Neural Differentiation Of Embryonic Stem Cells

Human embryonic stem (hES) cells are expected to become a cell source for use in a variety of neurodegenerative diseases. In vitro neural differentiation of hES cells provides a useful model to study early neural development in human, as well as application of hES cell-derived neural cells in neurodegenerative diseases. The current study includes three parts. (1) Mouse embryonic stem cells (mES) were differentiated into homogeneous neural glial precursors through a modified protocol. The mES derived neural cells were transplanted into the mouse model of multiple sclerosis, and enhanced the motility of the diseased mice. Furthermore, in order to track the transplanted cells and study their differentiation potential in vivo, we established stable mES cell line expressing luciferase. (2) To establish an in vitro model for investigating the molecular mechanisms to regulate neurogenesis and neural stem cell self-renewal, we differentiate hES cells, previously established and characterized in our laboratory, into neural cells in monolayer culture with serum-free medium. Neural induction of hES cells (Oct-4+, Sox2+, Nestin-) is categorized in three stages by morphology and marker expression: neuroectoderm determination, neurogenesis (Oct-4-, Sox2+, nestin+), and neuron maturity (Sox2-, Tuj-1+, MAP2+). The differentiation model system closely mimics the early embryonic development of neural system and provides a large quantity of neural stem/precursor cells. We are able to demonstrate that the neural stem/precursor cells derived from hES cells could form neurospheres in suspension culture as neural precursors from embryonic or adult brain tissues do, and differentiate into neuron, astrocyte and oligdendrocytes in vitro. To faciliate the research using this neural precursor cells, the cell cryopreserveation and gene transfection methods were also established. (3) We have employed this neural precursor cell model to further investigate the effect of bFGF on the neurogenesis, growth, differentiation and migration of neural precursor cells. We demonstrate that bFGF promotes growth and migration of neural precursor cells, although it impairs the maturity of neurons. The molecular mechanism about how bFGF functions in the system is under investigation. Thus, our system not only provides a source of neuroectodermal cells, neural progenenitor cells and neurons for cell therapy research, but also offers a paradigm to dissect mechanisms of neural induction and cell lineage specification during early human development.