Heterochronic blood exchange (HBE) has demonstrated that circulating factors restore youthful features to aged tissues. However, the systemic mediators of those rejuvenating effects remain poorly defined. We show here that the beneficial effect of young blood on aged muscle regeneration was diminished when serum was depleted of extracellular vesicles (EVs). Whereas EVs from young animals rejuvenate aged cell bioenergetics and skeletal muscle regeneration, aging shifts EV subpopulation heterogeneity and compromises downstream benefits on recipient cells. Machine learning classifiers revealed that aging shifts the nucleic acid, but not protein, fingerprint of circulating EVs. Alterations in subpopulation heterogeneity were accompanied by declines in transcript levels of the prolongevity protein α-Klotho (Klotho), and injection of EVs improved muscle regeneration in a Klotho mRNA-dependent manner. These studies demonstrate that EVs play a key role in the rejuvenating effects of HBE and that Klotho transcripts within EVs phenocopy the effects of young serum on aged skeletal muscle.

Nat Aging (2021). https://doi.org/10.1038/s43587-021-00143-2

血液中流通的细胞外囊泡（extracellular vesicles）会携带「长寿蛋白」的合成指令，送往身体各处。而衰老则会改变这些囊泡的特性，最终损害身体的自我修复能力。