The Journal of Neuroscience, May 14, 2008, 28(20):5240-5247; doi:10.1523/JNEUROSCI.0344-08.2008
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Development/Plasticity/Repair
Latent Stem and Progenitor Cells in the Hippocampus Are Activated by Neural Excitation
Tara L. Walker,
Amanda White,
Debra M. Black,
Robyn H. Wallace,
Pankaj Sah, and
Perry F. Bartlett
Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
Correspondence should be addressed to Perry F. Bartlett, Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia. Email: p.bartlett{at}uq.edu.au
The regulated production of neurons in the hippocampus throughout life underpins important brain functions such as learning and memory. Surprisingly, however, studies have so far failed to identify a resident hippocampal stem cell capable of providing the renewable source of these neurons. Here, we report that depolarizing levels of KCl produce a threefold increase in the number of neurospheres generated from the adult mouse hippocampus. Most interestingly, however, depolarizing levels of KCl led to the emergence of a small subpopulation of precursors (approximately eight per hippocampus) with the capacity to generate very large neurospheres (>250 µm in diameter). Many of these contained cells that displayed the cardinal properties of stem cells: multipotentiality and self-renewal. In contrast, the same conditions led to the opposite effect in the other main neurogenic region of the brain, the subventricular zone, in which neurosphere numbers decreased by
40% in response to depolarizing levels of KCl. Most importantly, we also show that the latent hippocampal progenitor population can be activated in vivo in response to prolonged neural activity found in status epilepticus. This work provides the first direct evidence of a latent precursor and stem cell population in the adult hippocampus, which is able to be activated by neural activity. Because the latent population is also demonstrated to reside in the aged animal, defining the precise mechanisms that underlie its activation may provide a means to combat the cognitive deficits associated with a decline in neurogenesis.
Key words: hippocampus; stem cell; precursor; activation; depolarization; potassium
Received Jan. 25, 2008;
revised March 19, 2008;
accepted April 9, 2008.
Correspondence should be addressed to Perry F. Bartlett, Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia. Email: p.bartlett{at}uq.edu.au
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