Identification of urinary biomarkers for age-related macular degeneration

Age-related macular degeneration (AMD) can be considered as a chronic low-grade systemic inflammatory disease. This study was undertaken to test the associations of AMD with the urinary proinflammatory cytokines transforming growth factor (TGF)-β1, macrophage chemoattractant protein (MCP)-1 and C3a-desArg, as potential noninvasive biomarkers for monitoring AMD.

A cross-sectional study of 103 AMD cases, comprising early AMD (n = 51), geographic atrophy (GA; n = 19), or choroidal neovascularization (CNV; 33), and 54 unrelated controls, aged 73 ± 9 years, who attended the Royal Victorian Eye and Ear Hospital and private practice in Victoria, Australia. AMD status was determined from the bilateral retinal digital photographs and through angiography and optical coherence tomography images when confirmation of CNV was needed. Serum and urine cytokine levels were measured by immunoassay and the rs1061170 (Y402H) single-nucleotide polymorphism of the complement factor H (CFH) gene was determined.

Multivariate logistic regression analyses demonstrated significant associations of urinary TGF-β1 levels (odds ratio [95% confidence interval]: OR = 1.24 [1.02-1.50]; P < 0.031) and MCP-1 levels (OR = 1.07 [1.02-1.12]; P < 0.008), in early AMD, and also MCP-1 levels with GA (OR = 1.10 [1.03-1.17]; P < 0.003). There was no correlation between urinary and serum cytokine levels. Individuals with one or more copies of the C allele (Y402H) were 2.5 times more likely to have urinary MCP-1 above median levels (P < 0.040).

This study demonstrates a novel finding of an association between elevated urinary cytokines TGF-β1 and MCP-1 and AMD. Further development of a urinary biomarker profile could provide a practical tool for detection of early AMD, progression monitoring, and assessment of treatment efficacy.