[Early administration of erythropoietin in the extreme premature, a risk factor for retinopathy of prematurity?]

Effect of red blood cell transfusion on the development of retinopathy of prematurity: A systematic review and meta-analysis

BACKGROUND

The effect of red blood cell (RBC) transfusion on retinopathy of prematurity (ROP) is difficult to establish, because ROP may also be influenced by other factors. Therefore, we carried out a systematic review and meta-analysis to explore the relationship between RBC transfusion and the development of ROP.

METHODS

The PubMed, Embase, Cochrane Library and Web of Science databases were searched from their inception to September 1, 2019. Observational studies that reported the relationship between RBC transfusion and ROP after adjusting for other potential risk factors were included. The combined result was analyzed by a random effect model. Heterogeneity and publication bias were tested, and sensitivity analysis was performed.

RESULTS

Of the 2628 identified records, 18 studies including 15072 preterm infants and 5620 cases of ROP were included. A random effect model was used and revealed that RBC transfusion was significantly associated with ROP (pooled OR = 1.50, 95% CI: 1.27-1.76), with moderate heterogeneity among the included studies (I2 = 44.2%). Subgroup analysis indicated that RBC transfusion was more closely related to ROP in the group with a gestational age (GA) ≤32 weeks (OR = 1.77, 95% CI: 1.29-2.43) but not in the groups with a GA ≤34 weeks (OR = 1.36, 95% CI: 0.85-2.18) or a GA <37 weeks (OR = 1.25, 95% CI: 0.86-1.82). No obvious publication bias was found based on the funnel plot and Egger's test. Removing any single study did not significantly alter the combined result in the sensitivity analysis.

CONCLUSIONS

Our study revealed that RBC transfusion is an independent risk factor for the development of ROP, especially in younger preterm infants. However, there seemed to be no evidence to support an effect of RBC transfusion on ROP in older groups. Further studies addressing this issue in older preterm neonates are warranted.

Intravitreal Delivery of VEGF-A165-loaded PLGA Microparticles Reduces Retinal Vaso-Obliteration in an In Vivo Mouse Model of Retinopathy of Prematurity

PURPOSE

Retinopathy of prematurity (ROP) is a condition of abnormal retinal vascularization with reduced levels of vascular endothelial growth factor (VEGF) causing vaso-obliteration (Phase I), followed by abnormal neovascularization from increased VEGF (Phase II). We hypothesized that intravitreal pro-angiogenic VEGF-A in microparticle form would promote earlier retinal revascularization in an oxygen-induced ischemic retinopathy (OIR) mouse model.

MATERIALS AND METHODS

Wildtype mice (39) were exposed to 77% oxygen from postnatal day 7 (P7) to P12. VEGF-A₁₆₅-loaded poly(lactic-co-glycolic acid) (PLGA) (n = 15) or empty PLGA (n = 14) microparticles were fabricated using a water-in-oil-in-water double emulsion method, and injected intravitreally at P13 into mice right eyes (RE). Left eyes (LE) were untreated. At P20, after retinal fluorescein angiography, vascular parameters were quantified. Retinal VEGF levels at P13 and flatmounts at P20 were performed separately.

RESULTS

VEGF-A₁₆₅-loaded microparticles had a mean diameter of 4.2 μm. with a loading level of 8.6 weight.%. Retinal avascular area was reduced in VEGF-treated RE (39.5 ± 9.0%) compared to untreated LE (52.6 ± 6.1%, p < 0.0001) or empty microparticle-treated RE (p < 0.001) and untreated LEs (p = 0.001). Retinal arteries in VEGF-treated RE were less tortuous than untreated LE (1.08 ± 0.05 vs. 1.18 ± 0.08, p < 0.001) or empty-microparticles-treated RE (p = 0.02). Retinal arterial tortuosity was similar in the LE of VEGF and empty microparticle-treated mice (P > 0.05). Retinal vein width was similar in VEGF-treated and empty microparticle-treated RE (P > 0.9), which were each less dilated than their contralateral LE (p < 0.01). VEGF levels were higher in P13 OIR mice than RA mice (p < 0.0001). Retinal flatmounts showed vaso-obliteration and neovascularization.

CONCLUSIONS

Endogenous retinal VEGF is suppressed in OIR mice. Exogenous intravitreal VEGF-A₁₆₅-loaded microparticles in OIR mice reduced retinal vaso-obliteration and accelerated recovery from vein dilation and arterial tortuosity. This may be beneficial in preventing Phase II ROP without systemic effects.

The progress of prophylactic treatment in retinopathy of prematurity

Retinopathy of prematurity (ROP) is a retinal vascular disorder frequently found in premature infants. Different therapeutic strategies have been developed to treat ROP. However, there are still many children with ROP suffering by severe limitations in vision or even blindness. Recently, ROP has been suggested to be caused by abnormal development of the retinal vasculature, but not simply resulted by retinal neovascularization which takes about 4 to 6wk after birth in premature infants. Thus, instead of focusing on how to reduce retinal neovascularization, understanding the pathological changes and mechanisms that occur prior to retinal neovascularization is meaningful, which may lead to identify novel target(s) for the development of novel strategy to promote the healthy growth of retinal blood vessels rather than passively waiting for the appearance of retinal neovascularization and removing it by force. In this review, we discussed recent studies about, 1) the pathogenesis prior to retinal neovascularization in oxygen-induced retinopathy (OIR; a ROP in animal model) and in premature infants with ROP; 2) the preclinical and clinical research on preventive treatment of early OIR and ROP. We will not only highlight the importance of the mechanisms and signalling pathways in regulating early stage of ROP but also will provide guidance for actively exploring novel mechanisms and discovering novel treatments for early phase OIR and ROP prior to retinal neovascularization in the future.

Retinopathy of prematurity: a review of risk factors and their clinical significance

Retinopathy of prematurity (ROP) is a retinal vasoproliferative disease that affects premature infants. Despite improvements in neonatal care and management guidelines, ROP remains a leading cause of childhood blindness worldwide. Current screening guidelines are primarily based on two risk factors: birth weight and gestational age; however, many investigators have suggested other risk factors, including maternal factors, prenatal and perinatal factors, demographics, medical interventions, comorbidities of prematurity, nutrition, and genetic factors. We review the existing literature addressing various possible ROP risk factors. Although there have been contradictory reports, and the risk may vary between different populations, understanding ROP risk factors is essential to develop predictive models, to gain insights into pathophysiology of retinal vascular diseases and diseases of prematurity, and to determine future directions in management of and research in ROP.

Early Erythropoietin Administration does not Increase the Risk of Retinopathy in Preterm Infants

BACKGROUND

Erythropoietin (EPO) administration prevents anemia of prematurity and may be associated with a significant increase in the risk of retinopathy of prematurity (ROP) in preterm infants. Nonetheless, early EPO treatment may prevent damage following retinal neovascularization. The aim of this meta-analysis was to elucidate whether EPO administration increases the risk of ROP.

METHODS

We searched MEDLINE, PubMed, CINAHL (Cumulative Index to Nursing and Allied Health Literature), and the Cochrane Central Register of Controlled Trials with no language restrictions. Randomized controlled trials that reported the association between EPO treatment in preterm infants and ROP were eligible. All of the included studies were stratified into two groups according to the age of initiation of EPO treatment: before 8 days of age (early EPO), and 8-28 days of age (late EPO).

RESULTS

Thirteen studies were identified that included a total of 1999 preterm infants. EPO administration did not increase the risk of ROP of any stage or Stage ≥3 (any relative risk: 0.99, 95% confidence interval: 0.84-1.16, p = 0.89; Stage ≥3 relative risk: 1.34, 95% confidence interval: 0.90-1.99, p = 0.15). This trend remained unchanged in both the early and late EPO groups. There did not seem to be any evidence of publication bias for outcomes as the funnel plots were symmetrical.

CONCLUSION

EPO administration did not significantly increase the risk of ROP of any stage reported or Stage ≥3. Further clinical trials investigating the impact of EPO on ROP in premature infants should include all confounding factors to clarify this important issue.

Pharmacologic interventions for the prevention and treatment of retinopathy of prematurity

Retinopathy of prematurity (ROP), a significant morbidity in prematurely born infants, is the most common cause of visual impairment and blindness in children and persists till adulthood. Strict control of oxygen therapy and prevention of intermittent hypoxia are the keys in the prevention of ROP, but pharmacologic interventions have decreased risk of ROP. Various drug classes such as methylxanthines (caffeine), VEGF inhibitors, antioxidants, and others have decreased ROP occurrence. The timing of pharmacologic intervention remains unsettled, but early prevention rather than controlling disease progression may be preferred. These drugs act through different mechanisms, and synergistic approaches should be considered to maximize efficacy and safety.

Erythropoietin and retinopathy of prematurity: a meta-analysis

We performed a meta-analysis to study the association between erythropoietin (EPO) and the development of retinopathy of prematurity (ROP) in preterm newborn infants. Studies were identified through PubMed (1966-) and ISI databases (1965-) literature searches. Results and effect sizes are expressed as odds ratio (OR) with 95 % confidence intervals (CI). Fourteen studies identified to the meta-analysis, including 3,484 preterm newborn infants. A total of 563 of 1,221 babies treated with EPO had ROP (46.1 %) vs. 420 of 1,134 babies without EPO (37.0 %). No significant difference was found in the ROP risk between the two groups, with the OR 1.592 (95 % CI 0.901-2.812). A total of 192 of 1,298 babies treated with EPO had severe ROP (stage 3-4) (14.8 %) vs. 166 of 1,199 babies without EPO (13.8 %). The OR was 1.203 (95 % CI 0.763-1.896). No significant publication bias was found. Sensitivity analyses showed the results were robust.

CONCLUSION

Our meta-analysis indicates that EPO treatment is not associated with the development of ROP in preterm infants. But this conclusion should be confirmed by further high-quality researches.

Erythropoietin promotes retinal angiogenesis in a mouse model

This study aimed to investigate the effect and potential mechanisms of exogenous administration of recombinant human erythropoietin (rhEPO) on retinal angiogenesis in a mouse model of oxygen-induced retinopathy (OIR). Postnatal day 7 (P7) mice (n=132) were randomly assigned to one of six groups: Control group (n=22), OIR group (n=22), OIR + vehicle control group (n=22), OIR + rhEPO 10 IU group (n=22), OIR + rhEPO 50 IU group (n=22), and OIR + rhEPO 100 IU group (n=22). OIR was induced by exposing mice to 75±2% O2 for five days, followed by exposure to room air for a further five days. Animals in groups 3-6 (the OIR + vehicle control group and OIR + rhEPO 10 IU, 50 IU, and 100 IU groups) received an intraperitoneal injection of saline, or rhEPO 10 IU, 50 IU and 100 IU, respectively, which were administered daily from P7-P12. Immunofluorescent and hematoxylin-eosin staining were used to detect retinal neovascularization (RNV) in retinal whole mounts. Quantitative polymerase chain reaction and western blot analysis were used to detect the expression levels of vascular endothelial growth factor (VEGF), endothelial nitric oxide synthase (eNOS), and neuronal nitric oxide synthase (nNOS). RNV occurred in the OIR groups and was accompanied by dilated, twisted and occluded blood vessels. rhEPO treatment resulted in an increase in the number of newly formed and severely dilated vessels. rhEPO increased RNV in a dose-dependent manner, which was accompanied by an increase in the messenger RNA and protein expression of VEGF, eNOS and nNOS. Thus, exogenous use of rhEPO promotes the RNV in a mouse model of OIR and is accompanied by increased expression levels of VEGF, eNOS and nNOS.

The pathophysiology of retinopathy of prematurity: an update of previous and recent knowledge

Retinopathy of prematurity (ROP) is a disease that can cause blindness in very low birthweight infants. The incidence of ROP is closely correlated with the weight and the gestational age at birth. Despite current therapies, ROP continues to be a highly debilitating disease. Our advancing knowledge of the pathogenesis of ROP has encouraged investigations into new antivasculogenic therapies. The purpose of this article is to review the findings on the pathophysiological mechanisms that contribute to the transition between the first and second phases of ROP and to investigate new potential therapies. Oxygen has been well characterized for the key role that it plays in retinal neoangiogenesis. Low or high levels of pO2 regulate the normal or abnormal production of hypoxia-inducible factor 1 and vascular endothelial growth factors (VEGF), which are the predominant regulators of retinal angiogenesis. Although low oxygen saturation appears to reduce the risk of severe ROP when carefully controlled within the first few weeks of life, the optimal level of saturation still remains uncertain. IGF-1 and Epo are fundamentally required during both phases of ROP, as alterations in their protein levels can modulate disease progression. Therefore, rhIGF-1 and rhEpo were tested for their abilities to prevent the loss of vasculature during the first phase of ROP, whereas anti-VEGF drugs were tested during the second phase. At present, previous hypotheses concerning ROP should be amended with new pathogenetic theories. Studies on the role of genetic components, nitric oxide, adenosine, apelin and β-adrenergic receptor have revealed new possibilities for the treatment of ROP. The genetic hypothesis that single-nucleotide polymorphisms within the β-ARs play an active role in the pathogenesis of ROP suggests the concept of disease prevention using β-blockers. In conclusion, all factors that can mediate the progression from the avascular to the proliferative phase might have significant implications for the further understanding and treatment of ROP.