The temporal topography of the N-Methyl- N-nitrosourea induced photoreceptor degeneration in mouse retina

Abstract

Retinitis pigmentosa (RP) is a group of inherited neurodegenerative diseases characterized by the progressive photoreceptors apoptosis. The N-Methyl- N-nitrosourea (MNU) is an alkylating toxicant which could induce photoreceptor apoptosis resembling that of the hereditary RP. However, the detailed process pattern of this degeneration remains poorly characterized. We systemically explored the topography of the photoreceptor degeneration in the MNU treated mouse, and related these spatial data with the time-dependent characteristics of retinal pathology. These temporal topographic data delineated sequential scenes of the progressive photoreceptor degeneration in the MNU treated retinas: focal photoreceptors showed different vulnerabilities to the MNU toxicity and displayed a distinctive spatial- and time-dependent progression. Moreover, the positional asymmetry between the retinal quadrants firstly provided instructive information about the unique toxicology properties of the MNU. Further mechanism study suggested that the up-regulation of Bax and Calpain-2, rather than the Caspase-3, should be responsible for the asymmetry in the MNU induced photoreceptor degeneration. Together with the comparative sensitivities to the neurotoxicity of MNU between two photoreceptor populations, these topographic data would facilitate the standardization of analytic parameters related to the MNU induced RP model, and enhance its application in the therapeutic explorations of human RP.

Topographic Quantification of the Transcorneal Electrical Stimulation (TES)–Induced Protective Effects on N-Methyl-N-Nitrosourea–Treated Retinas

“…Without the supports of topographic technologies, the effectively preserved zone might be readily overlooked, resulting in an underestimated therapeutic effect, or in contrast, a regional effect might be mistaken for global efficiency, giving rise to positive errors. 29 In the present study, TES-induced effects on the regional retina were systemically measured using topographic methods. Both the MEA and morphologic measurement suggested that the photoreceptors in the central retina were more efficiently preserved compared to the peripheral and midperipheral regions.…”

“…Neuroretinal whole mounts were prepared according to previously described methods and were then divided into quadrant patches with four incisions, at 3, 6, 9, and 12 o'clock. 29 Total RNA was extracted from the pooled retinal patches with a commercial reagent (Trizol; Gibco, Inc., Grand Island, NY, USA), followed by cDNA synthesis using the lMACS DNA Synthesis kit (Miltenyi Biotech GmbH, Bergisch-Gladbach, Germany). Primer sequences are depicted in Table 1, and all primers were quality controlled by sequencing the template on a genetic ABI analyzer (Applied Biosystems, Inc., Foster City, CA, USA).…”

Intravitreous Delivery of Αb-Crystallin Ameliorates N-Methyl-N-Nitrosourea Induced Photoreceptor Degeneration in Mice: An in vivo and ex vivo Study

“…The design of the treatment protocol was based on the basic pathological feature of animal model and previous pharmacological studies. Typically, the retinal degenerative process in MNU administered mice occurred within 7 days with a dose of 60 mg/kg [21,22]. This administered dose was considered as the optimum dose for model construction and has been used in multiple therapeutic trials [22,23].…”

“…Typically, the retinal degenerative process in MNU administered mice occurred within 7 days with a dose of 60 mg/kg [21,22]. This administered dose was considered as the optimum dose for model construction and has been used in multiple therapeutic trials [22,23]. MNU solution (5 mg/ml) was prepared by dissolving reagent in physiological saline containing 0.05% acetic acid.…”

“…Furthermore, the TUNEL assay was performed to quantify the apoptotic activity in photoreceptors. A previous study had shown that the MNU induced apoptotic activation peaked at 3 days post administration(P3), and then returned to the baseline around P7 [22]. Therefore, we performed the TUNEL assay at P3 to capture the most evident changes (Fig.…”