Figure 2.

Partial depletion of microglia/macrophages in the early phase after MCAo impairs GPR17-expressing (GFP⁺) OPC response and exacerbates myelin damage

(A) Schematic representation of the experimental protocol exploited for early depletion of microglia/macrophages after MCAo. (B) Representative images of cells stained for Iba1, CD16/32, Ym1, GFP, and GFP/BrdU at the boundary of the ischemic lesion (0−500 μm) at day 3 post-MCAo following intranasal administration of GdCl₃ or vehicle. Arrowheads indicate cells double positive for GFP and BrdU. Scale bars, 50 μm. (C) Quantification of the density of total Iba1⁺, Iba1⁺ and CD16/32⁺, and Iba1⁺ and Ym1⁺ cells at the boundary of the ischemic lesion (0−500 μm) at day 3 post-MCAo following intranasal administration of GdCl₃ or vehicle (n = 4). Data are expressed as mean ± SE. Student’s t test. (D) Quantification of the density of GFP⁺ OPCs and of the percentage of GFP⁺ cells incorporating BrdU at the boundary of the ischemic lesion (0−500 μm) at day 3 post-MCAo following intranasal administration of GdCl₃ or vehicle (n = 4). Data are expressed as mean ± SE. Student’s t test. (E) Scatterplot representation of the linear correlation between the densities of Iba1⁺ cells (x axis) and GFP⁺ OPCs (y axis) at the boundary of the ischemic lesion (0−500 μm) at day 3 post-MCAo. Green dots correspond to GdCl₃-treated animals, whereas blue dots represent vehicle-treated animals. For correlation analysis, two-tailed Pearson test was used. (F) Representative electron micrographs showing myelinated axons in the ipsilateral corpus callosum (CC) of ischemic mice at day 3 post-MCAo following intranasal administration of GdCl₃ or vehicle and in the corresponding region of the contralateral hemisphere of vehicle-treated animals. Scale bars, 1 μm. (G) Quantification of g-ratio, myelin thickness, axon diameter, and myelinated axon density in the ipsilateral corpus callosum of ischemic mice at day 3 post-MCAo following intranasal administration of GdCl₃ or vehicle and in the corresponding region of the contralateral hemisphere of vehicle-treated animals (n = 3; 300 fibers/experimental condition have been analyzed). Data are expressed as mean ± SE. One-way ANOVA followed by Tukey’s post hoc analysis.