Table 1.

Factors That Influence Neural Stem/Precursor Cell Survival and Function

Measured Responses	In vitro	In vivo
Cell growth and differentiation	Multipotent cells can be obtained and grown from neurogenic areas in brain.	Neurogenesis results in new neurons/glia in the hippocampal dentate gyrus.
Proliferation and differentiation	Neural precursor cell growth is dependent upon cell density and cell-cell contact.	Changes in neurogenesis are associated with changes in cognitive function.
Radiation effects have an early impact on cell viability	Irradiation induces acute (hrs-days) oxidative stress and apoptosis.	Neural precursor cells extremely sensitive, undergoing apoptosis after clinically relevant doses within 48 hr.
Reactive oxygen species, radiation dose, and new neurons	Radiation-induced oxidative stress in multipotent neural precursor cells is dose dependent.	Radiation reduces neurogenesis in a dose dependent fashion.
Radiation effects have a chronic impact on cell viability and differentiation	Irradiation induces persistent (weeks-months) oxidative stress.	Radiation-induced changes in neurogenesis are persistent
Microenvironmental factors can impact the response of neural precursor cells	Protracted irradiation enriches cultures for radioresistant CD133+ neural precursor cells	Alterations in the microenvironment (inflammation, oxidative stress) are associated with altered neurogenesis and cognitive function after irradiation.
Neuronal activity		Neuronal activity in the dentate gyrus is adversely affected by irradiation