Astroglia-microvessel relationship in the developing human telencephalon.

The telencephalon of 12 and 18 week-old human foetuses was examined for evidence of astroglia-microvessel relationship. Immature astroglia cells (radial glia and astroblasts) and astrocytes were immunostained using antibodies to the cytoskeletal proteins vimentin (VIM) and glial fibrillary acidic protein (GFAP). The microvessels were detected using an antibody to the blood-brain barrier (BBB)-specific glucose transporter GLUT1. Two extracellular matrix (ECM) glycoproteins, laminin (LM), an endothelial-derived molecule, and tenascin-C (TN-C), a glia-derived molecule, were also analyzed. In the two stages examined, VIM- and GFAP-positive fibers of the radial glia establish close relationships with the radial and periventricular microvessels, which are GLUT1-positive and lined by an LM-positive basal lamina-like matrix. At the 18th week, also radial glia transitional forms and immature astrocytes exhibit extensive contacts with the microvasculature. A TN-C-rich ECM is revealed around the vascular plexus of ventricular zones at the 12th week, and around the newly growing radial microvessels and the microvessel branching sites at the 18th week. The observations taken as a whole, suggest that during the telencephalon morphogenesis the immature astroglia cells play a role in the early establishment of the distribution pattern of the neural microvessels and in their growth and maturation.