An increase in ROS is required for repair of the neonatal cerebellum

The neonatal mouse cerebellum shows remarkable regenerative potential upon injury at birth. Nestin-expressing progenitors (NEPs) undergo adaptive reprogramming to replenish the lost granule cell progenitors. Here, we investigate how the injury microenvironment affects NEPs’ regenerative potential and adaptive reprogramming. Single cell transcriptomic and bulk chromatin accessibility analyses of the NEPs from control and injured neonatal cerebella show a temporary increase in mechanisms involved in the response to reactive oxygen species (ROS), a known damage-associated molecular pattern. Analysis of ROS levels also confirms a temporary increase in ROS levels upon injury at postanal day 1, 1-2 days after injury, overlapping with the induction in cell death in the cerebellum. Using a transgenic mouse model that overexpresses mitochondrial catalase (mCAT) and reduces ROS levels globally, we showed that the regenerative potential of NEPs decreases upon injury to the granule cell progenitors at birth and the repair is impaired. Finally, we demonstrated that microglia are involved in adaptive reprogramming by regulating NEP migration to the external granule layer, the site of injury. Collectively, our results highlight that the changes in the tissue microenvironment such as an increase in the ROS levels are required for the adaptative reprogramming of NEPs upon injury to the granule cell progenitors at birth, highlighting the instructive roles of microenvironmental signals during regeneration in the neonatal brain.