Magnetic resonance lipid signals in rat brain after experimental stroke correlate with neutral lipid accumulation

Proton magnetic resonance spectroscopy (MRS) signals from lipids in brain h ave been observed to increase after ischemic brain injury. However, neither the chemical identity nor the cellular location of these lipids has been e stablished. The aim of the present study was to identify the origin of MRS lipid signals in rat brain after temporary (90 min) middle cerebral artery occlusion (MCAO). Fatty acyl proton signals were detected by short-echo one and two dimensional H-1 MRS in superfused brain slices from the infarcted hemisphere 1-5 days after MCAO. The intensities of these signals were stron gly correlated with the amount of triacylglyceride and cholesterol ester in lipid extracts from the samples (r(2) = 0.96, P < 0.05) and were not corre lated with the amount of free fatty acids in the tissue. Histological stain ing of tissue revealed the presence of neutral lipid droplets in infarcted regions. Dual labeling by immunohistochemistry demonstrated that these drop lets were localized to microglia/macrophage (OX-42-labeled cells). These re sults strongly suggest that 1H MRS lipid signals from brain after stroke ar ise from microglia/macrophage phagocytosis of cellular membranes. <(c)> 200 1 Elsevier Science Ireland Ltd. All rights reserved.