Tear proteomic analysis in keratoconus patients and potential biomarkers: a case-control study

Keratoconus is a corneal ectasia whose pathophysiological mechanisms, including biomolecular alterations and genetic influences, remain poorly understood. Recent studies have shown altered cytokine levels, increased proteinase activity, and other potential mediators in the tear film and corneal tissue, highlighting a possible involvement of inflammatory pathways in the pathophysiology of keratoconus. This observational study aims to characterize the tear proteome of keratoconus patients and compare it to a control group, reporting potential disease biomarkers in the tear film. 23 keratoconus patients were selected at the Cornea and External Diseases Outpatient Clinic of the Clinics Hospital of UNICAMP. The control group consisted of 17 age- and sex-matched participants. All study subjects underwent corneal tomography (Pentacam). Tear film samples were collected and sent for proteomic evaluation by mass spectrometry at the National Biosciences Laboratory (LNBio). After quantification, univariate and multivariate statistical analyses were performed. A total of 353 proteins were identified and quantified, of which 25 showed statistical differences in the univariate analysis (t-test), and 19 were selected in the multivariate analysis (PLS-DA). There was an overlap of 7 proteins identified in both uni- and multivariate analyses: chitinase-3-like protein 2, prosaposin, zymogen granule protein 16 homolog B, procollagen-lysine,2-oxoglutarate 5-dioxygenase 1, secretoglobin family 1D member 1, albumin, and Ig kappa chain V-I region. Thirty-seven proteins showed statistically significant variation between the keratoconus and control groups. Proteomic analysis revealed differentially expressed proteins in the tear film of keratoconus patients. We report the identified proteomic profile, which includes potential biomarkers that may help elucidate the disease's pathophysiology.