Prospects for genuine regenerative medicine for the brain are opening up. Neurobiology has overturned its own dogmas over the past decade.
“The brain is able to produce new neurons throughout life, to repair a lesion or to cope with a new influx of information ”. Pierre-Marie Lledo, head of the “Perception and memory” unit at the Institut Pasteur, can now say so. And in one sentence, it sums up the revolution of the last ten years on the brain. A revolution that goes against the dogma of fixing the number of neurons at birth. Research had already established that all organs in the body have a potential for regeneration, especially through stem cells, but the brain seemed doomed to age inexorably from the outset of adolescence, until a Swedish researcher, Peter Eriksson, in 1998 found newly formed neurons in the hippocampus, the area of the brain that manages spatial memory. In 2003, Pierre-Marie Lledo’s team discovered in turn that new neurons were produced in the very heart of the brain and were moving very quickly towards the olfactory bulb. “The 30,000 new nerve cells produced daily by a normal mouse brain circulate at the incredible speed of 150 µm / hour, more than ten times faster than in the developing brain of the embryo, which is far less crowded than a adult brain ”he emphasizes (see video opposite). The same team discovered in 2004 tenascin, a molecule that attracts these new neurons to their final destination and established in 2008 that new neurons can in fact be produced throughout the brain and not from a single source. A concept that once again revolutionizes neurobiology. Why neural transplants are ineffectiveThe new neurons are also perfectly functional and are produced in greater quantities when the brain needs them, as one of the experiments of Pierre-Marie Lledo’s team was able to demonstrate. ” By subjecting mice to ever new smells every day for 40 days, we were able to extend their olfactory memory from 30 minutes to 4 hours thanks to the doubling of the number of new neurons produced. “. The latest work by this team, which should be published in Nature Neuroscience, shows that newly produced neurons are able to respond more effectively to stimulation. However, they are naturally destroyed if they are not useful for keeping information. Questions toto Dr Harold Cremer, research director at CNRS, head of the “Molecular control of neurogenesis” team at the Marseille Luminy Institute for Developmental Biology. Study the factors that influence the fate of neuronsWhat is the fate of the new neurons in the brain? Dr Harold Cremer Newly generated neurons in the adult brain in an ectopic position of the brain, such as the striatum, have been shown to become glial cells. It is possible, to explain that the brain is refractory to new neurons, that it is less good to have these new neurons than not to have them in a brain affected by a disease. How to promote their integration? Interview with PL |
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