Insights into the Interplay Between Irreversible Growth Arrest and Inflammation During Cellular Senescence - Genome Dynamics in Neuroscience and Aging

Caroline Gleason ¹ Mary Klein ¹ Liang Li ² Marta Kovatcheva ³ Nguan Soon Tan ⁴ Andrew Koff ⁵

¹Louis V. Gerstner Graduate School of Biomedical Sciences, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, USA
²Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, China
³Institute for Research in Biomedicine, The Barcelona Institute of Science and Technology, Spain
⁴School of Biological Sciences, Nanyang Technological University, Singapore
⁵Program in Molecular Biology, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, USA

Cellular senescence is involved in many physiological and pathological processes, including wound healing, stem cell exhaustion, tumor suppression, and aging. Despite the established link between senescence and aging, the sensors, transducers, and effectors that underlie aging-associated senescence at the genetic or molecular level remain elusive. We hypothesized that the programs involved in cell cycle exit are likely to be cell type- and signal-specific, but that once a cell has committed to senescence, the effectors involved might be more broadly conserved. Using therapy-induced senescence as a model, we set out to identify these effectors by engineering a cell line to progress synchronously from quiescence into senescence using CDK4/6 inhibitors.

We were able to observe robust temporal separation between the appearance of different senescence markers, such as increased ATRX foci formation (day 3), SA-β-gal expression (day 5), irreversible growth arrest (day 14), and the elaboration of three distinct SASP effector programs (day 14, 21, and 28). Using this system, we identified the protein ANGPTL4 as a putative regulator of irreversible growth arrest and the later expression of other SASP transcripts related to inflammation. To determine if the role of ANGPTL4 was conserved in other senescence contexts, as we hypothesized, we turned to a model of skin wounding in mice. DeMaria and Campisi have previously shown that senescent cells surrounding a wound stimulate healing; within this model, we found that ANGPTL4 was also necessary for timely wound healing, and that loss of ANGPTL4 led to decreased immune cell recruitment.

Our work establishes a link between irreversible growth arrest and the onset of the inflammatory SASP program in two different senescence systems. By extension, it suggests that manipulation of ANGPTL4 signaling pathways might also affect the age-associated appearance of senescent cells or the inflammatory contributions such cells make.