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Katharina Kern, Richard Paul Schaefer, Carla Lotta Mertineit, Ralf Brinkmann, Yoko Miura; Influence of thermal laser irradiation on cell proliferation and wound healing of primary RPE cell cultures. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4004.
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© ARVO (1962-2015); The Authors (2016-present)
Cell loss of retinal pigment epithelium (RPE) due to the death of damaged cells is suggested to underlie many age-related retinal disorders. Therefore, activating the restoration of RPE cell defects is crucial to preserve the retinal function. Laser-induced hyperthermia is discussed as a new therapeutic strategy to improve functionality of the RPE. In this study we investigated the influence of transient thermal impacts on the proliferation and wound healing of RPE cells.
Confluent RPE cell cultures were wounded either by thermal irradiation with a continuous wave thulium laser (wavelength: 1940 nm, spot diameter: 30 mm, irradiation time: 10 s) or mechanically thorough scratching with a pipette tip (vertically crossed lines across the diameter of culture dish). In the thulium laser irradiation, the transient temperature profile across the culture dish was Gaussian-like, with a maximal temperature at the center (Tmax) of 59°C, and the cells at the central area with T≥ 47°C were lethally damaged through irradiation. Cell proliferation was tested at 0, 24 or 48 h after wounding by detecting mitotic processes using 5-Ethinyl-2’-Desoxyuridin (EdU). In order to investigate the effect of a precede sub-lethal hyperthermia on RPE wound healing, confluent RPE cell cultures were sub-lethally irradiated with thulium laser for 10 s (Tmax= 43°C), followed by wounding with a pipette tip 1 h later. Wound healing was observed with long-term video microscopy (60 h, images were taken every 90 s). The cell front velocity (CFV) as an indicator of the speed of wound closure was assessed and compared to the one of the non-irradiated cultures.
The proliferation assays with EdU showed that heat-induced wounds lead to strong stimulation of cell proliferation within 24 h focused to the wound border, where the cells were sub-lethally heated. In contrast the mechanical wounds showed mild and diffuse enhancement of cell proliferation. Regarding the effect of a transient sub-lethal thermal irradiation, the CFV of the wound front of non-irradiated cultures was 7.6 µm/h, whereas the one of the sub-lethally irradiated cultures was significantly higher with 16.3 µm/h (p < 0.001).
The results suggest that sub-lethal thermal stimulation may enhance cell proliferation as well as wound healing of RPE cells, and thus may be useful for the restoration of damaged RPE.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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