Segregation of Human Neural Stem Cells in the Developing Primate Forebrain

Many central nervous system regions at all stages of life contain neural stem cells (NSCs). We explored how these disparate NSC pools might emerge. A traceable clone of human NSCs was implanted intraventricularly to allow its integration into cerebral germinal zones of Old World monkey fetuses. The NSCs distributed into two subpopulations: One contributed to corticogenesis by migrating along radial glia to temporally appropriate layers of the cortical plate and differentiating into lamina-appropriate neurons or glia; the other remained undifferentiated and contributed to a secondary germinal zone (the subventricular zone) with occasional members interspersed throughout brain parenchyma. An early neurogenetic program allocates the progeny of NSCs either immediately for organogenesis or to undifferentiated pools for later use in the “postdevelopmental” brain.ope

Clinical applications of human neural stem cells in neurodegenerative diseases, especially neonatal hypoxic-ischemic brain injury and spinal cord injury

Multipotent neural stem cells (NSCs) are operationally defined by their ability to self-renew, to differentiate into cells of all glial and neuronal lineages throughout the neuraxis, and to populate developing or degenerating CNS regions. The recognition that NSCs that were propagated in culture could be reimplanted into the mammalian brain, where they might integrate appropriately throughout the mammalian CNS and stably express foreign genes, has unveiled a new role for neural transplantation and gene therapy and a possible strategy for addressing the CNS manifestations of diseases that heretofore had been refractory to intervention. Proliferating single cells were isolated from the telencephalic region of human fetal cadavers at 13 weeks of gestation and were grown as neurospheres in long-term cultures. We investigated the characteristics of the growth, differentiation, and region-specific gene expression of human NSCs. An intriguing phenomenon with possible therapeutic potentials has begun to emerge from our observations of the behavior of NSCs in animal models of neonatal hypoxic-ischemic brain and spinal cord injury. During phases of active neurodegeneration, factors seem to be transiently elaborated to which NSCs may respond by migrating to degenerating regions and differentiating specifically towards replacement of dying neural cells. NSCs may attempt to repopulate and reconstitute ablated regions. In addition, NSCs may serve as vehicles for gene delivery and appear capable of simultaneous neural cell replacement and gene therapy. After the approval of the Institutional Review Board of Severance Hospital, Yonsei University College of Medicine and Korean Food and Drug Administration, an investigator-sponsored clinical trial of the transplantation of human NSCs into patients with severe perinatal hypoxic ischemic brain injury and traumatic cervical motor complete spinal cord injury have been performed. The existing data from these clinical trials have shown to be safe, well tolerated, and of neurologically-some benefits.ope

Global gene and cell replacement strategies via stem cells

The inherent biology of neural stem cells (NSCs) endows them with capabilities that not only circumvent many of the limitations of other gene transfer vehicles, but that enable a variety of novel therapeutic strategies heretofore regarded as beyond the purview of neural transplantation. Most neurodegenerative diseases are characterized not by discrete, focal abnormalities but rather by extensive, multifocal, or even global neuropathology. Such widely disseminated lesions have not conventionally been regarded as amenable to neural transplantation. However, the ability of NSCs to engraft diffusely and become integral members of structures throughout the host CNS, while also expressing therapeutic molecules, may permit these cells to address that challenge. Intriguingly, while NSCs can be readily engineered to express specified foreign genes, other intrinsic factors appear to emanate spontaneously from NSCs and, in the context of reciprocal donor-host signaling, seem to be capable of neuroprotective and/or neuroregenerative functions. Stem cells additionally have the appealing ability to 'home in' on pathology, even over great distances. Such observations help to advance the idea that NSCs - as a prototype for stem cells from other solid organs - might aid in reconstructing the molecular and cellular milieu of maldeveloped or damaged organs.ope

Stem cells: cross-talk and developmental programs

The thesis advanced in this essay is that stem cells-particularly those in the nervous system-are components in a series of inborn 'programs' that not only ensure normal development, but persist throughout life so as to maintain homeostasis in the face of perturbations-both small and great. These programs encode what has come to be called 'plasticity'. The stem cell is one of the repositories of this plasticity. This review examines the evidence that interaction between the neural stem cell (as a prototypical somatic stem cell) and the developing or injured brain is a dynamic, complex, ongoing reciprocal set of interactions where both entities are constantly in flux. We suggest that this interaction can be viewed almost from a 'systems biology' vantage point. We further advance the notion that clones of exogenous stem cells in transplantation paradigms may not only be viewed for their therapeutic potential, but also as biological tools for 'interrogating' the normal or abnormal central nervous system environment, indicating what salient cues (among the many present) are actually guiding the expression of these 'programs'; in other words, using the stem cell as a 'reporter cell'. Based on this type of analysis, we suggest some of the relevant molecular pathways responsible for this 'cross-talk' which, in turn, lead to proliferation, migration, cell genesis, trophic support, protection, guidance, detoxification, rescue, etc. This type of developmental insight, we propose, is required for the development of therapeutic strategies for neurodegenerative disease and other nervous system afflictions in humans. Understanding the relevant molecular pathways of stem cell repair phenotype should be a priority, in our view, for the entire stem cell field.ope

The dynamics of long-term transgene expression in engrafted neural stem cells

To assess the dynamics and confounding variables that influence transgene expression in neural stem cells (NSCs), we generated distinct NSC clones from the same pool of cells, carrying the same reporter gene transcribed from the same promoter, transduced by the same retroviral vector, and transplanted similarly at the same differentiation state, at the same time and location, into the brains of newborn mouse littermates, and monitored in parallel for over a year in vivo (without immunosuppression). Therefore, the sole variables were transgene chromosomal insertion site and copy number. We then adapted and optimized a technique that tests, at the single cell level, persistence of stem cell-mediated transgene expression in vivo based on correlating the presence of the transgene in a given NSC's nucleus (by fluorescence in situ hybridization [FISH]) with the frequency of that transgene's product within the same cell (by combined immunohistochemistry [IHC]). Under the above-stated conditions, insertion site is likely the most contributory variable dictating transgene downregulation in an NSC after 3 months in vivo. We also observed that this obstacle could be effectively and safely counteracted by simple serial infections (as few as three) inserting redundant copies of the transgene into the prospective donor NSC. (The preservation of normal growth control mechanisms and an absence of tumorigenic potential can be readily screened and ensured ex vivo prior to transplantation.) The combined FISH/IHC strategy employed here for monitoring the dynamics of transgene expression at the single cell level in vivo may be used for other types of therapeutic and housekeeping genes in endogenous and exogenous stem cells of many organs and lineagesope

Directed migration of neural stem cells to sites of CNS injury by the stromal cell-derived factor 1 alpha/CXC chemokine receptor 4 pathway

Migration toward pathology is the first critical step in stem cell engagement during regeneration. Neural stem cells (NSCs) migrate through the parenchyma along nonstereotypical routes in a precise directed manner across great distances to injury sites in the CNS, where they might engage niches harboring local transiently expressed reparative signals. The molecular mechanisms for NSC mobilization have not been identified. Because NSCs seem to home similarly to pathologic sites derived from disparate etiologies, we hypothesized that the inflammatory response itself, a characteristic common to all, guides the behavior of potentially reparative cells. As proof of concept, we show that human NSCs migrate in vivo (including from the contralateral hemisphere) toward an infarcted area (a representative CNS injury), where local astrocytes and endothelium up-regulate the inflammatory chemoattractant stromal cell-derived factor 1α (SDF-1α). NSCs express CXC chemokine receptor 4 (CXCR4), the cognate receptor for SDF-1α. Exposure of SDF-1α to quiescent NSCs enhances proliferation, promotes chain migration and transmigration, and activates intracellular molecular pathways mediating engagement. CXCR4 blockade abrogates their pathology-directed chain migration, a developmentally relevant mode of tangential migration that, if recapitulated, could explain homing along nonstereotypical paths. Our data implicate SDF-1α/CXCR4, representative of the inflammatory milieu characterizing many pathologies, as a pathway that activates NSC molecular programs during injury and suggest that inflammation may be viewed not simply as playing an adverse role but also as providing stimuli that recruit cells with a regenerative homeostasis-promoting capacity. CXCR4 expression within germinal zones suggests that NSC homing after injury and migration during development may invoke similar mechanisms.ope

The Promotion of Human Neural Stem Cells Adhesion Using Bioinspired Poly(norepinephrine) Nanoscale Coating

The establishment of versatile biomaterial interfaces that can facilitate cellular adhesion is crucial for elucidating the cellular processes that occur on biomaterial surfaces. Furthermore, biomaterial interfaces can provide physical or chemical cues that are capable of stimulating cellular behaviors by regulating intracellular signaling cascades. Herein, a method of creating a biomimetic functional biointerface was introduced to enhance human neural stem cell (hNSC) adhesion. The hNSC-compatible biointerface was prepared by the oxidative polymerization of the neurotransmitter norepinephrine, which generates a nanoscale organic thin layer, termed poly(norepinephrine) (pNE). Due to its adhesive property, pNE resulted in an adherent layer on various substrates, and pNE-coated biointerfaces provided a highly favorable microenvironment for hNSCs, with no observed cytotoxicity. Only a 2-hour incubation of hNSCs was required to firmly attach the stem cells, regardless of the type of substrate. Importantly, the adhesive properties of pNE interfaces led to micropatterns of cellular attachment, thereby demonstrating the ability of the interface to organize the stem cells. This highly facile surface-modification method using a biomimetic pNE thin layer can be applied to a number of suitable materials that were previously not compatible with hNSC technology.ope

Human Neural Stem Cells: Translational Research for Neonatal Hypoxic-Ischemic Brain Injury

Neonatal hypoxic-ischemic (HI) brain injury is a major cause of neonatal mortality and long-term neurodevelopmental disabilities. Although promising neuroprotective interventions have been studied, the current management of HI brain injury has been limited to supportive measures and induced hypothermia. In addition to engrafting, migrating toward the damage sites and differentiating into multiple lineages, multipotent neural stem/progenitor cells (NSPCs) also provide trophic/immunomodulatory factors and integrate into the host neurons upon implantation into an HI-injured brain. However, NSPC-based therapies have shown poor cell survival and integration, poor differentiation or restricted differentiation into the glial lineages. Furthermore, to achieve full functional recovery following brain injury, the optimization of cell therapy is needed to recapitulate the precise migration of stem cells to the region of interest and the neural rewiring present in the brain microenvironment. Therefore, the efficacy of NSPCs in the treatment of CNS injury is currently insufficient. Human NSPCs (hNSPCs) were isolated from the forebrain of an aborted fetus at 13 weeks of gestation with full parental consent and the approval of the Institutional Review Board of the Yonsei University College of Medicine. Here, to enhance the regenerative ability of hNSPCs in HI brain injury, cells were either pretreated with pharmacological agents or engineered to serve as vehicles for gene delivery. Furthermore, when combined with a poly (glycolic acid)-based synthetic scaffold, hNSPCs provide a more versatile treatment for neonatal HI brain injury. Finally, hNSPCs transfected with zinc-doped ferrite magnetic nanoparticles for controlling both cell migration and differentiation offer a simple and smart tool for cell-based therapies.ope

An evolved adeno-associated viral variant enhances gene delivery and gene targeting in neural stem cells

Gene delivery to, and gene targeting in, stem cells would be a highly enabling technology for basic science and biomedical application. Adeno-associated viral (AAV) vectors have demonstrated the capacity for efficient delivery to numerous cells, but their application to stem cells has been limited by low transduction efficiency. Due to their considerable advantages, however, engineering AAV delivery systems to enhance gene delivery to stem cells may have an impact in stem cell biology and therapy. Therefore, using several diverse AAV capsid libraries-including randomly mutagenized, DNA shuffled, and random peptide insertion variants-we applied directed evolution to create a "designer" AAV vector with enhanced delivery efficiency for neural stem cells (NSCs). A novel AAV variant, carrying an insertion of a selected peptide sequence on the surface of the threefold spike within the heparin-binding site, emerged from this evolution. Importantly, this evolved AAV variant mediated efficient gene delivery to rat, mouse, and human NSCs, as well as efficient gene targeting within adult NSCs, and it is thus promising for applications ranging from basic stem cell biology to clinical translation.ope

Successful Treatment of Neonatal Pylorospasm with Intravenous Atropine

Pylorospasm is a cause of delayed gastric emptying in young infants. As in patients with hypertrophic pyloric stenosis, most pylorospasm patients present with projectile vomiting. However, unlike that in case of hypertrophic pyloric stenosis, no persistent pyloric stenotic lesions are present. As such, follow-up using serial gastrointestinal fluoroscopy or ultrasonography can be helpful in diagnosing patients with clinical signs of gastroparesis. Most cases can be treated conservatively, but some patients require pharmacologic treatment. Antispasmodics have been proposed as a treatment for pylorospasm, but their use in neonates and infants has rarely been reported. Herein, we present a case of pylorospasm diagnosed in the neonatal period and successfully treated with intravenous atropine.ope