Purpose: The pathogenesis of keratoconus (KC) is multifactorial and associated with oxidative stress and subsequent DNA damage. The aim of this study was to investigate differences in DNA damage and replicative stress in patients with KC, and in both healthy and diseased controls. Methods: Sixty-four corneal buttons were obtained from 27 patients with KC after corneal transplant surgery, 21 patients with a decompensated graft (DG), and 16 healthy controls (HC). The amount of intact Alu elements per genome copy as measured by qPCR was used to quantify intact DNA. Telomere length was measured as a proxy for replicative stress. In addition, telomerase reverse transcriptase (hTERT) gene expression level was assessed. Results: Mean (±SD) DNA damage was similar between the KC (5.56 ±14.08), DG (3.16 ±8.22), and HC (3.51 ±6.66) groups (P=0.807). No associations were found between DNA damage and patient age (P=0.523), atopic constitution (P=0.240), or contact lens wear (P=0.393). Telomere length differed (P=0.034), most notably in the KC group, and hTERT was not detected in any corneal sample. Three cross-linked (CXL) KC corneas did not contain significant more DNA damage (2.6x, P = 0.750). Conclusions: Based on these findings, differences in actual corneal DNA damage in KC could not be identified, and the longer telomere length in KC did not support replicative stress as a major etiological factor in the pathogenesis of KC. Future longitudinal investigations on KC etiology should assess progressive early cases to better comprehend the cellular and molecular processes preceding the archetypical morphological changes.

Quantification of double stranded DNA breaks and telomere length as proxies for corneal damage and replicative stress in 64 human keratoconus corneas The role of DNA damage in the development of keratoconus