Outer retinal degeneration in a non-human primate model using temporary intravitreal tamponade with N-methyl-N-nitrosourea in cynomolgus monkeys

Abstract

The main objective of this study was to induce and evaluate drug-dose-dependent outer retinal degeneration in cynomolgus monkeys by application of N-methyl-N-nitrosourea (MNU). Intravitreal temporary tamponade induced outer retinal degeneration with N-methyl-N-nitrosourea (MNU) solutions (2–3 mg/mL) after vitrectomy in five cynomolgus monkeys. Optical coherence tomography (OCT), fundus autofluorescence (FAF), full-field electroretinography (ffERG), and visual evoked potentials (VEP) were performed at baseline and weeks 2, 6, and 12 postoperatively. At week 12, OCT angiography, histology, and immunohistochemistry were performed. Outer retinal degeneration was observed in four monkeys, especially in the peripheral retina. Anatomical and functional changes occurred at week 2 and persisted until week 12. FAF images showed hypoautofluorescence dots, similar to AF patterns seen in human retinitis pigmentosa. Hyperautofluorescent lesions in the pericentral area were also observed, which corresponded to the loss of the ellipsoid zone on OCT images. OCT revealed thinning of the outer retinal layer adding to the loss of the ellipsoid zone outside the vascular arcade. Histological findings confirmed that the abovementioned changes resulted from a gradual loss of photoreceptors from the perifovea to the peripheral retina. In contrast, the inner retina, including ganglion cell layers, was preserved. Functionally, a decrease or extinction of scotopic ffERGs was observed, which indicated rod-dominant loss. Nevertheless, VEPs were relatively preserved. Therefore, we can conclude that temporary exposure to intravitreal MNU tamponade after vitrectomy induces rod-dominant outer retinal degeneration in cynomolgus monkeys, especially in the peripheral retina.

Multiple consecutive-biphasic pulse stimulation improves spatially localized firing of retinal ganglion cells in the degenerate retina

“…While this study successfully demonstrated the efficacy of burst stimulation in normal and degenerate mouse models, its feasibility for human clinical studies necessitates validation in a non-human primate model that closely resembles a human retinal system. Our previous work established an RD monkey model [ 39 ], highlighting the drawbacks of single high-amplitude pulse stimulation on RGC response resolution [ 6 ]. Our upcoming research will assess the efficacy of burst stimulation to enhance spatial resolution in the RD monkey model, potentially enabling translation into human clinical studies based on insights from the non-human primate model.…”

Double‐Sided, Thin‐Film Microelectrode Array with Hemispheric Electrodes for Subretinal Stimulation

“…In Vitro Subretinal Stimulation: Retinal patches were isolated from two 10-week-old wild-type mice (C57BL/6J strain) and two adult male cynomolgus monkeys (Macaca fascicularis) with outer retinal degeneration induced by N-methyl-N-nitrosourea [49] (Figure S7a,b, Supporting Information). The retinal patch was attached to the recording electrode array (60pMEA200/30iR-Ti, Multichannel Systems GmbH, Germany) with the ganglion cell layer facing down contacting recording electrodes.…”

The Variation of Electrical Pulse Duration Elicits Reliable Network-Mediated Responses of Retinal Ganglion Cells in Normal, Not in Degenerate Primate Retinas

“…This study used adult male cynomolgus monkeys (Macaca fascicularis) with normal (n = 3) and outer RD induced by MNU (n = 3) [19]. The monkeys had a mean age of 53.6 ± 2.2 months and a mean body weight of 3.7 ± 0.4 kg.…”

“…The subjects were sacrificed approximately 14-21 weeks after MNU administration. The housing condition, how to euthanize, and the detailed methods of the operation for vitrectomy and injection of MNU were described in our previous study [19].…”

“…However, these genetic RD models do not fully mimic human RP because they show macular, not peripheral, degeneration [17,18]. Our previous study [19] established an NHP RP model with the cynomolgus monkey using N-methyl-N-nitrosourea (MNU), which induces rod-specific retinal degeneration.…”