Motor associations of iron accumulation in deep grey matter nuclei in Parkinson's disease: a cross-sectional study of iron-related magnetic resonance imaging susceptibility.

BACKGROUND AND PURPOSE: To determine whether iron deposition in deep brain nuclei assessed using high-pass filtered phase imaging plays a role in motor disease severity in Parkinson's disease (PD). METHODS: Seventy patients with mild to moderate PD and 20 age- and gender-matched healthy volunteers (HVs) underwent susceptibility-weighted imaging on a 3 T magnetic resonance imaging scanner. Phase shifts (radians) in deep brain nuclei were derived from high-pass filtered phase images and compared between groups. Analysis of clinical laterality and correlations with motor severity (Unified Parkinson's Disease Rating Scale, Part III, UPDRS-III) were performed. Phase shifts (in radians) were compared between HVs and three PD subgroups divided according to UPDRS-III scores using analysis of covariance, adjusting for age and regional area. RESULTS: Parkinson's disease patients had significantly (P < 0.001) higher radians than HVs bilaterally in the putamen, globus pallidus and substantia nigra (SN). The SN contralateral to the most affected side showed higher radians (P < 0.001) compared to the less affected side. SN radians positively correlated with UPDRS-III and bradykinesia-rigidity subscores, but not with tremor subscores. ancova followed by post hoc Bonferroni-adjusted pairwise comparisons revealed that SN radians were significantly greater in the PD subgroup with higher UPDRS-III scores compared to both lowest UPDRS-III PD and HV groups (P < 0.001). CONCLUSIONS: Increased nigral iron accumulation in PD appears to be stratified according to disease motor severity and correlates with symptoms related to dopaminergic neurodegeneration. This semi-quantitative in vivo iron assessment could prove useful for objectively monitoring PD progression, especially in clinical trials concerning iron chelation therapies.

Memantine and reduced time with dyskinesia in Parkinson's Disease.

OBJECTIVES: The partial glutamate antagonist amantadine is currently used in clinical practice, to reduce dyskinesia developing as a side-effect of levodopa treatment in patients suffering from Parkinson's disease (PD). This study was aimed at evaluating the antidyskinetic effect of another glutamate antagonist, memantine. METHODS AND MATERIALS: We performed a randomized, double-blind and placebo-controlled crossover clinical trial of memantine (20 mg), with a 3-week treatment period, and 15 patients completed the study. RESULTS: The primary outcome measure, a change in observed dyskinesia ratings, did not reach significance. Seven of the 15 patients reduced the L-dopa-induced dyskinesias by 32%, whereas for three patients, they increased by 33%, and for five patients, they did not change. Data from the self-administered diaries, as a secondary outcome measure, did show a significant 35% reduction in the percentage of time of the day spent with dyskinesia, from 25% (placebo) to 16% (memantine). Memantine was well tolerated, without any serious adverse events, or worsening in the parkinsonian motor score. CONCLUSION: The results suggest that memantine may be a useful antidyskinetic drug, and a larger clinical study is warranted.

Interim analysis of long-term intraduodenal levodopa infusion in advanced Parkinson disease.

BACKGROUND: This interim 12-month analysis is a part of an open-label, observational, prospective study on health outcomes and cost impact of levodopa/carbidopa intestinal gel (LCIG, Duodopa) in Parkinson disease (PD). The specific aim was to investigate clinical and health-related quality of life (HRQoL) effects in routine care. METHODS: Unified PD rating scale (UPDRS) was the primary efficacy measurement. PD QoL questionnaire 39 (PDQ-39) assessed HRQoL. Subjects were assessed at baseline, ≥3 months after surgery, and then every 3 months. RESULTS: Twenty-seven treatment-naïve subjects when started with LCIG showed a decrease in UPDRS score that was statistically significant throughout the year: UPDRS total score (mean ± SD), baseline = 52.1 ± 16.1, N = 27, month 0 (first visit; at least 3 months after permanent LCIG) = 43.1 ± 16.7, N = 27, P = 0.003; month 12 = 42.5 ± 22.6, n = 25, P = 0.017. PDQ-39 results also showed a tendency for improvement: PDQ-39 (mean ± SD), baseline = 33.6 ± 10.8, N = 27, month 0 = 27.1 ± 11.8, N = 27, P = 0.001; 12 months = 28.8 ± 12.8, n = 23, P = 0.126. CONCLUSIONS: LCIG provides functional improvement beginning at first visit that is sustained for 12 months.

Caspase inhibition reduces apoptosis and increases survival of nigral transplants.

Transplantation of embryonic nigral tissue ameliorates functional deficiencies in Parkinson disease. The main practical constraints of neural grafting are the shortage of human donor tissue and the poor survival of dopaminergic neurons grafted into patients, which is estimated at 5-10% (refs. 3,4). The required amount of human tissue could be considerably reduced if the neuronal survival was augmented. Studies in rats indicate that most implanted embryonic neurons die within 1 week of transplantation, and that most of this cell death is apoptotic. Modified peptides, such as acetyl-tyrosinyl-valyl-alanyl-aspartyl-chloro-methylketone (Ac-YVAD-cmk), that specifically inhibit proteases of the caspase family effectively block apoptosis in a plethora of experimental paradigms, such as growth factor withdrawal, excitotoxicity, axotomy, cerebral ischemia and brain trauma. Here we examined the effects of caspase inhibition by Ac-YVAD-cmk on cell death immediately after donor tissue preparation and on long-term graft survival. Treatment of the embryonic nigral cell suspension with Ac-YVAD-cmk mitigated DNA fragmentation and reduced apoptosis in transplants. It also increased survival of dopaminergic neurons grafted to hemiparkinsonian rats, and thereby substantially improved functional recovery.

Overexpressing Cu/Zn superoxide dismutase enhances survival of transplanted neurons in a rat model of Parkinson's disease.

A high survival rate of grafted dopamine neurons is crucial for reversing neurological deficits following brain tissue transplantation in Parkinson's disease. For unknown reasons the survival rate of transplanted dopamine neurons is only around 10% in experimental animals. The hypothesis that oxidative stress causes the loss of transplanted neurons was tested by grafting neurons from transgenic mice that overexpress Cu/Zn superoxide dismutase. Compared with the survival of those taken from non-transgenic littermates, the survival was 4 times higher for the transgenic dopamine neurons with a concomitant more extensive functional recovery. The results provide direct support for the free radical hypothesis of dopaminergic neuron death in brain tissue grafting.

Grafts of fetal dopamine neurons survive and improve motor function in Parkinson's disease.

Neural transplantation can restore striatal dopaminergic neurotransmission in animal models of Parkinson's disease. It has now been shown that mesencephalic dopamine neurons, obtained from human fetuses of 8 to 9 weeks gestational age, can survive in the human brain and produce marked and sustained symptomatic relief in a patient severely affected with idiopathic Parkinson's disease. The grafts, which were implanted unilaterally into the putamen by stereotactic surgery, restored dopamine synthesis and storage in the grafted area, as assessed by positron emission tomography with 6-L-[18F]fluorodopa. This neurochemical change was accompanied by a therapeutically significant reduction in the patient's severe rigidity and bradykinesia and a marked diminuation of the fluctuations in the patient's condition during optimum medication (the "on-off" phenomenon). The clinical improvement was most marked on the side contralateral to the transplant.

Dopamine release from nigral transplants visualized in vivo in a Parkinson's patient.

Synaptic dopamine release from embryonic nigral transplants has been monitored in the striatum of a patient with Parkinson's disease using [11C]-raclopride positron emission tomography to measure dopamine D2 receptor occupancy by the endogenous transmitter. In this patient, who had received a transplant in the right putamen 10 years earlier, grafts had restored both basal and drug-induced dopamine release to normal levels. This was associated with sustained, marked clinical benefit and normalized levels of dopamine storage in the grafted putamen. Despite an ongoing disease process, grafted neurons can thus continue for a decade to store and release dopamine and give rise to substantial symptomatic relief.

Xenotransplantation for CNS repair: immunological barriers and strategies to overcome them.

Neural transplantation holds promise for focal CNS repair. Owing to the shortage of human donor material, which is derived from aborted embryos, and ethical concerns over its use, animal donor tissue is now considered an appropriate alternative. In the USA, individuals suffering from Parkinson's disease, Huntington's disease, focal epilepsy or stroke have already received neural grafts from pig embryos. However, in animal models, neural tissue transplanted between species is usually promptly rejected, even when implanted in the brain. Some of the immunological mechanisms that underlie neural xenograft rejection have recently been elucidated, but others remain to be determined and controlled before individuals with neurological disorders can benefit from xenotransplantation.

Immature neural tissue grafts in Parkinson's disease.

Intracerebral transplantation of immature neural tissue is a promising therapeutical approach that has the potential of restoring damaged neuronal circuitries and reversing functional deficits. The development of the technique as a human application has progressed the furthest in Parkinson's disease (PD), with the demonstration of significant longlasting functional improvements, in combination with evidence of surviving grafted tissue, using a fluorodopa positron emission tomography (PET) scanning technique in a few patients. Although the technique is promising, and the effects observed are significant and of clinical importance for the grafted patients in the best cases so far, there are still incomplete effects and no transplantation treatment is suggested since there are still several technical aspects that might further improve the outcome. The progress of the development in the field is briefly reviewed.

Human fetal dopamine neurons grafted into the striatum in two patients with severe Parkinson's disease. A detailed account of methodology and a 6-month follow-up.

By using stereotaxic surgical techniques, ventral mesencephalic tissues from aborted human fetuses of 8 to 10 weeks' gestational age were implanted unilaterally into the striata in two patients with advanced Parkinson's disease. The patients were treated with a cyclosporine, azathioprine, and steroid regimen to minimize the risk for graft rejection. They were examined for 6 months preoperatively and 6 months postoperatively and continued to receive the same doses of antiparkinsonian medication. There were no significant postoperative complications. No major therapeutic effect from the operation was observed. However, in the clinical tests, both patients showed small but significant increases of movement speed for repeated pronation-supination, fist clenching, and foot lifting. The rate of walking also increased in the one patient tested. For both patients, there was an initial worsening postoperatively, followed by improvement vs preoperative performance at 1 to 3 months. Both patients also showed significant improvement in the magnitude of response to a single dose of levodopa (L-dopa), but there was no increase in the duration of drug action. The motor readiness potential increased in both patients postoperatively, primarily over the operated hemisphere. Neurophysiological measurements also showed a more rapid performance of simple and complex arm and hand movements on the side contralateral to transplantation in one patient at 5 months postoperatively. Positron emission tomography demonstrated no increased uptake of 6-L-(18F)-fluorodopa in the transplanted striatum at 5 and 6 months. Taken together, these results suggest that the fetal nigral implants may have provided a modest improvement in motor function, consistent with the presence of small surviving grafts. Although our results support further scientific experimentation with transplantation in Parkinson's disease, widespread clinical trials with this procedure are probably not warranted at this time.

Can sensory stimulation improve the functional outcome in stroke patients?

After obtaining informed consent, we randomized 78 patients with severe hemiparesis of the left or right side within 10 days of stroke onset: 40 to a control group receiving daily physiotherapy and occupational therapy, and 38 to a group that, in addition, we treated with sensory stimulation (acupuncture) twice a week for 10 weeks. The median age was 76 years for both groups. Motor function, balance, and ADL (Barthel's Index) were assessed before the start of treatment and at 1 and 3 months after stroke onset; ADL was also assessed after 12 months. We assessed the quality of life (QL) using the Nottingham Health Profile 3, 6, and 12 months after stroke onset. Patients given sensory stimulation recovered faster and to a larger extent than the controls, with a significant difference for balance, mobility, ADL, QL, and days spent at hospitals/nursing homes. Whether acupuncture per se is responsible for the differences requires further study.

Discordant neural tissue xenografts survive longer in immunoglobulin deficient mice.

BACKGROUND: The immune response against discordant xenografts in the brain is incompletely understood and remains a major obstacle for future clinical applications of xenogeneic neural tissue transplants in neurodegenerative disorders. To determine the role of antibodies in the rejection process, we compared graft survival and immune reactions between immunoglobulin deficient (IgKO) and normal mice. METHODS: A cell suspension of embryonic porcine ventral mesencephalon was injected into the striatum of adult normal and IgKO mice. Graft sizes and number of infiltrating CD4- and CD8-positive lymphocytes were determined by stereological methods at 4 days and 2, 4, and 6 weeks after the transplants. Microglial accumulation was determined using the optical densitometrical method. Intraparenchymal deposition of IgG was investigated at 4 days and 2 weeks. RESULTS: The majority of IgKO mice had surviving grafts for up to 4 weeks, whereas survival was minimal in control mice beyond 4 days. Graft sizes differed significantly between IgKO and control mice at 2 weeks (P<0.01, Kruskal Wallis ANOVA, followed by Mann Whitney test). The majority of infiltrating lymphocytes were CD4-positive in control mice but CD8-positive in IgKO mice. Microglial accumulation was strong around surviving grafts in IgKO mice at 4 weeks. Prominent staining of IgG, diffuse in the transplanted hemisphere and specific on grafted neurons, was found in control mice. CONCLUSIONS: Our results suggest that immunoglobulins play an initiating role in rejection of discordant neural xenografts. After a prolonged graft survival of approximately 4 weeks, a cellular response with a large proportion CD8-positive cells leads to rejection in IgKO mice.

Effects of immunosuppressive treatment on host responses against intracerebral porcine neural tissue xenografts in rats.

BACKGROUND: Embryonic xenogeneic neural tissue is an alternative for transplantation in Parkinson's disease, but immune responses limit the application. The aims of this study were to enhance the in vitro viability rates by donor tissue pretreatment; to compare the efficacy of cyclosporine A (CsA) and tacrolimus (FK) in inhibiting xenograft rejection in rats; to evaluate additional inductive therapy with prednisolone (PRE) or mycophenolate mofetil (MMF). METHODS: Tirilazad (a lipid peroxidase inhibitor) or FK and acYVAD-cmk (a caspase inhibitor), were added to embryonic porcine ventral mesencephalic tissue and viability was assessed in vitro. Tirilazad-treated tissue was grafted to the striatum of rats that were either left untreated or immunosuppressed with FK (1 mg/kg) or CsA (15 mg/kg) alone or in combination with a 2-week PRE (20 mg/kg) or MMF (40 mg/kg) induction course. Xenograft survival and host responses were determined using immunohistochemistry. RESULTS: Pretreatment with tirilazad enhanced tissue survival in vitro. After transplantation into untreated controls, there was no graft survival at twelve weeks. Neural cell counts were significantly improved in immunosuppressed recipients, but there were no differences between the treatment groups. Additional inductive treatment reduced the infiltration with CD4+ and CD8+ cells, and macrophage infiltration was reduced compared with animals given CsA or FK alone. CONCLUSION: Pretreatment of the donor tissue with free-radical scavengers reduces cell loss caused by tissue trauma. Porcine neural tissue xenografts survive significantly better in animals immunosuppressed with either FK or CsA. Additional inductive treatment with PRE or MMF reduced the infiltration of host cells into the xenografts.

Addition of allogeneic spleen cells causes rejection of intrastriatal embryonic mesencephalic allografts in the rat.

To address the importance of antigen-presenting cells for the survival of intracerebral neural allografts, allogeneic spleen cells were added to the graft tissue before transplantation. Dissociated embryonic, dopamine-rich mesencephalic and adult spleen tissues were prepared from either inbred Lewis or Sprague-Dawley rats. A mixture of neural and spleen cells was sterotaxically transplanted into the right striatum of adult Sprague-Dawley rats. Controls were neural allografts without addition of allogeneic spleen cells and syngeneic neural grafts with or without the addition of syngeneic spleen cells. Six weeks after transplantation, brain sections were processed immunocytochemically for tyrosine hydroxylase, specific for grafted dopamine neurons, and a bank of markers for various components in the immune and inflammatory responses. The neural allografts which were mixed with allogeneic spleen cells were rejected. In these rats, there were high levels of expression of major histocompatibility complex class I and II antigens, intense cellular infiltration including macrophages and activated microglial cells, and a presence of cluster of differentiation 4- and 8-immunoreactive cells in the graft sites. Moreover, there were increased levels of intercellular adhesion molecule-1, tumour necrosis factor-alpha and interleukin-6 in and around the grafts which were undergoing rejection. In contrast, syngeneic neural grafts survived well regardless of whether they were mixed with syngeneic spleen cells or not, and control neural allografts also exhibited unimpaired survival. No significant difference was observed in the number of grafted dopamine neurons among these three latter groups. The levels of expression of the different markers for inflammation and rejection were generally lower in these grafts than in implants of combined allogeneic neural and spleen cells. In summary, intrastriatal neural allografts, which normally survive well in our animal model, were rejected if allogeneic spleen cells from the same donor were added to the graft tissue. The added spleen cells caused strong host immune and inflammatory responses. The study gave support to the notion that immunological privilege of the brain does not provide absolute protection to immunogenetically histoincompatible neural grafts.

Sequential intrastriatal grafting of allogeneic embryonic dopamine-rich neuronal tissue in adult rats: will the second graft be rejected?

An important issue in clinical neural grafting is whether a second instriatial allograft can survive well in a patient who has received an allograft before. In this study, the survival, immunogenicity and function of intrastriatal grafts of allogeneic or syngeneic embryonic dopamine-rich tissue in rats which had previously received either an intrastriatal allo- or syn-graft or sham injections were examined. The first graft tissue was taken from inbred Lewis or Sprague-Dawley rat embryos and grafted into an intact striatum of adult Sprague-Dawley rats subjected to a unilateral 6-hydroxydopamine lesion on the contralateral side. Eight weeks after the first transplantation, either allogeneic or syngeneic tissue was grafted as dissociated tissue into the dopamine depleted striatum. The function of the second grafts was assessed by rotational asymmetry at two different time points, i.e. eight and 14 weeks after the second transplantation. There were significant reductions of rotational asymmetry in all groups over time, but no significant difference between groups. Tyrosine hydroxylase immunocytochemistry was used to assess dopamine cell survival and graft size. Statistical analysis revealed no significant differnce in the mean number of tyrosine hydroxylase immunoreactive cells or the mean volume of the second grafts placed on the right side (lesioned side) between groups. Monoclonal antibodies were used to evaluate cellular immune reactions and the major histocompatibility complex class I and class II expression in and around grafts. No major histocompatibility complex class I expression was seen in any of the graft combinations. The expression of the major histocompatibility complex class II antigens was generally higher in patches in and around the second allograft of rats which had previously received an allograft than that in and around any other type of grafts. However, the expression of the major histocompatibility complex class II antigens was low throughout the grafts and did not appear as marked perivascular infiltrates. All the major histocompatibility complex class II positive cells displayed a microglia-like morphology, supported by the parallel microglia and macrophage-specific OX-42 immunostaining. The results show that there is no marked on-going immune reactions in or around the implantation site in any group fourteen weeks after a second transplantation. It may be concluded, therefore, that sequential allografting, using stereotaxic implantation of dissociated embryonic neural tissue into the striatal parenchyma, is possible to perform without a major risk of graft rejection, provided that an atraumatic technique is used.

Antioxidant treatment protects striatal neurons against excitotoxic insults.

It has been suggested that oxidative stress plays an important role in mediating excitotoxic neuronal death. We have therefore investigated the protective effects of antioxidants against excitotoxic injury in the rat on striatal neurons both in vitro and in vivo. In the first part of the study, we determined whether two different types of antioxidants, the spin trapping agent, alpha-phenyl-tert-butyl nitrone and an inhibitor of lipid peroxidation, U-83836E, could protect cultured striatal neurons against either hypoglycemic injury or N-methyl-D-aspartate-induced excitotoxicity. Dopamine- and cyclic AMP-regulated phosphoprotein, which is enriched in medium-sized spiny neurons, was chosen as a marker for striatal neurons. alpha-Phenyl-t-butyl nitrone and U-83836E both significantly reduced cell death induced by these insults as indicated by an increased number of surviving dopamine- and cyclic AMP-regulated phospho-protein-positive neurons. The two antioxidants also promoted the survival of cultured striatal neurons grown at low cell density under serum-free culture conditions. In an in vivo experiment systemically administered alpha-phenyl-t-butyl nitrone exerted neuroprotective effects in the rat striatum following injection of the excitotoxin quinolinic acid. Apomorphine-induced rotation tests revealed that alpha-phenyl-t-butyl nitrone-treated animals were significantly less asymmetric in their motor behavior than control rats. Treatment with alpha-phenyl-t-butyl nitrone significantly reduced the size of the quinolinic acid-induced striatal lesions, as assessed by the degree of sparing of dopamine- and cyclic AMP-regulated phospho-protein-positive and nicotinamide adenine dinucleotide phosphate-diaphorase-positive neurons, and of microtubule-associated protein-2-immunorective areas. Furthermore, lesion-induced morphological changes in the substantia nigra pars reticulate, i.e. loss of dopamine- and cyclic AMP-regulated phosphoprotein-positive afferent fibers and atrophic changes due to transsynaptic degeneration, were also less extensive in the alpha-phenyl-t-butyl nitrone-treated animals. The results support the hypothesis that oxygen-free radicals contribute to excitotoxic neuronal injury. The in vivo cytoprotective effects of alpha-phenyl-t-butyl nitrone against striatal excitotoxic lesions suggest that antioxidants could be used as potential neuroprotective agents in Huntington's disease, which has been suggested to involve excitotoxicity.

DARPP-32-rich zones in grafts of lateral ganglionic eminence govern the extent of functional recovery in skilled paw reaching in an animal model of Huntington's disease.

Grafts of striatal tissue comprise two different types of tissue: regions with (P-zones) and without (NP-zones) neurons that express markers characteristic of the striatum, such as dopamine- and cyclic AMP-regulated phosphoprotein with a mol. wt of 32,000 (DARPP-32). It remains unclear whether P-zones alone play a crucial role in functional effects of striatal grafts in an animal model of Huntington's disease. The present study has been performed to determine: (i) the yield of DARPP-32-positive neurons in grafts of lateral ganglionic eminence; (ii) whether treatment of graft tissue with the spin-trapping agent alpha-phenyl-tert-butyl nitrone enhances the survival of implanted DARPP-32-positive neurons; and (iii) the relationship between the number of DARPP-32-positive neurons in the grafts and functional effects of the grafts on paw-reaching ability in rats with unilateral quinolinic acid lesions of the striatum. Dissociated tissue derived from the lateral ganglionic eminence of rat embryos (embryonic day 14), with or without addition of alpha-phenyl-tert-butyl nitrone (3 mM), was implanted into the quinolinic acid-lesioned striatum. Compared to unlesioned normal animals, rats with striatal lesions showed substantial impairment in paw-reaching ability, particularly on the side contralateral to the lesion, as judged from the number of pellets retrieved by each paw. Intrastriatal grafts gave rise to a significant improvement in paw-reaching ability. The mean total number of surviving DARPP-32-positive cells in grafts without alpha-phenyl-tert-butyl nitrone treatment was estimated at 115 x 10(3), which did not significantly differ from that in alpha-phenyl-tert-butyl nitrone-treated grafts. The paw-reaching scores were significantly correlated with the volumes of P-zones and the number of DARPP-32-positive neurons, but with neither the volumes of NP-zones nor the total graft volume. The results suggest that P-zones in striatal grafts mediate graft-derived functional recovery in a complex task such as skilled forelimb use. Although the antioxidant treatment with alpha-phenyl-tert-butyl nitrone failed to promote graft survival, the positive correlation between the yield of DARPP-32-positive cells in the graft and the extent of the functional recovery highly warrants further attempts to increase the yield of the striatal component in the graft.

Immune reactions following systemic immunization prior or subsequent to intrastriatal transplantation of allogeneic mesencephalic tissue in adult rats.

We have previously found that dissociated mesencephalic tissue, which differs from the host at both major histocompatibility complex and non-major histocompatibility complex gene loci, can survive stereotaxic transplantation to the striatum of adult rats. We have now studied the outcome of intrastriatal neural allografts in rats that were systemically immunized by an orthotopic skin allograft either prior or subsequent to intracerebral implantation surgery. Dissociated mesencephalic tissue from Lewis rat embryos was stereotaxically injected into the dopamine-depleted striatum of hemi-parkinsonian Sprague-Dawley rats. One group was immunized by an orthotopic allogeneic skin graft of the same genetic origin as the neural graft, six weeks before the neural transplantation (the pre-immunized group). Another group was post-immunized by an orthotopic skin allograft, six weeks after the neural transplantation (the post-immunized group). A control group of rats was not challenged by a skin allograft. Marked behavioural recovery was observed in six of seven rats in the control group, in six of eight rats in the post-immunized group, and in none of the pre-immunized rats. Tyrosine hydroxylase-immunopositive cells were found in rats from the two behaviourally compensated groups, but not in the pre-immunized group. The immune responses were evaluated by OX-18 (monoclonal antibody against major histocompatibility complex class I antigen), OX-6 (major histocompatibility complex class II antigen), OX-42 (microglia and macrophages), glial fibrillary acidic protein (astrocytes), OX-8 (cytotoxic T-lymphocytes) and W3/25 (helper T-lymphocytes) immunocytochemistry. All the neural allografts in the pre-immunized group were rejected, leaving scars only. There were more intense immune responses to the allografts in the post-immunized group than the control group, in terms of immunocytochemically higher expression of major histocompatibility complex class I and II antigens and more intense cellular reactions consisting of macrophages, activated microglia and astrocytes, in addition to CD8- and CD4-positive lymphocytes. In summary, the results show the following: (i) systemic pre-immunization leads to complete rejection of intrastriatal neural allografts, implying that the status of the host immune system before transplantation determines the outcome for intrastriatal neural allografts; (ii) established intrastriatal neural allografts can survive for at least six weeks after systemic immunization, in spite of increased host immune responses in and around the allografts; (iii) there are no marked immune reactions against intrastriatal neural allografts 13 weeks after implantation in rats which have not been systemically immunized by a skin allograft; (iv) pre-immunized rats may provide a very useful animal model to investigate the role of inflammatory lymphokines in immune rejection and to test alternative immunosuppressive drugs.

Sequential intracerebral transplantation of allogeneic and syngeneic fetal dopamine-rich neuronal tissue in adult rats: will the first graft be rejected?

The immune response against intracerebral grafts of allogeneic fetal dopamine-rich tissue was assessed in adult rats. Sprague-Dawley rats, now outbred, but originating from an inbred stock, were given unilateral 6-hydroxy-dopamine lesions of the mesostriatal pathway, and grafted intrastriatally with mechanically dissociated ventral mesencephalic tissue (embryonic day 13-15) obtained from an inbred Lewis strain. Graft survival was assessed by functional recovery of amphetamine-induced rotational behavior on four different occasions postsurgery, and histologically using catecholamine histofluorescence and tyrosine hydroxylase immunohistochemistry. The following groups were analysed: long-term survival of a single allogeneic graft; survival of a first allogeneic graft with a syngeneic second graft; survival of a first allograft combined with a second allogeneic graft; the survival of bilateral allogeneic grafts following a subsequent orthotopic allogeneic skin graft. Evidence for recipient immunization was obtained using an indirect fluorescent antibody detection technique, Simonsen's Spleen Index (S I) test. Viable grafts, giving rise to behavioral compensation, were present after 40 wk in rats from all groups. The "first" allograft always displayed good survival and function, even following a second intracerebral allograft. However, five of nine "second" allogeneic intracerebral grafts survived poorly. In contrast, all secondary syngeneic grafts survived well. Following the application of a subsequent orthotopic allogeneic skin graft in a subgroup of rats, there was a significantly lower survival of grafted dopamine neurons in the "first" graft.

Neural tissue xenotransplantation: what is needed prior to clinical trials in Parkinson's disease? Neural Tissue Xenografting Project.

Embryonic allografted human tissue in patients with Parkinson's disease has been shown to survive and ameliorate many of the symptoms of this disease. Despite this success, the practical problems of using this tissue coupled to the ethical restrictions of using aborted human fetal tissue have lead to an exploration for alternative sources of suitable material for grafting, including xenogeneic embryonic dopaminergic-rich neural tissue. Nevertheless, xenografted neural tissue itself generates a number of practical, ethical, safety, and immunological issues that have to be addressed prior to any clinical xenotransplant program. In this article we review these critical issues and set out the criteria that we consider need to be met in the development of our clinical xenotransplantation research programs. We advocate that these, or similar, criteria should be adopted and made explicit by other centers contemplating similar clinical trials.