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S. Balaiya Mehanathan, R. Malyapa, N. Mendenhall, K. V. Chalam; Proton Radiation Predominantly Destroys Choroidal Endothelial Cells While Preserving Retinal Ganglion Cells. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6221.
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© ARVO (1962-2015); The Authors (2016-present)
Laser photocoagulation and photodynamic therapy are the only proven treatment for choroidal neovascular age related macular degeneration (AMD). Recent advancement in therapeutic medicine is the use of proton radiotherapy in eye diseases due to its specific energy distribution in three dimensional pattern to reach its precise target. Newly proliferating vascular endothelial cells are sensitive to radiation contrary to mature retinal neurons. In the present study we evaluated proton radiation effect on cultured retinal and choroidal cell colonies.
Retinal ganglion cell (RGC-5), retinal pigment epithelial cell (ARPE-19) and choroidal endothelial cells (RF6A) with vascular endothelial growth factor (VEGF)that representing AMD model were chosen for the study. Plating efficiency of each cell line was observed after 13-15 days by colony count assay using crystal violet. Dose dependent curve of each cell line was determined upon exposure to single fraction of 2 Gy, 4 Gy, 8 Gy, 12 Gy and 16 Gy of protons with the presence of an internal control. The survival rate after radiation to retinal cells was measured after 13-15 days by colony count and structural morphology was observed using phase contrast microscopy.
Plating efficiency of retinal ganglion cell was 40% which is about three times higher than endothelial cells with VEGF and pigment epithelial cells. Dose response revealed that all three cells were not viable at 16 Gy and found to be a lethal. Ganglion cell showed 70% survival response at 2 Gy which decreased to 40% at 4 Gy and 10% at 8 Gy. In contrast endothelial cell with VEGF showed survival response of 46% at 2 Gy further to 33% and 3% at 4 and 8 Gy respectively. At 12 Gy both ganglion and endothelial cells were observed to be less viable (<1%).
Endothelial cells are significantly radio sensitive at 4 and 8 Gy dose compared to retinal ganglion cells. This dosage may provide a therapeutic window for treatment of macular degeneration.
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