Effects of oxygen concentration on the proliferation and differentiation of mouse neural stem cells in vitro.
OBJECTIVE
Cerebral ischemia is known to elicit the activation of neural stem cells (NSCs); however its mechanism is not fully determined. Although oxygen concentration is known to mediate many ischemic actions, there has been little attention given to the role of pathological oxygen changes under cerebral ischemia on the activation of NSCs. We investigated the effects of various oxygen concentrations on mouse neural stem cells in vitro.


METHODS
NSCs were cultured from the ganglionic eminence of fetal ICR mice on embryonic day 15.5 using a neurosphere method. The effects of oxygen concentrations on proliferation, differentiation, and cell death of NSCs were evaluated by bromodeoxyuridine (BrdU) incorporation, immunocytochemistry, and TUNEL assay, respectively.


RESULTS
The highest proliferation and the neuronal differentiation of the NSCs were observed in 2% oxygen, which yielded significantly higher proportions of both BrdU-labeled cells and Tuj1-positive cells when compared with 20% and 4% oxygen. On the other hand, the differentiation to the astrocytes was not affected by oxygen concentrations, except in the case of anoxia (0% oxygen). The cell death of the NSCs increased in lower oxygen conditions and peaked at anoxia. Furthermore, the switching of the neuronal subtype differentiation from GABA-positive to glutamate-positive neurons was observed in lower oxygen conditions.


CONCLUSIONS
These findings raise the possibility that reduced oxygen levels occurring with cerebral ischemia enhance NSC proliferation and neural differentiation, and that mild hypoxia (2% oxygen), which is known to occur in the ischemic penumbra, is suitable for abundant neuronal differentiation.
Horie
Nobutaka
N
Department of Neurobiology and Behavior, Unit of Basic Medical Sciences, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan. nobstanford@gmail.com
So
Kenji
K
Moriya
Takahiro
T
Kitagawa
Naoki
N
Tsutsumi
Keisuke
K
Nagata
Izumi
I
Shinohara
Kazuyuki
K
D000818:Animals; D001253:Astrocytes / Q000502:physiology*; D001479:Basal Ganglia / Q000166:cytology*; D016923:Cell Death; D002454:Cell Differentiation; D015687:Cell Hypoxia; D049109:Cell Proliferation; D004622:Embryo, Mammalian / Q000166:cytology; D051379:Mice; D008813:Mice, Inbred ICR; D009474:Neurons / Q000502:physiology*; D010100:Oxygen / Q000494:pharmacology / Q000502:physiology*; D013234:Stem Cells / Q000502:physiology*
D010100:Oxygen