Abnormal Differentiation in Senescent Human Conjunctival Epithelial Cells

Abstract

Purpose : X-irradiated senescent human conjunctival epithelial cells (hCjCs) exhibited the increased expression of genes associated with keratinization was reported (Kitazawa et al. Aging. 2023). The purpose of this study is to investigate the characteristics of ultraviolet (UV)-A induced senescent hCjCs and examine the effects of nicotinamide (NAM) for the prevention of abnormal cell differentiation.

Methods : Primary hCjCs were obtained from donor eyes. The hCjCs were exposed to 15J/cm² UV-A and were cultured to undergo senescent. Cell proliferation was assessed with incorporating 5-ethynyl-2'-deoxyuridine (EdU). Cellular senescence was assessed by cell morphology and senescent-related genes (p16 and p21). The cellular differentiation of hCjCs was examined with a keratinization marker (K10). The hCjCs were treated with NAM at 4 mM on the same day of UV-A exposure and were cultured in the presence of NAM for 7 days.

Results : UV-A radiated hCjCs displayed more elongated and flattened than non-UV-A radiated cells over time. On day 7, Ed-U incorporation was significantly lower in UV-A radiated hCjCs than non-UV-A radiated cells (p < 0.05). In addition, senescent-related genes (p16 and p21) and a keratinization marker (K10) were increased in the UV-A radiated hCjCs (p< 0.05). NAM supplementation showed improved Ed-U incorporation compared to non-treated UV-A radiated hCjCs (p = 0.07) and decreased expression of senescent-related genes (p16 and p21) and a keratinization marker (K10) (p < 0.05).

Conclusions : UV-A radiated hCjCs exhibited increased keratinization marker in addition to elevated senescent-related genes. The supplementation of NAM suppressed elevated genes identified in UV-A radiated hCjCs and improved cell proliferation.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.