Emerging interactions between circadian rhythms and extracellular vesicles.

Circadian rhythms are present across species, tuning internal processes to daily changes in the environment. Driven by genetically encoded circadian clocks present throughout the body, and modulated by external inputs, the circadian system is a key player in metabolic control. However, the molecular mediators underlying coordination between cells and tissues are not well known. Extracellular vesicles (EVs) have emerged over recent years as important players in cell-cell and organ-organ communication, however the influence of circadian rhythms on EVs is not yet understood. Research into this area is still scarce, yet already offers glimpses into the potential impact of circadian rhythms on EV biology. In this review, recent discoveries that reveal, directly or indirectly, a potential role for circadian rhythms in EV abundance, properties, cargo and signalling functions are first discussed. Next, the feedback of EV signalling on circadian clocks is considered. Last, unanswered questions regarding the interaction between circadian rhythms and EVs are examined alongside potential approaches to address them. Overall, the circadian impact on EV signalling is an exciting yet understudied aspect that warrants further investigation.