SYNERGISTIC SUPPRESSION OF RETINAL-PIGMENT EPITHELIAL-CELL PROLIFERATION IN CULTURE BY RADIATION AND HYPERTHERMIA

Purpose. To study combination effects of radiation and hyperthermia on the in vitro cell proliferation of cultured human retinal pigment epithelial cells; to explore possible application of the combination treatment for proliferative vitreoretinopathy. Method. Cultured human retinal pigment epithelial cells were treated by radiation, hyperthermia, or a combination of the two. Cell proliferation was evaluated by counting the cell number and by the uptake of bromodeoxyuridine. Results. X-ray irradiation of 100 cGy or 300 cGy was not effective in suppressing proliferation of the retinal pigment epithelial cells. Similarly, heat treatment at 42-degrees-C or 43-degrees-C for 30 min did not suppress proliferation of the retinal pigment epithelial cells. However, combination of hyperthermia at 42-degrees-C for 30 min with 300 cGy irradiation suppressed cellular growth of the retinal pigment epithelial cells to 35.7% of the control as estimated by the cell counting and to 48.3% by bromodeoxyuridine uptake study. Combination treatment of 43-degrees-C, 30 min hyperthermia and 300 cGy irradiation was more effective. Conclusions. A combination of low-dose radiation and mild hyperthermia is effective in the suppression of growth of cultured human retinal pigment epithelial cells, and the effects were found to be synergistic. It is expected that the synergistic effects will lower the radiation dose and also reduce the possible side effects of radiation in the treatment of proliferative vitreoretinopathy.