Studies also indicate that neurotrophic factors, such as glial cell line-derived neurotrophic factor (GDNF), neurotrophin-3 (NT-3), brain-derived neurotrophic factor (BDNF), and vascular endothelial growth factor (VEGF), promote neuroprotection and have a protective effect on the effectiveness of cell therapy against neurodegenerative diseases (Nosrat et al., 2004; Sakai et al., 2012). This evidence concerns the gene GDNF and neurodegenerative disease.