The change of the neuron–glia differentiation rate in human neural precursor cells (HPCs) and Ad-BDNF-/-GDNF-infected HPCs following the administration of a neurotoxin

Effect of BDNF and Other Potential Survival Factors in Models of In Vitro Oxidative Stress on Adult Spinal Cord-Derived Neural Stem/Progenitor Cells

Transplantation of neural stem/progenitor cells (NSPCs) is a promising strategy in spinal cord injury (SCI). However, poor survival of transplanted stem cells remains a major limitation of this therapy due to the hostile environment of the injured cord. Oxidative stress is a hallmark in the pathogenesis of SCI; however, its effects on NSPCs from the adult spinal cord have yet to be examined. We therefore developed in vitro models of mild and severe oxidative stress of adult spinal cord-derived NSPCs and used these models to examine potential cell survival factors. NSPCs harvested from the adult rat spinal cord were treated with hydrogen peroxide (H2O2) in vitro to induce oxidative stress. A mild 4 h exposure to H2O2 (500 μM) significantly increased the level of intracellular reactive oxygen species with minimal effect on viability. In contrast, 24 h of oxidative stress led to a marked reduction in cell survival. Pretreatment with brain-derived neurotrophic factor (BDNF) for 48 h attenuated the increase in intracellular reactive oxygen species and enhanced survival. This survival effect was associated with a significant reduction in the number of apoptotic cells and a significant increase in the activity of the antioxidant enzymes glutathione reductase and superoxide dismutase. BDNF treatment had no effect on NSPC differentiation or proliferation. In contrast, cyclosporin A and thyrotropin-releasing hormone had minimal or no effect on NSPC survival. Thus, these models of in vitro oxidative stress may be useful for screening neuroprotective factors administered prior to transplantation to enhance survival of stem cell transplants.

Response of human oligodendrocyte progenitors to growth factors and axon signals

We examined the effects of growth factors and axonal signals on the differentiation of human fetal and adult oligodendrocyte progenitor cells (OPCs) and determined whether these effects translated into enhanced axonal ensheathment. Only small numbers of fetal OPCs grown in defined medium expressed the oligodendroglial lineage markers Olig2 and O4. The combination of platelet-derived growth factor-AA and basic fibroblast growth factor enhanced proliferation of Olig2-positive and O4-positive cells; a combination of brain-derived neurotrophic factor and insulin-like growth factor 1 promoted O4-positive cell differentiation, galactocerebroside expression, and morphological complexity. Coculturing with rodent dorsal root ganglion neurons in defined medium alone enhanced OPC differentiation and myelin basic protein expression. The addition of brain-derived neurotrophic factor/insulin-like growth factor 1 further enhanced differentiation, axonal attachment and ensheathment, and clustering of the contactin-associated protein Caspr and Na+ channels. By contrast, most adult OPCs were O4 positive and Olig2 positive in defined medium; both brain-derived neurotrophic factor/insulin-like growth factor 1 and platelet-derived growth factor-AA/basic fibroblast growth factor promoted their myelin basic protein expression and membrane sheet formation; coculture with dorsal root ganglion neurons further increased myelin basic protein expression. Growth factors also enhanced attachment of adult OPCs to axons, but their capacity to ensheath axons was lower than that of fetal OPCs. These results demonstrate that fetal and adult OPCs show measurable responses to selected growth factors and axon signals that correlate with their capacity for axon ensheathment. The distinct properties of fetal and adult OPCs may be related to differences in their chronological age and initial differentiation states.

Development of a high-throughput screening assay for chemical effects on proliferation and viability of immortalized human neural progenitor cells

There is considerable public concern that the majority of commercial chemicals have not been evaluated for their potential to cause developmental neurotoxicity. Although several chemicals are assessed annually under the current developmental neurotoxicity guidelines, time, resource, and animal constraints prevent testing of large numbers of chemicals using this approach. Thus, incentive is mounting to develop in vitro methods to screen chemicals for their potential to harm the developing human nervous system. As an initial step toward this end, the present studies evaluated an automated, high-throughput method for screening chemical effects on proliferation and viability using ReNcell CX cells, a human neural progenitor cell (hNPC) line. ReNcell CX cells doubled in approximately 36 h and expressed the neural progenitor markers nestin and SOX2. High-throughput assays for cell proliferation (5-bromo-2'-deoxyuridine incorporation) and viability (propidium iodide exclusion) were optimized and tested using known antiproliferative compounds. The utility of this in vitro screen was evaluated further using a set of compounds containing eight known to cause developmental neurotoxicity and eight presumably nontoxic compounds. Six out of eight developmental neurotoxicants significantly inhibited ReNcell CX cell proliferation and/or viability, whereas two out of eight nontoxic chemicals caused only minimal effects. These results demonstrate that chemical effects on cell proliferation and viability can be assessed via high-throughput methods using hNPCs. Further development of this approach as part of a strategy to screen compounds for potential effects on nervous system development is warranted.

Preclinical development of gene therapy for Parkinson's disease

Multiple targets and pathways may be amenable to the development of gene therapy approaches for Parkinson's disease. This article discusses some of the cellular and brain circuit pathways relevant to Parkinson's disease that would be clinically amenable to gene therapy. Approaches could be classified according to two main categories, i.e. symptomatic vs. neuroprotective/neurorestorative strategies. Examples of the different possibilities currently in development are given and feature both dopaminergic and non-dopaminergic symptomatic treatments of parkinsonian symptoms and/or L-DOPA-induced side effects, anti-apoptotic neuroprotective strategies and growth-factor delivery for neuroprotection/neurorestoration. While gene therapy has been mostly used so far for enhancing the expression of the target gene, the use of dominant negative or siRNA opens new possibilities. This, combined with the key feature of gene delivery that offers access to intracellular signalling pathways, is likely to further expand the number of proposed targets to be studied.