Experimental models in pulmonary pathology

Full Assessment of Lung Mechanics Using Computer-Controlled, Forced Oscillation Technique

The forced oscillation technique (FOT) is a powerful and accurate method to quantify the mechanical properties of the airways and tissues of the respiratory system. Here we provide a detailed protocol for the measurement of mouse respiratory mechanical parameters. We present a procedure for mouse endotracheal intubation using a handcrafted intubation platform and confirmation module. The FlexiVentFX™ system (Scireq Inc.) is utilized for the thorough assessment of lung function with the FlexiWare™ software serving as a unit for the planning, experimentation, and analysis. The protocol has been standardized and adapted for use by our center for lung-function phenotyping of mouse models generated for the International Mouse Phenotyping Consortium (IMPC). The simplified steps, technical considerations, and integrated hardware-software demonstration make this protocol adaptable and implementable for researchers interested in using FOT for lung-function evaluation. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Support Protocol 1: Assembly of the FlexiVentFX™ system for measurements Support Protocol 2: FlexiWare database management Support Protocol 3: A guide for the construction of intubation platform and confirmation module Basic Protocol 1: Mouse endotracheal intubation Basic Protocol 2: Assessment of mouse basal lung function.

Intratracheal bleomycin causes airway remodeling and airflow obstruction in mice

In addition to parenchymal fibrosis, fibrotic remodeling of the distal airways has been reported in interstitial lung diseases. Mechanisms of airway wall remodeling, which occurs in a variety of chronic lung diseases, are not well defined and current animal models are limited. The authors quantified airway remodeling in lung sections from subjects with idiopathic pulmonary fibrosis (IPF) and controls. To investigate intratracheal bleomycin as a potential animal model for fibrotic airway remodeling, the authors evaluated lungs from C57BL/6 mice after bleomycin treatment by histologic scoring for fibrosis and peribronchial inflammation, morphometric evaluation of subepithelial connective tissue volume density, TUNEL (terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling) assay, and immunohistochemistry for transforming growth factor β1 (TGFβ1), TGFβ2, and the fibroblast marker S100A4. Lung mechanics were determined at 3 weeks post bleomycin. IPF lungs had small airway remodeling with increased bronchial wall thickness compared to controls. Similarly, bleomycin-treated mice developed dose-dependent airway wall inflammation and fibrosis and greater airflow resistance after high-dose bleomycin. Increased TUNEL(+) bronchial epithelial cells and peribronchial inflammation were noted by 1 week, and expression of TGFβ1 and TGFβ2 and accumulation of S100A4(+) fibroblasts correlated with airway remodeling in a bleomycin dose-dependent fashion. IPF is characterized by small airway remodeling in addition to parenchymal fibrosis, a pattern also seen with intratracheal bleomycin. Bronchial remodeling from intratracheal bleomycin follows a cascade of events including epithelial cell injury, airway inflammation, profibrotic cytokine expression, fibroblast accumulation, and peribronchial fibrosis. Thus, this model can be utilized to investigate mechanisms of airway remodeling.

Animal models of airway inflammation and airway smooth muscle remodelling in asthma

Asthma is a complex disease that involves chronic inflammation and subsequent decline in airway function. The widespread use of animal models has greatly contributed to our understanding of the cellular and molecular pathways underlying human allergic asthma. Animal models of allergic asthma include smaller animal models which offer 'ease of use' and availability of reagents, and larger animal models that may be used to address aspects of allergic airways disease not possible in humans or smaller animal models. This review examines the application and suitability of various animal models for studying mechanisms of airway inflammation and tissue remodelling in allergic asthma, with a specific focus on airway smooth muscle.

Variability of interalveolar septal remodeling after bleomycin treatment in mice

Although bleomycin-induced cellular injury in the lung parenchyma is followed by the development of patchy fibrosis, the authors hypothesized that remodeling of the interalveolar septum (IAS) following bleomycin is a diffuse process not limited to the formation of discrete fibrotic areas. To determine the spectrum of changes in the IAS induced by bleomycin treatment, lungs were harvested from mice at 1, 2, 3, and 4 weeks following intratracheal administration of 0.04, 0.06, or 0.08 units of bleomycin. Light microscopy with quantitative morphometric techniques and electron microscopy were used to evaluate the IAS alterations. At 4 weeks after treatment, there was evidence of diffuse IAS remodeling. By morphological analysis, two types of structural remodeling of the IAS were observed. One type showed thickening with extracellular matrix deposition and hyperplasia of lining epithelial cells. The other type showed localized thinning of the interstitium with capillary loss and reduction in number and in size of epithelial cells. The authors have defined these variants as septal thickening and septal atrophy, respectively. The findings indicate that studies investigating the pathogenesis of lung fibrosis should focus on septal remodeling as well as analysis of fibrotic foci and measurement of collagen content.

Atopic NC/Nga mice as a model for allergic asthma: severe allergic responses by single intranasal challenge with protein antigen

Since certain characters of allergic asthma are common with other allergic disorders like atopic dermatitis, the possible relationship in etiology is expected. Herein, we investigated whether NC/Nga mice, an inherent animal model for human atopic dermatitis, are inclined to allergic asthma. A single intranasal challenge of NC/Nga mice immunized with ovalbumin (OVA) resulted in an increase in plasma levels of OVA-specific IgE, and typical pathological aspects of allergic asthma characterized by infiltration of numerous eosinophils, mucus hyper production of bronchial epithelial cells. Moreover, airway hyperresponsiveness to inhaled acetylcholine and marked enhancement of airway resistance after the challenge were observed as compared to control BALB/c mice. Delayed expression of mRNA of eosinophil active chemokines, interleukin-5, eotaxin, macrophage inflammatory protein-1alpha in concert with eosinophilia was determined in the lung of NC/Nga mice. These results suggest that asthmatic responses developed in NC/Nga mice challenged with OVA are very similar to human allergic asthma, and that NC/Nga mice are a useful model to elucidate various aspects of allergic asthma.

Repeated intratracheal challenge with particulate antigen modulates murine lung cytokines

When lungs of experimental animals are repeatedly challenged with Ag, pulmonary inflammation wanes via unknown mechanisms. We hypothesized that changes in the balance of lung cytokines are responsible for immune down-regulation to repeated Ag challenge. We used intratracheal (IT) challenge of primed C57BL/6 mice with SRBC and on various days after single (1IT) or triple (3IT) challenge counted lung inflammatory cells and measured whole-lung cytokine mRNA and protein concentrations using RT-PCR and ELISA. We found that lung lymphocyte numbers and parenchymal lung inflammation decreased significantly at days 6 and 9 after final Ag challenge in 3IT mice compared with 1IT mice. Lungs of 3IT mice showed the following changes in relative mRNA expression: an earlier peak in IL-10, decreased IL-1beta, and a change from a Th2 response in 1IT mice to a Th1 response in 3IT mice (with pronounced increases in IL-12, IL-18, and IFN-gamma and decreased IL-4, IL-13, and IL-5). Similar types of changes were seen in whole-lung protein concentrations for TNF-alpha, IL-10, IL-12 p40, IFN-gamma, and IL-4. Additionally, mRNA expression of the endothelial selectins CD62E and CD62P decreased and lung lymphocyte apoptosis increased in the 3IT group. Thus, physiologic down-regulation of the pulmonary immune response to repeated Ag exposure is characterized by increased anti- and decreased proinflammatory cytokines that accompanies Th1 polarization. Similar mechanisms may act to minimize chronic lung inflammation in the majority of normal humans who do not develop progressive lung pathology when repeatedly exposed to inhaled or aspirated environmental Ags.