The fate of human glial cells following transplantation in normal rodents and rodent models of neurodegenerative disease

Investigations on xenografting in the brain have previously focused on the anatomical and functional integration of the transplanted neurons. More recently, astrocytes are being implicated as having complex functions following transplantation, and are being investigated to determine their role(s) in transplantation. The present study was undertaken to investigate the migration of human astrocytes following transplantation of thalamic, striatal, and mesencephalic tissue into the rodent striatum. Human donor fetuses (9-16 weeks in gestation) obtained through elective and spontaneous abortions were utilized in this study. Following transplantation, donor astrocytes were labeled with an antiserum directed against human glial fibrillary acidic protein. Our results demonstrate that astrocytic elements from all three tissue types are capable of incorporating into the host brain, and have a tendency to follow white matter tracts (such as the corpus callosum, internal capsule, and fiber bundles in the striatum). Human astrocytes originating from the striatum and thalamus exhibited extensive migration, while migration was more limited in animals with ventral mesencephalon transplants. Ventral mesencephalon transplanted animals demonstrated positive astrocytes within the transplant, with processes (very few cell bodies) extending into white matter of adjacent host striatum. Astrocytes demonstrating immature morphology were observed with all transplant types, but were most prevalent in the striatal transplanted animals. The extent of astrocyte migration and the morphologies observed in this study reflect regional differences of the developing human brain. These results confirm and extend previous investigations on glial cell migration following transplantation in the brain.