Extracellular matrix and the blood-brain barrier in glioblastoma multiforme: spatial segregation of tenascin and agrin.

The quality of the blood-brain barrier (BBB), represented mainly by endothelial tight junctions (TJ), is now believed to be dependent on the brain microenvironment and influenced by the basal lamina of the microvessels. In the highly vascularized glioblastoma multiforme (GBM), a dramatic increase in the permeability of blood vessels is observed but the nature of basal lamina involvement remains to be determined. Agrin, a heparan sulfate proteoglycan, is a component of the basal lamina of BBB microvessels, and growing evidence suggests that it may be important for the maintenance of the BBB.