Retinal Microvessels Research Articles

Microvascular alterations of the ocular surface and retina in connective tissue disease-related interstitial lung disease.

To examine the disparities in macular retinal vascular density between individuals with connective tissue disease-related interstitial lung disease (CTD-ILD) and healthy controls (HCs) by optical coherence tomography angiography (OCTA) and to investigate the changes in microvascular density in abnormal eyes. For a retrospective case-control study, a total of 16 patients (32 eyes) diagnosed with CTD-ILD were selected as the ILD group. The 16 healthy volunteers with 32 eyes, matched in terms of age and sex with the patients, were recruited as control group. The macular retina's superficial retinal layer (SRL) and deep retinal layer (DRL) were examined and scanned using OCTA in each individual eye. The densities of retinal microvascular (MIR), macrovascular (MAR), and total microvascular (TMI) were calculated and compared. Changes in retinal vascular density in the macular region were analyzed using three different segmentation methods: central annuli segmentation method (C1-C6), hemispheric segmentation method [uperior right (SR), superior left (SL), inferior left (IL), and inferior right (IR)], and Early Treatment Diabetic Retinopathy Study (ETDRS) methods [superior (S), inferior (I), left (L), and right (R)]. The data were analyzed using Version 9.0 of GraphPad prism and Pearson analysis. The OCTA data demonstrated a statistically significant difference (P<0.05) in macular retinal microvessel density between the two groups. Specifically, in the SRL and DRL analyses, the ILD group exhibited significantly lower surface density of MIR and TMI compared to the HCs group (P<0.05). Furthermore, using the hemispheric segmentation method, the ILD group showed notable reductions in SL, SR, and IL in the superficial retina (P<0.05), as well as marked decreases in SL and IR in the deep retina (P<0.05). Similarly, when employing the ETDRS method, the ILD group displayed substantial drops in superficial retinal S and I (P<0.05), along with notable reductions in deep retinal L, I, and R (P<0.05). In the central annuli segmentation method, the ILD group exhibited a significant decrease in the superficial retinal C2-4 region (P<0.05), whereas the deep retina showed a notable reduction in the C3-5 region (P<0.05). Additionally, there was an observed higher positive likelihood ratio in the superficial SR region and deep MIR. Furthermore, there was a negative correlation between conjunctival vascular density and both deep and superficial retinal TMI (P<0.001). Patients with CTD-ILD exhibits a significantly higher conjunctival vascular density compared to the HCs group. Conversely, their fundus retinal microvascular density is significantly lower. Furthermore, CTD-ILD patients display notably lower superficial and deep retinal vascular density in comparison to the HCs group. The inverse correlation between conjunctival vascular density and both superficial and deep retinal TMI suggests that detecting subtle changes in ocular microcirculation could potentially serve as an early diagnostic indicator for connective tissue diseases, thereby enhancing disease management.

Melatonin Attenuates Diabetic Retinopathy by Regulating EndMT of Retinal Vascular Endothelial Cells via Inhibiting the HDAC7/FOXO1/ZEB1 Axis

ABSTRACTDiabetic retinopathy (DR) is characterized as a microvascular disease. Nonproliferative diabetic retinopathy (NPDR) presents with alterations in retinal blood flow and vascular permeability, thickening of the basement membrane, loss of pericytes, and formation of acellular capillaries. Endothelial–mesenchymal transition (EndMT) of retinal microvessels may play a critical role in advancing NPDR. Melatonin, a hormone primarily secreted by the pineal gland, is a promising therapeutic for DR. This study explored the EndMT in retinal microvessels of NPDR and its related mechanisms. The effect of melatonin on the retina of diabetic rats was evaluated by electroretinogram (ERG) and histopathologic slide staining. Furthermore, the effect of melatonin on human retinal microvascular endothelial cells (HRMECs) was detected by EdU incorporation assay, scratch assay, transwell assay, and tube formation test. Techniques such as RNA‐sequencing, overexpression or knockdown of target genes, extraction of cytoplasmic and nuclear protein, co‐immunoprecipitation (co‐IP), and multiplex immunofluorescence facilitated the exploration of the mechanisms involved. Our findings reveal, for the first time, that melatonin attenuates diabetic retinopathy by regulating EndMT of retinal vascular endothelial cells via inhibiting the HDAC7/FOXO1/ZEB1 axis. Collectively, these results suggest that melatonin holds potential as a therapeutic strategy to reduce retinal vascular damage and protect vision in NPDR.

Mitochondrial Genome-Encoded Long Noncoding RNA Cytochrome B (LncCytB) and Mitochondrial Ribonucleases in Diabetic Retinopathy.

Hyperglycemia damages mitochondria and downregulates transcription of mtDNA-encoded genes and the long noncoding RNA LncCytB, causing mitochondrial genomic instability. The genes encoded by mtDNA are transcribed as large polycistronic transcripts, and the 5' ends of precursor tRNAs are processed by mitochondrial-targeted ribonuclease P (MRPPs). Our aim was to investigate the role of MRPP1 in the downregulation of LncCytB in diabetic retinopathy. Using human retinal endothelial cells incubated in 20 mM D-glucose for 96 h, the gene expression and mitochondrial localization (immunofluorescence) of MRPP1 and the interaction between MRPP1 and LncCytB (determined by RNA-FISH and RNA immunoprecipitation) were quantified. The results were confirmed in retinal microvessels from streptozotocin-induced diabetic mice and from human donors with documented diabetic retinopathy. Compared to normal glucose, high glucose decreased mRNA and mitochondrial localization of MRPP1 and its interaction with LncCytB. While MRPP1 overexpression prevented glucose-induced decrease in MRPP1-LncCytB interaction, LncCytB expression and mitochondrial damage (reduction in protective nucleoids in mtDNA), MRPP1-siRNA further worsened them. Similar results were obtained from retinal microvessels from diabetic mice and from human donors with diabetic retinopathy. Downregulation of MRPP1 in diabetes suppresses LncCytB transcription, resulting in mitochondrial functional and genomic instability, ultimately leading to the development of diabetic retinopathy. Thus, preventing MRPP1 downregulation has the potential to inhibit retinopathy and prevent the fear of vision loss in diabetic patients.

Mitochondrial DNA transcription and mitochondrial genome-encoded long noncoding RNA in diabetic retinopathy

In diabetic retinopathy, mitochondrial DNA (mtDNA) is damaged and mtDNA-encoded genes and long noncoding RNA cytochrome B (LncCytB) are downregulated. LncRNAs lack an open reading frame, but they can regulate gene expression by associating with DNA/RNA/protein. Double stranded mtDNA has promoters on both heavy (HSP) and light (LSP) strands with binding sites for mitochondrial transcription factor A (TFAM) between them. The aim was to investigate the role of LncCytB in mtDNA transcription in diabetic retinopathy. Using human retinal endothelial cells incubated in high glucose, the effect of regulation of LncCytB on TFAM binding at mtDNA promoters was investigated by Chromatin immunoprecipitation, and binding of LncCytB at TFAM by RNA immunoprecipitation and RNA fluorescence in situ hybridization. High glucose decreased TFAM binding at both HSP and LSP, and binding of LncCytB at TFAM. While LncCytB overexpression ameliorated decrease in TFAM binding and transcription of genes encoded by both H- and L- strands, LncCytB-siRNA further downregulated them. Maintenance of mitochondrial homeostasis by overexpressing mitochondrial superoxide dismutase or Sirtuin-1 protected diabetes-induced decrease in TFAM binding at mtDNA and LncCytB binding at TFAM, and mtDNA transcription. Similar results were obtained from mouse retinal microvessels from streptozotocin-induced diabetic mice. Thus, LncCytB facilitates recruitment of TFAM at HSP and LSP, and its downregulation in diabetes compromises the binding, resulting in the downregulation of polypeptides encoded by mtDNA. Regulation of LncCytB, in addition to protecting mitochondrial genomic stability, should also help in maintaining the transcription of mtDNA encoded genes and electron transport chain integrity in diabetic retinopathy.

Cellular communication network factor 1 promotes retinal leakage in diabetic retinopathy via inducing neutrophil stasis and neutrophil extracellular traps extrusion

BackgroundDiabetic retinopathy (DR) is a major cause of blindness and is characterized by dysfunction of the retinal microvasculature. Neutrophil stasis, resulting in retinal inflammation and the occlusion of retinal microvessels, is a key mechanism driving DR. These plugging neutrophils subsequently release neutrophil extracellular traps (NETs), which further disrupts the retinal vasculature. Nevertheless, the primary catalyst for NETs extrusion in the retinal microenvironment under diabetic conditions remains unidentified. In recent studies, cellular communication network factor 1 (CCN1) has emerged as a central molecule modulating inflammation in pathological settings. Additionally, our previous research has shed light on the pathogenic role of CCN1 in maintaining endothelial integrity. However, the precise role of CCN1 in microvascular occlusion and its potential interaction with neutrophils in diabetic retinopathy have not yet been investigated.MethodsWe first examined the circulating level of CCN1 and NETs in our study cohort and analyzed related clinical parameters. To further evaluate the effects of CCN1 in vivo, we used recombinant CCN1 protein and CCN1 overexpression for gain-of-function, and CCN1 knockdown for loss-of-function by intravitreal injection in diabetic mice. The underlying mechanisms were further validated on human and mouse primary neutrophils and dHL60 cells.ResultsWe detected increases in CCN1 and neutrophil elastase in the plasma of DR patients and the retinas of diabetic mice. CCN1 gain-of-function in the retina resulted in neutrophil stasis, NETs extrusion, capillary degeneration, and retinal leakage. Pre-treatment with DNase I to reduce NETs effectively eliminated CCN1-induced retinal leakage. Notably, both CCN1 knockdown and DNase I treatment rescued the retinal leakage in the context of diabetes. In vitro, CCN1 promoted adherence, migration, and NETs extrusion of neutrophils.ConclusionIn this study, we uncover that CCN1 contributed to retinal inflammation, vessel occlusion and leakage by recruiting neutrophils and triggering NETs extrusion under diabetic conditions. Notably, manipulating CCN1 was able to hold therapeutic promise for the treatment of diabetic retinopathy.

Th1 cells contribute to retinal ganglion cell loss in glaucoma in a VCAM-1-dependent manner.

Glaucoma is a complex neurodegenerative disorder characterized by the progressive loss of retinal ganglion cells (RGC) and optic nerve axons, leading to irreversible visual impairment. Despite its clinical significance, the underlying mechanisms of glaucoma pathogenesis remain poorly understood. In this study, we aimed to unravel the multifaceted nature of glaucoma by investigating the interaction between T cells and retinas. By utilizing clinical samples, murine glaucoma models, and T cell transfer models, we made several key findings. Firstly, we observed that CD4+ T cells from glaucoma patients displayed enhanced activation and a bias towards T helper (Th) 1 responses, which correlated with visual impairment. Secondly, we identified the infiltration of Th1 cells into the retina, where they targeted RGC and integrated into the pro-inflammatory glial network, contributing to progressive RGC loss. Thirdly, we discovered that circulating Th1 cells upregulated vascular cell adhesion protein 1 (VCAM-1) on retinal microvessels, facilitating their entry into the neural retina. Lastly, we found that Th1 cells underwent functional reprogramming before reaching the retina, acquiring a phenotype associated with lymphocyte migration and neurodegenerative diseases. Our study provides novel insights into the role of peripheral CD4+ T cells in glaucoma pathogenesis, shedding light on the mechanisms underlying their infiltration into the retina and offering potential avenues for innovative therapeutic interventions in this sight-threatening disease.

Molecular Mechanisms and Therapeutic Implications of Human Pericyte-like Adipose-Derived Mesenchymal Stem Cells in an In Vitro Model of Diabetic Retinopathy.

The blood-retinal barrier (BRB) is strongly compromised in diabetic retinopathy (DR) due to the detachment of pericytes (PCs) from retinal microvessels, resulting in increased permeability and impairment of the BRB. Western blots, immunofluorescence and ELISA were performed on adipose mesenchymal stem cells (ASCs) and pericyte-like (P)-ASCs by co-cultured human retinal endothelial cells (HRECs) under hyperglycemic conditions (HG), as a model of DR. Our results demonstrated that: (a) platelet-derived growth factor receptor (PDGFR) and its activated form were more highly expressed in monocultured P-ASCs than in ASCs, and this expression increased when co-cultured with HRECs under high glucose conditions (HG); (b) the transcription factor Nrf2 was more expressed in the cytoplasmic fraction of ASCs and in the P-ASC nuclear fraction, under normal glucose and, even more, under HG conditions; (c) cytosolic phospholipase A2 activity and prostaglandin E2 release, stimulated by HG, were significantly reduced in P-ASCs co-cultured with HRECs; (d) HO-1 protein content was significantly higher in HG-P-ASCs/HRECs than P-ASCs/HRECs; and (e) VEGF-A levels in media from HG-co-cultures were reduced in P-ASCs/HRECs with respect to ASCs/HRECs. The data obtained highlighted the potential of autologous differentiated ASCs in future clinical applications based on cell therapy to counteract the damage induced by DR.

Ultrastructural changes in the rat retina in the presence of long-term opioid exposure

Purpose: To determine the features of the untrastructural reorganization in the rat retina by the end of week 4 and week 6 of experimental opioid exposure. Material and Methods: Forty-eight adult male albino rats (weight, 200-250 g; age, 4.5 months) were used in this study. They received nalbuphine hydrochloride intramuscularly daily for 42 days. Particularly, the drug was administered daily at a dose of 0.212 mg/kg for weeks 1 and 2, 0.225 mg/kg for weeks 3 and 4, and 0.252 mg/kg for weeks 5 and 6. In this way, we experimentally created the conditions of chronic opioid exposure. Animals were divided into three groups. Group 1 (19 animals) received nalbuphine for 28 days, and group 2 (19 animals), for 42 days. Group 3 (control group) comprised 10 animals. Of these, 5 animals were treated with normal saline at a dose of 0.22 mg/kg intramuscularly daily for 28 days, and the rest were treated in a similar manner for 42 days. Transmission electron microscopy studies of the rat retina were conducted in a routine manner. Results: By the end of week 4 of experimental opioid exposure, there was an increase in the number of retinal microvessels with signs of hyperemia and degenerative changes in retinal pigment epithelium (RPE) cells, increase in the destruction of membranous discs of photoreceptor outer segments, necrobiotic changes in the nuclei of individual photoreceptors, axonal degeneration in the outer and inner plexiform layers, degenerative changes in retinal horizontal neurons, and the appearance of necrotic structural changes in the cytoplasm of bipolar and amacrine cells. By the end of week 6, there was a further increase in hyperemia of retinal vessels and degenerative and necrotic changes in individual RPE cells and photoreceptor outer segments. In addition, we observed destruction and shortening of mitochondrial cristae of photoreceptor inner segments, necrotic nuclear changes in individual photoreceptors, degeneration of axons of the outer and inner plexiform layers, degenerative and necrotic changes in bipolar and amacrine cells, hypertrophic Müller cell processes, degeneration of ganglion cells, and vascular hyperemia and moderate perivascular edema in the outer and inner plexiform layers. Conclusion: Therefore, in the current rat study, after a 4-week exposure to daily nalbuphine injections at a dose ranging 0.212 to 0.253 mg/kg, there was ultrastuctural evidence of destructive processes in the RPE and photoreceptor outer segments, axonal degeneration in the outer and inner plexiform layers, degenerative and necrotic changes in bipolar and amacrine cells, hypertrophic Müller cell processes, ganglion cell degeneration and hyperemia due to an impaired retinal microcirculatory ultrastructure. At week 6 of the experiment, there was evidence of increased destructive and degenerative processes in structural components of the retina.

Retinal microvascular and microstructural alterations in the diagnosis of meibomian gland dysfunction in severely obese population: a new approach.

To study retinal microvascular and microstructural alterations in meibomian gland dysfunction (MGD) in severely obese population using optical coherence tomography angiography (OCTA). Twelve MGD patients with severely obese population (PAT group; 24 eyes) and 12 healthy controls (HC group; 24 eyes) were recruited. OCTA images were segmented into five [superior (S), nasal (N), inferior (I), temporal (T), and central foveal (C)] or nine [inner superior (IS), outer superior (OS), inner nasal (IN), outer nasal (ON), inner inferior (II), outer inferior (OI), inner temporal (IT), outer temporal (OT), and C] subregions. The superficial vessel density (SVD), retinal thickness (RT), foveal avascular zone (FAZ) parameters, and retinal volume were measured. Visual acuity was significantly different between two groups (0.8±0.17 in PAT group vs 0.2±0.06 in HC group). SVD was significantly lower in PATs in N, T, OS, IN, OT, and ON. The area under the receiver operating characteristic curve (AUC) for T was 0.961 [95% confidence interval (CI): 0.908 to 1.000], for OS was 0.962 (95%CI: 0.915 to 1.000). RT was significantly lower in PATs in IS, OS, OI, OT, ON, IT, IN, and II. AUC for OT was 0.935 (95%CI: 0.870 to 0.999), for IS was 0.915 (95% CI: 0.838 to 0.992). Angiography results showed significantly lower area and perimeter of FAZ, SVD of the inner retina and both retinal volume and the average volume thickness in the PAT group. Vision may be affected in patients with MGD due to changes in retinal microvessels and microstructures. These changes detected by OCTA may be a potential marker for diagnosing MGD in severe obesity.

Correlation Between Corneal Whorl-Like Nerve and Retinal Neurodegenerative Changes and Their Association With Microvessel Perfusion in Diabetes.

The purpose of this study was to compare the evolution of changes in the corneal nerves, retinal nerves, and cells and blood vessels at a single time point in early diabetic retinopathy (DR). Eighty participants (60 with diabetes and 20 nondiabetic controls) were examined. DR was graded according to the International Classification of Diabetic Retinopathy. Inferior whorl length (IWL), spiral orientation, central nerve fiber length (CNFL), retinal nerve fiber layer (RNFL) thickness, ganglion cell complex (GCC) layer thickness, global loss volume (GLV), focal loss volume (FLV) indices, superficial (sVD), and deep vessel densities (dVD) were examined. Compared with those of healthy controls, the IWL, CNFL, and FLV were decreased in the diabetic groups (P < 0.001). The IWL was significantly positively correlated with the RNFL and GCC thicknesses in the diabetic group (r = 0.248, P = 0.006 and r = 0.207, P = 0.023, respectively) and significantly negatively correlated with the FLV (r = -0.535, P < 0.001). The sVD was significantly positively correlated with the RNFL thickness (r = 0.314, P < 0.001) and negatively correlated with the GLV (r = -0.229, P = 0.012). Our findings suggest a correlation between corneal whorl-like nerve plexus and retinal nerve changes in the early stages of DR and that the IWL of the cornea may be able to indicate the extent of DR. Retinal nerve changes are associated with retinal microvessel perfusion, and nerve changes may precede vessel lesions.

Mitochondrial Genome-Encoded Long Noncoding RNA Cytochrome B and Mitochondrial Dysfunction in Diabetic Retinopathy.

Aims: Mitochondrial dysfunction is closely associated with the development of diabetic complications. In diabetic retinopathy, electron transport chain is compromised and mitochondrial DNA (mtDNA) is damaged, downregulating transcription of mtDNA-encoded cytochrome B (CYTB) and its antisense long noncoding RNA, long noncoding RNA cytochrome B (LncCytB). Our goal was to investigate the role of LncCytB in the regulation of CYTB and mitochondrial function in diabetic retinopathy. Methods: Using human retinal endothelial cells, genetically manipulated for LncCytB (overexpression or silencing), the effect of high glucose (20 mM d-glucose) on LncCytB-CYTB interactions (by chromatin isolation by RNA purification), CYTB gene expression (by real-time quantitative polymerase chain reaction), complex III activity, mitochondrial free radicals, and oxygen consumption rate (OCR, by Seahorse XF analyzer) was investigated. Key results were confirmed in the retinal microvessels from streptozotocin-induced diabetic mice. Results: High glucose decreased LncCytB-CYTB interactions, and while LncCytB overexpression ameliorated glucose-induced decrease in CYTB gene transcripts, complex III activity and OCR and increase in mitochondrial reactive oxygen species, LncCytB-siRNA further attenuated CYTB gene transcription, complex III activity, and OCR. Similar decrease in LncCytB-CYTB interactions and CYTB transcription was observed in diabetic mice. Furthermore, maintenance of mitochondrial homeostasis by overexpressing superoxide dismutase or sirtuin 1 in mice ameliorated diabetes-induced decrease in LncCytB-CYTB interactions and CYTB gene transcripts, and also improved complex III activity and mitochondrial respiration. Innovation and Conclusion: LncCytB downregulation in hyperglycemic milieu downregulates CYTB transcription, which inhibits complex III activity and compromises mitochondrial stability and OCR. Thus, preventing LncCytB downregulation in diabetes has potential of inhibiting the development of diabetic retinopathy, possibly via maintaining mitochondrial respiration. Antioxid. Redox Signal. 39, 817-828.

Protective effects and mechanisms of Momordica charantia polysaccharide on early-stage diabetic retinopathy in type 1 diabetes

Momordica charantia polysaccharide (MCP) is a potential drug for the prevention and alleviation of diabetes mellitus (DM) and diabetic retinopathy (DR). This study aimed to investigate the potential protective effects of MCP on early-stage DR and explore the underlying mechanisms. The model group (DM group) and treatment group (D+H group) were established by inducing type 1 DM using a single dose of streptozotocin (STZ) at 60 mg/kg. After modeling, the D+H group was orally administered a 500 mg/kg dose of MCP solution once daily for 12 weeks. Monitoring of systemic indicators (FBG, body weight, general condition) and retinal tissue inflammation and apoptosis (HE staining, IL-6, MCP-1, TNF-α, VEGF, NF-κB, Caspase-3) in this study demonstrated that MCP intervention alleviated both DM and DR. MCP improved the body weight and general condition of DM rats by reducing FBG levels. It also enhanced the anti-inflammatory and anti-apoptotic capabilities of retinal neurons and microvessels by modulating the actions of cytokines, thereby further regulating the inflammation and apoptosis of retinal neurons and microvessels. The underlying mechanisms may be associated with the downregulation of NF-κB and Caspase-3 pathway protein expression, as well as the downregulation of mRNA expression of NF-κB and Caspase-3 pathway genes. Further research is needed to elucidate the potential mechanisms underlying the protective effects of MCP on DR. MCP may emerge as a selective medication for the prevention and alleviation of DM and a novel natural medicine for the prevention and alleviation of DR.

VEGFR-2 adhesive nanoprobes reveal early diabetic retinopathy in vivo

Diabetic retinopathy (DR) is a debilitating organ manifestation of diabetes. Absent of early diagnosis and intervention, vision tends to drastically and irreversibly decline. Previously, we showed higher vascular endothelial growth factor receptor 2 (VEGFR-2) expression in diabetic microvessels, and the suitability of this molecule as a biomarker for early DR diagnosis. However, a hurdle to translation remained generation of biodegradable nanoprobes that are sufficiently bright for in vivo detection. Here, an adhesive fluorescent nanoprobe with high brightness was developed using biodegradable materials. To achieve that, a fluorophore with bulky hydrophobic groups was encapsulated in the nanoparticles to minimize fluorophore π-π stacking, which diminishes brightness at higher loading contents. The nanoprobe selectively targeted the VEGFR-2 under dynamic flow conditions. Upon systemic injection, the nanoprobes adhered in the retinal microvessels of diabetic mice and were visualized as bright spots in live retinal microscopy. Histology validated the in vivo results and showed binding of the nanoprobes to the microvascular endothelium and firmly adhering leukocytes. Leukocytes were found laden with nanoprobes, indicating the potential for payload transport across the blood-retinal barrier. Our results establish the translational potential of these newly generated nanoprobes in early diagnosis of DR.

Reduced folate carrier 1 is present in retinal microvessels and crucial for the inner blood retinal barrier integrity

BackgroundReduced folate carrier 1 (RFC1; SLC19a1) is the main responsible transporter for the B9 family of vitamins named folates, which are essential for normal tissue growth and development. While folate deficiency resulted in retinal vasculopathy, the expression and the role of RFC1 in blood-retinal barrier (BRB) are not well known.MethodsWe used whole mount retinas and trypsin digested microvessel samples of adult mice. To knockdown RFC1, we delivered RFC1-targeted short interfering RNA (RFC1-siRNA) intravitreally; while, to upregulate RFC1 we delivered lentiviral vector overexpressing RFC1. Retinal ischemia was induced 1-h by applying FeCl3 to central retinal artery. We used RT-qPCR and Western blotting to determine RFC1. Endothelium (CD31), pericytes (PDGFR-beta, CD13, NG2), tight-junctions (Occludin, Claudin-5 and ZO-1), main basal membrane protein (Collagen-4), endogenous IgG and RFC1 were determined immunohistochemically.ResultsOur analyses on whole mount retinas and trypsin digested microvessel samples of adult mice revealed the presence of RFC1 in the inner BRB and colocalization with endothelial cells and pericytes. Knocking down RFC1 expression via siRNA delivery resulted in the disintegration of tight junction proteins and collagen-4 in twenty-four hours, which was accompanied by significant endogenous IgG extravasation. This indicated the impairment of BRB integrity after an abrupt RFC1 decrease. Furthermore, lentiviral vector-mediated RFC1 overexpression resulted in increased tight junction proteins and collagen-4, confirming the structural role of RFC1 in the inner BRB. Acute retinal ischemia decreased collagen-4 and occludin levels and led to an increase in RFC1. Besides, the pre-ischemic overexpression of RFC1 partially rescued collagen-4 and occludin levels which would be decreased after ischemia.ConclusionIn conclusion, our study clarifies the presence of RFC1 protein in the inner BRB, which has recently been defined as hypoxia–immune-related gene in other tissues and offers a novel perspective of retinal RFC1. Hence, other than being a folate carrier, RFC1 is an acute regulator of the inner BRB in healthy and ischemic retinas.

Correlation between morphological characteristics of retinal microvessels and diabetic kidney disease in patients with type 2 diabetes mellitus based on a machine learning model

Objective: To explore the correlation between the morphological characteristics of retinal microvessels and diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus (T2DM). Methods: The clinical data and fundus photography of patients with T2DM treated in the First Affiliated Hospital of Zhengzhou University from January 2018 to December 2020 were retrospectively collected and analyzed. According to the presence of abnormal renal function, the patients were divided into DKD group and control group. The morphology and structure of fundus vessels were digitized by U-Net depth convolution neural network, and the correlation between fundus vascular morphology and DKD was analyzed by multivariate logistic regression. Results: A total of 648 patients with T2DM were enrolled, including 410 males and 238 females, and aged (53±10) years. There were 398 and 250 cases in control and DKD groups, respectively. Meanwhile, 1 296 fundus images were collected. Compared with control group, the male ratio (68.4% vs 60.1%, P=0.032), age [(54±9) vs (52±10) years, P=0.005], blood pressure [(136.8±17.3) vs (130.3±15.4) mmHg（1 mmHg=0.133 kPa）, P<0.001], total cholesterol [(4.5±1.4) vs (4.2±1.0) mmol/L, P=0.009], triglyceride [M (Q1, Q3)][1.7 (1.2, 3.0) vs 1.4 (1.0, 2.3) mmol/L, P<0.001] and Cystatin C [(0.9 (0.8, 1.0) vs 0.8 (0.7, 0.9) mg/L, P<0.001] were higher in the DKD group, while high-density lipoprotein [(1.0±0.3) vs (1.1±0.3) mmol/L, P=0.001] was lower in the DKD group. Multivariate logistic regression analysis showed that the risk of DKD in the third quartile (right eye: OR=1.825, 95%CI: 1.204-2.768, P=0.005) and fourth quartile (left eye: OR=1.929, 95%CI: 1.218-3.055, P=0.005) was higher than that in the lowest quartile of vascular curvature after adjusting for age and gender. The increase of average diameter of retinal vein was associated with the risk of DKD (left eye: OR=1.044, 95%CI: 1.013-1.075, P=0.005). The decrease of vascular fractal dimension (fourth quartile of left eye: OR=0.444, 95%CI: 0.199-0.987, P=0.046) and retinal vascular density (the second and fourth quartile of the right eye: OR=0.639, 95%CI: 0.409-0.998, P=0.049; OR=0.534, 95%CI: 0.331-0.864, P=0.010) were related to the risk of DKD. Conclusions: The abnormal morphological characteristics of retinal microvessels are related to the occurrence of DKD. The increase of retinal vein diameter and the decrease of retinal vessel density correlate with the occurrence of DKD.

Responses of retinal and brain microvasculature to streptozotocin induced diabetes revealed by global expression profiling.

This study aims to determine the effects of diabetes in the retinal and brain microvasculature through gene expression profiling. Twelve male Wistar rats were randomly divided into two groups: streptozotocin-induced diabetic rats and time-matched nondiabetic rats. The retinal microvessels (RMVs) and brain microvessels (BMVs) were mechanically isolated from individual rats. Differentially expressed genes (DEGs) in diabetic and nondiabetic microvessels were identified by cDNA microarrays analysis. In RMVs, we identified 43 DEGs, of which 20 were upregulated while 23 were downregulated by diabetes. In BMVs, 35 genes DEGs were identified, of which 22 were upregulated and 13 were downregulated by diabetes. Altered expression of the Nars, Gars, Mars, Iars, Yars, Bcl2, Nqo1, NR4A3, Gpd1, Stc1, Tsc22d3, Tnfrsf21 mRNA as observed in the microarray analyses, was confirmed by quantitative RT-PCR. The aminoacyl-tRNA synthetases (aaRSs) pathway in RMVs was significantly overrepresented as compared to BMVs. Our study demonstrates for the first time that in the brain microvasculature multiple compensatory mechanisms exists, serving to protect brain tissue from diabetic insults, whereas these mechanisms are not activated in the retinal microvasculature. This provides new insights as to why brain microvasculature is less susceptible to diabetes.

Effect of Highly Active Antiretroviral Therapy on Fundus Images and Retinal Microvessel Diameter in HIV/AIDS Patients

We aimed to investigate whether there were changes in fundus picture and retinal microvascularity of patients with human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) who were treated with highly active antiretroviral therapy (HAART). From July 2015 to November 2016, 130 HIV/AIDS patients were collected by the Yunnan Institute of Traditional Chinese Medicine, including 63 treatment-naïve patients and 67 that received HAART for 12 months. Fundus picture lesions, retinal microvascular diameters, CD4+ T lymphocyte count and HIV-1 plasma viral loads were compared between the two groups. The recruited patients were mainly young and middle-aged, with more males than females. There were no significant differences in smoking history, comorbidities and opportunistic infections between the two groups. According to the analysis results from SPSS 20.0 software, the number of CD4+ T lymphocytes in the treated patients (563.34±2.56 cells/μL) increased significantly (P=0.009) as compared with untreated patients (451.37±2.10 cells/μL), and the HIV-1 plasma viral load reduced considerably (4794 vs 0 copy/mL, P=0.000). No significant differences were observed from the fundus picture of patients after effective HAART therapy, including the retinal artery diameter, venous diameter and arteriovenous diameter ratio.

Mitochondrial Genome-Encoded Long Noncoding RNA and Mitochondrial Stability in Diabetic Retinopathy.

Mitochondria experience genomic and functional instability in diabetes, and mitochondrial dysfunction has a critical role in the development of diabetic retinopathy. Diabetes also alters expressions of many long non-coding RNAs (LncRNAs), the RNAs with >200 nucleotides and no open reading frame. LncRNAs are mainly encoded by nuclear genome, but mtDNA also encodes three LncRNAs. Our goal was to investigate the effect of hyperglycemia on mtDNA-encoded LncRNA Cytochrome B (LncCytB) in mtDNA stability in diabetic retinopathy. Retinal endothelial cells, transfected with LncCytB- overexpressing plasmids or siRNA, incubated in 5mmols/L (NG) or 20mmols/L (HG) D-glucose for four days, were analyzed for LncCytB expression by strand-specific PCR, and its mitochondrial localization by RNA-FISH. Damage sensitive mtDNA regions were examined by micrococcal nuclease digestion-sequencing, and LncCytB occupancy at mtDNA by chromatin isolation by RNA purification. Protective nucleoids in mtDNA were analyzed by SYBR green-MitoTracker Red staining, and confirmed in isolated mitochondria by flow cytometry. Compared to NG, HG downregulated LncCytB by >50%, but had no significant effect on the other mtDNAencoded LncRNAs. mtDNA packaging was impaired and MNase sensitivity was increased, and LncCytB occupancy at mtDNA was decreased. While LncCytB overexpression ameliorated mtDNA damage and decrease in nucleoids and copy numbers, LncCytB-siRNA exacerbated damage and further reduced nucleoids. Retinal microvessels from streptozotocin-induced diabetic mice and human donors with diabetic retinopathy presented similar decrease in LncCytB and mtDNA nucleoids. Thus, LncCytB has a major role in maintaining mitochondrial genomic stability, and its downregulation in hyperglycemic milieu contributes to increased vulnerability of mtDNA to damage.

Inner blood‐retinal barrier alterations associated with vascular amyloidosis in MCI and AD patients

AbstractBackgroundBlood‐brain barrier (BBB) breakdown in Alzheimer’s disease (AD) is linked to cerebral amyloid‐beta (Aβ) accumulation and cognitive decline. Previously, we identified substantial retinal pericyte loss along with vascular amyloidosis in mild cognitively impaired (MCI) and AD patients. In double transgenic APPSWE/PS1∆E9 (ADtg) mice, we further demonstrated substantial retinal capillary degeneration and microvascular leakage in comparison to wild type (WT) mice. Here, we sought to expand our investigation of inner blood‐retinal barrier (iBRB) integrity in relation to retinal and cerebral pathological benchmarks in MCI and AD patients compared to cognitively normal (CN) controls.MethodPostmortem human eyes and brains were obtained from USC‐ADRC. Retinas were isolated from 35 AD patients, 15 MCI patients, and 20 age‐ and sex‐matched healthy controls. Retinal cross sections spanning along ora serrata to optic disc were prepared from four pre‐defined quadrants: superiortemporal, temporalinferior, inferiornasal, and nasalsuperior. Histological examination was performed by immunostaining for different Aβ alloforms, tight junctions (zonula occulden‐1, claudin‐1 and ‐5), and blood vessels (lectin). Retinal microvessels were isolated for evaluating capillary degeneration. Stereological quantifications were performed and then correlated with the respective neuropathological reports of these patients. Mass spectrometry analysis of proteins isolated from another AD and control patients’ cohort was conducted to validate our data.ResultOur preliminary results showed early and significant downregulation of zonula occulden‐1 in retinal blood vessels of MCI and AD patients compared to controls. Downregulation of this key tight junction molecule was associated with increased retinal vascular Aβ accumulation. In addition, significant deficiencies of vascular‐related proteins including smoothelin, vascular endothelial zinc finger 1 (VEZF1), catenin isoform 1 were detected in retinal homogenates from AD patients versus controls by global proteome analysis. Analysis of isolated retinal blood vessels revealed capillary degeneration along with Alzheimer’s‐relevant vascular pathology in these patients.ConclusionOur data suggested an early alteration of iBRB integrity that contributed to Aβ accumulation in retinal blood vessels, consistent with previous reports in BBB of AD patients. Our results provide new insights into AD‐related vascular pathomechanisms in the retina that can be further evaluated for retinal imaging.

Habitual intake of dietary methylglyoxal is associated with less low-grade inflammation: the Maastricht Study

Dicarbonyls are major reactive precursors of advanced glycation endproducts (AGEs). Dicarbonyls are formed endogenously and also during food processing. Circulating dicarbonyls and AGEs are associated with inflammation and microvascular complications of diabetes, but for dicarbonyls from the diet these associations are currently unknown. We sought to examine the associations of dietary dicarbonyl intake with low-grade inflammation and microvascular function. In 2792 participants (mean ± SD age: 60±8 y; 50% men; 26% type 2 diabetes) of the population-based cohort the Maastricht Study, we estimated the habitual intake of the dicarbonyls methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG) by linking FFQ outcome data to our food composition database of the MGO, GO, and 3-DG content of>200 foods. Low-grade inflammation was assessed as six plasma biomarkers, which were compiled in a z score. Microvascular function was assessed as four plasma biomarkers, compiled in a zscore; as diameters and flicker light-induced dilation in retinal microvessels; as heat-induced skin hyperemic response; and as urinary albumin excretion. Cross-sectional associations of dietary dicarbonyls with low-grade inflammation and microvascular function were investigated using linear regression with adjustments for age, sex, potential confounders related to cardiometabolic risk factors, and lifestyle and dietary factors. Fully adjusted analyses revealed that higher intake of MGO was associated with a lower z score for inflammation [standardized β coefficient (STD β): -0.05; 95% CI: -0.09 to -0.01, with strongest inverse associations for hsCRP and TNF-α: both -0.05; -0.10 to -0.01]. In contrast, higher dietary MGO intake was associated with impaired retinal venular dilation after full adjustment (STD β: -0.07; 95% CI: -0.12 to -0.01), but not with the other features of microvascular function. GO and 3-DG intakes were not consistently associated with any of the outcomes. Higher habitual intake of MGO was associated with less low-grade inflammation. This novel, presumably beneficial, association is the first observation of an association between MGO intake and health outcomes in humans and warrants further investigation.