Fetal cortical astrocytes migrate from cortical homografts throughout the host brain and over the glia limitans.

The cerebral cortices from 14-day gestation rat embryos were prelabeled with Phaseolus vulgaris leucoagglutin (PHAL) and then homografted into freshly made implantation pockets in the host cerebral cortex. Animals were sacrificed at 30 and 60 days postimplantation (DPI). Paraffin sections were double labeled for the presence of glial fibrillary acidic protein (GFAP), a specific marker for astrocytes, and PHAL, utilized as a marker for transplant-derived cells. Transplant-derived astrocytes were found on the glia limitans along the entire circumference of the brain, in the hippocampal commissure, corpus callosum, internal capsule, entopeduncular nucleus, habenular commissure, brachium of the superior colliculus, optic tract, optic chiasm, and sensory root of the trigeminal nerve. Transplanted astrocytes entered the spaces of Virchow-Robin, and migrated along parenchymal blood vessels and between the ependymal and subependymal layers of the third and lateral ventricles. The presence of basal lamina or parallel nerve fiber bundles was a common factor for these migration routes.