Journal of Neuroscience, Vol 9, 3250-3271, Copyright © 1989 by Society for Neuroscience
Intrastriatal grafts derived from fetal striatal primordia. I. Phenotypy and modular organization
AM Graybiel, FC Liu and SB Dunnett
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge 02139.
Fetal striatal grafts display a striking modularity of composition. With
acetylcholinesterase (AChE) histochemistry, the tissue of such grafts can
be divided into regions with strong AChE staining of the neuropil and
regions in which AChE staining of the neuropil is weak. In the experiments
reported here, we reexamined the nature of this modularity. Striatal grafts
were made by injecting dissociated cells of E15 ganglionic eminence into
the striatum of adult rats, which 7 days before had recived intrastriatal
deposits of ibotenic acid. Some donors had been exposed to 3H-thymidine at
E11-E15. After 9-17 month survivals, the anatomical organization of the
grafts was studied by histochemistry, immunohistochemistry, and
autoradiography. In every graft, the AChE-rich regions formed patches (P
regions) in a larger AChE-poor surround (NP regions). Neurons labeled with
3H-thymidine appeared in both P and NP regions, suggesting that donor cells
were distributed in each type of region and that neither type of tissue, P
or NP, was composed exclusively of host tissue. In the AChE-rich P regions,
markers characteristic of normal perinatal and mature rat striatum were
expressed by medium-sized cells: calcium-binding protein (calbindin D28k)
immunostaining, metenkephalin (mENK) immunostaining, and, more rarely,
somatostatin (SOM) immunostaining. In the NP regions, however, medium-sized
cells expressing calbindin and mENK immunostaining were very rare, and
there was an abundance of neuronal types not found in normal mature
striatal tissue. These included (1) large, multipolar, calbindin-positive
neurons with well-ramified, densely stained dendrites, (2) large,
SOM-positive neurons with prominent dendritic trees, and (3) mENK-positive
cells smaller than typical striatal, medium-sized, mENK-immunoreactive
neurons. In Nissl stains, the AChE-rich P regions resembled the normal
striatum of mature animals, whereas the AChE-poor NP regions did not. These
findings suggest that the P regions of fetal striatal grafts achieve a
phenotypy similar to that of normal striatum at maturity and during much of
postnatal development. The dominant expression of perikaryal calbindin-
like immunoreactivity in the P regions further suggests that these zones
have a high proportion of tissue resembling striatal matrix. By contrast,
expression of marker antigens in the NP zones of the grafts suggests that
these zones are predominantly composed of nonstriatal tissue or that they
have the phenotypy of immature striatum intermixed with some nonstriatal
cells.(ABSTRACT TRUNCATED AT 400 WORDS)