Fig. 4: Region-specific microglial activations following cardiac arrest.
Morphological analysis of microglia was performed using StainAI for: A primary somatosensory cortical layers 1-6 (L1-L6); (B) hippocampal sub-regions: cornu ammonis 1, 2, 3 (CA1, CA2, CA3), stratum oriens (SO), stratum pyramidal (SP), stratum radiatum (SR), stratum lucidum (SL), lateral molecular layer of dentate gyrus (LMOL), molecular layer of dentate gyrus (MoDG), granule cell layer of dentate gyrus (GrDG), and polymorphic layer of dentate gyrus (PoDG); (C) somatosensory thalamus: thalamic reticular nucleus (nRT) and ventral posterior medial/lateral nucleus (VPM/L). Microglial cell classes were color-coded as follows: ramified (R, green), hypertrophic (H, yellow), bushy (B, orange), ameboid (A, red), rod-shape (RD, cyan), and hypertrophic rod-shaped (HR, blue). Pie charts display the percentage of each cell class relative to total cell count within each region. In the primary somatosensory cortices of control brains, 56% of microglia were ramified, with hypertrophic and bushy cells concentrated in layers 2/3 and 5 (A). Cardiac arrest increased total microglial density and activated morphotypes, particularly bushy and ameboid cells, while hypothermia reduced activation, restoring density to control levels. In the hippocampus, microglial density was highest in LMOL and MoDG in controls (B). Following cardiac arrest, activated morphotypes increased, particularly in CA12 brains, while hypothermia mitigated this activation, as indicated by heatmaps. In thalamic sub-regions, cardiac arrest led to increased microglial activation in both nRT and VPM/L, whereas hypothermia reduced activation in VPM/L but not in nRT (C). Significant regional differences were observed in microglial activation scores. CA11: cardiac arrest for 11 min; CA12: 12 min; CA+HT: 12.5 min with hypothermia treatment, MA: microglial activation. Statistical significance is denoted as *p < 0.05 and **p < 0.01 compared to controls, and αp < 0.05 and ααp < 0.01 compared to other regions. Data are presented as mean ± standard deviation.
