Administration of Bleomycin via the Oropharyngeal Aspiration Route Leads to Sustained Lung Fibrosis in Mice and Rats as Quantified by UTE-MRI and Histology

Christine Egger,Arthur Micard,Gabor Jarai,Thomas Suply,Bruno Tigani,Elizabeth Jarman,Nicolau Beckmann,Catherine Cannet,Agnès Feige,Andrew Dunbar,Christelle Gérard,Oliver Eickelberg

doi:10.1371/journal.pone.0063432

Abstract

Pulmonary fibrosis can be experimentally induced in small rodents by bleomycin. The antibiotic is usually administered via the intratracheal or intranasal routes. In the present study, we investigated the oropharyngeal aspiration of bleomycin as an alternative route for the induction of lung fibrosis in rats and mice. The development of lung injury was followed in vivo by ultrashort echo time magnetic resonance imaging (UTE-MRI) and by post-mortem analyses (histology of collagen, hydroxyproline determination, and qRT-PCR). In C57BL/6 mice, oropharyngeal aspiration of bleomycin led to more prominent lung fibrosis as compared to intranasal administration. Consequently, the oropharyngeal aspiration route allowed a dose reduction of bleomycin and, therewith, a model refinement. Moreover, the distribution of collagen after oropharyngeal aspiration of bleomycin was more homogenous than after intranasal administration: for the oropharyngeal aspiration route, fibrotic areas appeared all over the lung lobes, while for the intranasal route fibrotic lesions appeared mainly around the largest superior airways. Thus, oropharyngeal aspiration of bleomycin induced morphological changes that were more comparable to the human disease than the intranasal administration route did. Oropharyngeal aspiration of bleomycin led to a homogeneous fibrotic injury also in rat lungs. The present data suggest oropharyngeal aspiration of bleomycin as a less invasive means to induce homogeneous and sustained fibrosis in the lungs of mice and rats.

Highlights

Pulmonary fibrosis, characterized by fibroblast proliferation and extracellular matrix remodeling, is the end result of various types of lung damage including interstitial pneumonia and respiratory bronchiolitis [1,2,3]
oropharyngeal aspiration (OA) of Bleomycin Led to Increased Induction of Lung Fibrosis in C57BL/6 Mice Compared to IN Administration
The volume of signals induced by repeated IN bleomycin dosing (660.25 mg/kg) as described in Babin et al [25] and detected by magnetic resonance imaging (MRI) never exceeded 120 mL, for different experimenters and studies performed in C57BL/6 mice

Summary

Introduction

Pulmonary fibrosis, characterized by fibroblast proliferation and extracellular matrix remodeling, is the end result of various types of lung damage including interstitial pneumonia and respiratory bronchiolitis [1,2,3]. A patchy alveolar wall fibrosis develops in patients with chronic obstructive pulmonary disease (COPD) whereas in chronic asthmatics, a fibrotic response occurs predominantly in the lamina reticularis, leading to thickening of the basement membrane [4,5]. In both cases the ongoing inflammation-repair cycle leads to permanent structural changes in the airway wall (remodeling) of which fibrosis is a major constituent [6,7]. The availability of this animal model of pulmonary fibrosis provides the opportunity to investigate novel pharmacological approaches aiming to treat this crippling disease

Methods

Results

Conclusion