title: In vivo USPIO-enhanced MR signal characteristics of secondary degeneration in the ipsilateral substantia nigra after middle cerebral artery occlusion at 3T.
abstract: OBJECTIVE
  Ultrasmall superparamagnetic iron oxide (USPIO) particles to enhance MRI have been used to study neuroinflammation in vivo. Our purpose was to observe the USPIO-enhanced MR signal alterations in the primary ischemic lesion and ipsilateral substantia nigra after middle cerebral artery occlusion (MCAO) to verify the subsequent sequelae of neuroinflammation seen in the primary ischemic focus and secondary degeneration region.
  
  
  METHODS
  Sprague-Dawley rats were subjected to transient MCAO. In addition to conventional T2-, T1-weighted imaging, USPIO-enhanced MRI was performed in USPIO-injected stroke rats, while Gd-enhanced imaging was acquired in control stroke rats, on days 3, 6 using a 3-T MR scanner. The MR signal characteristics in the primary ischemic striatum, ipsilateral substantia nigra were noted, compared on histopathological H&E, Prussian blue (PB) staining.
  
  
  RESULTS
  After MCAO, USPIO-induced T2 hypointensity changes were observed in the primary ischemic region with BBB impairment at both time points. In the substantia nigra ipsilateral to the primary ischemic lesion, there was no evidence of USPIO accumulation detected by MRI and PB staining, and no BBB leakage reflected by Gd-enhanced imaging on days 3 and 6.
  
  
  CONCLUSIONS
  USPIO-enhanced MR signals have variable characteristics in both primary and remote sites after focal cerebral ischemia. This suggests that the neuroinflammatory response to brain ischemia in the primary ischemic focus and secondary degeneration region have different temporal patterns and pathophysiological mechanisms.
authors: Department of Radiology, Hua Shan hospital, Fu Dan university, 12, Wulumuqi Zhong Road, 200040 Shanghai, China. yym9876@sohu.com
authors: Yan Mei
authors: YM
authors: Yang
authors: Xiao Yuan
authors: XY
authors: Feng
authors: Le Kang
authors: le K
authors: Yin
authors: Chan Chan
authors: CC
authors: Li
authors: An Ning
authors: AN
authors: Li
authors: Jie
authors: J
authors: Jia
authors: Xiao Lou
authors: XL
authors: Wang
authors: Zun Guo
authors: ZG
authors: Du
authors: Li Xin
authors: LX
authors: Jin
mesh_terms: D000818:Animals; D020244:Infarction, Middle Cerebral Artery / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009410:Nerve Degeneration / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013378:Substantia Nigra / Q000473:pathology*
keywords: BBB; Focal cerebral ischemia; H&E; MCAO; MRI; PB; Prussian blue; ROI; SD; SN; ST; Secondary degeneration; Substantia nigra; T1-weighted imaging; T1WI; T2-weighted imaging; T2WI; USPIO; blood–brain barrier; hematoxylin and eosin; middle cerebral artery occlusion; region of interest; standard deviation; striatum; substantia nigra; ultrasmall superparamagnetic iron oxide