Neurons can be restored without stem cells
Scientists from the Helmholtz Center and Ludwig-Maximilian University in Munich, led by Magdalena Götz and Benedikt Berninger, have demonstrated that astrocytes taken from young mice (the star-shaped auxiliary cells surrounding neurons that act as a framework and participate in metabolism in brain tissue) can be transformed into two a type of active neurons capable of forming synapses and transmitting nerve impulses.
Previously, the Goetz and Berninger research group was able to show that astroglia cells (aggregates of astrocytes) can transform into neurons after infection of astrocytes with specially designed viruses carrying genes encoding transcription factors. But the neurons obtained from astroglia turned out to be incapable of forming functional synapses, which called into question the practical value of the entire technique aimed at creating a way to obtain active full-fledged neurons.
Now Berninger and colleagues have managed to overcome the problem that arose in the previous study. The introduction of another gene encoding the neurogenin-2 protein led to the formation of so-called excitatory neurons that activate neighboring cells, and with the help of another gene, Dlx2, it was possible to obtain inhibitory neurons that weaken the activity of neighboring cells. The results of the work are described in the article Directing Astroglia from the Cerebral Cortex into Subtype Specific Functional Neurons, published this week in the journal Public Library of Science Biology. (The picture shows an astrocyte from the mouse brain transformed into an excitatory neuron. Molecules specific to excitatory neurons glow green, and molecules that provide the main function of neurons, synaptic plasticity, through which interaction and signal transmission between neurons occur, glow white.)
Dr. Berninger believes that with the help of the technique developed by his group, other types of neurons can be obtained by introducing the corresponding gene into astrocytes. In this way, it is possible to obtain, for example, neurons that excrete dopamine, the destruction of which is the cause of Parkinson's disease.
The presented study illustrates the fundamental possibility of converting cells of one type into cells of another type without prior transformation of the original type of cells into stem cells. Previously, scientists were able to transform skin cells into neurons and one type of pancreatic cell into another without first converting skin cells into stem cells.
The work of the Goetz and Berninger group complements the method of transformation of skin cells into neurons, representing a new strategy for obtaining neurons without involving stem cells. For the development of individual human cells “in vitro” (outside the body) for the purpose of subsequent transplantation, skin cells are more convenient, since they are easy to obtain. The presented results of astrocyte transformation into neurons imply the possibility of obtaining neurons using this technique “in vivo” - directly in the patient's brain, without the need for pre-growing the necessary cells in Petri dishes and subsequent transplantation.
The next stage of the work will be to find out whether the neurons reprogrammed from astrocytes in the patient's brain will survive and whether they will be fully functional.
Fortunately, the brain is an inexhaustible source of astrocytes. Astrocytes begin to multiply with brain injuries, similar to how skin cells regenerate with cuts and scratches. After the publication of the article, the authors managed to obtain neurons from astrocytes grown after injury in the brains of adult mice.
Daria Chervyakova
Portal "Eternal youth" http://vechnayamolodost.ru based on Technology Review: Helping the Brain to Help Itself20.05.2010