Ryan H Mason1,2,3, Samuel A Minaker1,2,3, Gabriela Lahaie Luna4, Priya Bapat1,2,3, Armin Farahvash1,2,3, Anubhav Garg1,2,3, Nishaant Bhambra1,2,3, Rajeev H Muni5,6,7,8. 1. Department of Ophthalmology, St. Michael's Hospital/Unity Health Toronto, Toronto, ON, Canada. 2. Department of Ophthalmology & Vision Sciences, University of Toronto, Toronto, ON, Canada. 3. Kensington Vision and Research Centre, Toronto, ON, Canada. 4. Department of Ophthalmology, Queen's University, Kingston, ON, Canada. 5. Department of Ophthalmology, St. Michael's Hospital/Unity Health Toronto, Toronto, ON, Canada. rajeev.muni@gmail.com. 6. Department of Ophthalmology & Vision Sciences, University of Toronto, Toronto, ON, Canada. rajeev.muni@gmail.com. 7. Kensington Vision and Research Centre, Toronto, ON, Canada. rajeev.muni@gmail.com. 8. University of Toronto/Kensington Health Ophthalmology Biobank and Cytokine Laboratory, Toronto, ON, Canada. rajeev.muni@gmail.com.
Abstract
BACKGROUND: Diabetic retinopathy is a major complication of diabetes mellitus, where in its most advanced form ischemic changes lead to the development of retinal neovascularization, termed proliferative diabetic retinopathy (PDR). While the development of PDR is often associated with angiogenic and inflammatory cytokines, studies differ on which cytokines are implicated in disease pathogenesis and on the strength of these associations. We therefore conducted a systematic review and meta-analysis to quantitatively assess the existing body of data on intraocular cytokines as biomarkers in PDR. METHODS: A comprehensive search of the literature without year limitation was conducted to January 18, 2021, which identified 341 studies assessing vitreous or aqueous cytokine levels in PDR, accounting for 10379 eyes with PDR and 6269 eyes from healthy controls. Effect sizes were calculated as standardized mean differences (SMD) of cytokine concentrations between PDR and control patients. RESULTS: Concentrations (SMD, 95% confidence interval, and p-value) of aqueous IL-1β, IL-6, IL-8, MCP-1, TNF-α, and VEGF, and vitreous IL-2, IL-4, IL-6, IL-8, angiopoietin-2, eotaxin, erythropoietin, GM-CSF, GRO, HMGB-1, IFN-γ, IGF, IP-10, MCP-1, MIP-1, MMP-9, PDGF-AA, PlGF, sCD40L, SDF-1, sICAM-1, sVEGFR, TIMP, TNF-α, and VEGF were significantly higher in patients with PDR when compared to healthy nondiabetic controls. For all other cytokines no differences, failed sensitivity analyses or insufficient data were found. CONCLUSIONS: This extensive list of cytokines speaks to the complexity of PDR pathogenesis, and informs future investigations into disease pathogenesis, prognosis, and management.
BACKGROUND: Diabetic retinopathy is a major complication of diabetes mellitus, where in its most advanced form ischemic changes lead to the development of retinal neovascularization, termed proliferative diabetic retinopathy (PDR). While the development of PDR is often associated with angiogenic and inflammatory cytokines, studies differ on which cytokines are implicated in disease pathogenesis and on the strength of these associations. We therefore conducted a systematic review and meta-analysis to quantitatively assess the existing body of data on intraocular cytokines as biomarkers in PDR. METHODS: A comprehensive search of the literature without year limitation was conducted to January 18, 2021, which identified 341 studies assessing vitreous or aqueous cytokine levels in PDR, accounting for 10379 eyes with PDR and 6269 eyes from healthy controls. Effect sizes were calculated as standardized mean differences (SMD) of cytokine concentrations between PDR and control patients. RESULTS: Concentrations (SMD, 95% confidence interval, and p-value) of aqueous IL-1β, IL-6, IL-8, MCP-1, TNF-α, and VEGF, and vitreous IL-2, IL-4, IL-6, IL-8, angiopoietin-2, eotaxin, erythropoietin, GM-CSF, GRO, HMGB-1, IFN-γ, IGF, IP-10, MCP-1, MIP-1, MMP-9, PDGF-AA, PlGF, sCD40L, SDF-1, sICAM-1, sVEGFR, TIMP, TNF-α, and VEGF were significantly higher in patients with PDR when compared to healthy nondiabetic controls. For all other cytokines no differences, failed sensitivity analyses or insufficient data were found. CONCLUSIONS: This extensive list of cytokines speaks to the complexity of PDR pathogenesis, and informs future investigations into disease pathogenesis, prognosis, and management.
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