Astrocyte subtypes in the gray matter of injured human cerebral cortex: a transmission electron microscope study

Astrocytic subtypes in different cortical regions of injured human cerebral cortex of 22 patients with brain trauma, vascular anomalies and brain tumours have been examined by means of light microscopy and conventional transmission electron microscopy. The cortical biopsies of frontal, parietal and temporal cortex were examined to analyse the heterogeneous astrocytic response and characterize astrocytic population subtypes. Swollen clear and dense astrocytes, glycogen rich- and glycogen-depleted astrocytes, aged or lipofucsin rich-astrocytes and reactive, dark, hypertrophic astrocytes were identified. Clear and dense astrocytes displayed bundles of glial filaments and dense inclusion bodies. Glycogen-rich astrocytes exhibited an accumulation of beta type of monogranular glycogen granules, which disappear in the glycogen-depleted astrocytes, suggesting anoxic mobilization of glycogen stores during ischemia or anoxia. Lipofucsin rich astrocytes were mainly related with ageing processes, although their presence in young patients suggests also an injured related process. Dark astrocytes with phagocytic properties were found. They exhibited bundles of glial filaments. The astrocytic response depended upon the nature of cortical insult, extent of damage, time course of pathological lesion and affected cortical region.