Screening Blood and Vitreous for Biomarkers Associated with Proliferative Diabetic Retinopathy

<b>Background/Objectives</b>: Uncontrolled or long-standing diabetes can lead to proliferative diabetic retinopathy (PDR), a condition that significantly impairs vision. A subset of patients does not respond adequately to conventional therapies, such as intravitreal injections of anti-vascular endothelial growth factor (VEGF) or laser treatment. This study aims to identify potential biomarkers for alternative treatment pathways in the vitreous and blood of patients with severe PDR. <b>Methods</b>: Vitreous samples were collected from PDR patients (<i>n</i> = 3) undergoing vitrectomy for vitreous hemorrhage and from control patients (<i>n</i> = 9) undergoing ocular surgery for epiretinal membrane or macular holes. Blood samples were collected from a separate group of PDR patients (<i>n</i> = 13) and non-diabetic control patients without retinopathy (<i>n</i> = 13). Medical histories were obtained. Two-stage real-time quantitative polymerase chain reaction (qPCR) was used to evaluate mRNA expression levels of genes potentially implicated in PDR, including <i>HIF2A</i>, <i>PAI-1</i>, <i>TIE1</i>, <i>TIE2</i>, <i>ANGPT2</i>, and <i>VEGFA</i>. Molecular and statistical analyses were performed to compare PDR and control vitreous and blood samples. <b>Results</b>: The PDR vitrectomy group included two females and one male, aged 71-77 years (mean 74 years). All participants had undergone pan-retinal photocoagulation and two had received anti-VEGF injections before vitrectomy. These participants had elevated HbA1c levels. Targeted vitreous gene analysis revealed varying levels of increased expression of all genes examined as compared to the control group. A trend for increased median expression was demonstrated for all examined genes: <i>HIF2A</i> by 1.44-fold (PDR = 2.50, control = 1.74, <i>p</i> = 0.21), <i>PAI-1</i> by 1.56-fold (PDR = 3.00, control = 1.93, <i>p</i> = 0.37), <i>TIE1</i> by 1.36-fold (PDR = 2.33, control = 1.72, <i>p</i> = 0.66), <i>TIE2</i> by 2.06-fold (PDR = 2.81, control = 1.36, <i>p</i> = 0.51), <i>ANGPT2</i> by 2.93-fold (PDR = 6.32, control = 2.16, <i>p</i> = 0.1), and <i>VEGFA</i> by 3.53-fold (PDR = 3.51, control = 0.99, <i>p</i> = 0.08). PDR blood sample analysis as compared to controls showed a trend for increased expression of <i>VEGFA</i> by 1.2-fold (PDR = 0.88, control = 0.74, <i>p</i> = 0.57), whereas the other examined genes showed a trend of reduced expression; <i>HIF2A</i> decreased by 0.50-fold (PDR = 0.38, control = 0.75, <i>p</i> = 0.07), <i>PAI</i> by 0.51-fold (PDR = 0.35, control = 0.69, <i>p</i> = 0.09), <i>TIE-1</i> by 0.79-fold (PDR = 0.79, control = 1.00, <i>p</i> = 0.54), <i>TIE-2</i> by 0.70-fold (PDR = 0.58, control = 0.82, <i>p</i> = 0.34), and <i>ANGPT2</i> by 0.45-fold (PDR = 0.51, control = 1.15, <i>p</i> = 0.11). <b>Conclusions</b>: Vitreous sample analysis revealed a trend of increased mRNA expression of <i>ANGPT2</i> and <i>VEGFA</i> in patients with PDR. Blood sample analysis did not show a significant increase of <i>VEGFA</i> mRNA expression but a decreased trend of <i>HIF2A</i>, <i>PAI-1</i>, and <i>ANGPT2</i> mRNA expression. These trends warrant validation in a larger cohort to explore alternative pathways for targeted treatment.