Hennes, M.; Thorwirth, M.; Lao, C. L.; Stogsdill, J. A.; Arlotta, P.; Fischer-Sternjak, J.; Richter, M. L.; Goetz, M.

Understanding age-related cellular dysfunction in the brain is essential for developing strate-gies to promote healthy ageing. Towards this aim, we took advantage of a previously estab-lished mild dissociation method to profile cells in the cerebral cortex grey matter of adult and aged mice. This revealed glial cells with largely up-regulated and other glia and neurons with largely down-regulated gene expression upon ageing. Astrocytes were involved in increased interactions with microglia and decreased interaction with neurons, highlighting potent age-induced changes in their regulatory roles. Single cell RNA-seq and single nuclei multiome analysis of astrocytes uncovered down-regulation of Wnt-signalling with increased expression of its inhibitors and reduced RNA and protein levels of its effectors JunB/D, acting down-stream of Wnt signalling in ageing. This was confirmed by RNA-scope and immunostainings, as well as in human data. Notably, injection of JunD-expressing viral vectors in astrocytes increased their proliferation and HMGB1 levels in the aged brain, indicative of a more youthful astrocyte state.