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Jost Hillenkamp, Sofya Bartsch, Alexa Karina Klettner, Ralf Brinkmann, Johann Roider; Effect of Selective Retina Therapy (SRT) on the inflammatory microenvironment of the subretinal space. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6348.
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To investigate the effect of Selective Retina Therapy (SRT) as a treatment of early age-related macular degeneration (AMD) on the inflammatory microenvironment of the subretinal space with a focus on key pro-inflammatory and complement system factors.
Porcine retinal pigment epithelium (RPE)-Bruch-choroid explants maintained in static organ culture in modified Ussing chambers were irradiated with a pulsed Nd:YLF laser (wave length 527 nm, pulse duration 1.7 µs, repetition rate 100 Hz, spot size 200 µm) with 140 and 180 mJ/cm2 (below and above ED50-threshold radiant exposure for RPE cell death, respectively). Wound healing of irradiated RPE and cell viability were assessed by calcein-AM cell vitality test after 5 days of culture. Following SRT culture medium was collected from the apical and basolateral aspects of the RPE every 24 hours for quantification of complement factors beta (CFB) and C3 (C3), tumour growth factor beta 2 (TGF b2), tumour necrosis factor alpha (TNF alpha), and interferon gamma (IFN) by ELISA. The irradiated RPE-Bruch-choroid tissue was lysed and the same factors were quantified by Western blot (each factor n = 4-18).
Compared to controls secreted basolateral C3 was reduced (0.45 ± 0.15, p<0.05) while secreted apical CFB was increased (42.11 ± 1.94, p<0.05) 24 hours after SRT with 180 mJ/cm2. Basolateral and apical TGF beta 2, TNF alpha at all timepoints, C3, and CFB levels 48 and 96 hours after SRT with 180 mJ/cm2 were not altered. Following SRT with 180 mJ/cm2, tissue IFN levels quantified by Western blot were reduced (0.64 fold ± 0.26 (p<0.05), all other factors remained unaltered (C3 0.89-fold ± 0.1, TGF b2 0.72-fold ± 0.28, TNF alpha 0.94-fold ± 0.12 (all p>0.05)). Following SRT with 140 mJ/cm2 the tissue levels of all factors quantified by Western blot remained unaltered (C3 1.26-fold ± 0.56, TGF b2 1.23-fold ± 0.15, TNF alpha 0.94-fold ± 0.28, IFN 1.37-fold ± 0.75 (all p>0.05)).
Inflammation and complement activation are fundamental components of AMD. The results of this study suggest that SRT does not trigger a pro-inflammatory response of the RPE during wound healing after laser exposure. Consequently, SRT does not seem to trigger AMD progression.
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