An immunohistochemical and morphometric study on astrocytes and microvasculature in the human cerebral cortex

In this study, astrocytes and microvessels of the human cerebral cortex were analysed morphometrically with the aim of acquiring quantitative information on the glio-vascular relationships, considered to be of great importance in the formation and functioning of the blood-brain barrier. Immunohistochemistry for the astrocytic marker, glial fibrillary acidic protein, was used with a computerized image analysis system. The brain tissue was embedded using the progressive lowering of temperature method, and the image analyser was applied to semithin sections subjected to immunogold-silver staining and viewed by epipolarization microscopy. The results show that, in the human cerebral cortex, astrocytes cover 11.4% of the cortex area and that their perivascular processes are nearly as extensive as the vascular bed (0.8% versus 1.72% of the cortex area). These processes form a virtually continuous sheath around the vascular walls, only 11% of the vessel perimeter lacking this astrocytic glia covering. The present results, compared with previous unpublished data obtained by conventional immunocytochemical procedures on wax sections, indicate that low-temperature methods combined with gold-silver immunolabelling on semithin sections significantly improve the detection of immunoreactivity and the performance of the image analyser.