Screening and novel therapies for retinopathy of prematurity - A review

Extracellular vesicles and preterm infant diseases

With the continuous improvement in perinatal care, the number of viable preterm infants is gradually increasing, along with the rise in preterm-related diseases such as necrotizing enterocolitis, bronchopulmonary dysplasia, perinatal brain injury, retinopathy of prematurity, and sepsis. Due to the unique pathophysiology of preterm infants, diagnosing and treating these diseases has become particularly challenging, significantly affecting their survival rate and long-term quality of life. Extracellular vesicles (EVs), as key mediators of intercellular communication, play an important regulatory role in the pathophysiology of these diseases. Because of their biological characteristics, EVs could serve as biomarkers and potential therapeutic agents for preterm-related diseases. This review summarizes the biological properties of EVs, their relationship with preterm-related diseases, and their prospects for diagnosis and treatment. EVs face unique challenges and opportunities for clinical applications.

Incidence and Risk Factors of Retinopathy of Prematurity in Southeastern Iran: A Retrospective Cohort Study

BACKGROUND

Retinopathy of prematurity (ROP) is a significant cause of preventable premature infant vision loss. Many studies have reported different risk factors depending on the region. In this study, we evaluated the incidence of ROP and associated risk factors in a referral eye hospital in southeastern Iran.

METHODS

This was a retrospective cohort study of preterm infants with birth weight (BW)≤2000 g or gestational age (GA)≤34 weeks and infants with GA between 34-37 weeks or GA<37 weeks and BW>2000 g referred by their pediatricians to our center from March 2022 until March 2023.

RESULTS

Totally, 920 infants met the inclusion criteria for the study. The incidence of ROP and ROP requiring treatment was 20.2% and 3.58% respectively. Results of logistic regression analysis showed higher GA and BW as protective factors against ROP occurrence. History of blood transfusion and phototherapy increased ROP development.

CONCLUSION

Lower GA, lower BW, history of blood transfusion, and phototherapy were associated with ROP development. Phototherapy decreased the need for treatment among ROP patients.

Cytokine and growth factor correlation networks associated with morbidities in extremely preterm infants

BACKGROUND

Cytokines and growth factors (GF) have been implicated in the development of retinopathy of prematurity (ROP) and bronchopulmonary dysplasia (BPD). We hypothesize that even small coordinated changes in inflammatory proteins or GFs may reveal changes in underlying regulating mechanisms that do not induce obvious changes in concentration of individual proteins. We therefore applied correlation network analysis of serum factors to determine early characteristics of these conditions.

METHODS

Concentrations of 17 cytokines and five GFs were measured and analysed in blood samples from cord blood, on day one and during the following month in 72 extremely preterm infants. Spearman's correlation networks distinguishing BPD and severe ROP patients from non-affected were created.

RESULTS

Most cytokine concentrations correlated positively with each other and negatively with GFs. Very few individual cytokines differed between patients with and without ROP or BPD. However, networks of differently correlated serum factors were characteristic of the diseases and changed with time. In ROP networks, EPO, G-CSF and IL-8 (cord blood), BDNF and VEGF-A (first month) were prominent. In BPD networks, IL-1β, IGF-1 and IL-17 (day one) were noted.

CONCLUSIONS

Network analysis identifies protein signatures related to ROP or BPD in extremely preterm infants. The identified interactions between serum factors are not evident from the analysis of their individual levels, but may reveal underlying pathophysiological mechanisms in the development of these diseases.

Retinopathy of Prematurity in Eight Portuguese Neonatal Intensive Care Units: Incidence, Risk Factors, and Progression-A Prospective Multicenter Study

BACKGROUND/OBJECTIVES

Retinopathy of prematurity (ROP) is a retinal neovascular disease affecting preterm infants. Identifying risk factors for its development and progression is critical for effective screening and prevention. This study aimed to analyze the incidence of ROP and identify key risk factors for its development and progression.

METHODS

We conducted a prospective, observational cohort study on 455 neonates (gestational age [GA] < 32 weeks or birth weight < 1500 g) across eight Portuguese NICUs.

RESULTS

ROP incidence was 37.8%, with 4.6% requiring treatment. Multivariate analysis identified low GA and the number of red blood cell (RBC) transfusions as significant factors for ROP development and progression. After adjusting for these variables, platelet transfusions, high maximum fraction of inspired oxygen (FiO2) in the second week, and surfactant use remained significantly associated with ROP development, while early and late sepsis, maternal chronic hypertension, and delayed enteral nutrition were associated with progression to ROP requiring treatment.

CONCLUSIONS

These findings underscore the importance of addressing low GAs and adult RBC transfusions in ROP risk management and suggest that maximum FiO2, platelet transfusions, and sepsis also play crucial roles. Larger studies are needed to validate these results and explore preventive interventions, particularly regarding the impact of multiple adult RBC transfusions on fetal hemoglobin percentages.

Risk factors for the time to development of retinopathy of prematurity in premature infants in Iran: a machine learning approach

BACKGROUND

Retinopathy of prematurity (ROP), is a preventable leading cause of blindness in infants and is a condition in which the immature retina experiences abnormal blood vessel growth. The development of ROP is multifactorial; nevertheless, the risk factors are controversial. This study aimed to identify risk factors of time to development of ROP in Iran.

METHODS

This historical cohort study utilized data from the hospital records of all newborns referred to the ROP department of Farabi Hospital (from 2017 to 2021) and the NICU records of infants referred from Mahdieh Hospital to Farabi Hospital. Preterm infants with birth weight (BW) ≤ 2000 g or gestational age (GA) < 34 wk, as well as selected infants with an unstable clinical course, as determined by their pediatricians or neonatologists, with BW > 2000 g or GA ≥ 34 wk. The outcome variable was the time to development of ROP (in weeks). Random survival forest was used to analyze the data.

RESULTS

A total of 338 cases, including 676 eyes, were evaluated. The mean GA and BW of the study group were 31.59 ± 2.39 weeks and 1656.72 ± 453.80 g, respectively. According to the criteria of minimal depth and variable importance, the most significant predictors of the time to development of ROP were duration of ventilation, GA, duration of oxygen supplementation, bilirubin levels, duration of antibiotic administration, duration of Total Parenteral Nutrition (TPN), mother age, birth order, number of surfactant administration, and on time screening. The concordance index for predicting survival of the fitted model was 0.878.

CONCLUSION

Our findings indicated that the duration of ventilation, GA, duration of oxygen supplementation, bilirubin levels, duration of antibiotic administration, duration of TPN, mother age, birth order, number of surfactant administrations, and on time screening are potential risk factors of prognosis of ROP. The associations between identified risk factors were mostly nonlinear. Therefore, it is recommended to consider the nature of these relationships in managing treatment and designing early interventions.

Comparison of two different oxygen saturation target ranges for automated oxygen control in preterm infants: a randomised cross-over trial

OBJECTIVE

To compare the effect of peripheral oxygen saturation (SpO2) target range (TR) (either 91%-95% and 92%-96%) on the frequency and duration of hypoxic and hyperoxic episodes while on automated oxygen control using the OxyGenie controller.

DESIGN

Randomised cross-over study.

SETTING

Tertiary-level neonatal unit in the Netherlands.

PATIENTS

Infants (n=27) with a median (IQR) gestational age of 27+0 (25+5-27+3) weeks and postnatal age of 16 (10-22) days, receiving invasive or non-invasive respiratory support.

INTERVENTIONS

In both groups supplemental oxygen was titrated to a TR of 91%-95% (TRlow) or 92%-96% (TRhigh) by the OxyGenie controller (SLE6000 ventilator) for 24 hours each, in random sequence. After a switch in TR, a 1-hour washout period was applied to prevent carry-over bias.

MAIN OUTCOME MEASURES

Frequency and duration of hypoxic (SpO2<80% for ≥1 s) and hyperoxic episodes (SpO2>98% for ≥1 s).

RESULTS

Hypoxic episodes were less frequent when the higher range was targeted (TRhigh vs TRlow: 2.5 (0.7-6.2)/hour vs 2.4 (0.9-10.2)/hour, p=0.02), but hyperoxic episodes were more frequent (5.3 (1.8-12.3)/hour vs 2.9 (1.0-7.1)/hour, p<0.001). The duration of the out-of-range episodes was not significantly different (hypoxia: 4.7 (2.8-7.1) s vs 4.4 (3.7-6.5) s, p=0.67; hyperoxia: 4.3 (3.3-4.9) s vs 3.9 (2.8-5.5) s, p=0.89).

CONCLUSION

Targeting a higher SpO2 TR with the OxyGenie controller reduced hypoxic episodes but increased hyperoxic episodes. This study highlights the feasibility of using an automated oxygen titration device to explore the effects of subtle TR adjustments on clinical outcomes in neonatal care.

TRIAL REGISTRATION NUMBER

NL9662.

Mechanical Ventilation, Retinal Avascularity and Rate of Vascularisation: A Triad of Predictors for Retinopathy of Prematurity Treatment

AIM

The temporal avascular area of the retina and the duration of mechanical ventilation (DMV) may predict the need to treat retinopathy of prematurity (ROP). This study considers whether the rate of retinal vascularisation and related risk factors should be included in a predictive model of the need for ROP treatment.

METHODS

This single-centre, observational retrospective case-control study was conducted on 276 preterm infants included in an ROP screening programme. All had undergone at least three examinations of the fundus. The main outcome measures considered were DMV (in days of treatment), the temporal avascular area (in disc diameters, DD) and the rate of temporal retinal vascularisation (DD/week).

RESULTS

The multivariate logistic model that best explains ROP treatment (R2 = 63.1%) has three significant risk factors: each additional day of mechanical ventilation (OR, 1.05 [95% CI, 1.02-1.09]; p = 0.001); each additional DD of temporal avascular area (OR, 2.2 [95% CI, 1.7-2.9]; p < 0.001) and a vascularisation rate <0.5 DD/week (OR, 19.0 [95% CI, 6.5-55.5]; p < 0.001). Two tables are presented for calculating the expected need for ROP treatment according to these three risk factors.

CONCLUSIONS

A greater DMV, a broad avascular area of the temporal retina at the first binocular screening and slow retinal vascularisation strongly predict the need for ROP treatment. The predictive model we describe must be validated externally in other centres.

A Network Meta-Analysis of Success Rates following Low Dosage Anti-VEGF for Retinopathy of Prematurity

PURPOSE

To search the low dosage of anti-VEGF best for primary therapies on retinopathy of prematurity (ROP) in terms of success rate.

METHODS

We searched Medline(Pubmed), Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) databases only for randomized controlled trials that had been reported as of March 3, 2023. We included studies that used bevacizumab, aflibercept and conbercept for ROP with comparable cohorts and treatment criteria. This study was performed according the pre-specified protocol registered with PROSPERO (CRD42021270077) and the Preferred Reporting Items for Systematic Reviews and Meta-Analysis checklist. Those with animal and cell experiments, non-randomized case-control, or single case report were excluded. Frequentist network meta-analyses determined the surface under the cumulative ranking (SUCRA) of the success rate of each dose range group and compared pairs of treatments via STATA 15.

RESULT

Since non-RCT research were excluded, aflflibercept and conbercept studies were excluded. Therefore, only 6 bevacizumab studies were included in final meta-analysis: Inconsistency was not detected in this study via global inconsistent model test, loop inconsistency and local inconsistent model test (p > 0.05). In addition, a consistent model test has been passed in this study (p > 0.05). Little bias was detected via funnel plot. Since bevacizumab adult standard dose of single-injection is 1.25 mg, the concentration groups were converted according to the proportion of adult standard dose, such as 1/2, [1/5, 1/6.25], [1/10, 1/12.5], [1/19.8, 1/78.1], [1/156.3, 1/625]. The SUCRA of [1/10, 1/12.5] dose group were the best of largest probability to achieve success. However, [1/156.3, 1/625] dose group was the worst dose to achieve success in the five dose groups. The success rate ranking of league chart in this study is that [1/10, 1/12.5] > [1/5, 1/6.25] > 1/2 ≈ [1/19.8, 1/78.1] > [1/156.3, 1/625].

CONCLUSIONS

[1/10, 1/12.5] were the best dosage ranges to achieve maximal medicine success. [1/156.3, 1/625] was the worst ineffective in the five dose ranges.

Harnessing the therapeutic potential of the stem cell secretome in neonatal diseases

Preterm birth and intrapartum related complications account for a substantial amount of mortality and morbidity in the neonatal period despite significant advancements in neonatal-perinatal care. Currently, there is a noticeable lack of curative or preventative therapies available for any of the most common complications of prematurity including bronchopulmonary dysplasia, necrotizing enterocolitis, intraventricular hemorrhage, periventricular leukomalacia and retinopathy of prematurity or hypoxic-ischemic encephalopathy, the main cause of perinatal brain injury in term infants. Mesenchymal stem/stromal cell-derived therapy has been an active area of investigation for the past decade and has demonstrated encouraging results in multiple experimental models of neonatal disease. It is now widely acknowledged that mesenchymal stem/stromal cells exert their therapeutic effects via their secretome, with the principal vector identified as extracellular vesicles. This review will focus on summarizing the current literature and investigations on mesenchymal stem/stromal cell-derived extracellular vesicles as a treatment for neonatal diseases and examine the considerations to their application in the clinical setting.

Clinical outcomes of preterm infants while using automated controllers during standard care: comparison of cohorts with different automated titration strategies

OBJECTIVE

To compare short-term clinical outcome after using two different automated oxygen controllers (OxyGenie and CLiO₂).

DESIGN

Propensity score-matched retrospective observational study.

SETTING

Tertiary-level neonatal unit in the Netherlands.

PATIENTS

Preterm infants (OxyGenie n=121, CLiO₂ n=121) born between 24+0-29+6 weeks of gestation. Median (IQR) gestational age in the OxyGenie cohort was 28+3 (26+3.5-29+0) vs 27+5 (26+5-28+3) in the CLiO₂ cohort, respectively 42% and 46% of infants were male and mean (SD) birth weight was 1034 (266) g vs 1022 (242) g.

INTERVENTIONS

Inspired oxygen was titrated by OxyGenie (SLE6000) or CLiO₂ (AVEA) during respiratory support.

MAIN OUTCOME MEASURES

Mortality, retinopathy of prematurity (ROP), bronchopulmonary dysplasia and necrotising enterocolitis.

RESULTS

Fewer infants in the OxyGenie group received laser coagulation for ROP (1 infant vs 10; risk ratio 0.1 (95% CI 0.0 to 0.7); p=0.008), and infants stayed shorter in the neonatal intensive care unit (NICU) (28 (95% CI 15 to 42) vs 40 (95% CI 25 to 61) days; median difference 13.5 days (95% CI 8.5 to 19.5); p<0.001). Infants in the OxyGenie group had fewer days on continuous positive airway pressure (8.4 (95% CI 4.8 to 19.8) days vs 16.7 (95% CI 6.3 to 31.1); p<0.001) and a significantly shorter days on invasive ventilation (0 (95% CI 0 to 4.2) days vs 2.1 (95% CI 0 to 8.4); p=0.012). There were no statistically significant differences in all other morbidities.

CONCLUSIONS

In this propensity score-matched retrospective study, the OxyGenie epoch was associated with less morbidity when compared with the CLiO₂ epoch. There were significantly fewer infants that received treatment for ROP, received less intensive respiratory support and, although there were more supplemental oxygen days, the duration of stay in the NICU was shorter. A larger study will have to replicate these findings.

Neurosensory Alterations in Retinopathy of Prematurity: A Window to Neurological Impairments Associated to Preterm Birth

Retinopathy of prematurity (ROP) is one of the main blinding diseases affecting preterm newborns and is classically considered a vascular disorder. The premature exposure to the extrauterine environment, which is hyperoxic in respect to the intrauterine environment, triggers a cascade of events leading to retinal ischemia which, in turn, makes the retina hypoxic thus setting off angiogenic processes. However, many children with a history of ROP show persistent vision impairment, and there is evidence of an association between ROP and neurosensory disabilities. This is not surprising given the strict relationship between neuronal function and an adequate blood supply. In the present work, we revised literature data evidencing to what extent ROP can be considered a neurodegenerative disease, also taking advantage from data obtained in preclinical models of ROP. The involvement of different retinal cell populations in triggering the neuronal damage in ROP was described along with the neurological outcomes associated to ROP. The situation of ROP in Italy was assessed as well.

Evaluation of the Retinopathy of Prematurity Activity Scale (ROP-ActS) in a randomised controlled trial aiming for prevention of severe ROP: a substudy of the Mega Donna Mega trial

Objective

The current grading of retinopathy of prematurity (ROP) does not sufficiently discriminate disease severity for evaluation of trial interventions. The published ROP Activity Scales (original: ROP-ActS and modified: mROP-ActS), describing increasing severity of ROP, versus the categorical variables severe ROP, stage, zone and plus disease were evaluated as discriminators of the effect of an ROP preventive treatment.

Methods and analysis

The Mega Donna Mega trial investigated ROP in infants born <28-week gestational age (GA), randomised to arachidonic acid (AA) and docosahexaenoic acid (DHA) supplementation or no supplementation. Of 207 infants, 86% with finalised ROP screening were included in this substudy. ROP-ActS versus standard variables were evaluated using Fisher's non-parametric permutation test, multivariable logistic and linear regression and marginal fractional response models.

Results

The AA:DHA group (n=84) and the control group (n=93) were well balanced. The maximum ROP-ActS measurement was numerically but not significantly lower in the AA:DHA group (mean: 4.0 (95% CI 2.9 to 5.0)) versus the control group (mean: 5.3 (95% CI 4.1 to 6.4)), p=0.11. In infants with any ROP, the corresponding scale measurements were 6.8 (95% CI 5.4 to 8.2) and 8.7 (95% CI 7.5 to 10.0), p=0.039. Longitudinal profiles of the scale were visually distinguished for the categories of sex and GA for the intervention versus control.

Conclusions

The preventive effect of AA:DHA supplementation versus no supplementation was better discriminated by the trial's primary outcome, severe ROP, than by ROP-ActS. The sensitivity and the linear qualities of ROP-ActS require further validations on large data sets and perhaps modifications.

Trial registration number

NCT03201588.

Prediction model to predict type 1 retinopathy of prematurity using gestational age and birth weight (PW-ROP)

PURPOSE

To develop a prediction model for type 1 retinopathy of prematurity (ROP) from an Asian population.

METHODS

This retrospective cohort study included 1043 premature infants who had ROP screening in a tertiary hospital in Hong Kong from year 2006 to 2018. The ROP prediction model was developed by multivariate logistic regression analyses on type 1 ROP. The cut-off value and the corresponding sensitivity and specificity were determined by receiver operating characteristic curve analysis. A validation group of 353 infants collected from another tertiary hospital in another region of Hong Kong from year 2014 to 2017 was used for external validation.

RESULTS

There were 1043 infants in the study group. The median gestational age (GA) was 30 weeks and 1 day and median birth weight (BW) was 1286 g. The prediction model required only GA and BW as parameters (prematurity-birth weight ROP (PW-ROP)). The area under curve value was 0.902. The sensitivity and specificity were 87.4% and 79.3%, respectively. Type 1 ROP developed in 0.9%, 17.4% and 50% of infants with PW-ROP scores<0, between 0 and <300, and ≥300 respectively (p<0.001). On external validation, our prediction model correctly predicted 95.8% of type 1 ROP (sensitivity=95.8%, specificity=74.8%) in the validation group.

CONCLUSION

The PW-ROP model is a simple model which could predict type 1 ROP with high sensitivity and specificity. Incorporating this model to ROP examination would help identify infants at risk for ROP treatment.

Decoupling Oxygen Tension From Retinal Vascularization as a New Perspective for Management of Retinopathy of Prematurity. New Opportunities From β-adrenoceptors

Retinopathy of prematurity (ROP) is an evolutive and potentially blinding eye disease that affects preterm newborns. Unfortunately, until now no conservative therapy of active ROP with proven efficacy is available. Although ROP is a multifactorial disease, premature exposition to oxygen concentrations higher than those intrauterine, represents the initial pathogenetic trigger. The increase of oxygenation in a retina still incompletely vascularized promotes the downregulation of proangiogenic factors and finally the interruption of vascularization (ischemic phase). However, the increasing metabolic requirement of the ischemic retina induces, over the following weeks, a progressive hypoxia that specularly increases the levels of proangiogenic factors finally leading to proliferative retinopathy (proliferative phase). Considering non-modifiable the coupling between oxygen levels and vascularization, so far, neonatologists and ophthalmologists have "played defense", meticulously searching the minimum necessary concentration of oxygen for individual newborns, refining their diagnostic ability, adopting a careful monitoring policy, ready to decisively intervene only in a very advanced stage of disease progression. However, recent advances have demonstrated the possibility to pharmacologically modulate the relationship between oxygen and vascularization, opening thus the perspective for new therapeutic or preventive opportunities. The perspective of a shift from a defensive towards an attack strategy is now at hand.

Comparison of two devices for automated oxygen control in preterm infants: a randomised crossover trial

OBJECTIVE

To compare the effect of two different automated oxygen control devices on target range (TR) time and occurrence of hypoxaemic and hyperoxaemic episodes.

DESIGN

Randomised cross-over study.

SETTING

Tertiary level neonatal unit in the Netherlands.

PATIENTS

Preterm infants (n=15) born between 24+0 and 29+6 days of gestation, receiving invasive or non-invasive respiratory support with oxygen saturation (SpO₂) TR of 91%-95%. Median gestational age 26 weeks and 4 days (IQR 25 weeks 3 days-27 weeks 6 days) and postnatal age 19 (IQR 17-24) days.

INTERVENTIONS

Inspired oxygen concentration was titrated by the OxyGenie controller (SLE6000 ventilator) and the CLiO₂ controller (AVEA ventilator) for 24 hours each, in a random sequence, with the respiratory support mode kept constant.

MAIN OUTCOME MEASURES

Time spent within set SpO₂ TR (91%-95% with supplemental oxygen and 91%-100% without supplemental oxygen).

RESULTS

Time spent within the SpO₂ TR was higher during OxyGenie control (80.2 (72.6-82.4)% vs 68.5 (56.7-79.3)%, p<0.005). Less time was spent above TR while in supplemental oxygen (6.3 (5.1-9.9)% vs 15.9 (11.5-30.7)%, p<0.005) but more time spent below TR during OxyGenie control (14.7 (11.8%-17.2%) vs 9.3 (8.2-12.6)%, p<0.05). There was no significant difference in time with SpO₂ <80% (0.5 (0.1-1.0)% vs 0.2 (0.1-0.4)%, p=0.061). Long-lasting SpO₂ deviations occurred less frequently during OxyGenie control.

CONCLUSIONS

The OxyGenie control algorithm was more effective in keeping the oxygen saturation within TR and preventing hyperoxaemia and equally effective in preventing hypoxaemia (SpO₂ <80%), although at the cost of a small increase in mild hypoxaemia.

TRIAL REGISTRY NUMBER

NCT03877198.

Inflammatory biomarkers in very preterm infants during early intravenous paracetamol administration

BACKGROUND

Paracetamol promotes early closure of patent ductus arteriosus (PDA), and it may affect inflammation after preterm birth.

OBJECTIVE

The aim of this study was to evaluate the association between paracetamol treatment and serum inflammatory biomarkers in very preterm infants with respiratory distress.

STUDY DESIGN

The infants were randomly assigned to intravenous paracetamol or placebo during the first 4 days of life, and others received a lower dose of paracetamol unblinded. Serum samples were used for the analysis of 10 cytokines, C-reactive protein (CRP) and malondialdehyde (MDA). The impact of paracetamol on the biomarkers was evaluated, based on the levels during the early (<60 h) and the later (60-120 h) postnatal age.

RESULTS

Altogether, 296 serum samples from 31 paracetamol and 25 placebo group infants were analysed. Paracetamol had no effect on cytokine levels during the first 60 h when most induced PDA contractions took place. Later paracetamol treatment was associated with lower serum levels of several cytokines, including interleukin (IL-) 10, interferon gamma-induced protein (IP-) 10, and monocyte chemoattractant protein-1. CRP levels were lower in the paracetamol group during the early treatment. Amongst the infants who had severe morbidities, MDA was higher (p = .045), regardless of paracetamol treatment.

CONCLUSION

No significant differences in the cytokine levels were evident between the treatment and placebo groups. However, during early treatment, CRP levels were lower in the paracetamol group. To clarify whether this was due to a decrease in cardiopulmonary distress, or a distinct anti-inflammatory effect, requires further studies.

Eph Receptors and Ephrins in Retinal Diseases

Retinal diseases are the leading cause of irreversible blindness. They affect people of all ages, from newborns in retinopathy of prematurity, through age-independent diabetic retinopathy and complications of retinal detachment, to age-related macular degeneration (AMD), which occurs mainly in the elderly. Generally speaking, the causes of all problems are disturbances in blood supply, hypoxia, the formation of abnormal blood vessels, and fibrosis. Although the detailed mechanisms underlying them are varied, the common point is the involvement of Eph receptors and ephrins in their pathogenesis. In our study, we briefly discussed the pathophysiology of the most common retinal diseases (diabetic retinopathy, retinopathy of prematurity, proliferative vitreoretinopathy, and choroidal neovascularization) and collected available research results on the role of Eph and ephrins. We also discussed the safety aspect of the use of drugs acting on Eph and ephrin for ophthalmic indications.

Concurrent Physiological and Pathological Angiogenesis in Retinopathy of Prematurity and Emerging Therapies

Retinopathy of prematurity (ROP) is an ocular vascular disease affecting premature infants, characterized by pathological retinal neovascularization (RNV), dilated and tortuous retinal blood vessels, and retinal or vitreous hemorrhages that may lead to retinal detachment, vision impairment and blindness. Compared with other neovascular diseases, ROP is unique because of ongoing and concurrent physiological and pathological angiogenesis in the developing retina. While the disease is currently treated by laser or cryotherapy, anti-vascular endothelial growth factor (VEGF) agents have been extensively investigated but are not approved in the U.S. because of safety concerns that they negatively interfere with physiological angiogenesis of the developing retina. An ideal therapeutic strategy would selectively inhibit pathological but not physiological angiogenesis. Our group recently described a novel strategy that selectively and safely alleviates pathological RNV in animal models of ROP by targeting secretogranin III (Scg3), a disease-restricted angiogenic factor. The preclinical profile of anti-Scg3 therapy presents a high potential for next-generation disease-targeted anti-angiogenic therapy for the ROP indication. This review focuses on retinal vessel development in neonates, the pathogenesis of ROP and its underlying molecular mechanisms, including different animal models, and provides a summary of current and emerging therapies.

The Nrf2 inhibitor brusatol has a protective role in a rat model of oxygen-induced retinopathy of prematurity

Nuclear factor-erythroid 2-related factor 2 (Nrf2) has been testified to be involved in the development of retinopathy of prematurity (ROP), which can cause childhood visual impairment. Whether brusatol, an Nrf2 inhibitor, could be utilized to treat ROP was unknown. The oxygen-induced retinopathy rat model was established to mimic ROP, which was further intravitreal administrated with brusatol. Vessel morphology and microglial activation in the retina were assessed with histology analysis. The relative expression levels of angiogenesis and inflammation-related molecules were detected with Western blot and real-time polymerase chain reaction methods. Intravitreal brusatol administration could alleviate both angiogenesis and microgliosis induced by hyperoxia, along with down-regulation of vascular endothelial growth factor, vascular endothelial growth factor receptor (VEGFR)-1, VEGFR-2, cluster of differentiation molecule 11B, tumor necrosis factor alpha, inducible nitric oxide synthase, glial fibrillary acidic protein, and IBA-1 expression. It was further revealed that Nrf2 and heme oxygenease-1 were diminished by brusatol administration. The results demonstrate the potential of intravitreal brusatol deliver to treat ROP with down-regulation of angiogenesis and microgliosis.

Incidence and risk factors of retinopathy of prematurity in an Italian cohort of preterm infants

OBJECTIVE

Non-negligible differences in retinopathy of prematurity (ROP) and its risk factors between different neonatal intensive care units (NICUs) are reported. Our aim was to assess the incidence and risk factors for ROP development in a large cohort of very preterm infants who were assisted in two Italian NICUs.

METHODS

Preterm infants with gestational age between 23+ 0 and 29+ 6 weeks were stratified into subgroups of infants who developed ROP and those who did not; their clinical characteristics were compared with univariate and multivariable logistic regression analyses.

RESULTS

We studied a total of 178 infants of whom 67 (38%) developed ROP (stage 1: n = 12; stage 2: n = 41; stage 3: n = 14). Regression analysis demonstrated that maternal milk (OR 0.979, 95% Cl 0.961-0.998) decreased the risk of developing ROP, while intraventricular hemorrhage (IVH) (OR 2.055, 95% Cl 1.120-3.772) increased it. Moreover, maternal milk was found to decrease (OR 0.981, 95% Cl 0.964-0.997) the risk of ROP at discharge, while RBC transfusion increased it (OR 1.522, 95% Cl 1.208-1.916).

CONCLUSIONS

In our cohort the occurrence of ROP was similar to that previously reported. Strategies for promoting the use of mother's own milk, preventing IVH, and standardizing the approach to RBC transfusions could contribute to decreasing the risk of ROP in very preterm infants.

The effect of automated oxygen control on clinical outcomes in preterm infants: a pre- and post-implementation cohort study

Several studies demonstrated an increase in time spent within target range when automated oxygen control (AOC) is used. However the effect on clinical outcome remains unclear. We compared clinical outcomes of preterm infants born before and after implementation of AOC as standard of care. In a retrospective pre-post implementation cohort study of outcomes for infants of 24-29 weeks gestational age receiving respiratory support before (2012-2015) and after (2015-2018) implementation of AOC as standard of care were compared. Outcomes of interest were mortality and complications of prematurity, number of ventilation days, and length of stay in the Neonatal Intensive Care Unit (NICU). A total of 588 infants were included (293 pre- vs 295 in the post-implementation cohort), with similar gestational age (27.8 weeks pre- vs 27.6 weeks post-implementation), birth weight (1033 grams vs 1035 grams) and other baseline characteristics. Mortality and rate of prematurity complications were not different between the groups. Length of stay in NICU was not different, but duration of invasive ventilation was shorter in infants who received AOC (6.4 ± 10.1 vs 4.7 ± 8.3, p = 0.029).Conclusion: In this pre-post comparison, the implementation of AOC did not lead to a change in mortality or morbidity during admission. What is Known: • Prolonged and intermittent oxygen saturation deviations are associated with mortality and prematurity-related morbidities. • Automated oxygen controllers can increase the time spent within oxygen saturation target range. What is New: • Implementation of automated oxygen control as standard of care did not lead to a change in mortality or morbidity during admission. • In the period after implementation of automated oxygen control, there was a shift toward more non-invasive ventilation.

G-protein coupled estrogen receptor activation protects the viability of hyperoxia-treated primary murine retinal microglia by reducing ER stress

In this study, we investigated the effects of G-protein coupled estrogen receptor (GPER) activation in the early phase of retinopathy of prematurity (ROP) and its association with endoplasmic reticulum (ER) stress using primary murine retinal microglia as an experimental model. Fluorescence microscopy results show that the CD11c-positive primary retinal microglia in vitro cultured for 14 days were GPER-positive. GPER activation using GPER-agonist G-1 reduced autophagy and increased the viability of the hyperoxia-treated primary murine retinal microglia. Furthermore, GPER activation reduced the expression of ER stress-related proteins, IRE1α, PERK and ATF6 in the hyperoxia-treated primary murine retinal microglia compared to the corresponding controls. GPER activation significantly reduced a time-dependent increase in IP3R-dependent calcium release from the ER, thereby maintaining higher calcium levels in the ER of hyperoxia-treated primary retinal microglia. However, the protective effects of G-1 on the hyperoxia-treated primary retinal microglia were eliminated by inactivation of GPER using the GPER-antagonist, G-15. In conclusion, our study demonstrates that GPER activation enhances the survival of hyperoxia-treated primary retinal microglia by reducing ER stress. Our study demonstrates the therapeutic potential of GPER agonists such as G-1 in the early phase of ROP.