Chronic brain tissue remodeling after stroke in rat: A 1-year multiparametric magnetic resonance imaging study

Rats subjected to 2 h of transient middle cerebral artery occlusion were studied temporally over 1 year by magnetic resonance imaging (MRI) and behavioral testing. Multiparameter MRI measures of T-2, T-1, T-1 in the presence of off-resonance saturation of the bound proton signal (T-1sat), apparent diffusion coefficient (ADC) and susceptibility-weighted imaging (SWI) were obtained at 1 day, 1, 2, 3 and 4 weeks, and 3, 6, 9 and 12 months post-ischemia. Regions of interest included: ischemic core (damaged both at 1 day and later); new lesion (normal at 1 day, but damaged later); and recovery (damaged at 1 day, but normal later) areas. Hematoxylin and eosin, Prussian blue and ED-1, a monoclonal antibody murine macrophage marker, stainings were performed for histological assessment Core area T-2 and ADC values increased until similar to 6 months, and T-1 and T-1sat until similar to 12 months. New lesion area MRI parameter values increased until similar to 6 months (T-2, T-1 and ADC), or similar to 1 year (T-1sat). Lesion area was largest at 1 day (mean +/- SD: 37.0 +/- 13.7 mm(2)) and smallest at 1 year (18.1 +/- 10.5 mm(2)). Recovery area was largest at 3 weeks (8.9 +/- 3.8 mm(2)) and smallest at 1 year (6.4 +/- 3.3 mm(2)). The ipsilateral/contralateral ventricle area ratio was 0.7 +/- 0.2 at 1 day and increased significantly at 1 year (2.4 +/- 0.7). Iron-laden macrophages, histologically confirmed at 1 year, were detected in the lesion borders by SWI at 3, 6, 9 and 12 months. Our data indicate that MRI detectable changes of ischemia-damaged brain tissue continue for at least 1 year post-ischemia. (C) 2010 Elsevier B.V. All rights reserved.