Novel and immortalization-based protocols for the generation of neural CNS stem cell lines for gene therapy approaches.

Transplantation of neural cells engineered to produce growth factors or molecules with antitumor effects have the potential of grafted cells to be used as vectors for protein delivery in animal models of diseases. In this context, neural stem cells (NSCs), since their identification, have been considered an attractive subject for therapeutic applications to the damaged brain. NSCs have been shown to include attributes important for potential successful ex vivo gene therapy approaches: they show extensive in vitro expansion and, in some cases, a particular tropism toward pathological brain areas. Clearly, the challenges for future clinical development of this approach are in the definition of the most appropriate stem cells for a given application, what genes or chemicals can be delivered, and what diseases are suitable targets. Ideally, NSC lines should be homogeneous and well characterized in terms of their in vitro stability and grafting capacity. We discuss two possible approaches to produce homogeneous and stable progenitor and NSC lines that exploit an oncogene-based immortalization, or, in the second case, a novel protocol for growth factor expansion of stem cells with radial glia-like features. Furthermore, we describe the use of retroviral particles for genetic engineering.