Fig. 3.

The concept of differential ageing can be applied on an increasingly smaller scale. Differential ageing has been evidenced on an organism level, where an individual can biologically age better or worse than is expected for their chronological age. As well as different individuals ageing differently, ageing affects the function of various organ systems heterogeneously. Moreover, similar principles can be applied to nervous system regions, individual cells and even components within a single cell, which might age disproportionately to their counterparts. Some examples of differential ageing at each scale are provided above, which might have important consequences for age-related disease research. The experimental tractability of analysing nervous system tissue, cellular and molecular differential/delta ageing, as well as its possible future implications therapeutically, are reviewed in the discussion section. GM = grey matter; SpC = spinal cord. Templates used/adapted to create this figure are freely available from Servier Medical Art (https://smart.servier.com/). (References used to create this figure: D’Angelo et al., 2009; Fjell et al., 2013; Jernigan et al., 2001; Khan et al., 2017; Maxwell et al., 2018; Rhinn and Abeliovich, 2017; Soreq et al., 2017; Stauch et al., 2014).