GDNF and Alzheimer disease: Recently the secretome of DPSCs has also proven beneficial in models of Alzheimer’s disease [18] and spinal cord injury [19], and DPSCs are known to express valuable neurotrophic factors including neurotrophin-3 (NT-3), glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor, and nerve growth factor (NGF) [20,21].