Stem cells have been suggested as a possible fountain of youth for replacing tissues lost during aging. In the brain, replacing lost neurons may be possible, but is a challenge, as they have to then be re-connected with their appropriate targets. Furthermore, during aging memories are stored in specific circuits that might not be fully replaced by new neurons. Perhaps a more realistic and practical strategy for affecting the aging process would be to prevent the loss of neurons from occurring, thus retaining intact circuitry. Glial cell line derived neurotrophic factor (GDNF) has been shown to reverse some aspects of aging in the monkey brain - specifically loss of dopamine which results in slowed movement. We have recently shown that GDNF can be directly infused into the adult human brain and has significant effects on the symptoms of Parkinson's Disease. New data will be presented showing that human neural stem cells grown in the culture dish can be genetically modified to release GDNF. These cells survive transplantation into the brain and may be used in the future as "mini pumps" to protect aging neurons. It might be that using such approaches it will be possible to ward off the effects of aging in the brain, giving a better quality of life. Stem cells might not be the fountain of youth, but provide a fountain of youth through release of growth factors such as GDNF.