Neural Stem Cell Research Research Articles

Neural stem cells and the quest for restorative neurology.

A great deal of interest has attracted the attention of researchers on the potential use of (neural) stem cells in cell replacement or restorative therapies for heretofore incurable CNS pathologies such as brain stroke, spinal cord injury, Parkinson's disease or multiple sclerosis. This short perspective illustrates our view of neural stem cell research with a focus on the stem cell concept, on the in situ identity of neural stem cells and on selected aspects of embryonic and adult neurogenesis. A brief survey of current stem cell-based experimental literature tries to provide a realistic picture of how far we have gone in the quest to establish a restorative neurology.

Adult neural stem cells and repair of the adult central nervous system.

Neural stem cells are present not only in the developing nervous systems, but also in the adult central nervous system of mammals, including humans. The mature central nervous system has been traditionally regarded as an unfavorable environment for the regeneration of damaged axons of mature neurons and the generation of new neurons. In the adult central nervous system, however, newly generated neurons from adult neural stem cells in specific regions exhibit a striking ability to migrate, send out long axonal and dendritic projections, integrate into pre-existing neuronal circuits, and contribute to normal brain functions. Adult stem cells with potential neural capacity recently have been isolated from various neural and nonneural sources. Rapid advances in the stem cell biology have raised exciting possibilities of replacing damaged or lost neurons by activation of endogenous neural stem cells and/or transplantation of in vitro-expanded stem cells and/or their neuronal progeny. Before the full potential of adult stem cells can be realized for regenerative medicine, we need to identify the sources of stem cells, to understand mechanisms regulating their proliferation, fate specification, and, most importantly in the case of neuronal lineages, to characterize their functional properties. Equally important, we need to understand the neural development processes in the normal and diseased adult central nervous system environment, which is quite different from the embryonic central nervous system, where neural development has been traditionally investigated. Here we will review some recent progress of adult neural stem cell research that is applicable to developmental neurobiology and also has potential implications in clinical neuroscience.

Where new neurons come from

The brain has come alive with the sightings of stem cells, but the molecular handles on those cells are few. On page 169, Belachew et al. identify and characterize a new population of neural stem cells (NSCs) that can generate neurons in the postnatal mouse brain. Figure Putative neural stem cells expressing both CNP-GFP (green) and NG2 (red) are present in the adult CNS. In previous work, the researchers identified cells that express CNP in transgenic mice using a CNP-GFP marker. CNP is made in immature oligodendrocytes, so it is not surprising that the GFP-positive cells also express the proteoglycan NG2, which is also found in oligodendrocytes. But NG2+ cells are also present in parts of the CNS that contain NSCs, and are the major cell type that continues to divide in the adult CNS. The significance of these facts has remained unclear, as the function of NG2 in cell types other than oligodendrocytes had never been investigated. Now, Belachew et al. have cultured the CNP-GFP+/NG2+ cells, and found that the cells quickly turn into a variety of neural cell types, including astrocytes, oligodendrocytes, and electrically active neurons. When examined in their natural context, CNP-GFP+/NG2+ cells are highly proliferative and give rise to a variety of cell types in different parts of the brain. In the hippocampus, one place where neurons are born through adulthood, the CNP-GFP+/NG2+ cells turn into neurons. In contrast to previously identified GFAP+ NSCs, which are thought to give rise to excitatory neurons, CNP-GFP+/NG2+ cells give rise to inhibitory neurons. So there may be several types of stem cells in the brain, generating distinct subsets of adult-born neurons. A large hindrance to NSC research has been the lack of markers for stem cells. Use of the CNP and NG2 markers will allow researchers to explore the full repertoire of these stem cells and to test ways to manipulate their behavior. If the cells can be coaxed into migrating to the right places and stimulated to proliferate and differentiate, they might eventually be used to repair a damaged CNS. ▪

Transgenic and knock-out mice for deciphering the roles of EGFR ligands.

Generation of genetically engineered mice with either gain-of-function or loss-of-function mutations is the most popular technique for determining gene functions and the interrelationship between molecules in vivo. These models have provided a wealth of information about the developmental and physiological roles of oncogenes and growth factors. To date, transgenic techniques have been used extensively to study the functions of the epidermal growth factor (EGF) family. This review highlights some of the major recent findings pertinent to the EGF receptor (EGFR) and its ligands with special reference to elucidating how EGF and its related growth factors work together to regulate reproduction, growth and development. Finally, future investigations on ligand-ligand communications, EGFR and its ligands in neural stem cell research, and the mechanisms of EGFR signaling and trafficking in cells are also suggested.

Gene Therapy with Virus Vectors for specific Disease of the Nervous System: Adeno-Associated Viral Vectors For Parkinson's Disease

This chapter presents recombinant adeno-associated viral (rAAV) vector that represents one of the most powerful vehicles for delivering therapeutic genes into mammalian brains. In rodents and nonhuman primates, a substantial number of striatal neurons can be transduced with high titer rAAV vectors through simple stereotaxic injection. Although chromosomal rearrangements in association with integration of rAAV have been indicated in a transformed cell line, the safety and potential efficacy of rAAV vectors have been demonstrated both in animal models of several diseases and in clinical trials on patients with hemophilia. Recent advances in the field of neural or embryonic stem cell research have raised the hope of cell replacement as an alternative therapy for Parkinson's disease (PD). The significant functional recovery achieved with the triple transduction method in the primate model provides an optimistic outlook for gene therapy treatment of PD. Gene therapy using rAAV vectors is now not merely an experimental strategy, but offers a novel and apparently feasible protocol for the treatment of PD.

When cells become depressed: focus on neural stem cells in novel treatment strategies against depression.

Clinical neuroscience enters a new era in understanding the pathophysiology of depressive illness and the mode of action of antidepressant therapy. While elucidation of factors that lead to depression is still in its infancy, biochemical malfunctions appear to have well defined morphological correlations, especially in the hippocampus. Hippocampus is one of the main sites in the brain habouring neural stem cells. Cytokines and neurotrophic factors like brain-derived neurotrophic factor (BDNF) play a pivotal role in neural plasticity and potentially influence growth and migration of these progenitors. Not surprisingly, antidepressant drugs interfering with neurotransmitters such as serotonin (5-HT) influence neurotrophins like BDNF, since 5-HT homeostasis is essential for brain development, neurogenesis, and neuroplasticity as well as complex behavior. In this review, the new area of neural stem cell research and the avenues of ongoing and future research sustaining the development of novel treatments for depression will be explored.

Characterization of neurosphere cell phenotypes by flow cytometry

Neural stem cell research regularly utilizes neurosphere cultures as a continuous source of primitive neural cells. Results from current progenitor cell assays show that these cultures contain a low number of neural progenitors. Our goal is to characterize neurosphere cultures and define subpopulations in order to purify neural progenitor cells. Cells from embryonic mouse neurosphere cultures were stained with Hoechst 33342 and analyzed by flow cytometry. Subpopulations were sorted based on their relative fluorescence intensity in the blue and red regions of the spectrum. Individual sorted subpopulations were reanalyzed after 7 days in culture. Neurosphere cultures contain a relatively high number of cells that stain weakly with Hoechst 33342. This subpopulation is present when cultured as an entire batch in the presence of epidermal growth factor (EGF). When cultured separately, this subpopulation gives rise to a neurosphere population with essentially the same characteristics as freshly isolated embryonic mouse brain cells but contains substantially fewer weakly Hoechst-stained cells. Similar to hemopoietic systems, neurosphere cultures contain a subpopulation that can be characterized by a low emission of Hoechst fluorescence. When cultured separately, this subpopulation gives rise to a phenotype similar to freshly isolated, uncultured neural cells.