The cognitive aspect of AD is believed to be correlated with the decline of ChAT (choline acetyltransferase) activity [80], and theory was tested by injecting BMSCs (bone marrow stem cells) and NGF-BMSCs (gene-modified bone marrow stem cells) into the hippocampus of a rat model with Alzheimer’s disease [80]. The gene discussed is NGF; the disease is Alzheimer disease.