Glaucoma Biomarker Discovery

Abstract

Purpose:: To develop a blood test for predicting susceptibility to primary open angle glaucoma (POAG) and for monitoring the efficacy of POAG therapeutics.

Methods:: Blood was collected from clinically documented POAG and age-matched normal control (CTRL) donors at the Cole Eye Institute, Cleveland Clinic, Louis Stokes Cleveland VA Medical Center and at the Aravind Eye Hospital, Madurai, India. Plasma samples were fractionated on reverse phase-coated magnetic beads and analyzed by MALDI TOF/TOF mass spectrometry. Bioinformatic cluster analysis for peptidomic patterns and cross validation was performed with GeneSpring software.

Results:: Plasma from 429 donors was analyzed in this preliminary study. For USA donors (n = 378), MALDI TOF mass spectrometric analyses of 249 POAG and 138 CTRL plasma has allowed correct prediction of 96% as either POAG or normal based on peptidomic profiles. For Indian donors (n = 42), mass spectrometric analyses of 22 POAG and 20 CTRL provided 90% correct prediction as either POAG or normal. The peptide patterns from Indian and US plasma exhibit distinct differences. Relative to normal controls, the mean intensity of peptide m/z 1896 was elevated about 95% in the Indian POAG plasma and 160% in the USA POAG plasma. Peptide m/z 1896 has been sequenced and determined to be from complement C4B.

Conclusions:: These preliminary results provide proof of principle that plasma peptidomic patterns offer potential utility in predicting POAG susceptibility and monitoring therapeutic efficacy. Peptidomic pattern differences between USA and Indian plasma may reflect ethnic and environmental differences between the populations. The significance of the elevated complement C4B peptide in POAG plasma remains to be determined. Such findings may provide insights into the mechanism of POAG pathogenesis.

Keywords: proteomics • blood supply • proteolysis