Mouse Model of Oleic Acid-Induced Acute Respiratory Distress Syndrome

Summary

The present protocol describes a lung injury model in mice using oleic acid to mimic acute respiratory distress syndrome (ARDS). This model increases the inflammatory mediators on edema and decreases lung compliance. Oleic acid is used in the salt form (oleate) since this physiological form avoids the risk of embolism.

Abstract

Acute respiratory distress syndrome (ARDS) is a significant threat to critically ill patients with a high fatality rate. Pollutant exposure, cigarette smoke, infectious agents, and fatty acids can induce ARDS. Animal models can mimic the complex pathomechanism of the ARDS. However, each of them has limitations. Notably, oleic acid (OA) is increased in critically ill patients with harmful effects on the lung. OA can induce lung injury by emboli, disrupting tissue, altering pH, and impairing edema clearance. OA-induced lung injury model resembles various features of ARDS with endothelial injury, increased alveolar permeability, inflammation, membrane hyaline formation, and cell death. Herein, induction of lung injury is described by injecting OA (in salt form) directly into the lung and intravenously in a mouse since it is the physiological form of OA at pH 7. Thus, the injection of OA in the salt form is a helpful animal model to study lung injury/ARDS without causing emboli or altering the pH, thereby getting close to what is happening in critically ill patients.

Introduction

Ashbaugh et al.¹, in 1967, first described the acute respiratory distress syndrome (ARDS) and since then has been through multiple revisions. According to the Berlin definition, ARDS is a pulmonary inflammation that leads to an acute respiratory failure and hypoxemia (PaO₂/FiO₂ > 300 mm Hg) due to imbalance in the ventilation to perfusion ratio, diffuse bilateral alveolar damage (DAD) and infiltrate, increased lung weight, and edema^2,3. The pulmonary parenchyma is a complex cellular environment compounded by epithelial, endothelial, and other cells. These cells....

Protocol

The procedures used in this study were approved by the Ethics Committee on the Use of Animals of the Oswaldo Cruz Foundation (CEUA licenses n°002-08, 36/10 and 054/2015). Male Swiss Webster mice weighing between 20-30 g, provided by the Institute of Science and Technology in Biomodels (ICTB) of the Oswaldo Cruz Foundation (FIOCRUZ), were used for the experiments. The animals were kept in ventilated isolators in the Pavilhão Ozório de Almeida's vivarium, and water and food were available ad libitum<.......

Discussion

Selecting the correct ARDS model is essential to carry out the preclinical studies, and the evaluator must consider all the possible variables, such as age, sex, administration methods, and others⁶. The chosen model must reproduce the disease based on risk factors such as sepsis, lipid embolism, ischemia-reperfusion of the pulmonary vasculature, and other clinical risks¹⁴. However, no animal model used for ARDS can recreate all the human syndrome's features. Multiple in.......

Materials

Name	Company	Catalog Number	Comments
Anesthetic vaporizer	SurgiVet	model 100
Braided slik thread with needle number 5	Shalon medical	N/A
Cabinet vivarium	Insight	Model EB273
Centrifuge	Eppendorf	5430/5430R
Cytofunnel	ThermoFisher	11-025-48
Drontal puppy	Bayer	N/A
Hank's balanced Salts	Sigma-Aldrich	H4981
Heatpad	tkreprodução	TK-500
Hydrocloric Acid	Sigma-Aldrich	30721
Insulin syringe Ultrafine	BD	328322
Isoforine 1mL/mL	Cristália	N/A
Ketamine	Syntec	N/A
May-Grunwald-Giemsa	Sigma-Aldrich	205435
Micro BCA Protein Assay Kit	ThermoFisher	23235
Microscope  PrimoStar	Carl Zeiss
Mouse IL-1 beta duoSet ELISA	R&D system	DY401
Mouse IL-6 duoSet ELISA	R&D system	DY406
Mouse TNF-alpha duoSet ELISA	R&D system	DY410
Neubauer chamber improved bright-line	Global optics
Oleic Acid (99%)	Sigma-Aldrich	O1008
Osmium tetroxide solution (4%)	Sigma-Aldrich	75632
Peripheral Intravenous Catherter 20 G	BD Angiocath	388333
Prism 8 (graphic and statistic software)	Graphpad	N/A
Prostaglandin E2 ELISA Kit -Monoclonal	Cayman Chemical	514010
Shandon Cytospin 3	ThermoFisher	N/A
Sodium hydroxide	Merck	1,06,49,81,000
Spectrophotometer	Molecular Devices	SpectraMax ABS plus
Swiss webster mice	ICTB/FIOCRUZ	N/A
Syringe 1 mL	BD	990189
Tris-base	Bio Rad	161-0719	Electrophoresis purity reagent
Türk's solution	Sigma-Aldrich	93770
Xilazine	Syntec	N/A