The Mongolian gerbil as an advanced model to study cone system physiology

Exploration of the visual streak of the Mongolian gerbil as a model for the human central retina

Introduction

The Mongolian gerbil (MG), a day-active rodent, features a particular retinal region of high visual acuity, the visual streak (VS). Optimized for vision in desert-like environments, the VS allows for a perfect view of the horizon between the projection areas of the sky and the ground. Here, we assess the structural basis of this specialized region and compare the findings to the conditions at the human retinal center.

Methods

The VSs of MG retinas (n = 5) were evaluated morphologically with immunohistochemistry for cone, rod, and RPE cell-specific markers in dorsoventral cross-sections, and the results were compared to data from the near (adjacent) and far periphery. Mass spectrometry of the VS and peripheral retina/RPE was used to analyze the proteomic differential expression between these regions.

Results

In the VS of the MG, we found an increased density of cones, elongated photoreceptor outer segments (OSs), and a rod-to-cone ratio lying within the zone of descent between the border of the macula and the fovea (macular shoulder). Similarly, the base area of retinal pigment epithelium (RPE) cells in the VS was significantly reduced, while cells were taller than those in the periphery. Accordingly, proteomic data provided evidence for an enhanced abundance of key proteins relevant to photoreceptor and RPE function and pathophysiology of macular diseases in the VS.

Conclusion

The high degree of conformance between the VS data of the MG and the human central retina renders the MG a promising rodent, non-primate model of the central human retina.

Morphological characterization of retinal development from birth to adulthood via retinal thickness assessment in mice: A systematic review

The morphology and thickness of the retinal layers are valuable biomarkers for retinal health and development. The retinal layers in mice are similar to those in humans; thus, a mouse is appropriate for studying the retina. The objectives of this systematic review were: (1) to describe normal retinal morphology quantitatively using retinal layer thickness measured from birth to age 6 months in healthy mice; and (2) to describe morphological changes in physiological retinal development over time using the longitudinal (in vivo) and cross-sectional (ex vivo) data from the included studies. A PubMed search was conducted for articles published from to 1980-2024 that included quantitative data. Prior to sexual maturity, an increase in the total retinal and inner plexiform layer thicknesses were observed, with a decrease in the inner nuclear layer thickness. After sexual maturity, an asymptotic decrease in thickness was observed up to age 6 months in all layers; during this period, no significant changes were observed in the outer nuclear layer or nerve fiber layer/ganglion cell layer complex. Potential sources of variability and inconsistency among the studies included differences in imaging modality, animal strain, measurement timing, and retinal segmentation/assignment techniques. These findings highlight the importance of including a control group in experimental designs and providing comparative data for further investigations.