GDNF and Alzheimer disease: For example, NGF availability was increased in the forebrain of mild Alzheimer’s disease patients by autologous fibroblasts genetically modified to produce and secrete human NGF [139,140]; human GDNF was delivered via bilateral continuous intraputamenal infusion to Parkinson’s disease patients [141]; and CNTF was intrathecally delivered to ALS patients via an encapsulated genetically modified baby hamster kidney cells that release human CNTF [142].