Neuroprotective Effects of Thermal Stimulation of the Retina and Selective Retina Therapy Implications for the Treatment of Macular Disease - Abstract
Objectives: Thermal Stimulation of the Retina (TSR, a photothermal sublethal continuous wave laser) as well as Selective Retina Therapy (SRT, a photodisruptive selective
RPE regenerating micro pulsed laser) have shown therapeutic effects on age-related macular degeneration (AMD), in AMD mouse models. Both laser modalities act on the RPE regenerative processes. In this study, we investigate a possible neuroprotective effect of TSR and SRT.
Methods: Neuronal SH-SY5Y cells were stressed by H2O2 to simulate oxidative stress on neuroretinal cells, like seen in AMD. Cell viability was measured by methylthiazolyl-tetrazolium (MTT), assay. Cells were incubated with apical supernatants from organ cultures (retinal pigment epithelium (RPE), Bruch’s Membrane (BrM) and choroid), treated by TSR or by SRT and compared with cells incubated with supernatants from controls to evaluate neuroprotective effects.
Apical secretion of Nerve Growth Factor (NGF), Brain Derived Neurotrophic Factor (BDNF), Vascular Endothelial Growth Factor (VEGF), and Pigment Epithelium Derived Factor (PEDF), were measured quantitatively by ELISA in untreated or irradiated porcine organ cultures.
Results: Viability of oxidatively stressed SH-SY5Y cells declined by about 50 %. Supernatants from TSR treated organ cultures had a protective effect, in contrast to cells
incubated with supernatants from SRT treated organ cultures.
No NGF, nor BDNF secretion could be detected in untreated or irradiated controls in the apical compartment of organ cultures. Apical VEGF secretion was significantly reduced,
PEDF significantly increased after SRT treatment. This was not the case after TSR treatment.
Conclusions: TSR-treated organ cultures exerted neuroprotective, by so far unidentified mediators. There is no RPE derived NGF or BDNF secretion to the apical compartment
and this is not altered by laser therapy. Apical VEGF decrease and PEDF increase in SRT treated organ cultures did not affect neuronal cell survival. TSR might have neuroprotective properties which need to be examined in further studies.