Endogenous Neural Progenitor Cells Research Articles

Myelin repair strategies: a cellular view

The development of successful myelin repair strategies depends on the detailed knowledge of the cellular and molecular processes underlying demyelination and remyelination in the central nervous system of animal models and in patients with multiple sclerosis (MS). Based on the complexity of the demyelination and remyelination processes, it should be expected that effective therapeutic approaches will require a combination of strategies for immunomodulation, neuroprotection, and myelin replacement. This brief review highlights recent cellular and molecular findings and indicates that future therapeutic strategies to enhance remyelination may also require combinatorial treatment to accomplish. The relapsing-remitting course of some forms of multiple sclerosis has typically fueled hope for effective repair of multiple sclerosis lesions, if demyelinating activity could be attenuated. Recent findings support the potential of endogenous neural stem cells and progenitor cells to generate remyelinating oligodendrocytes. Importantly, interactions with viable axons and supportive astrocytic responses are required for endogenous immature cells to fulfill their potential remyelinating capacity. The research described here will help in identifying the major obstacles to effective remyelination and potential therapeutic targets to guide development of comprehensive approaches for testing in animal models and eventual treatment of patients with multiple sclerosis.

Neural progenitor cells transplanted into the uninjured brain undergo targeted migration after stroke onset

Endogenous neural stem cells normally reside in their niche, the subventricular zone, in the uninjured rodent brain. Upon stroke, these cells become more proliferative and migrate away from the subventricular zone into the surrounding parenchyma. It is not known whether this stroke-induced behavior is due to changes in the niche or introduction of attractive cues in the infarct zone, or both. A related question is how transplanted neural stem cells respond to subsequent insults, including whether exogenous stem cells have the plasticity to respond to subsequent injuries after engraftment. We addressed this issue by transplanting neural progenitor cells (NPCs) into the uninjured brain and then subjecting the animal to stroke. We were able to follow the transplanted NPCs in vivo by labeling them with superparamagnetic iron oxide particles and imaging them via high-resolution magnetic resonance imaging (MRI) during engraftment and subsequent to stroke. We find that transplanted NPCs that are latent can be activated in response to stroke and exhibit directional migration into the parenchyma, similar to endogenous neural NPCs, without a niche environment.

Disease Targets and Strategies for the Therapeutic Modulation of Endogenous Neural Stem and Progenitor Cells

Neural stem cells, able to self-renew and give rise to both neurons and glia, line the cerebral ventricles of the adult human brain. Humans also harbor lineage-restricted neuronal progenitors in the hippocampus and glial progenitor cells in both the gray and white matter of the forebrain. These various stem and progenitor cell types may provide targets for pharmacotherapy for a variety of disorders of the central nervous system. Each resident progenitor phenotype may be mobilized and induced to differentiate in vivo by the actions of both exogenous growth factors and small molecule modulators of progenitor-selective signaling pathways. This strategy may be particularly efficacious in neurodegenerations such as Huntington's disease, in which lost neurons may be replenished through the directed induction of progenitor cells lining the ventricular wall of the affected striatum. Similarly, the mobilization of glial progenitor cells may permit the introduction of new oligodendrocytes to demyelinated regions of adult white matter. Our rapidly increasing understanding of the molecular control of progenitor cell mobilization and differentiation should provide a wealth of new opportunities for recruiting endogenous progenitors as a means of treating neurological disease.

Temporal Response of Neural Progenitor Cells to Disease Onset and Progression in Amyotrophic Lateral Sclerosis-Like Transgenic Mice

Regenerative medicine through neural stem cells (NSCs) or neural progenitor cells (NPCs) has been proposed as an alterative avenue for restoring neurological dysfunction in amyotrophic lateral sclerosis (ALS). It is critical to understand the organization and distribution of endogenous adult NPCs in response to motor neuron degeneration before regenerative medicine can be applied for ALS therapy. For this reason, we analyzed the temporal response of NPCs to motor neuron degeneration in the spinal cord and brain using nestin enhancer-driven LacZ reporter transgenic mice (pNes-Tg mice, control) and bi-transgenic mice containing both the nestin enhancer-driven LacZ reporter gene and mutant G93A-SOD1 gene (Bi-Tg mice). We observed an increase of NPCs in the dorsal horns of the spinal cord at the disease onset and progression stages in the Bi-Tg mice compared with that of age-matched pNes-Tg control mice. In contrast, an increase of NPCs in the ventral horns was detected at the disease progression stage. On the other hand, an increase of NPCs in the motor cortex at the disease-onset stage, but not at the disease progression stage, was detected. Furthermore, a decrease of NPCs in the lateral ventricle at the disease progression stage was observed, whereas no difference in the number of NPCs in the hippocampus was detected at the disease onset and progression stages. Some of the NPCs differentiate into neuron-like cells in response to motor neuron degeneration. The organization and distribution of endogenous adult NPCs in the ALS-like transgenic mice at the disease onset and progression stages provide fundamental bases for consideration of regenerative therapy of ALS by increasing de novo neurogenesis.

“Transcribing” postischemic neurogenesis: a tale revealing hopes of adult brain repair

Stroke, trauma and neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases affect millions of people worldwide. To date, treatment for these disorders is mainly symptomatic. However, the discovery of multipotent neural progenitor cell (NPC) capable of producing not only glia but also neurons in the adult brain has brought revolutionary changes in the field of restorative therapy. Currently, it posits that regeneration of neurons can occur throughout life, opening a door for the development of novel therapies to treat neurological diseases by neuronal regeneration using proliferation, differentiation, and integration of NPC at sites of brain injury. To achieve this goal, we need to strive to better understand the molecular signals involved in the control of NPC fate and the mechanisms inducing their migration and integration into the existing neural networks and synaptic circuits. The functional properties of the newborn neurons and their ability to form appropriate afferent and efferent connections should be determined for optimizing functional recovery in human disorders. In studying adult neurogenesis and adult NPC, the availability of developmental paradigms, such as embryonic neurogenesis and embryonic NPC, stands as a candidate experimental model. During the assembly of neural circuits in the developing brain, embryonic NPC generates functionally distinct neuronal cell types, each at a stereotyped position. In recent years, considerable progress has been made in defining the molecular players controlling embryonic NPC specification [1, 2]. These studies have revealed that neural cell fate depends critically on local environmental signals, which direct cell fates by inducing the expression of intrinsic proteins, notably transcription factors (TFs). In molecular biology, a TF is a protein that regulates transcription of target genes. In particular, TFs regulate the binding of RNA polymerase and the initiation of transcription. TFs act in networks [3] to induce the expression of target genes, which subsequently define the fate of the descendant cells (Fig. 1). In fact, developmental mechanisms may be more than just a model for studying the molecular regulation of adult neurogenesis. Recent laboratory evidence has identified some key embryonic NPC molecular regulators, such as sonic hedgehog and Wnt, as modulators of adult NPC [4–6]. In addition to these secreted signals, some of the intracellular TFs involved in developmental neural patterning were found to be expressed by and to affect aspects of the adult NPC biology (see [7] for a recent review). It is not surprising then that there is an increasing interest on how to employ TFs to manipulate endogenous NPC for the purposes of repairing the injured brain. In the current issue, Scholzke and Schwaninger [8] summarize the present state-of-the-art investigation on the TF involvement in neurogenesis after cerebral ischemia— the most common type of cerebral injury. Their review is unique, as it represents the first attempt to collectively analyze the transcriptional control of adult NPC in the context of reactive neurogenesis after ischemic damage to the brain. At present, the evidence for TF involvement in ischemia-induced adult neurogenesis is rather scarce and reports mainly the association of a certain TF with this process rather than its precise role. To overcome this, the authors review the major molecular players regulating embryonic NPC and then elegantly draw possible J Mol Med DOI 10.1007/s00109-007-0210-5

Recruitment of Endogenous Neural Progenitor Cells by Malignant Neoplasms of the Central Nervous System

It is proposed here that malignancies of the central nervous system (CNS) are capable of recruiting non-malignant CNS precursor cells and that doing so worsens the course of the disease. In particular, the argument is put forward that such tumors can activate resident neural stem cells, attract them or their progeny to the tumor site, and induce them to proliferate. What begins as a normal wound repair response by the recruited cells can eventually result in augmentation of the tumor. In support of this hypothesis, evidence consistent with the ideas proposed is presented. Since these recruited cells are non-malignant, it should be possible to interfere with this process. This would not necessarily remove the threat posed by the cancer, but could beneficially impact patients by slowing progression. Interfering with recruitment could simultaneously serve to block autocrine stimulation by tumor cells. In contrast, introducing exogenous stem cells could exacerbate the recruitment process unless measures are taken to preclude this possibility. Finally, it is worth noting that the situation described in the current hypothesis might apply to a variety of other stem and precursor cell-containing systems throughout the body.

Are cranial germ cell tumours really tumours of germ cells?

Germ cell tumours of the brain and those that occur in the gonads are believed to share a common origin from germ cell progenitors. This 'germ cell theory' rests upon similar histopathology between these tumours in different locations and the belief that endogenous somatic cells of the brain could not give rise to the range of cell types seen in germ cell tumours. An alternative 'embryonic cell theory' has been proposed for some classes of cranial germ cell tumours, but this still relies on the misplacement of cells in the brain (in this case the earliest embryonic stem cells) during early embryonic development. Recent evidence has demonstrated that neural stem cells of the brain can also give rise to many of the cell types seen in germ cell tumours. These data suggest that endogenous progenitor cells of the brain are a plausible alternative origin for these tumours. This idea is of central importance for studies aiming to elucidate the mechanisms of tumour development. The application of modern molecular analyses to reveal how tumour cells have altered with respect to their cell of origin relies on the certain identification of the cell from which the particular tumour arose. If the identity of this cell is mistaken, then studies to elucidate the mechanisms by which the progenitor cell has been subverted from its normal behaviour will not yield useful information. In addition, it will prove impossible to generate an appropriate animal model in which to study the underlying causes of those tumours. This article makes the case that current assumptions of the origins of cranial germ cell tumours are unreliable. It reviews the evidence in favour of the 'germ cell theory' and argues in favour of a 'brain cell theory' in which endogenous neural progenitor cells of the brain are the likely origin for these tumours. Thus, the case is made that cranial germ cell tumours, like other brain tumours, arise by the transformation of progenitor cells normally resident in the brain.

Selective blockage of Kv1.3 and Kv3.1 channels increases neural progenitor cell proliferation

The modulation of cell proliferation in neural progenitor cells (NPCs) is believed to play a role in neuronal regeneration. Recent studies showed that K(+) channel activity influenced cell proliferation. Therefore, we examined NPCs for K(+) channels and tested whether NPC self renewing can be modulated by synthetic K(+) channel modulators. The whole-cell K(+) current was partly K(+) dependent and showed a cumulative inactivating component. Two tetra-ethyl-ammonium ion (TEA)-sensitive K(+) currents with different voltage dependencies ( = 65 microm, E(50) = -0.3 +/- 1.3 mV and = 8 mm, E(50) = -15.2 +/- 2.8 mV) and an almost TEA-insensitive current were identified. Kaliotoxin blocked approximately 50% of the entire K(+) currents (IC(50) = 0.25 nm). These properties resembled functional characteristics of K(v)1.4, K(v)1.3 and K(v)3.1 channels. Transcripts for these channels, as well as proteins for K(v)1.3 and K(v)3.1, were identified. Immunocytochemical staining revealed K(v)1.3 and K(v)3.1 K(+) channel expression in almost all NPCs. The blockage of K(v)3.1 by low concentrations of TEA, as well as the blockage of K(v)1.3 by Psora-4, increased NPC proliferation. These findings underline the regulatory role of K(+) channels on the cell cycle and imply that K(+) channel modulators might be used therapeutically to activate endogenous NPCs.

Mitogen-Activated Protein Kinase Signaling, Oxygen Sensors and Hypoxic Induction of Neurogenesis

In the adult nervous system, neuronal subpopulations sustain a hierarchical pattern of selective vulnerability to hypoxia. Hypoxia also activates quiescent neural progenitor cells (NPCs) resulting in their amplification and subsequent differentiation into neurons and glia. Use of rat organotypic hippocampal cultures facilitates examination of early signaling events in response to hypoxia and reoxygenation that result in neurogenesis. Cultures were exposed to hypoxia for up to 6 h followed by reoxygenation. CA1 neurons showed focal nuclear condensation by 2 h of hypoxia, but CA2 and CA3 neurons were spared. JNKs and c-Jun reached peak activation by 4 h, returning to basal levels by 6 h. Expression of oxygen sensors, hemoxygenase 2 and HIF1, were elevated by 30 min and 2 h, respectively. By 24 h of reoxygenation, there was proliferation of nestin-positive NPCs. With U0126, an upstream inhibitor of ERK activation, BrdU labeling was markedly reduced immunohistochemically as well as PCNA protein expression, suggesting a role for ERKs in the proliferation response. Immunohistochemically, antinestin detected NPCs and on Western blots reached peak levels by 24–48 h of reoxygenation. Proliferation and differentiation of endogenous NPCs in the area of neuronal loss further suggests that mechanisms potentially exist in vitro for replacement with functional neurons.

Early Response of Endogenous Adult Neural Progenitor Cells to Acute Spinal Cord Injury in Mice

Adult neural progenitor cells (NPCs) are an attractive source for functional replacement in neurodegenerative diseases and traumatic injury to the central nervous system (CNS). It has been shown that transplantation of neural stem cells or NPCs into the lesioned region partially restores CNS function. However, the capacity of endogenous NPCs in replacement of neuronal cell loss and functional recovery of spinal cord injury (SCI) is apparently poor. Furthermore, the temporal and spatial response of endogenous adult NPCs to SCI remains largely undefined. To this end, we have analyzed the early organization, distribution, and potential function of NPCs in response to SCI, using nestin enhancer (promoter) controlled LacZ reporter transgenic mice. We showed that there was an increase of NPC proliferation, migration, and neurogenesis in adult spinal cord after traumatic compression SCI. The proliferation of NPCs detected by 5-bromodeoxyuridine incorporation and LacZ staining was restricted to the ependymal zone (EZ) of the central canal. During acute SCI, NPCs in the EZ of the central canal migrated vigorously toward the dorsal direction, where the compression lesion is generated. The optimal NPC migration occurred in the adjacent region close to the epicenter. More significantly, there was an increased de novo neurogenesis from NPCs 24 hours after SCI. The enhanced proliferation, migration, and neurogenesis of (from) endogenous NPCs in the adult spinal cord in response to SCI suggest a potential role for NPCs in attempting to restore SCI-mediated neuronal dysfunction.

Chemokines Regulate the Migration of Neural Progenitors to Sites of Neuroinflammation

Many studies have shown that transplanted or endogenous neural progenitor cells will migrate toward damaged areas of the brain. However, the mechanism underlying this effect is not clear. Here we report that, using hippocampal slice cultures, grafted neural progenitor cells (NPs) migrate toward areas of neuroinflammation and that chemokines are a major regulator of this process. Migration of NPs was observed after injecting an inflammatory stimulus into the area of the fimbria and transplanting enhanced green fluorescent protein (EGFP)-labeled NPs into the dentate gyrus of cultured hippocampal slices. Three to 7 d after transplantation, EGFP-NPs in control slices showed little tendency to migrate and had differentiated into neurons and glia. In contrast, in slices injected with inflammatory stimuli, EGFP-NPs migrated toward the site of the injection. NPs in these slices also survived less well. The inflammatory stimuli used were a combination of the cytokines tumor necrosis factor-alpha and interferon-gamma, the bacterial toxin lipopolysaccharide, the human immunodeficiency virus-1 coat protein glycoprotein 120, or a beta-amyloid-expressing adenovirus. We showed that these inflammatory stimuli increased the synthesis of numerous chemokines and cytokines by hippocampal slices. When EGFP-NPs from CC chemokine receptor CCR2 knock-out mice were transplanted into slices, they exhibited little migration toward sites of inflammation. Similarly, wild-type EGFP-NPs exhibited little migration toward inflammatory sites when transplanted into slices prepared from monocyte chemoattractant protein-1 (MCP-1) knock-out mice. These data indicate that factors secreted by sites of neuroinflammation are attractive to neural progenitors and suggest that chemokines such as MCP-1 play an important role in this process.

451. AAV-BDNF Augments Neurogenesis in Both the Normal Adult Rat Brain and the Quinolinic Acid Lesion Model of Huntington's Disease

The presence of ongoing neurogenesis in the adult mammalian brain raises the exciting possibility that endogenous progenitor cells could be used therapeutically for repair of neuronal loss associated with brain disease or injury. While previous studies have demonstrated that the adult brain has the potential for self-repair, it is apparent that the level of neurogenesis observed is insufficient to compensate for the progressive cell loss that occurs during brain injury and disease. In order for endogenous progenitor cells to be useful therapeutically, methods need to be developed to augment the process of neurogenesis and direct progenitor cells to proliferate, migrate and generate new neurons in specific areas of neuronal cell loss. Using in vivo gene transfer, we investigated the effect of Brain-Derived Neurotrophic Factor (BDNF) on the migration, differentiation and survival of endogenous progenitor cells in both the normal adult rat brain and the quinolinic acid (QA) lesion rat model of Huntington's disease (HD). We have developed a recombinant AAV vector encoding the human BDNF transgene under the control of the CBA constitutive promoter. Adult rats received unilateral stereotaxic injections of either AAV-BDNF, the control vector AAV-luciferase or sterile PBS into the anterior subventricular zone (SVZ). Three weeks later, the rats received daily injections of the mitotic marker bromodeoxyuridine (BrdU; 150 mg/kg i.p.) for 21 days in order to identify newly generated cells. Half of the rats also received a unilateral striatal injection of QA (50 nmol) in order to model HD. In the normal adult rat brain, BDNF over-expression had no effect on the number of BrdU labelled cells in the SVZ or striatum but resulted in a significant increase in BrdU labelling in the rostral migratory stream (RMS) compared to untreated animals (p|[le]|0.01). In untreated animals that received a striatal QA lesion we observed a significant reduction in the number of BrdU labelled cells in the SVZ and RMS compared to unlesioned animals (p|[le]|0.05) 21 days after lesioning, suggesting a chronic alteration in the dynamics of progenitor cell proliferation in response to QA lesioning. While BDNF over-expression did not alter the reduction in BrdU labelling observed in the RMS of QA lesioned animals, BDNF significantly increased the level of BrdU labelling in the SVZ of QA lesioned animals to that observed in unlesioned animals (p|[le]|0.01). BDNF also greatly induced the level of BrdU-immunoreactivity observed in the QA lesioned striatum compared to untreated animals (p|[le]|0.001). Furthermore, 9 weeks following QA lesioning we observed that BDNF over-expression had greatly enhanced the level of striatal neurogenesis observed in QA lesioned animals compared to untreated animals. These results demonstrate that over-expression of BDNF in the SVZ substantially augments the survival, migration and neuronal differentiation of progenitor cells in both neurogenic and non-neurogenic regions of the normal or QA lesioned adult rat brain, supporting the potential therapeutic use of endogenous neural progenitor cells for the treatment of HD.

Enhanced proliferation of progenitor cells in the subventricular zone and limited neuronal production in the striatum and neocortex of adult macaque monkeys after global cerebral ischemia

Cerebral ischemia in adult rodent models increases the proliferation of endogenous neural progenitor cells residing in the subventricular zone along the anterior horn of the lateral ventricle (SVZ a) and induces neurogenesis in the postischemic striatum and cortex. Whether the adult primate brain preserves a similar ability in response to an ischemic insult is uncertain. We used the DNA synthesis indicator bromodeoxyuridine (BrdU) to label newly generated cells in adult macaque monkeys and show here that the proliferation of cells with a progenitor phenotype (double positive for BrdU and the markers Musashi 1, Nestin, and beta III-tubulin) in SVZ a increased during the second week after a 20-min transient global brain ischemia. Subsequent progenitor migration seemed restricted to the rostral migratory stream toward the olfactory bulb and ischemia increased the proportion of adult-generated cells retaining their location in SVZ a with a progenitor phenotype. Despite the lack of evidence for progenitor cell migration toward the postischemic striatum or prefrontal neocortex, a small but sustained proportion of BrdU-labeled cells expressed features of postmitotic neurons (positive for the protein Neu N and the transcription factors Tbr 1 and Islet 1) in these two regions for at least 79 days after ischemia. Taken together, our data suggest an enhanced neurogenic response in the adult primate telencephalon after a cerebral ischemic insult.

Abstracts

Abstracts

Stem and progenitor cell–based therapy of the human central nervous system

Multipotent neural stem cells, capable of giving rise to both neurons and glia, line the cerebral ventricles of all adult animals, including humans. In addition, distinct populations of nominally glial progenitor cells, which also have the capacity to generate several cell types, are dispersed throughout the subcortical white matter and cortex. A number of approaches have evolved for using neural progenitor cells in cell therapy. Four strategies are especially attractive for clinical translation: first, transplantation of oligodendrocyte progenitor cells as a means of treating the disorders of myelin; second, transplantation of phenotypically restricted neuronal progenitor cells to treat diseases of discrete loss of a single neuronal phenotype, such as Parkinson disease; third, implantation of mixed progenitor pools to treat diseases characterized by the loss of several discrete phenotypes, such as spinal cord injury; and fourth, mobilization of endogenous neural progenitor cells to restore neurons lost as a result of neurodegenerative diseases, in particular Huntington disease. Together, these may present the most compelling strategies and near-term disease targets for cell-based neurological therapy.

Stromal Cell-Derived Factor 1α Mediates Neural Progenitor Cell Motility after Focal Cerebral Ischemia

In the adult rodent, stroke induces an increase in endogenous neural progenitor cell (NPC) proliferation in the subventricular zone (SVZ) and neuroblasts migrate towards the ischemic boundary. We investigated the role of stromal cell-derived factor 1alpha (SDF-1alpha) in mediating NPC migration after stroke. We found that cultured NPCs harvested from the normal adult SVZ, when they were overlaid onto stroke brain slices, exhibited significantly (P<0.01) increased migration (67.2+/-25.2 microm) compared with the migration on normal brain slices (29.5+/-29.5 microm). Immunohistochemistry showed that CXCR 4, a receptor of SDF-1alpha, is expressed in the NPCs and migrating neuroblasts in stroke brain. Blocking SDF-1alpha by a neutralizing antibody against CXCR 4 significantly attenuated stroke-enhanced NPC migration. ELISA analysis revealed that SDF-1alpha levels significantly increased (P<0.01) in the stroke hemisphere (43.6+/-6.5 pg/mg) when compared with the normal brain (25.2+/-1.9 pg/mg). Blind-well chamber assays showed that SDF-1alpha enhanced NPC migration in a dose-dependent manner with maximum migration at a dose of 500 ng/mL. In addition, SDF-1alpha induced directionally selective migration. These findings show that SDF-1alpha generated in the stroke hemisphere may guide NPC migration towards the ischemic boundary via binding to its receptor CXCR 4 in the NPC. Thus, our data indicate that SDF-1alpha/CXCR 4 is important for mediating specific migration of NPCs to the site of ischemic damaged neurons.

Intrastriatal transforming growth factor alpha delivery to a model of Parkinson's disease induces proliferation and migration of endogenous adult neural progenitor cells without differentiation into dopaminergic neurons.

We examined the cell proliferative, neurogenic, and behavioral effects of transforming growth factor alpha (TGFalpha) in a 6-OHDA Parkinson's disease model when compared with naive rats. Intrastriatal TGFalpha infusion induced significant proliferation, hyperplastic nodules, and substantial migratory waves of nestin-positive progenitor cells from the adult subventricular zone (SVZ) of dopamine-denervated rats. Interestingly, SVZ cells in naive rats displayed proliferation but minimal migration in response to the TGFalpha infusion. The cells in the expanded SVZ accumulated cytoplasmic beta-catenin, indicating activation of classical Wnt signaling. However, no evidence of any neuronal differentiation was found of these recruited progenitor cells anywhere examined in the brain. Consequently, no evidence of dopaminergic (DA) neurogenesis was found in the striatum or substantia nigra in any experimental group, and amphetamine-induced behavioral rotations did not improve. In summary, the cells in the TGFalpha-induced migratory cellular wave remain undifferentiated and do not differentiate into midbrain-like DA neurons.

230. Neural Progenitor Cell Transduction with AAV Serotypes 1 and 4

The mucopolysaccharidoses (MPS) and the ceroid lipofuscinoses (NCLs) are devastating childhood onset diseases. Some forms of MPS and all NCLs have a severe CNS component. MPS VII, or beta-glucuronidase deficiency, and late-infantile NCL, or tripeptidyl protease deficiency are due to mutations in mRNAs encoding soluble lysosomal enzymes. Prior work in our laboratory and others' demonstrated that overexpression of beta-glucurondiase or TPP-1 from transduced cells in brain can lead to enzyme activity in non-transduced cells remote from the injection site, and improvements in cellular pathology and behavioral deficits. This occurs through a process called cross-correction. We hypothesized that cross-correction could also occur from gene-corrected endogenous neural progenitor cells (NPCs). Transduction of endogenous NPCs with virus expressing beta-glucuronidase or TPP-1 may allow enzyme secretion at several sites: 1) in the SVZ (with enzyme secreted into the ventricular system); 2) during migration through the corpus callosum (with enzyme secreted along the extensive white matter tracts of the corpus callosum); and 3) from differentiated neurons in the olfactory bulb (OB). We tested AAV1 and AAV4 for their ability to target endogenous neural progenitors. AAV4 vector injected unilateral into the lateral ventricle of adult or P0 C57BL/6 mice resulted in highly specific transduction of ependymal cells along the ventricular wall. Only scattered transgene positive cells were observed in the rostral migratory stream (RMS) and olfactory bulb in tissues harvested from several days to 8 weeks after gene transfer, regardless of injection time. Transgene positive cells did not express neuronal cell marker, indicating that NPCs were not a major target of AAV4 transduction in vivo. In contrast to AAV4, transgene positive migrating neuroblasts and olfactory bulb neurons were obvious after unilateral intraventricular injection of AAV1. However, numbers remained too few to consider AAV1-transduced NPCs as a significant source of recombinant lysosomal enzymes. Thus, transduction of endogenous NPCs with AAV4 does not occur, and with AAV1 is limited, preclude the use of these vectors for therapeutic application via NPCs.

Spinal cord injury models: neurophysiology.

Spinal cord injury models: neurophysiology.