Abstract
Purpose/Aim of the Study. Subthreshold micropulse diode laser photocoagulation is an effective treatment for macular edema. The molecular mechanisms underlying treatment success are poorly understood. Therefore, we investigated the effects of sublethal laser energy doses on a single layer of densely cultured ARPE-19 cells as a model of the human retinal pigment epithelium (RPE). Materials and Methods. A single layer of densely cultured human ARPE-19 cells was perpendicularly irradiated with a micropulse diode laser. Nonirradiated cells served as controls. Sublethal laser energy was applied to form a photocoagulation-like area in the cultured cell layers. Hsp70 expression was evaluated using quantitative polymerase chain reaction and immunocytochemistry. Results. Photocoagulation-like areas were successfully created in cultured ARPE-19 cell layers using sublethal laser energy with our laser irradiation system. Hsp70 mRNA expression in cell layers was induced within 30 min of laser irradiation, peaking at 3 h after irradiation. This increase was dependent on the number of laser pulses. Hsp70 upregulation was not observed in untreated cell layers. Immunostaining indicated that Hsp70 expression occurred concentrically around laser irradiation sites and persisted for 24 h following irradiation. Conclusion. Sublethal photothermal stimulation with a micropulse laser may facilitate Hsp70 expression in the RPE without inducing cellular damage.
Highlights
Laser photocoagulation is widely used for treating various retinal diseases, including diabetic retinopathy [1], branch retinal vein occlusion [2], and central serous retinopathy [3]
The culture dish was placed on a mechanical stage so that the dish could be moved into the proper laser irradiation position in a flat X-Y plane
Because the clinical efficacy of macular edema treatment has been shown to be better with high-density micropulse laser irradiation than with standard laser treatment [16], we examined the effects of varying the number of laser irradiation lesions on HSPA1A mRNA levels by changing the spacing of laser irradiation lesions on the cultured cell layer, which resulted in an increase in the number of lesions from 81 to 477
Summary
Laser photocoagulation is widely used for treating various retinal diseases, including diabetic retinopathy [1], branch retinal vein occlusion [2], and central serous retinopathy [3]. Conventional laser treatments are destructive procedures used to create whole-layer damage to retinal tissue. Such invasive treatments are not suitable for macular diseases, including macular edema, because laser scars generally grow larger and create permanent scotomas. Retinal coagulation scars are not visible upon fundoscopic examination, autofluorescent imaging, or optical coherence tomography [11, 12] when the eyes are treated with a subthreshold micropulse laser. Many studies have shown the clinical efficacy of this treatment [10, 13,14,15,16,17]; few studies have investigated the molecular mechanisms responsible for fluid absorption from retinal tissue [18]. Lavinsky et al found slight morphological changes following laser irradiation with a low-energy output in Dutch-belted
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