Human Embryonic Stem Cell-Derived Neural &
Neuronal Cells in Vitro & in Vivo
Treatment of Experimental Cerebral Ischemia
By Riikka Äänismaa
Tampere University Press
Distributed By Coronet Books
$77.50 Paper original
Human pluripotent stem cells and their neural derivatives are considered potential regenerative material for treating central nervous system deficits resulting from traumatic injury (e.g. spinal cord injury) or neurodegenerative disease (e.g. ischemic stroke, multiple sclerosis, Parkinson’s disease). Although several studies have examined stem cell transplantation as a treatment for these conditions, the results have been highly variable and much more work is needed to address the many remaining questions. Clinical applications for neural cell transplants are currently being designed to treat brain injuries resulting from stroke and spinal cord injury.
This thesis describes efforts towards the generation of an efficient and simple protocol to differentiate human embryonic stem cells (hESCs) into neural progenitors and young neuronal cells. Additionally, a neuron-specific culturing matrix has been designed to improve the maintanence and differentiation of neural progenitors. The electrophysiologic properties of neuronal networks were also investigated in vitro. In addition, neural progenitor cell transplantation was performed in animal models of stroke and evaluated with regard to the optimal transplantation route and their effects on functional recovery of animals in combination with rehabilitation, i.e. housing in an enriched environment.
Neural differentiation of hESCs was achieved with a relatively simple differentiation protocol that was assessed using molecular biological methods. A hESC line-dependent variation in differentiation efficacy was observed. Regardless of the hESC line used, neuronal cells that were produced formed functional electrically active networks in vitro. Thus, the method developed in this thesis clearly produces functional neuronal cells. Moreover, neural adhesion molecule antibodies effectively produced a specific surface matrix for the selection of neuronal cultures. In animal studies, the optimal delivery route to induce the accumulation of transplanted neural progenitor cells into damaged brain tissue was evaluated. The non-invasiveness of intravenous administration of cell grafts would be optimal for a clinical setting. Based on our findings that grafted neural progenitor cells accumulated mainly in the liver, kidneys, and spleen following intravenous administration, this method appears to be not effective. We also attempted intracerebral transplantation of the neural progenitor cells into rats with experimentally induced stroke that were housed in either an enriched environment or standard cages. Regardless of the type of housing, rats with neural progenitor cell transplants showed significant improvement in a postural support task during the first month after treatment when compared to vehicle-treated animals. Neither group of rats showed any improvement in a reaching task. In vivo cell survival was minimal.
In conclusion, hESCs can be efficiently differentiated into neural progenitors and neuronal cells, but hESC line-dependent variations in differentiation potential must be considered, especially when planning and designing clinical applications. In addition, the electrophysiologic properties of the produced neuronal cells and networks should be carefully studied in vitro to ensure the functionality of the neurons. Neuron-specific antibodies can be used as a selective culturing matrix for neuronal cells. Intravenous transplantation of the cell grafts into the ischemic brain is currently not feasible and more work is needed to enhance the efficacy of intracerebrally transplanted cells.
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