Ependymal cells are the "source of youth" of the brain
Researchers at Duke University, working under the guidance of associate Professor Chay Kuo, identified the "source of youth" of the mouse brain, providing the formation of new neurons. They believe that there is a similar system in the human brain. Its existence explains the inability of neural tissue stem cells to independently transform into neurons in the laboratory.
Currently, all attempts to cultivate nerve stem cells in order to obtain neurons have ended, as a rule, with the appearance of auxiliary cells of nervous tissue – astrocytes.
It turned out that the neurogenicity (the ability to form new neurons) of stem cells in a living organism is supported by cellular structures formed by ependymal cells similar to epithelial cells. (Ependyma is a single–layer lining of the central cavities of the brain and spinal cord).
Even in prenatal development, stellate glial progenitor cells give rise to adult neural stem cells and their "ugly" counterparts - ependymal cells, the surface of which is covered with long movable hairs-cilia. The researchers decided to study these cells, since in an adult body they are stored exclusively in the lateral ventricles of the brain – regions populated also by adult stem cells of nervous tissue.
Experiments have shown that under the influence of the transcription factor Foxj1, which belongs to the class of proteins that ensure the "on/off" of gene expression, ependymal cells change shape and form cellular structures around stem cells. In this case, the lateral sections of the membrane of mature ependymal cells are stretched and connected to each other like the teeth of a mechanism or fingers.
Scientists have found that these transformations aimed at providing physical support to tender stem cells are caused by the launch of the synthesis of the structural protein ankyrin-3 (Ankyrin 3). Apparently, the absence of signals generated by structural support from ependymal cells is the reason for the inability of nerve stem cells to differentiate into neurons "in captivity".
In the future, the researchers plan to continue their work on studying the niche formed by ependymal cells to direct the differentiation of stem cells in the right direction. They believe that over time, this will allow the development of new therapeutic strategies for using human stem cells to replace dead neurons.
The article by Patricia Paez-Gonzalez et al. Ank3-Dependent SVZ Niche Assembly Is Required for the Continued Production of New Neurons was published on July 14 in the on-line version of the journal Neuron.
Evgeniya Ryabtseva
Portal "Eternal youth" www.vechnayamolodost.ru based on Duke Medicine: Researchers demystify a fountain of youth in the adult brain.
15.07.2011