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Transplanted multipotent human fetal neural stem cells (hfNSCs) significantly improved the function of parkinsonian monkeys in a prior study primarily by neuroprotection, with only 3%–5% of cells expressing a dopamine (DA) phenotype. In this paper, we sought to determine whether further manipulation of the neural microenvironment by overexpression of a developmentally critical molecule, glial cell-derived neurotrophic factor (GDNF), in the host striatum could enhance DA differentiation of hfNSCs injected into the substantia nigra and elicit growth of their axons to the GDNF-expressing target. hfNSCs were transplanted into the midbrain of 10 green monkeys exposed to 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine. GDNF was delivered concomitantly to the striatum via an adeno-associated virus serotype 5 vector, and the fate of grafted cells was assessed after 11 months. Donor cells remained predominantly within the midbrain at the injection site and sprouted numerous neurofilament-immunoreactive fibers that appeared to course rostrally toward the striatum in parallel with tyrosine hydroxylase-immunoreactive fibers from the host substantia nigra but did not mature into DA neurons. This work suggests that hfNSCs can generate neurons that project long fibers in the adult primate brain. However, in the absence of region-specific signals and despite GDNF overexpression, hfNSCs did not differentiate into mature DA neurons in large numbers. It is encouraging, however, that the adult primate brain appeared to retain axonal guidance cues. We believe that transplantation of stem cells, specifically instructed ex vivo to yield DA neurons, could lead to reconstruction of some portion of the nigrostriatal pathway and prove beneficial for the parkinsonian condition.

BackgroundGender is increasingly recognized as an important influence on brain development, disease susceptibility, and response to pharmacologic/rehabilitative treatments. In regenerative medicine, it remains entirely unknown whether there is an interaction between transplanted stem cells and host gender that might bias efficacy and safety in some patients but not others.MethodsWe examined the role of recipient gender in a neonatal rat hypoxic-ischemic injury (HII) model, treated with female human neuronal stem cells (hNSCs), labeled with superparamagnetic iron oxide particles implanted into the contralateral cerebral ventricle. We monitored HII evolution (by magnetic resonance imaging, histopathology, behavioral testing) and hNSC fate (migration, replication, viability).ResultsRecipient gender after implantation did not influence the volume or location of ischemic injury (1, 30, or 90 d) or behavior (90 d). Superparamagnetic iron oxide labeling did not influence HII evolution. Implantation had its greatest benefit on mild/moderate injuries, which remained stable rather than increasing as in severe HII as is the natural history for such lesions.ConclusionOur results suggest that hNSC treatment (including using hNSCs that are prelabeled with iron to allow tracking in real time by magnetic resonance imaging) would be equally safe and effective for male and female human newborns with mild-to-moderate HII.

Cell therapy has attracted considerable interest as a promising therapeutic alternative for patients with Parkinson's disease (PD). Clinical studies have shown that grafted fetal neural tissue can achieve considerable biochemical and clinical improvements in PD. However, the source of fetal tissue grafts is limited and ethically controversial. Human parthenogenetic stem cells offer a good alternative because they are derived from unfertilized oocytes without destroying potentially viable human embryos and can be used to generate an unlimited supply of neural cells for transplantation. We have previously reported that human parthenogenetic stem cell-derived neural stem cells (hpNSCs) successfully engraft, survive long term, and increase brain dopamine (DA) levels in rodent and nonhuman primate models of PD. Here we report the results of a 12-month transplantation study of hpNSCs in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned African green monkeys with moderate to severe clinical parkinsonian symptoms. The hpNSCs manufactured under current good manufacturing practice (cGMP) conditions were injected bilaterally into the striatum and substantia nigra of immunosuppressed monkeys. Transplantation of hpNSCs was safe and well tolerated by the animals with no dyskinesia, tumors, ectopic tissue formation, or other test article-related serious adverse events. We observed that hpNSCs promoted behavioral recovery; increased striatal DA concentration, fiber innervation, and number of dopaminergic neurons; and induced the expression of genes and pathways downregulated in PD compared to vehicle control animals. These results provide further evidence for the clinical translation of hpNSCs and support the approval of the world's first pluripotent stem cell-based phase I/IIa study for the treatment of PD (Clinical Trial Identifier NCT02452723).

Increased global connectivity has catalyzed technological development in almost all industries, in part through the facilitation of novel collaborative structures. Notably, open innovation and crowd-sourcing-of expertise and/or funding-has tremendous potential to increase the efficiency with which biomedical ecosystems interact to deliver safe, efficacious and affordable therapies to patients. Consequently, such practices offer tremendous potential in advancing development of cellular therapies. In this vein, the CASMI Translational Stem Cell Consortium (CTSCC) was formed to unite global thought-leaders, producing academically rigorous and commercially practicable solutions to a range of challenges in pluripotent stem cell translation. Critically, the CTSCC research agenda is defined through continuous consultation with its international funding and research partners. Herein, initial findings for all research focus areas are presented to inform global product development strategies, and to stimulate continued industry interaction around biomanufacturing, strategic partnerships, standards, regulation and intellectual property and clinical adoption.

Globoid cell leukodystrophy (GLD) or Krabbe disease, is a fatal demyelinating disease attributed to mutations in the galactocerebrosidase (GALC) gene. Loss of function mutations in GALC result in accumulation of the glycolipid intermediate, galactosylsphingosine (psychosine). Due to the cytotoxicity of psychosine, it has been hypothesized that accumulated psychosine underlie the pathophysiology of GLD. However, the cellular mechanisms of GLD pathophysiology remain unclear. Globoid cells, multinucleated microglia/macrophages in the central nervous system (CNS), are a defining characteristic of GLD. Here we report that exposure of primary glial cultures to psychosine induces the expression and the production of matrix metalloproteinase (MMP)-3 that mediated a morphological transformation of microglia into a multinucleated globoid cell type. Additionally, psychosine-induced globoid cell formation from microglia was prevented by either genetic ablation or chemical inhibition of MMP-3. These effects are microglia-specific as peripheral macrophages exposed to psychosine did not become activated or express increased levels of MMP-3. In the brain from twitcher mice, a murine model of human GLD, elevated MMP-3 expression relative to wild-type littermates was contemporaneous with disease onset and further increased with disease progression. Further, bone marrow transplantation (BMT), currently the only therapeutically beneficial treatment for GLD, did not mitigate the elevated expression of MMP-3 in twitcher mice. Hence, elevated expression of MMP-3 in GLD may promote microglial responses to psychosine that may represent an important pathophysiological process in this disease and its treatment.

Human pluripotent stem cells (PSC) have the potential to revolutionize regenerative medicine. However undifferentiated PSC can form tumors and strict quality control measures and safety studies must be conducted before clinical translation. Here we describe preclinical tumorigenicity and biodistribution safety studies that were required by the US Food and Drug Administration (FDA) and Australian Therapeutic Goods Administration (TGA) prior to conducting a Phase I clinical trial evaluating the safety and tolerability of human parthenogenetic stem cell derived neural stem cells ISC-hpNSC for treating Parkinson’s disease (ClinicalTrials.gov Identifier NCT02452723). To mitigate the risk of having residual PSC in the final ISC-hpNSC population, we conducted sensitive in vitro assays using flow cytometry and qRT-PCR analyses and in vivo assays to determine acute toxicity, tumorigenicity and biodistribution. The results from these safety studies show the lack of residual undifferentiated PSC, negligible tumorigenic potential by ISC-hpNSC and provide additional assurance to their clinical application.

Capitalizing on cellular homing to cancer is a promising strategy for targeting malignant cells for diagnostic, monitoring and therapeutic purposes. Murine C17.2 neural progenitor cells (NPC) demonstrate a tropism for cell line-derived tumors, but their affinity for patient-derived tumors is unknown. We tested the hypothesis that NPC accumulate in patient-derived tumors at levels detectable by optical imaging. Mice bearing solid tumors after transplantation with patient-derived leukemia cells and untransplanted controls received 10(6) fluorescent DiR-labeled NPC daily for 1-4 days, were imaged, then sacrificed. Tissues were analyzed by immunofluorescence and flow cytometry to detect tumor cell engraftment (CD45) and NPC (FITC-β galactosidase or DiR). Tumors consisted primarily of CD45-positive cells and demonstrated mild fluorescence, corresponding to frequent clusters of FITC-β gal-positive cells. Both transplanted and control mice demonstrated the highest fluorescent signal in the spleens and other tissues of the reticuloendothelial activating system. However, only rare FITC-β gal-positive cells were detected in the mildly engrafted transplanted spleens and none in the control spleens, suggesting that their high DiR signal reflects the sequestration of DiR-positive debris. The mildly engrafted transplanted kidneys demonstrated low fluorescent signal and rare FITC-β gal-positive cells whereas control kidneys were negative. Results indicate that NPC accumulate in tissues containing patient-derived tumor cells in a manner that is detectable by ex vivo optical imaging and proportional to the level of tumor engraftment, suggesting a capacity to home to micrometastatic disease. As such, NPC could have significant clinical applications for the targeted diagnosis and treatment of cancer.

Access to unlimited numbers of live human neurons derived from stem cells offers unique opportunities for in vitro modeling of neural development, disease-related cellular phenotypes, and drug testing and discovery. However, to develop informative cellular in vitro assays, it is important to consider the relevant in vivo environment of neural tissues. Biomimetic 3D scaffolds are tools to culture human neurons under defined mechanical and physico-chemical properties providing an interconnected porous structure that may potentially enable a higher or more complex organization than traditional two-dimensional monolayer conditions. It is known that even minor variations in the internal geometry and mechanical properties of 3D scaffolds can impact cell behavior including survival, growth, and cell fate choice. In this report, we describe the design and engineering of 3D synthetic polyethylene glycol (PEG)-based and biodegradable gelatin-based scaffolds generated by a free form fabrication technique with precise internal geometry and elastic stiffnesses. We show that human neurons, derived from human embryonic stem (hESC) cells, are able to adhere to these scaffolds and form organoid structures that extend in three dimensions as demonstrated by confocal and electron microscopy. Future refinements of scaffold structure, size and surface chemistries may facilitate long term experiments and designing clinically applicable bioassays.

In a perspective of regenerative medicine, multipotent human neural progenitor cells (hNPCs) offer a therapeutic advantage over pluripotent stem cells in that they are already invariantly “neurally committed” and lack tumorigenicity. However, some of their intrinsic properties, such as slow differentiation and uncontrolled multipotency, remain among the obstacles to their routine use for transplantation. Although rodent NPCs have been genetically modified in vitro to overcome some of these limitations, the translation of this strategy to human cells remains in its early stages. In the present study, we compare the actions of 4 basic helix-loop-helix transcription factors on the proliferation, specification, and terminal differentiation of hNPCs isolated from the fetal dorsal telencephalon. Consistent with their proneural activity, Ngn1, Ngn2, Ngn3, and Mash1 prompted rapid commitment of the cells. The Ngns induced a decrease in proliferation, whereas Mash1 maintained committed progenitors in a proliferative state. As opposed to Ngn1 and Ngn3, which had no effect on glial differentiation, Ngn2 induced an increase in astrocytes in addition to neurons, whereas Mash1 led to both neuronal and oligodendroglial specification. GABAergic, cholinergic, and motor neuron differentiations were considerably increased by overexpression of Ngn2 and, to a lesser extent, of Ngn3 and Mash1. Thus, we provide evidence that hNPCs can be efficiently, rapidly, and safely expanded in vitro as well as rapidly differentiated toward mature neural (typically neuronal) lineages by the overexpression of select proneural genes.

Sandhoff Disease (SD) involves the CNS accumulation of ganglioside GM2 and asialo-GM2 (GA2) due to inherited defects in the β-subunit gene of β-hexosaminidase A and B (Hexb gene). Substrate reduction therapy, utilizing imino sugar N-butyldeoxygalactonojirimycin (NB-DGJ), reduces ganglioside biosynthesis and levels of stored GM2 in SD mice. Intracranial transplantation of Neural Stem Cells (NSCs) can provide enzymatic cross correction, to help reduce ganglioside storage and extend life. Here we tested the effect of NSCs and NB-DGJ, alone and together, on brain β-hexosaminidase activity, GM2, and GA2 content in juvenile SD mice. The SD mice received either cerebral NSC transplantation at post-natal day 0 (p-0), intraperitoneal injection of NB-DGJ (500 mg/kg/day) from p-9 to p-15, or received dual treatments. The brains were analyzed at p-15. β-galactosidase staining confirmed engraftment of lacZ-expressing NSCs in the cerebral cortex. Compared to untreated and sham-treated SD controls, NSC treatment alone provided a slight increase in Hex activity and significantly decreased GA2 content. However, NSCs had no effect on GM2 content when analyzed at p-15. NB-DGJ alone had no effect on Hex activity, but significantly reduced GM2 and GA2 content. Hex activity was slightly elevated in the NSC + drug-treated mice. GM2 and GA2 content in the dual treated mice were similar to that of the NB-DGJ treated mice. These data indicate that NB-DGJ alone was more effective in targeting storage in juvenile SD mice than were NSCs alone. No additive or synergistic effect between NSC and drug was found in these juvenile SD mice.

BACKGROUND There are currently no satisfactory treatments or experimental models showing autonomic dysfunction for intramedullary spinal cord gliomas (ISCG). OBJECTIVE To develop a rat model of ISCG and investigate whether genetically engineered human neural stem cells (F3.hNSCs) could be developed into effective therapies for ISCG. METHODS Immunodeficient/Rowett Nude rats received C6 implantation of G55 human glioblastoma cells (10K/each). F3.hNSCs engineered to express either cytosine deaminase gene only (i.e., F3.CD) or dual genes of CD and thymidine kinase (i.e., F3.CD-TK) converted benign 5-fluorocytosine and ganciclovir into oncolytic 5-fluorouracil and ganciclovir-triphosphate, respectively. ISCG rats received injection of F3.CD-TK, F3.CD, or F3.CD-TK debris near the tumor epicenter 7 days after G55 seeding, followed with 5-FC (500 mg/kg/5 mL) and ganciclovir administrations (25 mg/kg/1 mL/day × 5/each repeat, intraperitoneal injection). Per humane standards for animals, loss of weight-bearing stepping in the hindlimb was used to determine post-tumor survival. Also evaluated were autonomic functions and tumor growth rate in vivo. RESULTS ISCG rats with F3.CD-TK treatment survived significantly longer (37.5 ± 4.78 days) than those receiving F3.CD (21.5 ± 1.75 days) or F3.CD-TK debris (19.3 ± 0.85 days; n = 4/group; P < .05, median rank test), with significantly improved autonomic function and reduced tumor growth rate. F3.DC-TK cells migrated diffusively into ISCG clusters to mediate oncolytic effect. CONCLUSION Dual gene-engineered human neural stem cell regimen markedly prolonged survival in a rat model that emulates somatomotor and autonomic dysfunctions of human cervical ISCG. F3.CD-TK may provide a novel approach to treating clinical ISCG. ABBREVIATIONS 5FC, 5-fluorocytosineBBB, Basso, Beattie, and BresnahanCD, cytosine deaminaseDP, diastolic blood pressureGCV, ganciclovir; hNSCs, human neural stem cellsISCG, intramedullary spinal cord gliomasMAP, mean arterial blood pressureNSCs, neural stem cellsSP, systolic blood pressureTK, thymidine kinase.

The history of Parkinson's disease (PD) therapeutics might be said to typify much of the history of clinical medicine in general. On page 891 of this issue, Mittal et al. ( 1 ), true to that tradition, provide an intriguing, unexpected, and potentially highly impactful observation that will likely form the basis of clinical practice in PD patients long before we have a true grasp on the mechanism of action (MOA).

Cellular signaling is largely controlled by protein phosphorylation. This post-translational modification (PTM) has been extensively analyzed when examining one or a few protein phosphorylation events that effect cell signaling. However, protein kinase-driven signaling networks, comprising total (phospho)proteomes, largely control cell fate. Therefore, large-scale analysis of differentially regulated protein phosphorylation is central to elucidating complex cellular events, including maintenance of pluripotency and differentiation of embryonic stem cells (ESCs). The current technology of choice for total phosphoproteome and combined total proteome plus total phosphoproteome (termed (phospho)proteome)1 analyses is multidimensional liquid chromatography- (MDLC) tandem mass spectrometry (MS/MS).Advances in the use of MDLC for separation of peptides comprising total (phospho)proteomes, phosphopeptide enrichment, separation of enriched fractions, and quantitative peptide identification by MS/MS have been rapid in recent years, as have improvements in the sensitivity, speed, and accuracy of mass spectrometers. Increasingly deep coverage of (phospho)proteomes is allowing an improved understanding of changes in protein phosphorylation networks as cells respond to stimuli and progress from one undifferentiated or differentiated state to another. Although MDLC-MS/MS studies are powerful, understanding the interpretation of the data is important, and targeted experimental pursuit of biological predictions provided by total (phospho)proteome analyses is needed.(Phospho)proteomic analyses of pluripotent stem cells are in their infancy at this time. However, such studies have already begun to contribute to an improved and accelerated understanding of basic pluripotent stem cell signaling and fate control, especially at the systems-biology level.

Identifying the molecular and cellular basis of complex neuropsychiatric disorders (cNPDs) has been limited by the inaccessibility of central neurons, variability within broad diagnostic classifications, and the interplay of genetic and environmental factors. Recent work utilizing neuronally differentiated human induced pluripotent stem cells (hiPSCs) from Mendelian and polygenic cNPDs is beginning to illuminate neuritic, synaptic or cell body variations accompanied by specific gene or protein expression alterations largely mimicking known pathology. In some cases, phenotypes have only emerged after application of cellular stress or long duration of differentiation. Pathological and cellular expression features are fully or partially responsive to pharmacological treatment highlighting the potential utility of differentiated hiPSCs for discovery of personalized therapeutics and for identifying pathogenetically relevant targets in subgroups of patients within a broad syndromic classification. Because of the inherent variability in developing and differentiating hiPSC lines and the multiple comparisons implicit in 'omics' technologies, rigorous algorithms for assuring statistical significance and independent confirmation of results, will be required for robust modeling of cNPDs.

Human embryonic stem cells (hESCs) are genetically stable with unlimited expansion ability and unrestricted plasticity, proffering a pluripotent reservoir for in vitro derivation of a large supply of disease-targeted human somatic cells that are restricted to the lineage in need of repair. There is a large healthcare need to develop hESC-based therapeutic solutions to provide optimal regeneration and reconstruction treatment options for the damaged or lost tissue or organ that have been lacking. In spite of controversy surrounding the ownership of hESCs, the number of patent applications related to hESCs is growing rapidly. This review gives an overview of different patent applications on technologies of derivation, maintenance, differentiation, and manipulation of hESCs for therapies. Many of the published patent applications have been based on previously established methods in the animal systems and multi-lineage inclination of pluripotent cells through spontaneous germ-layer differentiation. Innovative human stem cell technologies that are safe and effective for human tissue and organ regeneration in the clinical setting remain to be developed. Our overall view on the current patent situation of hESC technologies suggests a trend towards hESC patent filings on novel therapeutic strategies of direct control and modulation of hESC pluripotent fate, particularly in a 3-dimensional context, when deriving clinically-relevant lineages for regenerative therapies.

In the field of induced potency and fate reprogramming, it remains unclear what the best starting cell might be and to what extent a cell need be transported back to a more primitive state for translational purposes. Reprogramming a committed cell back to pluripotence to then instruct it toward a particular specialized cell type is demanding and may increase risks of neoplasia and undesired cell types. Precursor/progenitor cells from the organ of therapeutic concern typically lack only one critical attribute—the capacity for sustained self-renewal. We speculated that this could be induced in a regulatable manner such that cells proliferate only in vitro and differentiate in vivo without the need for promoting pluripotence or specifying lineage identity. As proof-of-concept, we generated and tested the efficiency, safety, engraftability, and therapeutic utility of “induced conditional self-renewing progenitor (ICSP) cells” derived from the human central nervous system (CNS); we conditionally induced self-renewal efficiently within neural progenitors solely by introducing v- myc tightly regulated by a tetracycline (Tet)- on gene expression system. Tet in the culture medium activated myc transcription and translation, allowing efficient expansion of homogeneous, clonal, karyotypically normal human CNS precursors ex vivo; in vivo, where Tet was absent, myc was not expressed, and self-renewal was entirely inactivated (as was tumorigenic potential). Cell proliferation ceased, and differentiation into electrophysiologically active neurons and other CNS cell types in vivo ensued upon transplantation into rats, both during development and after adult injury—with functional improvement and without neoplasia, overgrowth, deformation, emergence of non-neural cell types, phenotypic or genomic instability, or need for immunosuppression. This strategy of inducing self-renewal might be applied to progenitors from other organs and may prove to be a safe, effective, efficient, and practical method for optimizing insights gained from the ability to reprogram cells.

Three modes for cryopreservation (CP) of human iPSC cells have been compared:STD: standard CP of small clumps with 10% of CPA in cryovials,ACC: dissociation of the cells with Accutase and freezing in cryovials, andPLT: programmed freezing of adherent cells in plastic multiwell dishes in a programmable freezer using one- and multistep cooling protocols. Four CPAs were tesetd: dimethyl sulfoxide (DMSO), ethylene glycol (EG), propylene glycol (PG), and glycerol (GLY). The cells inACCandPLTwere frozen and recovered after thawing in the presence of a ROCK inhibitor Y-27632 (RI). EG was less toxic w/o CP cryopreservation than DMSO and allowed much better maintenance of pluripotency after CP than PG or GLY. The cells were cryopreserved very efficiently as adherent cultures (+RI) in plates (5-6-fold higher than STD) using EG and a 6-step freezing protocol. Recovery under these conditions is comparable or even higher than ACC+RI.Conclusions. Maintenance of cell-substratum adherence is a favorable environment that mitigates freezing and thawing stresses (ComfortFreeze®concept developed by CELLTRONIX). CP of cells directly in plates inready-to-goafter thawing format for HT/HC screening can be beneficial in many SC-related scientific and commercial applications such as drug discovery and toxicity tests.

Objective: Quantitative magnetic resonance imaging (MRI) can serially and noninvasively assess the degree of injury in rat pup models of hypoxic ischemic injury (HII). It can also noninvasively monitor stem cell migration following iron oxide prelabeling. Reports have shown that neural stem cells (NSCs) may help mediate neuroprotection or stimulate neuroreparative responses in adult and neonatal models of ischemic injury. We investigated the ability of high-field MRI to monitor and noninvasively quantify the migration, proliferation, and location of iron oxide–labeled NSCs over very long time periods (58 weeks) in real time while contemporaneously correlating this activity with the evolving severity and extent of neural damage. Methods: Labeled clonal murine NSCs (mNSCs) were implanted 3 days after unilateral HII in 10-day-old rat pups into the contralateral striatum or ventricle. We developed methods for objectively quantifying key aspects of dynamic NSC behavior (eg, viability; extent, and speed of migration; degree of proliferation; extent of integration into host parenchyma). MRI images were validated with histological and immunohistochemical assessments. Results: mNSCs rapidly migrated (100 lm/day) to the lesion site. Chains of migrating NSCs were observed in the corpus callosum. In pups subjected to HII, though not in intact control animals, we observed a 273% increase in the MR-derived volume of mNSCs 4 weeks after implantation (correlating with the known proliferative behavior of endogenous and exogenous NSCs) that slowly declined over the 58-week time course, with no adverse consequences. Large numbers of now quiescent mNSCs remained at the site of injury, many retaining their iron oxide label. Interpretation: Our studies demonstrate that MRI can simultaneously monitor evolving neonatal cerebral injury as well as NSC migration and location. Most importantly, it can noninvasively monitor proliferation dynamically for prolonged time periods. To be able to pursue clinical trials in newborns using stem cell therapies it is axiomatic that safety be insured through the long-term real time monitoring of cell fate and activity, particularly with regard to observing unanticipated risks to the developing brain. This study supports the feasibility of reliably using MRI for this purpose. ANN NEUROL 2010;00:000–000

SummaryThe molecular pathways controlling cerebellar Purkinje cell dendrite formation and maturation are poorly understood. The Purkinje cell degeneration (pcd) mutant mouse is characterized by mutations in Nna1, a gene discovered in an axonal regenerative context, but whose actual function in development and disease is unknown. We found abnormal development of Purkinje cell dendrites in postnatal pcdSid mice and linked this deficit to a deletion mutation in exon 7 of Nna1. With single cell gene profiling and virus-based gene transfer, we analyzed a molecular pathway downstream to Nna1 underlying abnormal Purkinje cell dendritogenesis in pcdSid mice. We discovered that mutant Nna1 dramatically increases intranuclear localization of lysyl oxidase propeptide, which interferes with NF-κB RelA signaling and microtubule-associated protein regulation of microtubule stability, leading to underdevelopment of Purkinje cell dendrites. These findings provide insight into Nna1's role in neuronal development and why its absence renders Purkinje cells more vulnerable.

Epigenetic parameters (DNA methylation, histone modifications, and miRNAs) play a significant role in cancer. To identify the common epigenetic signatures of both the individual matrix metalloproteinases (MMPs) and the additional genes, the function of which is also linked to proteolysis, migration, and tumorigenesis, we performed epigenetic profiling of 486 selected genes in unrelated non-migratory MCF-7 breast carcinoma and highly migratory U251 glioma cells. Genome-wide transcriptional profiling, quantitative reverse transcription-PCR, and microRNA analyses were used to support the results of our epigenetic studies. Transcriptional silencing in both glioma and breast carcinoma cells predominantly involved the repressive histone H3 Lys-27 trimethylation (H3K27me3) mark. In turn, epigenetic stimulation was primarily performed through a gain in the histone H3 Lys-4 dimethylation (H3K4me2) and H3 hyperacetylation and by a global reduction of H3K27me3. Inactive pro-invasive genes in MCF-7 cells but not in U251 cells frequently exhibited a stem cell-like bivalent mark (enrichment in both H3K27me3 and H3K4me2), a characteristic of developmental genes. In contrast with other MMPs, MMP-8 was epigenetically silenced in both cell types, thus providing evidence for the strict epigenetic control of this anti-tumorigenic proteinase in cancer. Epigenetic stimulation of multiple collagen genes observed in cultured glioma cells was then directly confirmed using orthotopic xenografts and tumor specimens. We suggest that the epigenetic mechanisms allow gliomas to deposit an invasion-promoting collagen-enriched matrix and then to use this matrix to accomplish their rapid migration through the brain tissue.

Aim: To determine whether transcriptional reprogramming is capable of reversing the developmental aging of normal human somatic cells to an embryonic state. Materials & methods: An isogenic system was utilized to facilitate an accurate assessment of the reprogramming of telomere restriction fragment (TRF) length of aged differentiated cells to that of the human embryonic stem (hES) cell line from which they were originally derived. An hES-derived mortal clonal cell strain EN13 was reprogrammed by SOX2, OCT4 and KLF4. The six resulting induced pluripotent stem (iPS) cell lines were surveyed for telomere length, telomerase activity and telomere-related gene expression. In addition, we measured all these parameters in widely-used hES and iPS cell lines and compared the results to those obtained in the six new isogenic iPS cell lines. Results: We observed variable but relatively long TRF lengths in three widely studied hES cell lines (16.09–21.1 kb) but markedly shorter TRF lengths (6.4–12.6 kb) in five similarly widely studied iPS cell lines. Transcriptome analysis comparing these hES and iPS cell lines showed modest variation in a small subset of genes implicated in telomere length regulation. However, iPS cell lines consistently showed reduced levels of telomerase activity compared with hES cell lines. In order to verify these results in an isogenic background, we generated six iPS cell clones from the hES-derived cell line EN13. These iPS cell clones showed initial telomere lengths comparable to the parental EN13 cells, had telomerase activity, expressed embryonic stem cell markers and had a telomere-related transcriptome similar to hES cells. Subsequent culture of five out of six lines generally showed telomere shortening to lengths similar to that observed in the widely distributed iPS lines. However, the clone EH3, with relatively high levels of telomerase activity, progressively increased TRF length over 60 days of serial culture back to that of the parental hES cell line. Conclusion: Prematurely aged (shortened) telomeres appears to be a common feature of iPS cells created by current pluripotency protocols. However, the spontaneous appearance of lines that express sufficient telomerase activity to extend telomere length may allow the reversal of developmental aging in human cells for use in regenerative medicine.

The inference of transcriptional networks that regulate transitions into physiological or pathological cellular states remains a central challenge in systems biology. A mesenchymal phenotype is the hallmark of tumour aggressiveness in human malignant glioma, but the regulatory programs responsible for implementing the associated molecular signature are largely unknown. Here we show that reverse-engineering and an unbiased interrogation of a glioma-specific regulatory network reveal the transcriptional module that activates expression of mesenchymal genes in malignant glioma. Two transcription factors (C/EBPbeta and STAT3) emerge as synergistic initiators and master regulators of mesenchymal transformation. Ectopic co-expression of C/EBPbeta and STAT3 reprograms neural stem cells along the aberrant mesenchymal lineage, whereas elimination of the two factors in glioma cells leads to collapse of the mesenchymal signature and reduces tumour aggressiveness. In human glioma, expression of C/EBPbeta and STAT3 correlates with mesenchymal differentiation and predicts poor clinical outcome. These results show that the activation of a small regulatory module is necessary and sufficient to initiate and maintain an aberrant phenotypic state in cancer cells.

Although we and others have demonstrated that neural stem cells (NSCs) may impact such neurogenetic conditions as lysosomal storage diseases when transplanted at birth, it has remained unclear whether such interventions can impact well-established mid-stage disease, a situation often encountered clinically. Here we report that when NSCs were injected intracranially into the brain of adult symptomatic Sandhoff (Hexb−/−) mice, cells migrated far from the injection site and integrated into the host cytoarchitecture, restoring β-hexosaminidase enzyme activity and promoting neuropathologic and behavioral improvement. Mouse lifespan increased, neurological function improved, and disease progression was slowed. These clinical benefits correlated with neuropathological correction at the cellular and molecular levels, reflecting the multiple potential beneficial actions of stem cells, including enzyme cross-correction, cell replacement, tropic support, and direct anti-inflammatory action. Pathotropism (i.e., migration and homing of NSCs to pathological sites) could be imaged in real time by magnetic resonance imaging. Differentially expressed chemokines might play a role in directing the migration of transplanted stem cells to sites of pathology. Significantly, the therapeutic impact of NSCs implanted in even a single location was surprisingly widespread due to both cell migration and enzyme diffusion. Because many of the beneficial actions of NSCs observed in newborn brains were recapitulated in adult brains to the benefit of Sandhoff recipients, NSC-based interventions may also be useful in symptomatic subjects with established disease. Disclosure of potential conflicts of interest is found at the end of this article.

Neural progenitor cells (NPCs) have been investigated as potential vehicles for brain tumor therapy because they have been shown to migrate toward central nervous system gliomas and can be genetically engineered to deliver cytotoxic agents to tumors. The mechanisms that regulate migration of NPCs to tumors are not fully understood. By means of microarray analysis, polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry, we found that monocyte chemoattractant protein-1 (MCP-1/CCL-2) was expressed in experimental brain tumor cells in vivo and in vitro. CCR2, the receptor for MCP-1, was expressed on C17.2 NPCs. We used a modified Boyden chamber assay and found increased migration of NPCs in vitro in response to MCP-1. By means of an in vivo model for NPC migration, we found evidence of NPC migration toward areas of MCP-1 infusion in rat brains. An understanding of NPC migration mechanisms may be used to enhance delivery of cytotoxic agents to brain tumor cells.

Neonatal global or focal hypoxic-ischemic brain injury remains a frequent and devastating condition, with serious long-term sequelae. An important issue in any neonatal clinical trial of neuroprotective agents relates to developing accurate measures of injury severity and also suitable measures of the response to treatment. Advanced magnetic resonance imaging techniques can acquire serial and noninvasive data about brain structure, metabolic activity, and the response to injury or treatment. These imaging methods need validation in appropriate animal models for translational research studies in human newborns. This review describes several approaches that use imaging as well as proton magnetic resonance spectroscopy to assess the severity of ischemic injury (e.g., for possible candidate selection) and for monitoring the progression and evolution of injury over time and as an indicator of recovery or response to treatment. Preliminary data are presented on how imaging can be used after neural stem cell implantation to characterize the migration rate, the magnitude of stem cell proliferation, and their final location. Imaging has the potential to allow monitoring of many dimensions of neuroprotective treatments and can be expected to contribute to efficacy and safety when clinical trials using neural stem cells or other neuroprotective agents become available.

We and others have reported that neural stem/progenitor cells (NSCs) may exert direct anti-inflammatory activity. This action has been attributed, in part, to T-cell suppression. However, how T-cells become suppressed by NSCs remains unresolved. In this study, we explored one of these mechanisms and challenged some previously advanced hypotheses regarding underlying NSC-mediated T-cell suppression. We employed an easily observable and manipulatable system in which activated and non-activated T-cells were co-cultured with a stable well-characterized clone of lacZ-expressing murine NSCs. As in previous reports, NSCs were found to inhibit T-cell proliferation. However, this inhibition by NSCs was not due to suppression of T cell activation or induction of apoptosis of T cells during the early activation stage. High levels of nitric oxide (NO) and prostaglandin E2 (PGE2) were induced in the T cells when co-cultured with NSCs. In addition, inducible NOS (iNOS) and microsomal type 1 PGES (mPGES-1) were readily detected in NSCs in co-culture with T-cells, but not at all in NSCs cultured alone or in activated T cells cultured with or without NSCs. This finding suggested that activated T cells induced NO and PGE2 production in the NSCs. Furthermore, T-cell proliferation inhibited by co-culture with the NSCs was significantly restored by inhibitors of NO and PGE2 production. Therefore, NSCs appear to suppress T-cells, at least in part, by NO and PGE2 production which, in turn, would account for the well-documented reduction of central nervous system immunopathology by transplanted NSCs.

Schwann cells and primary progenitor cells improve regeneration across peripheral nerve defects. This study examined the impact of immortalized neural precursor cells on regeneration of rat nerve defects. Across 10-mm gaps, neuromas formed without neural cables with C17.2- or RN33B-transplanted cells, but neural cables formed across 5-mm gaps seeded with RN33B cells. In vitro, dorsal root ganglia neurites elongated across Schwann and RN33B cells; RN33B cells induced neurite branching with shorter total outgrowth. Neural cable formation in vivo was likely determined by the balance of guidance and branch-inducing factors secreted by Schwann and transplanted precursor cells.

Neural stem cells (NSCs) are the main vehicle for genetic and molecular therapies in the central nervous system (CNS). The sustainability of NSCs has been ensured through genetic manipulation both in vitro and in vivo. NSC lines have also been immortalized and controlled for cell growth in similar fashion. Their potential to differentiate and their genetic plasticity make them the modality of choice for cellular transplantation. After transplantation, NSCs also exhibit inherent long-distance migratory capabilities and a remarkable capacity to integrate into brain structures. This makes NSCs the ideal candidate for delivery and expression of therapeutic genes. Mouse models of CNS diseases have already demonstrated the efficacy of such NSC-mediated treatment, and further investigations are underway to bridge the gap into true clinical application. Finally, the imaging possibilities with NSC transplants are endless, and they will be a pivotal component to safe and effective human transplantation. This paper provides an overview on NSCs and the various methods in which they have been genetically manipulated for biological investigation.

Most cases of hearing loss are caused by the death or dysfunction of one of the many cochlear cell types. We examined whether cells from a neural stem cell line could replace cochlear cell types lost after exposure to intense noise. For this purpose, we transplanted a clonal stem cell line into the scala tympani of sound damaged mice and guinea pigs. Utilizing morphological, protein expression and genetic criteria, stem cells were found with characteristics of both neural tissues (satellite, spiral ganglion, and Schwann cells) and cells of the organ of Corti (hair cells, supporting cells). Additionally, noise-exposed, stem cell-injected animals exhibited a small but significant increase in the number of satellite cells and Type I spiral ganglion neurons compared to non-injected noise-exposed animals. These results indicate that cells of this neural stem cell line migrate from the scala tympani to Rosenthal's canal and the organ of Corti. Moreover, they suggest that cells of this neural stem cell line may derive some information needed from the microenvironment of the cochlea to differentiate into replacement cells in the cochlea.

In order to evaluate the phenotypic effects of implanted neural stem cells (NSCs) in the mouse model of Niemann-Pick C (NPC) disease, we injected a well-characterized clone of murine NSCs into the cerebella of neonatal Npc1(-/-) and control mice. The implanted cells survived and were abundant in some regions of the cerebellum. Life span was lengthened in NPC mice with the implanted NSCs. However, the rate of weight gain and subsequent weight loss, resulting from neurodegeneration, was not significantly different from un-injected controls. Ataxia was measured by Rota-Rod performance. The overall rate of decline in time on the Rota-Rod was not significantly slowed down. Thus, in this small group of NPC mice, a single administration in the neonatal period of the NSCs (which were not engineered to over-express the missing gene and not directed into the parenchyma) was only partially therapeutic.

Stem cells provide us with a future alternative to more traditional pharmacology for treatment of a wide range of pathology that occurs within the central nervous system (CNS). The ability to not only, minimize neuronal and glial degeneration and loss, but also to repair and regenerate the diseases nervous system is currently the investigational horizon for regenerative medicine. For this, neural stem cells (NSCs) that can be derived either from the CNS itself or from pluripotent embryonic stem cells (ESCs), are promising candidates. Their ability to ameliorate disease symptoms and to improve functional recovery has been demonstrated in various animal models of traumatic and ischemic CNS injury and neurodegeneration involving neuronal and glial cells. Further, the possibility of recruiting endogenous stem cells to compliment stem cell transplantation is providing additional promise to the future of stem cell mediated regenerative medicine.

Stem cells, by virtue of their defining property of self-renewal, represent an unlimited source of potentially functional human cells for basic research and regenerative medicine. Having validated the feasibility of cell-based therapeutic strategies over the past decade, mostly through the use of rodent cells, the stem cell field has now embarked upon a detailed characterization of human cells. Recent progress has included improved cell culture conditions, long-term propagation, directed differentiation, and transplantation of both human embryonic and somatic stem cells. Continued progress in understanding basic human stem cell biology, combined with a better handle on the fundamental pathophysiology of human diseases one wishes to target (including the use of human stem cells in primate and other large animal models of human disease), should help to move this technology closer to clinical application.

Amniotic fluid contains multiple cell types derived from the developing fetus, including some that can give rise to differentiated adipose, muscle, bone, and neuronal cell lines. The present investigators have identified lines of broadly multipotent amniotic fluid-derived stem (AFS) cells that can give rise to a wide range of lineages including those in all embryonic germ layers, thereby meeting the criterion for pluripotent stem cells. Immunoselection with magnetic microspheres was used to isolate, from cultures of human amniocentesis specimens taken for prenatal genetic diagnosis, cells bearing the surface antigen c-Kit, the receptor for stem cell factor. Flow cytometry served to assess markers expressed by human AFS cells. AFS cells from 19 amniocentesis donors were able to differentiate along adipogenic, osteogenic, myogenic, endothelial, neurogenic, and hepatic pathways. Induced differentiation along multiple pathways was documented by the expression of mRNAs for lineage-specific genes. Multilineage differentiation was characteristic of AFS cells that were cloned by limiting dilution. Studies based on marking with a retroviral vector confirmed that cloned AFS cells and their differentiated derivatives did in fact descend from a single cell, and that the AFS cells are pluripotent stem cells. Feeders were not necessary for the undifferentiated AFS cells to expand extensively. The cells doubled in 36 hours and were not tumorigenic. Lines maintained for more than 250 population doublings continued to have long telomeres and normal karyotypes. The differentiated cells derived from AFS cells included neuronal lineage cells secreting the neurotransmitter L-glutamate or expressing G-protein-gated inwardly rectifying potassium channels, hepatic lineage cells producing urea, and osteogenic lineage cells that formed tissue-engineered bone. These studies affirm that stem cells capable of extensive self-renewal can routinely be obtained from human amniotic fluid. AFS cells can serve as precursors to a broad range of differentiated cell types that potentially have therapeutic applications. Banking of cells that would otherwise be discarded could provide a convenient source not only for autologous treatment later in life, but for matching of histocompatible donor cells with prospective recipients.

Reference EPFL-CONF-214231View record in Web of Science Record created on 2015-12-02, modified on 2017-05-25

Recent studies indicate that human pluripotent stem cell (PSC)-based therapies hold great promise in Parkinson's disease (PD). Clinical studies have shown that grafted fetal neural tissue can achieve considerable biochemical and clinical improvements in PD. However, the source of fetal tissue grafts is limited and ethically controversial. Human parthenogenetic stem cells offer a good alternative because they are derived from unfertilized oocytes without destroying viable human embryos and can be used to generate an unlimited supply of neural stem cells for transplantation. Here we evaluate for the first time the safety and engraftment of human parthenogenetic stem cell-derived neural stem cells (hpNSCs) in two animal models: 6-hydroxydopamine (6-OHDA)-lesioned rodents and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated nonhuman primates (NHPs). In both rodents and nonhuman primates, we observed successful engraftment and higher dopamine levels in hpNSC-transplanted animals compared to vehicle control animals, without any adverse events. These results indicate that hpNSCs are safe, well tolerated, and could potentially be a source for cell-based therapies in PD.

Treatment for neurological diseases or trauma remains the last frontier in modern medicine because there is no effective way to repair the central nervous system (CNS) and restore function. In this chapter, we discuss neural stem cells (NSCs) as an important research tool and potential therapy. The chapter begins with a quick review of the derivation of NSCs from the CNS and human pluripotent stem cells. The chapter then progresses to review some of the NSC transplantation work that has been performed in various preclinical animal models of disease and trauma, including stroke, Parkinson disease, amyotrophic lateral sclerosis, and spinal cord injury. We conclude the chapter with a discussion on the future applications of regenerative medicine in psychiatric diseases.

To use bioluminescent imaging in a murine transplant model to monitor the in vivo responses of transplanted luciferase-gene-positive neural progenitor cells (NPCs) to host immunity and ischemia.All animal studies were conducted according to institutional guidelines, with approval of the Subcommittee on Research Animal Care. Cranial windows were created in all animals, and all animals underwent NPC (C17.2-Luc-GFP-gal) transplantation into the right basal ganglia. An observational study was performed on C57 BL/6 (n = 5), nude (n = 4), and CD-1 (n = 4) mice, with bioluminescent imaging performed at days 7, 11, and 14 after transplantation. A study on the effects of ischemia was performed in a similar manner, but with the following differences: On day 9 after transplantation, the C57 BL/6 mice underwent 18 minutes of transient forebrain ischemia by means of temporary bilateral carotid occlusions (n = 6). A control group of C57 BL/6 mice underwent sham surgery (n = 6). Bioluminescent imaging was performed on the ischemic animals and control animals at days 7, 9, 11, and 14. Repeated-measures analysis of variance or Student t test was used to compare the means of the luciferase activities.In vivo cell tracking demonstrated that (a) C17.2-Luc-GFP-gal NPCs survived and proliferated better in the T-cell deficient nude mice than in the immunocompetent C57 BL/6 or CD-1 mice, in which progressive immune mediated cell loss was shown, and (b) transient forebrain ischemia appeared, unexpectedly, to act as a short-term stimulus to transplanted NPC growth and survival in immunocompetent mice.Immune status and host immunity can have an influence on NPC graft survival, and these changes can be noninvasively assessed with bioluminescent imaging in this experimental model.

Advances in the understanding of stem cells have enabled the development of novel therapies for brain tumours. Neural stem cells (NSCs) possess the ability to migrate throughout the CNS. By exploiting the tropism of NSCs to various neural pathologies (e.g., glioma, degeneration, stroke and so on) and the delivery of various immunomodulatory cytokines, new treatments for brain tumours have been investigated. These new strategies offer significantly more specificity than existing treatment regimens, such as surgery, radiation and chemotherapy. As methods in isolating and culturing NSCs are better understood, clinical applications of this therapeutic strategy may inevitably emerge. Here, the preclinical advances and the results supporting the effectiveness of stem cell therapies are reviewed. In addition, the obstacles to clinical development and methods to circumvent these caveats are discussed.

We tested a "standard" cryopreservation protocol (slow cooling with 10% DMSO) on the human embryonic stem cell (hESC) line H9 containing an Oct-4 (POU5F1) promoter-driven, enhanced green fluorescent protein (EGFP) reporter to monitor maintenance of pluripotency. Cells were cooled to -80 degrees C in cryovials and then transferred to a -80 degrees C freezer. Cells were held at -80 degrees C for 3 days ("short-term storage") or 3 months ("long-term storage"). Vials were thawed in a +36 degrees C water bath and cells were cultured for 3, 7, or 14 days. Propidium iodide (PI) was used to assess cell viability by flow cytometry. Control cells were passaged on the same day that the frozen cells were thawed. The majority of cells in control hESC cultures were Oct-4 positive and almost 99% of EGFP+ cells were alive as determined by exclusion of PI. In contrast, the frozen cells, even after 3 days of culture, contained only 50% live cells, and only 10% were EGFP-positive. After 7 days in culture, the proportion of dead cells decreased and there was an increase in the Oct-4-positive population but microscopic examination revealed large patches of EGFP-negative cells within clusters of colonies even after 14 days of culturing. After 3 months of storage at -80 degrees C the deleterious effect of freezing was even more pronounced: the samples regained a quantifiable number of EGFP-positive cells only after 7 days of culturing following thawing. It is concluded that new protocols and media are required for freezing hESC and safe storage at -80 degrees C as well as studies of the mechanisms of stress-related events associated with cell cryopreservation.

For more than a decade the 'neurosphere assay' has been used to define and measure neural stem cell (NSC) behavior, with similar assays now used in other organ systems and in cancer. We asked whether neurospheres are clonal structures whose diameter, number and composition accurately reflect the proliferation, self-renewal and multipotency of a single founding NSC. Using time-lapse video microscopy, coculture experiments with genetically labeled cells, and analysis of the volume of spheres, we observed that neurospheres are highly motile structures prone to fuse even under ostensibly 'clonal' culture conditions. Chimeric neurospheres were prevalent independent of ages, species and neural structures. Thus, the intrinsic dynamic of neurospheres, as conventionally assayed, introduces confounders. More accurate conditions (for example, plating a single cell per miniwell) will be crucial for assessing clonality, number and fate of stem cells. These cautions probably have implications for the use of 'cytospheres' as an assay in other organ systems and with other cell types, both normal and neoplastic.

‘While such ‘small-animal’ systems offer invaluable insights into fundamental biological questions, it is often misleading and perilous to unquestionably equate the higher order motor, sensory and cognitive processes that characterize human disease with that gleaned from a mouse or rat’ Enthusiasm for therapies based on the transplantation of exogenous cells or the transfer of genes by viral vectors has burgeoned over the past 30 years, accompanied by a predictable exhortation to launch clinical trials as soon as possible. Most data regarding safety, efficacy and mechanisms of these therapies have been derived from studies in rodents alone. While such ‘small-animal’ systems offer invaluable insights into fundamental biological questions, it is often misleading and perilous to unquestionably equate the higher order motor, sensory and cognitive processes that characterize human disease with that gleaned from a mouse or rat. Indeed, the literature is littered with clinical trials that failed and, in some cases, led to unforeseen adverse outcomes because the field leap-frogged over the requisite large-animal model. Large animals often provide an essential bridge between insights into fundamental biology and pathophysiology gleaned from simple systems and the realities of treating a human disease. Often, this is especially true for neurological disorders where not only differences in size and scale pertain, but also in neuroanatomical connections and organization, cognitive capacities, signaling pathways, genetic redundancy or the disease etiology. While the gene therapy field has increased their use of nonhuman primates prior to the application of viral vectors in clinical trials, the cellular therapy field – represented most conspicuously of late by the stem cell field – has only recently begun to properly address this requirement. Monkeys and the minipig may prove to be excellent preclinical models owing to their similar comparative anatomy, pharmacokinetics and physiological and metabolic

Previously, we reported that, when clonal neural stem cells (NSCs) were transplanted into brains of postnatal mice subjected to unilateral hypoxic-ischemic (HI) injury (optimally 3-7 days following infarction), donor-derived cells homed preferentially (from even distant locations) to and integrated extensively within the large ischemic areas that spanned the hemisphere. A subpopulation of NSCs and host cells, particularly in the penumbra, "shifted" their differentiation towards neurons and oligodendrocytes, the cell types typically damaged following asphyxia and least likely to regenerate spontaneously and in sufficient quantity in the "post-developmental" CNS. That no neurons and few oligodendrocytes were generated from the NSCs in intact postnatal cortex suggested that novel signals are transiently elaborated following HI to which NSCs might respond. The proportion of "replacement" neurons was approximately 5%. Neurotrophin-3 (NT-3) is known to play a role in inducing neuronal differentiation during development and perhaps following injury. We demonstrated that NSCs express functional TrkC receptors. Furthermore, the donor cells continued to express a foreign reporter transgene robustly within the damaged brain. Therefore, it appeared feasible that neuronal differentiation of exogenous NSCs (as well as endogenous progenitors) might be enhanced if donor NSCs were engineered prior to transplantation to (over)express a bioactive gene such as NT-3. A subclone of NSCs transduced with a retrovirus encoding NT-3 (yielding90% neurons in vitro) was implanted into unilaterally asphyxiated postnatal day 7 mouse brain (emulating one of the common causes of cerebral palsy). The subclone expressed NT-3 efficiently in vivo. The proportion of NSC-derived neurons increased to approximately 20% in the infarction cavity and80% in the penumbra. The neurons variously differentiated further into cholinergic, GABAergic, or glutamatergic subtypes, appropriate to the cortex. Donor-derived glia were rare, and astroglial scarring was blunted. NT-3 likely functioned not only on donor cells in an autocrine/paracrine fashion but also on host cells to enhance neuronal differentiation of both. Taken together, these observations suggest (1) the feasibility of taking a fundamental biological response to injury and augmenting it for repair purposes and (2) the potential use of migratory NSCs in some degenerative conditions for simultaneous combined gene therapy and cell replacement during the same procedure in the same recipient using the same cell (a unique property of cells with stem-like attributes).

Clonal neural cells with stem-like features integrate appropriately into the developing and degenerating central and peripheral nervous system throughout the neuraxis. In response to hypoxic-ischemic (HI) injury, previously engrafted, integrated, and quiescent clonal neural stem cells (NSCs) transiently re-enter the cell cycle, migrate preferentially to the site of ischemia, and differentiate into neurons and oligodendrocytes, the neural cell types typically lost following HI brain injury. They also replenish the supply of immature uncommitted resident stem/progenitor cells. Although they yield astrocytes, scarring is inhibited. These responses appear to occur most robustly within a 3-7 day "window" following HI during which signals are elaborated that upregulate genetic programs within the NSC that mediate proliferation, migration, survival, and differentiation, most of which appear to be terminated once the "window closes" and the chronic phase ensues, sending the NSCs into a quiescent state. These insights derived from using the stem cell in a novel role--as a "reporter" cell--to both track and probe the activity of endogenous stem cells as well as to "interrogate" and "report" the genes differentially induced by the acutely vs. chronically injured milieu. NSCs may be capable of the replacement of cells, genes, and non-diffusible factors in both a widespread or more circumscribed manner (depending on the therapeutic demands of the clinical situation). They may be uniquely responsive to some types of neurodegenerative conditions. We submit that these various capabilities are simply the normal expression of the basic homeostasis-preserving biologic properties and attributes of a stem cell which, if used rationally and in concert with this biology, may be exploited for therapeutic ends.