ABSTRACT
Magnetic resonance imaging (MRI) has been used to follow the course of bleomycin-induced lung injury in mice and to investigate two knockout mouse lines with the aim of providing potential therapeutic targets. Bleomycin (0.25 mg/kg) was administered intranasally six times, once a day. MRI was carried out on spontaneously breathing animals up to day 70 after bleomycin. Neither cardiac nor respiratory gating was applied during image acquisition. A long lasting response following bleomycin has been detected by MRI in the lungs of male C57BL/6 mice. Histology showed that, from day 14-70 after bleomycin, fibrosis was the predominant component of the injury. Female C57BL/6 mice displayed a smaller response than males. Bleomycin-induced injury was significantly more pronounced in C57BL/6 than in Balb/C mice. MRI and histology demonstrated a protection against bleomycin insult in female heterozygous and male homozygous cancer Osaka thyroid kinase knockout animals. In contrast, no protection was seen in cadherin-11 knockout animals. In summary, MRI can quantify, in spontaneously breathing mice, bleomycin-induced lung injury. With the ability for repetitive measurements in the same animal, the technique is attractive for in vivo target analysis and compound profiling in this murine model.
Subject(s)
Antibiotics, Antineoplastic/toxicity , Bleomycin/toxicity , Image Enhancement , Image Processing, Computer-Assisted , Lung/drug effects , Magnetic Resonance Imaging , Pulmonary Fibrosis/chemically induced , Administration, Intranasal , Alleles , Animals , Cadherins/genetics , Dose-Response Relationship, Drug , Female , Genetic Carrier Screening , Genetic Predisposition to Disease , Lung/pathology , MAP Kinase Kinase Kinases/genetics , Male , Mice , Mice, Inbred BALB C , Mice, Knockout , Proto-Oncogene Proteins/genetics , Pulmonary Fibrosis/genetics , Pulmonary Fibrosis/pathology , Sex FactorsABSTRACT
PURPOSE: To demonstrate the feasibility of proton MRI to noninvasively quantify bleomycin-induced injury and the effects of glucocorticosteroids in a rat model of lung fibrosis. MATERIALS AND METHODS: Sprague-Dawley rats received bleomycin intra-tracheally and underwent MRI up to day 70 following injury onset. A subgroup of animals was treated with budesonide. RESULTS: The response in the first 2 weeks post-bleomycin, characterized by diffuse MRI signals, was related primarily to inflammation as confirmed by histology. Later, increased signals reflected principally tissue remodeling involved in fibrosis development, as suggested by histological analysis revealing collagen deposition in the same areas where MRI signals had been detected. Budesonide administration at days 6 and 13 after bleomycin resulted in decreased MRI signals 24 h after each corticosteroid application. However, no complete signal resolution was observed. Histology showed that budesonide affected inflammation but not fibrosis. CONCLUSION: The ability of MRI to noninvasively quantify lung injury in bleomycin-treated rats will facilitate in vivo pharmacological studies in this model of pulmonary fibrosis. Repetitive measurements open new avenues in testing compounds as the responses at several time points during the course of treatment can be easily compared. Specifically, studies at the chronic phase, when fibrosis is already established, become amenable.
