Neural Stem Cells

	[Enlarge Image] Stem cell-derived dopamine neurons 3 months after transplantation into the brain of Parkinsonian animal

We have described how stem cells, derived from both rat and human midbrain, can be proliferated and differentiated into dopamine neurons in culture. Transplantation of such stem cell-derived dopamine neurons into the brain can improve behavioral symptoms in animal models of Parkinson's Diseases. 

Similar strategies are now being pursued for generating other neuronal and glial cell types, including GABA neurons and oliogodendrocytes. These cell types will be tested in animal models of Huntington's Disease and demyelination.

	[Enlarge Image] CNS stem cells grown in lowered oxygen expressing Nestin (green) and Cul2 (red) -- a protein known to interact with the product of the tumor supressor gene VHL.

We have described in vitro ambient oxygen concentration as a critical parameter in CNS stem cell culture. Standard tissue culture is carried out at 20 percent, whereas oxygen concentrations in the brain are dramatically lower. Reducing ambient oxygen levels to 2 to 4 percent (physiological range in vivo) leads to increased CNS precursor cell proliferation and survival, and affects neuronal subtype choice. Lowered oxygen culturing might be an important parameter for in vitro studies, using primary tissue. Current studies address the use of lowered oxygen in embryonic stem cell culture.

Long-term proliferation of midbrain CNS precursors leads to changes in the expression of regional patterning genes with subsequent loss of dopaminergic differentiation. We are using differential gee expression profiling to further characterize these changes. Identification and re-introduction of the key molecules involved in regional patterning might allow for rescue of dopaminergic differentiation in long-term cultured stem cells. Similar assays are used to describe maintenance or loss of regional identity in precursor and stem cells from other brain regions.