The existence of senescent cells in conjunctival epithelium from elderly individuals

• Published in: Japanese journal of ophthalmology 2024-03, Vol.68 (2), p.157-165
• Main Authors: Tomioka, Yasufumi, Kitazawa, Koji, Numa, Kohsaku, Hughes, Jun-Wei B., Yokoi, Norihiko, Sotozono, Chie
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Aging; Biomarkers; Cellular Senescence; Conjunctiva; Cyclin-Dependent Kinase Inhibitor p16 - analysis; Cyclin-Dependent Kinase Inhibitor p16 - genetics; Cyclin-Dependent Kinase Inhibitor p16 - metabolism; Cyclin-dependent kinase inhibitor p21; Epithelium; Epithelium - chemistry; Epithelium - metabolism; Female; Geriatrics; Humans; INK4a protein; Ki-67 Antigen; Laboratory Investigation; Male; Medicine; Medicine & Public Health; Men; Microenvironments; Middle age; Middle Aged; Older people; Ophthalmology; p16 Protein; Senescence; Stem cells; Women; Zonula occludens-1 protein
• ISSN: 0021-5155; 1613-2246
• DOI: 10.1007/s10384-023-01047-x

Purpose The ocular surface microenvironment changes with aging. However, it remains unclear if cellular senescence influences the ocular surface. We investigated the presence of p16 INK4a -expressing senescent cells in healthy human conjunctiva. Study design Clinical and experimental. Methods Healthy conjunctival tissue samples were obtained from middle-aged and elderly subjects. RT-qPCR was performed to assess the expression of senescence markers CDKN2A (p16 INK4a ) and CDKN1A (p21 CIP1/WAF1 ) and immunostaining was performed to examine the expression of the senescence marker p16 INK4a , stem cell markers Ki67 and p63, tight-junction marker ZO-1. Results Our study involved 19 conjunctival tissue samples (10 elderly and 9 middle-aged), mean age [elderly: 75.8 ± 3.7 years (72–81), middle-aged: 52.7 ± 7 years (38–59)], sex (elderly: 3 men, 7 women; middle-aged: 3 men, 6 women). The expression of p16 INK4a was significantly increased at the RNA level in the elderly compared to middle-aged ( p < 0.05). Positivity rate of p16 INK4a was significantly elevated in the elderly (15.0 ± 7.8%) compared to middle-aged (0.2 ± 0.6%) ( p < 0.05). Positivity rate of Ki67and p63 was significantly reduced in the elderly (1.7 ± 1.7% and 16.5 ± 9.5%) compared to middle-aged (3.9 ± 1.8% and 24.7 ± 5.7%) ( p < 0.05). ZO-1 expression was reduced in tissue samples showing p16 INK4a -positivity but retained in tissue samples in which p16 INK4a was undetectable. Conclusions Senescent cells accumulate with age in the conjunctival epithelium, accompanied by a decrease in Ki67, p63 and ZO-1 expressing cells.