Comparison of Two Quantitative Methods of Discerning Airspace Enlargement in Smoke-Exposed Mice

In this work, we compare two methods for evaluating and quantifying pulmonary airspace enlargement in a mouse model of chronic cigarette smoke exposure. Standard stereological sample preparation, sectioning, and imaging of mouse lung tissues were performed for semi-automated acquisition of mean linear intercept (Lm) data. After completion of the Lm measurements, D2, a metric of airspace enlargement, was measured in a blinded manner on the same lung images using a fully automated technique developed in-house. An analysis of variance (ANOVA) shows that although Lm was able to separate the smoke-exposed and control groups with statistical significance (p = 0.034), D2 was better able to differentiate the groups (p<0.001) and did so without any overlap between the control and smoke-exposed individual animal data. In addition, the fully automated implementation of D2 represented a time savings of at least 24x over semi-automated Lm measurements. Although D2 does not provide 3D stereological metrics of airspace dimensions as Lm does, results show that it has higher sensitivity and specificity for detecting the subtle airspace enlargement one would expect to find in mild or early stage emphysema. Therefore, D2 may serve as a more accurate screening measure for detecting early lung disease than Lm

PPARγ deficiency results in reduced lung elastic recoil and abnormalities in airspace distribution

Background: Peroxisome proliferator-activated receptor (PPAR)-γ is a nuclear hormone receptor that regulates gene expression, cell proliferation and differentiation. We previously described airway epithelial cell PPARγ deficient mice that develop airspace enlargement with decreased tissue resistance and increased lung volumes. We sought to understand the impact of airspace enlargement in conditionally targeted mice upon the physio-mechanical properties of the lung. Methods: We measured elastic recoil and its determinants, including tissue structure and surface forces. We measured alveolar number using radial alveolar counts, and airspace sizes and their distribution using computer-assisted morphometry. Results: Air vs. saline-filled pressure volume profiles demonstrated loss of lung elastic recoil in targeted mice that was contributed by both tissue components and surface tension, but was proportional to lung volume. There were no significant differences in surfactant quantity/function nor in elastin and collagen content between targeted animals and littermate controls. Importantly, radial alveolar counts were significantly reduced in the targeted animals and at 8 weeks of age there were 18% fewer alveoli with 32% more alveolar ducts. Additionally, the alveolar ducts were 19% larger in the targeted animals. Conclusions: Our data suggest that the functional abnormalities, including loss of recoil are secondary to altered force transmission due to differences in the structure of alveolar ducts, rather than changes in surfactant function or elastin or collagen content. These data further define the nature of abnormal lung maturation in the absence of airway epithelial cell PPARγ and identify a putative genetic determinant of dysanapsis, which may serve as a precursor to chronic lung disease

Role of the tachykinin NK1 receptor in a murine model of cigarette smoke-induced pulmonary inflammation

<p>Abstract</p> <p>Background</p> <p>The tachykinins, substance P and neurokinin A, present in sensory nerves and inflammatory cells such as macrophages and dendritic cells, are considered as pro-inflammatory agents. Inflammation of the airways and lung parenchyma plays a major role in the pathogenesis of chronic obstructive pulmonary disease (COPD) and increased tachykinin levels are recovered from the airways of COPD patients. The aim of our study was to clarify the involvement of the tachykinin NK₁receptor, the preferential receptor for substance P, in cigarette smoke (CS)-induced pulmonary inflammation and emphysema in a mouse model of COPD.</p> <p>Methods</p> <p>Tachykinin NK₁receptor knockout (NK₁-R^-/-) mice and their wild type controls (all in a mixed 129/sv-C57BL/6 background) were subjected to sub acute (4 weeks) or chronic (24 weeks) exposure to air or CS. 24 hours after the last exposure, pulmonary inflammation and development of emphysema were evaluated.</p> <p>Results</p> <p>Sub acute and chronic exposure to CS resulted in a substantial accumulation of inflammatory cells in the airways of both WT and NK₁-R^-/-mice. However, the CS-induced increase in macrophages and dendritic cells was significantly impaired in NK₁-R^-/-mice, compared to WT controls, and correlated with an attenuated release of MIP-3α/CCL20 and TGF-β1. Chronic exposure to CS resulted in development of pulmonary emphysema in WT mice. NK₁-R^-/-mice showed already enlarged airspaces upon air-exposure. Upon CS-exposure, the NK₁-R^-/-mice did not develop additional destruction of the lung parenchyma. Moreover, an impaired production of MMP-12 by alveolar macrophages upon CS-exposure was observed in these KO mice. In a pharmacological validation experiment using the NK₁receptor antagonist RP 67580, we confirmed the protective effect of absence of the NK₁receptor on CS-induced pulmonary inflammation.</p> <p>Conclusion</p> <p>These data suggest that the tachykinin NK₁receptor is involved in the accumulation of macrophages and dendritic cells in the airways upon CS-exposure and in the development of smoking-induced emphysema. As both inflammation of the airways and parenchymal destruction are important characteristics of COPD, these findings may have implications in the future treatment of this devastating disease.</p

Recurrent Recruitment Manoeuvres Improve Lung Mechanics and Minimize Lung Injury during Mechanical Ventilation of Healthy Mice

INTRODUCTION: Mechanical ventilation (MV) of mice is increasingly required in experimental studies, but the conditions that allow stable ventilation of mice over several hours have not yet been fully defined. In addition, most previous studies documented vital parameters and lung mechanics only incompletely. The aim of the present study was to establish experimental conditions that keep these parameters within their physiological range over a period of 6 h. For this purpose, we also examined the effects of frequent short recruitment manoeuvres (RM) in healthy mice. METHODS: Mice were ventilated at low tidal volume V(T) = 8 mL/kg or high tidal volume V(T) = 16 mL/kg and a positive end-expiratory pressure (PEEP) of 2 or 6 cm H(2)O. RM were performed every 5 min, 60 min or not at all. Lung mechanics were followed by the forced oscillation technique. Blood pressure (BP), electrocardiogram (ECG), heart frequency (HF), oxygen saturation and body temperature were monitored. Blood gases, neutrophil-recruitment, microvascular permeability and pro-inflammatory cytokines in bronchoalveolar lavage (BAL) and blood serum as well as histopathology of the lung were examined. RESULTS: MV with repetitive RM every 5 min resulted in stable respiratory mechanics. Ventilation without RM worsened lung mechanics due to alveolar collapse, leading to impaired gas exchange. HF and BP were affected by anaesthesia, but not by ventilation. Microvascular permeability was highest in atelectatic lungs, whereas neutrophil-recruitment and structural changes were strongest in lungs ventilated with high tidal volume. The cytokines IL-6 and KC, but neither TNF nor IP-10, were elevated in the BAL and serum of all ventilated mice and were reduced by recurrent RM. Lung mechanics, oxygenation and pulmonary inflammation were improved by increased PEEP. CONCLUSIONS: Recurrent RM maintain lung mechanics in their physiological range during low tidal volume ventilation of healthy mice by preventing atelectasis and reduce the development of pulmonary inflammation

Inhaled aerosol particle dosimetry in mice: A review

The availability of molecular and genetic tools has made the mouse the most common animal model for a variety of human diseases in toxicology studies. However, little is known about the factors that will influence the dose delivery to murine lungs during an inhalation study. Among these factors are the respiratory tract anatomy, lung physiology, and clearance characteristics. Therefore, the objective of this paper is to briefly review the current knowledge on the aforementioned factors in mice and their implications to the dose delivered to mouse models during inhalation studies. Representative scientific publications were chosen from searches using the NCBI PubMed and ISI Web of Knowledge databases. Relevant respiratory physiological differences have been widely reported for different mouse strains and sexes. The limited data on anatomical morphometry that is available for the murine respiratory tract indicates significant differences between mouse strains. These differences have implications to the dose delivered and the biological outcomes of inhalation studies