A Multimodal Imaging Approach Based on Micro-CT and Fluorescence Molecular Tomography for Longitudinal Assessment of Bleomycin-Induced Lung Fibrosis in Mice

Summary

We describe a non-invasive multimodal imaging approach based on Micro-CT and fluorescence molecular tomography for longitudinal assessment of the mouse lung fibrosis model induced by double intratracheal instillation of bleomycin.

Abstract

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by the progressive and irreversible destruction of lung architecture, which causes significant deterioration in lung function and subsequent death from respiratory failure.

The pathogenesis of IPF in experimental animal models has been induced by bleomycin administration. In this study, we investigate an IPF-like mouse model induced by a double intratracheal bleomycin instillation. Standard histological assessments used for studying lung fibrosis are invasive terminal procedures. The goal of this work is to monitor lung fibrosis through noninvasive imaging techniques such as Fluorescent Molecular Tomography (FMT) and Micro-CT. These two technologies validated with histology findings could represent a revolutionary functional approach for real time non-invasive monitoring of IPF disease severity and progression. The fusion of different approaches represents a step further for understanding the IPF disease, where the molecular events occurring in a pathological condition can be observed with FMT and the subsequent anatomical changes can be monitored by Micro-CT.

Introduction

Idiopathic pulmonary fibrosis (IPF) is chronic lung disease with progressive decrease of lung functions that is unfortunately often fatal within four years of diagnosis¹. The major features of IPF are extracellular matrix deposition and fibroblast proliferation, but the pathogenesis is not yet fully understood. The most supported hypothesis is that multiple cycles of lung injuries cause the destruction of alveolar epithelial cells that leads to alteration of the mesenchymal cell cycle proliferation, exaggerated accumulation of fibroblasts and myofibroblasts, and increased matrix production. Mediators involved in these processes such as matrix m....

Protocol

All animal experiments described herein were approved by the intramural animal-welfare committee for animal experimentation of Chiesi Farmaceutici and ERASMUS MC under protocol number: EMC 3349 (138-14-07) complying with the European Directive 2010/63 UE, Italian D.Lgs 26/2014 and the revised "Guide for the Care and Use of Laboratory Animals"²³.

NOTE: Prior to use, female inbred C57Bl/6 (7-8 weeks old) mice were acclimatized for at least 7 days to the local vivarium conditions (room temperature: 20-24 °C; relative humidity: 40-70%; 12-h light-dark cycle), having free access to standard rodent chow and so....

Results

Spontaneous resolution of the lung fibrosis lesions observed three weeks after single bleomycin administration and moderate structural changes highlight the limits of this model. Only preventive treatment could be performed due to the narrow therapeutic window that does not represent clinical practice¹⁷.

Here, we demonstrate that our protocol of double bleomycin intratracheal instillation is able to devel.......

Discussion

Despite many research groups focusing on developing new drugs to treat IPF, at the moment only two are available for patients. There is an urgent medical need to find more effective therapies⁷ because only lung transplantationis able to prolong survival of 4-5 years²⁶. The essential prerequisite for translational medicine and development of new drugs is the availability of an animal model that mimics the features of IPF and in which interventional studies are predictive of .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
FMT 2500 Fluorescence Tomography System	Perkin Elmer Inc.	Experimental Builder
MMPsense 680	Perkin Elmer Inc.	NEV10126	Protect from light, store the probe at 4 °C
TrueQuant software	Perkin Elmer Inc.
Female inbred C57BL/6	San Pietro NatisoneHorst, The Netherlands (UD),		Prior to use, animals were acclimatized for at least 5 days to the local vivarium conditions
Isoflurane	ESTEVE spa	571329.8	Do not inhale
Automated cell counter	Dasit XT 1800J	Experimental Builder
Saline Solution, 0.9% Sodium Chloride (NaCl)	Eurospital	15A2807
Quantum FX Micro-CT scanner	Perkin Elmer Inc.
Bleomycin sulphate from Streptomyces Verticillus	Sigma	B2434
Automatic tissue Processor	ATP700 Histo-Line Laboratories	ATP700
Embedding system	EG 1160 Leica Biosystems	EG 1160
Rotary microtome	Slee Cut 6062
Digital slide scanner	NanoZoomer S60, Hamamatsu Photonics
NIS-AR image analysis software	Nikon
Masson’s Trichrome Staining	Histo-Line Laboratories
10% neutral-buffered formalin	Sigma	HT5012-1CS
Penn-century model DP-4M Dry power insufflator	Penn-century	DPM-EXT
PE190 micro medical tubing	2biological instruments snc	BB31695-PE/8
Syringe without needle 5 mL	Terumo	SS*05SE1	Cut the boards of the piston by scissors
Hamilton 0.10 mL (model 1710)	Gastight	81022
Discofix 3-way Stopcock	Braun	4095111
Syringe with needle 1 mL	Pic solution	3,071,260,300,320	Use without needle
Plastic feeding tubes 18 ga x 50 mm	2biological instruments snc	FTP-18-50	Cut obliquely the tip