The study comprehensively dissected the roles of neural stem cells (NSCs), induced pluripotent stem cells (iPSCs) and mesenchymal stem cells (MSCs) in neural replacement, neuroinflammation modulation and neuroplasticity enhancement, and also explored the application of CRISPR/Cas9 in modifying the pathogenic variants of AD-related genes (APP, PSEN1 and PSEN2). The gene discussed is PSEN2; the disease is Alzheimer disease.