Characterization of a Mouse Model of Emphysema Induced by Multiple Instillations of Low-Dose Elastase

Abstract

Many experimental models have been proposed to study the pathophysiological features of emphysema, as well as to search for new therapeutic approaches for acute or chronically injured lung parenchyma. We aimed to characterize an emphysema model induced by multiple instillations of elastase by tracking changes in inflammation, remodeling, and cardiac function after each instillation. Forty-eight C57BL/6 mice were randomly assigned across two groups. Emphysema (ELA) animals received 1, 2, 3, or 4 intratracheal instillations of pancreatic porcine elastase (PPE, 0.2 IU) with a 1-week interval between them. Controls (C) received saline following the same protocol. Before and after implementation of the protocol, animals underwent echocardiographic analysis. After the first instillation of PPE, the percentage of mononuclear cells in the lung parenchyma increased compared to C (p = 0.0001). The second instillation resulted in hyperinflated alveoli, increased mean linear intercept, and reduced elastic fiber content in lung parenchyma compared to C (p = 0.0197). Following the third instillation, neutrophils and collagen fiber content in alveolar septa and airways increased, whereas static lung elastance was reduced compared to C (p = 0.0094). After the fourth instillation, the percentage of M1 macrophages in lungs; levels of interleukin-1β (IL-1β), keratinocyte-derived chemokine, hepatocyte growth factor (HGF), and vascular endothelial growth factor (VEGF); and collagen fiber content in the pulmonary vessel wall were increased compared to C (p = 0.0096). At this time point, pulmonary arterial hypertension was apparent, with increased diastolic right ventricular wall thickness. In conclusion, the initial phase of emphysema was characterized by lung inflammation with predominance of mononuclear cells, whereas at the late stage, impairment of pulmonary and cardiovascular functions was observed. This model enables analysis of therapies at different time points during controlled progression of emphysema. Accordingly, early interventions could focus on the inflammatory process, while late interventions should focus on restoring cardiorespiratory function.

Ghrelin therapy improves lung and cardiovascular function in experimental emphysema

“…Both models may result in cachexia [ 39 ] and pulmonary hypertension [ 40 ], but the lung damage induced by elastase persists for longer after induction in contrast to cigarette smoke [ 41 ]. In addition to lung structural damage induced by PPE, a persistent lung inflammatory process [ 42 ] with elastolysis and fibrogenesis has been observed [ 32 ]. The specific elastase-induced emphysema protocol used in the present study has been shown to produce loss of lean and total body mass, likely suggesting cachexia [ 43 ].…”

“…Sample size calculation was based on pilot studies and on previous studies in a murine model of elastase induced emphysema conducted in our laboratory [ 26 , 27 , 29 , 31 , 32 ]. A sample size of ten animals per group would provide the appropriate power (1 − β = 0.8) to identify significant (α = 0.05) differences in mean linear intercept between C and ELA groups, taking into account an effect size d = 1.97, a two-sided test, and a sample size ratio = 1 (G * - Power 3.1.9.2, University of Düsseldorf, Germany).…”

Variability in Tidal Volume Affects Lung and Cardiovascular Function Differentially in a Rat Model of Experimental Emphysema

“…To the best of our knowledge, this was the first investigation of the effects of different levels of V T variability on pulmonary and cardiovascular function, lung morphometry, and gene expression of markers of inflammation, surfactant proteins, epithelial cell damage, cell mechanical stress, and fibrogenesis in experimental emphysema. We chose the repeated intratracheal elastase instillation model because it reproduces important features of emphysema, including deterioration of respiratory system mechanics, airspace enlargement, and lung inflammation (Antunes and Rocco, 2011 ; Cruz et al, 2012 ; Henriques et al, 2016 ; Oliveira et al, 2016 ; Padilha et al, 2016 ; Rocha et al, 2017 ; Suki et al, 2017 ). Furthermore, multiple elastase instillations can lead to cardiorespiratory alterations (Antunes et al, 2014 ) that are consistent with cor pulmonale , including increased RV afterload (Henriques et al, 2016 ).…”

Platelet-derived growth factor receptor-α and Ras-related C3 botulinum toxin substrate-1 regulate mechano-responsiveness of lung fibroblasts

“…Circulating procollagen peptides are elevated following COPD exacerbations, consistent with active collagen synthesis (51). When administered intratracheally to mice, porcine pancreatic elastase increases rather than decreases collagen (14,42), particularly in regions of emphysema. Other studies suggest that a nonuniform distribution of collagen produces mechanical forces, which propagate emphysema after inflammation abates (17).…”