Characterizing the SASP-Dependent Paracrine Spreading of Senescence Between Human Brain Cell Types

One of the defining phenotypes of a senescent cell is the senescence-associated secretory phenotype (SASP), which can propagate senescence in neighboring cells both <i>in vitro</i> and <i>in vivo</i>. Importantly, this paracrine spreading of senescence can act in a cell non-autonomous manner, influencing neighboring cell populations and contributing to immune cell recruitment. As cellular senescence has recently been linked to both age-related neurodegenerative phenotypes and local inflammation and is more clearly defined across brain cell types in a cell-type-dependent manner, an urgent question remains regarding how a cell-type-specific paracrine spreading of senescence occurs in the brain. Here, we set out to profile the cell-type-specific features of the SASP and characterize the directionality of paracrine senescence-spreading between major brain cell types. Through this analysis, we identified key SASP ligand-receptor pairs involved in this paracrine dissemination. Targeting these factors with specific inhibitors, we prevented the paracrine spreading of senescence in a brain cell-type-dependent manner. Taken together, we identified specific SASP targets for therapeutic intervention in the context of human brain cells and thereby informed the SASP-dependent reaction of immune cells and age-related tissue dysfunction across both normal aging and models of neurodegenerative disease.