Dr. Hagen Huttner and Prof. Dr. Stefan Schwab from the Department of Neurology at the University Hospital of Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and Swedish colleagues from the Karolinska Institute have demonstrated that cells of the cortex cannot regenerate as originally assumed. With their method they disproved results from animal experiments on rodents. For their studies, they used the fact that a radioactive carbon isotope released by nuclear bomb tests during the Cold War had been incorporated into the genome of human nerve cells, remaining stable there for a very long time. These 14C isotopes can be measured.

The scientists first examined DNA repair mechanisms that are activated after tissue damage. In order to do so, they isolated nuclei from the cortical tissue of healthy subjects and stroke patients using flow cytometry. The researchers could not confirm that the neurons that survived in the cortex showed significant genomic rearrangements or translocations as would be expected in the case of repair processes.

They then determined the age of the cells after the stroke via the amount of 14C isotopes in the genome. The concentration of 14C corresponded to the time of birth of patients in the 14C concentration in the air. However, the concentration in the tissue damaged by stroke corresponded approximately to the concentration of control tissues from healthy subjects. That showed them that strokes do not lead to a formation of new neurons, as the isotopic amount would otherwise have decreased. Backdating showed that the age of the surviving cells corresponded to the age of the stroke patient themselves.

Earlier results from experiments on animals in which strokes had been artificially induces had led researchers to mistakenly assume that the human cerebral can form new cells after strokes (e.g. Arvidsson et al 2002, Jin et al 2006) and to infer a potential for regeneration.

Source (in German): http://idw-online.de/pages/de/news583370

Original publications:
Hagen B Huttner, Olaf Bergmann, Mehran Salehpour, Attila Rácz, Jemal Tatarishvili, Emma Lindgren, Tamás Csonka, László Csiba, Tibor Hortobágyi, Gábor Méhes, Elisabet Englund, Beata Werne Solnestam, Sofia Zdunek, Christian band Mountain, Lena Ström, Patrik Ståhl, Benjamin Sigurgeirsson, Andreas Dahl, Stefan Schwab, Göran Possnert, Samuel Bernard, Zaal Kokaia, Olle Lindvall, Joakim Lundeberg & Jonas Frisén (2014): The age and genomic integrity of neurons after cortical stroke in humans. Nature Neuroscience, doi: 10.1038/nn.3706

Arvidsson A, Collin T, Kirik, D, Kokaia, Z & Lindvall, O (2002): Neuronal replacement from endogenous precursor in the adult brain after stroke. Nature Medicine 8/9: 963-970.

Jin, K, Wang, X, Xie, L, Ou Mao, X, Zhu, W, Wang, Y, Shen, J, Mao Y, Banwait, S & Greenberg, DA (2006): Evidence for stroke-induced neurogenesis in the human brain. PNAS 103/35: 13198-13202.