NSCs of embryonic or adult origin can differentiate into neurons, astrocytes, and oligodendrocytes, which fill in the neuronal cells lost during AD pathology, and secrete brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF), which improves synaptic plasticity, supports the survival of pre-existing neurons, and maintains function (Pecoraro et al., 2025; Wu H. et al., 2025). This evidence concerns the gene BDNF and Alzheimer disease.