Understanding retinopathy of prematurity: update on pathogenesis

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.

A Narrative Review on Managing Retinopathy of Prematurity: Insights Into Pathogenesis, Screening, and Treatment Strategies

Retinopathy of prematurity (ROP) is a rare proliferative ocular condition that can happen in premature babies (born preterm <36 weeks) or who weigh <1.5 kg at birth (low birth weight babies). ROP is a major cause of childhood blindness. It is a premature disease since retina vascularization is completed only by 40 weeks of life. The survivability for preterm infants has increased owing to recent improvements in neonatal care during the past decade. As a result, the prevalence of ROP has risen concurrently. The abnormal development of blood vessels in the retina is the cause of this illness. It occurs in two phases, phases 1 and 2. Most preterm infants weighing <1.5 kg need supplemental oxygen for respiratory support at birth. This leads to the initiation of phase 1 (vasoconstrictive phase). Phase 1 is characterized by loss of maternal-fetal connection and hyperoxia due to supplemental oxygen therapy. Oxygen's vasoconstrictive and obliterative action is primarily observed in developing retinal vessels. The inhibition of vascular endothelial growth factor follows from this. Phase 2 (vasoproliferative phase) shows the dilatation and tortuosity of the bigger existing vessels together with neovascularization and proliferation of new vessels into the vitreous when the baby is shifted from respiratory support to room air. Now, the retina gets hypoxic, where the retina becomes more metabolically active but is yet minimally vascularized, leading to VEGF-induced vasoproliferation, which might result in retinal detachment. Patients with ROP face the danger of loss of vision. If correct and quick treatment is not provided, they might land into permanent blindness. Yet, ROP remains one of the most preventable causes of childhood blindness worldwide. Blindness caused by ROP can only be avoided if screening programs are readily available, pertinent, and appropriate. The initial stage in the therapy of ROP is the screening of premature neonates. Timely screening and management for ROP is important to avoid this irreversible loss of vision. The treatment is based on the severity of the disease. Management may include pharmacological interventions like intravitreal and anti-vascular endothelial growth factor and non-pharmacological interventions like laser surgery, vitrectomy, and scleral buckling. We conducted a thorough literature search of studies on pathogenesis, risk factors, classification, and various treatment options for retinopathy of prematurity in infants, using a mixture of pertinent keywords. Only those studies published in peer-reviewed journals between 2010 and 2023 and written in English were included. Duplicate studies, unavailable in full-text for free, or studies unrelated to our subject matter were excluded. After thoroughly evaluating the selected studies, the results were synthesized and presented narratively. This article sheds light on the pathogenesis of ROP, particularly its relation to oxygen use, screening, and potential therapeutic management of ROP. Today advances in screening techniques have improved the outcomes for infants with ROP. Still, ongoing research is needed to optimize management strategies and reduce the burden of this condition.

Identification of immune-related genes in diagnosing retinopathy of prematurity with sepsis through bioinformatics analysis and machine learning

Background: There is increasing evidence indicating that immune system dysregulation plays a pivotal role in the pathogenesis of retinopathy of prematurity (ROP) and sepsis. This study aims to identify key diagnostic candidate genes in ROP with sepsis. Methods: We obtained publicly available data on ROP and sepsis from the gene expression omnibus database. Differential analysis and weighted gene correlation network analysis (WGCNA) were performed to identify differentially expressed genes (DEGs) and key module genes. Subsequently, we conducted functional enrichment analysis to gain insights into the biological functions and pathways. To identify immune-related pathogenic genes and potential mechanisms, we employed several machine learning algorithms, including Support Vector Machine Recursive Feature Elimination (SVM-RFE), Least Absolute Shrinkage and Selection Operator (LASSO), and Random Forest (RF). We evaluated the diagnostic performance using nomogram and Receiver Operating Characteristic (ROC) curves. Furthermore, we used CIBERSORT to investigate immune cell dysregulation in sepsis and performed cMAP analysis to identify potential therapeutic drugs. Results: The sepsis dataset comprised 352 DEGs, while the ROP dataset had 307 DEGs and 420 module genes. The intersection between DEGs for sepsis and module genes for ROP consisted of 34 genes, primarily enriched in immune-related pathways. After conducting PPI network analysis and employing machine learning algorithms, we pinpointed five candidate hub genes. Subsequent evaluation using nomograms and ROC curves underscored their robust diagnostic potential. Immune cell infiltration analysis revealed immune cell dysregulation. Finally, through cMAP analysis, we identified some small molecule compounds that have the potential for sepsis treatment. Conclusion: Five immune-associated candidate hub genes (CLEC5A, KLRB1, LCN2, MCEMP1, and MMP9) were recognized, and the nomogram for the diagnosis of ROP with sepsis was developed.

Ocular Vascular Diseases: From Retinal Immune Privilege to Inflammation

The eye is an immune privileged tissue that insulates the visual system from local and systemic immune provocation to preserve homeostatic functions of highly specialized retinal neural cells. If immune privilege is breached, immune stimuli will invade the eye and subsequently trigger acute inflammatory responses. Local resident microglia become active and release numerous immunological factors to protect the integrity of retinal neural cells. Although acute inflammatory responses are necessary to control and eradicate insults to the eye, chronic inflammation can cause retinal tissue damage and cell dysfunction, leading to ocular disease and vision loss. In this review, we summarized features of immune privilege in the retina and the key inflammatory responses, factors, and intracellular pathways activated when retinal immune privilege fails, as well as a highlight of the recent clinical and research advances in ocular immunity and ocular vascular diseases including retinopathy of prematurity, age-related macular degeneration, and diabetic retinopathy.

Potential Role of Bilirubin in Preventing Retinopathy of Prematurity

BACKGROUND

One of the most common problems in preterm neonates is retinopathy of prematurity (ROP). It has been shown antioxidants may be effective in preventing the development and progression of ROP. Considering the antioxidant properties of bilirubin, we decided to investigate the bilirubin level in neonates with ROP and compare it with healthy neonates.

METHODS

This case-control study was performed on VLBW neonates admitted to the NICU of Ghaem Hospital in Mashhad between 2014 and 2020 for a Jaundice evaluation. Complete neonate's characteristics, maternal history and laboratory results were collected in a questionnaire. Then the neonates were examined for ROP by a fellowship of the retina of an ophthalmologist at 32 weeks or four weeks after birth. The highest bilirubin levels during their hospitalization were also recorded.

RESULTS

Of 427 neonates examined, 121 (37.7%) had a normal eye examination, and 266 (62.3%) had ROP. The mean weight, gestational age and bilirubin were 1455.8 ± 431.4 grams, 31.6 ± 2.3 weeks and 8.8 ± 2.4 mg/dl, respectively. There was a significant difference between controls and neonates with ROP with regard to birth weight, duration of intermittent positive pressure ventilation (IPPV), duration of oxygen therapy, first and fifth minute Apgar scores, the maximum level of bilirubin and gestational age (P < 0.05). It was observed that the maximum level of bilirubin was lower in neonates with higher stages of ROP.

CONCLUSION

According to the results of this study, higher levels of bilirubin in neonates may be a protective factor against ROP. Moreover, increased levels of bilirubin are associated with reduced severity of ROP. Therefore, prophylaxis phototherapy in premature infants may need to be reconsidered.

The Determinative Role of Cytokines in Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is a neonatal disease corresponding to vision impairment and blindness. Utilizing the pathogenesis of ROP and the risk factors affecting its progression can help prevent and reduce its incidence and lead to the emergence and development of new treatment strategies. Factors influencing retinopathy include growth and inflammatory factors that play an essential role in the pathogenesis of the ROP. This review summarizes the most critical factors in the pathogenesis of ROP.

The Serum Levels of Asymmetric Dimethylarginine, Vascular Endothelial Growth Factor, and Insulin-Like Growth Factor-1 in Preterms with Retinopathy of Prematurity

Objective:To determine the serum levels of asymmetric dimethylarginine (ADMA), vascular endothelial growth factor (VEGF), and insulin-like growth factor-1 (IGF-1) in preterms with retinopathy of prematurity (ROP). Materials and Methods: We included 37 preterm infants. The first blood samples were obtained within the first 5 days of life and repeated at the time of the first ophthalmologic examination for ROP. The levels of ADMA, IGF-1, and VEGF were measured in all samples. Results: ROP was detected in 12 of the subjects (32.4%). We categorized the subjects as non-ROP (Group 1; n = 25), untreated ROP (Group 2; n = 7), and treated ROP (Group 3; n = 5) according to the eye findings. There were no significant differences among the groups for serum levels of ADMA, VEGF, and IGF-1 at the first sampling. Conclusion: We did not find any differences in terms of serum ADMA, IGF-1, and VEGF levels in preterm infants with or without ROP.

APJ/apelin: a promising target for the treatment of retinopathy of prematurity

Retinopathy of prematurity is a noticeable retinal abnormality causing common blindness in children. An uncontrolled retinal vasculature in retinopathy of prematurity inflicts vision loss in numerous children despite the accessibility to a wide range of clinical treatments prescribed for retinopathy of prematurity. Apelin/APJ [class A (rhodopsin-like) G-protein-coupled receptor] signaling regulates retinopathy of prematurity augmented with uncontrolled angiogenesis. Antagonists targeting pathological apelin/APJ-signaling-induced angiogenesis could be effective in attenuating retinopathy of prematurity. The therapeutic proficiency of antagonists in diverse modalities: peptides, bioactive molecules and antibodies, targeting apelin peptides or the APJ receptor is discussed in this review. We hypothesize the antagonists could effectively attenuate the retinal vasculature triggered by apelin/APJ signaling activation governing vision impairment in young children.

Neurodevelopmental Outcomes Associated With Intravitreal Bevacizumab Injections for Retinopathy of Prematurity

BACKGROUND

Retinopathy of prematurity (ROP) is a common disorder among premature infants associated with significant morbidity. The current standard of care includes laser ablation therapy when needed. While intravitreal bevacizumab (IVB) injections have emerged as a new therapy for ROP, so have concerns about the systemic effects of the bevacizumab (Avastin), specifically on neurodevelopmental outcomes.

PURPOSE

To review the current literature on the impact of IVB on neurodevelopmental outcomes in neonates with ROP to inform nurses' knowledge and practice.

METHODS

A literature search was performed in the PubMed, CINAHL, and Embase databases. Eleven primary studies examining neurodevelopmental outcomes related to IVB were identified and reviewed.

RESULTS

Limitations of current studies, including small sample sizes, retrospective analysis subject to selection bias, and confounding factors such as sedation/anesthesia exposure, prevent robust conclusions from being drawn. However, there is not currently any clear evidence of negative neurodevelopmental impacts associated with IVB despite a sound theoretical basis for concern.

IMPLICATIONS FOR PRACTICE

Nurses should include all known and potential risks and benefits when counseling families and developing individualized plans of care for their neonatal patients with ROP.

IMPLICATIONS FOR RESEARCH

Well-designed, prospective studies examining neurodevelopmental outcomes at later time points are needed to conclusively support or disprove results of IVB therapy for ROP in the context of potential adverse effects.

Assessment of Role of Platelet Indices in the Occurrence of Retinopathy of Prematurity

PURPOSE

Platelets have a major role in the regulation of angiogenesis. Platelets have proangiogenic factors like vascular endothelial growth factor, which causes neovascularization of immature retina. However, there is no conclusive evidence to show that platelet indices have a role in retinopathy of prematurity (ROP). This study is aimed at assessing the role of platelet indices in the occurrence and need for treatment of ROP.

METHODS

This prospective cohort study included the screening of preterm babies (<37 weeks of gestation with birth weight <2000 g). The samples of platelet indices (mean platelet volume [MPV], platelet count [PLT], plateletcrit [PCT], and platelet distribution width [PDW]) collected within 1^st week of life were obtained from the electronic medical records and correlated to ROP status. Statistical analysis was done using SPSS version 22, and the Chi-square test and odds ratio were used for analysis.

RESULTS

A total of 300 preterm babies were screened, of whom, 55 (18.3%) babies had ROP changes. The association of the presence of ROP changes and platelet indices was not statistically significant (P value being MPV [0.22], PLT [0.58], PCT [0.98], and PDW [0.17]). Similarly, the requirement of treatment for ROP (Type I ROP) could not be correlated with abnormal platelet indices (odds ratio at 95% confidence interval - MPV [6 (0.44-81.44)], PLT [1.7 (0.25-11.37)], PCT [3 (0.44-20.90)], and PDW [0.32 (0.33-3.05)]).

CONCLUSION

Abnormal platelet indices did not show any significant risk with the occurrence or need for treatment of ROP.

The Role of Thrombocyte Parameters in Retinopathy of Prematurity Development

PURPOSE

To investigate the role of thrombocyte parameters in retinopathy of prematurity (ROP) development.

MATERIALS AND METHODS

This retrospective study included 120 preterm infants in total. Group 1 was formed by infants who developed type-1 ROP and received treatment. Group 2 was formed by infants who developed ROP and were not treated for ROP. Infants who did not develop ROP and whose retinal vascularization was completed in their follow-up formed Group 3. Gestational age, birth weight, and genders of groups were recorded. Platelet (PLT) count, mean platelet volume (MPV), and platelet distribution width (PDW) values were obtained from complete blood count. Platelet mass index (PMI) was calculated by multiplying the PLT count by MPV value. Thrombocytopenia was defined as PLT count <150 × 1000/μL. All parameters were compared between the groups.

RESULTS

There were 40 preterm infants in each group. The mean PLT count was 272.43 ± 122.67 in Group 1, 333.32 ± 133.06 in Group 2, and 310.03 ± 119.41 in Group 3. The difference in PLT count between the groups was not significant (p=0.094). Thrombocytopenia was observed in 25% of Group 1, 10% of Group 2, and 10% of Group 3 (p=0.095). No statistically significant difference was found in terms of MPV, PDW, and PMI values between the groups (p=0.102, p=0.097, and p=0.298, respectively).

CONCLUSIONS

Although PLT count was lower and thrombocytopenia rate was higher in the type-1 ROP group, the differences were not found to be significant. Further prospective studies are required to evaluate the role of thrombocytes in ROP pathogenesis.

eNOS controls angiogenic sprouting and retinal neovascularization through the regulation of endothelial cell polarity

The roles of nitric oxide (NO) and endothelial NO synthase (eNOS) in the regulation of angiogenesis are well documented. However, the involvement of eNOS in the sprouting of endothelial tip-cells at the vascular front during sprouting angiogenesis remains poorly defined. In this study, we show that downregulation of eNOS markedly inhibits VEGF-stimulated migration of endothelial cells but increases their polarization, as evidenced by the reorientation of the Golgi in migrating monolayers and by the fewer filopodia on tip cells at ends of sprouts in endothelial cell spheroids. The effect of eNOS inhibition on EC polarization was prevented in Par3-depleted cells. Importantly, downregulation of eNOS increased the expression of polarity genes, such as PARD3B, PARD6A, PARD6B, PKCΖ, TJP3, and CRB1 in endothelial cells. In retinas of eNOS knockout mice, vascular development is retarded with decreased vessel density and vascular branching. Furthermore, tip cells at the extremities of the vascular front have a marked reduction in the number of filopodia per cell and are more oriented. In a model of oxygen-induced retinopathy (OIR), eNOS deficient mice are protected during the initial vaso-obliterative phase, have reduced pathological neovascularization, and retinal endothelial tip cells have fewer filopodia. Single-cell RNA sequencing of endothelial cells from OIR retinas revealed enrichment of genes related to cell polarity in the endothelial tip-cell subtype of eNOS deficient mice. These results indicate that inhibition of eNOS alters the polarity program of endothelial cells, which increases cell polarization, regulates sprouting angiogenesis and normalizes pathological neovascularization during retinopathy.

An imbalance in autophagy contributes to retinal damage in a rat model of oxygen-induced retinopathy

In retinopathy of prematurity (ROP), the abnormal retinal neovascularization is often accompanied by retinal neuronal dysfunction. Here, a rat model of oxygen‐induced retinopathy (OIR), which mimics the ROP disease, was used to investigate changes in the expression of key mediators of autophagy and markers of cell death in the rat retina. In addition, rats were treated from birth to postnatal day 14 and 18 with 3‐methyladenine (3‐MA), an inhibitor of autophagy. Immunoblot and immunofluorescence analysis demonstrated that autophagic mechanisms are dysregulated in the retina of OIR rats and indicated a possible correlation between autophagy and necroptosis, but not apoptosis. We found that 3‐MA acts predominantly by reducing autophagic and necroptotic markers in the OIR retinas, having no effects on apoptotic markers. However, 3‐MA does not ameliorate retinal function, which results compromised in this model. Taken together, these results revealed the crucial role of autophagy in retinal cells of OIR rats. Thus, inhibiting autophagy may be viewed as a putative strategy to counteract ROP.

Neonatal Platelet Transfusions: Starting Again

Preterm neonates with severe thrombocytopenia are frequently prescribed prophylactic platelet transfusions despite no evidence of benefit. Neonatal platelet transfusion practice varies, both nationally and internationally. Volumes and rates of transfusion in neonatology are based on historic precedent and lack an evidence base. The etiology of harm from platelet transfusions is poorly understood. Neonates are expected to be the longest surviving recipients of blood produce transfusions, and so avoiding transfusion associated harm is critical in this cohort. This article reviews the evidence for and against platelet transfusion in the neonate and identifies areas of future potential neonatal platelet transfusion research.

Noninvasive ventilation for respiratory distress syndrome is a potential risk factor for retinopathy of prematurity : Single Slovenian tertiary center study

Retinopathy of prematurity (nROP) among extremely low gestational age newborns (ELGAN) in Slovenia has increased in recent years. At the same time mortality has further decreased and less invasive approaches for treatment of respiratory distress syndrome have been established. With the aim to study the possible association between the incidence of ROP and the duration of noninvasive ventilation, this retrospective study comprised ELGANs born during the first period (2010/2011), when invasive respiratory support was the prevalent method and in the second period (2015/2016), when noninvasive respiratory support was adopted. The results showed that the duration of noninvasive ventilation is a potential risk factor for ROP. Controlling for known risk factors for ROP and then adjusting for gestational age, number of transfusions and fraction of inspired oxygen (FiO₂), the odds of ROP were 1.22 times greater (95% confidence interval, CI 1.01-1.48) with every additional week of noninvasive ventilation (p = 0.03).

Complete blood count parameters to predict retinopathy of prematurity: when to evaluate and what do they tell us?

PURPOSE

To evaluate the relationship of novel inflammatory markers neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) with retinopathy of prematurity (ROP) development and requirement for laser photocoagulation (LP) treatment.

METHODS

The charts of infants screened for ROP were reviewed retrospectively, and 120 newborns who had complete blood count (CBC) data in the first 24 hours after delivery (early period) and between 35 and 37th gestational weeks (late period) were included. Study population consisted of 34 infants who required LP for ROP treatment, 52 newborns with ROP that regressed without treatment, and 34 controls who did not developed any ROP stages. Demographics, etiological factors and CBC data including NLR and PLR values were noted. Risk factors for ROP development and treatment requirement were investigated using logistic regression analyses.

RESULTS

Significantly lower NLR was found in ROP cases compared to non-ROP group during late period (p = 0.003), while there was no difference in NLR during early period (p = 0.298). No significant difference was observed in PLR during both early and late periods (p = 0.230 and p = 0.349, respectively). Multivariate analysis revealed daily weight gain as major risk factor for ROP development (p = 0.001; OR: 0.870, 95% CI: 0.799-0.947), and hyperbilirubinemia as an independent risk factor for LP requirement (p = 0.045; OR: 0.204, 95% CI: 0.043-0.966).

CONCLUSION

NLR or PLR does not appear to be predictive risk factors for treatment requirement in cases with ROP. CBC values during first 24 h of life may be misleading; therefore, a late period CBC is recommended to evaluate prognostic factors for ROP development.

Progressive retinal vessel malformation in a premature infant with Sturge-Weber syndrome: a case report and a literature review of ocular manifestations in Sturge-Weber syndrome

BACKGROUND

Sturge-Weber syndrome is a disorder marked by a distinctive facial capillary malformation, neurological abnormalities, and ocular abnormalities such as glaucoma and choroidal hemangioma.

CASE PRESENTATION

We report a case of progressively formed retinal vessel malformation in a premature male infant with Sturge-Weber syndrome and retinopathy of prematurity, after treatment with intravitreal anti-vascular endothelial growth factor (VEGF). The baby was born at 30 weeks gestation with a nevus flammeus involving his left eyelids and maxillary area. On postmenstrual age week 39, he received intravitreal anti-VEGF. Diffuse choroidal hemangioma became evident at 40 weeks, with the classic "tomato catsup fundus" appearance. These clinical findings characterized Sturge-weber syndrome. He presented with posterior retinal vessel tortuosity and vein-to-vein anastomoses at 44 weeks.

CONCLUSION

This is a rare case of documented progression of retinal vessel malformations in a patient with Sturge-Weber syndrome and retinopathy of prematurity.

Vascular Endothelial Growth Factor Signaling in Models of Oxygen-Induced Retinopathy: Insights Into Mechanisms of Pathology in Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is a leading cause of blindness in children worldwide. Blindness can occur from retinal detachment caused by pathologic retinal angiogenesis into the vitreous, termed intravitreal neovascularization (IVNV). Although agents that interfere with the bioactivity of vascular endothelial growth factor (VEGF) are now used to treat IVNV, concerns exist regarding the identification of optimal doses of anti-VEGF for individual infants and the effect of broad VEGF inhibition on physiologic angiogenesis in external organs or in the retina of a preterm infant. Therefore, it is important to understand VEGF signaling in both physiologic and pathologic angiogenesis in the retina. In this manuscript, we review the role of receptors that interact with VEGF in oxygen-induced retinopathy (OIR) models that represent features of ROP pathology. Specifically, we discuss our work regarding the regulation of VEGFR2 signaling in retinal endothelial cells to not only reduce severe ROP but also facilitate physiologic retinal vascular and neuronal development.

Small-Molecule Modulation of PPARs for the Treatment of Prevalent Vascular Retinal Diseases

Vascular-related retinal diseases dramatically impact quality of life and create a substantial burden on the healthcare system. Age-related macular degeneration, diabetic retinopathy, and retinopathy of prematurity are leading causes of irreversible blindness. In recent years, the scientific community has made great progress in understanding the pathology of these diseases and recent discoveries have identified promising new treatment strategies. Specifically, compelling biochemical and clinical evidence is arising that small-molecule modulation of peroxisome proliferator-activated receptors (PPARs) represents a promising approach to simultaneously address many of the pathological drivers of these vascular-related retinal diseases. This has excited academic and pharmaceutical researchers towards developing new and potent PPAR ligands. This review highlights recent developments in PPAR ligand discovery and discusses the downstream effects of targeting PPARs as a therapeutic approach to treating retinal vascular diseases.

Can Hematological Parameters be a Indicator Risk Factor in the Development of Retinopathy of Prematurity?

BACKGROUND

Hematological parameters have been investigated as being indicative of increased inflammatory response in morbidity of very preterm infants. This study aims to determine whether the hematologic parameters and ratios of preterms can be an indicative risk factor for the development of retinopathy of prematurity (ROP).

MATERIALS-METHODS

This retrospective cohort study examined newborns born before 32 weeks. Twenty-three patients treated with the diagnosis of ROP were included in the patient group. The control group included 23 patients who did not have ROP (no-ROP). Medical records of eligible preterm infants were retrospectively reviewed. Hemogram samples obtained from all patients during the first 24 h of life and samples of their mothers obtained before delivery were evaluated. The hemogram parameters of white blood cell (WBC) count, neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, lymphocyte/monocyte ratio, and platelet mass index were calculated.

RESULTS

No difference was observed between the groups in terms of demographic data. In terms of hematological parameters, maternal WBC counts of ROP patients were significantly higher than those of no-ROP patients and WBC counts of ROP patients were significantly lower than those of no-ROP patients.

CONCLUSIONS

This study found that high WBC counts in mothers before delivery and/or low WBC counts in preterms during the first postnatal day were higher in developed ROP. These results could lead to the development of prospective studies to assess the real prognostic value of WBC in ROP.

Protective Effects and Molecular Signaling of n-3 Fatty Acids on Oxidative Stress and Inflammation in Retinal Diseases

Oxidative stress and inflammation play crucial roles in the development and progression of retinal diseases. Retinal damage by various etiologies can result in retinopathy of prematurity (ROP), diabetic retinopathy (DR), and age-related macular degeneration (AMD). n-3 fatty acids are essential fatty acids and are necessary for homeostasis. They are important retinal membrane components and are involved in energy storage. n-3 fatty acids also have antioxidant and anti-inflammatory properties, and their suppressive effects against ROP, DR, and AMD have been previously evaluated. α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and their metabolites have been shown to alleviate retinal oxidative stress and inflammation involving various biological signaling pathways. In this review, we summarize the current understanding of the n-3 fatty acids effects on the mechanisms of these retinal diseases and how they exert their therapeutic effects, focusing on ALA, EPA, DHA, and their metabolites. This knowledge may provide new remedial strategies for n-3 fatty acids in the prevention and treatment of retinal diseases associated with oxidative stress and inflammation.

Oxidative Stress Markers and the Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is a leading cause of potentially preventable blindness in low birth weight preterm infants. Several perinatal and postnatal factors contribute to the incomplete maturation of retinal vascularization, leading to oxidative stress damage. Literature data suggest that the lack of equilibrium between pro-oxidants and anti-oxidants plays a key role. In the last decade, there has been an increasing interest in identifying the antecedents of ROP and the relevant pathogenic mechanisms involved. In this context, a panel of biomarkers was investigated in order to achieve early detection of oxidative stress occurrence and to prevent retinal damage. Several nutritional elements have been found to play a relevant role in ROP prevention. At this stage, no conclusive data have been shown to support the usefulness of one biomarker over another. Recently, the Food and Drugs Administration, the European Medicine Agency, and the National Institute of Health proposed a series of criteria in order to promote the inclusion of new biomarkers in perinatal clinical guidelines and daily practice. The aim of the present review is to offer an update on a panel of biomarkers, currently investigated as potential predictors of ROP, highlighting their strengths and weaknesses.

Vascular Regeneration for Ischemic Retinopathies: Hope from Cell Therapies

Retinal vascular diseases, such as diabetic retinopathy, retinopathy of prematurity, retinal vein occlusion, ocular ischemic syndrome and ischemic optic neuropathy, are leading causes of vision impairment and blindness. Whilst drug, laser or surgery-based treatments for the late stage complications of many of these diseases are available, interventions that target the early vasodegenerative stages are lacking. Progressive vasculopathy and ensuing ischemia is an underpinning pathology in many of these diseases, leading to hypoperfusion, hypoxia, and ultimately pathological neovascularization and/or edema in the retina and other ocular tissues, such as the optic nerve and iris. Therefore, repairing the retinal vasculature may prevent progression of ischemic retinopathies into late stage vascular complications. Various cell types have been explored for their vascular repair potential. Endothelial progenitor cells, mesenchymal stem cells and induced pluripotent stem cells are studied for their potential to integrate with the damaged retinal vasculature and limit ischemic injury. Clinical trials for some of these cell types have confirmed safety and feasibility in the treatment of ischemic diseases, including some retinopathies. Another promising avenue is mobilization of endogenous endothelial progenitors, whereby reparative cells are moved from their niche to circulating blood to target and home into ischemic tissues. Several aspects and properties of these cell types have yet to be elucidated. Nevertheless, we foresee that cell therapy, whether through delivery of exogenous or enhancement of endogenous reparative cells, will become a valuable and beneficial treatment for ischemic retinopathies.

Epithelial Membrane Protein 2 (EMP2) Promotes VEGF-Induced Pathological Neovascularization in Murine Oxygen-Induced Retinopathy

Purpose

Retinopathy of prematurity (ROP) is a leading cause of childhood blindness. ROP occurs as a consequence of postnatal hyperoxia exposure in premature infants, resulting in vasoproliferation in the retina. The tetraspan protein epithelial membrane protein-2 (EMP2) is highly expressed in the retinal pigment epithelium (RPE) in adults, and it controls vascular endothelial growth factor (VEGF) production in the ARPE-19 cell line. We, therefore, hypothesized that Emp2 knockout (Emp2 KO) protects against neovascularization in murine oxygen-induced retinopathy (OIR).

Methods

Eyes were obtained from wildtype (WT) and Emp2 KO mouse pups at P7, P12, P17, and P21 after normoxia or hyperoxia (P7-P12) exposure. Following hyperoxia exposure, RNA sequencing was performed using the retina/choroid layers obtained from WT and Emp2 KO at P17. Retinal sections from P7, P12, P17, and P21 were evaluated for Emp2, hypoxia-inducible factor 1α (Hif1α), and VEGF expression. Whole mount images were generated to assess vaso-obliteration at P12 and neovascularization at P17.

Results

Emp2 KO OIR mice demonstrated a decrease in pathologic neovascularization at P17 compared with WT OIR mice through evaluation of retinal vascular whole mount images. This protection was accompanied by a decrease in Hif1α at P12 and VEGFA expression at P17 in Emp2 KO animals compared with the WT animals in OIR conditions. Collectively, our results suggest that EMP2 enhances the effects of neovascularization through modulation of angiogenic signaling.

Conclusions

The protection of Emp2 KO mice against pathologic neovascularization through attenuation of HIF and VEGF upregulation in OIR suggests that hypoxia-induced upregulation of EMP2 expression in the neuroretina modulates HIF-mediated neuroretinal VEGF expression.

Pharmacologic interventions for the prevention and treatment of retinopathy of prematurity

Retinopathy of Prematurity (ROP) is a preventable neovascular retinal disease with a lifetime impact on vision and ocular morbidities. Retinal vessel immaturity and oxygen therapy, influenced or modulated by several risk factors including oxidative stress, intermittent hypoxia and desaturations, inflammation, infection, malnutrition, retinal growth factor deficiencies or excesses, and others are determinant factors of pathologic retinal angiogenesis and ROP. These factors are pharmacologic targets for prevention and/or rescue therapy. These drugs, include intravitreal anti-vascular endothelial growth factor drugs, erythropoietin, ocular propranolol, caffeine, antioxidants, insulin-like growth factor-I, and omega 3 poly-unsaturated fatty acids, and are promising therapies to prevent ROP, but require further studies. Topical ocular non-steroidal anti-inflammatory drugs (NSAIDs) target inflammatory cascade but the best, safest, and most effective ocular NSAID and formulation remain to be developed. Timing of drug intervention appears critical. Moreover, the complex interactions of the various pathophysiologic mechanisms resulting in aberrant angiogenesis thence ROP strongly suggest that drug combinations and synergisms may be required for effective prevention of ROP and a lifetime of blindness.

Effect of intravitreal and intraperitoneal cyanidin-3-glucoside injection in oxygen-induced retinopathy mouse model

Purpose:

To evaluate the effect of cyanidin-3-glucoside (C3G) in oxygen-induced retinopathy (OIR) mouse model.

Methods:

In this experimental study, 10 C57BL / 6J type mice exposed to room air comprised two control groups (n = 5 each; a negative control and a group receiving intravitreal sterile dimethyl sulfoxide [IVS DMSO]). Thirty C57BL / 6J type mice exposed to 75% ± 2% oxygen from postnatal day 7 to postnatal day 12 comprised the OIR groups. On postnatal day 12, these mice were randomized into six groups (n = 5 each): two OIR control groups (negative control and IVS DMSO), two intravitreal C3G groups (300 and 600 ng/μL), and two intraperitoneal C3G groups (0.05 and 0.1 mg/kg). We quantified neovascularization by counting endothelial cell proliferation on the vitreal side of the inner limiting membrane of the retina and examined histological and ultrastructural changes via light and electron microscopy and apoptosis by terminal deoxynucleotidyl transferase deoxy-UTP-nick end labeling.

Results:

The intravitreal C3G groups yielded lower endothelial cell counts compared with the intravitreal DMSO group. The intraperitoneal high-dose group had lower cell counts compared with the OIR control groups. Electron microscopy revealed significantly less mitochondrial dysmorphology in intravitreal groups and the high-dose intraperitoneal mice. We noted no difference in apoptotic cell count between the controls, low-dose intravitreal, and both intraperitoneal groups. However, apoptotic cell count was significantly higher in the high-dose intravitreal group.

Conclusion:

C3G suppresses endothelial cell proliferation in an OIR mouse model, leads to a reduced hyperoxia-induced mitochondrial dysmorphology, but increases apoptotic cell death in high concentrations.

New Lipid Mediators in Retinal Angiogenesis and Retinopathy

Retinal diseases associated with vascular destabilization and the inappropriate proliferation of retinal endothelial cells have major consequences on the retinal vascular network. In extreme cases, the development of hypoxia, the upregulation of growth factors, and the hyper-proliferation of unstable capillaries can result in bleeding and vision loss. While anti-vascular endothelial growth factor therapy and laser retinal photocoagulation can be used to treat the symptoms of late stage disease, there is currently no treatment available that can prevent disease progression. Cytochrome P450 enzymes metabolize endogenous substrates (polyunsaturated fatty acids) to bioactive fatty acid epoxides that demonstrate biological activity with generally protective/anti-inflammatory and insulin-sensitizing effects. These epoxides are further metabolized by the soluble epoxide hydrolase (sEH) to fatty acid diols, high concentrations of which have vascular destabilizing effects. Recent studies have identified increased sEH expression and activity and the subsequent generation of the docosahexaenoic acid-derived diol; 19,20-dihydroxydocosapentaenoic acid, as playing a major role in the development of diabetic retinopathy. This review summarizes current understanding of the roles of cytochrome P450 enzyme and sEH–derived PUFA mediators in retinal disease.

Late onset Descemet's membrane detachment: 15 years after limbal lensectomy with vitrectomy for ROP

A case of stage 4B retinopathy of prematurity (ROP) after successful retinal reattachment surgery with maintained vision presented with hazy cornea with spontaneous Descemet's membrane detachment (DMD) 15 years after the surgery, requiring Descemet Stripping Endothelial Keratoplasty (DSEK) to restore vision. There are reports of late spontaneous DMD after phacoemulsification or previous corneal surgeries. This report is unique as there is no published literature of spontaneous DMD after limbal surgery for ROP when searched in PubMed. The immature Descemet's membrane (DM), surgical intervention and changes in immature DM with age would have contributed to spontaneous DMD and warrant a long-term follow-up of premature kids.

Serum Vascular Endothelial Growth Factor Levels before and after Intravitreous Ranibizumab Injection for Retinopathy of Prematurity

Background

Retinopathy of prematurity (ROP) is one of the common complications of prematurity. Intravitreal injection of ranibizumab (IVR), an antivascular endothelial growth factor (VEGF) drug, showed significant benefit for ROP. However, there are concerns about systemic complications of anti-VEGF therapy in preterm infants.

Objectives

To evaluate serum VEGF level in the systemic circulation after IVR and the complications associated with IVR for the premature infants with ROP.

Methods

This prospective investigation assessed the serum concentrations of VEGF in ROP patients before and after IVR therapy. All the infants had binocular retinopathy and received IVR 0.25 mg per eye as the primary treatment. Serum samples were collected 1 day prior to injection and 1 day, 3 days, and 7 days after IVR treatment. Serum VEGF level was measured by the enzyme-linked immunosorbent assay (ELISA).

Results

Fifteen infants (6 girls and 9 boys) were enrolled. The serum concentrations of VEGF 1 day before and 1 day, 3 days, and 7 days after a total of 0.5 mg intravitreal injections of ranibizumab were 226.9 (198.4, 272.4), 12.8 (7.0, 22.4), 16 (12.0, 20.8), and 33.7 (24.0, 48.0) pg/ml, respectively. Serum VEGF levels decreased significantly at 1 day, 3 days, and 7 days after IVR treatment compared with pretreatment concentration (P < 0.05). Compared to days 1 and 3 after IVR, serum VEGF level at 7 days after IVR treatment increased significantly (P < 0.05).

Conclusion

Serum VEGF levels in patients with ROP were suppressed for at least 7 days after IVR treatment. Although the clinical significance of this phenomenon is uncertain, its safety profile requires further investigation.

Speed of Retinal Vascularization in Retinopathy of Prematurity: Risk and Protective Factors

Objective

The objective was to study the risk and protective factors involved in retinal vascular development of preterm infants with retinopathy of prematurity.

Methods

Between 2000 and 2017, 185 preterm infants were included in the protocol for retinopathy of prematurity. Risk factors associated with speed of retinal vascularization <0.5 disc diameter/week were studied in each of them.

Results

The statistically significant variables related to retinal vascular development <0.5 DD/w were intubation days, degree 3 of bronchopulmonary dysplasia, weight gain at 4-6 weeks, avascular temporal area, gestational age, number of transfusions, sepsis, number of risk factors, apnea at birth, presence of ductus arteriosus, and days of continuous positive airway pressure therapy. After the multivariate logistic regression analysis, only three variables were found to be significant: intubation days (p=0.005), degree 3 of bronchopulmonary dysplasia (p=0.022), and weight gain at 4–6 weeks (p=0.031).

Conclusion

In retinopathy of prematurity, degree 3 of bronchopulmonary dysplasia and intubation days cause delayed retinal vascular development, whereas greater postnatal weight gain favors an appropriate rate of retinal vascularization.

A review of treatment for retinopathy of prematurity

Introduction

Retinopathy of prematurity (ROP) is a leading cause of childhood blindness worldwide.

Areas covered

Recent methods to identify and manage treatment-warranted vascularly active ROP are recognized and being compared to standard care by laser treatment in prospective large-scale clinical studies. Pharmacologic anti-angiogenic (anti-VEGF) treatment has changed the natural history of vascularly active ROP by reducing stage 3 intravitreal neovascularization and extending physiologic retinal vascularization in many infants. Tractional retinal detachments in stage 4 ROP after treatment with anti-VEGF agents show additional fibrovascular complexity compared to eyes treated with laser only. We review current management and outcomes for vascularly active and fibrovascular retinal detachment in ROP (stages 3, 4, 5 ROP), highlighting the evidence from recent clinical studies. Included are technical details important in surgery for retinal detachment in ROP. Literature searches were employed through PubMed.

Expert opinion

Methods in pediatric imaging, safer pharmacologic treatments, and surgical techniques continue to advance to improve future ROP outcomes.

Gamma-Secretase Inhibitor, DAPT, Prevents the Development of Retinopathy of Prematurity in a Rat Model by Regulating the Delta-Like Ligand 4/Notch Homolog-1 (DLL4/Notch-1) Pathway

Background

Retinopathy of prematurity (ROP), or retrolental fibroplasia, affects premature infants who have undergone intensive care with oxygen therapy. This study aimed to investigate the inhibitory effect of the gamma-secretase inhibitor, DAPT, on neovascularization and its mechanism in a rat model of ROP.

Material/Methods

Sixty neonatal Sprague-Dawley (SD) rats included the control group (n=20), the model group (n=20), and the DAPT-treated group (n=20). The rat model of ROP was established using repeat cycles of oxygen inhalation. Enzyme-linked immunosorbent assay (ELISA) measured serum levels of vascular endothelial growth factor (VEGF), VEGF receptor-1 (VEGFR-1), and VEGFR-2. Histology of the retinal tissue included immunohistochemistry for the expression of Notch homolog-1 (Notch-1) and delta-like ligand 4 (DLL4). Retinal mRNA levels of DLL4, Notch-1, VEGF, VEGFR-1, and VEGFR-2 were evaluated with quantitative real-time polymerase chain reaction (qRT-PCR).

Results

The rat model of ROP showed increased serum levels of VEGF, VEGFR-1, and VEGFR-2 compared with the control group, which were decreased in the DAPT group. Histology of the retinal tissue in the model group showed degeneration of the retinal ganglion cells, and immunohistochemistry showed increased expression of Notch-1 and DLL4 compared with the control group and DAPT group. Retinal tissue in the model group had increased mRNA levels of DLL4, Notch-1, VEGF, VEGFR-1, and VEGFR-2 compared with the control group, and the DAPT group.

Conclusions

In a rat model, treatment with DAPT reduced the retinal changes associated with ROP with a mechanism that involved VEGF and its receptors through the DLL4/Notch-1 pathway.

Severe Visual Impairments in Infants and Toddlers in the United States

Introduction

This article describes the most prevalent visual conditions and other demographic characteristics of 5,931 young children with severe visual impairments in 28 states in the United States, the largest sample reported to date. The information presented in this article can assist in planning and implementing programs.

Method

The data were collected at the time of entry into specialized early intervention programs for young children with visual impairments through reviews of records, interviews, and direct observations. They were sent to Babies Count: The National Registry for Children with Visual Impairments, Birth to 3 Years at the American Printing House for the Blind. The data were collected and entered between January 2005 and April 2011.

Results

Cortical visual impairment, retinopathy of prematurity (ROP), and optic nerve hypoplasia were the three most prevalent diagnoses. Approximately 60% were identified as being legally blind, and 65% had disabilities in addition to visual impairments. The mean age of the children at the time of diagnosis was 4.9 (SD = 5.7) months, referral to specialized programs was at 10.5 (SD = 7.8) months, and entry into specialized programs was at 11.6 (SD = 8.0) months. There was an average lag of 5.6 months between the diagnosis and referral.

Discussion

Cortical visual impairment, ROP, and optic nerve hypoplasia continue to be the leading causes of severe, uncorrectable visual impairments in children in the United States. ROP appears to be decreasing in prevalence; however, more children with ROP appear to have additional disabilities. The lag of 5.6 months between diagnosis and referral, a longer lag than was previously reported, is of concern.

Implications for practitioners

Information about the characteristics of children with severe uncorrectable visual conditions is valuable for communicating with families, planning and implementing early intervention and educational programs, and collaborating with medical professionals.

Antenatal IL-1-dependent inflammation persists postnatally and causes retinal and sub-retinal vasculopathy in progeny

Antenatal inflammation as seen with chorioamnionitis is harmful to foetal/neonatal organ development including to eyes. Although the major pro-inflammatory cytokine IL-1β participates in retinopathy induced by hyperoxia (a predisposing factor to retinopathy of prematurity), the specific role of antenatal IL-1β associated with preterm birth (PTB) in retinal vasculopathy (independent of hyperoxia) is unknown. Using a murine model of PTB induced with IL-1β injection in utero, we studied consequent retinal and choroidal vascular development; in this process we evaluated the efficacy of IL-1R antagonists. Eyes of foetuses exposed only to IL-1β displayed high levels of pro-inflammatory genes, and a persistent postnatal infiltration of inflammatory cells. This prolonged inflammatory response was associated with: (1) a marked delay in retinal vessel growth; (2) long-lasting thinning of the choroid; and (3) long-term morphological and functional alterations of the retina. Antenatal administration of IL-1R antagonists - 101.10 (a modulator of IL-1R) more so than Kineret (competitive IL-1R antagonist) - prevented all deleterious effects of inflammation. This study unveils a key role for IL-1β, a major mediator of chorioamnionitis, in causing sustained ocular inflammation and perinatal vascular eye injury, and highlights the efficacy of antenatal 101.10 to suppress deleterious inflammation.

Correlation of Retinopathy of Prematurity with Bronchopulmonary Dysplasia

Retinopathy of prematurity (ROP) and bronchopulmonary dysplasia (BPD) are diseases that occur only in preterm infants. The etiology of these disorders is multifactorial; however, it is believed that some of the factors in children presenting with BPD affect both the initiation and severity of ROP. The aim of the study was to evaluate the degree of clinical severity of ROP in infants with BPD compared to those without BPD.

Ischemic Retinopathies: Oxidative Stress and Inflammation

Ischemic retinopathies (IRs), such as retinopathy of prematurity (ROP), diabetic retinopathy (DR), and (in many cases) age-related macular degeneration (AMD), are ocular disorders characterized by an initial phase of microvascular changes that results in ischemia, followed by a second phase of abnormal neovascularization that may culminate into retinal detachment and blindness. IRs are complex retinal conditions in which several factors play a key role during the development of the different pathological stages of the disease. Increasing evidence reveals that oxidative stress and inflammatory processes are important contributors to the pathogenesis of IRs. Despite the beneficial effects of the photocoagulation and anti-VEGF therapy during neovascularization phase, the need to identify novel targets to prevent initial phases of these ocular pathologies is still needed. In this review, we provide an update on the involvement of oxidative stress and inflammation in the progression of IRs and address some therapeutic interventions by using antioxidants and anti-inflammatory agents.

Retinal vasculature development in health and disease

Development of the retinal vasculature is based on highly coordinated signalling between different cell types of the retina, integrating internal metabolic requirements with external influences such as the supply of oxygen and nutrients. The developing mouse retinal vasculature is a useful model system to study these interactions because it is experimentally accessible for intra ocular injections and genetic manipulations, can be easily imaged and develops in a similar fashion to that of humans. Research using this model has provided insights about general principles of angiogenesis as well as pathologies that affect the developing retinal vasculature. In this review, we discuss recent advances in our understanding of the molecular and cellular mechanisms that govern the interactions between neurons, glial and vascular cells in the developing retina. This includes a review of mechanisms that shape the retinal vasculature, such as sprouting angiogenesis, vascular network remodelling and vessel maturation. We also explore how the disruption of these processes in mice can lead to pathology - such as oxygen induced retinopathy - and how this translates to human retinopathy of prematurity.

Retinopathy of prematurity: inflammation, choroidal degeneration, and novel promising therapeutic strategies

Retinopathy of prematurity (ROP) is an important cause of childhood blindness globally, and the incidence is rising. The disease is characterized by initial arrested retinal vascularization followed by neovascularization and ensuing retinal detachment causing permanent visual loss. Although neovascularization can be effectively treated via retinal laser ablation, it is unknown which children are at risk of entering this vision-threatening phase of the disease. Laser ablation may itself induce visual field deficits, and there is therefore a need to identify targets for novel and less destructive treatments of ROP. Inflammation is considered a key contributor to the pathogenesis of ROP. A large proportion of preterm infants with ROP will have residual visual loss linked to loss of photoreceptor (PR) and the integrity of the retinal pigment epithelium (RPE) in the macular region. Recent studies using animal models of ROP suggest that choroidal degeneration may be associated with a loss of integrity of the outer retina, a phenomenon so far largely undescribed in ROP pathogenesis. In this review, we highlight inflammatory and neuron-derived factors related to ROP progression, as well, potential targets for new treatment strategies. We also introduce choroidal degeneration as a significant cause of residual visual loss following ROP. We propose that ROP should no longer be considered an inner retinal vasculopathy only, but also a disease of choroidal degeneration affecting both retinal pigment epithelium and photoreceptor integrity.

Genome-wide expression differences in anti-Vegf and dexamethasone treatment of inflammatory angiogenesis in the rat cornea

Angiogenesis as a pathological process in the eye can lead to blindness. In the cornea, suppression of angiogenesis by anti-VEGF treatment is only partially effective while steroids, although effective in treating inflammation and angiogenesis, have broad activity leading to undesirable side effects. In this study, genome-wide expression was investigated in a suture-induced corneal neovascularization model in rats, to investigate factors differentially targeted by dexamethasone and anti-Vegf. Topical treatment with either rat-specific anti-Vegf, dexamethasone, or normal goat IgG (sham) was given to sutured corneas for 48 hours, after which in vivo imaging, tissue processing for RNA microarray, and immunofluorescence were performed. Dexamethasone suppressed limbal vasodilation (P < 0.01) and genes in PI3K-Akt, focal adhesion, and chemokine signaling pathways more effectively than anti-Vegf. The most differentially expressed genes were confirmed by immunofluorescence, qRTPCR and Western blot. Strong suppression of Reg3g and the inflammatory chemokines Ccl2 and Cxcl5 and activation of classical complement pathway factors C1r, C1s, C2, and C3 occurred with dexamethasone treatment, effects absent with anti-Vegf treatment. The genome-wide results obtained in this study provide numerous potential targets for specific blockade of inflammation and angiogenesis in the cornea not addressed by anti-Vegf treatment, as possible alternatives to broad-acting immunosuppressive therapy.

The Nicotinic Cholinergic Pathway Contributes to Retinal Neovascularization in a Mouse Model of Retinopathy of Prematurity

Purpose

To investigate the role of nicotinic acetylcholine receptors (nAChRs) in retinal vascular development and ischemia-induced retinal neovascularization (NV).

Methods

The expression of nAChR subtypes and VEGF signaling pathway components was assessed in mice with and without oxygen-induced ischemic retinopathy by comparing expression levels at postnatal day (P) 14 and P17 in mice exposed to 75% oxygen from P7 to P12 and returned to room air versus mice pups that were exposed to ambient oxygen levels during the same period. The effect of topical or intraocular injection of mecamylamine, a nonspecific nAChR antagonist, or targeted deletion of α7- or α9-nAChRs on ischemia-induced retinal NV was determined by comparing the amount of retinal NV at P17 in these mice versus appropriate controls.

Results

The expression of nAChR subunits and components of the VEGF signaling pathways was increased in ischemic retina. Topical application or intraocular injection of mecamylamine decreased retinal NV in this model. Mecamylamine had no effect on normal retinal vascular development or on revascularization of the central retinal area of nonperfusion in mice with ischemic retinopathy. Targeted deletion of α9, but not α7, nAChR receptor subunits reduced retinal NV in mice with ischemic retinopathy.

Conclusion

These data suggest that nAChR signaling, primarily through the α9 nAChR subunit, contributes to ischemia-induced retinal NV, but not retinal vascular development. Mecamylamine or a specific α9 nAChR antagonist could be considered for treatment of retinopathy of prematurity and other ischemic retinopathies.

Impaired nephrogenesis in neonatal rats with oxygen-induced retinopathy

BACKGROUND

Preterm neonates are born while nephrogenesis is ongoing, and are commonly exposed to factors in a hyperoxic environment that can impair renal development. Oxidative stress has also been implicated in the development of retinopathy of prematurity (ROP). The rat model of oxygen-induced retinopathy (OIR) is the most clinically relevant model of ROP because its biologic features closely resemble those of ROP in preterm infants. We investigated impaired renal development in a rat model of OIR.

METHODS

Newborn Sprague-Dawley rats were maintained in either a normoxic (room air, 21% O₂ ; control group) or a controlled hyperoxic (80% O₂ ; OIR group) environment from birth to postnatal day (P) 12. All pups were then raised in room air from P12 to P19.

RESULTS

The hyperoxic environment led to significantly higher urinary excretion of 8-hydroxy-2'-deoxyguanosine, a marker of oxidative DNA damage, and a reduction in nephrogenic zone width at P5 in OIR pups. Additionally, glomerular count was significantly reduced by 20% in the OIR group, and avascular and neovascular changes in the retina were observed only in the OIR group at P19. Messenger RNA levels of vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor-β, essential angiogenic cytokines for glomerulogenesis, in the renal cortex were significantly lower at P5 and significantly higher at P19 in the OIR group compared with controls.

CONCLUSION

Renal impairment was caused by exposure to a hyperoxic environment during nephrogenesis, and the pathology of the impaired nephrogenesis in this OIR model reflects the characteristics of ROP observed in preterm infants.

Insulin-Like Growth Factor Binding Protein-Related Protein 1 Inhibit Retinal Neovascularization in the Mouse Model of Oxygen-Induced Retinopathy

PURPOSE

To explore the inhibitory effect of insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) on retinal angiogenesis and its underlying molecular mechanisms in the mouse model of oxygen-induced retinopathy (OIR).

METHODS

C57BL/6J mice were classified into three groups as control group, OIR nonintervention group, and OIR intervention group. Postnatal day 12 (P12) mice in OIR intervention group were received recombinant mouse IGFBP-rP1 (50, 100, and 200 ng/mL) intravitreal injection. Five days later, the proliferative neovascular responses were estimated by quantifying the new vessel areas in flattening retinal tissues stained by high molecular fluorescein isothiocyanate-dextran and counting the numbers of neovascular cell nuclei breaking through the internal limiting membrane in cross sections. Expressions of phospho-extracellular signal-regulated kinase 1/2 (p-ERK1/2), ERK1/2, and vascular endothelial growth factor (VEGF) proteins in retinal tissues were assessed by western blot analysis.

RESULTS

Irregular neovascularization, nonperfusion region, and fluorescence leakage were observed in OIR models. The expression of retinal p-ERK1/2 and VEGF proteins were significantly upregulated in OIR nonintervention group compared with control group. The area ratio of retinal new vessels and the number of neovascular cell nuclei in OIR intervention group both decreased significantly, following the downregulation of retinal p-ERK1/2 protein expression and VEGF protein expression in a dose-dependent manner. Moreover, there was no significant difference in retinal ERK1/2 protein expression.

CONCLUSIONS

IGFBP-rP1 inhibits retinal angiogenesis by blocking ERK signaling pathway and downregulating VEGF expression in the mouse model of OIR. It highlights the potential importance of IGFBP-rP1 serving as a target of gene therapy for retinal neovascularization in the future.

Neonatal Intermittent Hypoxia, Reactive Oxygen Species, and Oxygen-Induced Retinopathy

Most of the major morbidities in the preterm newborn are caused by or are associated with oxygen-induced injuries and are aptly called "oxygen radical diseases in neonatology or ORDIN". These include bronchopulmonary dysplasia, retinopathy of prematurity, periventricular leukomalacia, intraventricular hemorrhage, necrotizing enterocolitis and others. Relative hyperoxia immediately after birth, immature antioxidant systems, biomolecular events favoring oxidative stress such as iron availability and the role of hydrogen peroxide as a key molecular mediator of these events are reviewed. Potential therapeutic strategies such as caffeine, antioxidants, non-steroidal anti-inflammatory drugs, and others targeted to these critical sites may help prevent oxidative radical diseases in the newborn resulting in improved neonatal outcomes.

The Multiple Facets of Lutein: A Call for Further Investigation in the Perinatal Period

Lutein may have important antioxidant actions in free-radical-mediated diseases, in addition to its well-known antioxidant and cytoprotective effects on macula and photoreceptors. The peculiar perinatal susceptibility to oxidative stress indicates that prophylactic use of antioxidants as lutein could help to prevent or at least to reduce oxidative stress related diseases in newborns. Since lutein is not synthesized by humans, the intake primarily depends on diet or supplementation. Newborns receive lutein exclusively from breast milk. Lutein supplementation in term newborns has been reported to reduce oxidative stress and increase antioxidant capacities in the first days of life. Innovative frontiers concerning lutein supplementation are orientated toward cardiometabolic health improvement and cognitive benefits. The safety of lutein as an antioxidant agent has been confirmed in experimental and clinical studies, but its routine use is not recommended in perinatal period. This review summarizes what is known about the role of lutein as an antioxidant and anti-inflammatory agent in animal model and humans.

Impact of bronchopulmonary dysplasia on brain and retina

Many premature newborns develop bronchopulmonary dysplasia (BPD), a chronic lung disease resulting from prolonged mechanical ventilation and hyperoxia. BPD survivors typically suffer long-term injuries not only to the lungs, but also to the brain and retina. However, currently it is not clear whether the brain and retinal injuries in these newborns are related only to their prematurity, or also to BPD. We investigated whether the hyperoxia known to cause histologic changes in the lungs similar to BPD in an animal model also causes brain and retinal injuries. Sprague Dawley rat pups were exposed to hyperoxia (95% O₂, ‘BPD’ group) or room air (21% O₂, ‘control’ group) from postnatal day 4–14 (P4–14); the rat pups were housed in room air between P14 and P28. At P28, they were sacrificed, and their lungs, brain, and eyes were extracted. Hematoxylin and eosin staining was performed on lung and brain sections; retinas were stained with Toluidine Blue. Hyperoxia exposure resulted in an increased mean linear intercept in the lungs (P<0.0001). This increase was associated with a decrease in some brain structures [especially the whole-brain surface (P=0.02)], as well as a decrease in the thickness of the retinal layers [especially the total retina (P=0.0008)], compared to the room air control group. In addition, a significant negative relationship was observed between the lung structures and the brain (r=−0.49, P=0.02) and retina (r=−0.70, P=0.0008) structures. In conclusion, hyperoxia exposure impaired lung, brain, and retina structures. More severe lung injuries correlated with more severe brain and retinal injuries. This result suggests that the same animal model of chronic neonatal hyperoxia can be used to simultaneously study lung, brain and retinal injuries related to hyperoxia.

Summary: Our results suggest that the same animal model of chronic neonatal hyperoxia can be used to simultaneously study lung, brain and retinal injuries related to hyperoxia.

Insight into SUCNR1 (GPR91) structure and function

SUCNR1 (or GPR91) belongs to the family of G protein-coupled receptors (GPCR), which represents the largest group of membrane proteins in human genome. The majority of marketed drugs targets GPCRs, directly or indirectly. SUCNR1 has been classified as an orphan receptor until a landmark study paired it with succinate, a citric acid cycle intermediate. According to the current paradigm, succinate triggers SUCNR1 signaling pathways to indicate local stress that may affect cellular metabolism. SUCNR1 implication has been well documented in renin-induced hypertension, ischemia/reperfusion injury, inflammation and immune response, platelet aggregation and retinal angiogenesis. In addition, the SUCNR1-induced increase of blood pressure may contribute to diabetic nephropathy or cardiac hypertrophy. The understanding of SUCNR1 activation, signaling pathways and functions remains largely elusive, which calls for deeper investigations. SUCNR1 shows a high potential as an innovative drug target and is probably an important regulator of basic physiology. In order to achieve the full characterization of this receptor, more specific pharmacological tools such as small-molecules modulators will represent an important asset. In this review, we describe the structural features of SUCNR1, its current ligands and putative binding pocket. We give an exhaustive overview of the known and hypothetical signaling partners of the receptor in different in vitro and in vivo systems. The link between SUCNR1 intracellular pathways and its pathophysiological roles are also extensively discussed.

Lutein, Zeaxanthin, and meso-Zeaxanthin in the Clinical Management of Eye Disease

Lutein, zeaxanthin, and meso-zeaxanthin are xanthophyll carotenoids found within the retina and throughout the visual system. The retina is one of the most metabolically active tissues in the body. The highest concentration of xanthophylls is found within the retina, and this selective presence has generated many theories regarding their role in supporting retinal function. Subsequently, the effect of xanthophylls in the prevention and treatment of various eye diseases has been examined through epidemiological studies, animal studies, and clinical trials. This paper attempts to review the epidemiological studies and clinical trials investigating the effects of xanthophylls on the incidence and progression of various eye diseases. Observational studies have reported that increased dietary intake and higher serum levels of lutein and zeaxanthin are associated with lower risk of age-related macular degeneration (AMD), especially late AMD. Randomized, placebo-controlled clinical trials have demonstrated that xanthophyll supplementation increases macular pigment levels, improves visual function, and decreases the risk of progression to late AMD, especially neovascular AMD. Current publications on the preventive and therapeutic effects of lutein and zeaxanthin on cataracts, diabetic retinopathy, and retinopathy of prematurity have reported encouraging results.

Neuroprotective effect of Myo/Nog cells in the stressed retina

Myo/Nog cells are essential for eye development in the chick embryo and respond to injury in adult tissues. These cells express mRNA for the skeletal muscle specific transcription factor MyoD, the bone morphogenetic protein (BMP) inhibitor Noggin and the cell surface protein recognized by the G8 monoclonal antibody (mAb). In this study, we determined that Myo/Nog cells are present in low numbers in the retina of the mouse eye. G8-positive Myo/Nog cells were distinguished from neuronal, Müller and microglial cells that were identified with antibodies to calretinin, Chx10, glial fibrillary acidic protein and ionized calcium binding adaptor molecule 1, respectively. In the neonatal retina, the number of Myo/Nog cells increased in parallel with cell death induced by transient exposure to hyperoxia. In this model of retinopathy of prematurity, depletion of Myo/Nog cells by intravitreal injection of the G8 mAb and complement increased cell death. These findings demonstrate that Myo/Nog cells are a distinct population of cells, not previously described in the retina, which increases in response to retinal damage and mitigate hypoxia-induced cell death.