TY - JOUR T1 - Caught in the Act: <em>In Vivo</em> Mapping of Macrophage Infiltration in Nerve Injury by Magnetic Resonance Imaging JF - The Journal of Neuroscience JO - J. Neurosci. SP - 10892 LP - 10896 DO - 10.1523/JNEUROSCI.23-34-10892.2003 VL - 23 IS - 34 AU - Martin Bendszus AU - Guido Stoll Y1 - 2003/11/26 UR - http://www.jneurosci.org/content/23/34/10892.abstract N2 - In vivo tracking of hematogenous macrophages has been a major challenge because these cells are key players in nerve injury and repair. We visualized the spatiotemporal course of macrophage infiltration after acute peripheral nerve injury in living rats by using superparamagnetic iron oxide (SPIO) particles and magnetic resonance imaging (MRI). A signal loss on MR images indicating iron accumulation was present in degenerating sciatic nerves between days 1 and 8 after a crush lesion, ceased thereafter, and corresponded to the transient presence of iron-labeled ED1-positive macrophages in tissue sections. In contrast, no SPIO accumulation was seen after optic nerve crush, which revealed microglial activation but lacked macrophage infiltration. SPIO-enhanced MRI provides a new tool to selectively visualize active periods of macrophage transmigration into the nervous system, thus enabling dynamic views on a fundamental process in a multitude of nerve disorders. ER -