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Chantal Dysli, Muriel Dysli, Martin Sebastian Zinkernagel, Volker Enzmann; Retinal Fluorescence Lifetime Characteristics in Mouse Models of Pharmacologically Induced Retinal Degeneration. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5929.
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© ARVO (1962-2015); The Authors (2016-present)
Fluorescence Lifetime Imaging Ophthalmoscopy (FLIO) is used for non-invasive in vivo measurement of fluorescence lifetimes of natural fluorophores of the retina.<br /> By directed induction of degeneration of the photoreceptors (PR) and the retinal pigment epithelium (RPE), the contribution of these individual layers to the measured fluorescence lifetime signal are investigated.
Wildtype C57BL/6 mice (6-8 weeks) were used for this experiment. Degeneration of the RPE was induced by intravenous injection of sodium iodate (NaIO3, 35 mg/kg). N-methyl-N-nitrosourea (MNU, 45 mg/kg) injected intraperitoneally was used for degeneration of the photoreceptor cell layer. NaIO3 mice, MNU mice, and control mice (NaCl) were measured at day 3, 7, 14, and 28 after injection. Fluorescence lifetime imaging was performed using a fluorescence lifetime imaging ophthalmoscope (FLIO, Heidelberg Engineering, Germany). The fluorescence excitation wavelength was 473 nm and decay times were measured in a short and in a long spectral channel (SSC: 498-560 nm, LSC: 560-720 nm). Corresponding optical coherence tomography images were acquired and histology (H&E) was performed from all retinas at the latest time point.
At day 28, fluorescence lifetimes were prolonged by 8% in the short and 61% in the long spectral channel in NaIO3 mice compared to control animals (p=0.21 and p=0.004 , respectively). In MNU mice, retinal lifetimes were shortened by 27% in the short and 51% in the long spectral channel (both p=0.0028). OCT images and histology verified the cell type-specific degeneration process over time.
Specific degeneration of the RPE by NaIO3 lead to longer mean fluorescence lifetimes of the retina compared to control mice, whereas in degeneration of the photoreceptor layer induced by MNU shorter lifetimes are measured. Therefore, short retinal fluorescence lifetimes may origin from the RPE and may be modified by the overlaying retinal layers.
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