MAPT and Alzheimer disease: Here, for the first time, we explored the effects of clinical‐grade hUC‐MSCs on the recovery of cognitive ability in SAMP8 mice, which is a senescence‐accelerated mouse model of AD; and we demonstrated that the core functional factor, hepatocyte growth factor (HGF), secreted from hUC‐MSCs plays important roles in hUC‐MSC‐modulated recovery of damaged neural cells by down‐regulating hyperphosphorylated tau, improving neurofibrillary tangles, reversing spine loss, and promoting synaptic plasticity in the aged hippocampus, which are all closely associated with memory deficits.