A Bivalent Chromatin Structure Marks Key Developmental Genes in Embryonic Stem Cells

Neural stem cells exist not only in the developing mammalian nervous system but also in the adult nervous system of all mammalian organisms, including humans. Neural stem cells can also be derived from more primitive embryonic stem cells. The location of the adult stem cells and the brain regions to which their progeny migrate in order to differentiate remain unresolved, although the number of viable locations is limited in the adult. The mechanisms that regulate endogenous stem cells are poorly understood. Potential uses of stem cells in repair include transplantation to repair missing cells and the activation of endogenous cells to provide "self-repair. " Before the full potential of neural stem cells can be realized, we need to learn what controls their proliferation, as well as the various pathways of differentiation available to their daughter cells.

https://science.sciencemag.org/content/sci/287/5457/1433.full.pdf

Mammalian neural stem cells.

The remarkable developmental potential and replicative capacity of human embryonic stem (ES) cells promise an almost unlimited supply of specific cell types for transplantation therapies. Here we describe the in vitro differentiation, enrichment, and transplantation of neural precursor cells from human ES cells. Upon aggregation to embryoid bodies, differentiating ES cells formed large numbers of neural tube-like structures in the presence of fibroblast growth factor 2 (FGF-2). Neural precursors within these formations were isolated by selective enzymatic digestion and further purified on the basis of differential adhesion. Following withdrawal of FGF-2, they differentiated into neurons, astrocytes, and oligodendrocytes. After transplantation into the neonatal mouse brain, human ES cell-derived neural precursors were incorporated into a variety of brain regions, where they differentiated into both neurons and astrocytes. No teratoma formation was observed in the transplant recipients. These results depict human ES cells as a source of transplantable neural precursors for possible nervous system repair.

http://digital.library.ucla.edu/websites/2004_996_027/ntp.neuroscience.wisc.edu/faculty/fac-art/zhangb.pdf

In vitro differentiation of transplantable neural precursors from human embryonic stem cells

Stem cells, which are clonogenic cells with self-renewal and multilineage differentiation properties, have the potential to replace or repair damaged tissue. We have directly isolated clonogenic human central nervous system stem cells (hCNS-SC) from fresh human fetal brain tissue, using antibodies to cell surface markers and fluorescence-activated cell sorting. These hCNS-SC are phenotypically 5F3 (CD133)+, 5E12+, CD34−, CD45−, and CD24−/lo. Single CD133+ CD34− CD45− sorted cells initiated neurosphere cultures, and the progeny of clonogenic cells could differentiate into both neurons and glial cells. Single cells from neurosphere cultures initiated from CD133+ CD34− CD45− cells were again replated as single cells and were able to reestablish neurosphere cultures, demonstrating the self-renewal potential of this highly enriched population. Upon transplantation into brains of immunodeficient neonatal mice, the sorted/expanded hCNS-SC showed potent engraftment, proliferation, migration, and neural differentiation.

https://www.pnas.org/content/pnas/97/26/14720.full.pdf

Direct isolation of human central nervous system stem cells

We describe here the isolation of stem cells from juvenile and adult rodent skin. These cells derive from the dermis, and clones of individual cells can proliferate and differentiate in culture to produce neurons, glia, smooth muscle cells and adipocytes. Similar precursors that produce neuron-specific proteins upon differentiation can be isolated from adult human scalp. Because these cells (termed SKPs for skin-derived precursors) generate both neural and mesodermal progeny, we propose that they represent a novel multipotent adult stem cell and suggest that skin may provide an accessible, autologous source of stem cells for transplantation.

/pdf/isolation-of-multipotent-adult-stem-cells-from-the-dermis-of-2ysrudtkph.pdf

Isolation of multipotent adult stem cells from the dermis of mammalian skin

Self-renewing, totipotent embryonic stem (ES) cells may provide a virtually unlimited donor source for transplantation. A protocol that permits the in vitro generation of precursors for oligodendrocytes and astrocytes from ES cells was devised. Transplantation in a rat model of a human myelin disease shows that these ES cell-derived precursors interact with host neurons and efficiently myelinate axons in brain and spinal cord. Thus, ES cells can serve as a valuable source of cell type-specific somatic precursors for neural transplantation.

https://science.sciencemag.org/content/sci/285/5428/754.full.pdf

Embryonic Stem Cell-Derived Glial Precursors: A Source of Myelinating Transplants

Transplantation of myelin-forming cells is a promising strategy for the treatment of myelin disorders. In this study, transplantation of glial cell progenitors into the cerebral ventricles of the embryonic myelin-deficient rat, a model of Pelizaeus-Merzbacher disease, was performed to assess the ability of these cells to incorporate into the developing brain and produce myelin. The donor cells migrated into the white and gray matter and produced myelin at widespread sites ranging from the corpus callosum and optic nerve to the cerebellum. These data suggest that myelin repair might be achieved by intraventricular delivery and transependymal incorporation of myelin-producing cells. Because these cells were genetically transduced to express a reporter gene, similar ex vivo manipulation with genes known to promote survival, migration, or proliferation of the transplanted cells could be used to enhance repair. Such a therapeutic strategy may be feasible in patients with inherited myelin disorders or in multiple sclerosis, particularly where the lesions are periventricular.

Randall D. Learish

Papers

Embryonic Stem Cell-Derived Glial Precursors: A Source of Myelinating Transplants

Intraventricular transplantation of oligodendrocyte progenitors into a fetal myelin mutant results in widespread formation of myelin.