A guide to assessing cellular senescence in vitro and in vivo

Abstract

Cellular senescence is a physiological mechanism whereby a proliferating cell undergoes a stable cell cycle arrest upon damage or stress and elicits a secretory phenotype. This highly dynamic and regulated cellular state plays beneficial roles in physiology, such as during embryonic development and wound healing, but it can also result in antagonistic effects in age-related pathologies, degenerative disorders, ageing and cancer. In an effort to better identify this complex state, and given that a universal marker has yet to be identified, a general set of hallmarks describing senescence has been established. However, as the senescent programme becomes more defined, further complexities, including phenotype heterogeneity, have emerged. This significantly complicates the recognition and evaluation of cellular senescence, especially within complex tissues and living organisms. To address these challenges, substantial efforts are currently being made towards the discovery of novel and more specific biomarkers, optimized combinatorial strategies and the development of emerging detection techniques. Here, we compile such advances and present a multifactorial guide to identify and assess cellular senescence in cell cultures, tissues and living organisms. The reliable assessment and identification of senescence is not only crucial for better understanding its underlying biology, but also imperative for the development of diagnostic and therapeutic strategies aimed at targeting senescence in the clinic.

Cellular Senescence in Human Aldosterone-Producing Adrenocortical Cells and Related Disorders

“…In addition, in order to further clarify the association between the status of DNA damage and the senescent status, we used γH2AX as a biomarker of DNA double-strand breaks caused by genotoxic agents such as UV or radiation [ 36 ]. DNA damage and replicative alteration could be a part of a senescent phenotype, although these phenotypes were reported to be not necessarily equivalent [ 37 , 38 ]. In this study, γH2AX immunolocalization was not concordant with those of the cell senescence biomarkers studied, including p16 and p21.…”

LEDGF/p75 Is Required for an Efficient DNA Damage Response

“…Finally, increased phosphorylation of H2AX can be also caused in response to cell cycle progression during G2/M phase entry [ 36 ]. Furthermore, elevated γH2AX and G2/M arrest could also be indicators for senescence [ 37 , 38 ]. Therefore, a potential cell cycle arrest in LEDGF KO cells was investigated, especially because LEDGF knockdown has been previously shown to induce cell cycle arrest in the S/G2 phase and increased apoptosis in prostate cancer cells [ 10 ].…”

The Emergence of Senescent Surface Biomarkers as Senotherapeutic Targets

“…Proliferation assays and specific markers of proliferation (e.g., the nuclear marker of proliferation Ki67) are commonly used to confirm the reduction in cell proliferation associated with senescence. Additionally, flow cytometry can be used to detect the cell cycle distribution and the specific phase in which senescent cells are arrested [ 19 ].…”