Directing dopaminergic fiber growth along a preformed molecular pathway from embryonic ventral mesencephalon transplants in the rat brain.

To identify guidance molecules to promote long-distance growth of dopaminergic axons from transplanted embryonic ventral mesencephalon (VM) tissue, three pathways were created by expressing green fluorescent protein (GFP), glial cell line-derived neurotrophic factor (GDNF), or a combination of GDNF/GDNF receptor α1 (GFRα1) along the corpus callosum. To generate the guidance pathway, adenovirus encoding these transcripts was injected at four positions along the corpus callosum. In all groups, GDNF adenovirus was also injected on the right side 2.5 mm from the midline at the desired transplant site. Four days later, a piece of VM tissue from embryonic day 14 rats was injected at the transplant site. All rats also received daily subcutaneous injections of N-acetyl-L-cysteinamide (NACA; 100 µg per rat) as well as chondroitinase ABC at transplant site (10 U/ml, 2 µl). Two weeks after transplantation, the rats were perfused and the brains dissected out. Coronal sections were cut and immunostained with antibody to tyrosine hydroxylase (TH) to identify and count dopaminergic fibers in the corpus callosum. In GFP-expressing pathways, TH(+) fibers grew out of the transplants for a short distance in the corpus callosum. Very few TH(+) fibers grew across the midline. However, pathways expressing GDNF supported more TH(+) fiber growth across the midline into the contralateral hemisphere. Significantly greater numbers of TH(+) fibers grew across the midline in animals expressing a combination of GDNF and GFRα1 in the corpus callosum. These data suggest that expression of GDNF or a combination of GDNF and GFRα1 can support the long-distance dopaminergic fiber growth from a VM transplant, with the combination having a superior effect.

A patient with Huntington's disease and long-surviving fetal neural transplants that developed mass lesions.

Transplantation of human fetal neural tissue into adult neostriatum is an experimental therapy for Huntington's disease (HD). Here we describe a patient with HD who received ten intrastriatal human fetal neural transplants and, at one site, an autologous sural nerve co-graft. Although initially clinically stable, she developed worsening asymmetric upper motor neuron symptoms in addition to progression of HD, and ultimately died 121 months post transplantation. Eight neural transplants, up to 2.9 cm, and three ependymal cysts, up to 2.0 cm, were identified. The autologous sural nerve co-graft was found adjacent to the largest mass lesion, which, along with the ependymal cyst, exhibited pronounced mass effect on the internal capsules bilaterally. Grafts were composed of neurons and glia embedded in disorganized neuropil; robust Y chromosome labeling was present in a subset of grafts and cysts. The graft-host border was discrete, and there was no evidence of graft rejection or HD pathologic changes within donor neurons. This report, for the first time, highlights the potential for graft overgrowth in a patient receiving fetal neural transplantation.

The role of positron emission tomography in the assessment of human neurotransplantation.

Positron emission tomography (PET) using tracers of the dopaminergic system has been used to measure striatal function in a small number of parkinsonian patients undergoing neurotransplantation procedures. Some postoperative scans have shown an unequivocal increase in presynaptic dopaminergic function at the graft site, providing evidence of graft survival independent of clinical assessment. Combined PET and magnetic resonance imaging (MRI) images provide the facility to explore the relationship between graft placement, survival and clinical efficacy.

Migratory pattern of fetal rat brain cells and human glioma cells in the adult rat brain.

The migratory behavior of two human glioma cell lines (D-54MG and GaMG) and fetal rat brain cells grafted into the adult rat brain was studied. To trace the implanted cells, they were stained with the carbocyanine vital dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate before injecting them into the white matter above the corpus callosum. The animals were sacrificed 2 h and 7 and 21 days after injection, and the brains were removed and cryosectioned. Fluorescence microscopy showed that both the 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate-stained fetal and tumor cells had the same migratory pattern. Implanted cells were found along myelinated fibers in the corpus callosum and in the perivascular space. After immunostaining for several extracellular matrix (ECM) components (laminin, fibronectin, collagen type IV, and chondroitin sulfate), laminin deposits were observed in the border zone between the host tissue and implanted tumor cells as well as fetal cells. By using two different types of antibodies against fibronectin, it is shown that the fibronectin expression observed in the tumor matrix may be host derived. This was further supported by the fact that tumor spheroids obtained from the two glioma cell lines were negative when immunostained for these ECM components. Several of the ECM components may be host derived. This can be caused by neovascularization and repair synthesis or by a local production of guiding substrates which are important for tumor cell locomotion. The present data suggest that the migratory patterns of fetal and glioma cells are indistinguishable when transplanted into the adult rat brain. Thus, glioma cells may be routed by the same ECM components that play a major role during brain development.

Angiogenic activity of the K-fgf/hst oncogene in neural transplants.

Using retrovirus-mediated gene transfer into neural transplants, we have expressed the human K-fgf/hst oncogene in the central nervous system. Single-cell suspensions of fetal rat brains were removed at embryonic days 13 and 14, exposed to a retroviral vector encoding the K-fgf oncogene and stereotaxically implanted into the caudate putamen of syngenic adult Fisher rats. Recipient animals were sacrificed at intervals of 6-16 months without evidence of neurological impairment. Mock-infected grafts showed the characteristic histopathological appearance of organotypically differentiated neural transplants. In contrast, grafts exposed to the K-fgf gene exhibited abundant capillary proliferation and capillary angiomas. By in situ hybridization analysis and immunohistochemistry, expression of K-fgf was detected in neural cells adjacent to vascular proliferations. Neurons and glia with abundant K-fgf transcripts were morphologically unaffected. In order to examine the transforming potential of the K-fgf gene in the nervous system, we combined retrovirus-mediated transfer of the K-fgf oncogene with a single transplacental exposure of the donor animals to the neurotropic carcinogen N-ethyl-N-nitrosourea (NEU). However, this combination of transforming agents did not result in tumor formation in the grafts. These results provide evidence for a powerful angiogenic effect of K-fgf on the developing brain in vivo.

Identification of the end stage of scrapie using infected neural grafts.

Although the formal pathogenesis of spongiform encephalopathies has been described in detail, it is not known whether the infectious agent targets primarily neurons, glial cells, or both. To address this question, we have transplanted transgenic embryonic neural tissue overexpressing PrP(c) into the forebrain of Prnp -knockout mice, and infected it with scrapie prions. After infection, grafts developed severe spongiform encephalopathy. As the infected hosts were not clinically affected, we were able to prolong the experiment and to assess changes in the graft over periods of time, which vastly exceeded the normal life span of scrapie-infected mice. Sequential contrast-enhanced magnetic resonance imaging (MRI) revealed progressive impairment of blood-brain barrier properties in infected grafts. However, loss of astrocytes was not observed. Subtotal neuronal loss occurred during the progression of the disease in the grafts, reactive astrocytes persisted until the terminal stage of disease. We conclude that scrapie encephalopathy primarily leads to neuronal death, while degeneration of astrocytes does not occur. Functional impairment of the blood-brain barrier suggests involvement of astrocytes and endothelial cells in the pathological process.

Restoration of thalamostriatal projections in rat neostriatal grafts: an electron microscopic analysis.

The thalamostriatal projections to rat neostriatal grafts were studied by using the Phaseolus vulgaris-leucoagglutinin (PHA-L) axonal tracing technique. Two to 6 months after implantation of striatal primordia into adult neostriata, PHA-L was injected into two different portions of the intralaminar nuclear complex of the thalamus. In the host neostriatum, labeled fibers from the parafascicular nucleus (PF) arborized in a large region in the neostriatum, but avoided small patchlike areas. Most of the fibers from PF had irregular curved trajectories with short side branches that formed boutons. Labeled fibers from the centromedial and paracentral nuclei (CeM-PC) projected to a similarly large area within the neostriatum but did not show any nonuniformity. CeM-PC axons had relatively straight trajectories and formed boutons en passant. Both sets of thalamostriatal projection fibers were found in the grafts. Some of the labeled fibers in the grafts formed dense, focal arborizations. Compared to the host neostriatum, the distribution of postsynaptic elements in the grafts was altered dramatically. In the host neostriatum, 89% of the terminals from PF terminated onto dendritic shafts; 93% of the CeM-PC terminals contacted dendritic spines. However, only 47% of the PF terminals in the grafts contacted dendritic shafts; 53% of them terminated on dendritic spines. In grafts, 81% of the terminals from CeM-PC region contacted dendritic spines; 19% of them made synapses on dendritic shafts. The shift of postsynaptic elements in the grafts suggests a loss of pathway specificity in the induction of dendritic spines on neostriatal neurons in grafts.

Survival and proliferation of nonneural tissues, with obstruction of cerebral ventricles, in a parkinsonian patient treated with fetal allografts.

BACKGROUND: Since 1985, treatment of idiopathic Parkinson's disease (PD) by surgical transfer of adult or fetal chromaffin tissue or of fetal central neural tissue to the brains of afflicted patients has been attempted, with variable clinical results. Neuropathologic studies of the status of these transplants are few and show wide variation in degree of graft survival. METHODS: We report the case of a 52-year-old man, who, 23 months earlier, received both intrastriatal implantation and intraventricular infusion of tissues derived from fetuses of 15 to 16 weeks and 5 to 6 weeks gestational age. Clinical improvement, as measured by increased amounts of "on" time with reduced levodopa requirements, seemed to occur over the subsequent months. He died suddenly at home after a several-hours interval of progressive lethargy and breathing difficulties. RESULTS: At autopsy, the diagnosis of PD was confirmed. Intrastriatal graft sites were identified, but contained no viable neurons; astrogliosis, focal microgliosis, and mixed inflammatory response, suggesting allograft rejection, were present. Surprisingly, the intraventricular tissues survived and showed ectodermal and mesenchymal, but no neural, differentiation, as well as cellular response; the left lateral and fourth ventricles were filled completely by this proliferated tissue. CONCLUSIONS: By intraventricular infusion, tissues from early-gestation sources can engraft successfully, grow, and survive for at least 23 months in the brain of a PD patient. However, contamination by, or differentiation into, nonneural tissues can occur, can lead to proliferation of tissues within ventricular spaces, and may result in ventricular obstruction. Grafts, whether intraventricular or intraparenchymal, are capable of inciting host responses, which in turn may limit their long-term survival. Finally, post-transplant clinical improvement in symptoms of PD may be unrelated to survival of engrafted neurons.

Xenotransplantation for brain repair: reduction of porcine donor tissue immunogenicity by treatment with anti-Gal antibodies and complement.

BACKGROUND: Transplantation of embryonic neural tissue is a potential treatment for Parkinson's disease. Because human donor material is in short supply, porcine xenografts are considered a useful alternative. Current immunosuppressive therapies fail, however, to protect intracerebral neural xenografts from host CD4 T lymphocytes. To reduce the immunogenicity of porcine donor tissue, we attempted to remove microglial cells with antibodies against the alpha-galactosyl epitope (Galalpha1,3Galbeta1,4GlcNAc-R), or anti-Gal, and complement, and studied whether this pretreatment can reduce direct and indirect T-cell responses to the tissue. METHODS: Brain tissue from 27-day-old pig embryos was dissociated and treated with human anti-Gal and rabbit complement. The microglial content was analyzed by flow cytometry. [3H]thymidine incorporation in cocultures of the brain cells and purified human CD4 T cells was used to determine direct T-cell responses. Indirect T-cell responses were studied by grafting pretreated and control-pretreated (no anti-Gal) nigral tissue into the lesioned striatum of immunocompetent rats with 6-hydroxydopamine-induced hemiparkinsonism. Amphetamine-induced circling behavior was used to measure graft function. RESULTS: Anti-Gal and complement reduced the microglial content to 11-24% of control and abolished the ability of the brain cells to induce human CD4 T-cell proliferation. Pretreated nigral tissue reduced hemiparkinsonism by more than 50% in five of eight rats at some point during the 10-week follow-up. Rats receiving control-pretreated nigral tissue did not display this degree of improvement. CONCLUSIONS: Pretreatment with anti-Gal and complement can reduce the immunogenicity of porcine neural tissue, and might, therefore, be a valuable alternative or supplement to immunosuppression in neural xenotransplantation.

Immunoelectron microscopic analysis of the synaptic connectivity of serotoninergic neurons grafted to the 5,7-dihydroxytryptamine-lesioned rat spinal cord.

The connections between the host and 5-hydroxytryptamine-containing neurons grafted to the spinal cord have been analysed using electron microscopic immunohistochemistry. Adult rats with 5,7-dihydroxytryptamine lesions of the brain and spinal cord received implants of embryonic medullary raphé neurons at three sites in the spinal cord. Eight to 10 months after grafting, the transplanted 5-hydroxytryptamine-positive neurons had formed extensive and complex contacts with spines, dendrites, perikarya and vesicle-containing structures in both the dorsal and ventral horns. Reinnervation of laminae IV-VI was less rich. In the graft itself, connections were also made between non-immunoreactive varicosities and 5-hydroxytryptamine-containing dendrites, and somata, but the exact origin of the afferents was not determined. Outside the implant site, no obvious synaptic junctions onto grafted 5-hydroxytryptamine-immunoreactive boutons were obvious, although labelled and unlabelled varicosities were often in close apposition. Synaptic junctions in the dorsal horn were predominantly symmetric, with the presynaptic varicosity containing mostly small agranular vesicles. By contrast, in the ventral horn most junctions were asymmetric, while the presynaptic element contained both small agranular and large dense-core vesicles. The results demonstrate that the types of synaptic contacts formed between the grafted 5-hydroxytryptamine neurons and the host spinal cord are remarkably similar to those found in intact spinal cord. In addition, the division of morphological differences that exists between 5-hydroxytryptamine-containing boutons in the normal dorsal vs ventral horns is also apparent in the transplanted animals. Finally, there appear to be present several anatomical substrates for the regulation by the host of 5-hydroxytryptamine output from the grafted neurons.

Intrastriatal grafts derived from fetal striatal primordia--IV. Host and donor neurons are not intermixed.

Embryonic striatal grafts transplanted into excitotoxin-damaged host striatum develop a heterogeneous structure in which some regions resemble striatum but others do not. In the experiments reported here, we tested for the possibility that the regions resembling striatum were actually derived from host neurons that migrated into the grafts, rather than being derived from donor cells. We placed embryonic striatal grafts into host brains in which striatal cells had been multiply pulse-labeled with [3H]thymidine. Four groups of host rats were exposed to [3H]thymidine at embryonic days 12 and 13-15, 15-18, 16-19, or 20 to postnatal day 1, and were allowed to reach maturity. One week prior to grafting, lesions of the caudoputamen were made unilaterally in each host rat by injecting ibotenic acid. At grafting, dissociated cells from embryonic days 14-16 rat striatal primordia were injected bilaterally into the host caudoputamen. The locations of [3H]thymidine-labeled neurons were analysed by autoradiography eight to 16.5 months post-grafting. Despite the presence of many intensely labeled neurons in the host striatum of rats in all four groups, intensely labeled neurons were rarely found in the cores of grafts. A few weakly labeled small cells appeared in the graft cores, and occasional strongly or weakly labeled medium-sized cells appeared at the margins of the graft zones. Some perivascular cells associated with blood vessels in the grafts were also weakly labeled, but the gliotic tissue surrounding the graft zones was not labeled. These results suggest that very few host striatal neurons migrate into the cores of intrastriatal grafts, or that, if they do, such neurons return to the host striatum or do not survive. At most, surviving host striatal neurons have limited spatial interactions with donor cells at the margins of the grafts, both in the damaged and in the intact host striatal environment. These observations, combined with our previous finding that [3H]thymidine-labeled cells derived from embryonic day 15 striatal primordia do not appear in the host striatum, indicate that no extensive mutual migrations of striatal donor neurons and host neurons occur in the zones of grafting.

Chronic gliosis triggers Alzheimer's disease-like processing of amyloid precursor protein.

Alzheimer's disease is a progressively dementing illness characterized by the extracellular accumulation and deposition of beta-amyloid. Early onset Alzheimer's disease is linked to mutations in three genes, all of which lead to increased beta-amyloid production. Inflammatory changes and gliosis may also play a role in the disease process, but the importance of these reactive events remains unclear. We recently reported that chronic cortical gliosis in heterotopic fetal rat cortical transplants is associated with significant changes in the levels of some of the proteins implicated in the pathogenesis of Alzheimer's disease. Because rodent beta-amyloid does not form extracellular amyloid deposits, we have now extended this model of chronic cortical gliosis to transgenic mice expressing the Swedish mutant form of human amyloid precursor protein. In addition, apolipoprotein E knockout mice were used to elucidate the role of this protein in reactive gliosis. The expression of mutant and murine proteins was assayed 6 or 10 months after transplantation using immunohistochemical and western blot methods. Heterotopic transplantation of fetal cortex onto the midbrain of neonatal mice consistently resulted in reactive gliosis, independent of apolipoprotein E status. In contrast, in homotopic cortex-to-cortex grafts there was little alteration in glial reactivity, a result similar to that obtained previously in rats. By 10 months post-transplantation the level of presenilin-1 expression was lower in heterotopic grafts than in host cortex and there was increased expression of transgenic amyloid precursor protein, but only in the gliotic cortex-to-midbrain grafts. Most importantly, increased levels of beta-amyloid, and particularly its precursor, C-99, were selectively found in these heterotopic transplants. Our results show that chronic gliosis is associated with altered processing of the amyloid precursor protein in vivo and thus may initiate or exacerbate pathological changes associated with Alzheimer's disease.

Glial cell line-derived neurotrophic factor increases survival, growth and function of intrastriatal fetal nigral dopaminergic grafts.

The ability of transplants of fetal nigral neurons to reverse symptoms in patients with Parkinson's disease is, at least in part, limited by the poor survival of the grafted dopaminergic neurons and the restricted host reinnervation from the graft. Here, we report that glial cell line-derived neurotrophic factor, a novel trophic factor for developing dopaminergic neurons, can increase survival and fibre outgrowth of fetal nigral dopaminergic neurons, and stimulate graft-induced functional recovery after transplantation in a rat model of Parkinson's disease. Injections of rat glial cell line-derived neurotrophic factor adjacent to the graft enhanced graft function, resulting in complete compensation of amphetamine-induced turning behaviour already by two weeks postgrafting as opposed to four weeks in the control group. The total number of surviving tyrosine hydroxylase-positive neurons was about two-fold greater in the glial cell line-derived neurotrophic factor-treated animals compared to the vehicle-injected controls, and the density of tyrosine hydroxylase-positive fibres was found to be increased both in the host striatum (from 37.6 +/- 8.3% to 105.5 +/- 9.7% of intact striatum) as well as inside the graft (55% increase). Moreover, in animals treated with glial cell line-derived neurotrophic factor, the outgrowth of tyrosine hydroxylase-positive fibres was mostly directed towards the injection site. These findings show that supply of exogenous glial cell line-derived neurotrophic factor to the transplantation site improves survival, growth and function of transplanted fetal nigral dopaminergic neurons in the rat Parkinson model.

Glutamic acid decarboxylase gene expression in thalamic reticular neurons transplanted as a cell suspension in the adult thalamus.

The goal of the present study was to determine whether alterations in neuronal morphology and connections in thalamic grafts were accompanied by changes in the expression of mRNA encoding glutamic acid decarboxylase (GAD), the key enzyme in the synthesis of GABA, the normal neurotransmitter of neurons of the thalamic reticular nucleus. Cell suspensions of rat fetal tissue containing both thalamic reticular nucleus and ventrobasal primordia were transplanted into the excitotoxically lesioned somatosensory thalamus of adult rats. Levels of messenger RNA (mRNA) encoding GAD (Mr 67,000; GAD67) were measured 7 days to 4 months following transplantation via quantitative in situ hybridization with 35S-radiolabeled antisense RNAs. Expression of GAD67 mRNA in the thalamic reticular nucleus was analyzed in parallel in rat pups between 0 and 30 days postnatally, and in adult animals. As already observed with immunohistochemistry, transplanted neurons of the thalamic reticular nucleus did not group in specific clusters but rather mingled with unlabeled (putatively ventrobasal) neurons. Levels of labelling for GAD67 mRNA per neuron increased over time and reached adult levels during the third week post-grafting, i.e. 2 weeks after the theoretical birthdate of the neurons (grafted at embryonic days 15-16). Similar values were observed and a plateau was reached at similar time points during normal ontogeny. The results suggest that, in contrast to morphology and size of the neuronal cell bodies, gene expression of GAD67 develops normally despite the ectopic location of neurons of the thalamic reticular nucleus in the somatosensory thalamus, the abnormal connectivity and the lack of segregation from non-GABAergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuronal development in embryonic brain tissue derived from schizophrenic women and grafted to animal hosts.

The distribution of schizophrenia in families supports the hypothesis of heritable risk factors in schizophrenia, but there is as yet no identification of an inherited neurobiological defect. Human embryonic brain tissue fragments, derived from first trimester abortions, can be transplanted into rat hosts, where they continue neuronal development and are accessible for neurobiological investigation. Hippocampal transplants derived from three schizophrenic women and a larger series of normal women have been studied. If there are heritable neuronal defects associated with schizophrenia, a proportion of the transplants from schizophrenic women would be expected to carry these defects. The transplants from the first two schizophrenic women showed profound abnormalities in survival and growth, compared to the series of transplants from normal women. The transplants from the third schizophrenic woman showed normal growth and development, as well as typical histological and electrophysiological features. The data must be regarded as preliminary, because of the small number of subjects that have been studied. However, they are consistent with the transmission of a defect in neuronal development to some of the offspring of schizophrenic women, a possibility consistent with other studies of the pathogenesis of schizophrenia. The mechanism of the defect in development remains to be identified.

Allografts of CNS tissue possess a blood-brain barrier: III. Neuropathological, methodological, and immunological considerations.

Development of a blood-brain barrier (BBB) within mammalian CNS grafts, placed either intracerebrally or peripherally, has been controversial. Published data from this laboratory have emphasized the presence or the absence of a BBB within solid mammalian tissue or cell suspension grafts is determined intrinsically by the graft and not by the surrounding host parenchyma (e.g., brain, kidney, testis, etc.). Nevertheless, correctly interpreting whether or not a BBB exists within brain grafts is manifested by methodologies employed to answer the question and by ensuing neuropathological and immunological consequences of intracerebral grafting. The present study addresses these issues and suggests misinterpretation for the absence of a BBB in brain grafts can be attributed to: (1) rupture of interendothelial tight junctional complexes in vessels of CNS grafts fixed by perfusion of the host; (2) damage to host vessels and BBB during the intracerebral grafting procedure; (3) graft placement in proximity to inherently permeable vessels (e.g., CNS sites lying outside the BBB) supplying the subarachnoid space/pial surface and circumventricular organs such as the median eminence, area postrema, and choroid plexus; and (4) graft rejection associated with antigen presenting cells and the host immune response. The latter is prevalent in xenogeneic grafts and exists in allogeneic grafts with donor-host mismatch in the major and/or minor histocompatibility complex. CNS grafts between non-immunosuppressed outbred donor and host rats of the same strain (e.g., Sprague Dawley or Wistar rats) can be rejected by the host; these grafts exhibit populations of immunohistochemically identifiable major histocompatibility complex class I+ and class EE+ cells (microglia, macrophages, etc.) and CD4+ T-helper and CD8+ T-cytotoxic lymphocytes. PC12 cell suspension grafts placed within the CNS of non-immunosuppressed Sprague Dawley rats are rejected similarly. Donor cells from solid CNS grafts placed intracerebrally and stained immunohistochemically for donor major histocompatibility complex (MHC) class I expression are identified within the host spleen and lymph nodes; these donor MHC expressing cells may initiate the host immune response subsequent to the cells entering the general circulation through host cerebral vessels damaged during graft placement. Rapid healing of damaged cerebral vessels is stimulated with exogenously applied basic fibroblast growth factor, which may prove helpful in reducing the potential entry of donor cells to the host circulation. These results have implication clinically for the intracerebral grafting of human fetal CNS cell suspensions.

Ultrastructural neuropathology in murine trisomy 16 hippocampal grafts.

Trisomy 21, Down syndrome individuals demonstrate Alzheimer's disease-associated neuropathology at post mortem. The amyloid precursor protein, one of the pathological proteins is encoded for on chromosome 21. Mouse chromosome 16 is syntenic to human chromosome 21 for the region spanning the amyloid gene. We have previously reported the appearance of Alzheimer's disease-associated neuropathological proteins in cortical grafts derived from Trisomy 16 mice at 4-6 months survival. This paper reports the ultrastructural observations of large and multiple deposits of intracellular lipofuscin within these trisomic grafts at 12 months survival along with increased numbers of free ribosomes, extended Golgi apparatus and endoplasmic reticulum, membrane degeneration and abnormal axonal profiles. Similar but less severe neuro-degeneration is occasionally observed within 18-month-old normal, mouse hippocampal tissue and rarely observed in age-matched control grafts.

Long distance transplant-to-host axon elongation without target deafferentation.

To confirm the entire course of the long distance transplant-to-host axon elongation, the Thy-1 mouse allelic system was used for marking the olfactory bulb (OB) transplant. Axons from OB transplanted into the lateral ventricle and adjacent areas extended for a long distance, through three routes, to the frontal cortical surface, to the olfactory tubercle, the primary olfactory cortex and OB. Because of the OB graft insertion from the dorsal aspect through the neocortex, the host olfactory system remained unaffected. These results demonstrated that the transplanted OB could express its intrinsic ability of the long distance axon elongation without target deafferentation and even if the OB is inserted in the rather mature host.

MK-801 does not enhance dopaminergic cell survival in embryonic nigral grafts.

Two groups of hemiparkinsonian rats received grafts of embryonic ventral mesencephalon with or without the addition of the NMDA receptor antagonist (+)dizocilpine hydrogen maleate (MK-801). When added to the cell suspension, a 10 microM concentration of MK-801 did not enhance the survival of tyrosine hydroxylase positive neurones in the grafts. These findings suggest that cell death occurring during nigral transplantation is not primarily due to excitotoxicity.

Bilateral fetal striatal grafts in the 3-nitropropionic acid-induced hypoactive model of Huntington's disease.

We investigated the 3-nitropropionic acid (3-NP)-induced hypoactive model of Huntington's disease (HD) to demonstrate whether fetal tissue transplantation can ameliorate behavioral deficits associated with a more advanced stage of HD. Twelve-week-old Sprague-Dawley rats were introduced to the 3-NP dosing regimen (10 mg/kg, i.p., once every 4 days for 28 consecutive days), and were then tested for general spontaneous locomotor activity in the Digiscan locomotor apparatus. All rats displayed significant hypoactivity compared to their pre-3-NP injection locomotor activity. Randomly selected rats then received bilateral intrastriatal solid grafts of fetal striatal (lateral ganglionic eminence, LGE) tissues from embryonic day 14 rat fetuses. Approximately 1/3 of each LGE in hibernation medium was infused into each lesioned host striatum. In control rats, medium alone was infused intrastriatally. A 3-mo posttransplant maturation period was allowed prior to locomotor activity testing. Animals receiving fetal LGE grafts exhibited a significant increase in locomotor activity compared to their post-3-NP injection activity or to the controls' posttransplant activity. Surviving striatal grafts were noted in functionally recovered animals. This observation supports the use of fetal striatal transplants to correct the akinetic stage of HD. To the best of our knowledge, this is the first study that has investigated the effects of fetal striatal transplantation in a hypoactive model of HD.