![]() ![]() Stem cells are also regulated by intrinsic signaling cascades and transcriptional mechanisms, some of which are common among all stem cells, and others that are unique to specific types. The behavior and fate of stem cells are strongly influenced by their specific anatomical locations and surrounding cell types, called “ the stem cell niche.” The niche provides physical support to host or anchor stem cells, and supplies factors to maintain and regulate them ( Li and Zhao, 2008). The latter definition has evolved into the modern definition of stem cells - cells that can divide to self-renew and to differentiate into other cell types in tissues and organs ( Li and Zhao, 2008, Ramalho-Santos and Willenbring, 2007). In his writings ( Haeckel, 1868), “stem cells” had two distinct meanings: one is the unicellular evolutionary origin of all multicellular organisms, and the other is the fertilized egg giving rise to all other cell types of the body. The term “stem cells” first appeared in the scientific literature in 1868 by the German biologist Ernst Haeckel ( Haeckel, 1868). In this special issue, leaders and experts in NSCs summarize our current understanding of NSC molecular regulation and the importance of NSCs for disease modeling and translational applications. Although recent advancements in embryonic and induced pluripotent stem cells have provided novel sources for NSCs, several challenges remain. The limited number of NSCs residing in the tissue has been a limiting factor for their clinical applications. On the other hand, ever since their discovery, NSCs have been a focal point for cell-based therapeutic strategies in the brain and spinal cord. Therefore, extensive investigations in the past decades have been devoted to understanding how NSCs are regulated. Because NSCs are regulated by both intrinsic genetic and epigenetic programs and extrinsic stimuli transduced through the stem cell niche, dysregulation of NSCs due to either genetic causes or environmental impacts may lead to disease. In adults, a small number of NSCs remain and are mostly quiescent however, ample evidence supports their important roles in plasticity, aging, disease, and regeneration of the nervous system. During development they give rise to the entire nervous system. Neural stem cells (NSCs) are the stem cells of the nervous system. The astonishing progress in the field of stem cell biology during the past 40 years has transformed both science and medicine. ![]()
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