Stem cells and neurogenesis in relation to Alzheimer's disease Models

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder associated with progressive cognitive decline and extensive neuropathology throughout the brain. Its main features include limited cell loss in selected subregions, generalized brain atrophy, and gradual accumulation of β-amyloid plaques and neurofibrillary tangles in several brain regions. One of the earliest and most prominently affected brain regions is the hippocampus, a brain structure involved in learning and memory that displays prominent cell loss in its CA1 subregion as well as abundant plaque and tangle pathology. Recent studies have identified the presence of stem cells in brains of adult rodents, primates, and also humans. Only in a few subregions do these stem cells continue to proliferate and differentiate to form new neurons within the mature brain, a process known as adult neurogenesis. Adult neurogenesis occurs in the hippocampal subgranular zone and in the subventricular zone of the lateral ventricles and olfactory bulb. These adult-generated neurons are involved in learning and memory and respond well to various hormonal and environmental factors, like stress, age, physical exercise, and also, surprisingly, to hippocampal insults. With the discovery of functional adult neurogenesis and increasing insights role in cognition and into its environmental control, hopes have risen that stem cells in the adult brain could one day be used to modulate neurodegeneration, and/or cognition e.g., by stimulating neuroregeneration. In this chapter, we discuss properties of stem cells and neurogenesis and their changes during the development of neuropathology and functional deficits in Alzheimer’s disease and some of its main animal models. In addition, we discuss possibilities to stimulate stem cells and neurogenesis for therapeutic purposes in relation to dementia