Decreased Platelet Counts and Serum Levels of VEGF-A, PDGF-BB, and BDNF in Extremely Preterm Infants Developing Severe ROP

Circulating VEGF-A Levels in Relation to Retinopathy of Prematurity and Treatment Effects: A Systematic Review and Meta-Analysis

Topic

Retinopathy of prematurity (ROP) is a severe retinal vascular disorder affecting preterm infants, potentially leading to retinal detachment and blindness. This review aims to elucidate the relationship between systemic VEGF levels and ROP.

Clinical Relevance

This systematic review aims to consolidate evidence from available studies to guide future research and inform clinical practice. In particular, the role of circulating VEGF-A levels in predicting ROP onset and progression, and evaluating the impact of anti-VEGF therapy on these levels, is crucial in ensuring efficacy and safety in patient care.

Methods

Scopus and PubMed were searched to identify studies investigating circulating VEGF-gene products in ROP patients using immunologic assays. Two authors independently screened the literature and extracted data, employing a random-effects meta-analysis to compare VEGF levels as the ratio of means between ROP patients and controls before and after treatment, heterogeneity was reported by I2-statistics. Risks of bias and publication bias were assessed using Quality Assessment of Diagnostic Accuracy Studies-2 and funnel plots/Egger's tests, respectively.

Results

Out of 941 papers, 54 were included, with 26 providing posttreatment data and 31 providing biomarker data. Findings show a significant decrease in VEGF-A levels in the first week after ROP treatment (ratio of means [95% confidence interval] 0.34 [0.25-0.45], I2 = 97%, 17 publications). Anti-VEGF therapy showed a significantly more pronounced decrease (0.31 [0.25-0.38], I2 = 40%, 7 publications) than laser treatment in the first week after treatment (0.77 [0.61-0.97], I2 = 42%, 2 publications, subgroup difference, P < 0.01), among studies with a low risk of bias. Serum samples demonstrated a more marked decrease in VEGF-A than plasma (subgroup difference P < 0.01). However, the use of blood VEGF-A concentration as a biomarker for ROP prediction has shown inconsistent trends. The risk of bias mainly stems from unclear patient selection and lack of sample timing or analytical method details.

Conclusion

While anti-VEGF treatment significantly reduced blood VEGF-A levels in the first week post-ROP treatment, blood VEGF-A levels did not consistently predict ROP development. Heterogeneity in the results underscores the need for optimized analytical methods and emphasizes the importance of considering individual variation in VEGF-A concentrations independent of ROP diagnosis.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Biomarkers in retinopathy of prematurity: a systematic review and meta-analysis

Aim

Retinopathy of prematurity is a significant global cause of childhood blindness. This study aims to identify serum biomarkers that are associated with the development of ROP.

Methods

A systematic review and meta-analysis was conducted using PRISMA guidelines. Three databases were searched (Pubmed, Scopus and Web of Science) from 2003 to March 2023. Only studies investigating serum biomarker levels in preterm infants (<37 weeks gestation) were included.

Results

Meta-analysis suggests that low serum IGF-1 levels have a strong association with the development of ROP [SMD (95% CI) of -.46 [-.63, -.30], p < .001]. Meta-analysis suggests that higher serum glucose levels were associated with the development of ROP [SMD (95% CI) of 1.25 [.94, 1.55], p < .001]. Meta-analysis suggests that thrombocytopenia is associated with the development of ROP [SMD (95% CI) of -.62 [-.86, -.37], p < .001].

Conclusion

Low levels of serum IGF-1, high levels of serum glucose and thrombocytopenia all appear to have the strongest association with the development of ROP out of the 63 biomarkers investigated in this review. These associations highlight their potential use as diagnostic biomarkers in ROP, though further research is needed to establish the exact relationship between these biomarkers and disease pathogenesis.

Platelet Counts and Risk of Severe Retinopathy of Prematurity: A Bayesian Model-Averaged Meta-Analysis

BACKGROUND

We aimed to conduct a systematic review and Bayesian model-averaged meta-analysis (BMA) on the association between platelet counts and severe retinopathy of prematurity (ROP).

METHODS

We searched for studies reporting on platelet counts (continuous variable) or thrombocytopenia (categorical variable) and severe ROP or aggressive posterior ROP (APROP). The timing of platelet counts was divided into Phase 1 (<2 weeks) and Phase 2 (around ROP treatment). BMA was used to calculate Bayes factors (BFs). The BF10 is the ratio of the probability of the data under the alternative hypothesis (H1) over the probability of the data under the null hypothesis (H0).

RESULTS

We included 21 studies. BMA showed an association between low platelet counts and severe ROP. The evidence was strong (BF10 = 13.5, 7 studies) for phase 1 and very strong (BF10 = 51.0, 9 studies) for phase 2. Thrombocytopenia (<100 × 109/L) in phase 2 was associated with severe ROP (BF10 = 28.2, 4 studies). Following adjustment for publication bias, only the association of severe ROP with thrombocytopenia remained with moderate evidence in favor of H1 (BF10 = 4.30).

CONCLUSIONS

Thrombocytopenia is associated with severe ROP. However, the evidence for this association was tempered when results were adjusted for publication bias.

Complete blood count parameters as biomarkers of retinopathy of prematurity: a Portuguese multicenter study

PURPOSE

To evaluate complete blood count (CBC) parameters in the first week of life as predictive biomarkers for the development of retinopathy of prematurity (ROP).

METHODS

Multicenter, prospective, observational study of a cohort of preterm infants born with gestational age (GA) < 32 weeks or birth weight < 1500 g in eight Portuguese neonatal intensive care units. All demographic, clinical, and laboratory data from the first week of life were collected. Univariate logistic regression was used to assess risk factors for ROP and then multivariate regression was performed.

RESULTS

A total of 455 infants were included in the study. The median GA was 29.6 weeks, and the median birth weight was 1295 g. One hundred and seventy-two infants (37.8%) developed ROP. Median values of erythrocytes (p < 0.001), hemoglobin (p < 0.001), hematocrit (p < 0.001), mean corpuscular hemoglobin concentration (p < 0.001), lymphocytes (p = 0.035), and platelets (p = 0.003) of the group of infants diagnosed with ROP any stage were lower than those without ROP. Mean corpuscular volume (MCV) (p = 0.044), red blood cell distribution width (RDW) (p < 0.001), erythroblasts (p < 0.001), neutrophils (p = 0.030), neutrophils-lymphocytes ratio (p = 0.028), and basophils (p = 0.003) were higher in the ROP group. Higher values of MCV, erythroblasts, and basophils remained significantly associated with ROP after multivariate regression.

CONCLUSION

In our cohort, the increase in erythroblasts, MCV, and basophils in the first week of life was significantly and independently associated with the development of ROP. These CBC parameters may be early predictive biomarkers for ROP.

Retinopathy of prematurity: A review of pathophysiology and signaling pathways

Retinopathy of prematurity (ROP) is a vasoproliferative disorder of the retina and a leading cause of visual impairment and childhood blindness worldwide. The disease is characterized by an early stage of retinal microvascular degeneration, followed by neovascularization that can lead to subsequent retinal detachment and permanent visual loss. Several factors play a key role during the different pathological stages of the disease. Oxidative and nitrosative stress and inflammatory processes are important contributors to the early stage of ROP. Nitric oxide synthase and arginase play important roles in ischemia/reperfusion-induced neurovascular degeneration. Destructive neovascularization is driven by mediators of the hypoxia-inducible factor pathway, such as vascular endothelial growth factor and metabolic factors (succinate). The extracellular matrix is involved in hypoxia-induced retinal neovascularization. Vasorepulsive molecules (semaphorin 3A) intervene preventing the revascularization of the avascular zone. This review focuses on current concepts about signaling pathways and their mediators, involved in the pathogenesis of ROP, highlighting new potentially preventive and therapeutic modalities. A better understanding of the intricate molecular mechanisms underlying the pathogenesis of ROP should allow the development of more effective and targeted therapeutic agents to reduce aberrant vasoproliferation and facilitate physiological retinal vascular development.

Systemic Cytokines in Retinopathy of Prematurity

Retinopathy of prematurity (ROP), a vasoproliferative vitreoretinal disorder, is the leading cause of childhood blindness worldwide. Although angiogenic pathways have been the main focus, cytokine-mediated inflammation is also involved in ROP etiology. Herein, we illustrate the characteristics and actions of all cytokines involved in ROP pathogenesis. The two-phase (vaso-obliteration followed by vasoproliferation) theory outlines the evaluation of cytokines in a time-dependent manner. Levels of cytokines may even differ between the blood and the vitreous. Data from animal models of oxygen-induced retinopathy are also valuable. Although conventional cryotherapy and laser photocoagulation are well established and anti-vascular endothelial growth factor agents are available, less destructive novel therapeutics that can precisely target the signaling pathways are required. Linking the cytokines involved in ROP to other maternal and neonatal diseases and conditions provides insights into the management of ROP. Suppressing disordered retinal angiogenesis via the modulation of hypoxia-inducible factor, supplementation of insulin-like growth factor (IGF)-1/IGF-binding protein 3 complex, erythropoietin, and its derivatives, polyunsaturated fatty acids, and inhibition of secretogranin III have attracted the attention of researchers. Recently, gut microbiota modulation, non-coding RNAs, and gene therapies have shown promise in regulating ROP. These emerging therapeutics can be used to treat preterm infants with ROP.

Postnatal serum IGF-1 levels associate with brain volumes at term in extremely preterm infants

BACKGROUND

Growth factors important for normal brain development are low in preterm infants. This study investigated the link between growth factors and preterm brain volumes at term.

MATERIAL/METHODS

Infants born <28 weeks gestational age (GA) were included. Endogenous levels of insulin-like growth factor (IGF)-1, brain-derived growth factor, vascular endothelial growth factor, and platelet-derived growth factor (expressed as area under the curve [AUC] for serum samples from postnatal days 1, 7, 14, and 28) were utilized in a multivariable linear regression model. Brain volumes were determined by magnetic resonance imaging (MRI) at term equivalent age.

RESULTS

In total, 49 infants (median [range] GA 25.4 [22.9-27.9] weeks) were included following MRI segmentation quality assessment and AUC calculation. IGF-1 levels were independently positively associated with the total brain (p < 0.001, β = 0.90), white matter (p = 0.007, β = 0.33), cortical gray matter (p = 0.002, β = 0.43), deep gray matter (p = 0.008, β = 0.05), and cerebellar (p = 0.006, β = 0.08) volume adjusted for GA at birth and postmenstrual age at MRI. No associations were seen for other growth factors.

CONCLUSIONS

Endogenous exposure to IGF-1 during the first 4 weeks of life was associated with total and regional brain volumes at term. Optimizing levels of IGF-1 might improve brain growth in extremely preterm infants.

IMPACT

High serum levels of insulin-like growth factor (IGF)-1 during the first month of life were independently associated with increased total brain volume, white matter, gray matter, and cerebellar volume at term equivalent age in extremely preterm infants. IGF-1 is a critical regulator of neurodevelopment and postnatal levels are low in preterm infants. The effects of IGF-1 levels on brain development in extremely preterm infants are not fully understood. Optimizing levels of IGF-1 may benefit early brain growth in extremely preterm infants. The effects of systemically administered IGF-1/IGFBP3 in extremely preterm infants are now being investigated in a randomized controlled trial (Clinicaltrials.gov: NCT03253263).

Language Impairment in Children of Mothers with Gestational Diabetes, Preeclampsia, and Preterm Delivery: Current Hypothesis and Potential Underlying Mechanisms : Language Impartment and Pregnancy Complications

Many conditions may impair or delay language development, including socioeconomic status, parent's education, or intrauterine environment. Accordingly, increasing evidence has described that pregnancy complications, including gestational diabetes mellitus (GDM), preeclampsia, and preterm delivery, are associated with the offspring's impaired neurodevelopment. Since language is one of the high brain functions, alterations in this function are another sign of neurodevelopment impairment. How these maternal conditions may generate language impairment has yet to be entirely understood. However, since language development requires adequate structural formation and function/connectivity of the brain, these processes must be affected by alterations in maternal conditions. However, the underlying mechanisms of these structural alterations are largely unknown. This manuscript critically analyzes the literature focused on the risk of developing language impairment in children of mothers with GDM, preeclampsia, and preterm delivery. Furthermore, we highlight potential underlying molecular mechanisms associated with these alterations, such as neuroinflammatory and metabolic and cerebrovascular alterations.

Retinopathy of prematurity: Metabolic risk factors

At preterm birth, the retina is incompletely vascularized. Retinopathy of prematurity (ROP) is initiated by the postnatal suppression of physiological retinal vascular development that would normally occur in utero. As the neural retina slowly matures, increasing metabolic demand including in the peripheral avascular retina, leads to signals for compensatory but pathological neovascularization. Currently, only late neovascular ROP is treated. ROP could be prevented by promoting normal vascular growth. Early perinatal metabolic dysregulation is a strong but understudied risk factor for ROP and other long-term sequelae of preterm birth. We will discuss the metabolic and oxygen needs of retina, current treatments, and potential interventions to promote normal vessel growth including control of postnatal hyperglycemia, dyslipidemia and hyperoxia-induced retinal metabolic alterations. Early supplementation of missing nutrients and growth factors and control of supplemental oxygen promotes physiological retinal development. We will discuss the current knowledge gap in retinal metabolism after preterm birth.

Association of platelet deficiency with severe retinopathy of prematurity: a review

AIM

The aim of this review was to compile existing evidence on the role of platelets in the development of severe retinopathy of prematurity (ROP), highlight the strengths and weaknesses of the available studies and critically discuss the reported data.

METHODS

A comprehensive literature search was conducted on PubMed from January 2000 to January 2022, and the reference lists of the included studies were screened manually.

RESULTS

There were 19 primary studies that fulfilled the eligibility criteria. Experimental research indicated lower platelet count in mice oxygen-induced retinopathy model compared with normoxia controls, while platelet transfusions suppressed neovascularisation. The latter finding was not consistently confirmed in clinical research, where a low platelet count, an increased number of thrombopenic episodes and of platelet transfusions have all been implicated in the development of ROP requiring treatment, either type I or aggressive posterior or both. However, existing studies exhibit significant clinical heterogeneity and present methodological limitations that imperil their reliability and validity.

CONCLUSION

Platelet deficiency has been associated with severe ROP. However, critical thresholds of platelet parameters are still unrecognised. Future research is required to determine whether platelet parameters can be predictive biomarkers for ROP requiring treatment and at what thresholds.

Omega-3/Omega-6 Long-Chain Fatty Acid Imbalance in Phase I Retinopathy of Prematurity

There is a gap in understanding the effect of the essential ω-3 and ω-6 long-chain polyunsaturated fatty acids (LCPUFA) on Phase I retinopathy of prematurity (ROP), which precipitates proliferative ROP. Postnatal hyperglycemia contributes to Phase I ROP by delaying retinal vascularization. In mouse neonates with hyperglycemia-associated Phase I retinopathy, dietary ω-3 (vs. ω-6 LCPUFA) supplementation promoted retinal vessel development. However, ω-6 (vs. ω-3 LCPUFA) was also developmentally essential, promoting neuronal growth and metabolism as suggested by a strong metabolic shift in almost all types of retinal neuronal and glial cells identified with single-cell transcriptomics. Loss of adiponectin (APN) in mice (mimicking the low APN levels in Phase I ROP) decreased LCPUFA levels (including ω-3 and ω-6) in retinas under normoglycemic and hyperglycemic conditions. ω-3 (vs. ω-6) LCPUFA activated the APN pathway by increasing the circulating APN levels and inducing expression of the retinal APN receptor. Our findings suggested that both ω-3 and ω-6 LCPUFA are crucial in protecting against retinal neurovascular dysfunction in a Phase I ROP model; adequate ω-6 LCPUFA levels must be maintained in addition to ω-3 supplementation to prevent retinopathy. Activation of the APN pathway may further enhance the ω-3 and ω-6 LCPUFA's protection against ROP.

Decreased plasma levels of PDGF-BB, VEGF-A, and HIF-2α in preterm infants after ibuprofen treatment

INTRODUCTION

Ibuprofen is one of the most common non-steroidal anti-inflammatory drugs used to close patent ductus arteriosus (PDA) in preterm infants. PDA is associated with bronchopulmonary dysplasia (BPD), while PDA closure by ibuprofen did not reduce the incidence of BPD or death. Previous studies have indicated an anti-angiogenesis effect of ibuprofen. This study investigated the change of angiogenic factors after ibuprofen treatment in preterm infants.

METHODS

Preterm infants with hemodynamically significant PDA (hsPDA) were included. After confirmed hsPDA by color doppler ultrasonography within 1 week after birth, infants received oral ibuprofen for three continuous days. Paired plasma before and after the ibuprofen treatment was collected and measured by ELISA to determine the concentrations of platelet-derived growth factor-BB (PDGF-BB) and vascular endothelial growth factor A (VEGF-A), and hypoxia-inducible factor-2α (HIF-2α).

RESULTS

17 paired plasma from infants with hsPDA were collected. The concentration of PDGF-BB and VEGF-A significantly decreased after ibuprofen treatment (1,908 vs. 442 pg/mL for PDGF-BB, 379 vs. 174 pg/mL for VEGF-A). HIF-2α level showed a tendency to decrease after ibuprofen treatment, although the reduction was not statistically significant (p = 0.077).

CONCLUSION

This study demonstrated decreased vascular growth factors after ibuprofen exposure in hsPDA infants.

Thrombocytopenia as Type 1 ROP Biomarker: A Longitudinal Study

This study aimed to prospectively evaluate the association between the appearance and evolution of retinopathy of prematurity (ROP) and selected blood parameters, focusing on platelets count. In total, 157 preterm consecutive babies screened for ROP were included and classified in: ROP necessitating treatment (group ROP1), ROP regressed without therapy (group ROP2) and no ROP (group no-ROP), divided in two phases for each group depending on gestational age. Blood parameters were weekly gathered and referred to postmenstrual age, ROP severity and phase. Platelet count mean values were statistically lower (p < 0.001) during both phases in ROP1 group (179 × 10⁹/L vs. 213 × 10⁹/L in phase 1 and 2, respectively) vs. other groups (ROP2: 286 × 10⁹/L vs. 293 × 10⁹/L; no ROP: 295 × 10⁹/L vs. 313 × 10⁹/L). Platelet count at birth <181 × 10⁹ was statistically associated with Type 1 ROP development and evolution (sensibility = 76.47%, 95% confidence interval 60.0–87.6; specificity = 66.12%, 95% confidence interval 57.3–73.9). In ROP 1 group, a platelets count mean value “spike” (392.6 × 109/L) was documented at 36 weeks of corrected gestational age, preceding the need for treatment performed at a median of 38.1 ± 3.2 weeks. Early birth thrombocytopenia is confirmed as a biomarker of development and progression of ROP requiring treatment. The increase of platelets count at 35–37 weeks of corrected gestational age can be considered a possible clinical biomarker anticipating Type 1 ROP progression in preterm infants.

Metabolism in Retinopathy of Prematurity

Retinopathy of prematurity is defined as retinal abnormalities that occur during development as a consequence of disturbed oxygen conditions and nutrient supply after preterm birth. Both neuronal maturation and retinal vascularization are impaired, leading to the compensatory but uncontrolled retinal neovessel growth. Current therapeutic interventions target the hypoxia-induced neovessels but negatively impact retinal neurons and normal vessels. Emerging evidence suggests that metabolic disturbance is a significant and underexplored risk factor in the disease pathogenesis. Hyperglycemia and dyslipidemia correlate with the retinal neurovascular dysfunction in infants born prematurely. Nutritional and hormonal supplementation relieve metabolic stress and improve retinal maturation. Here we focus on the mechanisms through which metabolism is involved in preterm-birth-related retinal disorder from clinical and experimental investigations. We will review and discuss potential therapeutic targets through the restoration of metabolic responses to prevent disease development and progression.