Rejuvenation of Senescent Cells, In Vitro and In Vivo, by Low-Frequency Ultrasound

Abstract

The presence of senescent cells causes age-related pathologies since their removal by genetic or pharmacological means, as well as possibly by exercise, improves outcomes in animal models. An alternative to depleting such cells would be to rejuvenate them to promote their return to a replicative state. Here we report that treatment of non-growing senescent cells with low-frequency ultrasound (LFU) rejuvenates the cells for growth. Notably, there are 15 characteristics of senescent cells that are reversed by LFU, including senescence-associated secretory phenotype (SASP) plus decreased cell and organelle motility. There is also inhibition of β-galactosidase, p21, and p16 expression, telomere length is increased, while nuclear 5mC, H3K9me3, γH2AX, nuclear p53, ROS, and mitoSox levels are all restored to normal levels. Mechanistically, LFU causes Ca²⁺ entry and increased actin dynamics that precede dramatic increases in autophagy and an inhibition of mTORC1 signaling plus movement of Sirtuin1 from the nucleus to the cytoplasm. Repeated LFU treatments enable the expansion of primary cells and stem cells beyond normal replicative limits without altering phenotype. The rejuvenation process is enhanced by co-treatment with cytochalasin D, rapamycin, or Rho kinase inhibition but is inhibited by blocking Sirtuin1 or Piezo1 activity. Optimized LFU treatment parameters increased mouse lifespan and healthspan. These results indicate that mechanically induced pressure waves alone can reverse senescence and aging effects at the cellular and organismal level, providing a non-pharmacological way to treat the effects of aging.