The Influence of Donor Age on the Survival of Solid and Suspension Intraparenchymal Human Embryonic Nigral Grafts

In many species, graft survival and graft-derived behavioral recovery are affected by the embryonic donor age. We compared the ability of solid and suspension grafts of human embryonic mesencephalic dopaminergic (DA) neurons at different embryonic stages to survive intra-parenchymal transplantation into 6-OHDA lesioned immunosuppressed rats. Suspension grafts survived best when donor age was between postconception (PC) days 34 and 56. Transplants displayed numerous healthy tyrosine hydroxylase immunoreactive (TH-IR) neurons which sent extensive neuritic processes into the host striatum. Suspension grafts survived poorly when donor age was greater than 65 days. Solid implants displayed comparable viability of TH-IR neurons when donor age was between 44 and 65 days. No solid grafts contained TH-IR cells when donor tissue was older than 72 days. The suspension and solid methods of transplantation resulted in comparable survival of robust grafts, but solid grafts resulted in more intergraft variability than suspension grafts, particularly among the more marginal implants. Our results demonstrate that the upper limit for survival of human embryonic DA suspension grafts correlates well with the period of development of the human nigrostriatal pathway. The “window” for donor age of solid human embryonic DA grafts appears to be extended by about 9 days in comparison to suspension grafts. These data suggest that the upper age limit for grafting human mesencephalic DA neurons should be PC day 56 for suspension grafts, and PC day 65 for solid implants. Older donors are likely to produce grafts with fewer surviving DA neurons.

Cyclosporine-A Increases Spontaneous and Dopamine Agonist-Induced Locomotor Behavior in Normal Rats

Cyclosporine-A (CsA) has been increasingly used as an immunosuppressant concomitant with neural transplantation treatment for different degenerative disorders. However, the possible role that CsA itself may have in the recovery of transplant patients is not known. Some investigators have argued that clinical improvement following transplantation (e.g., myoblast) may be confounded by CsA administration. The present study was conducted to delineate CsA-induced behavioral alterations. Four groups of normal 5-wk old Sprague-Dawley rats (n = 8 per group) were utilized in two separate experiments. In both experiments, two groups of animals were used; each group either received daily injections of 15 mg/kg of CsA or olive oil for 32 days (experiment 1) and 21 days (experiment 2). Animals in both experiments were subsequently tested for nocturnal locomotor behavior. Animals in experiment 2 were further tested in passive avoidance task, motor coordination, and amphetamine-induced locomotor activity. Results demonstrated that CsA-treated animals were significantly hyperactive compared to controls across the 12-h nocturnal activity periods and in amphetamine-induced locomotor activity. No significant differences between the CsA- and vehicle-treated animals were observed in passive avoidance or in motor coordination. Postmortem analyses of dopamine and its metabolites in the striatum and olfactory tubercle did not show any significant differences between the CsA- and the vehicle-treated groups. In summary, CsA significantly increased nocturnal spontaneous and amphetamine-induced locomotor behavior, but the neurochemical correlates for these effects need to be investigated. In addition, while the present study demonstrated that CsA induced motor alterations, any possible effects CsA may have on neurological or dystrophic patients with motor dysfunctions remain to be determined.

Fetal Grafting for Parkinson's Disease: Expression of Immune Markers in Two Patients with Functional Fetal Nigral Implants

In a number of centers throughout the world, fetal nigral transplantation is being performed for the treatment of Parkinson's disease (PD). Clinical results have been inconsistent. One parameter that differs among transplant studies is the degree and manner by which patients are immunosuppressed following transplantation. Indeed, the role of the immune system following fetal grafting in humans is not well understood. Recently, two patients from our open label trial that received fetal nigral implants have come to autopsy. These patients were immunosuppressed with cyclosporin for 6 mo posttransplantation and survived for a total of 18 mo postgrafting. Robust survival of grafted dopamine-containing cells was observed in both cases. Immunostaining for HLA-DR revealed a dense collection of cells within grafts from both cases. HLA-DR staining was rarely observed within the host including non-grafted regions of the striatum. A more detailed analysis of immune markers was performed in Case 2. Numerous pan macrophages, T-cells, and B-cells were observed within graft sites located in the postcommissural putamen. In contrast, staining for these immune cells was not observed within the ungrafted anterior putamen. These findings suggest that even in healthy appearing functional nigral implants, grafts are invaded by host immune cells that could compromise their long-term viability and function. Alternatively, immune cells are known to secrete trophic factors, which may ultimately favor graft survival and function. Further work is needed to understand the role of the immune system in fetal grafting.

Microcarrier Enhanced Survival of Human and Rat Fetal Ventral Mesencephalon Cells Implanted in the Rat Striatum

The transplantation of tissue containing dopamine-producing cells into the mammalian central nervous system is an emerging treatment for Parkinson's disease, despite relatively poor survival of implanted tissue. Recent evidence has suggested that Cytodex microcarriers enhance the survival of dopaminergic rat chromaffin cells transplanted into the rat striatum in the absence of immunosuppression. The current study was undertaken to evaluate the survival of rat and human fetal ventral mesencephalic neurons (VM) implanted alone or after attachment to microcarriers in the striatum of rats without immunosuppression. Rat fetal VM neurons demonstrated enhanced survival in the rat striatum when transplanted on microcarriers, compared to their transplantation alone during the 3-mo period examined in the present study. Transplants of human fetal VM neurons on microcarriers also survived remarkably well in the rat striatum without systemic immunosuppression. In contrast, human fetal VM cells transplanted alone into the rat striatum did not survive without systemic immunosuppression. There was no evidence of TH fiber sprouting in the vicinity of any transplant site. These data indicated that Cytodex microcarriers provide enhanced survival of both rat allograft and human xenograft fetal mesencephalic cells in the rat striatum without the necessity of systemic immunosuppression, perhaps by inducing a unique neuron–glia environment.

Trophic Effect of Porcine Sertoli Cells on Rat and Human Ventral Mesencephalic Cells and Hnt Neurons in Vitro

The poor survival of embryonic dopaminergic (DA) neurons transplanted into patients with Parkinson's disease (PD) has encouraged researchers to search for new methods to affect the short- as well as long-term survival of these neurons after transplantation. In several previous rodent studies Sertoli cells increased survival of islet cells and chromaffin cells when cotransplanted in vivo. The aims of this study were to investigate whether porcine Sertoli cells had a positive effect on the survival and maturation of rat and human DA neurons, and whether the Sertoli cells had an effect on differentiation of neurons derived from a human teratocarcinoma cell line (hNT neurons). A significant increase of tyrosine hydroxylase (TH)-positive neurons of both rat and human ventral mesencephalic tissue was found when cocultured with Sertoli cells. Furthermore, there was a significantly increased soma size and neurite outgrowth of neurons in the coculture treated group. The Sertoli cell and hNT coculture also revealed an increased number of TH-positive cells. These results demonstrate that the wide variety of proteins and factors secreted by porcine Sertoli cells benefit the survival and maturation of embryonic DA neurons and suggest that cotransplantation of Sertoli cells and embryonic DA neurons may be useful for a cell transplantation therapy in PD.

The synaptic impact of the host immune response in a parkinsonian allograft rat model: Influence on graft-derived aberrant behaviors

Graft-induced dyskinesias (GIDs), side-effects found in clinical grafting trials for Parkinson's disease (PD), may be associated with the withdrawal of immunosuppression. The goal of this study was to determine the role of the immune response in GIDs. We examined levodopa-induced dyskinesias (LIDs), GID-like behaviors, and synaptic ultrastructure in levodopa-treated, grafted, parkinsonian rats with mild (sham), moderate (allografts) or high (allografts plus peripheral spleen cell injections) immune activation. Grafts attenuated amphetamine-induced rotations and LIDs, but two abnormal motor syndromes (tapping stereotypy, litter retrieval/chewing) emerged and increased with escalating immune activation. Immunohistochemical analyses confirmed immune activation and graft survival. Ultrastructural analyses showed increases in tyrosine hydroxylase-positive (TH+) axo-dendritic synapses, TH+ asymmetric specializations, and non-TH+ perforated synapses in grafted, compared to intact, striata. These features were exacerbated in rats with the highest immune activation and correlated statistically with GID-like behaviors, suggesting that immune-mediated aberrant synaptology may contribute to graft-induced aberrant behaviors.

Studying neurosurgical implants for Parkinson disease: A question of design

North American researchers' perspectives on designing neurosurgical implant studies for Parkinson disease (PD) challenged the custom of holding surgical trials to less stringent evidentiary standards than other clinical studies. Researchers supported placebo surgery-controlled trials. The framework they used to design and evaluate studies both of deep brain stimulation and cellular implants for PD may be applicable to a broad range of surgical implants for other disorders.

Bilateral human fetal striatal transplantation in Huntington's disease

BACKGROUND

Transplanted striatal cells have been demonstrated to survive, grow, establish afferent and efferent connections, and improve behavioral signs in animal models of Huntington's disease (HD).

OBJECTIVE

To evaluate feasibility and safety and to provide preliminary information regarding the efficacy of bilateral human fetal striatal transplantation in HD.

METHODS

Seven symptomatic patients with genetically confirmed HD underwent bilateral stereotactic transplantation of two to eight fetal striata per side in two staged procedures. Tissue was dissected from the lateral half of the lateral ventricular eminence of donors 8 to 9 weeks postconception. Subjects received cyclosporine for 6 months.

RESULTS

Three subjects developed subdural hemorrhages (SDHs) and two required surgical drainage. One subject died 18 months after surgery from probable cardiac arrhythmia secondary to severe atherosclerotic cardiac disease. Autopsy demonstrated clearly demarcated grafts of typical developing striatal morphology, with host-derived dopaminergic fibers extending into the grafts and no evidence of immune rejection. Other adverse events were generally mild and transient. Mean Unified HD Rating Scale (UHDRS) motor scores were 32.9 plus minus 6.2 at baseline and 29.7 plus minus 7.5 12 months after surgery (p = 0.24). Post-hoc analysis, excluding one subject who experienced cognitive and motor deterioration after the development of symptomatic bilateral SDHs, found that UHDRS motor scores were 33.8 plus minus 6.2 at baseline and 27.5 plus minus 5.2 at 12 months (p = 0.03).

CONCLUSIONS

Transplantation of human fetal striatal cells is feasible and survival of transplanted cells was demonstrated. Patients with moderately advanced HD are at risk for SDH after transplantation surgery.

Neural transplantation in Parkinson's disease

In conclusion, proof of the principle exists that neural grafts can survive transplantation in PD and that this graft survival is related to preliminary evidence of clinical benefit and improvement on FD-PET. Two prospective, randomized, surgical placebo-controlled trials of fetal tissue transplantation for the treatment of PD will be published in the near future, as will results of a placebo-controlled xenograft trial. Lifelong survival of human fetal nigral grafts is likely. The striatum is comparatively simple to target surgically in comparison to other sites such as the subthalamic nucleus. Several new sources of dopamine cells are being developed for transplantation purposes. Long-term monitoring for toxicity, such as the development of dyskinesias, will be needed, and dose-escalation trials should be performed slowly due to the irreversible nature of transplants. There are numerous ways to improve current techniques of neural transplantation.

Apoptosis in cultured hNT neurons

Programmed cell death (apoptosis) is an important mechanism shaping the size of different cell populations within the developing nervous system. In our study we used the NT2/D1 clone originally established from the Ntera 2 cell line to investigate the baseline levels of apoptosis in cultured postmitotic hNT (NT2-N) neurons previously treated for 3, 4 or 5 weeks with retinoic acid (RA) and compared it with apoptosis in NT2 precursors unexposed to RA. First, we examined whether different lengths of exposure to RA might affect baseline apoptotic rate in differentiating hNT neurons. Second, we investigated whether cultured hNT neurons, previously shown to possess dopaminergic characteristics, would be preferentially affected by apoptosis. Using the terminal deoxynucleotidyl transferase (tdt)-labeling technique we found that the postmitotic hNT neuronal cells exposed to RA demonstrated significantly higher numbers of apoptotic cells (12.5-15.8%) in comparison to rapidly dividing NT2 precursor cell line (3.6-4.4%) at both studied (1 and 5 days in vitro, DIV) time points. Similar apoptotic nuclear morphology, including a variable extent of nuclear fragmentation was observed in all examined hNT cultures. On the other hand, the incidence of apoptotic nuclei was rare in cultures of NT2 precursors not subjected to RA treatment. Combined immunocytochemistry for tyrosine hydroxylase (TH) and Hoechst staining revealed dopaminergic hNT neurons destined to die. Our double-labeling studies have demonstrated that only a subset of TH-positive hNT cells had condensed chromatin after 1 (approx. 15%) and 5 (approx. 20%) DIV. NT2 precursors were not TH-positive. Collectively, our results demonstrated that exposure to differentiating agent RA triggers an apoptotic commitment in a subset of postmitotic hNT neurons. These results suggest that this cell line may serve as a model of neuronal development to test various pathogenic factors implicated in the etiology of Parkinson's disease (PD), as well as to screen numerous pharmacological treatments that may slow or prevent dopaminergic deterioration.

Transplantation of human fetal striatal tissue in Huntington's disease: rationale for clinical studies

Huntington's disease is a fatal neurological disorder characterized by chorea and deterioration in cognitive and neuropsychiatric function. Primary pathological changes are found in the striatum, where GABAergic neurons undergo degenerative changes. Local interneurons are relatively spared. Here, we describe the rationale for clinical trials of fetal striatal tissue transplantation for the treatment of Huntington's disease. Specifically, the reasons for utilizing tissue derived from the far lateral aspect of the lateral ventricular eminence as a source of striatal tissue will be discussed.

Transplanted fetal striatum in Huntington's disease: phenotypic development and lack of pathology

Neural and stem cell transplantation is emerging as a potential treatment for neurodegenerative diseases. Transplantation of specific committed neuroblasts (fetal neurons) to the adult brain provides such scientific exploration of these new potential therapies. Huntington's disease (HD) is a fatal, incurable autosomal dominant (CAG repeat expansion of huntingtin protein) neurodegenerative disorder with primary neuronal pathology within the caudate-putamen (striatum). In a clinical trial of human fetal striatal tissue transplantation, one patient died 18 months after transplantation from cardiovascular disease, and postmortem histological analysis demonstrated surviving transplanted cells with typical morphology of the developing striatum. Selective markers of both striatal projection and interneurons such as dopamine and c-AMP-related phosphoprotein, calretinin, acetylcholinesterase, choline acetyltransferase, tyrosine hydroxylase, calbindin, enkephalin, and substance P showed positive transplant regions clearly innervated by host tyrosine hydroxylase fibers. There was no histological evidence of immune rejection including microglia and macrophages. Notably, neuronal protein aggregates of mutated huntingtin, which is typical HD neuropathology, were not found within the transplanted fetal tissue. Thus, although there is a genetically predetermined process causing neuronal death within the HD striatum, implanted fetal neural cells lacking the mutant HD gene may be able to replace damaged host neurons and reconstitute damaged neuronal connections. This study demonstrates that grafts derived from human fetal striatal tissue can survive, develop, and are unaffected by the disease process, at least for 18 months, after transplantation into a patient with HD.

The X-gal caution in neural transplantation studies

Cell transplantation into host brain requires a reliable cell marker to trace lineage and location of grafted cells in host tissue. The lacZ gene encodes the bacterial (E. coli) enzyme beta-galactosidase (beta-gal) and is commonly visualized as a blue intracellular precipitate following its incubation with a substrate, "X gal," in an oxidation reaction. LacZ is the "reporter gene" most commonly employed to follow gene expression in neural tissue or to track the fate of transplanted exogenous cells. If the reaction is not performed carefully-with adequate optimization and individualization of various parameters (e.g.. pH, concentration of reagents, addition of chelators, composition of fixatives) and the establishment of various controls--then misleading nonspecific background X-gal positivity can result, leading to the misidentification of cells. Some of this background results from endogenous nonbacterial beta-gal activity in discrete populations of neurons in the mammalian brain; some results from an excessive oxidation reaction. Surprisingly, few articles have empha sized how to recognize and to eliminate these potential confounding artifacts in order to maximize the utility and credibility of this histochemical technique as a cell marker. We briefly review the phenomenon in general, discuss a specific case that illustrates how an insufficiently scrutinized X-gal positivity can be a pitfall in cell transplantation studies, and then provide recommendations for optimizing the specificity and reliability of this histochemical reaction for discerning E. coli beta-gal activity.

Adult bone marrow stromal cells differentiate into neural cells in vitro

Bone marrow stromal cells (BMSC) normally give rise to bone, cartilage, and mesenchymal cells. Recently, bone marrow cells have been shown to have the capacity to differentiate into myocytes, hepatocytes, and glial cells. We now demonstrate that human and mouse BMSC can be induced to differentiate into neural cells under experimental cell culture conditions. BMSC cultured in the presence of EGF or BDNF expressed the protein and mRNA for nestin, a marker of neural precursors. These cultures also expressed glial fibrillary acidic protein (GFAP) and neuron-specific nuclear protein (NeuN). When labeled human or mouse BMSC were cultured with rat fetal mesencephalic or striatal cells, a small proportion of BMSC-derived cells differentiated into neuron-like cells expressing NeuN and glial cells expressing GFAP.

Dopaminergic phenotype of hNT cells in vitro

We investigated the catecholaminergic nature of cultured hNT neurons previously treated either for 4 or 5 weeks with retinoic acid (RA). There were significantly more tyrosine hydroxylase (TH)-positive neurons (60%) in cultures treated for 4 weeks with RA compared to 5 week-treated cultures (</=15%). Furthermore, numerous TH-positive hNT cells were also immunoreactive to dopamine transporter (DAT), dopamine receptor (D2) and aldehyde dehydrogenase (AHD-2), an enzyme exclusively expressed by dopaminergic (DA) ventral mesencephalic (VM) precursors. Thus this cell line has all the necessary cellular machinery to produce functional DA neurons and therefore is a good alternative tissue source to fetal VM.

Sertoli cells enhance the survival of co-transplanted dopamine neurons

One of the major issues in neural transplantation is the low survival rate (<5%) of transplanted dopamine (DA) neurons [3]. Recently it has been shown that it is possible to enhance the survival of these neurons, which in turn may decrease the amount of tissue that is required for each transplantation patient. The present paper demonstrates a novel approach for enhancing neuronal survival by co-transplantation of neuronal tissue with Testis-derived Sertoli cells (SC). This strategy could improve neuronal survival through the provision of trophic support.

Sertoli cells decrease microglial response and increase engraftment of human hNT neurons in the hemiparkinsonian rat striatum

Sertoli cells (SCs) provide immune protection and nutritive support to the developing germ cells in the testis. Sertoli cells have also been shown to provide immune protection to islets transplanted outside the testes. In this study, the ability of these cells to diminish the infiltration/activation of microglia into a neural graft implanted in the lesioned striatum of a hemiparkinsonian rat was investigated. Human neuron-like cells (hNT neurons) were implanted either alone or in combination with rat SCs. Three months later, the animals were sacrificed and immunohistochemistry was performed to determine the survival of the xenografted neurons as well as microglial infiltration/activation. Cotransplantation of the SCs with the hNT neurons increased graft survival and was associated with an increase in graft size. Furthermore, there were fewer microglia present in the grafted tissue of the cotransplantation groups. These results show that SCs retain their immunosuppressive ability even within the brain. As immune responses to grafted neural tissue within the central nervous system become better understood, this ability of the SCs to provide localized immunosuppression to the transplanted tissue may become more important. This is particularly true as the search for alternative sources of neural tissue to treat neurodegenerative diseases expands to encompass other species.

Long-term evaluation of bilateral fetal nigral transplantation in Parkinson disease

BACKGROUND

Parkinson disease (PD) is associated with a progressive loss of nigrostriatal dopamine neurons. Medication therapy provides adequate control of symptoms for several years, but long-term treatment is complicated by progressive disability and the development of motor fluctuations and dyskinesias. In animal models of PD, fetal nigral transplants have been shown to survive grafting into the striatum, provide extensive striatal reinnervation, and improve motor function. In patients with PD, cell survival and clinical benefit have been observed following fetal nigral grafting, but results have been inconsistent.

OBJECTIVE

To evaluate the safety and efficacy of bilateral fetal nigral transplantation into the postcommissural putamen in patients with advanced PD complicated by motor fluctuations and dyskinesias.

PATIENTS AND METHODS

Six patients with advanced PD underwent bilateral fetal nigral transplantation. Each patient received solid grafts derived from donors aged 6 1/2 to 9 weeks after conception stereotactically implanted into the postcommissural putamen using 3 to 4 donors per side. Cyclosporine was administered for approximately 6 months to provide immune suppression. Clinical evaluations included the Unified Parkinson's Disease Rating Scale (UPDRS), Schwab-England Activities of Daily Living Scale, and timed tests of motor function conducted during both the "off' and "on" states at baseline and at 1, 3, 6, 9, 12, 18, and 24 months following transplantation. Percentage of time off and percentage of time on with and without dyskinesia were recorded at half-hour intervals using home diaries during the week prior to each evaluation. 18F-fluorodopa positron emission tomographic scans were performed at baseline, and at 6 months and 1 year following transplantation.

RESULTS

Patients have been followed up for a mean+/-SD of 20.5+/-5.5 months. Complications related to surgery were mild and transient. Activities of daily living, motor, and total (activities of daily living plus motor) UPDRS scores during the off state improved significantly (P<.05, Wilcoxon signed rank test) at final visit in comparison with baseline. Mean total UPDRS off score improved 32%, and each patient experienced at least a 19% improvement. Mean percentage of time on without dyskinesia during the waking day improved from 22% to 60% (P<.05). Mean putamenal fluorodopa uptake on positron emission tomography increased significantly at 6 and 12 months in comparison with baseline (P<.001, 2-tailed t test). This increase correlated with clinical improvement. Two patients died 18 months after transplantation from causes unrelated to the surgical procedure. In both cases, histopathological examination showed robust survival of tyrosine hydroxylase immunoreactive cells and abundant reinnervation of the postcommissural putamen.

CONCLUSIONS

Fetal nigral tissue can be transplanted into the postcommissural putamen bilaterally in patients with advanced PD safely and with little morbidity. In this open-label pilot study we observed consistent long-term clinical benefit and increased fluorodopa uptake on positron emission tomography. Clinical improvement appears to be related to the survival and function of transplanted fetal tissue.

Proteasome inhibitors prevent tracheary element differentiation in zinnia mesophyll cell cultures

To determine whether proteasome activity is required for tracheary element (TE) differentiation, the proteasome inhibitors clasto-lactacystin beta-lactone and carbobenzoxy-leucinyl-leucinyl-leucinal (LLL) were used in a zinnia (Zinnia elegans) mesophyll cell culture system. The addition of proteasome inhibitors at the time of culture initiation prevented differentiation otherwise detectable at 96 h. Inhibition of the proteasome at 48 h, after cellular commitment to differentiation, did not alter the final percentage of TEs compared with controls. However, proteasome inhibition at 48 h delayed the differentiation process by approximately 24 h, as indicated by examination of both morphological markers and the expression of putative autolytic proteases. These results indicate that proteasome function is required both for induction of TE differentiation and for progression of the TE program in committed cells. Treatment at 48 h with LLL but not clasto-lactacystin beta-lactone resulted in partial uncoupling of autolysis from differentiation. Results from gel analysis of protease activity suggested that the observed incomplete autolysis was due to the ability of LLL to inhibit TE cysteine proteases.

Fetal nigral grafts survive and mediate clinical benefit in a patient with Parkinson's disease

We have previously demonstrated that fetal nigral grafts can survive, reinnervate the striatum, and mediate clinically relevant recovery in a patient with Parkinson's disease (PD). Most previous autopsy cases have failed to identify meaningful numbers of viable grafted cells suggesting that differences in critical transplant variables determine graft viability. The present study evaluated the structural and functional correlates of fetal nigral transplantation in a second PD patient who received fetal nigral grafts according to our previously published transplant protocol. A 61-year-old woman with severe PD received bilateral fetal nigral grafts to the postcommissural putamen from seven donor fetuses (four right side and three left side) aged 6.5-9 weeks postconception. This patient died 19 months after surgery from a cause unrelated to the transplant surgery. Her postoperative clinical course was characterized by improved motor and activities of daily living scores during "off time," reduced "off time," and increased "on" time without dyskinesia. Positron emission tomography (PET) scans revealed a bilateral and progressive increase in fluorodopa (FD) uptake within the grafted putamen. Postmortem examination of the right hemisphere revealed large oval-shaped grafts containing more than 138,000 tyrosine-hydroxylase-immunoreactive (TH-ir) neurons. Grafted cells formed a seamless border with the host and provided dense TH-ir innervation to 78% of the host postcommissural putamen. Graft-mediated sprouting of host fibers was not observed. These data provide essential confirmation that, under appropriate transplant conditions, grafted nigral neurons can survive, reinnervate the host striatum, and provide clinical benefit to PD patients. These findings also support the concept that improved motor function and striatal FD uptake on PET after nigral grafting in PD are the result of the viability of grafted neurons and graft-derived reinnervation of the host striatum.

Trophic effect of porcine Sertoli cells on rat and human ventral mesencephalic cells and hNT neurons in vitro

The poor survival of embryonic dopaminergic (DA) neurons transplanted into patients with Parkinson's disease (PD) has encouraged researchers to search for new methods to affect the short- as well as long-term survival of these neurons after transplantation. In several previous rodent studies Sertoli cells increased survival of islet cells and chromaffin cells when cotransplanted in vivo. The aims of this study were to investigate whether porcine Sertoli cells had a positive effect on the survival and maturation of rat and human DA neurons, and whether the Sertoli cells had an effect on differentiation of neurons derived from a human teratocarcinoma cell line (hNT neurons). A significant increase of tyrosine hydroxylase (TH)-positive neurons of both rat and human ventral mesencephalic tissue was found when cocultured with Sertoli cells. Furthermore, there was a significantly increased soma size and neurite outgrowth of neurons in the coculture treated group. The Sertoli cell and hNT coculture also revealed an increased number of TH-positive cells. These results demonstrate that the wide variety of proteins and factors secreted by porcine Sertoli cells benefit the survival and maturation of embryonic DA neurons and suggest that cotransplantation of Sertoli cells and embryonic DA neurons may be useful for a cell transplantation therapy in PD.

Testis-derived Sertoli cells have a trophic effect on dopamine neurons and alleviate hemiparkinsonism in rats

Neural tissue transplantation has become an alternative treatment for Parkinson's disease (PD) and other neurodegenerative disorders. The clinical use of neural grafts as a source of dopamine for Parkinson's disease patients, although beneficial, is associated with logistical and ethical issues. Thus, alternative graft sources have been explored including polymer-encapsulated cells and nonneural cells (that is, adrenal chromaffin cells) or genetically modified cells that secrete dopamine and/or trophic factors. Although progress has been made, no current alternative graft source has ideal characteristics for transplantation. Emerging evidence suggests the importance of trophic factors in enhancing survival and regeneration of intrinsic dopaminergic neurons. It would be desirable to transplant cells that are readily available, immunologically accepted by the central nervous system and capable of producing dopamine and/or trophic factors. Sertoli cells have been shown to secrete CD-95 ligand and regulatory proteins, as well as trophic, tropic, and immunosuppressive factors that provide the testis, in part, with its "immunoprivileged" status. The present study demonstrated that transplantation of rat testis-derived Sertoli cells into adult rat brains ameliorated behavioral deficits in rats with 6-hydroxydopamine-induced hemiparkinsonism. This was associated with enhanced tyrosine hydroxylase (TH) immunoreactivity in the striatum in the area around the transplanted Sertoli cells. Furthermore, in vitro experiments demonstrated enhanced dopaminergic neuronal survival and outgrowth when embryonic neurons were cultured with medium in which rat Sertoli cells had been grown. Transplantation of Sertoli cells may provide a useful alternative treatment for PD and other neurodegenerative disorders.

Hyperactivity and hypoactivity in a rat model of Huntington's disease: the systemic 3-nitropropionic acid model

The present study proposes the use of systemic 3-nitropropionic acid (3-NP) treatment in rats as a model of Huntington's disease (HD). The systemic 3-NP model involves chronic injection of low dose intraperitoneal (i.p.) injections of 3-NP to rats once every 4 days over a period of time. Evidence from our experimental studies suggests that manipulating the number of injections can result in either increased nocturnal spontaneous locomotor activity (hyperactivity) or nocturnal akinesia (hypoactivity) [1]. For example, two injections of 3-NP (using the treatment of one injection every 4 days) result in hyperactivity, while four injections or more of 3-NP lead to hypoactivity [1]. The locomotor activity is recorded by Digiscan locomotor activity monitors [11]. The observation of these two types of locomotor activity is unique since no excitotoxin model has replicated a two-stage progression of a HD-like behavioral alteration. Most studies using excitotoxins like quinolinic acid (QA) and kainic acid (KA) have only reproduced the hyperactivity stage [4,5,7]. With the systemic 3-NP model, investigations into at least two stages of the disease are made possible. This allows for better assessment of intervention strategies such as neural transplants across different stages of the disease. The systemic 3-NP rat model is believed to be an improved animal model of HD.

Fetal grafting for Parkinson's disease: expression of immune markers in two patients with functional fetal nigral implants

In a number of centers throughout the world, fetal nigral transplantation is being performed for the treatment of Parkinson's disease (PD). Clinical results have been inconsistent. One parameter that differs among transplant studies is the degree and manner by which patients are immunosuppressed following transplantation. Indeed, the role of the immune system following fetal grafting in humans is not well understood. Recently, two patients from our open label trial that received fetal nigral implants have come to autopsy. These patients were immunosuppressed with cyclosporin for 6 mo posttransplantation and survived for a total of 18 mo postgrafting. Robust survival of grafted dopamine-containing cells was observed in both cases. Immunostaining for HLA-DR revealed a dense collection of cells within grafts from both cases. HLA-DR staining was rarely observed within the host including nongrafted regions of the striatum. A more detailed analysis of immune markers was performed in Case 2. Numerous pan macrophages, T-cells, and B-cells were observed within graft sites located in the postcommissural putamen. In contrast, staining for these immune cells was not observed within the ungrafted anterior putamen. These findings suggest that even in healthy appearing functional nigral implants, grafts are invaded by host immune cells that could compromise their long-term viability and function. Alternatively, immune cells are known to secrete trophic factors, which may ultimately favor graft survival and function. Further work is needed to understand the role of the immune system in fetal grafting.

From transplants to gene therapy for Parkinson's disease

The efficacy of fetal tissue transplants in the treatment of Parkinson's disease has been demonstrated preliminarily. However, results are short term, and have not been confirmed in prospective randomized controlled trials. Furthermore, although patients are improved, they remain severely disabled. There are several problems with the widespread clinical use of fetal tissue that make the use of molecular biological strategies more compelling. Several conceptual problems are shared by both fetal and molecular biological neuroreconstruction strategies. It is necessary to characterize the "dose" of the transplanted therapeutic agent as well as its volume of distribution. The symptoms that may improve following neuronal reconstruction are likely to be directly related to the somatotopic localization of the transplants; the duration of benefit should be long enough to be relevant in a chronic disease such as Parkinson's disease. Operative therapies that utilize gene therapy or other reconstructive neurosurgical techniques are likely to require novel clinical trial designs to demonstrate their efficacy.

Proteinase Activity during Tracheary Element Differentiation in Zinnia Mesophyll Cultures

The zinnia (Zinnia elegans) mesophyll cell culture tracheary element (TE) system was used to study proteinases active during developmentally programmed cell death. Substrate-impregnated gels and single-cell assays revealed high levels of proteinase activity in differentiating TEs compared with undifferentiated cultured cells and expanding leaves. Three proteinases (145, 28, and 24 kD) were exclusive to differentiating TEs. A fourth proteinase (59 kD), although detected in extracts from all tissues examined, was most active in differentiating TEs. The 28- and 24-kD proteinases were inhibited by thiol proteinase inhibitors, leupeptin, and N-[N-(L-3-trans-carboxirane-2-carbonyl)-L-leucyl]-agmatine (E-64). The 145- and 59-kD proteinases were inhibited by the serine proteinase inhibitor phenylmethylsulfonyl fluoride (PMSF). Extracts from the TE cultures contained sodium dodecyl sulfate-stimulated proteolytic activity not detected in control cultures. Sodium dodecyl sulfate-stimulated proteolysis was inhibited by leupeptin or E-64, but not by PMSF. Other tissues, sucrose-starved cells and cotyledons, that contain high levels of proteolytic activity did not contain TE-specific proteinases, but did contain higher levels of E-64-sensitive activities migrating as 36- to 31-kD enzymes and as a PMSF-sensitive 66-kD proteinase.

Dopaminergic transplants in patients with Parkinson's disease: neuroanatomical correlates of clinical recovery

For the past 15 years, patients with Parkinson's disease have participated in clinical trials evaluating the efficacy of intrastriatal dopamine transplants. Principally, two donor tissues have been employed, the chromaffin cells of the adrenal medulla and fetal ventral mesencephalon. The clinical response following each type of transplant has been variable. In general, the magnitude and the duration of the clinical response is greater with fetal dopaminergic neurons than with adrenal medullary grafts. Postmortem studies of patients receiving adrenal medullary grafts or fetal nigral implants provide a neuroanatomical framework for the clinical response. Adrenal grafts survive poorly following implantation into the striatum, but they are capable of inducing sprouting of host-derived fibers within a the caudate nucleus. In contrast, robust survival of fetal nigral implants can be achieved within the human brain which can provide extensive reinnervation to the parkinsonian striatum. These findings are strikingly similar to what has been seen in rodent and nonhuman primate models of PD. This paper describes the neuroanatomical correlates of dopamine brain grafting in humans and elucidates the pattern of changes seen in dopaminergic systems which are associated with clinical benefit.

Neural transplantation as an experimental treatment modality for cerebral ischemia

Cerebrovascular disease exemplifies the poor regenerative capacity of the CNS. While there are methods to prevent cerebral infarction, there is no effective therapy available to ameliorate the anatomical, neurochemical and behavioral deficits which follow cerebral ischemia. Focal and transient occlusion of the middle cerebral artery (MCA) in rodents has been reported to result in neuropathology similar to that seen in clinical cerebral ischemia. Using specific techniques, this MCA occlusion can result in a well-localized infarct of the striatum. This review article will provide data accumulated from animal studies using the MCA occlusion technique in rodents to examine whether neural transplantation can ameliorate behavioral and morphological deficits associated with cerebral infarction. Recent advances in neural transplantation as a treatment modality for neurodegenerative disorders such as Parkinson's disease, have revealed that fetal tissue transplantation may produce neurobehavioral recovery. Accordingly, fetal tissue transplantation may provide a potential therapy for cerebral infarction. Preliminary findings in rodents subjected to unilateral MCA occlusion, and subsequently transplanted with fetal striatal tissue into the infarcted striatum have produced encouraging results. Transplanted fetal tissue, assessed immunohistochemically, has been demonstrated to survive and integrate with the host tissue, and, more importantly, ameliorate the ischemia-related behavioral deficits, at least in the short term. Although, this review will focus primarily on cerebral ischemia, characterized by a localized CNS lesion within the striatum, it is envisioned that this baseline data may be extrapolated and applied to cerebral infarction in other brain areas.

Functional fetal nigral grafts in a patient with Parkinson's disease: chemoanatomic, ultrastructural, and metabolic studies

A patient with Parkinson's disease received bilateral fetal human nigral implants from six donors aged 6.5 to 9 weeks post-conception. Eighteen months following a post-operative clinical course characterized by marked improvement in clinical function, this patient died from events unrelated to the grafting procedure. Post-mortem histological analyses revealed the presence of viable grafts in all 12 implant sites, each containing a heterogeneous population of neurons and glia. Approximately 210,146 implanted tyrosine hydroxylase-immunoreactive (TH-ir) neurons were found. A greater number of TH-ir grafted neurons were observed in the right (128,162) than the left (81,905) putamen. Grafted TH-ir neurons were organized in an organotypic fashion. These cells provided extensive TH-ir and dopamine transporter-ir innervation to the host striatum which occurred in a patch-matrix fashion. Quantitative evaluations revealed that fetal nigral grafts reinnervated 53% and 28% of the post-commissural putamen on the right and left side, respectively. Grafts on the left side innervated a lesser area of the striatum, but optical density measurements were similar on both sides. There was no evidence that the implants induced sprouting of host TH-ir systems. Electron microscopic analyses revealed axo-dendritic and occasional axo-axonic synapses between graft and host. In contrast, axo-somatic synapses were not observed. In situ hybridization for TH mRNA revealed intensely hybridized grafted neurons which far exceeded TH mRNA expression within residual host nigral cells. In addition, gamma-amino butyric acid (GABA)-ergic neurons were observed within the graft that formed a dense local neuropil which was confined to the implant site. Serotonergic neurons were not observed within the graft. Cytochrome oxidase activity was increased bilaterally within the grafted post-commissural putamen, suggesting increased metabolic activity. In this regard, a doubling of cytochrome oxidase activity was observed within the grafted post-commissural putamen bilaterally relative to the non-grafted anterior putamen. The grafts were hypovascular relative to the surrounding striatum and host substantia nigra. Blood vessels within the graft stained intensely for GLUT-1, suggesting that this marker of blood--brain barrier function is present within human nigral allografts. Taken together, these data indicate that fetal nigral neurons can survive transplantation, functionally reinnervate the host putamen, establish synaptic contacts with host neurons, and sustain many of the morphological and functional characteristics of normal nigral neurons following grafting into a patient with PD.

Cyclosporine-A increases locomotor activity in rats with 6-hydroxydopamine-induced hemiparkinsonism: relevance to neural transplantation

BACKGROUND

The immunosuppressant cyclosporine-A (CsA) is the primary drug for neural transplantation in Parkinson's disease. However, little is known of its direct effects on movement disorders. Our previous observation of increased locomotor activity in normal rats injected with CsA prompted us to investigate further the effects of CsA on hemiparkinsonian rats.

METHODS

We examined the effects of CsA with 6-hydroxydopamine-induced hemiparkinsonism. The animals were randomly assigned to either intraperitoneal injections of CsA (15 mg/kg) or olive oil (the vehicle used for CsA) for 32 days. All animals were tested using the elevated body swing test, and the spontaneous and the amphetamine-induced rotational tests prior to and following the 32-day drug regimen.

RESULTS

As revealed by the elevated body swing test, CsA-treated rats had significantly higher mean percent contralateral (to the lesion) swings compared to their pretreatment level (p < 0.01) or to vehicle-treated rats at posttreatment (p < 0.005). In the spontaneous rotational test, CsA-treated rats displayed ipsilateral (to the lesion) rotations which were significantly higher than their pretreatment rotational behavior (p < 0.005) or the posttreatment rotational behavior of olive oil-treated rats (p < 0.0001). Similarly, CsA-treated rats displayed significantly more amphetamine-induced ipsilateral rotations compared to their or the olive oil-treated rats pretreatment level (p < 0.05).

CONCLUSION

Our present observations extend our previous findings on motor alterations produced by CsA on normal rats to hemiparkinsonian rats. These results taken together would suggest that CsA may interact with the locomotor effects observed following neural transplantation with adjunctive CsA immunosuppression.

CNS immunological modulation of neural graft rejection and survival

Neural transplantation therapy as a possible alternative treatment for neurological movement disorders, such as in Parkinson's disease (PD), has accentuated research interest on the immune status of the central nervous system (CNS). Most animal studies concerned with neural transplantation for the treatment of PD have utilized dopamine (DA) neurons from tissues of the embryonic ventral mesencephalon. Rat embryonic DA neurons, grafted either as solid blocks or dissociated into a cell suspension and stereotaxically injected intraparenchymally into a rat lesion model of PD, have been shown to survive and form connections with the host brain, and ameliorate the behavioral deficits of PD. Similarly, studies on nonhuman primate models of PD provide considerable support for neural transplantation of DA neurons as an experimental clinical procedure for the treatment of PD. To this end, experimental clinical trials have been centered upon transplantation of the embryonic ventral mesencephalic cells for PD patients. Although not conclusive, the findings from clinical studies have provided some evidence that most patients with marked increases in fluorodopa uptake (indicating graft survival) have been immunosuppressed. Furthermore, immune reactions have been observed in rats xenografted with human embryonic tissue. Of note, embryonic ventral mesencephalic tissues compared to adult tissues produce better morphological and long-lasting behavioral amelioration of the neurobehavioral deficits of PD, thus advocating the use of grafts from young donors (embryo) to circumvent the CNS immune rejection. The possible graft rejection due to CNS immune reactions, coupled with the social and ethical problems surrounding the use of embryonic neural tissue, and the logistical problems concerning tissue availability have prompted the development of alternative sources of DA-secreting cells. To circumvent these obstacles, several methods have been suggested including the use of immunosuppressants such as Cyclosporine-A, transplantation of autografts, polymer-encapsulated DA-secreting cells, co-culturing and co-transplantation of DA-secreting cells with microcarrier beads, with Sertoli cells, or with fragments of a monoclonal antibody that can mask the MHC class I antigens, and genetically modifying cells that can withstand CNS immune reactions. Some of these techniques allow transplantation of allograft (same species transplantation), or even xenograft (cross species transplantation) without immunosuppression of the recipient. We discuss recent CNS immunosuppression techniques that pose some promise for enhanced survival of neural grafts. When possible, advantages and disadvantages of each method are presented. Hopefully, such critical analysis of different immunosuppression techniques will produce innovated ideas that will lead to a better understanding of CNS immune response and its modulatory function on graft rejection and survival.

Functional fetal nigral grafts in a patient with Parkinson's disease: chemoanatomic, ultrastructural, and metabolic studies

A patient with Parkinson's disease received bilateral fetal human nigral implants from six donors aged 6.5 to 9 weeks post-conception. Eighteen months following a post-operative clinical course characterized by marked improvement in clinical function, this patient died from events unrelated to the grafting procedure. Post-mortem histological analyses revealed the presence of viable grafts in all 12 implant sites, each containing a heterogeneous population of neurons and glia. Approximately 210,146 implanted tyrosine hydroxylase-immunoreactive (TH-ir) neurons were found. A greater number of TH-ir grafted neurons were observed in the right (128,162) than the left (81,905) putamen. Grafted TH-ir neurons were organized in an organotypic fashion. These cells provided extensive TH-ir and dopamine transporter-ir innervation to the host striatum which occurred in a patch-matrix fashion. Quantitative evaluations revealed that fetal nigral grafts reinnervated 53% and 28% of the post-commissural putamen on the right and left side, respectively. Grafts on the left side innervated a lesser area of the striatum, but optical density measurements were similar on both sides. There was no evidence that the implants induced sprouting of host TH-ir systems. Electron microscopic analyses revealed axo-dendritic and occasional axo-axonic synapses between graft and host. In contrast, axo-somatic synapses were not observed. In situ hybridization for TH mRNA revealed intensely hybridized grafted neurons which far exceeded TH mRNA expression within residual host nigral cells. In addition, gamma-amino butyric acid (GABA)-ergic neurons were observed within the graft that formed a dense local neuropil which was confined to the implant site. Serotonergic neurons were not observed within the graft. Cytochrome oxidase activity was increased bilaterally within the grafted post-commissural putamen, suggesting increased metabolic activity. In this regard, a doubling of cytochrome oxidase activity was observed within the grafted post-commissural putamen bilaterally relative to the non-grafted anterior putamen. The grafts were hypovascular relative to the surrounding striatum and host substantia nigra. Blood vessels within the graft stained intensely for GLUT-1, suggesting that this marker of blood--brain barrier function is present within human nigral allografts. Taken together, these data indicate that fetal nigral neurons can survive transplantation, functionally reinnervate the host putamen, establish synaptic contacts with host neurons, and sustain many of the morphological and functional characteristics of normal nigral neurons following grafting into a patient with PD.

Free radical damage and oxidative stress in Huntington's disease

Bioenergetic defects and oxidative stress may be critical links in an excitotoxic mechanism of neuronal death. Oxidative stress, a condition describing the production of oxygen radicals beyond a threshold for proper antioxidant neutralization, has been implicated as a pathologic condition in several neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. In addition, oxygen radicals are known to be important mediators in acute pathologies, in the theory of senescence, cancer, as well as our healthy immune system. Although free radicals may have a special chemical nature which allows them to perform important cellular functions, they are a damaging entity whose reactivity may play a part in the development of cellular compromises that can kill a neuron. In this review, the free radicals in biological systems, the defense systems against them, and the damaging interactions, i.e., oxidative stress, which they confer are discussed. The descriptions provided raise the hypothesis that an imbalance between the production and removal of radicals would be abrasive on a neuron. Accordingly, the neurodegeneration initially caused by gene mutation in Huntington's disease may be further worsened by free radical damage underlied by oxidative stress. This article reviews existing data on the free radical damage and the oxidative stress, which are primarily directed towards Parkinson's disease and Alzheimer's disease, and whenever possible relates such mechanisms to Huntington's disease.

Fetal nigral transplantation as a therapy for Parkinson's disease

Fetal nigral grafts have been demonstrated to survive, secrete dopamine, form synaptic connections with host neurons, and reverse behavioral disturbances in experimental models of parkinsonism. These findings suggest that fetal nigral grafting may be a useful therapy for patients with Parkinson's disease (PD). Recent preliminary clinical trials of transplantation in PD have shown increased striatal fluorodopa uptake (measured using positron emission tomography) and clinical benefit in some patients. An autopsy study of one patient who had received fetal nigral transplants demonstrated robust graft survival and striatal reinnervation, with no evidence of host-derived sprouting or immune rejection. The development of a successful clinical transplantation program depends on a careful consideration of the transplantation variables and the related long-term risks and benefits to the patients.

(-)-nicotine protects against systemic kainic acid-induced excitotoxic effects

(-)-Nicotine was shown to produce in vivo protection against neurobehavioral effects caused by systemically administered kainic acid (KA), an excitotoxin that has been widely used to induce temporal lobe convulsions including "wet dog shakes" in experimental animals. Rats pretreated with (-)-nicotine (0.5 mg/kg sc) 15 min before receiving KA (12.0 mg/kg sc) exhibited a marked reduction (P < 0.5) in the number of wet dog shakes when compared to saline-pretreated rats. Similarly, little visible brain damage was found in the (-)-nicotine-pretreated rats, but a widespread reduction in acetylcholinesterase-positive neurons was noted in the hippocampal areas of the saline-pretreated animals. While the mechanism of neuroprotection of (-)-nicotine is still not known, these findings suggest that (-)-nicotine may act as a therapeutic agent for putative excitotoxin-mediated disorders.