Stem cell research seems like it is not going anywhere fast. In fact breakthroughs are being announced more and more frequently. This week a Johns Hopkins team has discovered in young adult mice that a lone brain stem cell is capable not only of replacing itself and generating specialized neurons and glia (important types of brain cells), but also of taking a wholly unexpected path: generating two new brain stem cells. Previously it was not known that the brain was able to produce two neuron types from a single source.
Hongjun Song, Ph.D., professor of neurology and neuroscience and director of the Stem Cell Program in the Institute for Cell Engineering, the Johns Hopkins University School of Medicine explains:
“Now we know they don’t just maintain their numbers, or go down in number, but that stem cells can amplify. If we can somehow cash in on this newly discovered property of stem cells in the brain, and find ways to intervene so they divide more, then we might actually increase their numbers instead of losing them over time, which is what normally happens, perhaps due to aging or diseases. It’s a simple idea that forced us to confront a lot of complex technical issues. With so many millions of cells in the relatively large mouse brain, labeling a single stem cell and then chasing its family history was like finding a needle in a haystack.”
Using mice genetically modified with special genes that color code cells for easy labeling and tracking, the Hopkins team injected a very small amount of a chemical into about 50 mouse brains to induce extremely limited cell labeling.
The scientists then developed computer programs and devised a new imaging technique that allowed them to examine stained slices of the mouse brain and, ultimately, follow single, randomly chosen radial glia-like stem cells over time. The method allowed them to track down all the new cells derived from a single original stem cell.
The team then followed the fates of all the marked radial glia-like stem cells for at least a month or two, and examined some a full year later to discover that even over the long term, the “mother” cell was still generating itself as well as different kinds of progeny.
Gila cells are more or less an unknown quantity in the nervous system. In humans and other mammals, in insects, in birds; in practically all life forms with a brain, gila cells exist, in the central nervous system and the periphery, binding the neurons together.
For some time it was thought that this was all they did: supported and bound the development of neurons. They are everywhere in the brain, but very little was known about them.
Attempts to study these cells have been hampered somewhat: remove the gila, and neurons where they were, die out. Remove the neurons, and gila die out. There is obviously a sort of symbiotic relationship there, but no-one knows that it is, as there has never been any opportunity to study either cell type without the other, and we are still many, many decades from being able to perfectly simulate an entire cell in all its functions, to understand in that way, without knowing it first.
Guo-li Ming, associate professor of neurology and neuroscience and a member of the Neuroregeneration Program in the Institute for Cell Engineering continues regarding the breakthrough:
“We reconstituted single stem cells’ family trees to look at the progeny they gave rise to. We discovered that single cells in an intact animal nervous system absolutely do exhibit stem-cell properties; they are capable of both replicating themselves and producing different types of differentiated neural progeny.”
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Written by Sy Kraft