A human neuron injury model for molecular studies of axonal regeneration
Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel. Experimental Neurology
(Impact Factor: 4.7).
10/2009; 223(1):119-27. DOI: 10.1016/j.expneurol.2009.09.019
The enhancement of regeneration of damaged axons in both the peripheral and central nervous systems is a widely pursued goal in clinical medicine. Although some of the molecular mechanisms involved in the intrinsic neurite regeneration program have been elucidated, much additional study is required for development of new therapeutics. The majority of studies in the field of axonal regeneration have utilized animal models due to obvious limitations of the accessibility of human neural tissues. Here we describe the use of human embryonic stem cell (hESC)-derived neurons as a novel model for studying neuronal responses to axonal injury. Neurons were generated using PA6 induction and neurites injured in vitro using trituration or laser microdissection. Lesioned neurons re-extended neurites with distinct growth cones. Expression of proteins associated with regeneration were observed in this human in vitro system, including appearance of importin beta1 in processes after neuritomy. Laser-transected hESC-derived neuronal cultures were analyzed for their transcriptional response to injury using Affymetrix expression microarrays. Profound changes in gene expression were observed over a time course of 2 to 24 hours after lesion. The expression of several genes reported to be involved in axonal injury responses in animal models changed following injury of hESC-derived neurons. Thus, hESC-derived neurons may be a useful in vitro model system for mechanistic studies on human axonal injury and regeneration.
Available from: web.mit.edu
- "The drastic increase in blast-induced traumatic brain injuries among both military (nearly 50% of the Iraq war injured returnees) and civilian casualties – mainly due to terrorists explosive devices – have generated important research efforts in the last few years  . Impact-and/or acceleration-induced brain traumatic injuries have already been the focus of many cellular and macroscopical studies through in vivo        , ex vivo  , in vitro     , medical postanalysis     and modeling approaches              . However, the specific effects of a blast – a pressure wave of finite amplitude generated by a rapid release of energy  – on the brain is still widely unknown. "
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ABSTRACT: Traumatic brain injuries have recently been put under the spotlight as one of the most important causes of accidental brain dysfunctions. Significant experimental and modeling efforts are thus underway to study the associated biological, mechanical and physical mechanisms. In the field of cell mechanics, progress is also being made at the experimental and modeling levels to better characterize many of the cell functions, including differentiation, growth, migration and death. The work presented here aims to bridge both efforts by proposing a continuum model of a neuronal cell submitted to blast loading. In this approach, the cytoplasm, nucleus and membrane (plus cortex) are differentiated in a representative cell geometry, and different suitable material constitutive models are chosen for each one. The material parameters are calibrated against published experimental work on cell nanoindentation at multiple rates. The final cell model is ultimately subjected to blast loading within a complete computational framework of fluid-structure interaction. The results are compared to the nanoindentation simulation, and the specific effects of the blast wave on the pressure and shear levels at the interfaces are identified. As a conclusion, the presented model successfully captures some of the intrinsic intracellular phenomena occurring during the cellular deformation under blast loading that potentially lead to cell damage. It suggests, more particularly, that the localization of damage at the nucleus membrane is similar to what has already been observed at the overall cell membrane. This degree of damage is additionally predicted to be worsened by a longer blast positive phase duration. In conclusion, the proposed model ultimately provides a new three-dimensional computational tool to evaluate intracellular damage during blast loading.
Available from: Michael Yee
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ABSTRACT: Study of the human neurotrophic herpesvirus varicella-zoster virus (VZV) and of its ability to infect neurons has been severely limited by strict viral human tropism and limited availability of human neurons for experimentation. Human embryonic stem cells (hESC) can be differentiated to all the cell types of the body including neurons and are therefore a potentially unlimited source of human neurons to study their interactions with human neurotropic viruses. We report here reproducible infection of hESC-derived neurons by cell-associated green fluorescent protein (GFP)-expressing VZV. hESC-derived neurons expressed GFP within 2 days after incubation with mitotically inhibited MeWo cells infected with recombinant VZV expressing GFP as GFP fusions to VZV proteins or under an independent promoter. VZV infection was confirmed by immunostaining for immediate-early and viral capsid proteins. Infection of hESC-derived neurons was productive, resulting in release into the medium of infectious virions that appeared fully assembled when observed by electron microscopy. We also demonstrated, for the first time, VZV infection of axons and retrograde transport from axons to neuronal cell bodies using compartmented microfluidic chambers. The use of hESC-derived human neurons in conjunction with fluorescently tagged VZV shows great promise for the study of VZV neuronal infection and axonal transport and has potential for the establishment of a model for VZV latency in human neurons.
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ABSTRACT: Effective therapeutic interventions for injuries of the central nervous system such as spinal cord injury are still unavailable, having a great impact on the quality of life of victims and their families, as well as high costs in medical care. Animal models of spinal cord injury are costly, time-consuming and labor-intensive, making them unsuitable for screening large numbers of experimental conditions. Thus, culture models that recapitulate key aspects of neuronal changes in central nervous system injuries are needed to gain further understanding of the pathological and regenerative mechanisms involved, as well as to accelerate the screening of potential therapeutic agents. In this study we differentiated adherent cultures of dissociated human fetal spinal cord neural precursors into postmitotic neurons which we could then detach from culture plates and successfully freeze down in a viable state. When replated in neuronal medium without neurodifferentiating factors, these ready-to-use human spinal cord neurons remained viable, postmitotic and regenerated neurites in a cell density-dependent manner. Insulin-like growth factor 1 and growth hormone had no effect on neurite regeneration while brain-derived neurotrophic factor increased both the number of cells with neurites as well as the average neurite length. Our model can be applied to investigate factors involved in neuroregeneration of the human spinal cord and since adherent dissociated cell cultures are used, this system has significant potential as a screening platform for therapeutic agents to treat spinal cord injury.
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