Others have tried a different strategy of providing trophic support to degenerating neurons, including the infusion of glial cell line-derived neurotrophic factor (GDNF) in patients with PD [15,16,17,18] and manufacturing and temporarily implanting nerve growth factor (NGF)-producing cells targeting the NBM in patients with Alzheimer’s disease (AD) [19,20]. This evidence concerns the gene GDNF and Parkinson disease.