Abstract
Purpose: :
To utilize protein arrays to characterize the distribution of a wide range of angiogenic modulators in vitreous fluids from normal and diabetic individuals.
Methods: :
Central vitreous samples were recovered from individuals with non-proliferative, pre-proliferative and proliferative diabetic retinopathy who underwent vitrectomy surgery, and from control groups of individuals with and without retinal detachments but without underlying diabetic retinopathy. Individual vitreous samples are assayed for protein content and subjected to SDS-PAGE analysis. Samples are analyzed for the relative distribution of 43 angiogenic modulators using two commercial membrane arrays coupled to a femtogram sensitive substrate. Samples are also quantitatively assayed using a micro-well plate array system for VEGF, HGF, HbEGF and FGFb.
Results: :
Membrane array analysis allows the routine detection in normal vitreous of MCP-1, ANG, GRO, TIMPs 1 and 2. These are often accompanied by angiostatin, angiopoetin-2, uPAR, VEGF-R2 and MMP-9 and other entities. Vitreous samples from all individuals with retinal detachments irrespective of underlying diabetic retinopathy invariably exhibit much stronger signals for MCP-1, GRO, ANG, TIMPs, IL-8, IL-6 and MMP-9. Elevated signals of VEGF, angiopoietin-2 and leptin are often encountered with distinctly different patterns of distribution. Elevated levels of angiopoietin-2 are common to the non-proliferative compared to the proliferative diabetic population, while elevated signals for both VEGF and leptin are observed in most, but not alldiabetic samples. Micro-well plate assays for HGF, VEGF, FGFb, and HB-EGF show elevated levels of VEGF and HGF, which are quantifiable in all samples. In this limited sample, a wide range of concentrations of increased levels of HGF and VEGF are found in the diabetic vitreous, independent of progression from non-proliferative to proliferative diabetes. The highest levels of both HGF and VEGF are detected in a non-proliferative diabetic sample that is atypical in that it is totally devoid of leptin.
Conclusions: :
Protein arrays are useful tools for identifying angiogenic modulators in the vitreous fluid and can be used to obtain a broader picture of angiogenic factors that are altered during the progression of diabetic retinopathy to identify possibly targets for therapeutic intervention.
Keywords: diabetic retinopathy • proteomics