Monitoring of impaired phagocytic function of Kupffer cells in an obstructive cholangitis rat model using superparamagnetic iron oxide MRI and contrast

Kupffer cells (KC) have an important role in the host defense in obstructive cholangitis. Non-invasive monitoring of phagocytic function of KC is pivotal. Several studies showed the possibility of non-invasive monitoring of phagocytic function of KC using superparamagnetic iron oxide-enhanced magnetic resonance imaging (SPIO-MRI) or contrast-enhanced ultrasound (CEUS). To investigate the serial change of KC function using SPIO-MRI and CEUS and whether the SPIO-MRI parameter correlates with the CEUS parameter in obstructive cholangitis rat models. With our institutional Animal Care and Use Committee approval, 19 rats (common bile duct ligation [CBDL]: n？=？9; control: n？=？10) underwent SPIO-MRI and CEUS at baseline, two, and four weeks after CBDL. The relative signal loss (RSL) of T2* value on SPIO-MRI and Kupffer phase parenchymal echogenicity (KPE) on CEUS were measured. The correlation between SPIO-MRI and CEUS parameters were compared with KC count. In CBDL group, RSL and KPE had significantly decreased (72.1% to 29.5%, 2.7 to 0.4) at four weeks compared with those in the control group (68.2% to 58.3%, 2.5 to 3.0, P？<？0.05). During the follow-up period, RSL showed significantly positive correlations with KPE (P？=？0.007). In addition, at four weeks, we found RSL was positively correlated with KPE (ρ？=？0.750, P？=？0.002). KC count was negatively correlated to RSL and KPE at four weeks (ρ？=？？0.771, P？=？0.001 and ρ？=？？0.644, P？=？0.013). SPIO-MRI and CEUS may be equally useful for monitoring the serial changes of KC phagocytic function in vivo