In Vivo MRI Assessment of Hepatic and Splenic Disease in a Murine Model of Schistosmiasis

BACKGROUND: Schistosomiasis (or bilharzia), a major parasitic disease, affects more than 260 million people worldwide. In chronic cases of intestinal schistosomiasis caused by trematodes of the Schistosoma genus, hepatic fibrosis develops as a host immune response to the helminth eggs, followed by potentially lethal portal hypertension. In this study, we characterized hepatic and splenic features of a murine model of intestinal schistosomiasis using in vivo magnetic resonance imaging (MRI) and evaluated the transverse relaxation time T(2) as a non-invasive imaging biomarker for monitoring hepatic fibrogenesis. METHODOLOGY/PRINCIPAL FINDINGS: CBA/J mice were imaged at 11.75T two, six and ten weeks after percutaneous infection with Schistosoma mansoni. In vivo imaging studies were completed with histology at the last two time points. Anatomical MRI allowed detection of typical manifestations of the intestinal disease such as significant hepato- and splenomegaly, and dilation of the portal vein as early as six weeks, with further aggravation at 10 weeks after infection. Liver multifocal lesions observed by MRI in infected animals at 10 weeks post infection corresponded to granulomatous inflammation and intergranulomatous fibrosis with METAVIR scores up to A2F2. While most healthy hepatic tissue showed T(2) values below 14 ms, these lesions were characterized by a T(2) greater than 16 ms. The area fraction of increased T(2) correlated (r(S) = 0.83) with the area fraction of Sirius Red stained collagen in histological sections. A continuous liver T(2)* decrease was also measured while brown pigments in macrophages were detected at histology. These findings suggest accumulation of hematin in infected livers. CONCLUSIONS/SIGNIFICANCE: Our multiparametric MRI approach confirms that this murine model replicates hepatic and splenic manifestations of human intestinal schistosomiasis. Quantitative T(2) mapping proved sensitive to assess liver fibrogenesis non-invasively and may therefore constitute an objective imaging biomarker for treatment monitoring in diseases involving hepatic fibrosis.