Development and pathological changes of neurovascular unit regulated by hypoxia response in the retina

Reappearance of excentric persistent fetal vasculature stalk following laser treatment in a patient with type 1 retinopathy of prematurity

PURPOSE

In this report, we aim to present an unusual reappearance of hyaloidal artery remnant with atypical localization during the follow-up of an infant who underwent indirect laser photocoagulation for type 1 ROP.

METHODS

Retrospective case report.

RESULTS

We report a case of reappearance of an eccentrically located hyaloidal stalk in the macular area during the follow-up period, 2 weeks after laser photocoagulation for type 1 ROP subsequently progressed to cause foveal distortion, which is successfully removed with a lens-sparing vitrectomy.

CONCLUSIONS

To the best of our knowledge, there is no similar case in the literature. In the presence of fibrovascular proliferation extending into the vitreous, especially in premature infants, it should be kept in mind that this may be a reappearance of PFV and it may not always be located on the optic disc.

LncRNA MALAT 1/miR-625-3p/HIF-1α axis regulates the EMT of hypoxia-induced RPE cells by activating NF-κB/snail signaling

The retina may undergo structural and functional damage as a result of hypoxia, which could lead to permanent blindness. As competing endogenous RNAs (ceRNAs), lncRNAs are essential in eye disorders. The biological function of lncRNA MALAT 1 and its potential mechanisms in hypoxic-ischemic retinal diseases are still unknown. MALAT 1 and miR-625-3p expression alterations in hypoxia-treated RPE cells were examined using qRT-PCR. The target binding relationships between MALAT 1 and miR-625-3p, as well as between miR-625-3p and HIF-1α, were identified utilizing bioinformatics analysis and dual luciferase reporter assay. We observed that si-MALAT 1 and miR-625-3p mimic both reduced apoptosis and epithelial-mesenchymal transition (EMT) in hypoxic RPE cells, whereas si-MALAT 1 was reversed by miR-625-3p inhibitor. Further, we carried out a mechanistic investigation, and rescue assays demonstrated that MALAT 1 sponging miR-625-3p influenced HIF-1α expression and consequently took part in the NF-κB/Snail signaling pathway, which regulated apoptosis and EMT. In conclusion, our research had shown that the MALAT 1/miR-625-3p/HIF-1α axis drove the progression of hypoxic-ischemic retinal disorders and may serve as a promising predictive biomarker for their therapeutic and diagnostic targets.

Optical coherence tomography angiography characteristics of the retinal and optic disc morphology in prolactinoma

PURPOSE

To investigate changes in the retinal and optic disc (OD) morphology in prolactinoma patients without optical chiasmal compression and/or visual field defects using optical coherence tomography angiography (OCTA).

METHODS

In this cross-sectional imaging study, 16 consecutive prolactinoma patients (group 1, 32 eyes) and 15 age- and gender-matched healthy subjects (group 2, 30 eyes) underwent a thorough neuro-ophthalmological examination, which included testing for the presence of any intracranial compressive lesion that could cause optic neuropathy. Retinal morphological parameters, outer retinal and choriocapillaris flow areas, as well as OD vessel density (VD) and retinal nerve fiber layer (RNFL) thickness in for quadrants were then measured using OCTA.

RESULTS

Mean age (p = 0.537) and gender (p = 0.385) of participants in groups 1 and 2 did not differ significantly. The mean BCVA for both groups was 0.00 ± 0.00 logMAR. Microadenomas made up the majority of prolactinomas (87.1 %). All retinal morphological parameters in deep capillary plexus (excluding foveal VD) differed significantly between groups 1 and 2 (whole: p < 0.001, parafoveal: p = 0.021, and perifoveal: p < 0.001). Peripapillary RNFL thickness in temporal (p < 0.001), nasal (p = 0.010), and inferior (p = 0.007) quadrants also differed significantly between the two groups. Foveal deep (r = -0.304, p = 0.035) and choriocapillaris flow (r = -0.511, p = 0.008) were negatively correlated with tumor size at diagnosis.

CONCLUSIONS

Significant microvascular morphological changes, particularly in the deep retinal layer, as well as in the peripapillary RNFL thickness, were observed in prolactinoma patients. OCTA appears to be capable of detecting non-manifest circumpapillary and even intra-retinal microvascular changes even when there are no obvious signs of prolactinoma-related ocular complications caused by chiasmal compression.

Common Genes Involved in Autophagy, Cellular Senescence and the Inflammatory Response in AMD and Drug Discovery Identified via Biomedical Databases

Purpose

Retinal pigment epithelial cell autophagy dysfunction, cellular senescence, and the retinal inflammatory response are key pathogenic factors in age-related macular degeneration (AMD), which has been reviewed in our previously work in 2019. This study aims to identify genes collectively involved in these three biological processes and target drugs in AMD.

Methods

The pubmed2ensembl database was used to perform text mining. The GeneCodis database was applied to analyze gene ontology biological process and the KEGG pathway. The STRING database was used to analyze protein–protein interaction analysis and hub genes were identified by the Cytoscape software. The Drug Gene Interaction Database was used to perform drug–gene interactions.

Results

We identified 62 genes collectively involved in AMD, autophagy, cellular senescence, and inflammatory response, 19 biological processes including 42 genes, 11 enriched KEGG pathways including 37 genes, and 12 hub genes step by step via the above biomedical databases. Finally, five hub genes (IL-6, VEGF-A, TP53, IL-1β, and transforming growth factor [TGF]-β1) and their specific interaction modes were identified, corresponding with 24 target drugs with therapeutic potential for AMD.

Conclusions

IL-6, VEGF-A, TP53, IL-1β, and TGF-β1 are pivotal in autophagy, cellular senescence, and the inflammatory response in AMD, corresponding with 24 drugs with therapeutic potential for AMD, providing definite molecular mechanisms for further research and new possibilities for AMD treatment in the future.

Translational Relevance

IL-6, VEGF-A, TP53, IL-1β, and TGF-β1 may be new targets for AMD gene therapy and drug development.

Diabetic Retinopathy: The Role of Mitochondria in the Neural Retina and Microvascular Disease

Diabetic retinopathy (DR), a common chronic complication of diabetes mellitus and the leading cause of vision loss in the working-age population, is clinically defined as a microvascular disease that involves damage of the retinal capillaries with secondary visual impairment. While its clinical diagnosis is based on vascular pathology, DR is associated with early abnormalities in the electroretinogram, indicating alterations of the neural retina and impaired visual signaling. The pathogenesis of DR is complex and likely involves the simultaneous dysregulation of multiple metabolic and signaling pathways through the retinal neurovascular unit. There is evidence that microvascular disease in DR is caused in part by altered energetic metabolism in the neural retina and specifically from signals originating in the photoreceptors. In this review, we discuss the main pathogenic mechanisms that link alterations in neural retina bioenergetics with vascular regression in DR. We focus specifically on the recent developments related to alterations in mitochondrial metabolism including energetic substrate selection, mitochondrial function, oxidation-reduction (redox) imbalance, and oxidative stress, and critically discuss the mechanisms of these changes and their consequences on retinal function. We also acknowledge implications for emerging therapeutic approaches and future research directions to find novel mitochondria-targeted therapeutic strategies to correct bioenergetics in diabetes. We conclude that retinal bioenergetics is affected in the early stages of diabetes with consequences beyond changes in ATP content, and that maintaining mitochondrial integrity may alleviate retinal disease.

The role of cldnh during the early retinal development in zebrafish

Claudin-3, an integral component of tight junction, has recently been shown to be expressed in retinal ganglion cells, retinal pigment cells, and retinal vascular endothelial cells. However, the role of claudin-3 in the development of the neural retina and its vessels remains undefined. This study aimed to investigate the role of zebrafish claudin-h (cldnh), the closest ortholog of mouse and human claudin-3, in the development of the neural retina and its vessels. Cldnh levels in green fluorescent protein transgenic zebrafish were genetically manipulated by cldnh morpholino oligonucleotide (MO) and cldnh mRNA to investigate gene function. The expression of cldnh was analyzed using polymerase chain reaction and immunofluorescence staining. The altered morphological, cellular and molecular events in the cldnh MO-morphant eyes were detected using hematoxylin-eosin staining, fluorescent dye injection, confocal in vivo imaging, BrdU labeling, TUNEL assay, RNA sequencing, and Western blot. We demonstrated that the cldnh protein was expressed in the neural retina and the hyaloid vessel which is the predecessor of the retinal vessel in zebrafish. Cldnh knockdown delayed lamination of the neural retina and reduced its thickness, which might be associated with the downregulation of the retinal development-related genes of atoh7, pcdh17, crx, neurod1, insm1a, sox9b and cdh11, and the upregulation of the cell cycle and apoptosis-associated genes of tp53, cdkn1a and casp8. Cldnh knockdown also reduced the density and interrupted the lumenization of the hyaloid vessels, which might be owing to the downregulation of the vessel formation-related genes of hlx1 and myl7. In conclusion, cldnh was required for the normal development of the neural retina and its vessels in zebrafish, providing a basis for elucidating its role in the pathogenesis of retinal vascular or inflammatory diseases.

Retinal microvasculature in pituitary adenoma patients: is optical coherence tomography angiography useful?

PURPOSE

To examine retinal vascular changes in the peripapillary and macular areas in patients with pituitary adenoma (PA) using optical coherence tomography angiography (OCTA).

METHODS

Cross-sectional, retrospective study of 17 consecutive PA patients and 16 healthy subjects. All patients underwent a neuro-ophthalmological examination to assess the presence of optic neuropathy (ON). Static automated perimetry (SAP), macular and optic disc structural OCT [retinal nerve fibre layer (RNFL) and ganglion cell complex (GCC) thicknesses] and OCTA were performed. Pituitary adenoma (PA) patients with ON were compared to those without ON and to healthy subjects.

RESULTS

Optic neuropathy (ON) was found in 16 eyes of nine PA patients. Peripapillary vessel density (ppVD) and macular vessel density (VD) in the superficial vascular plexus were significantly decreased in PA eyes with ON, compared to healthy eyes (45.21 ± 5.69 versus 50.52 ± 2.14% and 43.79 ± 5.03% versus 48.96 ± 2.94%, respectively). No significant difference in VD was observed in the macular deep vascular complex (DVC) between groups. Pituitary adenoma (PA) patients with ON had a mean ppVD reduction by 10.51% compared to healthy subjects. RNFL and GCC thicknesses were significantly reduced in PA eyes with ON compared to the other groups. Peripapillary VD (ppVD) significantly correlated with RNFL thickness and SAP mean deviation.

CONCLUSIONS

Optical coherence tomography angiography showed a significant decrease in ppVD and superficial macular VD in PA eyes with ON compared to healthy eyes, according to RNFL and GCC thinning. Together with the absence of DVC alterations, it may provide further insights into neurovascular coupling.

From Rust to Quantum Biology: The Role of Iron in Retina Physiopathology

Iron is essential for cell survival and function. It is a transition metal, that could change its oxidation state from Fe²⁺ to Fe³⁺ involving an electron transfer, the key of vital functions but also organ dysfunctions. The goal of this review is to illustrate the primordial role of iron and local iron homeostasis in retinal physiology and vision, as well as the pathological consequences of iron excess in animal models of retinal degeneration and in human retinal diseases. We summarize evidence of the potential therapeutic effect of iron chelation in retinal diseases and especially the interest of transferrin, a ubiquitous endogenous iron-binding protein, having the ability to treat or delay degenerative retinal diseases.

Effects of Hyperoxia on the Refraction in Murine Neonatal and Adult Models

Whether hyperoxia affects the refraction in neonatal and adult mice is unknown. The mice exposed to 85% oxygen at postnatal 8 days (P8d) for 3 days and the mice exposed to normal air were assigned to the neonatal hyperoxia and normoxia groups, respectively. The refraction, the corneal curvature radius (CR) and the axial length (AL) were measured at P30d and P47d. Postnatal 6 weeks (P6w) adult mice were divided into the adult hyperoxia and normoxia groups. These parameters were measured before oxygen exposure, after 1 and 6 weeks, and every 7 weeks. The lens elasticity was measured at P7w and P26w by enucleation. The neonatal hyperoxia group showed a significantly larger myopic change than the neonatal normoxia group (P47d −6.56 ± 5.89 D, +4.11 ± 2.02 D, p < 0.001), whereas the changes in AL were not significantly different (P47d, 3.31 ± 0.04 mm, 3.31 ± 0.05 mm, p = 0.852). The adult hyperoxia group also showed a significantly larger myopic change (P12w, −7.20 ± 4.09 D, +7.52 ± 2.54 D, p < 0.001). The AL did not show significant difference (P12w, 3.44 ± 0.03 mm, 3.43 ± 0.01 mm, p = 0.545); however, the CR in the adult hyperoxia group was significantly smaller than the adult normoxia group (P12w, 1.44 ± 0.03 mm, 1.50 ± 0.03 mm, p = 0.003). In conclusion, hyperoxia was demonstrated to induce myopic shift both in neonatal and adult mice, which was attributed to the change in the CR rather than the AL. Elucidation of the mechanisms of hyperoxia and the application of this result to humans should be carried out in future studies.

Heat Shock Proteins Regulatory Role in Neurodevelopment

Heat shock proteins (Hsps) are a large family of molecular chaperones that are well-known for their roles in protein maturation, re-folding and degradation. While some Hsps are constitutively expressed in certain regions, others are rapidly upregulated in the presence of stressful stimuli. Numerous stressors, including hyperthermia and hypoxia, can induce the expression of Hsps, which, in turn, interact with client proteins and co-chaperones to regulate cell growth and survival. Such interactions must be tightly regulated, especially at critical points during embryonic and postnatal development. Hsps exhibit specific patterns of expression consistent with a spatio-temporally regulated role in neurodevelopment. There is also growing evidence that Hsps may promote or inhibit neurodevelopment through specific pathways regulating cell differentiation, neurite outgrowth, cell migration, or angiogenesis. This review will examine the regulatory role that these individual chaperones may play in neurodevelopment, and will focus specifically on the signaling pathways involved in the maturation of neuronal and glial cells as well as the underlying vascular network.

Pax6 regulation of Sox9 in the mouse retinal pigmented epithelium controls its timely differentiation and choroid vasculature development

The synchronized differentiation of neuronal and vascular tissues is crucial for normal organ development and function, although there is limited information about the mechanisms regulating the coordinated development of these tissues. The choroid vasculature of the eye serves as the main blood supply to the metabolically active photoreceptors, and develops together with the retinal pigmented epithelium (RPE). Here, we describe a novel regulatory relationship between the RPE transcription factors Pax6 and Sox9 that controls the timing of RPE differentiation and the adjacent choroid maturation. We used a novel machine learning algorithm tool to analyze high resolution imaging of the choroid in Pax6 and Sox9 conditional mutant mice. Additional unbiased transcriptomic analyses in mutant mice and RPE cells generated from human embryonic stem cells, as well as chromatin immunoprecipitation and high-throughput analyses, revealed secreted factors that are regulated by Pax6 and Sox9. These factors might be involved in choroid development and in the pathogenesis of the common blinding disease: age-related macular degeneration (AMD).

No evidence for loss of short-wavelength sensitive cone photoreceptors in normal ageing of the primate retina

In old world primates including humans, cone photoreceptors are classified according to their maximal sensitivity at either short (S, blue), middle (M, green) or long (L, red) wavelengths. Colour discrimination studies show that the S-cone pathway is selectively affected by age and disease, and psychophysical models implicate their loss. Photoreceptors have high metabolic demand and are susceptible to age or disease-related losses in oxygen and nutrient supply. Hence 30% of rods are lost over life. While comparable losses are not seen in cones, S-cones comprise less than 10% of the cone population, so significant loss would be undetected in total counts. Here we examine young and aged primate retinae stained to distinguish S from M/L-cones. We show there is no age-related cone loss in either cone type and that S-cones are as regularly distributed in old as young primates. We propose that S-cone metabolism is less flexible than in their M/L counterparts, making them more susceptible to deficits in normal cellular function. Hypoxia is a feature of the ageing retina as extracellular debris accumulates between photoreceptors and their blood supply which likely impacts S-cone function. However, that these cells remain in the ageing retina suggests the potential for functional restoration.