Changes in Retinal Structure and Ultrastructure in the Aged Mice Correlate With Differences in the Expression of Selected Retinal miRNAs

Abstract

Age and gender are two important factors that may influence the function and structure of the retina and its susceptibility to retinal diseases. The aim of this study was to delineate the influence that biological sex and age exert on the retinal structural and ultrastructural changes in mice and to identify the age-related miRNA dysregulation profiles in the retina by gender. Experiments were undertaken on male and female Balb/c aged 24 months (approximately 75–85 years in humans) compared to the control (3 months). The retinas were analyzed by histology, transmission electron microscopy, and age-related miRNA expression profile analysis. Retinas of both sexes showed a steady decline in retinal thickness as follows: photoreceptor (PS) and outer layers (p < 0.01 for the aged male vs. control; p < 0.05 for the aged female vs. control); the inner retinal layers were significantly affected by the aging process in the males (p < 0.01) but not in the aged females. Electron microscopy revealed more abnormalities which involve the retinal pigment epithelium (RPE) and Bruch’s membrane, outer and inner layers, vascular changes, deposits of amorphous materials, and accumulation of lipids or lipofuscins. Age-related miRNAs, miR-27a-3p (p < 0.01), miR-27b-3p (p < 0.05), and miR-20a-5p (p < 0.05) were significantly up-regulated in aged male mice compared to the controls, whereas miR-20b-5p was significantly down-regulated in aged male (p < 0.05) and female mice (p < 0.05) compared to the respective controls. miR-27a-3p (5.00 fold; p < 0.01) and miR-27b (7.58 fold; p < 0.01) were significantly up-regulated in aged male mice vs. aged female mice, whereas miR-20b-5p (−2.10 fold; p < 0.05) was significantly down-regulated in aged male mice vs. aged female mice. Interestingly, miR-27a-3p, miR-27b-3p, miR-20a-5p, and miR-20b-5p expressions significantly correlated with the thickness of the retinal PS layer (p < 0.01), retinal outer layers (p < 0.01), and Bruch’s membrane (p < 0.01). Our results showed that biological sex can influence the structure and function of the retina upon aging, suggesting that this difference may be underlined by the dysregulation of age-related mi-RNAs.

miRMaster 2.0: multi-species non-coding RNA sequencing analyses at scale

“…The circRNA showing the most significant change between male and female mice was mmu_circ_0004351, with a fold change of 17.5 and an FDR adjusted Wilcoxon Mann-Whitney P -value of 4.6 × 10 –32 (Figure 4C ). miRNAs for which only 5% of the observed variance could be attributed to the mouse sex, were also partially differentially expressed, and have been previously reported in literature for single tissues or other species, such as mmu-miR-27a-3p and miR-27b-3p ( 44 , 45 ) and miR-16-5p and miR-21-3p ( 46 ).…”

Serum miRNA modulations indicate changes in retinal morphology

“…Some of these miRNAs have been identified previously in association with AMD, with miR-26a-5p and miR-27a-3p showing directional changes consistent with the literature (Grassmann et al, 2014;Szemraj et al, 2015) and let-7d-5p and miR-574-3p showing a directional change opposite to that reported in the literature (Ertekin et al, 2014;ElShelmani et al, 2020). Additionally, miR-27a-3p is a mediator of the inflammatory response (Zhang et al, 2018), and its overexpression was associated with increased oxidative stress and retinal damage (Ren et al, 2021), and increasing in aging mouse retinas (Hermenean et al, 2021). Interestingly, here we show that modulation in miR-26a-5p and miR-27a-3p correlated with histological features, specifically TUNEL + cell count and retinal volume, respectively.…”

Retinal Aging in 3× Tg-AD Mice Model of Alzheimer's Disease

“…Several age-dependent cellular and molecular changes have been described in mouse retinas, such as, photoreceptor mislocalization (Sugita et al, 2020 ) and vascular and RPE changes (Hermenean et al, 2021 ). Regarding metrics captured by OCT, although some studies have found age-dependent alterations in mouse retinas, such as auto-fluorescence (Ferdous et al, 2021 ) and scattering diversity (Gardner et al, 2020 ), these cannot be directly compared with our results.…”