BDNF and Alzheimer disease: From the evidence presented, stem cell therapy has shown to exert beneficial modulation effects on the BDNF/TrkB signalling pathway and its downstream cascades in mitigating AD by mainly upregulating BDNF and TrkB levels, suppressing GSK-3β activity, increasing autophagy and CREB activity, reducing neuroinflammation and oxidative stress, and improving cognitive functions as summarized in Table 1 and Figure 2.