Genetic perpetuation of in vitro expanded human neural stem cells: cellular properties and therapeutic potential

Long-term propagated human neural stem cells (self-renewing and multipotent) allow for the unlimited and predictable generation of different types of human neural cells in vitro. In addition, these cell lines may be of help for the elucidation of basic neuro-developmental issues, and also for the development of innovative therapeutic strategies for nervous system disorders (through cell replacement and/or gene transfer-based therapies). In this article we summarize our current knowledge about these long-term cultured cells, particularly that of immortalized cells, with the aim of critically addressing their usefulness and potential for therapeutic use. Perpetuation methods and in vitro properties of immortalized cells are analyzed. Although reports on in vivo studies are scarce, present data on survival, integration, migration, and differentiation of the cells indicate that they may be useful for the development of cellular and genetic therapies, in various models of neurodegeneration. A great deal of basic and applied research remains to be done in order to fully explore, understand, and exploit the therapeutic potential of human neural precursor cells.