Protocol Preview: a Ferret Model of Respiratory Inflammation

Blog post by Jasmin Skinner

Acute lung injury is the pulmonary manifestation of acute systemic inflammation, and is a major cause of morbidity and mortality in the United States [1]. Although its incidence and outcomes have been historically difficult to determine, one 2005 study estimated that acute lung injury is associated with 74,500 deaths annually in the United States, as well as 3.6 million hospital days [2]. Additionally, research has shown that physical, cognitive, and mental health impairments are common and persistent following acute lung injury [3]. Despite its significant impact on public health, the inflammation and tissue damage that occurs alongside this condition has been difficult to treat.

Inflammatory lung injuries can result from both infectious and non-infectious sources [4]. Viral and bacterial infections like influenza, pneumonia, and SARS-CoV-2 will typically elicit an acute inflammatory response, and could lead to severe complications such as acute respiratory distress syndrome [5]. The inflammatory response to these infections results in an influx of immune cells into the lungs, which is often accompanied by a series of pro-inflammatory agents (e.g., interleukin-8) and reactive oxygen species that can damage lung tissue [4]. While there is some understanding of the cellular components involved in this process, treatment plans and the underlying mechanisms driving tissue injury are not as well characterized, and appropriate preclinical models are needed.

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Challenges with modeling respiratory inflammation

While rodents have long been used to model many human diseases, the differences in anatomy, physiology, and immunology between humans and mice cannot be ignored when modeling respiratory inflammation. Their small size in particular poses several challenges, as traditional methods for measuring their respiratory function like pulmonary function testing (PFT) are often extremely invasive and fatal, which limits their use in long-term studies [4]. While less invasive PFT approaches have been attempted (e.g., plethysmography), they often still require invasive procedures to capture the full respiratory effect [4]. Larger animals such as pigs and non-human primates tend to have more similar biology to humans, but are more expensive and raise ethical considerations [4]. Recently, one group of researchers proposed a ferret model as a solution to modeling respiratory inflammation at the preclinical stage. 

Why use a ferret model in preclinical respiratory inflammation studies?

Although ferrets may seem like an unlikely candidate as a preclinical model, they present many advantages to studies of respiratory inflammation. Their larger size compared to mice reduces the risk of fatality after PFT, and they can be intubated more easily [4]. Ferrets also have a high propensity for pathogenic infections, can experience disease mutations that are relevant to humans (e.g., cystic fibrosis), and demonstrate similar pathology and disease progression as humans. Previous studies have shown that ferrets can be used to study infections in immunocompromised hosts [6] and vaccine efficacy against influenza [7]. Recently, Khoury et al. further demonstrated how ferrets can be used to model inflammatory respiratory disease and injury, which we review in this Protocol Preview [4].

Measuring lung function in ferret models of lung inflammatory disease

To evaluate the appropriateness of using ferrets as a model for inflammatory disease, the authors exposed conscious animals to nebulized lipopolysaccharide (LPS) daily for seven days, one hour at a time, while saline was administered to control animals (Figure 1). Lung function was evaluated in anesthetized ferrets both prior to and after LPS or saline administration using a forced pulmonary maneuver system. Afterwards, the ferrets were euthanized and a bronchoalveolar lavage was performed to assess what might be present in their lungs.

Study timeline for a ferret respiratory inflammation model

Figure 1: Study timeline for a ferret respiratory inflammation model. © 2022 Khoury et al., licensed under CC BY 4.0.

Important findings and implications

Following seven days of exposure to nebulized LPS, the authors observed a decrease in ferret lung function, similarly to what is observed clinically in patients with acute lung injury. Histological analysis also confirmed that LPS exposure resulted in alveolar damage and pulmonary neutrophilic inflammation (Figure 2). The authors note that this decline in lung function is likely due to similar respiratory anatomy between ferrets and humans. For example, ferrets have a similar number of generations of terminal bronchioles as humans and express relevant receptors (e.g., influenza receptor) and mutations (e.g., CFTR).

Lung histological changes in ferrets following saline and/or LPS administration

Figure 2: Changes in lung histology following administration of saline and/or LPS. © 2022 Khoury et al., licensed under CC BY 4.0.

Additionally, the larger size of ferrets compared to mice allows for easier and repeated intubation, making them an excellent choice for longitudinal respiratory studies. Ferrets are also far less expensive to purchase and care for than other non-murine models, and require less space than larger animal models. The results obtained in this study suggest that this approach  improves upon established preclinical respiratory models, as repeated lung function measurements can be performed on ferrets with minimal harm to the animal.

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About the Author

About the Author

Jasmin Skinner is an undergraduate student at the University of Western Ontario completing a Specialization in Biology and a Minor in Chemistry, with focused interest in applying these concepts to environmental conservation. As a lover of the outdoors and the arts, much of her time is spent in nature and within the local London art community, creating and connecting with all walks of life. After graduating, she hopes to continue her passion of finding unconventional solutions to environmental issues by working with nature, not against it.


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