Genome-wide association identifies novel ROP risk loci in a multiethnic cohort.

We conducted a genome-wide association study (GWAS) in a multiethnic cohort of 920 at-risk infants for retinopathy of prematurity (ROP), a major cause of childhood blindness, identifying 1 locus at genome-wide significance level (p < 5×10-8) and 9 with significance of p < 5×10-6 for ROP ≥ stage 3. The most significant locus, rs2058019, reached genome-wide significance within the full multiethnic cohort (p = 4.96×10-9); Hispanic and European Ancestry infants driving the association. The lead single nucleotide polymorphism (SNP) falls in an intronic region within the Glioma-associated oncogene family zinc finger 3 (GLI3) gene. Relevance for GLI3 and other top-associated genes to human ocular disease was substantiated through in-silico extension analyses, genetic risk score analysis and expression profiling in human donor eye tissues. Thus, we identify a novel locus at GLI3 with relevance to retinal biology, supporting genetic susceptibilities for ROP risk with possible variability by race and ethnicity.

Extending Peripheral Retinal Vascularization in Retinopathy of Prematurity Through Regulation of VEGF Signaling.

PURPOSE: Experimental studies provide evidence that regulation of VEGF receptor-2 signaling in endothelial cells orders cell divisions and extends developmental angiogenesis while inhibiting pathologic intravitreal angiogenesis and has relevance to retinopathy of prematurity (ROP). We tested the hypothesis that intravitreal anti-VEGF would extend vascularization into peripheral avascular retina in human type 1 ROP compared with controls. DESIGN: Retrospective, nonrandomized treatment comparison. METHODS: The study was conducted at an academic institution, with the study population comprising all premature infants screened for ROP from January 2019 through December 2022. The experimental group included type 1 ROP treated with bilateral bevacizumab (0.25 mg) and had adequate fundus imaging by a certified ophthalmic photographer at 2 examinations: within 2 weeks of treatment and 1-3 weeks later. A control group included gestational age- and birthweight-matched infants with ROP less severe than type 1 ROP. The main outcome measure was extent of temporal retinal vasculature measured by a masked analyst between treated and control eyes. Paired and nonpaired t tests were used. RESULTS: Of 382 screened infants, 34 developed type 1 ROP; 11 comprised the experimental group and 11 the control group. At baseline, there was a trend toward shorter temporal vascular extent in treatment compared with control groups (3667±547 vs 4262±937 pixels, 95% CI -1277, 88; P = .084) but no difference between groups at follow-up (P = .945). Vascular extension was significantly greater in the treatment than control (872±521 vs 253±151 pixels, 95% CI 262, 977; P = .003), showing catch-up growth. CONCLUSIONS: This clinical evidence supports laboratory-based studies that regulation of VEGF using an intravitreal anti-VEGF agent increases developmental angiogenesis into the peripheral avascular retina while inhibiting pathologic intravitreal angiogenesis in ROP.

A Literary Pediatric Retina Fellowship With Michael T. Trese, MD.

Michael T. Trese, MD (1946-2022), a vitreoretinal surgeon, made significant contributions to the field of retina. Although most known for his work in pediatric retina surgery, he was a pioneer in areas such as medical retina, translational research, and telemedicine. This article reviews his major contributions to spread his knowledge more widely to vitreoretinal trainees and specialists. We discuss six areas where Trese made a lasting impact: lens-sparing vitrectomy, familial exudative vitreoretinopathy, congenital X-linked retinoschisis, autologous plasmin enzyme, regenerative medicine, and telemedicine. [Ophthalmic Surg Lasers Imaging Retina 2023;54:701-712.].

Genome-wide association identifies novel ROP risk loci in a multi-ethnic cohort.

We conducted a genome-wide association study (GWAS) in a multiethnic cohort of 920 at-risk infants for retinopathy of prematurity (ROP), a major cause of childhood blindness, identifying 2 loci at genome-wide significance level (p<5×10-8) and 7 at suggestive significance (p<5×10-6) for ROP ≥ stage 3. The most significant locus, rs2058019, reached genome-wide significance within the full multiethnic cohort (p=4.96×10-9); Hispanic and Caucasian infants driving the association. The lead single nucleotide polymorphism (SNP) falls in an intronic region within the Glioma-associated oncogene family zinc finger 3 (GLI3) gene. Relevance for GLI3 and other top-associated genes to human ocular disease was substantiated through in-silico extension analyses, genetic risk score analysis and expression profiling in human donor eye tissues. Thus, we report the largest ROP GWAS to date, identifying a novel locus at GLI3 with relevance to retinal biology supporting genetic susceptibilities for ROP risk with possible variability by race and ethnicity.

Laser versus Anti-VEGF: A Paradigm Shift for Treatment-Warranted Retinopathy of Prematurity.

Retinopathy of prematurity (ROP), a leading cause of childhood blindness, has historically been associated with blindness from overgrowth of blood vessels from the retina into the vitreous that lead to complex retinal detachments. Our understanding of ROP has evolved with the survival of extremely low-birthweight infants and includes not only overgrowth of blood vessels, but also insufficient developmental retinal vascular growth in early phases of the disease. Our current treatments of ROP have focused on methods to improve perinatal and prenatal care, reduce premature birth, and prevent early phases of ROP. Nonetheless, addressing vasoproliferation in treatment-warranted eyes remains the mainstay of management. Two main treatment strategies co-exist today: laser treatment, which has been the standard of care since the 1990s, and anti-VEGF injections, which have been used since early reports in 2007 (Travassos et al. in Ophthalmic Surg Lasers Imaging, 38:233-237, https://doi.org/10.3928/15428877-20070501-09 , 2007, Shah et al. in Indian J Ophthalmol 55:75-76, https://doi.org/10.4103/0301-4738.29505 , 2007, Quiroz-Mercado et al. in Semin Ophthalmol 22:109-125, https://doi.org/10.1080/08820530701420082 , 2007).

The value of pre-symptomatic genetic risk assessment for age-related macular degeneration: the Moran AMD Genetic Testing Assessment (MAGENTA) study-a study protocol for a randomized controlled trial.

BACKGROUND: Age-related macular degeneration (AMD) is an irreversible blinding eye condition with complex genetic and environmental etiologies. Genetic testing for AMD for previously identified multiple-risk single nucleotide polymorphisms can help determine an individual's future susceptibility. However, such testing has been discouraged until evidence shows that providing such information to symptomatic or pre-symptomatic individuals will alter their disease course. Therefore, we designed this study to investigate whether knowledge of AMD risk could stimulate the adoption of a healthier lifestyle that could lower the incidence of AMD later in life. We hypothesize that pre-symptomatic individuals informed of a high genetic risk of AMD are more likely to make quantifiable, positive lifestyle changes relative to participants informed of lower genetic risk or randomized to deferred disclosure of genetic testing results. METHODS: The Moran AMD Genetic Testing Assessment (MAGENTA) study is a phase 2, single-center, prospective, double-masked, randomized controlled trial conducted at the John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. Participants are randomized by a 3:1 allocation ratio to immediate and deferred disclosure groups and followed for 12 months. Skin, ocular, and serum carotenoid status, as well as nutritional and social surveys, are assessed at study visits. Skin carotenoid assessment is by resonance Raman spectroscopy and reflectance spectroscopy, ocular carotenoids are measured with Heidelberg Spectralis autofluorescence imaging and fluorescence lifetime imaging ophthalmoscopy (FLIO), and serum carotenoids are quantified using high-performance liquid chromatography. The primary outcome evaluates changes in skin carotenoid status in response to genetic risk disclosure. The secondary outcomes examine changes in ocular and serum carotenoid status in response to genetic risk disclosure. Also, we will correlate AMD genetic risk with baseline ocular and systemic carotenoid status and FLIO. DISCUSSION: MAGENTA will provide much-needed evidence on whether pre-symptomatic testing for AMD risk can lead to quantifiable long-term changes in behavior and lifestyle associated with a lower incidence of AMD later in life. Findings from the MAGENTA trial will facilitate the design of a future larger, longer-term, multicenter phase 3 trial that could feature subgroup analysis, expanded measures of lifestyle modification, and potential active nutritional interventions. TRIAL REGISTRATION: ClinicalTrials.gov NCT05265624 . Registered on March 3, 2022.

7-Ketocholesterol Promotes Retinal Pigment Epithelium Senescence and Fibrosis of Choroidal Neovascularization via IQGAP1 Phosphorylation-Dependent Signaling.

Accumulation of 7-ketocholesterol (7KC) occurs in age-related macular degeneration (AMD) and was found previously to promote fibrosis, an untreatable cause of vision loss, partly through induction of endothelial-mesenchymal transition. To address the hypothesis that 7KC causes mesenchymal transition of retinal pigment epithelial cells (RPE), we exposed human primary RPE (hRPE) to 7KC or a control. 7KC-treated hRPE did not manifest increased mesenchymal markers, but instead maintained RPE-specific proteins and exhibited signs of senescence with increased serine phosphorylation of histone H3, serine/threonine phosphorylation of mammalian target of rapamycin (p-mTOR), p16 and p21, ß-galactosidase labeling, and reduced LaminB1, suggesting senescence. The cells also developed senescence-associated secretory phenotype (SASP) determined by increased IL-1ß, IL-6, and VEGF through mTOR-mediated NF-κB signaling, and reduced barrier integrity that was restored by the mTOR inhibitor, rapamycin. 7KC-induced p21, VEGF, and IL-1ß were inhibited by an inhibitor of protein kinase C. The kinase regulates IQGAP1 serine phosphorylation. Furthermore, after 7KC injection and laser-induced injury, mice with an IQGAP1 serine 1441-point mutation had significantly reduced fibrosis compared to littermate control mice. Our results provide evidence that age-related accumulation of 7KC in drusen mediates senescence and SASP in RPE, and IQGAP1 serine phosphorylation is important in causing fibrosis in AMD.

Ocular and developmental outcomes of a dosing study of bevacizumab for retinopathy of prematurity.

PURPOSE: To report 2-year ocular and developmental outcomes for infants receiving low doses of intravitreal bevacizumab for type 1 retinopathy of prematurity (ROP). METHODS: A total of 120 premature infants (mean birthweight, 687 g; mean gestational age, 24.8 weeks) with type 1 ROP were enrolled in a multicenter, phase 1 dose de-escalation study. One eye per infant received 0.25 mg, 0.125 mg, 0.063 mg, 0.031 mg, 0.016 mg, 0.008 mg, 0.004 mg, or 0.002 mg of intravitreal bevacizumab; fellow eyes when treated received one dosage level higher. At 2 years, 70 of 120 children (58%) underwent ocular examinations; 51 (43%) were assessed using the Bayley Scale of Infant and Toddler Development. RESULTS: Correlation coefficients for the association of total dosage of bevacizumab with Bayley subscales were -0.20 for cognitive (95% CI, -0.45 to 0.08), -0.15 for motor (95% CI, -0.41 to 0.14), and -0.19 for language (95% CI, -0.44 to 0.10). Fourteen children (21%) had myopia greater than -5.00 D in one or both eyes, 7 (10%) had optic nerve atrophy and/or cupping, 20 (29%) had strabismus, 8 (11%) had manifest nystagmus, and 9 (13%) had amblyopia. CONCLUSIONS: In this study cohort, there was no statistically significant correlation between dosage of bevacizumab and Bayley scores at 2 years. However, the sample size was small and the retention rate relatively low, limiting our conclusions. Rates of high myopia and ocular abnormalities do not differ from those reported after larger bevacizumab doses.

COMBINED HAMARTOMA OF THE RETINA AND RETINAL PIGMENT EPITHELIUM AT PEDIATRIC AGE: Surgical Versus Conservative Approach.

PURPOSE: To report outcomes of pediatric patients with combined hamartoma of the retina and the retina pigment epithelium followed up conservatively or after pars plana vitrectomy. METHODS: This retrospective multicenter study included 62 eyes of 59 pediatric patients with combined hamartoma of the retina and the retina pigment epithelium from 13 different international centers with an average age of 7.7 ± 4.7 (0.3-17) years at the time of the diagnosis and having undergone pars plana vitrectomy or followed conservatively. At baseline and each visit, visual acuity values, optical coherence tomography for features and central foveal thickness, and tumor location were noted. Lesions were called as Zone 1, if it involves the macular and peripapillary areas, and the others were called as Zone 2 lesions. RESULTS: Twenty-one eyes of 20 patients in the intervention group and 41 eyes of 39 patients in the conservative group were followed for a mean of 36.2 ± 40.4 (6-182) months. Best-corrected visual acuity improved in 11 (68.8%) of 16 eyes in the intervention group and 4 (12.9%) of 31 eyes in the conservative group ( P < 0.001). The mean central foveal thickness decreased from 602.0 ± 164.9 µ m to 451.2 ± 184.3 µ m in the intervention group, while it increased from 709.5 ± 344.2 µ m to 791.0 ± 452.1 µ m in Zone 1 eyes of the conservative group. Posterior location of tumor, irregular configuration of the foveal contour and ellipsoid Zone defect in optical coherence tomography, subretinal exudate and prominent vascular tortuosity were associated with poor visual acuity. CONCLUSION: Vitreoretinal surgery is safe and effective in improving vision and reducing retinal distortion in Zone 1 combined hamartoma of the retina and the retina pigment epithelium in children.

Retinopathy of prematurity.

Retinopathy of prematurity (ROP) is a devastating neurovascular disease of the retina in newborn infants that can lead to vision deficits or even blindness. In this concise review we discuss our current knowledge about diagnosis, etiology, pathogenesis, intervention, and outcomes of the disease. Major advancements have been made both in categorizing the disease in the new International Classification of Retinopathy of Prematurity, Third Edition classification and in treating severe ROP with anti-vascular endothelial growth factor (VEGF) agents. New development always creates new questions and opens up new areas of research. We will discuss in this review both the benefits and downsides of the new anti-VEGF treatment approaches in ROP, especially in light of our improved understanding of the underlying ROP pathophysiology. We also offer pointers to areas where more research is needed. WHAT THIS PAPER ADDS: Concise update on all aspects of retinopathy of prematurity (ROP), including advances in understanding and treatment. Benefits and risks of the new treatment method of anti-vascular endothelial growth factor injections in ROP are discussed. New research areas that deserve attention in the coming years are identified.

Multimodal Retinal Imaging Findings in Two Cousins With VCAN-Related Vitreoretinopathy or Wagner Disease.

Wagner disease is a rare, nonsyndromic vitreoretinopathy caused by autosomal dominant variants in the versican (VCAN) gene. It is associated with abnormalities of the vitreoretinal interface that can lead to peripheral traction and retinal detachments, which also occur in other vitreoretinopathies such as X-linked retinoschisis (XLRS), familial exudative vitreoretinopathy (FEVR) and Stickler syndrome. There is variability in the clinical phenotype in Wagner disease potentially due to variants in VCAN gene variants. In this article, we report a family harboring the VCAN c.9265+1G>C variant and describe the clinical and retinal findings in two members. [Ophthalmic Surg Lasers Imaging Retina 2022;53:639-643.].

Vitrectomy-Assisted Excision in the Treatment of Juxtapapillary Retinal Capillary Hemangioma.

Juxtapapillary retinal capillary hemangiomas are sight-threatening hamartomas located on or adjacent to the optic nerve. Nonsurgical approaches including laser photocoagulation and cryotherapy have been shown to be effective to reduce exudation in peripheral hemangiomas. However, in juxtapapillary hemangiomas, the functional outcomes are limited due to associated potential damage of the retinal nerve fiber layer. We present an 18-year-old female patient with von Hippel-Lindau (VHL) disease who presented with a juxtapapillary retinal capillary hemangioma associated with a tractional epiretinal membrane (ERM) and secondary macular hole. After vitrectomy-assisted excision of the lesion and inner limiting membrane (ILM) peeling around the macular hole, visual acuity and macular anatomy were recovered at 10 months of follow-up. [Ophthalmic Surg Lasers Imaging Retina 2022;53:570-573.].

RNA-Seq Provides Insights into VEGF-Induced Signaling in Human Retinal Microvascular Endothelial Cells: Implications in Retinopathy of Prematurity.

The pathophysiology of retinopathy of prematurity (ROP) is postulated to first involve delayed intraretinal vascularization, followed by intravitreal neovascularization (IVNV). Although intravitreal agents that reduce the bioactivity of vascular endothelial growth factor (VEGF) are used to treat IVNV, concerns exist regarding their effects on intraretinal vascularization. In an experimental ROP model, VEGF receptor 2 (VEGFR2) knockdown in retinal endothelial cells reduced IVNV and promoted intraretinal vascularization, whereas knockdown of a downstream effector, signal transducer and activator of transcription 3 (STAT3) in retinal endothelial cells only reduced IVNV. In this study, we tested the hypothesis that the different pathways involved in VEGF-triggered VEGFR2 signaling and VEGF-triggered STAT3 signaling in retinal endothelial cells would allow us to delineate signaling pathways involved in IVNV from those involved in intraretinal vascularization in ROP. To address our hypothesis, we used RNA-sequencing and pathway enrichment analysis to determine changes in the transcriptome of cultured human retinal microvascular endothelial cells (HRMECs). Of the enriched pathways, inactivation of oncostatin M signaling was predicted by either KDR or STAT3 knockdown in the presence of VEGF. Activation of kinetochore metaphase signaling was predicted by KDR knockdown, whereas inactivation was predicted by STAT3 knockdown in the presence of VEGF. Inactivation of signaling by the Rho family of GTPases was predicted by KDR knockdown, but activation was predicted by STAT3 knockdown in the presence of VEGF. Taken together, our data identified unique signaling pathway differences between VEGF-triggered VEGFR2 and VEGF-triggered STAT3 in HRMECs that might have implications in ROP.

Plasma Levels of Bevacizumab and Vascular Endothelial Growth Factor After Low-Dose Bevacizumab Treatment for Retinopathy of Prematurity in Infants.

Importance: Intravitreal bevacizumab effectively treats severe retinopathy of prematurity (ROP), but it enters the bloodstream and may reduce serum vascular endothelial growth factor (VEGF), potentially causing detrimental effects on developing organs in the premature infant. Objective: To evaluate the association of intravitreal bevacizumab with plasma bevacizumab and VEGF concentrations at 2 and 4 weeks after predefined, de-escalating doses of intravitreal bevacizumab were administered to infants with severe ROP. Design, Setting, and Participants: This phase 1 dose de-escalation case series study was conducted at 10 US hospitals of ophthalmology institutions from May 21, 2015, to May 7, 2019. Blood samples were collected 2 and 4 weeks after intravitreal bevacizumab injection. Participants included 83 premature infants with type 1 ROP in 1 or both eyes and no previous ROP treatment. Data were analyzed from April 2017 to August 2021. Interventions: Study eyes received a single bevacizumab injection of 0.250 mg, 0.125 mg, 0.063 mg, 0.031 mg, 0.016 mg, 0.008 mg, 0.004 mg, or 0.002 mg. When the fellow eye required treatment, one dose higher was administered. Total dose administered at baseline was defined as the sum of doses given to each eye within 3 days of initial study-eye injection. Main Outcomes and Measures: Plasma bevacizumab concentration at 2 and 4 weeks after injection and the percentage change in plasma VEGF concentrations from pretreatment levels. Results: A total of 83 infants (mean [SD] age, 25 [2] weeks; 48 boys [58%]) were included in this study. Higher doses of bevacizumab administered at baseline were associated with higher plasma bevacizumab concentrations at 2 weeks (ρ, 0.53; 95% CI, 0.31-0.70) and 4 weeks (ρ, 0.44; 95% CI, 0.18-0.64). Plasma VEGF concentrations decreased by 50% or more from pretreatment levels in 40 of 66 infants (61%) at 2 weeks and 31 of 61 infants (51%) at 4 weeks, but no association was observed between the total dose of bevacizumab administered at baseline and percentage change in plasma VEGF concentrations 2 weeks (ρ, -0.04; 95% CI, -0.28 to 0.20) or 4 weeks (ρ, -0.17; 95% CI, -0.41 to 0.08) after injection. Conclusions and Relevance: Results of this phase 1 dose de-escalation case series study revealed that bevacizumab doses as low as 0.002 mg were associated with reduced plasma VEGF levels for most infants at 2 and 4 weeks after intravitreal administration; however, no association was observed between total bevacizumab dose administered and reductions in plasma VEGF levels from preinjection to 2 weeks or 4 weeks. Additional studies are needed to evaluate the long-term effects of low-dose bevacizumab on neurodevelopment and retinal structure.

Planned Preterm Delivery and Treatment of Severe Infantile FEVR With Osteoporosis-Pseudoglioma Syndrome.

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary vitreoretinopathy resulting from mutations in the wnt signaling pathway leading to abnormalities in fetal retinal vasculogenesis, angiogenesis, and retinal vascular maintenance. Severe FEVR may result in congenital retinal detachment resembling Norrie disease. The authors report the first case of planned preterm delivery and treatment of a patient with severe FEVR from biallelic LRP5 mutations whose siblings had congenital tractional retinal detachments with light perception vision outcomes after conventional care. Early intervention allowed laser ablation of avascular retina and functional visual outcome despite a successfully repaired unilateral tractional retinal detachment. [Ophthalmic Surg Lasers Imaging Retina. 2022;53(4):228-232.].

Active Rap1-mediated inhibition of choroidal neovascularization requires interactions with IQGAP1 in choroidal endothelial cells.

Neovascular age-related macular degeneration (nAMD) is a leading cause of blindness. The pathophysiology involves activation of choroidal endothelial cells (CECs) to transmigrate the retinal pigment epithelial (RPE) monolayer and form choroidal neovascularization (CNV) in the neural retina. The multidomain GTPase binding protein, IQGAP1, binds active Rac1 and sustains activation of CECs, thereby enabling migration associated with vision-threatening CNV. IQGAP1 also binds the GTPase, Rap1, which when activated reduces Rac1 activation in CECs and CNV. In this study, we tested the hypothesis that active Rap1 binding to IQGAP1 is necessary and sufficient to reduce Rac1 activation in CECs, and CNV. We found that pharmacologic activation of Rap1 or adenoviral transduction of constitutively active Rap1a reduced VEGF-mediated Rac1 activation, migration, and tube formation in CECs. Following pharmacologic activation of Rap1, VEGF-mediated Rac1 activation was reduced in CECs transfected with an IQGAP1 construct that increased active Rap1-IQGAP1 binding but not in CECs transfected with an IQGAP1 construct lacking the Rap1 binding domain. Specific knockout of IQGAP1 in endothelial cells reduced laser-induced CNV and Rac1 activation in CNV lesions, but pharmacologic activation of Rap1 did not further reduce CNV compared to littermate controls. Taken together, our findings provide evidence that active Rap1 binding to the IQ domain of IQGAP1 is sufficient to interfere with active Rac1-mediated CEC activation and CNV formation.

IQGAP1 causes choroidal neovascularization by sustaining VEGFR2-mediated Rac1 activation.

Loss of visual acuity in neovascular age-related macular degeneration (nAMD) occurs when factors activate choroidal endothelial cells (CECs) to transmigrate the retinal pigment epithelium into the sensory retina and develop into choroidal neovascularization (CNV). Active Rac1 (Rac1GTP) is required for CEC migration and is induced by different AMD-related stresses, including vascular endothelial growth factor (VEGF). Besides its role in pathologic events, Rac1 also plays a role in physiologic functions. Therefore, we were interested in a method to inhibit pathologic activation of Rac1. We addressed the hypothesis that IQGAP1, a scaffold protein with a Rac1 binding domain, regulates pathologic Rac1GTP in CEC migration and CNV. Compared to littermate Iqgap1+/+, Iqgap1-/- mice had reduced volumes of laser-induced CNV and decreased Rac1GTP and phosphorylated VEGFR2 (p-VEGFR2) within lectin-stained CNV. Knockdown of IQGAP1 in CECs significantly reduced VEGF-induced Rac1GTP, mediated through p-VEGFR2, which was necessary for CEC migration. Moreover, sustained activation of Rac1GTP induced by VEGF was eliminated when CECs were transfected with an IQGAP1 construct that is unable to bind Rac1. IQGAP1-mediated Src activation was involved in initiating Rac1 activation, CEC migration, and tube formation. Our findings indicate that CEC IQGAP1 interacts with VEGFR2 to mediate Src activation and subsequent Rac1 activation and CEC migration. In addition, IQGAP1 binding to Rac1GTP results in sustained activation of Rac1, leading to CEC migration toward VEGF. Our study supports a role of IQGAP1 and the interaction between IQGAP1 and Rac1GTP to restore CECs quiescence and, therefore, prevent vision-threatening CNV in nAMD.

Signaling Through the Erythropoietin Receptor Affects Angiogenesis in Retinovascular Disease.

Purpose: Exogenous erythropoietin (EPO) is being considered for tissue protection and angiogenesis in retinal vascular diseases. However, studies are limited by insufficient tools to address signaling effects through the EPO receptor (EPOR). We used a humanized mouse model of hypoactive EPOR signaling to test the hypothesis that EPOR signaling supports angiogenesis in retinovascular diseases. Methods: Humanized Knockin EPOR mice (hWtEPOR) with hypoactive EPOR signaling were compared to littermate wild-type mice (WT). Postnatal day (p)7 mice of each genotype were exposed to 75% oxygen for five days, followed by 21% oxygen in the oxygen-induced retinopathy model (OIR) and compared to room-air (RA)-raised pups. At time points after OIR, pups were sacrificed, and flat-mounted, lectin-stained retinas were analyzed for central avascular area or intravitreal neovascular area (IVNV). Flash-frozen retinas were analyzed for angiogenic protein (Epo, VEGF, p-Stat3) and gene (Vegfa, Kdr, Epo, Hif1α, Hif2α) expression levels. Results: In OIR, hWtEPOR mice had increased AVA compared with WT at p8, p12, and p17, but there was no difference in IVNV between hWtEPOR and WT mice at p17. Although VEGF and p-STAT3 proteins were increased in WT at p17 OIR, there were no differences in retinal angiogenic factor expression levels between hWtEPOR and WT OIR at p17 despite similar areas of IVNV. Conclusions: Our data support the hypothesis that EPOR signaling was associated with regrowth of vascularization following oxygen-induced capillary dropout and played a role in intravitreal angiogenesis. Additional study of EPOR signaling regulation on other angiogenic factor pathways may be considered.

Retinopathy of Prematurity: Evolving Treatment With Anti-Vascular Endothelial Growth Factor.

PURPOSE: To discuss the evolution in retinopathy of prematurity since its first description as retrolental fibroplasia in the United States, including the changes in the understanding of pathophysiology; methods of diagnosis; destructive, anti-vascular endothelial growth factor (anti-VEGF), and supportive treatments; and differences in retinopathy of prematurity manifestations worldwide. The overall goal is to clarify retinopathy of prematurity currently and formulate questions to optimize future care. STUDY DESIGN: Literature review and synthesis. METHODS: Critical review and consideration of the literature with inclusion of historical articles and those regarding pathophysiologic risk factors, retinopathy of prematurity worldwide, basic and clinical science particularly regarding anti-VEGF mechanisms and agents tested in clinical trials. RESULTS: Retinopathy of prematurity has evolved from affecting infants approximately 2 months premature to affecting extremely premature infants. Worldwide, retinopathy of prematurity differs and, in emerging countries, has features similar to that experienced in the United States when retinopathy of prematurity first manifested. Treatments have evolved from destruction of the peripheral avascular retina to inhibit angiogenic stimuli to anti-VEGF agents, which inhibit pathologic angiogenesis but also extend normal intraretinal angiogenesis by ordering the development of intraretinal vessels. Clinical trial evidence is accruing with the goal to develop less destructive treatments to optimize vision and that are protective to the retina and infant. CONCLUSIONS: Goals for retinopathy of prematurity are to optimize prenatal and perinatal care, improve diagnostic acumen worldwide and refine treatment strategies, including with anti-VEGF agents, to inhibit intravitreal angiogenesis and facilitate vascularization of the previously avascular retina, which include supporting neural and vascular development of the premature infant and retina.