Ageing is the largest risk factor for many chronic diseases. Studies of heterochronic parabiosis, substantiated by blood exchange and old plasma dilution, show that old-age-related factors are systemically propagated and have pro-geronic effects in young mice. However, the underlying mechanisms how bloodborne factors promote ageing remain largely unknown. Here, using heterochronic blood exchange in male mice, we show that aged mouse blood induces cell and tissue senescence in young animals after one single exchange. This induction of senescence is abrogated if old animals are treated with senolytic drugs before blood exchange, therefore attenuating the pro-geronic influence of old blood on young mice. Hence, cellular senescence is neither simply a response to stress and damage that increases with age, nor a chronological cell-intrinsic phenomenon. Instead, senescence quickly and robustly spreads to young mice from old blood. Clearing senescence cells that accumulate with age rejuvenates old circulating blood and improves the health of multiple tissues.

衰老是许多慢性疾病的最大危险因素。通过血液交换和老年血浆稀释证实的异时性联体共生研究表明，老年相关因素在年轻小鼠中系统性传播并具有促老年效应。然而，血源性因素促进衰老的潜在机制仍然很大程度上未知。在这里，我们利用雄性小鼠的异时性血液交换，发现老年小鼠的血液在一次交换后会诱导年轻动物的细胞和组织衰老。如果在血液交换前用抗衰老药物治疗老年动物，这种衰老的诱导作用就会被消除，从而减弱老年血液对年轻小鼠的促衰老影响。因此，细胞衰老既不是简单地对随年龄增长而增加的压力和损伤的反应，也不是按时间顺序排列的细胞固有现象。相反，衰老现象从衰老的血液中迅速而有力地传播到年轻小鼠身上。清除随着年龄的增长而积累的衰老细胞，可以使旧的循环血液恢复活力，并改善多个组织的健康。