Decreased endostatin in db/db retinas is associated with optic disc intravitreal vascularization.

Endostatin, a naturally cleaved fragment of type XVIII collagen with antiangiogenic activity, has been involved in the regulation of neovascularization during diabetic retinopathy. Here, the intracellular distribution of endostatin in healthy mouse and human neuroretinas has been analyzed. In addition, to study the effect of experimental hyperglycemia on retinal endostatin, the db/db mouse model has been used. Endostatin protein expression in mouse and human retinas was studied by immunofluorescence and Western blot, and compared with db/db mice. Eye fundus angiography, histology, and immunofluorescence were used to visualize mouse retinal and intravitreal vessels. For the first time, our results revealed the presence of endostatin in neurons of mouse and human retinas. Endostatin was mainly expressed in bipolar cells and photoreceptors, in contrast to the optic disc, where endostatin expression was undetectable. Diabetic mice showed a reduction of endostatin in their retinas associated with the appearance of intravitreal vessels at the optic disc in 50% of db/db mice. Intravitreal vessels showed GFAP positive neuroglia sheath, basement membrane thickening by collagen IV deposition, and presence of MMP-2 and MMP-9 in the vascular wall. All together, these results point that decreased retinal endostatin during experimental diabetes is associated with optic disc intravitreal vascularization. Based on their phenotype, these intravitreal vessels could be neovessels. However, it cannot be ruled out the possibility that they may also represent persistent hyaloid vessels.

Long-term visual and anatomic outcomes following early surgery for persistent fetal vasculature: a single-center, 20-year review.

BACKGROUND: Persistent fetal vasculature (PFV) is a spectrum of congenital anomalies caused by complete or partial failure of the ocular fetal vasculature to regress. We report the visual and anatomic outcomes in a large cohort of patients who underwent early surgery for PFV. METHODS: We retrospectively reviewed the medical records of patients who underwent lensectomy and anterior or core vitrectomy for unilateral PFV without primary intraocular lens implantation through limbal or pars plana/plicata approach. Inclusion criteria were surgery prior to 7 months of age, with at least 12 months of follow-up. Eyes with severe posterior segment involvement and retinal detachment deemed beyond repair were excluded. RESULTS: A total of 58 patients met inclusion criteria. Mean age at surgery was 2.1 ± 1.5 months. Mean follow-up was 6.7 ± 4.2 years. At final follow-up, 19 eyes (33%) had visual acuity better than 1.0 logMAR. Thirty-three eyes (57%) developed 1 or more postoperative adverse events: glaucoma in 21 (36%) and retinal detachment in 11 (19%), 8 of which occurred in eyes that had pars plana or pars plicata incisions (P = 0.002). In patients with limbal incisions, 17 of 40 (43%) achieved a visual acuity better than 1.0 logMAR, compared with 2 of 18 patients (11%) with a pars plana/pars plicata incision (P = 0.03). CONCLUSIONS: In our study cohort, early surgery for PFV achieved functional visual acuity in about one-third of patients. Limbal approach to surgery may result in better visual acuity and anatomic results.

Comparison between non-visualized polyps and visualized polyps on optical coherence tomography angiography in polypoidal choroidal vasculopathy.

PURPOSE: To determine the underlying reasons for the non-visualization of polyps on en face optical coherence tomography angiography (OCTA) in patients with polypoidal choroidal vasculopathy (PCV). METHODS: A cross-sectional study of consecutive treatment-naïve 30 eyes with active PCV was included. Results of fundus photography, fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), spectral domain optical coherence tomography (SD-OCT), and en face OCTA were analyzed. RESULTS: A total of 64 active polyps were found on FFA and ICGA in 30 eyes. On OCTA, 42/64 (65.6%) polyps were visualized, while 22/64 (34.4%) polyps were non-visualized. There were no significant differences in the size (P = 0.723) and filling time of polyps (P = 0.558) between the two groups. However, polypoidal lesions were less common in the non-visualized group (P < 0.001). The height of the polyps on SD-OCT was 243.95 ± 114.24 µm in the non-visualized group, which was higher than those (188.00 ± 87.93 µm) in the visualized group (P = 0.048). Moreover, more pulsatile polyps (72.7%) were found in the non-visualized group than those (2.4%) in the visualized group (P < 0.001). Four of the 22 polyps in the non-visualized group (18.2%) were located under a thick subretinal hemorrhage, and two of 22 invisible polyps (9.6%) located under and parallel to the retinal vessel in the inner layer of retina. CONCLUSIONS: Our results revealed that the height of the polyps, and not the size and pulsation of the polyps, correlated with the visualization of the polyps on OCTA. Polyps that were pulsating in early ICGA were difficult to be visualized on OCTA, which is the most possible reason for the non-visualization. Coverage with thick subretinal hemorrhage or retina vessels was another reason for the non-visualization of the polyps in active PCV on OCTA.

Bush-like integrin filament networks associated with hyaloid vasculature in murine neonate eyes.

The vitreous of perinatal mice temporarily develops a unique vascular system, called the vasa hyaloidea propria (VHP). Observations showed the vessels possessed an extracellular matrix including the basement membrane in their entire length. Immunostaining of whole mount preparations of VHP with integrin ß1 antibody displayed a bush-like network consisting of long and straight fibers which were associated with the VHP but extended apart from the blood vessels. Electron microscopically, each fiber was composed of a bundle of thin filaments different from collagen fibrils. Macrophages associated with the VHP appeared to be arrested by the integrin bushes. The integrin bushes fragmented and disappeared by postnatal day 10, just before the regression of the VHP. Macrophages were involved in the digestion and clearance of integrin bushes. The vitreous integrin bushes appear to provide a scaffold for architectural maintenance of the hyaloid vessels and macrophages.

Management of severe persistent fetal vasculature: case series and review of the literature.

PURPOSE: Persistent fetal vasculature (PFV) is a unique ocular disorder usually presenting early in life. The unregressed embryonal hyaloid vasculature poses a risk of severe ocular complications leading to decreased visual acuity. Surgery is the mainstay of therapy in complicated cases. We describe the clinical presentation and surgical treatment of PFV managed at our center from 2012 to 2015. METHODS: The study is a case series comprised eight patients who were diagnosed with complicated severe PFV. All were managed with a tailored surgical approach. The clinical characteristics, medical and surgical treatment, and follow-up findings of each case are described. RESULTS: There were six males and two females. Surgical intervention involved anterior or posterior vitrectomy, lens extraction, and intraocular lens implantation. Hyaloid stalk removal with release of ciliary traction was variably utilized in selected cases. Endodiathermy controlled intraocular bleeding, and intraocular scissors proved helpful in anterior PFV for disinserting the ciliary process from an abnormally thickened posterior lens capsule. Visual outcomes differed in each case, depending on multiple clinical factors. CONCLUSION: Severe complex PFV presents a therapeutic challenge. A tailored surgical approach with meticulous postoperative management is essential for visual rehabilitation.

Matrix metalloproteinase-14 is a biomarker of angiogenic activity in proliferative diabetic retinopathy.

Purpose: Matrix metalloproteinase-14 (MMP-14) is a transmembrane MMP that plays a critical role in promoting angiogenesis. We investigated the expression levels of MMP-14 and correlated the levels with clinical disease activity and with the levels of the angiogenic factors vascular endothelial growth factor (VEGF) and MMP-9 in proliferative diabetic retinopathy (PDR). To reinforce the findings at the functional level, we examined the expression of MMP-14 in the retinas of diabetic rats. Methods: Vitreous samples from 34 patients with PDR and 18 nondiabetic patients and epiretinal membranes from 13 patients with PDR and the retinas of rats were studied with enzyme-linked immunosorbent assay, immunohistochemistry, western blotting, and real-time reverse transcription PCR (RT-PCR). Results: The MMP-14, VEGF, and MMP-9 levels were statistically significantly higher in the vitreous samples from patients with PDR than in the samples from the nondiabetic controls (p<0.001 for all comparisons). The MMP-14 levels in patients with PDR with active neovascularization were statistically significantly higher than those in patients with inactive PDR (p<0.001). There were statistically significant positive correlations between levels of MMP-14 and levels of VEGF (r = 0.3; p = 0.032) and MMP-9 (r = 0.54; p<0.001). In the epiretinal membranes, MMP-14 was expressed in vascular endothelial cells, leukocytes, and myofibroblasts. Statistically significant positive correlations were detected between the numbers of blood vessels expressing CD31 and the numbers of blood vessels (r = 0.74; p = 0.004) and stromal cells (r = 0.72; p = 0.005) expressing MMP-14. Statistically significant increases of MMP-14 mRNA and protein were detected in rat retinas after induction of diabetes. Conclusions: These results suggest that MMP-14 is involved in PDR angiogenesis.

Histochemical characteristics of regressing vessels in the hyaloid vascular system of neonatal mice: Novel implication for vascular atrophy.

The hyaloid vasculature constitutes a transitory system nourishing the internal structures of the developing eye, but the mechanism of vascular regression and its cell biological characteristics are not fully understood. The present study aimed to reveal the specificity of the hyaloid vessels by a systematic immunohistochemical approach for marker substances of myeloid cells and the extracellular matrix (ECM) in neonatal mice. Macrophages immunoreactive for F4/80, cathepsin D, and LYVE-1 gathered around the vasa hyaloidea propria (VHP), while small round cells in vascular lumen of VHP were selectively immunoreactive for galectin-3; their segmented nuclei and immunoreactivities for Ly-6G, CD11b, and myeloperoxidase indicated their neutrophilic origin. VHP possessed thick ECM and a dense pericyte envelope as demonstrated by immunostaining for laminin, type IV collagen, integrin ß1, and NG2. The galectin-3+ cells loosely aggregated with numerous erythrocytes in the lumen of hyaloid vessels in a manner reminiscent of vascular congestion. Galectin-3 is known to polymerize and form a complex with ECM and NG2 as well as recruit leukocytes on the endothelium. Observation of galectin-3 KO mice implicated the involvement of galectin-3 in the regression of hyaloid vasculature. Since macrophages may play central roles including blocking of the blood flow and the induction of apoptosis in the regression, galectin-3+ neutrophils may play a supportive role in the macrophage-mediated involution of the hyaloid vascular system.

Pegaptanib: choroidal neovascularization in patients with age-related macular degeneration and previous arterial thromboembolic events.

PURPOSE: To evaluate the efficacy and the rate of side effects of the pegylated aptamer pegaptanib in the treatment of patients with choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) and a history of previous arterial thromboembolic events (ATEs). METHODS: Twenty-three eyes of 23 patients with subfoveal CNV due to AMD and cerebrovascular accidents (n = 12) and myocardial infarction (n = 11) in the previous 6 months received intravitreal pegaptanib 0.3 mg according to a pro re nata regimen and were followed for 12 months. The paired Student t test was used to evaluate mean changes in best-corrected visual acuity (BCVA; primary outcome measure) and central foveal thickness (CFT). RESULTS: The mean patient age was 71.5 ± 4.6 years; there were 14 women and 9 men. The CNV was type 1, 2, and 3 in 18, 3, and 2 eyes, respectively. The mean BCVA improved from 0.67 ± 0.23 logMAR at baseline to 0.52 ± 0.31 logMAR at the end of 12-month follow-up (p = 0.044). Thirty-five percent of patients achieved ≥3 Early Treatment Diabetic Retinopathy Study lines improvement at 12 months. Mean CFT at baseline (381 ± 111 µm) decreased to 304 ± 82 µm at 12 months (p = 0.008). Patients received a mean of 4.3 ± 1.3 (range 3-7) injections. No systemic or ocular side effects occurred; no patient experienced further ATEs. CONCLUSIONS: Intravitreal pegaptanib can be considered a viable treatment option for patients with AMD-related CNV who are at high risk of ATEs.

Development of the hyaloid, choroidal and retinal vasculatures in the fetal human eye.

The development of the ocular vasculatures is perfectly synchronized to provide the nutritional and oxygen requirements of the forming human eye. The fetal vasculature of vitreous, which includes the hyaloid vasculature, vasa hyaloidea propria, and tunica vasculosa lentis, initially develops around 4-6 weeks gestation (WG) by hemo-vasculogenesis (development of blood and blood vessels from a common progenitor, the hemangioblast). This transient fetal vasculature expands around 12 WG by angiogenesis (budding from primordial vessels) and remains until a retinal vasculature begins to form. The fetal vasculature then regresses by apoptosis with the assistance of macrophages/hyalocytes. The human choroidal vasculature also forms by a similar process and will supply nutrients and oxygen to outer retina. This lobular vasculature develops in a dense collagenous tissue juxtaposed with a cell constitutively producing vascular endothelial growth factor (VEGF), the retinal pigment epithelium. This epithelial/endothelial relationship is critical in maintaining the function of this vasculature throughout life and maintaining it's fenestrated state. The lobular capillary system (choriocapillaris) develops first by hemo-vasculogenesis and then the intermediate choroidal blood vessels form by angiogenesis, budding from the choriocapillaris. The human retinal vasculature is the last to develop. It develops by vasculogenesis, assembly of CXCR4+/CD39+ angioblasts or vascular progenitors perhaps using Muller cell Notch1 or axonal neuropilinin-1 for guidance of semaphorin 3A-expressing angioblasts. The fovea never develops a retinal vasculature, which is probably due to the foveal avascular zone area of retina expressing high levels of antiangiogenic factors. From these studies, it is apparent that development of the mouse ocular vasculatures is not representative of the development of the human fetal, choroidal and retinal vasculatures.

Myosin-X knockout is semi-lethal and demonstrates that myosin-X functions in neural tube closure, pigmentation, hyaloid vasculature regression, and filopodia formation.

Myosin-X (Myo10) is an unconventional myosin best known for its striking localization to the tips of filopodia. Despite the broad expression of Myo10 in vertebrate tissues, its functions at the organismal level remain largely unknown. We report here the generation of KO-first (Myo10 tm1a/tm1a ), floxed (Myo10 tm1c/tm1c ), and KO mice (Myo10 tm1d/tm1d ). Complete knockout of Myo10 is semi-lethal, with over half of homozygous KO embryos exhibiting exencephaly, a severe defect in neural tube closure. All Myo10 KO mice that survive birth exhibit a white belly spot, all have persistent fetal vasculature in the eye, and ~50% have webbed digits. Myo10 KO mice that survive birth can breed and produce litters of KO embryos, demonstrating that Myo10 is not absolutely essential for mitosis, meiosis, adult survival, or fertility. KO-first mice and an independent spontaneous deletion (Myo10 m1J/m1J ) exhibit the same core phenotypes. During retinal angiogenesis, KO mice exhibit a ~50% decrease in endothelial filopodia, demonstrating that Myo10 is required to form normal numbers of filopodia in vivo. The Myo10 mice generated here demonstrate that Myo10 has important functions in mammalian development and provide key tools for defining the functions of Myo10 in vivo.

Nanoparticle-protein complexes mimicking corona formation in ocular environment.

Nanoparticles adsorb biomolecules to form corona upon entering the biological environment. In this study, tissue-specific corona formation is provided as a way of controlling protein interaction with nanoparticles in vivo. In the vitreous, the composition of the corona was determined by the electrostatic and hydrophobic properties of the associated proteins, regardless of the material (gold and silica) or size (20- and 100-nm diameter) of the nanoparticles. To control protein adsorption, we pre-incubate 20-nm gold nanoparticles with 5 selectively enriched proteins from the corona, formed in the vitreous, to produce nanoparticle-protein complexes. Compared to bare nanoparticles, nanoparticle-protein complexes demonstrate improved binding to vascular endothelial growth factor (VEGF) in the vitreous. Furthermore, nanoparticle-protein complexes retain in vitro anti-angiogenic properties of bare nanoparticles. In particular, priming the nanoparticles (gold and silica) with tissue-specific corona proteins allows nanoparticle-protein complexes to exert better in vivo therapeutic effects by higher binding to VEGF than bare nanoparticles. These results suggest that controlled corona formation that mimics in vivo processes may be useful in the therapeutic use of nanomaterials in local environment.

Combined Persistent Fetal Vasculature: A Classification Based on High-Resolution B-Mode Ultrasound and Color Doppler Imaging.

PURPOSE: The purpose of this study was to classify combined persistent fetal vasculature (PFV) on the basis of the ultrasonographic and Doppler characteristics. The potential clinical significance for both surgery design and prognosis determination was discussed. DESIGN: A cross-sectional case series. PARTICIPANTS: The eyes of 54 children diagnosed with unilateral combined PFV were evaluated using B-mode ultrasound and color Doppler imaging (CDI). METHODS: Each participant's age at first presentation, diagnosis for referral, gender, family history, and systemic or other ocular anomalies were recorded. Retinal detachment, optic nerve abnormalities, and macular dislocation were also recorded in detail according to the RetCam (Clarity Medical Systems, Pleasanton, CA), ultrasound, and Doppler findings. The PFV eyes were divided into 4 groups on the basis of the ultrasound and CDI findings. Intergroup analysis was performed. MAIN OUTCOME MEASURES: Overall and intergroup analyses of the demographic features of the children with PFV were performed. The axial length, depth of the anterior chamber, and lens thickness were compared between the affected eyes and the fellow healthy eyes among the 4 groups. RESULTS: Some 22.2%, 18.5%, 33.3%, and 25.9% of the eyes were grouped into type I ("I" shape), II ("Y" shape), III (inverted "Y" shape), and IV ("X" shape) combined PFV, respectively. The age at first presentation for type I was older than that for the other groups (P = 0.014). The axial length was reduced (P = 0.012) and the anterior chamber more shallow (P = 0.011) than in fellow healthy eyes for type IV eyes, but not for the other 3 groups. CONCLUSIONS: Ultrasound and CDI are informative screening and diagnostic tools that show characteristic flow patterns in the 4 types of combined PFV. This novel classification system provides new and important information for the diagnosis of PFV and, if validated, may play a role in guiding treatment recommendations in the future.

Clinical and histological characteristics of canine ocular gliovascular syndrome.

OBJECTIVE: To characterize the clinical, diagnostic, and histopathologic findings in dogs with canine ocular gliovascular syndrome (COGS). PROCEDURES: The archives at the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) were used to identify eyes with COGS. Histopathological inclusion criteria included: a neovascular membrane extending from the optic nerve head or retina, clusters of spindle cells lacking vascularization within the vitreous, and histological signs of glaucoma. Special and immunohistochemical (IHC) staining techniques were performed. Clinical data, treatments, and outcomes were obtained from case records and information provided by submitting veterinarians. RESULTS: Thirty-seven eyes of 36 dogs were identified with COGS. The average age at diagnosis was 8.8 years (±2.2). The relative risk for a Labrador retriever affected by COGS was significantly greater (9.3 times) (P < 0.0001) when compared to all other dog breeds within the COPLOW database. Most dogs presented with hyphema and secondary glaucoma; average intraocular pressure was 39 mmHg (±19). Average time to enucleation or evisceration was 27 days. Vitreal cells stained positive with IHC for glial fibrillary acidic protein in 14 of 17 globes, and vascular endothelial growth factor was expressed in the vitreal cells in five of five globes. CONCLUSIONS: We have defined a syndrome associated with vitreal glial cell aggregates and neovascular proliferation from the optic nerve or retina, which leads to neovascular glaucoma. The inflammation and secondary glaucoma resulting from this syndrome appear poorly responsive to conventional medical therapies. The exact etiology of COGS remains undetermined, but a systemic etiology is unlikely.

Posterior tunica vasculosa lentis and "brittle star" of persistent fetal vasculature.

A 17-month-old girl referred for a suspected ciliary body medulloepithelioma was found to have persistent fetal vasculature. Fluorescein angiography showed perfused hyaloid artery posterior tunica vasculosa lentis with brittle star appearance and nonperfused anterior pupillary membrane. Ultrasound biomicroscopy confirmed absence of iris or ciliary body solid tumor.

Semaphorin 3A blocks the formation of pathologic choroidal neovascularization induced by transforming growth factor beta.

OBJECTIVE: Choroidal neovascularization (CNV) is a major cause of vision loss in retinal diseases such as age-related macular degeneration (AMD). Previously, we demonstrated that semaphorin3A (Sema3A), which is a chemorepellent guidance molecule, inhibited the formation of retina neovascularization. In the present study, we investigated the antiangiogenic effects of Sema3A on transforming growth factor beta (TGF-ß) in vitro and in vivo. METHODS: Enzyme-linked immunosorbent assays (ELISAs) were used to measure the TGF-ß levels in the vitreous humor of patients with AMD and controls. Human umbilical vein endothelial cells (HUVECs) were used for the in vitro study, and a laser-induced CNV mouse model was prepared for the in vivo study. The HUVECs were incubated with TGF-ß and Sema3A. The proliferation, migration, apoptosis, and tube formation of the cells were then measured using BrdU, Transwell, flow cytometry, and Matrigel assays, respectively, and the SMAD2/3 signaling pathways were analyzed using western blot analysis. The C57BL/6J mouse retina was exposed to a laser to induce choroidal neovascularization (CNV), and Sema3A was injected intravitreously. After 14 days, fundus fluorescein angiography was performed to evaluate the leakage area of the CNV. The vascular endothelial growth factor (VEGF) and TGF-ß concentrations in the retina-choroid complex were measured with ELISA. Components of the p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase-1/2 (ERK1/2), c-Jun NH2-terminal kinase (JNK), and SMAD2/3 signaling pathways in the Sema3A-treated groups were analyzed using western blotting. RESULTS: In this study, we first verified that the vitreous TGF-ß level was higher in patients with neovascular AMD than in the controls. We also showed that Sema3A inhibited TGF-ß-induced HUVEC proliferation, migration, and tube formation and inhibited the downstream SMAD2/3 signaling pathway. Sema3A also induced TGF-ß-stimulated HUVEC apoptosis and inhibited the response of TGF-ß in vitro. In vivo, the TGF-ß level was increased in the CNV mouse model. Sema3A not only inhibited laser-induced CNV formation but also inhibited the uptake of VEGF and TGF-ß. In the western blot analysis, Sema3A was shown to inhibit the phosphorylation of p38 MAPK, ERK1/2, and JNK and to inhibit the SMAD2/3 signaling pathway after Sema3A treatment in CNV mice. CONCLUSIONS: Sema3A can be applied as a useful, adjunctive therapeutic strategy for preventing CNV formation.

Endothelial NADPH oxidase 4 mediates vascular endothelial growth factor receptor 2-induced intravitreal neovascularization in a rat model of retinopathy of prematurity.

PURPOSE: NADPH oxidase-generated reactive oxygen species (ROS) are implicated in angiogenesis. Isoforms of NADPH oxidase NOX1, NOX2, and NOX4 are reported to be expressed in endothelial cells (ECs). Of these, NOX1 and NOX2 have been reported to contribute to intravitreal neovascularization (IVNV) in oxygen-induced retinopathy (OIR) models. In this study, we tested the hypothesis that the isoform NOX4 in ECs contributed to vascular endothelial growth factor (VEGF)-induced angiogenesis and IVNV. METHODS: Isoforms of NADPH oxidase MRNA were measured in several types of cultured vascular ecs: human retinal microvascular ECs (hRMVECs), choroidal ECs (CECs), and human umbilical vascular ECs (HUVECs) using real-time PCR. Newborn rat pups and dams were placed into an OIR model that cycled oxygen concentration between 50% and 10% every 24 h for 14 days, and then were placed in room air (RA) for an additional 4 days (rat OIR model). NOX4 expression in retinal lysates from the RA-raised pups at postnatal day 0 (P0), P14, and P18 was determined with western blots. STAT3 activation was determined as the ratio of phosphorylated STAT3 to total STAT3 with western blot analysis of retinal lysates from pups raised in RA or from the rat OIR model at P18. Semiquantitative assessment of the density of NOX4 colabeling with lectin-stained retinal ECs was determined by immunolabeling of retinal cryosections from P18 pups in OIR or in RA. In hRMVECs transfected with NOX4 siRNA and treated with VEGF or control, 1) ROS generation was measured using the 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate, acetyl ester fluorescence assay and 2) phosphorylated VEGF receptor 2 and STAT3, and total VEGFR2 and STAT3 were measured in western blot analyses. VEGF-stimulated hRMVEC proliferation was measured following transfection with NOX4 siRNA or STAT3 siRNA, or respective controls. RESULTS: NOX4 was the most prevalent isoform of NADPH oxidase in vascular ECs. NOX4 expression in retinal lysates was significantly decreased during development in RA. Compared to RA, the expression of retinal NOX4 increased at P18. At p18 OIR, semiquantitative assessment of the density of lectin and NOX4 colabeling in retinal vascular ECs was greater in retinal cryosections and activated STAT3 was greater in retinal lysates when compared to the RA-raised pups. In cultured hRMVECs, knockdown of NOX4 by siRNA transfection inhibited VEGF-induced ROS generation. VEGF induced a physical interaction of phosphorylated-VEGFR2 and NOX4. Knockdown of NOX4: 1) reduced VEGFR2 activation but did not abolish it and 2) abolished STAT3 activation in response to VEGF. Knockdown of either NOX4 or STAT3 inhibited VEGF-induced EC proliferation. CONCLUSIONS: Our data suggest that in a model representative of human retinopathy of prematurity, NOX4 was increased at a time point when IVNV developed. VEGF-activated NOX4 led to an interaction between VEGF-activated VEGFR2 and NOX4 that mediated EC proliferation via activation of STAT3. Altogether, our results suggest that NOX4 may regulate VEGFR2-mediated IVNV through activated STAT3.