Fetal Mesencephalic Transplants Research Articles

α-Synuclein propagates from mouse brain to grafted dopaminergic neurons and seeds aggregation in cultured human cells

Post-mortem analyses of brains from patients with Parkinson disease who received fetal mesencephalic transplants show that α-synuclein-containing (α-syn-containing) Lewy bodies gradually appear in grafted neurons. Here, we explored whether intercellular transfer of α-syn from host to graft, followed by seeding of α-syn aggregation in recipient neurons, can contribute to this phenomenon. We assessed α-syn cell-to-cell transfer using microscopy, flow cytometry, and high-content screening in several coculture model systems. Coculturing cells engineered to express either GFP- or DsRed-tagged α-syn resulted in a gradual increase in double-labeled cells. Importantly, α-syn-GFP derived from 1 neuroblastoma cell line localized to red fluorescent aggregates in other cells expressing DsRed-α-syn, suggesting a seeding effect of transmitted α-syn. Extracellular α-syn was taken up by cells through endocytosis and interacted with intracellular α-syn. Next, following intracortical injection of recombinant α-syn in rats, we found neuronal uptake was attenuated by coinjection of an endocytosis inhibitor. Finally, we demonstrated in vivo transfer of α-syn between host cells and grafted dopaminergic neurons in mice overexpressing human α-syn. In summary, intercellularly transferred α-syn interacts with cytoplasmic α-syn and can propagate α-syn pathology. These results suggest that α-syn propagation is a key element in the progression of Parkinson disease pathology.

Neural transplantation in Parkinson's disease and its effects on rest tremor: a review of the literature.

The transplantation of fetal mesencephalic dopaminergic tissue into the striatum of parkinsonian (PD) patients is an experimental therapeutic approach. The target population for this treatment are advanced, predominantly akinetic-rigid patients with therapy-associated complications, and not tremor-dominant PD patients. Based on a review of selected published data, no specific beneficial effect of fetal mesencephalic transplantation in PD patients was reported on the cardinal symptom rest tremor. On the one hand, this might be the result of a lack of efficacy of this treatment with respect to tremor; on the other hand, PD patients with predominant tremor may have a better prognosis with respect to motor function and therefore might not reach the advanced akinetic-rigid stage, which makes them eligible for neural transplantation. Rest-tremor dominant PD patients have not undergone fetal cell grafting; therefore its effect on rest tremor is unknown.

Gene therapy for Parkinson's disease: early data

Parkinson's disease is the second most common neurodegenerative disorder, affecting at least 1% of people above the age of 65 years, a proportion that increases with age. The introduction of replacement therapy with levodopa and, more recently, various adjunct drugs has substantially improved survival and quality of life. However, these therapies are associated with several long-term complications that can limit the tolerated dose. None of the available drugs has a convincing effect on the inexorable progression of the disease. Surgical approaches, such as deep-brain stimulation of the subthalamic nucleus, are effective 1 Deuschl G Schade-Brittinger C Krack P et al. A randomized trial of deep-brain stimulation for Parkinson's disease. N Engl J Med. 2006; 355: 896-908 Crossref PubMed Scopus (2018) Google Scholar but technically complex, and continuing care from an expert team is needed. Although there is interest in cell-based therapies, double-blind controlled trials of human fetal mesencephalic transplantation were disappointing. 2 Freed CR Greene PE Breeze RE et al. Transplantation of embryonic dopamine neurons for severe Parkinson's disease. N Engl J Med. 2001; 344: 710-719 Crossref PubMed Scopus (1968) Google Scholar , 3 Olanow CW Goetz CG Kordower JH et al. A double-blind controlled trial of bilateral fetal nigral transplantation in Parkinson's disease. Ann Neurol. 2003; 54: 403-414 Crossref PubMed Scopus (1244) Google Scholar Several gene-therapy approaches have been suggested or are in development, ranging from those that attempt to restore dopamine synthetic capacity 4 Bankiewicz KS Forsayeth J Eberling JL et al. Long-term clinical improvement in MPTP-lesioned primates after gene therapy with AAV-hAADC. Mol Ther. 2006; 14: 564-570 Summary Full Text Full Text PDF PubMed Scopus (235) Google Scholar , 5 Pardridge WM Tyrosine hydroxylase replacement in experimental Parkinson's disease with transvascular gene therapy. NeuroRx. 2005; 2: 129-138 Crossref PubMed Scopus (83) Google Scholar to those that protect against cell death with trophic factors, 6 Kordower JH Herzog CD Dass B et al. Delivery of neurturin by AAV2 (CERE-120)-mediated gene transfer provides structural and functional neuroprotection and neurorestoration in MPTP-treated monkeys. Ann Neurol. 2006; 60: 706-715 Crossref PubMed Scopus (216) Google Scholar to molecules that interfere with the aberrant protein aggregation in Parkinson's disease. 7 Lo Bianco C Schneider BL Bauer M et al. Lentiviral vector delivery of parkin prevents dopaminergic degeneration in an α-synuclein rat model of Parkinson's disease. Proc Natl Acad Sci USA. 2004; 101: 17510-17515 Crossref PubMed Scopus (270) Google Scholar , 8 Mochizuki H Yamada M Mizuno Y Parkin gene therapy for α-synucleinopathy: a rat model of Parkinson's disease. Parkinsonism Relat Disord. 2006; 12: S107-S109 Summary Full Text Full Text PDF Scopus (6) Google Scholar Safety and tolerability of gene therapy with an adeno-associated virus (AAV) borne GAD gene for Parkinson's disease: an open label, phase I trialAAV-GAD gene therapy of the subthalamic nucleus is safe and well tolerated by patients with advanced Parkinson's disease, suggesting that in-vivo gene therapy in the adult brain might be safe for various neurodegenerative diseases. Full-Text PDF

In Vivo PET Measurements with [11C]PE2I to Evaluate Fetal Mesencephalic Transplantations to Unilateral 6-OHDA-Lesioned Rats

Positron emission tomography (PET) is a useful tool to assess and visualize neurotransmissions in vivo. In this study, we performed repeated PET scans with [11C]PE2I, a tracer of the dopamine transporter, to evaluate the alteration of the expression of dopamine (DA) transmission component after a fetal mesencephalic transplantation. The fetal mesencephalic cells were transplanted into the striatum of unilateral 6-OHDA-lesioned rats. PET scans with [11C]PE2I were performed to evaluate the DA transporter before and 2 and 4 weeks after the transplantation. Rotation behavior tests, in vitro autoradiography, measurements of DA contents in the striatum by high-performance liquid chromatography (HPLC), and tyrosine hydroxylase (TH) immunohistological examinations were performed at the same time points and examined for their relationship to changes in the dopamine transporter. The number of ipsilateral rotations induced by methamphetamine injections decreased. DA contents in the striatum measured with HPLC significantly increased. In the PET study, the binding potential of [11C]PE2I increased at 4 weeks. The results of the in vitro autoradiography study corresponded with those of the PET study. The degrees of the change in the binding potentials correlated with those of the numbers of rotations in the behavioral study and the DA contents in the striatum. In the histological examination, TH-positive cells with axons were observed at 2 and 4 weeks after the transplantation. As the dopamine transporter exists only in the axon terminal of DA neurons, these results suggested that PET measurements of [11C]PE2I binding indicated not only survival, but maturity and functioning of the transplanted cells. Repeated PET measurements of DA transporters are a useful tool in assessing the effectiveness of neural transplantations.

Stem cell treatment for Parkinsonʼs disease: an update for 2005

The hallmark pathologic feature of Parkinson's disease is loss of melanized dopaminergic neurons within the substantia nigra pars compacta coupled with depletion of striatal dopamine. This is responsible for the major motor features of the disease. Whereas dopaminergic replacement therapy is effective in the early stages of the illness, chronic treatment is associated with motor complications and development of features that do not respond to levodopa therapy. Development of cellular therapies offers the potential to provide more effective treatment for the disease without motor complications. Two clinical trials of fetal nigral transplantation failed to meet their primary endpoint and were complicated by the development of dyskinesia that persisted after withdrawal of levodopa ('off-medication' dyskinesia). However, recent studies suggest that both the limited clinical response and off-medication dyskinesia may be related to partial, but incomplete, dopaminergic reinnervation of the striatum and that both might be improved by transplantation of more dopamine neurons. Stem cells offer the potential to provide a virtually unlimited supply of optimized dopaminergic neurons that can provide enhanced benefits in comparison to fetal mesencephalic transplants. Stem cells have now been shown to be capable of differentiating into dopamine neurons that provide benefits following transplantation in animal models of Parkinson's disease. However, cell survival and behavioral responses are limited. There have been numerous advances in enhancing the yield of dopamine neurons from stem cells, and promoting their survival and consequent clinical effects. Stem cells offer great promise as a therapy for Parkinson's disease, but numerous hurdles remain to be overcome with stem cell therapy. The adverse event profile of transplantation must be determined, and societal and ethical issues addressed. As Parkinson's disease involves degeneration of both dopaminergic and non-dopaminergic neurons, it also remains to be determined if transplantation of even the ideal dopamine neuron will improve non-dopaminergic features of the disease or provide benefits superior to existing therapies.

Terapia celular y otras estrategias neurorregenerativas en la enfermedad de Parkinson (I)

To review, from a mainly clinical standpoint, the different strategies applied to regenerate or restore the nigrostriatal dopaminergic system in Parkinson's disease. This first part focuses on the results of adrenal medulla and human fetal mesencephalic transplants, and a second part will address transplants of other cell types, administration of trophic factors, and gene therapy.Adrenal medulla transplants were abandoned because of their inconsistent results and high morbidity. Although fetal mesencephalic transplantation can produce long-term restoration of striatal dopamine deficiency, this neurochemical effect is clinically inadequate in presence of progressive neuronal loss. Other strategies with similar 'dopaminergic' action mechanism are not a therapeutic option in this setting.The objective of neuroregenerative therapy for Parkinson's disease should include trophic restoration of damaged neuronal systems, since improvement in striatal dopaminergic function is not sufficient. After the recent failure of the direct (intraventricular or intraputaminal) administration of glial cell line-derived neurotrophic factor (GDNF), attention of researchers has focused on indirect methods, including transplantation of GDNF-producing cells (carotid body cell aggregates or different genetically modified cells, including stem cells), and in vivo gene therapy.

Sustained pharmacological inhibition of nitric oxide synthase does not affect the survival of intrastriatal rat fetal mesencephalic transplants

The objective of the present study was to investigate the potential role of the free radical nitric oxide (NO) in the development of fetal rat mesencephalic neurons grafted in a 6-hydroxydopamine (6-OHDA) lesioned rat model of Parkinson's disease. First, using nitric oxide synthase (NOS)-immunocytochemistry and reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry, we investigated the presence of the neuronal isoform of NOS (nNOS) in intrastriatal mesencephalic grafts. During the course of the experiment (16 weeks) an increase in the staining intensity and the number of nNOS/NADPH-d positive cells within the grafts was observed, as well as a gradual maturation of dopaminergic neurons. In addition, within both the host striatal and grafted mesencephalic tissue, a NO-dependent accumulation of cyclic guanosine monophosphate (cGMP) was detected, indicating the presence of guanylate cyclase, i.e., the target-enzyme for NO. Secondly, to determine the impact of NO on the survival of grafted dopaminergic neurons, 6-OHDA lesioned rats received mesencephalic grafts and were subsequently treated with the competitive NOS-inhibitor N ω -nitro- l-arginine methylester ( l-NAME). After chronic treatment for 4 weeks, tyrosine hydroxylase immunocytochemistry revealed no apparent differences between the survival of grafted dopaminergic neurons in control- or l-NAME treated animals, respectively. As the maturation of grafted dopaminergic neurons coincides with a gradual increase in the expression of nNOS within the graft and since dopaminergic cell numbers are not changed upon administration of l-NAME, it is concluded that endogenously produced and potentially toxic NO does not affect the survival of grafted fetal dopaminergic neurons.

Neurosurgical horizons in Parkinson's disease

Based on recent neuroanatomic and physiologic discoveries, neurosurgical therapies may increasingly complement and extend pharmacologic management of Parkinson's disease. Procedures showing promise include subthalamotomy and pallidotomy; thalamic electrical stimulation may also offer application for tremor control. Transplantation of adrenal chromaffin cells has not been associated with consistent long-term improvement in most patients, and fetal mesencephalic transplantation remains controversial. Trophic factors that may be pivotal to cellular repair and survival of transplanted tissue have potential therapeutic roles when purified and perfused centrally or when the cells that produce the factors are transplanted.

Downregulation of muscarinic receptors in the rat caudate-putamen after lesioning of the ipsilateral nigrostriatal dopamine pathway with 6-hydroxydopamine (6-OHDA): normalization by fetal mesencephalic transplants

The autoradiographic distribution and density of muscarinic receptors was studied in the neostriatum of rats with long-term unilateral 6-hydroxydopamine (6-OHDA) lesions of the nigrostriatal dopaminergic pathway and in lesioned rats who had additionally received embryonic substantia nigra grafts in the dopamine denervated striatum. Muscarinic receptors were labeled with [ 3H]quinuclidinyl benzilate (QNB), M 1 receptors were directly labeled with [ 3H]pirenzepine (PZ) and non-M 1 receptors were labeled by the competition of 100 nM PZ with [ 3H]QNB. The density and distribution of muscarinic receptors were directly compared to the sodium-dependent, high-affinity, choline uptake sites as labeled with [ 3H]hemicholinium-3 (HC-3). In the 6-OHDA-lesioned animals, there was a 25% reduction in muscarinic receptors labeled with [ 3H]QNB. Subtype analysis showed that there was a reduction of both M 1 (−26%) and non-M 1 (−33%) receptors. A normal density of both muscarinic receptor populations was found in animals with successful transplants. Saturation analysis demonstrated that the changes, in muscarinic receptor density, were due to a change in receptor number ( B max) and not affinity ( K d). There was no significant change in [ 3H]HC-3 binding in the 6-OHDA-lesioned or transplanted animals, indicating that alterations in muscarinic receptors were not due to transynaptic degeneration of striatal cholinergic interneurons. The findings of downregulation of muscarinic receptors following long-term dopamine denervation and the subsequent normalization of muscarinic receptor density after fetal mesencephalic transplantation suggests that transplanted substantia nigra cells are able to restore inhibitory control on striatal cholinergic interneurons.

Decrease of behavioral and biochemical denervation supersensitivity of rat striatum by nigral transplants

The effect of fetal mesencephalic transplants on dopamine receptor supersensitivity has been studied behaviorally and biochemically in rats with a unilateral lesion of the nigrostriatal pathway. Female rats were lesioned with 6-hydroxydopamine in the left substantia nigra. At least one month later they were tested with apomorphine (0.25 mg/kg, s.c.), amphetamine (5mg/kg, s.c.), LY 171555 (D 2 agonist) (0.5 mg/kg, i.p.) and CY 208243 (D 1 agonist) (0.5 mg/kg, s.c.). A suspension containing approximately1.5 × 10 6 cells from the ventral mesencephalon of rat embryos was distributed in three sites in a triangular fashion in the center of the denervated striatum. Six months later, grafted dopamine neurons reinnervated the medial part of the dorsal striatum, increased the dopamine level and reversed the rotational asymmetry evoked by amphetamine. Apomorphine given four months post-transplant still elicited contraversive circling but the number of turns was reduced. Circling evoked six months post-transplant by CY 208243 or LY 171555 was significantly less in grafted rats than in lesioned non-grafted rats. The density of dopaminergic receptors in the striatum of grafted and lesioned rats was examined by autoradiography by means of in vitro binding with [ 3H]SCH 23390 for D 1 receptors and [ 3H]spiperone for D 2 receptors. The results show that intrastriatal nigral transplants decrease the supersensitivity of the D 2 receptors and to a lesser extent of the D 1 receptors. Normalization of D 2 receptors may explain the decrease of behavioral supersensitivity following administration of apomorphine and D 2 agonist in grafted rats. D 1 receptors were less affected by the lesion and also less normalized than D 2 receptors by the transplants. D 1 changes localized in other structures of the basal ganglia may explain the decreased circling to apomorphine and D 1 agonists in grafted rats.