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 tumo urs have been examined by means of light microscopy and conventional transm ission electron microscopy. The cortical biopsies of frontal, parietal and temporal cortex were examined to analyse the heterogeneous astrocytic respo nse and characterize astrocytic population subtypes. Swollen clear and dens e astrocytes, glycogen rich- and glycogen- depleted astrocytes, aged or lip ofucsin rich-astrocytes and reactive, dark, hypertrophic astrocytes were id entified. Clear and dense astrocytes displayed bundles of glial filaments a nd dense inclusion bodies. Glycogen-rich astrocytes exhibited an accumulati on of beta type of monogranular glycogen granules, which disappear in the g lycogen-depleted astrocytes, suggesting anoxic mobilization of glycogen sto res during ischemia or anoxia. Lipofucsin rich astrocytes were mainly relat ed with ageing processes, although their presence in young patients suggest s also an injured related process. Dark astrocytes with phagocytic properti es were found. They exhibited bundles of glial filaments. The astrocytic re sponse depended upon the nature of cortical insult, extent of damage, time course of pathological lesion and affected cortical region.