Quantitative analysis of radiation-induced senescence in endothelial cells

Epidemiological studies have shown that ionizing radiation is associated with an elevated risk of cardiovascular diseases (CVD). Endothelial cells, lining the blood vessels, are believed to be the primary target of ionizing radiation with regard to the development of CVD. Dysfunction, apoptosis or premature senescence of endothelial cells can trigger atherosclerosis, the main cause of CVD worldwide. Three different assays were used to detect senescence in immortalized coronary artery endothelial cells (TICAE) after irradiation. All the assays are based on the detection of β-galactosidase activity at pH 6, which is a key feature of senescent cells. Using the standard senescence-associated β-galactosidase (SA β-gal) assay, we found that irradiation (10 Gy) significantly increases the amount of senescent cells but only on day 1 post-irradiation (PI). Additionally, we found that there was a remarkably high percentage of senescent cells in the control group (0 Gy). Using the colorimetric CPRG and fluorometric MUG assays, we found higher SA β-gal activities in the control group compared to the irradiated group. Thus, for future experiments, it will be crucial to further optimize the assays and consider a different cell model, like cell cultures at a lower passage number or primary endothelial cells, to limit the amount of senescent cells in the control group.