Transdifferentiation of reactive astrocytes into functional neurons causes motor recovery after spinal cord injury

摘要

Transdifferentiation of reactive astrocytes into functional neurons causes motor recovery after spinal cord injury Transdifferentiation is a promising therapy for replacing dead neurons in spinal cord injury (SCI) where scar-forming reactive astrocytes proliferate robustly, allowing themselves as a prime tar- get for reprogramming into neurons. In this study, we directly reprogrammed reactive astrocytes into functional neurons with particular molecular tools, comprising a double-floxed transcrip- tion factor, neurogenin-2 (Ngn2) and a split-Cre under two different promoters for reactive astrocytes specific gene expression. In the injured mouse brain, over 60% of virally-transfected reactive astro- cytes transdifferentiated into NeuN positive neuron-like cells with robust action potential via expressing Ngn2. In the AAV-EF1a-df- Ngn2-IRES-GFP with split cre infected SCI (SCI/Ngn2) group, motor impairment was significantly recovered to 34% of the normal level in Basso mouse score (BMS), consistent with showing action poten- tial. Ngn2-expressing cells colocalize with neuronal markers but not with BrdU, indicating that they are originated not from cell- division, but from the cell-fate switch. These results show that reactive astrocytes directly convert to neurons without risk of tumorigenesis caused by stemness of infected cells. Our study pro- poses the transdifferentiation of reactive astrocytes into functional neurons as a next-generation therapeutic approach for patients suffering from spinal cord injury.