Wednesday, August 28, 2013

Human stem cells: Scientists grow brain-buds - Spiegel Online

only about four millimeters wide, the collection of cells, researchers have bred in the laboratory – but they allow to map the development of the human brain during the first few weeks of an embryo. Although it is not a true mini-brains, which is why the researchers cautiously speak of “cerebral organoids”. But with their help, developmental disorders and diseases could be better than exploring, for example, in mice.

the team at Madeline Lancaster and Jürgen Knoblich the Vienna Institute for Molecular Biotechnology of the scientific journal “Nature” writes the structures from human embryonic stem cells created. In further experiments, the researchers use so-called iPS cells: ordinary body cells that have been reprogrammed to become stem cells


stem cells possess an enormous capacity for self-organization. Under suitable conditions, they self-assemble into three-dimensional tissues. The researchers took advantage of this and let the stem cells at a certain stage of development grow in a rotating bioreactor. By the rotation of the nutrient supply to the cells is improved.

grown in two months

period of about two months, the organoids reached their final size. The tissues were viable indefinitely, the researchers write. Some had already lived for ten months in the reactors. Because it did not have blood vessels that provide nutrients and oxygen transported into the interior of the size of the organoids, however, is limited. Therefore, the cells in the core structures of the die, the scientists explain.

studies demonstrated that the organoids were divided into different areas distinguishable from one another, as is the case with front-, middle-and hindbrain. Similar to the natural development of the human cerebral cortex different layers formed in organ culture in which different cell populations were formed around nerve cells and glial cells. Individual, spatially distant areas were interconnected. “On average, brain-organoids can mimic the development of brain structures until the ninth week of pregnancy,” says Lancaster.

“Nature” provide researchers an example of the application of their organoids before: the study of microcephaly. Of this developmental disorder sufferers have an unusually small head and a small brain. They are usually mentally retarded. In animal studies with mice can explore this disorder bad, because crucial steps in developing rat brain have been different.

The researchers

a microcephaly patient withdrawals some skin cells, which they converted to iPS cells. Subsequently cultured organoids compared them with those that had emerged from healthy cells. In microcephaly organoids, the team found a total of less progenitor cells and already differentiated neurons. With microcephaly, the stem cells begin therefore too early to form combinations neurons, rather than to continue to divide and thus to increase their number. Finally, can the less nerve cells are formed.

No “brain in a Petri dish”

“In the future we would also like other diseases that may be associated with developmental brain disorders – such as autism or schizophrenia – rebuild in culture and explore,” says study leader Knoblich


for the pharmaceutical industry such culture systems might be of importance, such as the effect of drugs and chemicals to test. So far, this is done either in animals or in cell cultures.

Despite the compelling data to realize a “brain in a Petri dish” was further out of reach, says the German stem cell researcher Oliver Brustle of the University of Bonn, the investigation of his colleagues. Within the Organoid the different brain areas were randomly distributed. They did not possess the same shape and spatial organization as in the brain.

work but was impressively shown that such cultures in developmental biology and biomedical applications could be used as a tool.


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