Transplantation of cryopreserved human embryonal carcinoma-derived neurons (NT2N cells) promotes functional recovery in ischemic rats

Human bone marrow stem cells exhibit neural phenotypes and ameliorate neurological deficits after grafting into the ischemic brain of rats

There is now evidence to suggest that bone marrow mesenchymal stem cells (MSCs) not only differentiate into mesodermal cells, but can also adopt the fate of endodermal and ectodermal cell types. In this study, we addressed the hypotheses that human MSCs can differentiate into neural cells when implanted in the brain and restore sensorimotor function after experimental stroke. Purified human MSCs were grafted into the cortex surrounding the area of infarction 1 week after cortical brain ischemia in rats. Two and 6 weeks after transplantation animals were assessed for sensorimotor function and then sacrificed for histological examination. Ischemic rats that received human MSCs exhibited significantly improved functional performance in limb placement test. Histological analyses revealed that transplanted human MSCs expressed markers for astrocytes (GFAP(+)), oligodendroglia (GalC(+)), and neurons (beta III(+), NF160(+), NF200(+), hNSE(+), and hNF70(+)). The morphological features of the grafted cells, however, were spherical in nature with few processes. Therefore, it is unlikely that the functional recovery observed by the ischemic rats with human MSC grafts was mediated by the integration of new "neuronal" cells into the circuitry of the host brain. The observed functional improvement might have been mediated by proteins secreted by transplanted hMSCs, which could have upregulated host brain plasticity in response to experimental stroke.

Neuronal formation of free radicals plays a minor role in hypoxic cell death in human NT2-N neurons

Free radicals are suggested to play an important role in hypoxic-ischemic neuronal death. However, the importance in human disease is not known. Furthermore, whether posthypoxic free radical formation mainly occurs in endothelium and neutrophils, or whether neuronal production is important, is not finally determined. To study this we differentiated human Ntera2 teratocarcinoma cells into postmitotic NT2-N neurons and exposed them to free radicals, hypoxia, or oxygen and glucose deprivation. These cells are devoid of nitric oxide synthase, and we hypothesized that free radicals are important mediators downstream of N-methyl-D-aspartate stimulation. Production of free radicals, evaluated with the fluorescent dyes dihydrorhodamine and 2',7'-dichlorodihydrofluorescein, was significantly higher in neurons deprived of oxygen and glucose after 40 min of reoxygenation than in normoxic cells. The antioxidant trolox, the flavonoid quercetin, thiopental, and the N-methyl-D-aspartate-glutamate receptor antagonist MK-801 reduced the formation of free radicals. Treatment with the flavonoid rutin (86 +/- 16% of hypoxic cells without drug, p < 0.01), trolox (86 +/- 20%, p < 0.01), and MK-801 (57 +/- 12%, p < 0.01) reduced lactate dehydrogenase release after 6 h of hypoxia. Trolox, salicylate, and quercetin also significantly reduced lactate dehydrogenase release after 3 h of oxygen and glucose deprivation. The protection offered by these antioxidants was, however, limited compared with the effect of MK-801. We conclude that oxygen and glucose deprivation causes a moderate increase in the formation of free radicals in NT2-N neurons that can be inhibited by antioxidants and by blocking of the N-methyl-D-aspartate-glutamate receptor. Although MK-801 conveys profound protection, antioxidants provide only a limited improvement in neuronal survival. Thus in this model, mechanisms downstream of the N-methyl-D-aspartate-glutamate receptor other than free radicals and nitric oxide have to be invoked.

Single-Cell Antisense RNA Amplification and Microarray Analysis as a Tool for Studying Neurological Degeneration and Restoration

Neurodegenerative diseases typically affect subpopulations of neurons. Characterizing these vulnerable cells and identifying the factors that make them susceptible to damage while neighboring cells remain resistant are essential to the understanding of molecular pathogenesis that underlies neurodegenerative diseases. Classically, molecular analysis of the central nervous system involves the identification and isolation of an anatomic region of interest; next, the relevant tissue is pulverized, and the resulting homogenate is analyzed. Although this method provides useful data, its effectiveness diminishes when used in areas of high cellular diversity or in instances in which one cell type is lost as a consequence of selective cell death or quiescence. A technique that affords the ability to assess molecular events in a very precise anatomical site would provide a powerful tool for this research discipline. In this review, we discuss the amplification of messenger RNA from single neural cells and the subsequent use of the RNA to probe DNA microarrays in an effort to create cell-specific molecular profiles. Specifically, recent work in single-cell expression profiling in Alzheimer's and Huntington's diseases is discussed. We also review some new work with neural stem cells and their application to restorative neurobiology. Finally, we discuss the use of cell-specific molecular profiles to better understand the basics of neuronal cell biology.

hNT neurons delay onset of motor deficits in a model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a degenerative motor neuron disease that manifests as a progressive muscular weakness leading to paralysis and death. Because of the diffuse nature of the motor neuron death, this disease is not considered a good candidate for treatment through neural transplantation. The purpose of this study was to show that transplantation of human neuron-like cells (hNT neurons) into the spinal cord of a transgenic ALS mouse model would improve motor deficits. The hNT neurons were transplanted bilaterally into L4-L5 spinal cord of the transgenic mice ( approximately 8 weeks of age), and the animals were evaluated on health and behavioral measures. The animals were perfused, and immunohistochemistry was performed to identify the transplanted cells. Transplantation of the hNT neurons into the spinal cord delayed the onset of motor behavioral symptoms. This was the first demonstration that even localized transplantation of neural cells directly into the parenchyma could improve motor function in an ALS model. Further study is needed to delineate the mechanism underlying these effects. This therapeutic approach has the potential to restore neural transmission, thereby improving quality of life for the ALS patient and possibly extend life expectancy.

In vitro induction and in vivo expression of bcl-2 in the hNT neurons

Bcl-2 encodes membrane-associated proteins that suppress programmed cell death in cells of various origins. Compelling evidence suggests that bcl-2 is also involved in neuronal differentiation and axonal regeneration. The human Neuro-Teratocarcinoma (hNT) neurons constitute a terminally differentiated human neuronal cell line that is derived from the Ntera-2/clone D1 (NT2) precursors upon retinoic acid (RA) treatment. After transplantation into the central nervous system (CNS), the hNT neurons survive, engraft, maintain their neuronal identity, and extend long neurite outgrowth. We were particularly interested in the intracellular determinants that confer these post-transplant characteristics to the hNT neurons. Thus, we asked whether the hNT neurons express bcl-2 after transplantation into the rat striatum and if RA induction of the neuronal lineage is mediated by bcl-2. The grafted hNT neurons were first identified using three different antibodies that recognize human-specific epitopes, anti-hMit, anti-hNuc, and NuMA. After a 1-month post-transplant survival time, NuMA immunostaining revealed that 12% of the hNT neurons survived the transplantation. These neurons extended long neuritic processes within the striatum, as demonstrated using the human-specific antibody against the midsize neurofilament subunit HO14. Importantly, we found that 85% of the implanted hNT neurons expressed bcl-2 and that the in vitro induction of the neuronal lineage from the NT2 precursors with RA resulted in an upregulation of bcl-2 expression. Together, these data suggest that the differentiation of the hNT neurons to a neuronal lineage could be mediated at least partially by bcl-2.

Serial [18F] fluorodeoxyglucose positron emission tomography after human neuronal implantation for stroke

OBJECTIVE

There is no known effective treatment for chronic stroke. In this report, we used positron emission tomography (PET) with [18F]fluorodeoxyglucose (FDG) to map the metabolic brain response to neuronal cell implantation in the first human neuroimplantation trial for stroke.

METHODS

Twelve patients (nine men, three women; mean age +/- standard deviation, 60.8+/-8.3 yr) with chronic basal ganglia infarction and persistent motor deficit underwent FDG PET within 1 week before and 6 and 12 months after stereotactic implantation of human neuronal cells. Serial neurological evaluations during a 52-week postoperative period included the National Institutes of Health stroke scale and the European stroke scale.

RESULTS

Alterations in glucose metabolic activity in the stroke and surrounding tissue at 6 and 12 months after implantation correlated positively with motor performance measures.

CONCLUSION

FDG PET performed as part of an initial open-label human trial of implanted LBS-Neurons (Layton BioScience, Sunnyvale, CA) for chronic stroke demonstrates a relationship between relative regional metabolic changes and clinical performance measures. These preliminary findings suggest improved local cellular function or engraftment of implanted cells in some patients.

Differentiation of human dopamine neurons from an embryonic carcinomal stem cell line

Previous studies from this laboratory have demonstrated that fibroblast growth factor 1 together with a number of co-activator molecules (dopamine, TPA, IBMX/forskolin), will induce the expression of the catecholamine biosynthetic enzyme tyrosine hydroxylase (TH) in 10% of human neurons (hNTs) derived from the NT2 cell line [10]. In the present study, we found that TH induction was increased to nearly 75% in hNTs when cells were permitted to age 2 weeks in culture prior to treatment with the differentiation cocktail. This high level of TH expression was sustained 7 days after removal of the differentiating agents from the media. Moreover, the induced TH present in these cells was enzymatically active, resulting in the production of low levels of dopamine (DA) and its metabolite DOPAC. These findings suggest that hNTs may provide an important tissue culture model for the study of factors regulating TH gene expression in human neurons. Moreover, hNTs may serve, in vivo, as a source of human DA neurons for use in transplantation therapies.

Resolution of stroke deficits following contralateral grafts of conditionally immortal neuroepithelial stem cells

BACKGROUND AND PURPOSE

Grafts of MHP36 cells have previously been shown to reduce dysfunction after global ischemia in rats. To test their efficacy after focal ischemia, MHP36 cells were grafted 2 to 3 weeks after transient intraluminal middle cerebral artery occlusion (tMCAO) in rats.

METHODS

MHP36 cells were implanted into the hemisphere contralateral to the lesion, with 8 deposits of 3 microL of cell suspension (25 000 cells per microliter). Sham grafted rats received equivalent volumes of vehicle. Three groups, sham-operated controls (n=11), MCAO+sham grafts (n=10), and MCAO+MHP36 grafts (n=11), were compared in 3 behavioral tests.

RESULTS

In the bilateral asymmetry test, MCAO+MHP36 grafted rats exhibited neglect before grafting but subsequently showed no significant dysfunction, whereas MCAO+sham grafted rats showed stable sensorimotor deficits over 18 weeks relative to controls. MCAO+sham grafted rats demonstrated spontaneous motor asymmetry and increased rotational bias after injection of dopamine agonists. MCAO+MHP36 and control groups exhibited no bias in either spontaneous or drug-induced rotation. In contrast to motor recovery, MCAO+MHP36 grafted rats showed no improvement relative to MCAO+sham grafted rats in spatial learning and memory in the water maze. MCAO produced large striatal and cortical cavitations in both occluded groups. Lesion volume was significantly reduced (P<0.05) in the MCAO+MHP36 grafted group. The majority of MHP36 cells were identified within the intact grafted hemisphere. However, MHP36 cells were also seen in the cortex, striatum, and corpus callosum of the lesioned hemisphere.

CONCLUSIONS

MHP36 cells may improve functional outcome after MCAO by assisting spontaneous reorganization in both the damaged and intact hemispheres.

Restoration of function by neural transplantation in the ischemic brain

Stroke remains a major brain disorder that often renders patients severely impaired and permanently disabled. There is no available treatment for reversing these deficits. Hippocampal, striatal and cortical grafting studies demonstrate that fetal cells/tissues, immortalized cells, and engineered cell lines can survive grafting into the ischemic adult brain, correct neurotransmitter release, establish both afferent and efferent connections with the host brain, and restore functional and cognitive deficits in specific models of stroke. The success of neural transplantation depends on several factors: the stroke model (location, extent, and degree of infarction), the donor cell viability and survival at pre- and post-transplantation, and the surgical technique, among others. Further exploitation of knowledge of neural transplantation therapy already available from our experience in treating Parkinson's disease needs to be critically considered for stroke therapy. While the consensus is to create a functional neuronal circuitry in the damaged host brain, there is growing evidence that trophic action of the grafts and host, as well as exogenous application of trophic factors may facilitate functional recovery in stroke. Current treatment modules, specifically that of rehabilitative medicine, should also be explored with neural transplantation therapy. However, validation of neural transplantation and any other treatment for stroke should be critically assessed in laboratory experiments and limited clinical trials. No direct treatment is recognized as safe and effective for reversing the stroke-induced brain damage and functional/cognitive deficits. The first clinical trial of neural transplantation in stroke patients is a mile-stone in stroke therapy, but subsequent large-scale trials should be approached with caution.

Neurobiology of human neurons (NT2N) grafted into mouse spinal cord: implications for improving therapy of spinal cord injury

Emerging data suggest that current strategies for the treatment of spinal cord injury might be improved or augmented by spinal cord grafts of neural cells, and it is possible that grafted neurons might have therapeutic potential. Thus, here we have summarized recent studies of the neurobiology of clonal human (NT2N) neurons grafted into spinal cord of immunodeficient athymic nude mice. Postmitotic human NT2N neurons derived in vitro from an embryonal carcinoma cell line (NT2) were transplanted into spinal cord of neonatal, adolescent and adult nude mice where they became integrated into the host gray and white matter, did not migrate from the graft site, and survived for > 15 months after implantation. The neuronal phenotype of the grafted NT2N cells was similar in gray and white matter regardless of host age at implantation, and some of the processes extended by the transplanted NT2N neurons became ensheathed by oligodendrocytes. However, there were consistent differences between NT2N processes traversing white versus gray matter. Most notably, NT2N processes with a trajectory in white matter extended over much longer distances (some for > 2 cm) than those confined to gray matter. Thus, NT2N neurons grafted into spinal cord of nude mice integrated into gray as well as white matter, where they exhibited and maintained the morphological and molecular phenotype of mature neurons for > 15 months after implantation. Also, the processes extended by grafted NT2N neurons differentially responded to cues restricted to gray versus white matter. Further insight into the neurobiology of grafted human NT2N neurons in the normal and injured spinal cord of experimental animals may lead to novel and more effective strategies for the treatment of spinal cord injury.

Neural transplantation in spinal cord injury

Although medical advancements have significantly increased the survival of spinal cord injury patients, restoration of function has not yet been achieved. Neural transplantation has been studied over the past decade in animal models as a repair strategy for spinal cord injury. Although spinal cord neural transplantation has yet to reach the point of clinical application and much work remains to be done, reconstructive strategies offer the greatest hope for the treatment of spinal cord injury in the future. This article presents the scientific basis of neural transplantation as a repair strategy and reviews the current status of neural transplantation in spinal cord injury.

Hyperbaric oxygen therapy for treatment of postischemic stroke in adult rats

The efficacy of hyperbaric oxygen (HBO) therapy for treatment of stroke remains to be validated in the laboratory. We report here that adult rats subjected to occlusion of the middle cerebral artery and subsequently exposed to HBO (3 atm, 2 x 90 min at a 24-h intervals; animals terminated shortly after the second treatment) or hyperbaric pressure (HBP; 3 atm, 2 x 90 min at a 24-h interval; animals terminated shortly after the second treatment) immediately after the ischemia or after a 60-min delay generally displayed recovery from motor deficits at 2.5 and 24 h of reperfusion, as well as a reduction in cerebral infarction at 24 h of reperfusion compared to ischemic animals subjected to normal atmospheric pressure. While both HBO and HBP treatments promoted beneficial effects, HBO produced more consistent protection than HBP. Treatment with HBO immediately or 60 min after reperfusion equally produced significant attenuations of cerebral infarction and motor deficits. In contrast, protective effects of HBP treatment against ischemia were noted only when administered immediately after ischemia, which resulted in a significantly reduced infarction volume, but only produced a trend toward decreased behavioral deficits. The present results demonstrate that HBO and, to some extent, HBP reduced ischemic brain damage and behavioral dysfunctions.

The effects of taurine on hNT neurons transplanted in adult rat striatum

Taurine acts as an antioxidant able to protect neurons from free radical-mediated cellular damage. Moreover, it modulates the immune response of astrocytes that participate in neurodegenerative processes. The objective of this study was to examine whether taurine can prevent or attenuate the host inflammatory response induced by the xenotransplantation of neurons derived from the human teratocarcinoma cell line (hNT neurons). Male Sprague-Dawley rats were treated IP with either saline or taurine. Animals from both groups were perfused on the 4th or 11th day and the saline or taurine was administered from the start of the study until the day prior to sacrifice. The brains were processed immunohistochemically using antibodies against glial fibrillary acidic protein (GFAP), microglia (OX42), and human nuclear matrix antigen (NuMA). In the saline group, NuMA labeling revealed small grafts on the 4th day and no surviving cells on the 11th day. However, in the group that received taurine there were surviving grafts at both time points. Strong immunoreactivity for GFAP and OX42 was detected in the saline group surrounding the transplant. These effects were reduced in animals receiving taurine. Taken together, these results demonstrated that taurine was able to facilitate graft survival and attenuate the immune response generated by the xenograft.

In vitro and in vivo characterization of hNT neuron neurotransmitter phenotypes

The hNT neuron exhibits many characteristics of neuroepithelial precursor cells, making them an excellent model to study neuronal plasticity in vitro and in vivo. These cells express a number of neurotransmitters in vitro, including dopamine, gamma-aminobutyric acid and acetylcholine. However, there have been few reports of the neurotransmitters that hNT neurons express in vivo. The present study examined whether hNT neurons express the same neurotransmitters in vivo as they do in vitro. First, the expression of tyrosine hydroxylase (TH), glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT) and the human specific nuclear marker NuMA by hNT neurons was confirmed. Nineteen normal animals were then transplanted with 80,000 hNT neurons aimed at the striatum, hippocampus or cerebral cortex. Five additional animals received injections of medium. All animals received daily intraperitoneal injections of cyclosporine (10 mg/kg) and survived 30 days. Sections through the transplants were examined for NuMA-positive hNT neurons, and for the presence of the three neurotransmitter markers: TH, GAD and ChAT. The hNT neurons were found in the striatum and cortex. Of the hNT neurons found within the rat striatum, 33% were ChAT-positive. In the cortex, only 4% of the neurons expressed ChAT. No GAD-positive hNT neurons were detected at either site. No NuMA-positive neurons were found in the hippocampus. The implanted hNT neurons did not induce activation of astrocytes as determined by immunocytochemistry for glial fibrillary acidic protein (GFAP). Moreover, no hNT neuron was found to express GFAP in vivo. Together, these data suggest that the hNT neurons engraft in the new host tissue, maintain their neuronal identity and may be guided in differentiation according to local environmental cues.

Developmental regulation of neurogenesis in the pluripotent human embryonal carcinoma cell line NTERA-2

Embryonal carcinoma (EC) cells provide a caricature of pluripotent embryonic stem (ES) cells and may be used as surrogates for investigating the mechanisms that regulate cell differentiation during embryonic development. NTERA-2 is a human EC cell line that differentiates in response to retinoic acid yielding cells that include terminally differentiated neurons. The expression of genes known to be involved in the formation of the vertebrate nervous system was examined during retinoic acid-induced NTERA-2 differentiation. Differentiation of these human EC cells into neurons could be divided into three sequential phases. During phase 1, in the first week of differentiation, hath1 mRNA showed a small transient increase that correlated with the rapid accumulation of nestin message, a marker of neuroprogenitors. Transcripts of nestin were quickly downregulated during phase 2 as expression of neuroD1, characteristic of neuroprogenitors exiting the cell cycle, was induced. A neural cell surface antigen, detected by the monoclonal antibody A2B5, was expressed by cells exiting the cell cycle, correlating with the expression of neuroD1 as the cells became post-mitotic. Markers of mature neural cells (e.g. synaptophysin and neuron-specific enolase) were subsequently increased during phase 3 and were maintained. This regulated pattern of gene expression and commitment to the neural lineage indicates that differentiation of NTERA-2 neurons in vitro follows a similar pathway to that observed by neural ectodermal precursors during vertebrate neurogenesis in vivo.

Transplantation therapy for Parkinson's disease

This review paper will provide an overview of the advent of neural transplantation therapy and the milestones achieved over the last 20 years for its use in treating Parkinson's disease. A discussion of technical factors that influence the outcome of neural transplantation is presented, with emphasis given on three sections dealing with immunosuppressants, alternative grafts and trophic factors which have recently been the focus of basic research and development of early phase clinical trials. Some views on the clinical assessment of transplanted Parkinson's disease patients are given at the end of the paper, with a synopsis highlighting the importance of basic research in advancing the potential clinical benefits of neural transplantation therapy in the treatment of Parkinson's disease.

Human NT2 neurons express a large variety of neurotransmission phenotypes in vitro

The NT2 cell line, which was derived from a human teratocarcinoma, exhibits properties that are characteristic of a committed neuronal precursor at an early stage of development. NT2 cells can be induced by retinoic acid to differentiate in vitro into postmitotic central nervous system (CNS) neurons (NT2-N cells). The commitment of NT2-N cells to a stable neuronal phenotype is irreversible. Because it may be possible to transplant these human neurons to compensate for neuronal loss after traumatic injuries or neurodegenerative diseases of the CNS, knowledge of their phenotype is essential. This study aimed to characterize in detail the neurotransmission phenotype of NT2-N cells by using immunocytochemical methods. Single peroxidase immunostaining demonstrated that NT2-N cells expressed the gamma-aminobutyric acidergic (GABAergic), catecholaminergic, and cholinergic phenotypes to a large extent and expressed the serotonergic phenotype to a minor extent. NT2-N cells also expressed different neuropeptides, such as neuropeptide Y, oxytocin, vasopressin, calcitonin gene-related peptide, and Met- and Leu-enkephalin. Double fluorescence immunostaining further indicated that a large number of NT2-N cells could express GABA and another neurotransmitter or neuropeptide at the same time. Finally, electron microscopy demonstrated that these NT2 neurons elaborate classical synaptic contacts. The multipotentiality of these neurons, combined with their apparent functionality, suggests that they may represent useful material for a variety of therapeutic approaches aimed at replacing dead neurons after neurodegenerative diseases or lesions of the CNS.

Transmembrane-4-superfamily proteins CD151 and CD81 associate with alpha 3 beta 1 integrin, and selectively contribute to alpha 3 beta 1-dependent neurite outgrowth

Proteins in the transmembrane-4-superfamily (TM4SF) form many different complexes with proteins in the integrin family, but the functional utility of these complexes has not yet been demonstrated. Here we show that TM4SF proteins CD151, CD81, and CD63 co-distribute with alpha3beta1 integrin on neurites and growth cones of human NT2N cells. Also, stable CD151-alpha3beta1 and CD81-alpha3beta1 complexes were recovered in NT2N detergent lysates. Total NT2N neurite outgrowth on laminin-5 (a ligand for alpha3beta1 integrin) was strongly inhibited by anti-CD151 and -CD81 antibodies either together ( approximately 85% inhibition) or alone ( approximately 45% inhibition). Notably, these antibodies had no inhibitory effect on NT2N neurites formed on laminin-1 or fibronectin, when alpha3beta1integrin was not engaged. Neurite number, length, and rate of extension were all affected by anti-TM4SF antibodies. In summary: (1) these substrate-dependent inhibition results strongly suggest that CD151 and CD81 associations with alpha3beta1 are functionally relevant, (2) TM4SF proteins CD151 and CD81 make a strong positive contribution toward neurite number, length, and rate of outgrowth, and (3) NT2N cells, a well-established model of immature central nervous system neurons, can be a powerful system for studies of integrin function in neurite outgrowth and growth cone motility.

Cell replacement therapies for central nervous system disorders

In animal models, immature neural precursors can replace lost neurons, restore function and promote brain self-repair. Clinical trials in Parkinson's disease suggest that similar approaches may also work in the diseased human brain. But how realistic is it that cell replacement can be developed into effective clinical therapy?

Lumbar transplant of neurons genetically modified to secrete brain-derived neurotrophic factor attenuates allodynia and hyperalgesia after sciatic nerve constriction

Chronic delivery of anti-nociceptive molecules by means of cell grafts near the pain processing centers of the spinal cord is a newly developing technique for the treatment of neuropathic pain. The rat neuronal cell line, RN33B, derived from E13 rat brainstem raphe and immortalized with the SV40 temperature-sensitive allele of large T antigen (tsTag), was transfected with rat brain-derived neurotrophic factor cDNA (BDNF), and the BDNF-synthesizing cell line, 33BDNF.4, was isolated. The 33BDNF.4 cells synthesized mature BDNF protein at permissive temperature (33 degrees C), when the cells were proliferating, and during differentiation at non-permissive temperature (39 degrees C) in vitro. The bio-active BDNF protein was also secreted by the cells during both growth conditions, as measured by ELISA analysis of BDNF content and secretion. The bio-activity of the BDNF in 33BDNF.4 cell conditioned media was assessed by neurite outgrowth from E15 dorsal root ganglion (DRG) cultures. A control cell line, 33V1, transfected with the vector alone, did not synthesize or secrete any significant BDNF at either growth condition. Both cell lines were used as grafts in a model of chronic neuropathic pain induced by unilateral chronic constriction injury (CCI) of the sciatic nerve. Pain-related behaviors, including cold and tactile allodynia and thermal and tactile hyperalgesia, were evaluated after CCI in the affected hindpaw. When 33BDNF.4 and 33V1 cells were transplanted in the lumbar subarachnoid space of the spinal cord 1 week after CCI, they survived greater than 7 weeks on the pia mater around the spinal cord and the 33BDNF.4 cells continued to synthesize BDNF in vivo. Furthermore, the tactile and cold allodynia and tactile and thermal hyperalgesia induced by CCI was significantly reduced during the 2-7 week period after grafts of 33BDNF.4 cells. The maximal effect on chronic pain behaviors with the BDNF grafts occurred 2-3 weeks after transplant and the anti-nociceptive effects of the BDNF cell grafts was permanent. Transplants of the control 33V1 cells had no effect on the allodynia and hyperalgesia induced by CCI and these cells did not synthesize BDNF in vivo. These data suggest that a chronically applied, low local dose of BDNF supplied by transplanted cells near the spinal dorsal horn was able to reverse the development of chronic neuropathic pain following CCI. The use of neural cell lines that are able to deliver anti-nociceptive molecules, such as BDNF, in a model of chronic pain offers a novel approach to pain management and such 'biologic minipumps' can be developed for safe use in humans.

The properties of hNT cells following transplantation into the subventricular zone of the neonatal forebrain

Neurons derived from the human teratocarcinoma cell line (hNT) establish structural polarity and a fully mature phenotype following transplantation into the rodent brain. Here we describe the transplantation of hNT cells into the anterior part of neonatal subventricular zone (SVZa), which is a prolific region of neuronal progenitor cells. Ordinarily, the progeny of endogenous or homotopically transplanted SVZa cells migrate to the olfactory bulb (OB) along a restricted pathway, the rostral migratory stream (RMS), and differentiate into interneurons. To compare the phenotype of cultured hNT cells to their transplanted cohorts, hNT cells labeled by the fluorescent dye PKH26 were cultured for 1 day and stained with cell-type-specific antibodies. Clusters as well as individual hNT cells were immunoreactive for TuJ1, an antibody that recognizes neuron-specific class III beta-tubulin. The distribution and phenotype of the transplanted hNT cells were examined. The majority of transplanted PKH26-labeled hNT cells were found at their site of implantation in the SVZa, while a small proportion of the transplanted hNT cells was situated in the migratory pathway leading to the OB and in the subependymal zone and granule cell layer of the olfactory bulb. Many of the transplanted hNT cells, both within the SVZa and within the RMS, revealed a neuronal phenotype. Collectively, these results reveal the capacity of hNT cells to respond, at least partially, to cues that ordinarily govern the migration of SVZa-derived cells and maintain their neuronal identity.

Intrastriatal and intranigral grafting of hNT neurons in the 6-OHDA rat model of Parkinson's disease

The clinical findings on neural transplantation for Parkinson's disease (PD) reported thus far are promising but many issues must be addressed before neural transplantation can be considered a routine therapeutic option for PD. The future of neural transplantation for the treatment of neurological disorders may rest in the discovery of a suitable alternative cell type for fetal tissue. One such alternative may be neurons derived from a human teratocarcinoma (hNT). hNT neurons have been shown to survive and integrate within the host brain following transplantation and provide functional recovery in animal models of stroke and Huntington's disease. In this study, we describe the transplantation of hNT neurons in the substantia nigra (SN) and striatum of the rat model for PD. Twenty-seven rats were grafted with one of three hNT neuronal products; hNT neurons, hNT-DA neurons, or lithium chloride (LiCl) pretreated hNT-DA neurons. Robust hNT grafts could be seen with anti-neural cell adhesion molecule and anti-neuron-specific enolase immunostaining. Immunostaining for tyrosine hydroxylase (TH) expression revealed no TH-immunoreactive (THir) neurons in any animals with hNT neuronal grafts. THir cells were observed in 43% of animals with hNT-DA neuronal grafts and all animals with LiCl pretreated hNT-DA neuronal grafts (100%). The number of THir neurons in these animals was low and not sufficient to produce significant functional recovery. In summary, this study has demonstrated that hNT neurons survive transplantation and express TH in the striatum and SN. Although hNT neurons are promising as an alternative to fetal tissue and may have potential clinical applications in the future, further improvements in enhancing TH expression are needed.

Intracerebral transplantation of bone marrow with BDNF after MCAo in rat

We tested the hypothesis that a composite graft of fresh bone marrow (BM) along with brain-derived neurotrophic factor (BDNF), transplanted into the ischemic boundary zone (IBZ) of rat brain, facilitates BM cells to survive and differentiate, and improves functional recovery after middle cerebral artery occlusion (MCAo). The fresh BM was harvested from adult rats injected with bromodeoxyuridine (BrdU) as a tracer. Rats (n=37) were subjected to 2h of MCAo, received grafts at 24h and were sacrificed at 7days after MCAo. Test groups consisted of: (1) control - MCAo alone (n=9); (2) injection of phosphate buffered saline (n=4); (3) transplantation of BM (n=8); (4) injection of BDNF (n=7); and (5) transplantation of BM with BDNF (n=9) into the IBZ. Immunohistochemistry was used to identify cells derived from the BM stem cells. Behavioral tests (rotarod motor test; adhesive-removal somatosensory test) were performed before and 7days after MCAo. The data indicate that intracerebral grafting of a combination of BM with BDNF enhances differentiation of BM cells and significantly improves motor recovery of rotarod (P<0.05) and adhesive-removal (P<0.05) tests. We anticipate that BM along with neurotrophic factors may provide a powerful autoplastic therapy for human neurological injury and degenerative disorders.

Neural transplantation cannula and microinjector system: experimental and clinical experience. Technical note

The authors present a simple, reliable, and safe system for performing neural transplantation in the human brain. The device consists of a transplantation cannula and microinjector system that has been specifically designed to reduce implantation-related trauma and to maximize the number of graft deposits per injection. The system was evaluated first in an experimental rat model of Parkinson's disease (PD). Animals in which transplantation with this system had been performed showed excellent graft survival with minimal trauma to the brain. Following this experimental stage, the cannula and microinjector system were used in eight patients with PD enrolled in the Halifax Neural Transplantation Program who received bilateral putaminal transplants of fetal ventral mesencephalic tissue. A total of 16 transplantation operations and 64 trajectories were performed in the eight patients, and there were no intraoperative or perioperative complications. Magnetic resonance imaging studies obtained 24 hours after surgery revealed no evidence of tissue damage or hemorrhage. Transplant survival was confirmed by fluorodopa positron emission tomography scans obtained 6 and 12 months after surgery. As neural transplantation procedures for the treatment of neurological conditions evolve, the ability to deliver viable grafts safely will become critically important. The device presented here has proved to be of value in maximizing the number of graft deposits while minimizing implantation-related trauma to the host brain.

Survival, neuronal differentiation, and fiber outgrowth of propagated human neural precursor grafts in an animal model of Huntington's disease

Expanded neural precursor cells provide an attractive alternative to primary fetal tissue for cell replacement therapies in neurodegenerative diseases. In this study we transplanted epigenetically propagated human neural precursor cells into a rat model of Huntington's disease. Neural precursors survived transplantation and large numbers differentiated to express neuronal antigens, including some that expressed DARPP-32, indicating a mature striatal phenotype had been adopted. Neuronal fibers from the grafts projected diffusely throughout the host brain, although there was no evidence that outgrowth was specifically target directed. This study supports the contention that propagated human neural precursors may ultimately be of use in therapeutic neural transplantation paradigms for diseases such as Huntington's disease.

Differential effects of spinal cord gray and white matter on process outgrowth from grafted human NTERA2 neurons (NT2N, hNT)

To investigate host effects on grafts of pure, postmitotic, human neurons, we assessed the morphologic and molecular phenotype of purified NTera2N (NT2N, hNT) neurons implanted into the spinal cord of athymic nude mice. NT2N neurons were implanted into both spinal cord gray matter and white matter of neonatal, adolescent, and adult mice and were evaluated at postimplantation times up to 15 months. NT2N neurons remained at the implantation site and showed process integration into all host areas, and each graft exhibited similar phenotypic features regardless of location or host age at implantation. Evidence of host oligodendrocyte ensheathment of NT2N neuronal processes was seen, and grafted NT2N neurons acquired and maintained the morphologic and molecular phenotype of mature neurons. The microenvironments of host gray matter and white matter appear to exert differential effects on implanted neuronal processes, because consistent differences were noted in the morphologies of graft processes extending into white matter versus gray matter. NT2N processes extended for long distances (>2 cm) within white matter, whereas NT2N processes located within gray matter had shorter trajectories. This suggests that NT2N neurons integrate similarly into spinal cord gray matter and white matter, but they extend processes that respond differentially to gray matter and white matter cues. Further studies of the model system described here may identify the host molecular signals that support and direct integration of grafted human neurons as well as the outgrowth of their processes in the nervous system.

Restorative neurosurgery: opportunities for restoration of function in acquired, degenerative, and idiopathic neurological diseases

Historically, neurosurgery has improved the environment of the nervous system to promote maximal spontaneous recovery of function. The population of patients whom we treat at present is a small portion of those who suffer from disabling neurological illnesses. Based on a combination of new technology, and advances in neuroscience, restorative neurosurgery is advancing the frontiers of our specialty, and providing the potential to restore lost function. Significant advancements in gene therapy, the discovery and delivery of neurotrophic factors, and cell transplantation now require neurosurgeons to broaden the scope of our practice so that it includes the restoration of function in an enormous number of patients with acquired, degenerative and idiopathic neurological diseases. In order to meet the present challenge, neurosurgeons must broaden our vision, our role, and our future educational goals. In this review, we summarize the landmark advances in the basic and clinical neurosciences and the results of clinical trials that are driving our evolution from passive reaction to disease to active attempts to restore lost central nervous system function.

Neural transplantation of human neuroteratocarcinoma (hNT) neurons into ischemic rats. A quantitative dose-response analysis of cell survival and behavioral recovery

Transplantation of fetal neuronal tissue has been used successfully to ameliorate symptoms of neurodegenerative disease in animals and humans. This technique has recently been extended as an experimental treatment for ischemic brain damage. However, due to ethical issues with the use of fetal cells for the treatment of any human disease, there has been a concerted effort to find alternative graft sources for neural transplantation. The human neuroteratocarcinoma neuron cell is derived from an embryonal teratocarcinoma cell line that can be differentiated into post-mitotic neurons. Neural transplantation of human neuroteratocarcinoma neurons has recently been shown to produce behavioral amelioration of symptoms in rats with ischemia-induced injury. The present study was undertaken to: (i) determine the minimum effective number of transplanted human neuroteratocarcinoma neurons required for amelioration of ischemia-induced behavioral dysfunction; and (ii) quantify the survival of human neuroteratocarcinoma neurons in vivo. Transplants of 0, 5, 10, 20, 40, 80 or 160 x 10(3) human neuroteratocarcinoma neurons were made into rats that sustained ischemic damage. Animals that received 40, 80 or 160 x 10(3) human neuroteratocarcinoma neurons demonstrated a dose-dependent improvement in performance of both the passive avoidance and elevated body swing tests. At the conclusion of behavioral testing, human neuroteratocarcinoma neurons were identified in paraffin sections with human neural cell adhesion molecule MOC-1 and human neurofilament antibodies. Transplants of 80 or 160 x 10(3) human neuroteratocarcinoma neurons demonstrated a 12-15% survival of human neuroteratocarcinoma neurons in the graft, while transplants of 40 x 10(3) human neuroteratocarcinoma neurons demonstrated a 5% survival. Transplantation of human neuroteratocarcinoma neurons ameliorated behavioral deficits produced by ischemic damage. The human neuroteratocarcinoma neuron, additionally, showed greater survival than that reported for fetal cells when transplanted into the brain. Therefore, this readily available cell may prove to be an excellent candidate for the treatment of ischemic damage in human patients.

Lithium chloride induces the expression of tyrosine hydroxylase in hNT neurons

In the present study, several doses of lithium chloride were tested for their ability to induce the expression of tyrosine hydroxylase (TH) in neurons derived from a human teratocarcinoma cell line (hNT) after 5 and 10 days in vitro (DIV). Following immunocytochemical staining for tyrosine hydroxylase, the percentage of TH-positive neurons was determined and morphometric analysis, including mean soma profile area and neuritic length, was performed. hNT neurons responded to lithium treatment in a dose-dependent manner. In 5 DIV, the most effective dose of lithium chloride (1.0 mM) increased the number of TH-positive neurons approximately sixfold. In addition, both TH-positive hNT neuron mean soma profile area and neurite length were significantly larger than controls by 60 and 70%, respectively. Moreover, even after withdrawal of lithium chloride on day 5, the number of TH-positive neurons in 10 DIV cultures remained significantly increased. These data suggest that hNT cells are indeed responsive to lithium exposure and may serve as a continual source of TH-expressing neurons in new therapeutic approaches to degenerative brain disease.

Terminally differentiated human neurons survive and integrate following transplantation into the traumatically injured rat brain

The present study evaluated the survival and integration of human postmitotic neurons (hNT) following transplantation into the traumatically injured rodent brain. Anesthetized male Sprague-Dawley rats (n = 47) were subjected to lateral fluid percussion brain injury of moderate severity (2.4-2.6 atm). Sham animals (n = 28) were surgically prepared, but did not receive brain injury. At 24 h following injury or sham surgery, the rats were re-anesthetized and approximately 100,000 hNT cells (freshly cultured or previously frozen) or vehicle were stereotactically injected into the ipsilateral cortex. Animals were examined for neuromotor function at 48 h, 7 days, and 14 days posttransplantation using a standard battery of motor tests. Animals were sacrificed at 2 weeks postinjury and viability of hNT grafts was assessed by Nissl staining and MOC-1 immunohistochemistry, which recognizes human neural cell adhesion molecules (NCAM) expressed on hNT cells. Transplanted hNT grafts remained viable in 83% of brain-injured animals at 2 weeks following transplantation of either fresh or frozen hNT cells. Glial fibrillary acidic protein (GFAP) immunohistochemistry revealed a marked increase in the number of reactive astrocytes following brain injury in both vehicle and hNT implanted animals. These reactive astrocytes appeared not to impede grafted cells from sending projections into host tissue. Despite the survival of transplanted cells in the traumatically injured brain, hNT cells had no significant effect on posttraumatic neurologic motor function during the acute posttraumatic period. Since hNT cells are transfectable, prolonged survival of these transplanted cells in the posttraumatic milieu suggests that grafted hNT cells may be a suitable means for delivery of therapeutic, exogenous proteins into the CNS for treatment of traumatic brain injury.

Neural transplantation of hNT neurons for Huntington's disease

Fetal striatal tissue transplants have been shown to restore motor deficits in rat and monkey models of Huntington's disease (HD). In the present study, using rats with unilateral striatal lesions, we compared fetal striatal tissue transplants to transplants of human NT (hNT) neurons. hNT neurons are terminally differentiated cells derived from the human NTera-2 cell line. In vitro, we have found that purified hNT neurons have a biochemical phenotype similar to that of human fetal striatal tissue. Both hNT neurons and fetal striatal tissue express mRNAs for glutamic acid decarboxylase, choline acetyltransferase, and the D1 and D2 dopamine receptors. Grafts of either hNT neurons or fetal striatal tissue into unilateral quinolinic acid-lesioned rat striatum improved methamphetamine-induced circling behavior. Sham controls showed no changes in methamphetamine-induced circling behavior. In the staircase test for skilled forelimb use, both transplant groups showed partial recovery in skilled use of the paw contralateral to the side of lesion, whereas the control animals showed continued deficits. These findings suggest that transplantation of hNT neurons may be an alternative to transplantation of fetal striatal tissue in the treatment of HD.

Survival and integration of transplanted postmitotic human neurons following experimental brain injury in immunocompetent rats

OBJECT

Limitations regarding cell homogeneity and survivability do not affect neuronlike hNT cells, which are derived from a human teratocarcinoma cell line (Ntera2) that differentiates into postmitotic neurons with exposure to retinoic acid. Because NT2N neurons survive longer than 1 year after transplantation into nude mice brains, the authors grafted these cells into the brains of immunocompetent rats following lateral fluid-percussion brain injury to determine the long-term survivability of NT2N cell grafts in cortices damaged by traumatic brain injury (TBI) and the therapeutic effect of NT2N neurons on cognitive and motor deficits.

METHODS

Seventy-two adult male Sprague-Dawley rats, each weighing between 340 and 370 g, were given an anesthetic agent and subjected to lateral fluid percussion brain injury of moderate severity (2.2-2.5 atm in 46 rats) or to surgery without TBI (shamoperation, 26 rats). Twenty-four hours postinjury, 10(5) NT2N cells (24 injured animals) or 3 microl of vehicle (22 injured and 14 control animals) was stereotactically implanted into the periinjured or control cerebral cortex. Motor function was assessed at weekly intervals and all animals were killed at 2 or 4 weeks after their posttraumatic learning ability was assessed using a Morris water maze paradigm. Viable NT2N grafts were routinely observed to extend human neural cell adhesion molecule-(MOC-1)immunoreactive processes into the periinjured cortex at 2 and 4 weeks posttransplantation, although no significant improvement in motor or cognitive function was noted. Inflammation identified around the transplant at both time points was assessed by immunohistochemical identification of macrophages (ED-1) and microglia (isolectin B4).

CONCLUSIONS

Long-term survival and integration of NT2N cells in the periinjured cortex of immunocompetent rats provides the researcher with an important cellular system that can be used to study maturation, regulation, and neurite outgrowth of transplanted neurons following TBI.

Engraftable human neural stem cells respond to developmental cues, replace neurons, and express foreign genes

Stable clones of neural stem cells (NSCs) have been isolated from the human fetal telencephalon. These self-renewing clones give rise to all fundamental neural lineages in vitro. Following transplantation into germinal zones of the newborn mouse brain they participate in aspects of normal development, including migration along established migratory pathways to disseminated central nervous system regions, differentiation into multiple developmentally and regionally appropriate cell types, and nondisruptive interspersion with host progenitors and their progeny. These human NSCs can be genetically engineered and are capable of expressing foreign transgenes in vivo. Supporting their gene therapy potential, secretory products from NSCs can correct a prototypical genetic metabolic defect in neurons and glia in vitro. The human NSCs can also replace specific deficient neuronal populations. Cryopreservable human NSCs may be propagated by both epigenetic and genetic means that are comparably safe and effective. By analogy to rodent NSCs, these observations may allow the development of NSC transplantation for a range of disorders.