Development of human fetal substantia nigra grafts in the brain of non-immunosuppressed rats.

: The survival of xenogenous tissue after transplantation to the brain of Wistar rats without immunosuppression was studied. Cell suspension was prepared from the ventral mesencephalon of human embryos 7-8 weeks of gestation, and injected either into the striatum or motor cortex of adult rats. After 1, 3, 7, 14 days and 1, 3, 6, 8 months the rats were sacrificed and the brains were processed for tyrosine hydroxylase (TH), glial fibrillary acidic protein (GFAP), ferritin immunocytochemistry and electron microscopy study. The intensity of inflammatory reaction of the host brain strongly affected the viability of grafted cells, the extend of GFAP and ferritin reactions in the tissue around the graft. Grafted human TH-positive neurons were found for 3 month survival only. After transplantation, we observed the grafted cell differentiation similar to that in normally developing mesencephalon. Six and eight months after transplantation glial cells prevailed in the grafts, while most neurons looked abnormal. An extensive bundles of myelinated fibers transpassing the intracortical transplants were seen. We are concluding that human mesencephalic cells can survive and develop in the brain of non-immunosuppressed rats.