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KV Chalam, S Balaiya, R Malyapa; Proton Radiation Destroys VEGF Enriched Choroidal Endothelial Cell Proliferation, an association With Age Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1780.
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© ARVO (1962-2015); The Authors (2016-present)
Exudative form of age related macular degeneration (AMD) is the leading cause of blindness above the age of 65 in the western world. Choridcal neovasculization (CNV) is characterized by vascular endothelial growth factor (VEGF) mediated choroidal endothelial cell (CEC) proliferation. CNV is currently being treated with ant-VEGF therapy but requires repeated intravitreal injections. Novel treatments such as proton beam radiation delivers a homogenous three-dimensional dose to the target lesion with minimal damage to surrounding healthy tissues and may reduce the frequency of repeat intravitreal treatments. We evaluated the sensitivity of proliferating CEC enriched with VEGF to escalating doses of proton beam radiation to optimize effective dose level.
Choridal endothelial cells were maintained at log-scale enriched with VEGF at a concentration of 50ng/mL. Semi-confluent cells were exposed to single fraction of varying radiation dose. Dosage ranged from 2, 4, 8 and 12 CGE (Cobalt Gray Equivalent) with a presence of an internal control. Post radiation viability of choroidal endothelial cells were analyzed on day 2 and day 5 using WST-1 assay. Cell survival was quantified with trypan blue dye exclusion assay using Vi-cell XR.
On day 2, WST-1 assay results showed 98.1% of viability at 2 CGE, 96.1% at 4CGE, 83.4% at 8 CGE and 68.9% at 12 CGE, compared to control. However, on day 5, the viability decreased to 58.2%, 57.6%, 51.6% and 27% at 2, 4, 8 and 12 CGE respecively after radiation. Vi-cell XR studies confirmed the number of viable cells as 97.9%, 72.6%, 57.5%, 47.2% at 2, 4, 8 and 12 CGE of post radiation day 2. The cell numbers decreased at further day interval 5 which were of 68.4%, 58.9%, 31.5% and 25.3% proportionate to the degree of radiation.( r=0.7)
Proton beam radiation at doses of 8 and 12 CGE significantly decreases cell viability of VEGF induced choroidal endothelial cells and can be used as starting treatment dose for choroidal neovascularization associate with age related macular degeneration.
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