Magnetic resonance imaging of superparamagnetic iron oxide-labeled macrophage infiltrates in acute-phase renal ischemia-reperfusion mouse model

Macrophages play a key role in the initial pathogenesis of kidney ischemia-reperfusion (I-R) injury, but the mechanism of their spatial and temporal recruitment from circulation remains uncertain. This study aimed to evaluate the feasibility of magnetic resonance imaging (MRI) for detecting intravenously administered superparamagnetic iron oxide (SPIO)-labeled macrophages in an experimental renal I-R mouse model. Unilateral kidney I-R mice were imaged with a 4.7-T MRI scanner before and after administration of SPIO-labeled macrophages (RAW 264.7). On MR images, adoptive transfer of SPIO-labeled macrophages in the acute phase (1-2 days after I-R) caused a band-shaped signal-loss zone resulting from macrophage infiltrations, in the outer medullary region of injured kidneys. MRI detection of macrophages homing to an injured kidney may facilitate early detection and investigation of the pathogenesis of acute kidney injury and be a strategy for determining the treatment of acute renal failure. From the Clinical Editor: This study evaluated the feasibility of magnetic resonance imaging for detecting superparamagnetic iron oxide (SPIO)-labeled macrophages in a renal ischemia-reperfusion mouse model. Similar strategies in humans may facilitate early detection and stratification of acute kidney injury.