Journal of Neuroscience, Vol 9, 614-624, Copyright © 1989 by Society for Neuroscience
Human fetal mesencephalic tissue grafted to dopamine-denervated striatum of athymic rats: light- and electron-microscopical histochemistry and in vivo chronoamperometric studies
I Stromberg, P Almqvist, M Bygdeman, TE Finger, G Gerhardt, AC Granholm, TJ Mahalik, A Seiger, L Olson and B Hoffer
Department of Histology and Neurobiology, Karolinska Institute, Stockholm, Sweden.
Human fetal mesencephalic tissue obtained from elective first-trimester
abortions was grafted to 6-hydroxydopamine-denervated striatum of athymic
(nude) rats. After 3-6 months, the transplants were evaluated by light and
electron microscopy using antibodies against tryosine hydroxylase (TH),
human specific Thy-1 (Thy-1), 5-hydroxytryptamine (5- HT), and laminin. In
vivo chronoamperometric studies of K+-induced release of electroactive
species were done prior to the histochemical evaluations. At the light
microscopical level, Thy-1-immunoreactivity was evenly distributed
throughout the entire transplants. Thy-1- immunoreactive nerve fibers were
observed radiating from the graft into the host striatum. In sections that
were double-stained with antibodies against Thy-1 and TH, such nerve fibers
contained both markers. Also 5- HT-immunoreactive cells were found in the
grafts with processes both in the grafts and radiating into host neuropil.
Laminin immunohistochemistry showed an even distribution of capillaries in
the graft with less density than in host brain, suggesting immaturity of
graft tissue. At the ultrastructural level, TH-immunoreactive axons made
symmetric contacts with unlabeled dendritic shafts and dendritic spines
within the host brain. A few asymmetric contacts with TH- immunoreactive
axons were seen. 5-HT-immunoreactive terminals made both symmetric and
asymmetric contacts with unlabeled dendritic shafts and spines. In vivo
chronoamperometry using local application of K+ revealed average signals
that were lower on the transplanted side than in control striatum. However,
close to the grafts significant amounts of the K+-evoked signal amplitudes
were as large as 1.3 microM, and the ratio of the reduction to oxidation
currents suggested release of a mixture of dopamine and 5-HT. Taken
together, this study shows that human fetal mesencephalic tissue pieces
survive grafting into nude rats, develop normal vascularization, and
express coexistence of TH- and Thy-1-immunoreactivity. Human TH- and
5-HT-immunoreactive nerve fibers form synapses in host striatum and release
monoamine neurotransmitters.