p16INK4a and γ-H2AX as Biomarkers of Senescence in Skin Tissue: A Cadaveric Cross-sectional Study at a Tertiary Care Centre in Punjab, India

Introduction: Baseline expression of p16INK4a characterises cellular senescence. Similarly, the measurement of γ-GammaH2AX (γ-H2AX) foci levels in cells provides a reliable method for quantification of Deoxyribonucleic Acid (DNA) damage. Aim: To explore the role of p16INK4a and γ-H2AX as biomarkers of senescence in skin tissue. Materials and Methods: This was a cross-sectional study conducted in the Department of Anatomy, PGIMER, Chandigarh, Punjab, India from June 2022 to January 2023. Skin tissue was obtained from 30 cadavers, aged 20-90 years, from the anterior abdominal wall. The time duration of sample collection after death varied from six hours to 12 hours. Samples were divided into two groups: Group-I 70 years, with n=15 in each group. The relative change in the expression pattern of p16INK4a and γH2AX markers, as well as the microstructure of the skin (thickness of epidermis and dermis, distribution of collagen I/II/III fibres, architecture of sebaceous glands), were statistically analysed using an unpaired t-test. Results: Intense staining was observed with p16INK4a in Group-II, showing positivity in 60.75% of the cells, while Group-I depicted a weak staining pattern (15%). On immunostaining with γ-H2AX, only Group-II cells showed intense positivity (45%). Significant differences were observed in the epidermal and dermal thickness: Group-I (165.5267±37.73 μm; 2394.6±874.13 μm); Group-II (54.6±22.79 μm; 566.67±242.23 μm), and collagen Type-II/III fibres were found predominantly in aging skin tissue. Conclusion: The present study provides comprehensive data regarding age-associated changes between p16INK4a, γ-H2AX, and skin microstructure, which result in decreased repair and regenerative capacity of skin tissue and various age-related skin diseases.