Comprehensive single cell profiling of ageing glial cells reveals impaired Wnt signalling and Jun transcription factors regulating cortical astrocytes

Understanding age-related cellular dysfunction in the brain is essential for developing strategies to promote healthy ageing. Towards this aim, we took advantage of a previously established 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, high-lighting 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 downstream 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. <h4>Main points</h4> Transcriptomic analysis uncovers cell type–specific impact of ageing in the cortical grey matter, including altered intercellular communication networks. Multiomic profiling identifies dysregulated Wnt signalling in ageing cortical astrocytes. Ageing astrocytes exhibit upregulation of the Wnt signalling regulators Maml2 and Daam2, accompanied by downregulation of the AP-1 transcriptional complex component JunD. Overexpression of JunD increases proliferation after mild injury in aged astrocytes.