Fig. 3

Potential mechanisms underlying the stem cell therapies. This schematic illustrates how stem cell–based therapies combat neurodegeneration through multiple mechanisms in one integrated approach. Newly grafted or converted neural cells (center) replace or supplement degenerating neurons (upper left), while transplanted stem cells or induced cells also bolster neurogenesis (upper right) by differentiating into neurons, astrocytes, oligodendrocytes, or interneurons. Moreover, these cells secrete neurotrophic factors (left) that enhance cell survival and plasticity, and release anti-inflammatory mediators (lower left) to modulate immune responses involving peripheral macrophages, microglia, and astrocytes. Finally, healthy mitochondria can be transferred to damaged neurons (lower right), improving energy production and reducing oxidative stress