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EVALUATION OF CHOROIDAL ENDOTHELIAL CELL PROLIFERATION AFTER EXPOSURE TO VARYING DOSES OF PROTON BEAM RADIATION

Chalam, Kakarla V MD, PhD*; Balaiya, Sankarathi PhD*; Malyappa, Robert S MD, PhD†; Hsi, Wen PhD†; Brar, Vikram S MD*; Murthy, Ravi K MD*

doi: 10.1097/IAE.0b013e3181dee621
Original Study

Purpose: 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.

Methods: 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.

Results: 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).

Conclusion: 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: kchalam@jax.ufl.edu

© The Ophthalmic Communications Society, Inc.