Focal epiretinal radiation has emerged as a promising tool in the management of choroidal neovascularization associated with age-related macular degeneration. However, the dosages tested are not backed by cell culture studies used in the clinical setting empirically.
Choroidal endothelial cells (RF6A) were maintained in a log scale and exposed to a single fraction of 2, 4, 8, and 12 cobalt gray-equivalent of proton radiation with an internal control. Cell viability was quantified using Vi-cell XR and neutral red assay at days 5, 9, and 12 after radiation. Mitochondrial viability using WST-1 and reactive oxygen species levels using dihydrorhodamine 123 were measured at similar intervals.
By using neutral red assay, on day 12, the percentages of viable cells compared with control were 100.1 ± 5.7%, 96.7 ± 23.3%, 27.6 ± 6.6%, and 19.5 ± 3% at radiation doses of 2, 4, 8, and 12 cobalt gray-equivalent, respectively (P < 0.001). Increase in reactive oxygen species levels correlated with the number of dead cells implicating reactive oxygen species as an intermediary molecule (r2 = 0.85-0.96).
Our study shows sensitivity of cultured choroidal endothelial cells to proton beam radiation at doses of 8 and 12 cobalt gray-equivalent in an in vitro model.
The authors' study shows sensitivity of cultured choroidal endothelial cells to proton beam radiation at doses of 8 and 12 cobalt gray-equivalent in an in vitro model.
From the *Department of Ophthalmology, University of Florida College of Medicine, Jacksonville, Florida; and †Department of Radiation Oncology, University of Florida Proton Therapy Institute, Jacksonville, Florida.
The authors declare no proprietary interest or funding support.
Reprint requests: Kakarla V. Chalam, MD, PhD, Department of Ophthalmology, University of Florida, 580 West 8th Street, Tower II, 3rd Floor, Jacksonville, FL 32209; e-mail: firstname.lastname@example.org