Left-Right Determination Factor 2 (LEFTY2) Is an Aqueous Humor Biomarker for Exfoliation Glaucoma

Exfoliation syndrome (XFS) is characterized by deposition of exfoliation material (XFM) in the anterior segment. XFM contributes to development of exfoliation glaucoma (XFG). Here, we evaluated left-right determination factor 2 (LEFTY2), a TGFβ superfamily protein, as an XFS and XFG biomarker.

Aqueous humor (AH) and/or blood was collected from patients undergoing cataract surgery. Controls included patients with cataracts (CAT; AH, n = 78; blood, n = 20) or cataracts and primary open-angle glaucoma (CAT/GL; AH, n = 67; blood, n = 20). Affected groups included patients with cataracts and XFS (AH, n = 32; blood, n = 2) or cataracts and XFG (AH, n = 42; blood, n = 19). LEFTY2 concentration was measured by ELISA. To test if LEFTY2 is TGFβ responsive, human trabecular meshwork (HTM) cell cultures were treated with TGFβ1-3, and LEFTY2 expression was quantified by real-time quantitative PCR or ELISA.

AH LEFTY2 concentrations were significantly elevated in XFG patients (27.23 ± 45.39 ng/mL) versus controls (CAT: 1.19 ± 0.72 ng/mL, P < 0.0001; CAT/GL: 1.68 ± 1.81 ng/mL, P < 0.0001). ROC analyses indicated that LEFTY2 is a good AH biomarker for XFG (CAT vs. XFG, AUC = 0.87; P < 0.0001). LEFTY2 AH levels were highest in eyes judged to have the heaviest XFM deposits (ρ = 0.341, P = 0.0054). Plasma LEFTY2 levels did not correlate with disease status or ocular LEFTY2 levels. TGFβ treatment significantly increased LEFTY2 expression in HTM cells.

LEFTY2 is a promising AH biomarker for XFG. Its clinical value may be limited by accessibility, OD/OS discordance, and interpatient variability. Its role in XFG pathogenesis requires further study.

Identification of biomarkers for XFG may improve early detection and treatment.