Senescent Characteristics of Human Corneal Endothelial Cells upon Ultraviolet-A Exposure
Purpose: The objective of this study was to investigate the senescent phenotypes of human corneal endothelial cells (hCEnCs) upon treatment with ultraviolet (UV)-A. Methods: We assessed cell morphology, senescence-associated ß-galactosidase (SA-ß-gal) activity, cell proliferation and expression of senescence markers (p16 and p21) in hCEnCs exposed to UV-A radiation, and senescent hCEnCs induced by ionizing radiation (IR) were used as positive controls.  We performed RNA sequencing and proteomics analysis to compare gene and protein expression profiles between UV-A- and IR-induced senescent hCEnCs, and we also compared the results to non-senescent hCEnCs. Results: Cells exposed to 5 J/cm2 of UV-A or to IR exhibited typical senescent phenotypes, including enlargement, increased SA-ß-gal activity, decreased cell proliferation and elevated expression of p16 and p21.  RNA-Seq analysis revealed that 83.9% of the genes significantly upregulated and 82.6% of the genes significantly downregulated in UV-A-induced senescent hCEnCs overlapped with the genes regulated in IR-induced senescent hCEnCs.  Proteomics also revealed that 93.8% of the proteins significantly upregulated in UV-A-induced senescent hCEnCs overlapped with those induced by IR.  In proteomics analyses, senescent hCEnCs induced by UV-A exhibited elevated expression levels of several factors part of the senescence-associated secretory phenotype. Conclusion: In this study, where senescence was induced by UV-A, a more physiological stress for hCEnCs compared to IR, we determined that UV-A modulated the expression of many genes and proteins typically altered upon IR treatment, a more conventional method of senescence induction, even though UV-A also modulated specific pathways unrelated to IR. Overall design: To investigate the gene profiles of senescent corneal endothelial cells by UVA and X-ray exposure. Expression profiling by high throughput sequencing. Four biological replicates were analyzed for each of 3 conditions (untreated, irradiation, UVA exposure)