Imaging of the inflammatory response in reperfusion injury after transient cerebral ischemia in rats: correlation of superparamagnetic iron oxide-enhanced magnetic resonance imaging with histopathology.
BACKGROUND
Acute inflammatory responses have been thought to play a central role in ischemia-reperfusion injury after acute ischemic stroke. Superparamagnetic iron oxide (SPIO) particles have been known to enable in-vivo monitoring of macrophage infiltration by magnetic resonance imaging (MRI) in the experimental ischemic rat brain.


OBJECTIVE
To determine whether the accumulation of macrophages could be seen in vivo in a reperfusion animal model after focal cerebral ischemia using SPIO-enhanced MRI.


METHODS
Thirty-four adult male rats were enrolled in this study. SPIO particles were injected into the rats at different time points after 1-hour transient occlusion of the middle cerebral artery, and three-dimensional (3D) T2*-weighted magnetic resonance (MR) images with a gradient-echo sequence were performed 24 hours later. Histochemical iron staining was compared with T2* signal abnormalities.


RESULTS
At days 3 and 4 post-reperfusion, focal areas of signal loss indicating local accumulation of SPIO particles appeared in a part of the damaged brain. Areas of signal loss corresponded to local accumulation of iron-laden macrophages in histologic sections, and SPIO-induced signal loss indicated active macrophage transmigration into the reperfused brain.


CONCLUSIONS
SPIO-enhanced MRI demonstrated through in-vivo monitoring that macrophages participate in reperfusion injury at early stages of injury development. SPIO-enhanced MRI could be a useful tool to examine the inflammatory mechanisms involved in reperfusion brain injury.
Department of Radiology, Yonsei University College of Medicine, Seoul, Korea.
J
J
Kim
D I
DI
Kim
S-K
SK
Lee
D J
DJ
Kim
J E
JE
Lee
S K
SK
Ahn
D000818:Animals; D001921:Brain / Q000473:pathology / Q000648:ultrastructure; D003287:Contrast Media / Q000008:administration & dosage; D004195:Disease Models, Animal; D052203:Ferrosoferric Oxide; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional; D007249:Inflammation / Q000175:diagnosis* / Q000209:etiology; D002546:Ischemic Attack, Transient / Q000150:complications / Q000175:diagnosis*; D008264:Macrophages / Q000473:pathology / Q000648:ultrastructure; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000175:diagnosis* / Q000209:etiology; D013997:Time Factors
D003287:Contrast Media; D052203:Ferrosoferric Oxide