteria because we observed that this method introduced more bacteria into the distal alveoli region of the lung compared with some other procedures such as using a catheter via mouth.
Compared with other acute lung injury models, the P. aeruginosa model described here is suitable for studying lung injury induced by bacteria and by excessive inflammation. Unlike other animal models that use P. aeruginosa to induce sepsis10,11, here we use intra-tracheal injection of these bacteria to induce localized acute lung injury.

<table><tbody><tr><td>Anesthetic: Ketamin, xylazine, lidocaine, buprenorphine</td><td></td><td></td><td>pharmaceutical grade</td></tr><tr><td>27 G needle</td><td>Fisher</td><td>1482648</td><td></td></tr><tr><td>syringe</td><td>Fisher</td><td>14823434</td><td>1 ml</td></tr><tr><td>scissors</td><td>Fine Science tools</td><td></td><td></td></tr><tr><td>forceps</td><td>Fine Science tools</td><td></td><td></td></tr><tr><td>suture&amp;nbsp;</td><td>Fisher</td><td>19-037-526</td><td></td></tr><tr><td>Eye gauge, glove, gown</td><td></td><td></td><td></td></tr><tr><td>Biosafety Cabinet</td><td></td><td></td><td></td></tr><tr><td>chlorine dioxide based disinfectant</td><td></td><td></td><td>Clidox</td></tr><tr><td>sheep blood agar plates&amp;nbsp;</td><td>Medex supply</td><td>HL-1160</td><td></td></tr></tbody></table>

pseudomonas aeruginosa induced lung injury model

In order to study human acute lung injury and pneumonia, it is important to develop animal models to mimic various pathological features of this disease. Here we have developed a mouse lung injury model by intra-tracheal injection of bacteria Pseudomonas aeruginosa (P. aeruginosa or PA). Using this model, we were able to show lung inflammation at the early phase of injury. In addition, alveolar epithelial barrier leakiness was observed by analyzing bronchoalveolar lavage (BAL); and alveolar cell death was observed by Tunel assay using tissue prepared from injured lungs. At a later phase following injury, we observed cell proliferation required for the repair process. The injury was resolved 7 days from the initiation of P. aeruginosa injection. This model mimics the sequential course of lung inflammation, injury and repair during pneumonia. This clinically relevant animal model is suitable for studying pathology, mechanism of repair, following acute lung injury, and also can be used to test potential therapeutic agents for this disease.

Starting from 24 - 72 hr post P. aeruginosa injection, increased cellularity was observed in lung sections (Figure 1A-D). The lung started to recover from 96 hr post injury (Figure 1E). At 7 days post P. aeruginosa, normal alveoli morphology was largely restored (Figure 1F). Tunnel staining using lung sections prepared at 24 hr post P. aeruginosa showed cell death in alveoli cells (Figure 1G-I). In order to study the repair pro...

Watch this Scientific Journal Video about Pseudomonas aeruginosa Induced Lung Injury Model at JoVE.com

Pseudomonas aeruginosa Induced Lung Injury Model

We have developed a mouse lung injury model by intra-tracheal injection of bacteria Pseudomonas aeruginosa. This model mimics lung injury during pneumonia and is clinically relevant.

Pseudomonas aeruginosa Induced Lung Injury Model

In order to study human acute lung injury and pneumonia, it is important to develop animal models to mimic various pathological features of this disease. ...

pseudomonas-aeruginosa-induced-lung-injury-model

Research

JoVE Journal

Immunology and Infection

18.4K Views.  University of Illinois at Chicago. We have developed a mouse lung injury model by intra-tracheal injection of bacteria Pseudomonas aeruginosa. This model mimics lung injury during pneumonia and is clinically relevant. 

Video: Pseudomonas aeruginosa Induced Lung Injury Model

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 ...

A Method for Generating Pulmonary Neutrophilia Using Aerosolized Lipopolysaccharide

Acute lung injury (ALI) is a severe disease characterized by alveolar neutrophilia, with limited treatment options and high mortality. Experimental models of ALI are key in enhancing our understanding of disease pathogenesis. Lipopolysaccharide (LPS) derived from gram positive bacteria induces neutrophilic inflammation in the airways and lung parenchyma of mice. Efficient pulmonary delivery of compounds such as LPS is, however, difficult to achieve. In the approach described here, pulmonary delivery in mice is achieved by challenge to aerosolized Pseudomonas aeruginosa LPS. Dissolved LPS was aerosolized by a nebulizer connected to compressed air. Mice were exposed to a continuous flow of LPS aerosol in a Plexiglas box for 10 min, followed by 2 min conditioning after the aerosol was discontinued. Tracheal intubation and subsequent bronchoalveolar lavage, followed by formalin perfusion was next performed, which allows for characterization of the sterile pulmonary inflammation. Aerosolized LPS generates a pulmonary inflammation characterized by alveolar neutrophilia, detected in bronchoalveolar lavage and by histological assessment. This technique can be set up at a small cost with few appliances, and requires minimal training and expertise. The exposure system can thus be routinely performed at any laboratory, with the potential to enhance our understanding of lung pathology.

We describe a method for inducing neutrophilic pulmonary inflammation by challenge to aerosolized lipopolysaccharide by nebulization, to model acute lung injury. In addition, basic surgical techniques for lung isolation, tracheal intubation and bronchoalveolar lavage are also described.

Acute lung injury (ALI) is a severe disease characterized by alveolar neutrophilia, with limited treatment options and high mortality. Experimental models ...

Studying Microbial Communities In Vivo: A Model of Host-mediated Interaction Between Candida Albicans and Pseudomonas Aeruginosa in the Airways

Studying host-pathogen interaction enables us to understand the underlying mechanisms of the pathogenicity during microbial infection. The prognosis of the host depends on the involvement of an adapted immune response against the pathogen1. Immune response is complex and results from interaction of the pathogens and several immune or non-immune cellular types2. In vitro studies cannot characterise these interactions and focus on cell-pathogen interactions. Moreover, in the airway3, particularly in patients with suppurative chronic lung disease or in mechanically ventilated patients, polymicrobial communities are present and complicate host-pathogen interaction. Pseudomonas aeruginosa and Candida albicans are both problem pathogens4, frequently isolated from tracheobronchial samples, and associated to severe infections, especially in intensive care unit5. Microbial interactions have been reported between these pathogens in vitro but the clinical impact of these interactions remains unclear6. To study the interactions between C. albicans and P. aeruginosa, a murine model of C. albicans airways colonization, followed by a P. aeruginosa-mediated acute lung infection was performed.

Studying Microbial Communities In Vivo: A Model of Host-mediated Interaction Between Candida Albicans and Pseudomonas Aeruginosa in the Airways

While in vitro study of host-pathogen interactions allow the characterization of specific immune responses, in vivo models are required to observe the effects of complex responses. Using Candida albicans exposure followed by Pseudomonas aeruginosa-mediated lung infection, we established a murine model of microbial interactions involved in ventilator-associated pneumonia pathogenicity.

Studying host-pathogen interaction enables us to understand the underlying mechanisms of the pathogenicity during microbial infection. The prognosis of ...

A Robust Pneumonia Model in Immunocompetent Rodents to Evaluate Antibacterial Efficacy against S. pneumoniae, H. influenzae, K. pneumoniae, P. aeruginosa or A. baumannii

Efficacy of candidate antibacterial treatments must be demonstrated in animal models of infection as part of the discovery and development process, preferably in models which mimic the intended clinical indication. A method for inducing robust lung infections in immunocompetent rats and mice is described which allows for the assessment of treatments in a model of serious pneumonia caused by S. pneumoniae, H. influenzae, P. aeruginosa, K. pneumoniae or A. baumannii. Animals are anesthetized, and an agar-based inoculum is deposited deep into the lung via nonsurgical intratracheal intubation. The resulting infection is consistent, reproducible, and stable for at least 48 h and up to 96 h for most isolates. Studies with marketed antibacterials have demonstrated good correlation between in vivo efficacy and in vitro susceptibility, and concordance between pharmacokinetic/pharmacodynamic targets determined in this model and clinically accepted targets has been observed. Although there is an initial time investment when learning the technique, it can be performed quickly and efficiently once proficiency is achieved. Benefits of the model include elimination of the neutropenic requirement, increased robustness and reproducibility, ability to study more pathogens and isolates, improved flexibility in study design and establishment of a challenging infection in an immunocompetent host.

A Robust Pneumonia Model in Immunocompetent Rodents to Evaluate Antibacterial Efficacy against S. pneumoniae, H. influenzae, K. pneumoniae, P. aeruginosa or  A. baumannii

A method for establishing lung infections in immunocompetent rodents is described. With proficiency, this method can be performed quickly and easily to induce stable infection with many isolates of S. pneumoniae, H. influenzae, P. aeruginosa, K. pneumoniae and A. baumannii.

Efficacy of candidate antibacterial treatments must be demonstrated in animal models of infection as part of the discovery and development process, ...

An IL-8 Transiently Transgenized Mouse Model for the In Vivo Long-term Monitoring of Inflammatory Responses

Airway inflammation is often associated with bacterial infections and represents a major determinant of lung disease. The in vivo determination of the pro-inflammatory capabilities of various factors is challenging and requires terminal procedures, such as bronchoalveolar lavage and the removal of lungs for in situ analysis, precluding longitudinal visualization in the same mouse. Here, lung inflammation is induced through the intratracheal instillation of Pseudomonas aeruginosa culture supernatant (SN) in transiently transgenized mice expressing the luciferase reporter gene under the control of a heterologous IL-8 bovine promoter. Luciferase expression in the lung is monitored by in vivo bioluminescent image (BLI) analysis over a 2.5- to 48-h timeframe following the instillation. The procedure can be repeated multiple times within 2 - 3 months, thus permitting the evaluation of the inflammatory response in the same mice without the need to terminate the animals. This approach permits the monitoring of pro- and anti-inflammatory factors acting in the lung in real time and appears suitable for functional and pharmacological studies.

An IL-8 Transiently Transgenized Mouse Model for the In Vivo Long-term Monitoring of Inflammatory Responses

The method described here allows for the visualization of IL-8 promoter-dependent inflammation activation in the lungs of mice through non-invasive bioluminescence imaging (BLI). The same animal can be subjected to BLI multiple times for up to two months from the time of delivery of the luciferase reporter construct.

Airway inflammation is often associated with bacterial infections and represents a major determinant of lung disease. The in vivo determination of the ...

Open Tracheostomy Gastric Acid Aspiration Murine Model of Acute Lung Injury Results in Maximal Acute Nonlethal Lung Injury

Acid pneumonitis is a major cause of sterile acute lung injury (ALI) in humans. Acid pneumonitis spans the clinical spectrum from asymptomatic to acute respiratory distress syndrome (ARDS), characterized by neutrophilic alveolitis, and injury to both alveolar epithelium and vascular endothelium. Clinically, ARDS is defined by acute onset of hypoxemia, bilateral patchy pulmonary infiltrates and non-cardiogenic pulmonary edema. Human studies have provided us with valuable information about the physiological and inflammatory changes in the lung caused by ARDS, which has led to various hypotheses about the underling mechanisms. Unfortunately, difficulties determining the etiology of ARDS, as well as a wide range of pathophysiology have resulted in a lack of critical information that could be useful in developing therapeutic strategies.
Translational animal models are valuable when their pathogenesis and pathophysiology accurately reproduce a concept proven in both in vitro and clinical settings. Although large animal models (e.g., sheep) share characteristics of the anatomy of human trachea-bronchial tree, murine models provide a host of other advantages including: low cost; short reproductive cycle lending itself to greater data acquisition; a well understood immunologic system; and a well characterized genome leading to the availability of a variety of gene deletion and transgenic strains. A robust model of low pH induced ARDS requires a murine ALI that targets mainly the alveolar epithelium, secondarily the vascular endothelium, as well as the small airways leading to the alveoli. Furthermore, a reproducible injury with wide differences between different injurious and non-injurious insults is important.
The murine gastric acid aspiration model presented here using hydrochloric acid employs an open tracheostomy and recreates a pathogenic scenario that reproduces the low pH pneumonitis injury in humans. Additionally, this model can be used to examine interaction of a low pH insult with other pulmonary injurious entities (e.g., food particles, pathogenic bacteria).

This protocol induces acute lung injury in a mouse that has close fidelity to the pathogenesis of acid pneumonitis observed in humans. We generate a maximal acute nonlethal low pH lung injury and account for differences in rodent-human anatomic respiratory structure using an open tracheostomy coupled with circumferential pressure release.

Acid pneumonitis is a major cause of sterile acute lung injury (ALI) in humans. Acid pneumonitis spans the clinical spectrum from asymptomatic to acute ...

Medicine

A Model of Self-limited Acute Lung Injury by Unilateral Intra-bronchial Acid Instillation

Selective intra-bronchial instillation of hydrochloric acid (HCl) to the murine left mainstem bronchus causes acute tissue injury with histopathologic findings similar to human acute respiratory distress syndrome (ARDS). The resulting alveolar edema, alveolar-capillary barrier damage, and leukocyte infiltration predominantly affect the left lung, preserving the right lung as an uninjured control and allowing animals to survive. This model of self-limited acute lung injury enables investigation of tissue resolution mechanisms, such as macrophage efferocytosis of apoptotic neutrophils and restitution of alveolar-capillary barrier integrity. This model has helped identify important roles for resolution agonists, including specialized pro-resolving mediators (SPMs), providing a foundation for the development of new therapeutic approaches for patients with ARDS.

Selective intra-bronchial acid instillation to the left lung in mice results in unilateral and self-limited acute lung injury that models human acute respiratory distress syndrome (ARDS) induced by gastric acid aspiration.

Selective intra-bronchial instillation of hydrochloric acid (HCl) to the murine left mainstem bronchus causes acute tissue injury with histopathologic ...

A Delayed Inoculation Model of Chronic Pseudomonas aeruginosa Wound Infection

Pseudomonas aeruginosa (P. aeruginosa) is a major nosocomial pathogen of increasing relevance to human health and disease, particularly in the setting of chronic wound infections in diabetic and hospitalized patients. There is an urgent need for chronic infection models to aid in the investigation of wound pathogenesis and the development of new therapies against this pathogen. Here, we describe a protocol that uses delayed inoculation 24 hours after full-thickness excisional wounding. The infection of the provisional wound matrix present at this time forestalls either rapid clearance or dissemination of infection and instead establishes chronic infection lasting 7&#8211;10 days without the need for implantation of foreign materials or immune suppression. This protocol mimics a typical temporal course of post-operative infection in humans. The use of a luminescent P. aeruginosa strain (PAO1:lux) allows for quantitative daily assessment of bacterial burden for P. aeruginosa wound infections. This novel model may be a useful tool in the investigation of bacterial pathogenesis and the development of new therapies for chronic P. aeruginosa wound infections.

A Delayed Inoculation Model of Chronic Pseudomonas aeruginosa Wound Infection

We describe a delayed inoculation protocol for generating chronic wound infections in immunocompetent mice.

Pseudomonas aeruginosa (P. aeruginosa) is a major nosocomial pathogen of increasing relevance to human health and disease, particularly in the setting of ...

P. aeruginosa Infected 3D Co-Culture of Bronchial Epithelial Cells and Macrophages at Air-Liquid Interface for Preclinical Evaluation of Anti-Infectives

fDrug research for the treatment of lung infections is progressing towards predictive in vitro models of high complexity. The multifaceted presence of bacteria in lung models can re-adapt epithelial arrangement, while immune cells coordinate an inflammatory response against the bacteria in the microenvironment. While in vivo models have been the choice for testing new anti-infectives in the context of cystic fibrosis, they still do not accurately mimic the in vivo conditions of such diseases in humans and the treatment outcomes. Complex in vitro models of the infected airways based on human cells (bronchial epithelial and macrophages) and relevant pathogens could bridge this gap and facilitate the translation of new anti-infectives into the clinic. For such purposes, a co-culture model of the human cystic fibrosis bronchial epithelial cell line CFBE41o- and THP-1 monocyte-derived macrophages has been established, mimicking an infection of the human bronchial mucosa by P. aeruginosa at air-liquid interface (ALI) conditions. This model is set up in seven days, and the following parameters are simultaneously assessed: epithelial barrier integrity, macrophage transmigration, bacterial survival, and inflammation. The present protocol describes a robust and reproducible system for evaluating drug efficacy and host responses that could be relevant for discovering new anti-infectives and optimizing their aerosol delivery to the lungs.

P. aeruginosa Infected 3D Co-Culture of Bronchial Epithelial Cells and Macrophages at Air-Liquid Interface for Preclinical Evaluation of Anti-Infectives

We describe a protocol for a three-dimensional co-culture model of infected airways, using CFBE41o- cells, THP-1 macrophages, and Pseudomonas aeruginosa, established at the air-liquid interface. This model provides a new platform to simultaneously test antibiotic efficacy, epithelial barrier function, and inflammatory markers.

fDrug research for the treatment of lung infections is progressing towards predictive in vitro models of high complexity. The multifaceted presence of ...

Inducing Acute Lung Injury in Mice by Direct Intratracheal Lipopolysaccharide Instillation

Airway administration of lipopolysaccharide (LPS) is a common way to study pulmonary inflammation and acute lung injury (ALI) in small animal models. Various approaches have been described, such as the inhalation of aerosolized LPS as well as nasal or intratracheal instillation. The presented protocol describes a detailed step-by-step procedure to induce ALI in mice by direct intratracheal LPS instillation and perform FACS analysis of blood samples, bronchoalveolar lavage (BAL) fluid, and lung tissue. After intraperitoneal sedation, the trachea is exposed and LPS is administered via a 22 G venous catheter. A robust and reproducible inflammatory reaction with leukocyte invasion, upregulation of proinflammatory cytokines, and disruption of the alveolo-capillary barrier is induced within hours to days, depending on the LPS dosage used. Collection of blood samples, BAL fluid, and lung harvesting, as well as the processing for FACS analysis, are described in detail in the protocol. Although the use of the sterile LPS is not suitable to study pharmacologic interventions in infectious diseases, the described approach offers minimal invasiveness, simple handling, and good reproducibility to answer mechanistic immunological questions. Furthermore, dose titration as well as the use of alternative LPS preparations or mouse strains allow modulation of the clinical effects, which can exhibit different degrees of ALI severity or early vs. late onset of disease symptoms.

Presented here is a step-by-step procedure to induce acute lung injury in mice by direct intratracheal lipopolysaccharide instillation and to perform FACS analysis of blood samples, bronchoalveolar lavage fluid, and lung tissue. Minimal invasiveness, simple handling, good reproducibility, and titration of disease severity are advantages of this approach.

Airway administration of lipopolysaccharide (LPS) is a common way to study pulmonary inflammation and acute lung injury (ALI) in small animal models. ...

Pseudomonas aeruginosa Induced Lung Injury Model

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