Similar to BDNF, IGF-1 is a restorative factor that facilitates hippocampal neurogenesis and has been used as a promising therapeutic molecule to revitalise cognitive abilities in aged animals [5]. Researches in the past focused on using IGF-1 peptides to overcome cognitive deficits in aged brain. Administration of IGF-1 peptides via intracerebroventricular (ICV) infusion [23] or osmotic minipumps implants [24] has successfully increased hippocampal neurogenesis and ameliorated age-related cognitive decline. By contrast, current studies are now paying more attention to the application of genes.