Human fetal substantia nigra grafted to the dopamine-denervated striatum of immunosuppressed rats: evidence for functional reinnervation.

Human fetal substantia nigra tissue, obtained following therapeutic termination of first trimester pregnancies, was grafted to cavities overlying the striatum in ciclosporin-treated rats whose nigrostriatal dopamine system had been removed unilaterally by 6-hydroxydopamine. Tyrosine hydroxylase (TH) immunocytochemistry revealed large numbers of surviving human substantia nigra neurons that matured and formed TH-positive nerve fibers reinnervating the host rat striatum. Apomorphine-induced rotational behavior in grafted animals was reduced by 70-80% in optimal cases 3-5 months after grafting. Thus human fetal dopamine neurons can correct functional deficits in dopamine-denervated rat hosts.