NGF and Alzheimer disease: Adult neurogenesis can be stimulated through extrinsic administration of chemical agents and growth factors in the context of AD, such as: Erythropoietin [142,143,144], fluoxetine [145], granulocyte colony stimulating factor (G-CSF) and AMD3100 [146], brain-derived neurotrophic factor (BDNF) [147,148,149], insulin growth factor-1 (IGF-1) [150], nerve growth factor (NGF) [151,152], vascular endothelial growth factor (VEGF) [153], growth, and transforming growth factor β (TGF-β) [154].