oa Editorial [Hot Topic:Role of Neural Stem Cells in Neurodegenerative Diseases:From the Molecule and Cell to the Clinic (Guest Editor: Oscar Gonzalez-Perez)]

Neurological disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease, stroke and multiple sclerosis (MS) are caused by an extensive loss of neurons and glial cells into the brain. Regrettably, there are no effective treatments against any of these disorders, yet. Recently, cell replacement and gene transfer into the damaged brain have shown a high potential for the design of novel therapeutic strategies to treat a broad spectrum of human neurological diseases. This special issue is a timely compilation of comprehensive and concise reviews, which summarize the most important experimental and preclinical studies involving stem-cell-based and gene therapies against neurodegenerative diseases. All contributors are experts in specific fields and all of them discuss the benefits and potential pitfalls of stem-cell-based therapies in several neurological disorders. Because they were written using a simple language, these peer-reviewed contributions are suitable for novices and experts readers. This issue begins with a concise review that provides basic concepts and describes the cellular composition of the subventricular zone, the main niche of the neural stem cells in the adult brain. Additionally, this review also describes the signals involved in proliferation, survival, migration and differentiation of neural stem cells under physiological conditions. In an excellent review, Kasahara et al. explain the role of stem cells and the cell signals involved in the brain repair after stroke. As elegantly discussed by Kabatas and colleagues, these beneficial properties of stem cells are not exclusive for cerebral ischemia, but also appear to be useful in traumatic injuries. Increasing evidence indicates that stem cells play an important role in sustained tissue restoration and cellular homeostasis into the brain. This is a crucial property for the design of therapies against chronic neurodegenerative processes. In a landmark review, Rivera et al. comprehensively explain the cell signals that control mesenchymal and neural stem cells in myelination and remyelination of injured white matter. On the other hand, Mitrecic et al. nicely explicate recent data found against amyotrophic lateral sclerosis. Millan and Gonzalez-Castaneda conclude this special issue explaining the novel advances reached in stem-cell-based therapies in models of Parkinson's and Alzheimer's disease, respectively. In summary, growing evidence indicates that mesenchymal and neural stem cells are good candidates to establish stem cellbased therapies in neural disorders. Mature neurons and oligodendrocytes are efficiently generated from these multipotent cells. In parallel, extensive efforts to develop stem-cell transplantations have been successfully performed under experimental conditions. Nevertheless chemical mediators and signaling pathways involved in all these processes are to be fully elucidated, before these stem-cell-based therapies become a realistic clinical tool against neurodegenerative diseases.