Neural stem cells: therapeutic potential for neurodegenerative diseases.

INTRODUCTION: Neural stem cells (NSCs) from specific brain areas or developed from progenitors of different sources are of therapeutic potential for neurodegenerative diseases. SOURCES OF DATA: Treatment strategies involve the (i) transplantation of exogenous NSCs; (ii) pharmacological modulations of endogenous NSCs and (iii) modulation of endogenous NSCs via the transplantation of exogenous NSCs. AREAS OF AGREEMENT: There is a consensus about the therapeutic potential of transplanted NSCs. The ability of NSCs to home into areas of central nervous system injury allows their delivery by intravenous injection. There is also a general agreement about the neuroprotective mechanisms of NSCs involving a 'bystander effect'. AREAS OF CONTROVERSY: Individual laboratories may be using phenotypically diverse NSCs, since these cells have been differentiated by a variety of neurotrophins and/or cultured on different ECM proteins, therefore differing in the expression of neuronal markers. GROWING POINTS: Optimization of the dose, delivery route, timing of administration of NSCs, their interactions with the immune system and combination therapies in conjunction with tissue engineered neural prostheses are under investigation. AREAS TIMELY FOR DEVELOPING RESEARCH: In-depth understanding of the biological properties of NSCs, including mechanisms of therapy, safety, efficacy and elimination from the organism. These areas are central for further use in cell therapy. CAUTIONARY NOTE: As long as critical safety and efficacy issues are not resolved, we need to be careful in translating NSC therapy from animal models to patients.