Retinal Tissue Research Articles

Pathomorphological Changes of the Retina in Chronic Intraocular Pressure Increase

Glaucoma is one of the most unfavorable neurodegenerative diseases of the eye. However, the etiology and pathogenesis of glaucoma have not been fully studied enough. Thus, for example, the issue of the primacy of damage to the fundus structures in the development of glaucomatous optic neuropathy remains debatable.This review presents a modern view of the main pathomorphological changes in the retina in chronically elevated intraocular pressure (IOP). The analysis of structural changes in various layers of retinal tissue, primarily retinal ganglion cells in glaucoma, is carried out. Attention is focused on the role of various pathogenetic mechanisms in the occurence and progression of dystrophic changes in the retina with an increase of IOP. The need for a comprehensive analysis of structural, functional and hemodynamic parameters in each specific clinical case is emphasized, which helps to increase the sensitivity of new methods for diagnosing glaucoma and optimize the treatment of the disease.

Level-set based adaptive-active contour segmentation technique with long short-term memory for diabetic retinopathy classification.

Diabetic Retinopathy (DR) is a major type of eye defect that is caused by abnormalities in the blood vessels within the retinal tissue. Early detection by automatic approach using modern methodologies helps prevent consequences like vision loss. So, this research has developed an effective segmentation approach known as Level-set Based Adaptive-active Contour Segmentation (LBACS) to segment the images by improving the boundary conditions and detecting the edges using Level Set Method with Improved Boundary Indicator Function (LSMIBIF) and Adaptive-Active Counter Model (AACM). For evaluating the DR system, the information is collected from the publically available datasets named as Indian Diabetic Retinopathy Image Dataset (IDRiD) and Diabetic Retinopathy Database 1 (DIARETDB 1). Then the collected images are pre-processed using a Gaussian filter, edge detection sharpening, Contrast enhancement, and Luminosity enhancement to eliminate the noises/interferences, and data imbalance that exists in the available dataset. After that, the noise-free data are processed for segmentation by using the Level set-based active contour segmentation technique. Then, the segmented images are given to the feature extraction stage where Gray Level Co-occurrence Matrix (GLCM), Local ternary, and binary patterns are employed to extract the features from the segmented image. Finally, extracted features are given as input to the classification stage where Long Short-Term Memory (LSTM) is utilized to categorize various classes of DR. The result analysis evidently shows that the proposed LBACS-LSTM achieved better results in overall metrics. The accuracy of the proposed LBACS-LSTM for IDRiD and DIARETDB 1 datasets is 99.43% and 97.39%, respectively which is comparably higher than the existing approaches such as Three-dimensional semantic model, Delimiting Segmentation Approach Using Knowledge Learning (DSA-KL), K-Nearest Neighbor (KNN), Computer aided method and Chronological Tunicate Swarm Algorithm with Stacked Auto Encoder (CTSA-SAE).

Peripheral monocytes and neutrophils promote photoreceptor cell death in an experimental retinal detachment model

Photoreceptor cell death and immune cell infiltration are two major events that contribute to retinal degeneration. However, the relationship between these two events has not been well delineated, primarily because of an inadequate understanding of the immunological processes involved in photoreceptor degeneration, especially that of peripheral leukocytes that infiltrate the subretinal space and retinal tissues. In this work, we characterized the role of leukocyte infiltration within the detached retina. We observed that CD45+ CD11b+ Ly6G+ neutrophils and CD45+ CD11b+ Ly6G− Ly6C+ monocytes are the predominant peripheral immune cell populations that infiltrate the retinal and subretinal space after detachment. Selective depletion of monocytes or neutrophils using cell-specific targeting is neuroprotective for photoreceptors. These results indicate that peripheral innate immune cells contribute to photoreceptor degeneration, and targeting these immune cell populations could be therapeutic during retinal detachment.

Exome sequencing reveals PPEF2 variant associated with high myopia

High myopia (HM) is a serious blinding eye disease, and genetic factors play an important role in the development of HM. In this study, whole exome sequencing (WES) was used to identify a novel variant c.A875G of the PPEF2 for a large Uyghur family with nonsyndromic HM. The variant was verified to cosegregate with HM in the family using Sanger sequencing. Another novel variant c.1959C > G in PPEF2 was identified in one of 100 sporadic cases of HM by multiplex PCR targeted amplicon sequencing (MTA-seq). The Ppef2 was verified that mainly expressed in the retinal pigment epithelium (RPE), choroid and retina tissues. Immunofluorescence (IF) and immunohistochemistry (IHC) assays showed that the PPEF2 was strongly expressed in the inner segment layer formed by photoreceptor protrusions, as well as in the outer nuclear layer. Compared with the wild-type, the c.A875G resulted in reduced protein levels but had no effect on protein subcellular localization in cells. In addition, the c.A875G variant resulted in a decreased migratory and proliferative capacity but promoted apoptosis in cells. In summary, PPEF2 was identified as a novel HM-causing gene, and this variant in PPEF2 might cause HM by regulating the migration, proliferation and apoptosis of myopia-related cells.

The TRIM21-FOXD1-BCL-2 axis underlies hyperglycaemic cell death and diabetic tissue damage

Chronic hyperglycaemia is a devastating factor that causes diabetes-induced damage to the retina and kidney. However, the precise mechanism by which hyperglycaemia drives apoptotic cell death is incompletely known. Herein, we found that FOXD1, a FOX family transcription factor specifically expressed in the retina and kidney, regulated the transcription of BCL-2, a master regulator of cell survival. Intriguingly, the protein level of FOXD1, which responded negatively to hyperglycaemic conditions, was controlled by the TRIM21-mediated K48-linked polyubiquitination and subsequent proteasomal degradation. The TRIM21-FOXD1-BCL-2 signalling axis was notably active during diabetes-induced damage to murine retinal and renal tissues. Furthermore, we found that tartary buckwheat flavonoids effectively reversed the downregulation of FOXD1 protein expression and thus restored BCL-2 expression and facilitated the survival of retinal and renal tissues. In summary, we identified a transcription factor responsible for BCL-2 expression, a signalling axis (TRM21-FOXD1-BCL-2) underlying hyperglycaemia-triggered apoptosis, and a potential treatment for deleterious diabetic complications.

IL1R2 promotes retinal angiogenesis to participate in retinopathy of prematurity by activating the HIF1α/PFKFB3 pathway

Retinopathy of prematurity (ROP) is the leading cause of blindness in children, but there is no safe and effective treatment available. Interleukin-1 receptor type 2 (IL1R2) acts as a decoy receptor for IL-1 may affect ROP progression. This study aimed to investigate the role of IL1R2 in ROP. A microglial cell model was established under hypoxia conditions and co-cultured with choroidal endothelial cells, while an oxygen-induced retinopathy (OIR) model was also established. Microglial activation and IL1R2 levels in retinal tissues were analyzed using immunofluorescence assay. Endothelial cell migration was evaluated by Transwell assay and scratch test, angiogenesis was assessed using ELISA and tube formation assay, and proliferation was evaluated by EdU assay. The HIF1α/PFKFB3 pathway was analyzed by western blot. We observed that IL1R2 expression was predicted to be upregulated in ROP and was increased in hypoxia-treated BV2 cells. Additionally, IL1R2 levels were upregulated in the retinal tissues of OIR mice and correlated with microglial activation. In vitro experiments, we found that hypoxia promoted endothelial cell migration, angiogenesis, proliferation, and activated the HIF1α/PFKFB3 pathway, which were rescued by IL1R2 knockdown. Moreover, NHWD-870 (a HIF1α/PFKFB3 pathway inhibitor) suppressed endothelial cell migration, angiogenesis, and proliferation induced by IL1R2 overexpression. In conclusion, IL1R2 facilitates the migration, angiogenesis, and proliferation of choroidal endothelial cells by activating the HIF1α/PFKFB3 pathway to regulate ROP progression.

HAGLR, stabilized by m6A modification, triggers PTEN-Akt signaling cascade-mediated RPE cell pyroptosis via sponging miR-106b-5p.

Consistent hyperglycaemia on retinal microvascular tissues is recognized as a vital inducer of diabetic retinopathy (DR) pathogenesis. In view of the essential functionality of long noncoding RNAs (lncRNAs) in multiple human diseases, we aim to figure out the exact role and underlying mechanisms of lncRNA HOXD Cluster Antisense RNA 1 (HAGLR) in DR pathogenesis. Serum specimens from patients with proliferative DR and healthy volunteers were collected for measuring HAGLR levels. Human primary retinal pigment epithelium (HRPE) cells kept in high glucose (HG) condition were applied to simulating hyperglycaemia of DR pathology in vitro. Cell proliferation, apoptosis, either pyroptosis was assess using Cell Counting Kit-8 TUNEL, flow cytometry, and enzyme-linked immunoassay assays. Bioinformatics analysis was subjected to examine the interaction between HAGLR and N6-methyladenosine (m6A)-bind protein IGF2BP2, as determined using RNA immunoprecipitation and RNA pull-down. Luciferase reporter assay was performed to assess the HAGLR-miR-106b-5p-PTEN axis. Levels of pyroptosis-associated biomarkers were detected using western blotting. Aberrantly overexpressed HAGLR was uncovered in the serum samples of DR patients and HG-induced HRPE cells, of which knockdown attenuated HG-induced cytotoxic impacts on cell apoptosis and pyroptosis. Whereas, reinforced HAGLR further aggravated these effects. IGF2BP2 positively regulated HAGLR in a m6A-dependent manner. HAGLR served as a sponge for miR-106b-5p to upregulate PTEN, thereby activating Akt signaling cascade. Rescue assays demonstrated that PTEN overexpression abolished the inhibition of silenced HAGLR on pyroptosis in HRPE cells. HAGLR, epigenetically modified by IGF2BP2 in an m6A-dependent manner, functioned as a sponge for miR-106b-5p, thereby activating PTEN/Akt signaling cascade to accelerate DR pathology.

Multi-Wavelength Photobiomodulation Ameliorates Sodium Iodate-Induced Age-Related Macular Degeneration in Rats.

Age-related macular degeneration (AMD) is a global health challenge. AMD causes visual impairment and blindness, particularly in older individuals. This multifaceted disease progresses through various stages, from asymptomatic dry to advanced wet AMD, driven by various factors including inflammation and oxidative stress. Current treatments are effective mainly for wet AMD; the therapeutic options for dry AMD are limited. Photobiomodulation (PBM) using low-energy light in the red-to-near-infrared range is a promising treatment for retinal diseases. This study investigated the effects of multi-wavelength PBM (680, 780, and 830 nm) on sodium iodate-induced oxidatively damaged retinal tissue. In an in vivo rat model of AMD induced by sodium iodate, multi-wavelength PBM effectively protected the retinal layers, reduced retinal apoptosis, and prevented rod bipolar cell depletion. Furthermore, PBM inhibited photoreceptor degeneration and reduced retinal pigment epithelium toxicity. These results suggest that multi-wavelength PBM may be a useful therapeutic strategy for AMD, mitigating oxidative stress, preserving retinal integrity, and preventing apoptosis.

NDRG2 alleviates photoreceptor apoptosis by regulating the STAT3/TIMP3/MMP pathway in mice with retinal degenerative disease.

Photoreceptor apoptosis is the main pathological feature of retinal degenerative diseases; however, the underlying molecular mechanism has not been elucidated. Recent studies have shown that N-myc downstream regulated gene 2 (NDRG2) exerts a neuroprotective effect on the brain and spinal cord. In addition, our previous studies have confirmed that NDRG2 is expressed in mouse retinal photoreceptors and counteracts N-methyl-N-nitrosourea (MNU)-induced apoptosis. However, the underlying molecular mechanism remains unclear. In this study, we observed that the expression of NDRG2 was not only significantly inhibited in photoreceptors after MNU treatment but also after hydrogen peroxide treatment, and photoreceptor apoptosis was alleviated or aggravated after overexpression or knockdown of NDRG2 in the 661W photoreceptor cell line, respectively. The apoptosis inhibitor Z-VAD-FMK rescued photoreceptor apoptosis induced by MNU after NDRG2 knockdown. Next, we screened and identified tissue inhibitor of metalloproteinases 3 (TIMP3) as the downstream molecule of NDRG2 in 661W cells by using quantitative real-time polymerase chain reaction. TIMP3 exerts a neuroprotective effect by inhibiting the expression of matrix metalloproteinases (MMPs). Subsequently, we found that signal transducer and activator of transcription 3 (STAT3) mediated the NDRG2-associated regulation of TIMP3. Finally, we overexpressed NDRG2 in mouse retinal tissues by intravitreally injecting an adeno-associated virus with mouse NDRG2 in vivo. Results showed that NDRG2 upregulated the expression of phospho-STAT3 (p-STAT3) and TIMP3, while suppressing MNU-induced photoreceptor apoptosis and MMP expression. Our findings revealed how NDRG2 regulates the STAT3/TIMP3/MMP pathway and uncovered the molecular mechanism underlying its neuroprotective effect on mouse retinal photoreceptors.

Method to Regulate Monocyte Function by Silencing HIF-1α mRNA in a Model of Retinal Neovascularization.

Circulating monocytes migrate into the retina in response to inflammation and neovascularization. Furthermore, under inflammatory conditions such as diabetes, healthy monocytes become activated in the circulation. However, the contribution of activated monocytes to neovascularization is largely unknown. HIF-1α has been shown to contribute to the pathogenesis of neovascularization. We describe here the synthesis of a hybrid nanomaterial for targeted delivery and gene silencing in activated monocytes that are associated with pathological neovascularization. To test the gene silencing ability of AS-shRNA-lipids in vitro, we used the probe to inhibit HIF-1α mRNA induced in mouse monocytes by exposing them to hypoxia. In addition, we tested AS-shRNA-lipids for inhibition of neovascularization in vivo using the mouse model of oxygen-induced retinopathy (OIR). Significant reduction of neovascularization was achieved in mouse OIR by targeting activated monocytes using intraperitoneal injections of AS-shRNA-lipids. Expression of HIF-1α and CD14 mRNA were both inhibited in circulating cells, suggesting normalization of the activated monocytes in P17 OIR animals treated with AS-shRNA-lipids. We hypothesized that inhibition of HIF-1α mRNA in activated monocytes may have a direct impact on VEGF expression in the retinal tissues in vivo. We observed that VEGF mRNA expression was inhibited in P17 retinal tissues after systemic treatment with HIF-1α-targeted AS-shRNA-lipids. These findings may provide a framework for a strategy to inhibit retinal neovascularization by targeting circulating activated monocytes.

Deletion of IFT20 exclusively in the RPE ablates primary cilia and leads to retinal degeneration.

Vision impairment places a serious burden on the aging society, affecting the lives of millions of people. Many retinal diseases are of genetic origin, of which over 50% are due to mutations in cilia-associated genes. Most research on retinal degeneration has focused on the ciliated photoreceptor cells of the retina. However, the contribution of primary cilia in other ocular cell types has largely been ignored. The retinal pigment epithelium (RPE) is a monolayer epithelium at the back of the eye intricately associated with photoreceptors and essential for visual function. It is already known that primary cilia in the RPE are critical for its development and maturation; however, it remains unclear whether this affects RPE function and retinal tissue homeostasis. We generated a conditional knockout mouse model, in which IFT20 is exclusively deleted in the RPE, ablating primary cilia. This leads to defective RPE function, followed by photoreceptor degeneration and, ultimately, vision impairment. Transcriptomic analysis offers insights into mechanisms underlying pathogenic changes, which include transcripts related to epithelial homeostasis, the visual cycle, and phagocytosis. Due to the loss of cilia exclusively in the RPE, this mouse model enables us to tease out the functional role of RPE cilia and their contribution to retinal degeneration, providing a powerful tool for basic and translational research in syndromic and non-syndromic retinal degeneration. Non-ciliary mechanisms of IFT20 in the RPE may also contribute to pathogenesis and cannot be excluded, especially considering the increasing evidence of non-ciliary functions of ciliary proteins.

Hyperspectral analysis of amyloid beta (Aβ) evolutional changes in preclinical to late‐stage Alzheimer’s disease using matched brain and retinal tissue

AbstractBackgroundAlzheimer’s disease (AD) is a progressive, degenerative brain disorder that leads to cognitive impairment and eventually death. It is marked by buildup of abnormal amyloid aggregates (Aβ) in the brain. This study aimed to elucidate the neuropathologic sequence and corresponding [RetiSpec] hyperspectral signals of Aβ evolutional changes in preclinical to late‐stage AD using retinal and brain samples.MethodWe used brain‐ and retina‐matched human tissue samples from the NIH Brain Bank at Johns Hopkins. Study groups included: No AD neuropathologic change with negative AD neuropathology (n = 15); Low‐level AD neuropathologic change with positive AD neuropathology (n = 15); High level AD neuropathologic change with positive AD neuropathology (n = 15). To validate retinal hyperspectral imaging (rHSI) detection of Aβ in these retinal samples, we quantified Aβ oligomers (AβOs) in human retinal tissue. Immunohistochemistry was performed. We used humanized, affinity‐matured, IgG2 mAβ selective biotinylated antibody (ACU‐193) to detect soluble AβOs in retinal and brain tissues followed by objective quantification of ACU193 retinal staining by performing annotations and data extraction using QuPath software. One‐way ANOVA and t‐tests were performed to compare between controls and AD stages.ResultWhen assessing ACU193 staining present from retinal tissue samples, we observed 29‐53% retinal tissue area positivity in controls and 15‐72% retinal tissue area positivity in the AD group. Level of AD pathology demonstrated an effect on the rHSI spectra (450‐600nm) in regions near the optic disc and the ventral periphery: intermediate AD pathology showed the strongest rHSI signature (decrease in optical transmittance) followed by high, then low AD pathology samples. Correlation of the Braak neurofibrillary tangle stage and ΔOD offered a Pearson r score of 0.79 (p = 0.004).ConclusionThis study was the first to assess and quantify AβOs in clinically, neuropathologically, and hyperspectrally characterized postmortem matched brain and retinal tissues. Progression of well‐established neuropathologically classified AD stages (e.g Braak) may correlate with retinal AβO levels measured using rHSI. Certain retina regions that share nervous tissue with the brain (optic disc, periphery) are likely more sensitive to rHSI‐mediated detection of AD pathology. Larger samples are needed to comprehensively assess and quantify retinal AβOs.

Microbial infection and associated inflammasome in the retina of Alzheimer’s disease patients

AbstractBackgroundRecent advances in Alzheimer’s disease (AD) research revealed that AD pathology is not confined to the brain but also occur in the neurosensory retina. Data have further suggested parallels between retinal and brain AD biomarkers. While the exact etiology of AD pathogenesis is undefined, an emerging theory has linked AD with microbial infection as a plausible cause for AD progression. The presence of several microbes including Chlamydia pneumoniae (Cp), Borrelia burgdorferi, Porphyromonas gingivalis, and Toxoplasma gondii have been reported in the post‐mortem brain of AD patients and murine models. However, the existence and role of microbial infection in AD retina has never been studied.MethodWe employed a range of histological, biochemical, and genetic techniques to detect bacterial infection and other associated biomarkers in postmortem retinas of patients with mild cognitive impairment (MCI) or AD dementia, compared to retinas from age‐matched individuals who displayed normal cognition (NC). We assessed the presence and burden of Cp and correlated with gliosis, inflammasome, and apoptosis markers.ResultWe discovered the presence of Cp inclusions in postmortem retinas of patients with MCI and AD as compared to age‐ and sex‐matched NC individuals. Our experimental evidence revealed Cp‐infected retinal neuronal cells in AD patients, with no increase in retinal Cp infection in MCI versus CN and a significant 4‐fold increase in of Cp immunoreactivity in retinas of AD patients versus MCI and CN subjects. These data possibly indicate that Cp infection mainly occur during the dementia phase of AD and is less observable at the early functional impairment stages of AD. Retinal microglia were found to aggregate around and engulf Cp‐infected cells. Alongside Cp infection, retinal tissues from MCI and AD patients exhibited increased NLRP3 inflammasome and gliosis. Our data suggest Cp‐triggered inflammasome activation, that can lead to neuronal degeneration. We further found a relationship between the severity of retinal Cp infection and brain pathology; retinal Cp burden was associated with brain neurofibrillary tangles, neuropil threads, Braak stage.ConclusionCp‐triggered chronic inflammation could be a detrimental process leading to retinal degeneration in AD, suggesting potential new therapeutic avenues involving early antibiotic treatment or inflammasome attenuation.

Visualizing Tau Tangles in AD Retina with a BODIPY‐based Fluorescent Ligand

AbstractBackgroundAlzheimer’s disease (AD) is a neurodegenerative disease responsible for most cases of senile dementia. Despite numerous studies, there are no effective therapies or significant progress in symptom progression. To develop a therapeutic strategy, research has focused on accurate diagnostic methods. Coupled units of hyperphosphorylated protein (P‐Tau) and total‐Tau monomers (t‐Tau) are reliable biomarkers for AD. Early identification of neurofibrillary tangles (NFTs) in retinal tissue is a promising diagnostic tool. The development of highly specific Tau fluorophores has been achieved through the construction of a computational model of TAU oligomers.MethodsThe construction of the highly specific Tau fluorophore BT‐1 (Soloperto et al., 2021) consisting of a BODIPY‐based probe showed excellent photophysical properties and high selectivity allowing in vitro imaging of hyperphosphorylated tau protein filaments with minimal background noise. Delivery to living iPSC derived retinal cells was achieved by identifying a class of delivery cargoes among ferritin proteins, natural nanocages that can embed small molecules and enter human cells expressing the transferrin receptor.ResultsBT‐1 colocalizes with phosphorylated and oligomeric tau in AD retinal slices. Loading the ferritin nanocage with the fluorescent probe BT‐1 generated a unique formulation for the delivery of the fluorescent probe to retinal tissue.ConclusionThe use of ferritin nanocages loaded with the fluorescent probe BT‐1 provides a promising method for the specific identification of NFTs in retinal tissue for the clinical diagnosis of AD. The encapsulation of other substrates in ferritin nanocages has potential applications in nanomedicine.

Fukushimura Brain Bank ‐Nursing home based brainbank project in Japan‐

AbstractBackgroundThe Fukushimura (welfare village), located in Toyohashi city, Japan, is a unique complex of various nursing home facilities including dementia homes, Day‐care houses, homes for disabled and mentally retarded, and the Fukushimura Hospital. This village is totally managed by private sector, the Sawarabi Medical Cooperative. About 800 elderly people reside in this area. The hospital plays a pivotal role within the village and acts as the central facility for each nursing homes.Fukushimura BrainBank (FBB) was established in 1990. The neuropathological investigation of FBB was initially conducted by Kenji Kosaka, who reported cortical Lewy bodies first. Our research institute was approved in 2004 by the Ministry of Education, Culture, Sports, Science and Technology, as one of the non‐governmental institutes which is permitted to apply for governmental grants.MethodAll the medical records and radiological images from the nursing home to hospital are stored in the research institute and accessible for the researchers to evaluate the psychological symptoms observed by carers in the long duration of the disease. The brain MRI of 1.5 Tesla was used for evaluating 3D‐volumetric T1WI and diffusion tensor imaging.For collecting CNS specimens, the brains are separated into two hemispheres, one for neuropathological analyses with using several antibodies for beta‐amyloid, phosphorylated tau, alpha‐ synuclein, and TDP‐43. Modified gallyas‐silver staining is applied for evaluating argyrophilic grain disease. The other hemispheres are stored for frozen sections. Retinal tissue is collected with optional consent.ResultThe number of autopsy became over 30 cases per year. Most of the patients had dementia. Of note, geriatric residents with mentally retardation or cerebral palsy from childhood were included. At the end of 2022, more than 800 of frozen brains with detailed medical record are stored in FBB and readily available for research. The neuropathology database share the same coding system for Japanese Brain Bank Network for Neuroscience Research (JBBNNR).ConclusionThe challenge of FBB will play a unique and important role to clarify cliniconeuropathological correlation of the nursing home residential with various geriatric conditions with 3D(Disability, Dementia, and Developmental disorders).

Diabetic Müller-Glial-Cell-Specific Il6ra Knockout Mice Exhibit Accelerated Retinal Functional Decline and Thinning of the Inner Nuclear Layer.

Interleukin-6 (IL-6) is implicated in the pathology of diabetic retinopathy (DR). IL-6 trans-signaling via soluble IL-6 receptor (IL-6R) is primarily responsible for its pro-inflammatory functions, whereas cis-signaling via membrane-bound IL-6R is anti-inflammatory. Using a Müller-glial-cell-specific Il6ra-/- mouse, we examined how loss of IL-6 cis-signaling in Müller glial cells (MGCs) affected retinal thinning and electroretinography (ERG) response over 9months of diabetes. Diabetes was induced in wildtype and knockout mice with streptozotocin (40mg/kg, daily for 5days). Spectral domain optical coherence tomography (SD-OCT), ERG, and fundoscopy/fluorescein angiography (FA) were assessed at 2, 6, and 9months of diabetes. MGCs and bipolar neurons were examined in retinal tissue sections by immunofluorescence. Diabetic MGC Il6ra-/- mice had significantly thinner retinas than diabetic wildtype mice at 2 (-7.6µm), 6 (-12.0µm), and 9months (-5.0µm) of diabetes, as well as significant thinning of the inner nuclear layer (INL). Diabetic MGC Il6ra-/- mice also showed a reduction in scotopic B-wave amplitude and B-wave/A-wave ratio earlier than wildtype diabetic mice. In retinal sections, we found a decrease in bipolar neuronal marker PKCα only in diabetic MGC Il6ra-/- mice, which was significantly lower than both controls and diabetic wildtype mice. Glutamine synthetase, a Müller cell marker, was reduced in both wildtype and MGC Il6ra-/- diabetic mice compared to their respective controls. IL-6 cis-signaling in MGCs contributes to maintenance of the INL in diabetes, and loss of the IL-6 receptor reduces MGC-mediated neuroprotection of bipolar neurons in the diabetic retina.

Critical Next Steps for Translation of Preclinical and Ex Vivo Human Retinal Studies for Alzheimer’s Disease Diagnosis

AbstractRetinal ganglion cells are part of the CNS and as such many years of research has focused on determining and documenting how changes in retinal cells and layers may inform on disease diagnosis, display neuropathology and neurodegeneration. As noted in this session, degeneration of the retina and visual dysfunction occur in the majority of AD, with new and exciting imaging techniques being employed in both animal models and human ex vivo retinal tissues that suggest that the retina can act as a mirror to the brain. Unfortunately, consistency of methods and access to viable tissues has hampered the generalizability and speed of translatability of these exciting fundings. In addition, to date, no studies have directly linked observed neuropathology or neurodegeneration in the retina with more established biomarkers in CSF or blood which is ultimately needed to understand whether retinal imaging or analysis is viable for clinical use. Retinal imaging in live participants could serve as a minimally invasive biomarker to detect neurodegenerative disease. From recent anti‐amyloid studies, identifying individuals at risk for AD in the asymptomatic stage is critical for efficacy of treatments. If validation and establishment of retinal analyses continue as they have and consistency and consensus is obtained in retinal targets to focus on and these prove to mirror changes ongoing in brain, the timing of these changes in relation to brain changes will need to be determined so that a window of when retinal imaging and analysis is viable will need to be determined. Once the conditions, methods and timing of retinal imaging is determined, the ultimate goal would be to screen aged individuals in a primary care setting annually and then refer to specialty clinics or centers for follow up, confirmation and consideration for therapeutic trials.

Neuropathological hallmarks in the eye: towards biomarkers for neurodegeneration

AbstractThe retina, an extension of the central nervous system, has emerged as a valuable tool for the study of neurodegeneration, as it shares many structural and functional features with the brain. The retina is easily accessible and can be examined non‐invasively, making it an attractive target for the development of biomarkers for neurodegenerative diseases. Several neuropathological hallmarks have been identified in the retina that are associated with neurodegenerative diseases, such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and frontotemporal lobar degeneration (FTLD). The identification of specific biomarkers in the retina may aid in the early detection and diagnosis of neurodegenerative diseases, as well as in the monitoring of disease progression and treatment efficacy.In order to progress these findings into reliable biomarkers, various aspects in this field require attention. Access to post mortem retina tissue, together with characterized brain tissue samples, is essential for the study of retinal pathology in relation to brain pathology. This will allow for the examination of the relationship between retinal and brain pathology and may provide important insights into the mechanisms underlying neurodegeneration. In addition, the assessment of retinal pathology requires standardized approaches, as there is currently no consensus on the methods used to evaluate retinal tissue. Standardized approaches are necessary to ensure the accuracy and reproducibility of results, as well as to facilitate comparison between different studies. Artificial intelligence (AI) has the potential to revolutionize the field of retinal pathology, as it can facilitate the identification of subtle changes in retinal structure that may be indicative of neurodegenerative disease.In conclusion, the retina has emerged as a valuable tool for the study of neurodegeneration. The identification of neuropathological hallmarks in the retina, increased understanding of retinal pathology in relation to brain pathology, standardized approaches for the assessment of pathology, access to post mortem retina tissue, and the use of AI all have the potential to advance the field of retinal pathology and aid in the development of biomarkers for neurodegenerative diseases.

Scutellarin Alleviates Diabetic Retinopathy via the Suppression of Nucleotide-Binding Oligomerization Domain (NOD)-Like Receptor Pyrin Domain Containing Protein 3 Inflammasome Activation

Purpose Diabetic retinopathy, a prevalent complication of diabetes, represents the leading cause of vision loss and blindness among middle-aged and elderly populations. Recent research has demonstrated the ameliorating effects of scutellarin on diabetes-associated complications such as diabetic retinopathy and type 2 diabetic cardiomyopathy. However, investigations into its protective impact and underlying mechanisms on diabetic retinopathy are scant. This study aims to explore the therapeutic potential of scutellarin in diabetic retinopathy treatment. Methods Diabetic retinopathy was induced in rats through intraperitoneal injections of streptozotocin (STZ, 60 mg/kg) administered daily for three consecutive days. Following this, diabetic retinopathy rats received daily intragastric administration of scutellarin (40 mg/kg) for 42 days. Results Our findings suggest that scutellarin alleviates histological damage in the retinal tissues of streptozotocin-challenged rats. Furthermore, scutellarin effectively enhances total retinal thickness and increases the number of ganglion cell layer (GCL) cells in the retinal tissues of streptozotocin-treated rats. Scutellarin also demonstrated anti-inflammatory and antioxidant effects in the retinal tissues of STZ-induced rats, as indicated by reduced levels of tumor necrosis factor-α, interleukin-1β, and interleukin-6, and elevated levels of glutathione peroxidase, superoxide dismutase, and catalase. Additionally, scutellarin effectively inhibited the expression of NOD-like receptor pyrin domain containing protein 3 inflammasome-related markers in the retinal tissues of streptozotocin-administered rats. Conclusions Collectively, our results indicate that scutellarin significantly reduces streptozotocin-induced retinal inflammation, an effect that may be partially attributed to the suppression of NLRP3 inflammasome activation.

Optometry in adults with microdeletion 22q11.2: The eye as a window to the brain

PurposeThe 22q11.2 deletion syndrome (22q11.2DS) has an estimated prevalence of 1:2148 live births and is associated with an increased risk of schizophrenia, cognitive decline and early-onset Parkinson’s disease. Because retinal and cerebral tissue share embryological, physiological and anatomical characteristics, retinal blood vessel morphology and retinal nerve fiber layer (RNFL) thickness have been proposed as non-invasive biomarkers for psychiatric and neurodegenerative disorders. In this exploratory study, we examined these potential biomarkers in adults with 22q11.2DS relative to controls, and in relation to age. MethodsCentral retinal artery and vein equivalent, fractal dimension, and vascular tortuosity, obtained through fundoscopy, and peripapillary RNFL and macular thickness, obtained through optical coherence tomography, were compared between adults with 22q11.2DS and sex- and age-matched controls. ResultsMean retinal vascular fractal dimension and tortuosity values were significantly higher in the group of adults with 22q11.2DS than in controls (p < 0.001; p < 0.001). RNFL was thicker in the nasal segment (p = 0.002) in 22q11.2DS, and a trend for thinner RNFL in the nasal and temporal inferior segments (p = 0.05 and p = 0.06, respectively) was found. There were significant negative correlations with age for fractal dimension (p < 0.001) and RNFL thickness in the global (p = 0.007), temporal inferior (p = 0.005) and temporal superior (p = 0.04) segments in adults with 22q11.2DS, but not in controls. ConclusionsOur results indicate higher retinal vascular fractal dimension and tortuosity, and a decrease in fractal dimension and RNFL thickness in relation to age in adults with 22q11.2DS. Our findings support future studies that focus on retinal fractal dimension and RNFL thickness as potential biomarkers for age-related manifestations in 22q11.2 including psychotic and (early) neurodegenerative disorders.