The bright and dark side of extracellular vesicles in the senescence-associated secretory phenotype.

Senescence is a state of proliferative arrest which has been described as a protective mechanism against the malignant transformation of cells. However, senescent cells have also been demonstrated to accumulate with age and to contribute to a variety of age-related pathologies. These pathological effects have been attributed to the acquisition of an enhanced secretory profile geared towards inflammatory molecules and tissue remodelling agents - known as the senescence-associated secretory phenotype (SASP). Whilst the SASP has long been considered to be comprised predominantly of soluble mediators, growing evidence has recently emerged for the role of extracellular vesicles (EVs) as key players within the secretome of senescent cells. This review is intended to consolidate recent evidence for the roles of senescent cell-derived EVs to both the beneficial (Bright) and detrimental (Dark) effects of the SASP.