Vascular Eye Diseases Research Articles

Photoreceptors inhibit pathological retinal angiogenesis through transcriptional regulation of Adam17 via c-Fos

Pathological retinal angiogenesis profoundly impacts visual function in vascular eye diseases, such as retinopathy of prematurity (ROP) in preterm infants and age-related macular degeneration in the elderly. While the involvement of photoreceptors in these diseases is recognized, the underlying mechanisms remain unclear. This study delved into the pivotal role of photoreceptors in regulating abnormal retinal blood vessel growth using an oxygen-induced retinopathy (OIR) mouse model through the c-Fos/A disintegrin and metalloprotease 17 (Adam17) axis. Our findings revealed a significant induction of c-Fos expression in rod photoreceptors, and c-Fos depletion in these cells inhibited pathological neovascularization and reduced blood vessel leakage in the OIR mouse model. Mechanistically, c-Fos directly regulated the transcription of Adam17 a shedding protease responsible for the production of bioactive molecules involved in inflammation, angiogenesis, and cell adhesion and migration. Furthermore, we demonstrated the therapeutic potential by using an adeno-associated virus carrying a rod photoreceptor-specific short hairpin RNA against c-fos which effectively mitigated abnormal retinal blood vessel overgrowth, restored retinal thickness, and improved electroretinographic (ERG) responses. In conclusion, this study highlights the significance of photoreceptor c-Fos in ROP pathology, offering a novel perspective for the treatment of this disease.

СОВРЕМЕННЫЕ ПОДХОДЫ К ЛЕЧЕНИЮ РЕТИНАЛЬНЫХ ОККЛЮЗИЙ ВЕН СЕТЧАТКИ, ЛИТЕРАТУРНЫЙ ОБЗОР

Retinal vein occlusion (RVO) is the second among acquired vascular eye diseases, giving priority only to diabetic retinopathy. The severity of retinopathy depends on the location of the occlusion and the development of collateral vessels. RVO is not accompanied only by a decrease in visual acuity (VA), but also by the development of such complications as recurrent intravitreal hemorrhages, traction retinal detachment, secondary neovascular glaucoma. It causes the disability of patients and loss of professional fitness in people of working age. The treatment of RVO focuses on two main goals. The first one is the identification of risk factors and their drug therapy, and the second one is the identification and treatment of complications of retinal vein occlusion. The treatment of any pathology depends on early diagnosis, as well as a quick and well-chosen algorithm for managing the patient. The macular edema is treated by intravitreal injections of corticosteroids, antiVEGF, laser photocoagulation of the retina. Intraocular injections is currently the only way to provide a high intravitreal and intraretinal concentration of the drug. This review describes an algorithm for choosing the optimal treatment for RVO.

Identification of Novel Retinal Pericyte-Targeting rAAV Vectors Through Directed Evolution

PurposeRetinal pericytes play a vital role in maintaining retinal homeostasis, and their dysfunction underlies pathogenesis in such vascular eye diseases as diabetic retinopathy and wet age-related macular degeneration. Consequently, retinal pericytes are attractive therapeutic targets for gene therapy, but effectively targeting pericytes with recombinant adeno-associated virus (rAAV) vectors remains a challenge.MethodsWe introduced genetic modifications into the surface-exposed variable regions of the rAAV2/2 capsid to generate a complex library (>1 × 107) of capsid mutants that were then screened for preferential tropism toward retinal pericytes. Using the Tg(Cspg4-DsRed.T1)1Akik/J reporter mouse model, which has red fluorescent pericytes that can be isolated via flow cytometry in order to recover vector genomes, we performed three rounds of screening and identified seven putative mutants capable of transducing retinal pericytes.ResultsFollowing intravitreal administration of mutant vectors packaging ubiquitously expressing green fluorescent protein reporters and postmortem flow cytometry of enzymatically digested retinae, two mutants in particular, Peri-E and Peri-G, demonstrated significantly greater transduction of retinal pericytes than unmodified rAAV2/2 (1.4-fold and 2.8-fold, respectively).ConclusionsAlthough difficult to characterize the effect of each point mutation in the context of multiple amino acid variations from the wild-type AAV2 sequence, we identified several point mutations that may play critical roles in limiting HSPG binding, evading neutralization by murine A20 monoclonal antibodies, modulating antigenicity, and evading ubiquitination to ultimately improve transduction efficiency of retinal pericytes.Translational RelevanceIdentification of novel retinal pericyte targeting rAAV vectors enables the development of new, long-lasting gene therapies for retinal diseases such as diabetic retinopathy and wet age-related macular degeneration.

Endothelial Cell Transcytosis Assay as an In Vitro Model to Evaluate Inner Blood-Retinal Barrier Permeability.

Dysfunction of the blood-retinal barrier (BRB) contributes to the pathophysiology of several vascular eye diseases, often resulting in retinal edema and subsequent vision loss. The inner blood-retinal barrier (iBRB) is mainly composed of retinal vascular endothelium with low permeability under physiological conditions. This feature of low permeability is tightly regulated and maintained by low rates of paracellular transport between adjacent retinal microvascular endothelial cells, as well as transcellular transport (transcytosis) through them. The assessment of retinal transcellular barrier permeability may provide fundamental insights into iBRB integrity in health and disease. In this study, we describe an endothelial cell (EC) transcytosis assay, as an in vitro model for evaluating iBRB permeability, using human retinal microvascular endothelial cells (HRMECs). This assay assesses the ability of HRMECs to transport transferrin and horseradish peroxidase (HRP) in receptor- and caveolae-mediated transcellular transport processes, respectively. Fully confluent HRMECs cultured on porous membrane were incubated with fluorescent-tagged transferrin (clathrin-dependent transcytosis) or HRP (caveolae-mediated transcytosis) to measure the levels of transferrin or HRP transferred to the bottom chamber, indicative of transcytosis levels across the EC monolayer. Wnt signaling, a known pathway regulating iBRB, was modulated to demonstrate the caveolae-mediated HRP-based transcytosis assay method. The EC transcytosis assay described here may provide a useful tool for investigating the molecular regulators of EC permeability and iBRB integrity in vascular pathologies and for screening drug delivery systems.

Eye and SARS-CoV-2 in 2022

The ocular symptoms of COVID-19 are rare, however, the most common is conjunctivitis. Retinal changes, including dilated veins, tortuous blood vessels, intraretinal hemorrhages, and cotton balls are much less common. In addition, there may be swelling of the eyelids, their irritation, most often in combination with conjunctival hyperemia. Moreover, COVID-19 infection may be accompanied by different neuro-ophthalmic disorders and, in rare cases, by mucormycosis. Various ocular complications have been reported following vaccination against COVID-19, including facial nerve palsy, abduction nerve palsy, acute macular neuro-retinopathy, superior ocular vein thrombosis, corneal transplant rejection, membrane inflammation vascular eye disease, central serous chorioretinopathy, reactivation of Vogt-Koyanagi-Harada disease and onset of Graves’ disease. Chemical eye injuries in children caused by hand sanitizers have also been reported. Although numerous studies have confirmed the antiviral activity of benzalkonium chloride, its role in this regard requires further research.

Choroidal melanocytic lesions in children: focal aggregates and melanocytosis

To investigate prevalence and age of onset of choroidal melanocytic lesions (other than nevi) in pediatric patients. The pooled data of participants 6 months to 18 years of age in the Sydney Paediatric Eye Disease Study, the Sydney Myopia Study, and the Sydney Adolescent Vascular Eye Disease Study were reviewed retrospectively to identify children with choroidal melanocytic lesions. The clinical features and prevalence by age were assessed. From the pooled sample of 5,533 unique children, 39 cases of focal melanocytic aggregates and 22 cases of choroidal melanocytosis were identified, with overall prevalence of 0.70% and 0.40%, respectively. There was a statistically significant trend toward increased prevalence with increasing age. Both focal melanocytic aggregates and choroidal melanocytosis tended to be bilateral (100% and 86% respectively), brown in color, and temporally located in all cases. Amelanotic variants were not identified. Focal melanocytic aggregates were small (0.15-0.5 mm), whereas choroidal melanocytosis varied in size (5.0-20 mm). All focal melanocytic aggregates were characteristically located 4-5 mm temporal to the center ofthe fovea and were associated with linear nervelike (11 [28%]) or tortuous vessel like structures (10 [26%]). In this study, pooled data from large population studies revealed morphologic patterns of choroidal melanocytic lesions, other than nevus, that correlate with described clinicalappearance in adults. The association of focal melanocytic aggregates with nervelike structures supports their embryologic origin along the migration path of uveal melanocytes.

Quantification of retinal blood leakage in fundus fluorescein angiography in a retinal angiogenesis model

Blood leakage from the vessels in the eye is the hallmark of many vascular eye diseases. One of the preclinical mouse models of retinal blood leakage, the very-low-density-lipoprotein receptor deficient mouse (Vldlr−/−), is used for drug screening and mechanistic studies. Vessel leakage is usually examined using Fundus fluorescein angiography (FFA). However, interpreting FFA images of the Vldlr−/− model is challenging as no automated and objective techniques exist for this model. A pipeline has been developed for quantifying leakage intensity and area including three tasks: (i) blood leakage identification, (ii) blood vessel segmentation, and (iii) image registration. Morphological operations followed by log-Gabor quadrature filters were used to identify leakage regions. In addition, a novel optic disk detection algorithm based on graph analysis was developed for registering the images at different timepoints. Blood leakage intensity and area measured by the methodology were compared to ground truth quantifications produced by two annotators. The relative difference between the quantifications from the method and those obtained from ground truth images was around 10% ± 6% for leakage intensity and 17% ± 8% for leakage region. The Pearson correlation coefficient between the method results and the ground truth was around 0.98 for leakage intensity and 0.94 for leakage region. Therefore, we presented a computational method for quantifying retinal vascular leakage and vessels using FFA in a preclinical angiogenesis model, the Vldlr−/− model.

Choroidal nevi in children: prevalence, age of onset, and progression

To determine the age of onset and prevalence of choroidal nevi in children. In this cross-sectional study, the fundus photographs of a pooled sample of children 6months to 18years of age with 6-year longitudinal follow-up who participated in the Sydney Paediatric Eye Disease Study, Sydney Myopia Study, and the Sydney Adolescent Vascular Eye Disease Study were reviewed. Prevalence by age, clinical features, and longitudinal follow-up assessment was undertaken. Of 5,533 children (7,059 examinations), 48 children with a choroidal nevus were identified. Prevalence increased with age: <6years, 0.47%; 6years, 0.63%; 12years, 1.06%; 18years, 1.79%. Nevus was unilateral in all cases (100%), and the majority were melanotic (46, 96%). Most (36 [75%]) were irregular in shape, with ill-defined margins (45 [94%]). All identified nevi were posterior to the equator. All nevi were small, with the average largest basal diameter of 1.6mm (range, 0.5-3.2) and were not associated with secondary changes (drusen, orange pigment, subretinal fluid). The majority (18/31 [58%]) of nevi remained stable, with 5 of 31 (16%) demonstrating subtle growth (minimum of 600μm). Four new-onset nevi were documented. Malignant transformation was not observed in any of the nevi. In our study cohort, the prevalence of choroidal nevi increased with age up to 18years. The distribution and prevalence of choroidal melanocytic lesions reported herein can be used for designing population-based studies in children that incorporate emerging imaging technologies.

New mathematical method for automating the analysis of fluorescein angiograms of the human fundus

To develop a method for automatic analysis of angiographic images of the fundus for early diagnosis of vascular disorders and complications in a number of ophthalmic diseases. Initial angiograms of patients (n=117) with vascular eye diseases and in healthy condition were analyzed in automatic mode using a new mathematical approach to digital processing of fundus fluorescein angiograms based on a three-stage algorithm for extracting information from images. A new mathematical method has been developed for the analysis fluorescein angiograms allowing for more complete results than with visual inspection of images, with image processing taking no more than 1 second in automatic mode. The developed method is based on fundamental results of the mathematical theory of image analysis and the joint use of image processing methods, mathematical morphology and mathematical statistics. The article introduces software implementations of the developed methods and presents the automated workplace of an ophthalmologist researcher.

Макулярный отек на фоне окклюзий ретинальных вен. Особенности морфометрии макулы и хориоретинальной гемодинамики

This review article summarizes current data on the pathogenesis of macular edema after retinal vein occlusions (RVOs) and patterns of macular morphometry and chorioretinal hemodynamics. RVOs account for 60% of acute vascular eye diseases. The major cause of vision loss in RVOs is macular edema which results from subclinical inflammation characterized by leukostasis and enhanced expression of adhesion molecules and production of cytokines increasing retinal capillary permeability. The association between the severity of macular edema and vitreous levels of pro-inflammatory mediators (IL-1β, IL-6, TNF-α, MCP-1, and VEGF) is established. Cystic lesions and detachment of the neuroepithelium (75%) are typical for macular edema after RVOs. Impaired chorioretinal hemodynamics (as demonstrated by a significant reduction of vascular density in the superficial and deep vascular plexus, significant decrease in peak diastolic flow velocity, and increase in resistivity index in the ophthalmic artery and short posterior ciliary arteries) is also reported. The paper addresses etiological factors of RVOs and pathogenesis of macular edema, technical tools for vital assessment of the retina, and choroidal/retinal hemodynamics. This provides great opportunities for a complex in-depth study of the development and course of macular edema to identify potential predictors of its development and persistence. Keywords: retinal vein occlusions, macular edema, morphometry, chorioretinal hemodynamics. For citation: Fil' A.A., Sorokin E.L., Kolenko O.V. Macular edema after retinal vein occlusions. Macular morphometry and chorioretinal hemodynamics. Russian Journal of Clinical Ophthalmology. 2021;21(3):164–168 (in Russ.). DOI: 10.32364/2311-7729-2021-21-3- 164-168.

Repeatability and Reproducibility of Total Retinal Blood Flow Measurements Using Bi-Directional Doppler OCT.

PurposeTo investigate the repeatability and reproducibility of total retinal blood flow measurements using a custom-built dual-beam bidirectional Doppler optical coherence tomography (OCT) system in healthy subjects.MethodsRepeatability and reproducibility were analyzed in 10 and 34 healthy subjects, respectively. For repeatability, measurements were taken twice within 30 minutes, for reproducibility, twice within two to five weeks. Two analysis approaches were compared for calculation of absolute blood velocities: a previously published approach resulting in values for total arterial (QA,abs) and total venous blood flow (QV,abs) and a novel approach taking into account that there is a fixed relation between the phase shift in the two OCT channels (QA,new, QV,new). Repeatability and reproducibility were quantified using intraclass correlation coefficients (ICCs).ResultsFor QA,abs and QV,abs, ICC values between 0.78 and 0.84 were obtained. QA,new and QV,new values revealed better repeatability and reproducibility as compared to the convential appoach. Repeatability ICCs for QA,new and QV,new were between 0.91 and 0.93, and reproducibility ICCs were between 0.87 and 0.91 indicating excellent reproducibility. Good agreement was observed between total retinal blood flow values as measured from retinal arteries and retinal veins.ConclusionsMeasurement of total retinal blood flow using dual-beam Doppler OCT shows excellent reproducibility, which can further be improved by using a novel algorithm for calculating blood velocities in retinal vessels.Translational RelevanceOur data indicate that dual-beam Doppler OCT can be used for longitudinal studies. Hence, quantitative retinal blood flow may be established as a biomarker for progression vascular eye diseases.

Vitamin-D3 (α-1, 25(OH) 2D3) Protects Retinal Pigment Epithelium From Hyperoxic Insults.

PurposeOxidative stress affects the retinal pigment epithelium (RPE) leading to development of vascular eye diseases. Cholecalciferol (VIT-D) is a known modulator of oxidative stress and angiogenesis. This in vitro study was carried out to evaluate the protective role of VIT-D on RPE cells incubated under hyperoxic conditions.MethodsCadaver primary RPE (PRPE) cells were cultured in hyperoxia (40% O2) with or without VIT-D (α-1, 25(OH) 2D3). The functional and physiological effects of PRPE cells with VIT-D treatment were analyzed using molecular and biochemical tools.ResultsVascular signaling modulators, such as vascular endothelial growth factor (VEGF) and Notch, were reduced in hyperoxic conditions but significantly upregulated in the presence of VIT-D. Additionally, PRPE conditioned medium with VIT-D induced the tubulogenesis in primary human umbilical vein endothelial cells (HUVEC) cells. VIT-D supplementation restored phagocytosis and transmembrane potential in PRPE cells cultured under hyperoxia.ConclusionsVIT-D protects RPE cells and promotes angiogenesis under hyperoxic insult. These findings may give impetus to the potential of VIT-D as a therapeutic agent in hyperoxia induced retinal vascular diseases.

Serum Fibroblast Growth Factor 21 in Patients with and without Pterygia.

PurposePterygium is a common fibro-vascular-related eye disease. The fibroblast growth factor 21 (FGF21) helps reduce neovascularization. Previous studies have shown that the serum level of FGF21 correlates with vascular eye diseases such as diabetic retinopathy and retinopathy of prematurity. In this study, the serum FGF21 is compared in patients with and without pterygium.Methods This descriptive-analytical cross-sectional study examines individuals with pterygium who visited the Ophthalmology Clinic of Khatam-al-Anbia Hospital in Mashhad, Iran, during 2017–2018. Control subjects were selected from healthy people without pterygium disease. Patients with a history of acute illness, chronic liver and kidney disease, diabetes, cancer, malnutrition and drug use, women who were pregnant or breastfeeding, and subjects who were taking anticonvulsants or glucocorticoids were excluded as these may affect insulin and glycosuria levels. Sixty people (30 in each group) were chosen using the convenient sampling method. Intravenous blood samples were taken from all patients. After preparing the patients, the freeze was checked using the enzyme-linked immunosorbent assay (ELISA) method after samples had been taken. Data were analyzed by SPSS using an independent t-test, Mann–Whitney, Chi-square, Kruskal–Wallis, and Kolmogorov–Smirnov tests ( = 0.05).ResultsThe serum FGF21 levels were 319.09 246.93 pg/ml and 608.88 449.81 pg/ml (P = 0.005) in the pterygium group and control subjects, respectively. The average serum FGF21 was 281.55 40.74 pg/ml in males and 361.375 10.298 pg/ml in females in the pterygium group. The difference was not statistically significant (P = 0.19)ConclusionOur study showed that FGF21 levels were lower in patients with pterygium than the control subjects to a statistically significant level.

MicroRNAs in Vascular Eye Diseases.

Since the discovery of the first microRNA (miRNA) decades ago, studies of miRNA biology have expanded in many biomedical research fields, including eye research. The critical roles of miRNAs in normal development and diseases have made miRNAs useful biomarkers or molecular targets for potential therapeutics. In the eye, ocular neovascularization (NV) is a leading cause of blindness in multiple vascular eye diseases. Current anti-angiogenic therapies, such as anti-vascular endothelial growth factor (VEGF) treatment, have their limitations, indicating the need for investigating new targets. Recent studies established the roles of various miRNAs in the regulation of pathological ocular NV, suggesting miRNAs as both biomarkers and therapeutic targets in vascular eye diseases. This review summarizes the biogenesis of miRNAs, and their functions in the normal development and diseases of the eye, with a focus on clinical and experimental retinopathies in both human and animal models. Discovery of novel targets involving miRNAs in vascular eye diseases will provide insights for developing new treatments to counter ocular NV.

Wnt Signaling in vascular eye diseases.

The Wnt signaling pathway plays a pivotal role in vascular morphogenesis in various organs including the eye. Wnt ligands and receptors are key regulators of ocular angiogenesis both during the eye development and in vascular eye diseases. Wnt signaling participates in regulating multiple vascular beds in the eye including regression of the hyaloid vessels, and development of structured layers of vasculature in the retina. Loss-of-function mutations in Wnt signaling components cause rare genetic eye diseases in humans such as Norrie disease, and familial exudative vitreoretinopathy (FEVR) with defective ocular vasculature. On the other hand, experimental studies in more prevalent vascular eye diseases, such as wet age-related macular degeneration (AMD), diabetic retinopathy (DR), retinopathy of prematurity (ROP), and corneal neovascularization, suggest that aberrantly increased Wnt signaling is one of the causations for pathological ocular neovascularization, indicating the potential of modulating Wnt signaling to ameliorate pathological angiogenesis in eye diseases. This review recapitulates the key roles of the Wnt signaling pathway during ocular vascular development and in vascular eye diseases, and pharmaceutical approaches targeting the Wnt signaling as potential treatment options.

The potent small molecule integrin antagonist THR-687 is a promising next-generation therapy for retinal vascular disorders

Integrins are associated with various eye diseases such as diabetic retinopathy (DR) and wet age-related macular degeneration (AMD) and implicated in main pathologic disease hallmarks like neovascularization, inflammation, fibrosis and vascular leakage. Targeting integrins has the potential to attenuate these vision-threatening processes, independent of anti-vascular endothelial growth factor (VEGF) responsiveness. The current investigation characterized THR-687 as a novel pan RGD (arginylglycylaspartic acid) integrin receptor antagonist able to compete for binding with the natural ligand with nanomolar potency (e.g. αvβ3 (IC50 of 4.4 ± 2.7 nM), αvβ5 (IC50 of 1.3 ± 0.5 nM) and α5β1 (IC50 of 6.8 ± 3.2 nM)). THR-687 prevented the migration of human umbilical vein endothelial cells (HUVECs) into a cell-free area (IC50 of 258 ± 113 nM) as well as vessel sprouting in an ex vivo mouse choroidal explant model (IC50 of 236 ± 173 nM), and was able to induce the regression of pre-existing vascular sprouts. Moreover, combined intravitreal and intraperitoneal administration of THR-687 potently inhibited VEGF-induced leakage in the mouse retina. In addition, THR-687 injected intravitreally at 3 different dose levels (0.45 mg, 2.25 mg or 4.5 mg/eye) potently inhibited neovascularization-induced leakage in the cynomolgus laser-induced choroidal neovascularization (CNV) model.These data suggest that THR-687 is a promising drug candidate for the treatment of vision-threatening retinal vascular eye diseases such as DR and wet AMD.

Intraocular Penetration of a vNAR: In Vivo and In Vitro VEGF165 Neutralization.

Variable new antigen receptor domain (vNAR) antibodies are novel, naturally occurring antibodies that can be isolated from naïve, immune or synthetic shark libraries. These molecules are very interesting to the biotechnology and pharmaceutical industries because of their unique characteristics related to size and tissue penetrability. There have been some approved anti-angiogenic therapies for ophthalmic conditions, not related to vNAR. This includes biologics and chimeric proteins that neutralize vascular endothelial growth factor (VEGF)165, which are injected intravitreal, causing discomfort and increasing the possibility of infection. In this paper, we present a vNAR antibody against human recombinant VEGF165 (rhVEGF165) that was isolated from an immunized Heterodontus francisci shark. A vNAR called V13, neutralizes VEGF165 cytokine starting at 75 μg/mL in an in vitro assay based on co-culture of normal human dermal fibroblasts (NHDFs) and green fluorescence protein (GFP)-labeled human umbilical vein endothelial cells (HUVECs) cells. In the oxygen-induced retinopathy model in C57BL/6:Hsd mice, we demonstrate an endothelial cell count decrease. Further, we demonstrate the intraocular penetration after topical administration of 0.1 μg/mL of vNAR V13 by its detection in aqueous humor in New Zealand rabbits with healthy eyes after 3 h of application. These findings demonstrate the potential of topical application of vNAR V13 as a possible new drug candidate for vascular eye diseases.

MEDICAL AND SOCIAL ISSUES OF OCCUPATIONAL REHABILITATION IN ELDERLY PATIENTS WITH VASCULAR OPHTHALMOPATHY

Цель – определение медико-социальных особенностей профессиональной реабилитации лиц пожилого возраста, страдающих сосудистыми заболеваниями глаз.

Endothelial microRNA-150 is an intrinsic suppressor of pathologic ocular neovascularization

Pathologic ocular neovascularization commonly causes blindness. It is critical to identify the factors altered in pathologically proliferating versus normally quiescent vessels to develop effective targeted therapeutics. MicroRNAs regulate both physiological and pathological angiogenesis through modulating expression of gene targets at the posttranscriptional level. However, it is not completely understood if specific microRNAs are altered in pathologic ocular blood vessels, influencing vascular eye diseases. Here we investigated the potential role of a specific microRNA, miR-150, in regulating ocular neovascularization. We found that miR-150 was highly expressed in normal quiescent retinal blood vessels and significantly suppressed in pathologic neovessels in a mouse model of oxygen-induced proliferative retinopathy. MiR-150 substantially decreased endothelial cell function including cell proliferation, migration, and tubular formation and specifically suppressed the expression of multiple angiogenic regulators, CXCR4, DLL4, and FZD4, in endothelial cells. Intravitreal injection of miR-150 mimic significantly decreased pathologic retinal neovascularization in vivo in both wild-type and miR-150 knockout mice. Loss of miR-150 significantly promoted angiogenesis in aortic rings and choroidal explants ex vivo and laser-induced choroidal neovascularization in vivo. In conclusion, miR-150 is specifically enriched in quiescent normal vessels and functions as an endothelium-specific endogenous inhibitor of pathologic ocular neovascularization.

Endothelial TWIST1 promotes pathological ocular angiogenesis.

Pathological neovessel formation impacts many blinding vascular eye diseases. Identification of molecular signatures distinguishing pathological neovascularization from normal quiescent vessels is critical for developing new interventions. Twist-related protein 1 (TWIST1) is a transcription factor important in tumor and pulmonary angiogenesis. This study investigated the potential role of TWIST1 in modulating pathological ocular angiogenesis in mice. Twist1 expression and localization were analyzed in a mouse model of oxygen-induced retinopathy (OIR). Pathological ocular angiogenesis in Tie2-driven conditional Twist1 knockout mice were evaluated in both OIR and laser-induced choroidal neovascularization models. In addition, the effects of TWIST1 on angiogenesis and endothelial cell function were analyzed in sprouting assays of aortic rings and choroidal explants isolated from Twist1 knockout mice, and in human retinal microvascular endothelial cells treated with TWIST1 small interfering RNA (siRNA). TWIST1 is highly enriched in pathological neovessels in OIR retinas. Conditional Tie2-driven depletion of Twist1 significantly suppressed pathological neovessels in OIR without impacting developmental retinal angiogenesis. In a laser-induced choroidal neovascularization model, Twist1 deficiency also resulted in significantly smaller lesions with decreased vascular leakage. In addition, loss of Twist1 significantly decreased vascular sprouting in both aortic ring and choroid explants. Knockdown of TWIST1 in endothelial cells led to dampened expression of vascular endothelial growth factor receptor 2 (VEGFR2) and decreased endothelial cell proliferation. Our study suggests that TWIST1 is a novel regulator of pathologic ocular angiogenesis and may represent a new molecular target for developing potential therapeutic treatments to suppress pathological neovascularization in vascular eye diseases.