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Norio Hasegawa, Miho Nozaki, Daisuke Ozone, Shuichiro Hirahara, Yuichiro Ogura; Response of the retinal pigment epithelium to subthreshold laser photocoagulation in mice. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5846.
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© ARVO (1962-2015); The Authors (2016-present)
Endpoint Management ®(EpM) software (Topcon Medical Laser Systems, Santa Clara, CA) is one of the subthreshold laser that was developed for the treatment of the macular diseases such as diabetic macular edema. However the mechanism of its efficacy is not fully elucidated. The purpose of this study is to evaluate the response of the retinal pigment epithelium (RPE) after EpM laser in mice.
Retinal laser photocoagulation was performed on male C57BL/6J mice with EpM and conventional setting using PASCAL Streamline 577 (Topcon Medical Laser Systems). Appropriate EpM laser setting was determined using color fundus photograph, fundus autofluorescence (FAF) and fluorescein angiography (FA) using Optos200Tx (Optos PLC., Dunfermline, Scotland, UK). Expression of Heat Shock Protein (HSP) 70 in the RPE were quantified using ELISA after laser, and RPE flatmount was evaluated by immunohistochemical staining against ZO-1 and RPE65 after laser.
With conventional setting (80mW, 15 milliseconds, 200μm), the laser spots were well visible on day 1, 3 and 7 after laser, and FAF showed hyperfluorescence at the laser spots on day 1, 3 and 7 after laser. For EpM setting, the titration was performed in mice retina, and the power that showed “barely visible” spot was 30 mW. With 50% EpM setting, marked hyperfluorescence was detected 3 days after laser, but with 30% EpM setting, no abnormal fluorescence was found on day 1, 3 and 7 after laser. We employed the EpM setting as 30% EpM of 30 mW, 15 milliseconds, 200μm in this study. The level of HSP70 in the RPE was significantly elevated on day 3 and 7 after laser treatment (p<0.05) in EpM group, whereas there was no significant elevation in conventional setting group. On day 1 after laser, both EpM and conventional laser group showed destruction of ZO-1 and RPE65 staining, but EpM group showed normal staining of ZO-1 and RPE65 on day 3. However conventional laser group showed destruction of ZO-1 and RPE staining even on day 7 after laser.
HSP70 have been implicated in facilitating tissue remodeling. Our results showed that EpM laser induced HSP70 expression in the RPE, and early recovery of tight junction of the RPE, and the function of the RPE cells. Our findings suggest that EpM laser might be effective in the macular diseases, via induction of the RPE remodeling.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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