A new age in understanding adult hippocampal neurogenesis in Alzheimer's disease.

Several lines of evidence have established that proliferation and differentiation of neural stem cells into neurons within the sub-granular zone of the dentate gyrus, a process named adult hippocampal neurogenesis, contribute to maintaining healthy cognitive functions throughout life. The rate of adult hippocampal neurogenesis decreases with aging and a premature impairment of adult hippocampal neurogenesis has been observed both in animal models of Alzheimer's disease and human post-mortem tissues. The causal relationship between adult hippocampal neurogenesis and the development of Alzheimer's disease pathology has, however, not been established. This is partly due to the limitation of recapitulating the development of Alzheimer's disease pathology in rodent models and the lack of translatable biomarkers to identify tractable targets in humans. While it is tempting to postulate that adult hippocampal neurogenesis could be leveraged to improve cognitive deficits in Alzheimer's disease, consensual results have yet to be reached to fully explore this hypothesis. In this review, we discuss how the recent progress in identifying molecular pathways in adult hippocampal neurogenesis provides a good framework to initiate strategies for drug-based intervention in neurodegenerative diseases, especially in Alzheimer's disease. We outline how discrepancies in pre-clinical disease models and experimental methodology have resulted in contradictory findings and propose a shift towards using more translatable approaches to model neurogenesis in Alzheimer's disease. In particular, we review how exploring novel experimental paradigms including the use of human induced pluripotent stem cells and more complex cell culture systems, as well as standardizing protocols used to investigate evidence of neurogenesis in human tissues, could deliver deeper mechanistic insights that would kick-start innovative drug discovery efforts to promote healthy aging and cellular rejuvenation.