Regulation of vascular endothelial growth factor-dependent retinal neovascularization by insulin-like growth factor-1 receptor

Clinical and Growth Correlates of Retinopathy of Prematurity in Preterm Infants with Surgical Necrotizing Enterocolitis and Intestinal Perforation

OBJECTIVE

 This study aimed to identify the clinical and growth parameters associated with retinopathy of prematurity (ROP) in infants with necrotizing enterocolitis (NEC) and spontaneous ileal perforation (SIP).

STUDY DESIGN

 We conducted a retrospective cohort study that compared clinical data before and after NEC/SIP onset in neonates, categorizing by any ROP and severe ROP (type 1/2) status.

RESULTS

 The analysis included 109 infants with surgical NEC/SIP. Sixty infants (60/109, 55%) were diagnosed with any ROP, 32/109 (29.3%) infants (22% type 1 and 7.3% type 2) with severe ROP. On univariate analysis, those with severe ROP (32/109, 39.5%) were of lower median gestational age (GA, 23.8 weeks [23.4, 24.6] vs. 27.3 [26.3, 29.0], p < 0.001), lower median birth weight (625 g [512, 710] vs. 935 [700, 1,180], p < 0.001) and experienced higher exposure to clinical chorioamnionitis (22.6 vs. 2.13%, p < 0.006), and later median onset of ROP diagnosis (63.0 days [47.0, 77.2] vs. 29.0 [19.0, 41.0], p < 0.001), received Penrose drain placement more commonly (19 [59.4%] vs. 16 [34.0%], p = 0.04), retained less residual small bowel (70.0 cm [63.1, 90.8] vs. 90.8 [72.0, 101], p = 0.007) following surgery, were exposed to higher FiO2 7 days after birth (p = 0.001), received ventilation longer and exposed to higher FiO2 at 2 weeks (p < 0.05) following NEC and developed acute kidney injury (AKI) more often (25 [86.2%] vs. 20 [46.5%], p = 0.002) than those without ROP. Those with severe ROP had lower length, weight for length, and head circumference z scores. In an adjusted Firth's logistic regression, GA (adjusted odds ratio [aOR] = 0.51, 95% confidence interval [CI]: [0.35, 0.76]) and diagnosis at later age (aOR = 1.08, 95% CI: [1.03, 1.13]) was shown to be significantly associated with any ROP.

CONCLUSION

 Infants who develop severe ROP following surgical NEC/SIP are likely to be younger, smaller, have been exposed to more O2, develop AKI, and grow poorly compared with those did not develop severe ROP.

KEY POINTS

· Thirty percent of infants with NEC/SIP had severe ROP.. · Those with severe ROP had poor growth parameters before and after NEC/SIP.. · Risk factors based ROP prevention strategies are needed to have improved ophthalmic outcomes..

Identifying transcriptomic profiles of iron-quercetin complex treated peripheral blood mononuclear cells from healthy volunteers and diabetic patients

Peripheral blood is an alternative source of stem/progenitor cells for regenerative medicine owing to its ease of retrieval and blood bank storage. Previous in vitro studies indicated that the conditioned medium derived from peripheral blood mononuclear cells (PBMCs) treated with the iron-quercetin complex (IronQ) contains potent angiogenesis and wound-healing properties. This study aims to unveil the intricate regulatory mechanisms governing the effects of IronQ on the transcriptome profiles of human PBMCs from healthy volunteers and those with diabetes mellitus (DM) using RNA sequencing analysis. Our findings revealed 3741 and 2204 differentially expressed genes (DEGs) when treating healthy and DM PBMCs with IronQ, respectively. Functional enrichment analyses underscored the biological processes shared by the DEGs in both conditions, including inflammatory responses, cell migration, cellular stress responses, and angiogenesis. A comprehensive exploration of these molecular alterations exposed a network of 20 hub genes essential in response to stimuli, cell migration, immune processes, and the mitogen-activated protein kinase (MAPK) pathway. The activation of these pathways enabled PBMCs to potentiate angiogenesis and tissue repair. Corroborating this, quantitative real-time polymerase chain reaction (qRT-PCR) and cell phenotyping confirmed the upregulation of candidate genes associated with anti-inflammatory, pro-angiogenesis, and tissue repair processes in IronQ-treated PBMCs. In summary, combining IronQ and PBMCs brings about substantial shifts in gene expression profiles and activates pathways that are crucial for tissue repair and immune response, which is promising for the enhancement of the therapeutic potential of PBMCs, especially in diabetic wound healing.

Association between albuminuria and retinal microvascular parameters measured with swept-source optical coherence tomography angiography in patients with diabetic retinopathy

PURPOSE

To evaluate the relationship between urine albumin excretion (UAE) and retinal microvascular parameters assessed using swept-source optical coherence tomography angiography (SS-OCTA) in patients with diabetic retinopathy (DR).

METHODS

This retrospective cross-sectional study included 180 patients with diabetes and 50 age-matched controls. Patients with diabetes were grouped according to the five-stage DR severity, combined with the presence of albuminuria. All subjects underwent 12×12mm2 field SS-OCTA. The foveal avascular zone metrics, vessel density, and capillary nonperfusion area (NPA) were quantified using a semi-automatic software algorithm on three different rectangular fields (3×3 mm2, 6×6 mm2, and 10×10 mm2). The correlations between albuminuria and the four OCTA parameters were analyzed.

RESULTS

A total of 105 subjects had normal UAE, and 75 subjects had albuminuria. Of the 102 subjects whose DR severity was higher than mild non-proliferative DR (NPDR), capillary NPA on the 3×3 mm2, 6×6 mm2, and 10×10 mm2 fields was significantly larger in the albuminuria group. None of the OCTA parameters were significantly different between the two groups in subjects with mild NPDR or without DR. Multiple logistic regression analysis showed that an increase in NPA in the 6×6 mm2 and 10×10 mm2 fields was a significant risk factor for the presence of albuminuria (odds ratio = 1.92 and 1.35).

CONCLUSION

An increase in capillary NPA was independently associated with albuminuria in patients with clinically significant DR levels. SS-OCTA imaging can be a useful marker for the early detection of diabetic nephropathy.

Propranolol: a new pharmacologic approach to counter retinopathy of prematurity progression

Despite the evident progress in neonatal medicine, retinopathy of prematurity (ROP) remains a serious threat to the vision of premature infants, due to a still partial understanding of the mechanisms underlying the development of this disease and the lack of drugs capable of arresting its progression. Although ROP is a multifactorial disease, retinal vascularization is strictly dependent on oxygen concentration. The exposition of the retina of a preterm newborn, still incompletely vascularized, to an atmosphere relatively hyperoxic, as the extrauterine environment, induces the downregulation of proangiogenic factors and therefore the interruption of vascularization (first ischemic phase of ROP). However, over the following weeks, the growing metabolic requirement of this ischemic retina produces a progressive hypoxia that specularly promotes the surge of proangiogenic factors, finally leading to proliferative retinopathy (second proliferative phase of ROP). The demonstration that the noradrenergic system is actively involved in the coupling between hypoxia and the induction of vasculogenesis paved the way for a pharmacologic intervention aimed at counteracting the interaction of noradrenaline with specific receptors and consequently the progression of ROP. A similar trend has been observed in infantile hemangiomas, the most common vascular lesion of childhood induced by pre-existing hypoxia, which shares similar characteristics with ROP. The fact that propranolol, an unselective antagonist of β1/2 adrenoceptors, counteracts the growth of infantile hemangiomas, suggested the idea of testing the efficacy of propranolol in infants with ROP. From preclinical studies, ongoing clinical trials demonstrated that topical administration of propranolol likely represents the optimal approach to reconcile its efficacy and maximum safety. Given the strict relationship between vessels and neurons, recovering retinal vascularization with propranolol may add further efficacy to prevent retinal dysfunction. In conclusion, the strategy of contrasting precociously the progression of the disease appears to be more advantageous than the current wait-and-see therapeutic approach, which instead is mainly focused on avoiding retinal detachment.

Extracellular vimentin as a versatile immune suppressive protein in cancer

The interest in finding new targets in the tumor microenvironment for anti-cancer therapy has increased rapidly over the years. More specifically, the tumor-associated blood vessels are a promising target. We recently found that the intermediate filament protein vimentin is externalized by endothelial cells of the tumor vasculature. Extracellular vimentin was shown to sustain angiogenesis by mimicking VEGF and supporting cell migration, as well as endothelial cell anergy, the unresponsiveness of the endothelium to proinflammatory cytokines. The latter hampers immune cell infiltration and subsequently provides escape from tumor immunity. Other studies showed that extracellular vimentin plays a role in sustained systemic and local inflammation. Here we will review the reported roles of extracellular vimentin with a particular emphasis on its involvement in the interactions between immune cells and the endothelium in the tumor microenvironment. To this end, we discuss the different ways by which extracellular vimentin modulates the immune system. Moreover, we review how this protein can alter immune cell-vessel wall adhesion by altering the expression of adhesion proteins, attenuating immune cell infiltration into the tumor parenchyma. Finally, we discuss how vimentin-targeting therapy can reverse endothelial cell anergy and promote immune infiltration, supporting anti-tumor immunity.

Usefulness of Children's Hospital of Philadelphia ROP (CHOP ROP) model in the prediction of type 1 ROP

Purpose

Children's Hospital of Philadelphia retinopathy of prematurity (CHOP ROP) model can be used to predict ROP, a leading cause of childhood blindness, using risk factors such as postnatal weight gain, birth weight (BW), and gestation age (GA). The purpose of this study was to determine the usefulness of the CHOP ROP for the prediction of treatable ROP.

Methods

This was a prospective observational study. Babies <34 weeks of GA, BW <2000 grams, and GA 34-36 weeks with risk factors such as respiratory distress syndrome (RDS) were included; ROP screening, follow-up, and treatment were performed based on national guidelines. The average daily postnatal weight gain was measured, and the CHOP nomogram was plotted. Babies were categorized as high risk or low risk based on the "CHOP" alarm. The sensitivity and specificity of the CHOP ROP for the detection of treatable ROP were determined. In case of poor sensitivity, a new cutoff alarm level was planned using logistic regression analysis.

Results

Of 62 screened infants, 23 infants did not fulfill the criteria of the CHOP algorithm and were excluded. Thus, in the study on 39 infants, the predictive model with an alarm level of 0.014 had 100% specificity and 20% sensitivity. With the "new" alarm level (cutoff) of 0.0003, the CHOP nomogram could detect all the infants who developed treatable ROP, that is, sensitivity increased to 100% but specificity decreased to 10.5%.

Conclusion

The CHOP ROP model with a cutoff point (0.014) performed poorly in predicting severe ROP in the study. Thus, there is a need to develop inclusive and more sensitive tailor-made algorithms.

Study protocol of OmegaROP-2 prospective study: expression of placental fatty acid receptors in preterm newborns with retinopathy of prematurity

BACKGROUND

Incomplete vascularization of the retina in preterm infants carries a risk of retinopathy of prematurity (ROP). Progress in neonatal resuscitation in developing countries has led to the survival of an increasing number of premature infants, resulting in an increased rate of ROP and consequently in visual disability. Strategies to reduce ROP involve optimizing oxygen saturation, nutrition, and normalizing factors such as insulin-like growth factor 1 and n-3 long-chain polyunsaturated fatty acids (LC-PUFA). Our previous study, OmegaROP, showed that there is an accumulation or retention of docosahexaenoic acid (DHA) in mothers of infants developing ROP, suggesting abnormalities in the LC-PUFA placental transfer via fatty acid transporting proteins. The present study aims to better understand the LC-PUFA transport dysfunction in the fetoplacental unit during pregnancy and to find a novel target for the prevention of ROP development.

METHODS

The study protocol is designed to evaluate the correlation between the expression level of placental fatty acid receptors and ROP occurrence. This ongoing study will include 100 mother-infant dyads: mother-infant dyads born before 29 weeks of gestational age (GA) and mother-infant dyads with full-term pregnancies. Recruitment is planned over a period of 46 months. Maternal and cord blood samples as well as placental tissue samples will be taken following delivery. ROP screening will be performed using wide-field camera imaging according to the International Classification of ROP consensus statement.

DISCUSSION

The results of this study will have a tangible impact on public health. Indeed, if we show a correlation between the expression level of placental omega-3 receptors and the occurrence of ROP, it would be an essential step in discovering novel pathophysiological mechanisms involved in this retinopathy.

TRIAL REGISTRATION

NCT04819893.

Retinopathy of prematurity: from oxygen management to molecular manipulation

INTRODUCTION

Retinopathy of prematurity (ROP) is a vasoproliferative disorder of the premature retina with the potential to progress to extraretinal neovascularisation. This review serves as an introduction to retinopathy of prematurity (ROP), outlining key parts of ROP pathophysiology, diagnosis and treatment. ROP is traditionally diagnosed by indirect ophthalmoscopy and classified using anatomical zones, stages of disease, and the presence or absence of "plus disease" (dilation and tortuosity of the major retinal arterioles and venules). ROP has a bi-phasic pathophysiology: initial hyperoxia causes reduced retinal vascularisation, followed by pathological vaso-proliferation resulting from subsequent hypoxia and driven by vascular endothelial growth factor (VEGF).

ADVANCEMENTS IN MANAGEMENT

This review summarises previous trials to establish optimum oxygen exposure levels in newborns and more recently the development of anti-VEGF agents locally delivered to block pathological neovascularisation, which is technically easier to administer and less destructive than laser treatment.

FUTURE DIRECTIONS

There remains an ongoing concern regarding the potential unwanted systemic effects of intravitreally administered anti-VEGF on the overall development of the premature baby. Ongoing dosing studies may lessen these fears by identifying the minimally effective dose required to block extraretinal neovascularisation.

Angiogenesis and Tissue Repair Depend on Platelet Dosing and Bioformulation Strategies Following Orthobiological Platelet-Rich Plasma Procedures: A Narrative Review

Angiogenesis is the formation of new blood vessel from existing vessels and is a critical first step in tissue repair following chronic disturbances in healing and degenerative tissues. Chronic pathoanatomic tissues are characterized by a high number of inflammatory cells; an overexpression of inflammatory mediators; such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1); the presence of mast cells, T cells, reactive oxygen species, and matrix metalloproteinases; and a decreased angiogenic capacity. Multiple studies have demonstrated that autologous orthobiological cellular preparations (e.g., platelet-rich plasma (PRP)) improve tissue repair and regenerate tissues. There are many PRP devices on the market. Unfortunately, they differ greatly in platelet numbers, cellular composition, and bioformulation. PRP is a platelet concentrate consisting of a high concentration of platelets, with or without certain leukocytes, platelet-derived growth factors (PGFs), cytokines, molecules, and signaling cells. Several PRP products have immunomodulatory capacities that can influence resident cells in a diseased microenvironment, inducing tissue repair or regeneration. Generally, PRP is a blood-derived product, regardless of its platelet number and bioformulation, and the literature indicates both positive and negative patient treatment outcomes. Strangely, the literature does not designate specific PRP preparation qualifications that can potentially contribute to tissue repair. Moreover, the literature scarcely addresses the impact of platelets and leukocytes in PRP on (neo)angiogenesis, other than a general one-size-fits-all statement that "PRP has angiogenic capabilities". Here, we review the cellular composition of all PRP constituents, including leukocytes, and describe the importance of platelet dosing and bioformulation strategies in orthobiological applications to initiate angiogenic pathways that re-establish microvasculature networks, facilitating the supply of oxygen and nutrients to impaired tissues.

Clinical and Growth Correlates of Retinopathy of Prematurity in Preterm infants with Surgical Necrotizing Enterocolitis and intestinal Perforation

Background

we sought to determine the clinical and growth parameters associated with retinopathy of prematurity (ROP) in infants with necrotizing enterocolitis (NEC) and spontaneous ileal perforation (SIP).

Methods

Retrospective cohort study comparing clinical information before and following NEC/SIP onset in neonates with and without severe ROP (Type 1 and 2).

Results

Those with severe ROP (32/109, 39.5%) had lower GA, BW, chorioamnionitis, later median onset of ROP diagnosis and received Penrose drain and had higher AKI, poor weight z scores, poor linear growth, longer duration of ventilation and higher FIo2 than those without ROP following NEC/SIP. The GA and diagnosis at later age remained significant for any ROP on multi regression modelling.

Conclusion

The surgical NEC/SIP infants with severe ROP were more likely to be younger, smaller, had AKI, had higher oxygen exposure and poor weight gain and linear growth than those without severe ROP.

Research progress of VEGFR small molecule inhibitors in ocular neovascular diseases

Angiogenesis is the biological process in which existing blood vessels generate new ones and it is essential for body growth and development, wound healing, and granulation tissue formation. Vascular endothelial growth factor receptor (VEGFR) is a crucial cell membrane receptor that binds to VEGF to regulate angiogenesis and maintenance. Dysregulation of VEGFR signaling can lead to several diseases, such as cancer and ocular neovascular disease, making it a crucial research area for disease treatment. Currently, anti-VEGF drugs commonly used in ophthalmology are mainly four macromolecular drugs, Bevacizumab, Ranibizumab, Conbercept and Aflibercept. Although these drugs are relatively effective in treating ocular neovascular diseases, their macromolecular properties, strong hydrophilicity, and poor blood-eye barrier penetration limit their efficacy. However, VEGFR small molecule inhibitors possess high cell permeability and selectivity, allowing them to traverse and bind to VEGF-A specifically. Consequently, they have a shorter duration of action on the target, and they offer significant therapeutic benefits to patients in the short term. Consequently, there is a need to develop small molecule inhibitors of VEGFR to target ocular neovascularization diseases. This review summarizes the recent developments in potential VEGFR small molecule inhibitors for the targeted treatment of ocular neovascularization diseases, with the aim of providing insights for future studies on VEGFR small molecule inhibitors.

The Antiangiogenic Effect and Ocular Pharmacology of Novel Modified Nonsteroidal Anti-Inflammatory Drugs in the Treatment of Oxygen-Induced Retinopathy

Purpose: To evaluate the hypothesis that 3 novel compounds, OXT-328, Q-922, and CL-717 show efficacy in the treatment of oxygen-induced retinopathy (OIR) and whether or not their route of administration is intravitreal, topical, or systemic. Methods: The OIR mouse model, characterized by an avascular area (AVA) and a neovascular area (NVA) of the retina, was used to study retinopathy of prematurity and other retinal diseases characterized by abnormal vessel growth. We measured the effect of our compounds on both the AVA and NVA in whole mounts of mouse retinal tissue. We also evaluated their ability to prevent new vessel formation in chicken chorioallantoic membranes (CAMs). Finally, we measured the in vitro uptake and biodistribution of topically applied CL-717 in human eye explants. Results: In mice with OIR, compared to controls, a single intravitreal administration of Q-922 or OXT-328 significantly reduced both AVA and NVA. CL-717 administered as eye drops over 5 days also reduced AVA and NVA, whereas OXT-328 eye drops had no effect. Q-922 given intraperitoneal (150 mg/kg/day × 5 days) reduced AVA and NVA. Remarkably, explanted human eyes bathed in CL-717 show rapid uptake and biodistribution in ocular tissues. In the chicken CAM model, all 3 compounds reduced the formation of new blood vessels by about one-third. No side effect in mice was observed, except for mild ocular surface irritation with Q-922. Conclusions: Systemic administration of Q-922 or topical administration of CL-717 holds particular promise for a simplified treatment of proliferative retinopathies without the necessity of intravitreal injections.

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).

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.

Insulin-like growth factor-1 stimulates retinal cell proliferation via activation of multiple signaling pathways

Insulin-like growth factor-1 (IGF-1) plays critical roles in the development of the central nervous system (CNS), including the retina, regulating cell proliferation, differentiation, and survival. Here, we investigated the role of IGF-1 on retinal cell proliferation using primary cultures from rat neural retina. Our data show that IGF-1 stimulates retinal cell proliferation and regulates the expression of neurotrophic factors, such as interleukin-4 and brain-derived neurotrophic factor. In addition, our results indicates that IGF-1-induced retinal cell proliferation requires activation of multiple signaling pathways, including phosphatidylinositol 3-kinase, protein kinase Src, phospholipase-C, protein kinase C delta, and mitogen-activated protein kinase pathways. We further show that activation of matrix metalloproteinases and epidermal growth factor receptor is also necessary for IGF-1 enhancing retinal cell proliferation. Overall, these results unveil potential mechanisms by which IGF-1 ensures retinal cell proliferation and support the notion that manipulation of IGF-1 signaling may be beneficial in CNS disorders associated with abnormal cell proliferation.

Molecular mechanism of VEGF and its role in pathological angiogenesis

Over the last seven decades, a significant scientific contribution took place in the delineation of the implications of vascular endothelial-derived growth factor (VEGF) in the processes of angiogenesis. Under pathological conditions, mainly in response to hypoxia or ischemia, elevated VEGF levels promote vascular damage and the growth of abnormal blood vessels. Indeed, the development of VEGF biology has revolutionized our understanding of its role in pathological conditions. Hence, targeting VEGF or VEGF-mediated molecular pathways could be an excellent therapeutic strategy for managing cancers and intraocular neovascular disorders. Although anti-VEGF therapies, such as monoclonal antibodies and small-molecule tyrosine kinase inhibitors, have limited clinical efficacy, they can still significantly improve the overall survival rate. This thus demands further investigation through the development of alternative strategies in the management of VEGF-mediated pathological angiogenesis. This review article focuses on the recent developments toward the delineation of the functional biology of VEGF and the role of anti-VEGF strategies in the management of tumor and eye pathologies. Moreover, therapeutic angiogenesis, an exciting frontier for the treatment of ischemic disorders, is highlighted in this review, including wound healing.

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.

Elevated IGF-1 and GH Levels Are Correlated With a Thicker Iris and Wider Anterior Chamber Angle in Treatment-Naïve Acromegaly Patients

Purpose

To compare the difference in anterior segment biometrics derived from anterior segment optical coherence tomography (AS-OCT) between treatment-naïve acromegaly patients and normal controls and evaluate the correlations between above biometrics and insulin-like growth factor 1 (IGF-1) and growth hormone (GH) levels.

Methods

Sixty eyes of 30 acromegaly patients and 60 eyes of 30 normal controls were included in this case-control study. Central corneal thickness, pupil diameter, iris thickness (IT), iris curvature (IC), anterior chamber depth (ACD), anterior chamber width, lens vault (LV), angle open distance (AOD) 500, AOD750, and trabecular iris space area (TISA) 500 and TISA750 were measured by AS-OCT. General linear regression models were constructed to evaluate the independent endocrine factors affecting iris morphology and anterior chamber angle (ACA) width.

Results

The acromegaly patients had an evenly thicker iris (P < 0.001), a smaller IC (P < 0.05), a smaller LV (P = 0.040) and significantly larger AOD500, AOD750, TISA500 and TISA750 (P < 0.001). There was a positive correlation between the serum GH level and ACD in the acromegaly patients (P = 0.031). Linear regression models showed the lower LV and smaller IC were independent influencing factors of the increase in the AOD500, AOD750, and TISA750 and nasal TISA500. Serum IGF-1 was an independent factor for the increase in pupil diameter (β = 0.002, P = 0.031) and both the average nasal (β = 6.781*10⁻⁵, P = 0.049) and temporal (β = 7.736*10⁻⁵, P = 0.045) IT values and for the decrease in temporal IC (β < 0.001, P = 0.037). GH was an independent factor for the increase in temporal AOD750 (β = 0.001, P = 0.030) and temporal TISA750 (β = 0.002, P = 0.016).

Conclusions

Patients with acromegaly have a thicker IT, smaller IC, and lower LV with a wider ACA than normal controls. Serum GH is independently correlated with the temporal ACA width, whereas serum IGF-1 is independently correlated with IT, pupil diameter, and IC.

Daily Oxygen Supplementation and Risk of Retinopathy of Prematurity

PURPOSE

Excessive oxygen supplementation increases risk of retinopathy of prematurity (ROP). While numerous oxygen parameters could be considered when predicting ROP (saturation targets, actual saturation, fraction of inspired oxygen, etc.), complicated measures are impractical as screening criteria. We sought to develop a simple, clinically useful measure of daily oxygen supplementation during ages 0-28 days to improve prediction of ROP.

METHODS

Secondary analysis of two Postnatal Growth and ROP (G-ROP) Study cohorts (G-ROP-1 and G-ROP-2) at 45 hospitals. Infants with a known ROP outcome and complete oxygen data were included. Associations between severe ROP and days on supplemental oxygen (FiO2 > 21%), during ages 0-28 days (DSO28) were assessed, controlling for birth weight (BW) and gestational age (GA). New screening criteria incorporating DSO were developed and compared to current guidelines.

RESULTS

Among 8,949 studied infants, 459 (5.1%) developed type 1 ROP. DSO28 was associated with severe ROP (adjusted-OR 1.05 per day supplemental oxygen, 95%CI 1.03-1.07, p < .0001). The following criteria had 100% sensitivity for type 1 ROP and higher specificity than current guidelines: new BW/GA criteria with DSO (BW<901 g, GA<26 weeks, or DSO >3), 23.4% fewer infants examined; modified G-ROP criteria including DSO, 29.0% fewer infants; original G-ROP criteria, 31.8% fewer infants.

CONCLUSION

In high-level neonatal-care settings, incorporating DSO (a simple measure of oxygen supplementation) into screening criteria improves sensitivity and specificity for type 1 ROP over current BW-GA criteria, but does not perform as well as the validated G-ROP criteria.

Deletion of Tgfβ signal in activated microglia prolongs hypoxia-induced retinal neovascularization enhancing Igf1 expression and retinal leukostasis

Retinal neovascularization (NV) is the major cause of severe visual impairment in patients with ischemic eye diseases. While it is known that retinal microglia contribute to both physiological and pathological angiogenesis, the molecular mechanisms by which these glia regulate pathological NV have not been fully elucidated. In this study, we utilized a retinal microglia-specific Transforming Growth Factor-β (Tgfβ) receptor knock out mouse model and human iPSC-derived microglia to examine the role of Tgfβ signaling in activated microglia during retinal NV. Using a tamoxifen-inducible, microglia-specific Tgfβ receptor type 2 (Tgfβr2) knockout mouse [Tgfβr2 KO (ΔMG)] we show that Tgfβ signaling in microglia actively represses leukostasis in retinal vessels. Furthermore, we show that Tgfβ signaling represses expression of the pro-angiogenic factor, Insulin-like growth factor 1 (Igf1), independent of Vegf regulation. Using the mouse model of oxygen-induced retinopathy (OIR) we show that Tgfβ signaling in activated microglia plays a role in hypoxia-induced NV where a loss in Tgfβ signaling microglia exacerbates and prolongs retinal NV in OIR. Using human iPSC-derived microglia cells in an in vitro assay, we validate the role of Transforming Growth Factor-β1 (Tgfβ1) in regulating Igf1 expression in hypoxic conditions. Finally, we show that Tgfβ signaling in microglia is essential for microglial homeostasis and that the disruption of Tgfβ signaling in microglia exacerbates retinal NV in OIR by promoting leukostasis and Igf1 expression.

New Aspects on the Treatment of Retinopathy of Prematurity: Currently Available Therapies and Emerging Novel Therapeutics

Retinopathy of prematurity (ROP) is a rare proliferative ocular disorder in preterm infants. Because of the advancements in neonatal care, the incidence of ROP has increased gradually. Now, ROP is one of the leading causes of blindness in children. Preterm infants with immature retinal development are exposed to supplemental oxygen inside an incubator until their cardiopulmonary system is adequately developed. Once they are returned to room air, the relatively low oxygen level stimulates various angiogenesis factors initiating retinal neovascularization. If patients with ROP are not offered adequate and timely treatment, they can experience vision loss that may ultimately lead to permanent blindness. Although laser therapy and anti-vascular endothelial growth factor agents are widely used to treat ROP, they have limitations. Thus, it is important to identify novel therapeutics with minimal adverse effects for the treatment of ROP. To date, various pharmacologic and non-pharmacologic therapies have been assessed as treatments for ROP. In this review, the major molecular factors involved in the pathogenesis of ROP, currently offered therapies, therapies under investigation, and emerging novel therapeutics of ROP are discussed.

Insulin like growth factor-1 works synergistically with dopamine to attenuate diabetic retinopathy by downregulating vascular endothelial growth factor

AIM

Levels of Insulin-like growth factor-1 (IGF-1), a proangiogenic growth factor is elevated and dopamine downregulated in proliferative diabetic retinopathy (PDR). This study aims to investigate whether IGF-1 with dopamine can together modulate vascular endothelial growth factor (VEGF) to prevent proliferative diabetic retinopathy while also attenuating angiogenic effects of IGF-1.

METHODS

Effect of combination of levodopa L-Dopa with IGF-1 was tested on normal retinal pigment epithelium cells (ARPE-19) and human umbilical vein endothelial cells (HUVEC), followed by tube formation. Invivo analysis of anti-angiogenic potential assessed by chick chorioallantoic membrane (CAM) assay. Diabetes induction in wistar rats at two time points, 12 and 16 weeks, treated with L-Dopa+IGF-1 and analysed for morphological variations, serum and tissue dopamine levels, gene expression by real-time PCR and western blot assay.

RESULTS

L-Dopa+IGF-1 on ARPE-19 cells caused no toxicity and worked synergistically. Reduced number of vessels observed. Significant improvement in inner retina thickness (*p < 0.05) was observed when L-Dopa was given alone and/or with IGF-1. Dopamine levels improved significantly in both serum and tissue (*p < 0.05). Levels of VEGF and IGF-1 receptors reduced significantly in 12 weeks. Western studies suggest that L-Dopa+IGF-1 modulates its effects via Akt/ERK dependent pathway.

CONCLUSION

First ever report on synergistic effect of L-Dopa+IGF-1 in a rat model of diabetic retinopathy. Even though the effect of L-Dopa in combination with IGF-1 is comparable to levels of L-Dopa alone, this study presents an interesting finding of neuroprotective function of IGF-1, which has been studied in disease models of Parkinson's but not diabetes.

Diabetic Corneal Neuropathy: Pathogenic Mechanisms and Therapeutic Strategies

Diabetes mellitus (DM) is a major global public health problem that can cause complications such as diabetic retinopathy, diabetic neuropathy, and diabetic nephropathy. Besides the reporting of reduction in corneal nerve density and decrease in corneal sensitivity in diabetic patients, there may be a subsequent result in delayed corneal wound healing and increased corneal infections. Despite being a potential cause of blindness, these corneal nerve changes have not gained enough attention. It has been proposed that corneal nerve changes may be an indicator for diabetic neuropathy, which can provide a window for early diagnosis and treatment. In this review, the authors aimed to give an overview of the relationship between corneal nerves and diabetic neuropathy as well as the underlying pathophysiological mechanisms of corneal nerve fiber changes caused by DM for improved prediction and prevention of diabetic neuropathy. In addition, the authors summarized current and novel therapeutic methods for delayed corneal wound healing, nerve protection and regeneration in the diabetic cornea.

The role of growth hormone and IGF-1 in retinopathy: a prospective study of retinopathy in patients with acromegaly and impaired fasting glucose

AIMS

To investigate the effects of the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis on the incidence and progression of retinopathy.

METHODS

We enrolled 91 patients with acromegaly and 123 subjects with impaired fasting glucose (IFG) between 2008 and 2016 to examine the incidence and prevalence of retinopathy. Patients attended follow-ups in our clinics and underwent examinations according to the national guidelines for diabetes management. Both cohorts attended follow-ups until June 2019.

RESULTS

Both groups had similar HbA1c, cholesterol, and blood pressure levels. However, patients with acromegaly had higher GH (8.05 ± 16.18 vs. 0.78 ± 1.25 ng/mL) and IGF-1 (547.0 ± 342.1 vs. 146.7 ± 51.4 ng/mL) levels than in subjects with IFG. During the follow-up period, 8 patients (8.8%) with acromegaly and 12 patients (9.8%) with IFG developed some degree of retinopathy. Three patients with acromegaly and two with IFG progressed to proliferative retinopathy. Patients with acromegaly had the same incidence of non-proliferative retinopathy (odds ratio [OR] 0.830; 95% CI 0.318-2.164) and a non-statistically significantly higher incidence of proliferative retinopathy (OR 2.461; 95% CI 0.404-14.988).

CONCLUSION

The data reveals that GH and IGF-1 might play a crucial role in the development of proliferative retinopathy and influence its progression. Therefore, we suggest screening patients with acromegaly should be similar to diabetes patients.

Advanced proliferative diabetic retinopathy and macular edema in acromegaly: a case report and literature review

We describe the multimodal management of a patient with proliferative diabetic retinopathy and diabetic macular edema associated with active acromegaly. A 61-year-old Japanese female who had had type 2 diabetic mellitus for > 10 years complained of deteriorated eyesight. She had distinct acromegalic features, and her visual acuity was 0.05 (right) and 0.4 (left) because of sub-capsular cataracts and proliferative diabetic retinopathy with macular edema. Anti-vascular endothelial growth factor treatments, cataract surgeries and retinal direct laser photocoagulation were performed together with gradual glycemic control with basal insulin to prevent worsening of the visual impairment. She was given an injection of a long-acting somatostatin analog (octreotide LAR) and began taking three bolus mealtime insulin shots with basal insulin beginning 1 month before undergoing a trans-sphenoidal adenomectomy. After this successful surgery, her blood glucose levels immediately decreased, and the rapid-acting insulin at mealtimes was discontinued with the observation of normal growth hormone and insulin-like growth factor (IGF)-1 levels, suggesting that her acromegaly was in remission. Her visual acuity improved without a worsening of diabetic retinopathy. Since the increased IGF-1 production in systemic circulation and local vitreous fluids may be one of the aggravating factors for diabetic retinopathy, our patient's acromegaly complicated with severe retinopathy presented an opportunity for multimodal management in close collaboration with an ophthalmologist, neurosurgeon, and endocrinologist. Our literature review revealed that the estimated prevalence of diabetic retinopathy in cases of acromegaly associated with diabetes mellitus is 12.5-42.9%.

Effects of Intravitreal Aflibercept on the Systemic Insulin-like Growth Factor-I and Vascular Endothelial Growth Factor-A in Patients with Diabetic Retinopathy and Age-Related Macular Degeneration

Purpose

To analyze the effect of intravitreal aflibercept injections on systemic levels of insulin-like growth factor-1 and vascular endothelial growth factor-A in patients with diabetic retinopathy and age-related macular degeneration.

Methods

Vascular endothelial growth factor-A and insulin-like growth factor-1 levels were determined before and one week and four weeks after intravitreal injection of aflibercept (2.0 mg/50 μl) for 19 patients with age-related macular degeneration (mean age, 76 ± 11 years) and 18 patients with diabetic retinopathy (mean age, 64 ± 14 years). Twenty-two healthy individuals were enrolled as controls.

Results

A significant decline in systemic vascular endothelial growth factor-A level, from 43 (30–57) pg/ml at baseline to 8 (8–8) pg/ml (p < 0.001) at week one and 17 (8–25) pg/ml (p=0.0054) at week four, was observed in the age-related macular degeneration group. In the diabetic retinopathy group, vascular endothelial growth factor-A levels declined from 53 (35–117) pg/ml to 2 (1–5) pg/ml (p < 0.0001) one week after injection and 16 (13–22) pg/ml four weeks after injection (p=0.0327). At baseline, systemic insulin-like growth factor-1 concentration was higher in the diabetic retinopathy group (57 [37–99] pg/ml) than in the age-related macular degeneration group (35 [24–51] pg/ml) (p=0.0056). A subgroup analysis showed that patients in the proliferative diabetic retinopathy subgroup had significantly higher systemic insulin-like growth factor-1 concentrations (71 [44.7–243] pg/ml) than those in the nonproliferative diabetic retinopathy subgroup (43 [29–66] pg/ml) (p=0.0048).

Conclusions

The difference between the baseline systemic insulin-like growth factor-1 levels of the age-related macular degeneration and diabetic retinopathy groups and the higher insulin-like growth factor-1 levels in the proliferative diabetic retinopathy subgroup one week after aflibercept therapy suggest that insulin-like growth factor-1 may play a role in the pathomechanism of diabetic retinopathy.

Caveolin-1 Down-Regulation Reduces VEGF-A Secretion Induced by IGF-1 in ARPE-19 Cells

The insulin-like growth factor 1 (IGF-1) stimulates expression and secretion of vascular endothelial growth factor-A (VEGF-A), the main actor in ocular neovascularization, by RPE cells. Activity of IGF-1 is regulated by interaction between its receptor and Caveolin-1 (Cav-1), the main component of caveolae. The aim of this study was to investigate whether modulation of Cav-1 expression affects synthesis and secretion of VEGF-A. ARPE-19 cells were transfected with small interfering RNA for Cav-1 (si-Cav-1) and with control siRNA (si-CTR) and stimulated with IGF-1. We found that down-regulation of Cav-1 did not affect activation of IGF-1R but regulated in an opposite manner the phosphorylation of Akt and Erk1/2. Moreover, we found that IGF-1 increased mRNA levels of VEGF-A in both si-CTR and in si-Cav-1 ARPE-19 cells and that Cav-1 silencing significantly reduced basal and IGF-1-stimulated VEGF-A release. Then we investigated the response of the microvascular endothelial cell line HMEC-1 to secretory products of ARPE-19 cells by evaluating wound healing closure, finding that conditioned media from si-Cav-1-ARPE-19 cells reduced endothelial cell migration rate. These data demonstrate that Cav-1 regulates secretion of VEGF-A, and that the depletion of Cav-1 reduces IGF-1 induced VEGF-A secretion in ARPE-19 cells and the migratory potential of their secretory products.

Time to regain birth weight - a marker to predict the severity of retinopathy of prematurity?

BACKGROUND

Poor weight gain in the first few weeks of life has been studied as a predictor of retinopathy of prematurity (ROP). Our aim was to assess whether time taken to regain birthweight (BW) be used as an additional marker to identify infants with type 1 ROP.

METHODS

In this retrospective study, preterm infants (< 27 weeks gestational age at birth) born during the period from 1/1/2010-31/12/2015 at a tertiary neonatal intensive care unit in Australia were included. Twenty-seven preterm infants with Type 1 ROP were identified. Controls (No ROP or ROP other than type 1) were matched with cases on gestational age at birth and BW (1:4 ratio). Data were collected from the database and medical records.

RESULTS

The median (IQR) gestational age for Type 1 ROP and control groups were 24 (24-26) and 25 (24-26) weeks respectively and median (IQR) BW for Type 1 ROP and control groups were 675 (635-810) and 773 (666-884) grams respectively. Preterm infants with Type 1 ROP were more likely to be small for gestational age (SGA) (18.5% vs 3.7%, p = 0.015) and had increased weeks on oxygen therapy (median 11.9 vs 9.1, p = 0.028). Time to regain BW was longer in preterm infants with type 1 ROP than controls but did not reach statistical significance (median 9 vs 7 days, OR 1.08, 95% CI 1.00-1.17, p = 0.059) adjusted for SGA and duration of oxygen therapy. The area under the curve from the time to regain BW model with adjustment for SGA and duration of oxygen therapy was 0.73 (95% CI 0.62-0.83).

CONCLUSION

We hypothesize that time to regain BW has potential to aid prediction of Type 1 ROP and this warrants further investigation in a larger prospective study.

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.

Alteration in choroidal microvasculature determined by optical coherence tomography angiography in patients with acromegaly

AIM

We aimed to investigate the retinal layers and macular capillary structure using optical coherence tomography angiography (OCTA) with acromegaly patients and determine the relationship between OCTA parameters and disease duration, Growth hormone (GH) and Insuline growth factor (IGF - 1) levels.

PATIENTS AND METHOD

Twenty-two patients with acromegaly who were followed up in the endocrinology outpatient clinic of Sisli Hamidiye Etfal Health Training and Research Hospital, were recruited into the study. Healthy control group was consisted of 22 age and gender matched subjects. Complete opthalmological examination including best visual acuity (BCVA), axial lenght, intraocular pressure (IOP) measurement, anterior segment and fundus examination, central corneal thickness with pachymetry and OCTA measurement were performed in the patients and healthy control group. Foveal avascular zone (FAZ), foveal vascular density (FVD), parafoveal vascular density (PFVD), choroidal flow (CF), foveal thickness (FT) and choroidal thickness (CT) were compared beetwen groups. Correlation between disease duration, GH and IGF-1 levels and OCTA parameters were evaluated.

RESULTS

There was no statistically significant difference between the groups in terms of BCVA, axial length, IOP, FT, FAZ, FD and PFVD. Choroidal thickness and CF was significantly high in the patients group compared to healthy controls (respectively, p = 0.003, p = 0.022). The mean follow-up period in patients with acromegaly was 90±50.2 months. There was a significant correlation between GH and subfoveal choroidal thickness in the patient group (p < 0.001, r = 0.52), a significant correlation was determined between disease duration and corneal thickness (p = 0.01, r = 0.41). In addition, an inverse correlation was detected between the IGF-1 level and the FAZ domain (p = 0.022, r= -0.34).

CONCLUSION

In patients with acromegaly, choroidal vasculature seems to be more affected than the retinal vasculature.

Antiproliferative and Mitochondrial Protective Effects of Apigenin in an Oxygen-Induced Retinopathy In Vivo Mouse Model

Purpose: To investigate the effects of a common dietary flavonoid apigenin on retinal endothelial cell proliferation, retinal morphological structure, and apoptotic cell death in an oxygen-induced retinopathy (OIR) mouse model to evaluate the possibility of the use of apigenin in the treatment of ocular neovascular diseases (ONDs). Methods: Ninety-six newborn C57BL/6J mice were included. Eight groups were randomized, each including 12 mice. Two negative control groups were kept in room air: the first without any injection and the second received intravitreal (IV) dimethyl sulfoxide (DMSO), which is the solvent we used. The OIR groups were exposed to 75% ± 2% oxygen from postnatal days (PD) 7 to 12. On PD 12, the mice were randomly assigned to 6 groups: 2 OIR control groups (1 received no injection, 1 received IV-DMSO), 2 IV-apigenin groups (10 and 20 μg/mL), and 2 intraperitoneal (IP)-apigenin groups (10 and 20 mg/kg). We quantified retinal endothelial cell proliferation by counting neovascular tufts in cross-sections and examined histological and ultrastructural changes through light and electron microscopy. We evaluated apoptosis by terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL). Results: We detected a significant increase in endothelial cell proliferation in the OIR groups. Groups receiving apigenin, both IP and IV, had significant decreases in endothelial cells, atypical mitochondrion count, and apoptotic cells compared with the groups receiving no injections. None of the apigenin-injected groups revealed cystic degeneration or cell loss. Conclusions: Apigenin suppresses neovascularization, has antiapoptotic and antioxidative effects in an OIR mouse model, and can be considered a promising agent for treating OND. Clinical trial (Project number: DA15/19).

The prenatal phase of retinopathy of prematurity

AIM

To explore the current literature on prenatal inflammation-associated risk factors for retinopathy of prematurity (ROP).

METHODS

Subjective summary of selected experimental and epidemiological publications that support the authors' central hypothesis that the aetiology of ROP begins before birth.

RESULTS

Based on current evidence we suggest that, contrary to current aetiological models, the process of ROP development begins with a prephase in utero. This beginning is likely initiated by inflammatory responses that are associated with intrauterine infection.

CONCLUSION

We propose a novel aetio-pathogenetic model of ROP and suggest that the effects of postnatal exposure to inflammatory stressors (resulting from infection or hyperoxia or both) as well as those of other pre- and postnatal contributors to the complex pathogenesis of ROP might be modified by the prenatal phase of the disease.

Insulin-Like Growth Factor 1 in the Preterm Rabbit Pup: Characterization of Cerebrovascular Maturation following Administration of Recombinant Human Insulin-Like Growth Factor 1/Insulin-Like Growth Factor 1-Binding Protein 3

Following preterm birth, serum levels of insulin-like growth factor 1 (IGF-1) decrease compared to corresponding in utero levels. A recent clinical trial indicated that supplementation with recombinant human (rh) IGF-1/rhIGF-binding protein 3 (rhIGF-1/rhIGFBP-3) prevents severe intraventricular hemorrhage (IVH) in extremely preterm infants. In a preterm rabbit pup model, we characterized endogenous serum and hepatic IGF-1, along with brain distribution of IGF-1 and IGF-1 receptor (IGF1R). We then evaluated the effects of rhIGF-1/rhIGFBP-3 on gene expression of regulators of cerebrovascular maturation and structure. Similar to preterm infants, serum IGF-1 concentrations decreased rapidly after preterm birth in the rabbit pup. Administration of rhIGF-1/rhIGFBP-3 restored in utero serum levels but was rapidly eliminated. Immunolabeled IGF1R was widely distributed in multiple brain regions, displaying an abundant density in the choroid plexus and sub-ependymal germinal zones. Increased IGF-1 immunoreactivity, distributed as IGF1R, was detected 4 h after rhIGF-1/rhIGFBP-3 administration. The rhIGF-1/rhIGFBP-3 treatment led to upregulation of choroid plexus genes involved in vascular maturation and structure, with corresponding protein translation for most of these genes. The preterm rabbit pup model is well suited for evaluation of IGF-1-based prevention of IVH. Administration of rhIGF-1/rhIGFBP-3 affects cerebrovascular maturation, suggesting a role for it in preventing preterm IVH.

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.

Assessment of a New Nanostructured Microemulsion System for Ocular Delivery of Sorafenib to Posterior Segment of the Eye

Eye drop formulations allowing topical treatment of retinal pathologies have long been sought as alternatives to intravitreal administration. This study aimed to assess whether a novel nanostructured microemulsions system (NaMESys) could be usefully employed to deliver sorafenib to the retina following topical instillation. NaMESys carrying 0.3% sorafenib (NaMESys-SOR) proved to be cytocompatible in vitro on rabbit corneal cells, and well-tolerated following b.i.d. ocular administration to rabbits during a 3-month study. In rats subject to retinal ischemia-reperfusion, NaMESys-SOR significantly inhibited retinal expression of tumor necrosis factor-alpha (TNFα, 20.7%) and inducible nitric oxide synthase (iNos, 87.3%) mRNAs in comparison to controls. Similarly, in streptozotocin-induced diabetic rats, NaMESys-SOR inhibited retinal expression of nuclear factor kappa B (NFκB), TNFα, insulin like growth factor 1 (IGF1), IGF1 receptor (IGF1R), vascular endothelial growth factor receptor 1 (VEGFR1) and 2 (VEGFR2) mRNAs by three-fold on average compared to controls. Furthermore, a reduction in TNFα, VEGFR1 and VEGFR2 protein expression was observed by western blot. Moreover, in mice subject to laser-induced choroidal neovascularization, NaMESys-SOR significantly inhibited neovascular lesions by 54%. In conclusion, NaMESys-SOR was shown to be a well-tolerated ophthalmic formulation able to deliver effective amounts of sorafenib to the retina, reducing proinflammatory and pro-angiogenic mediators in reliable models of proliferative retinopathies. These findings warrant further investigations on the full therapeutic potential of NaMESys-SOR eye drops, aiming to address unmet needs in the pharmacotherapy of retinal neovascular diseases.

Translational Research in Retinopathy of Prematurity: From Bedside to Bench and Back Again

Retinopathy of prematurity (ROP), a vascular proliferative disease affecting preterm infants, is a leading cause of childhood blindness. Various studies have investigated the pathogenesis of ROP. Clinical experience indicates that oxygen levels are strongly correlated with ROP development, which led to the development of oxygen-induced retinopathy (OIR) as an animal model of ROP. OIR has been used extensively to investigate the molecular mechanisms underlying ROP and to evaluate the efficacy of new drug candidates. Large clinical trials have demonstrated the efficacy of anti-vascular endothelial growth factor (VEGF) agents to treat ROP, and anti-VEGF therapy is presently becoming the first-line treatment worldwide. Anti-VEGF therapy has advantages over conventional treatments, including being minimally invasive with a low risk of refractive error. However, long-term safety concerns and the risk of late recurrence limit this treatment. There is an unmet medical need for novel ROP therapies, which need to be addressed by safe and minimally invasive therapies. The recent progress in biotechnology has contributed greatly to translational research. In this review, we outline how basic ROP research has evolved with clinical experience and the subsequent emergence of new drugs. We discuss previous and ongoing trials and present the candidate molecules expected to become novel targets.

A Good Way to Reduce Screening for Retinopathy of Prematurity: Development of the ROP Model in a China Preterm Population

Importance: Retinopathy of prematurity (ROP) is a preventable cause of blindness in children. Without treatment, more than 45% of eyes may suffer permanent vision loss. Current ROP screening guidelines, which include a range of birth weights (BWs) and gestational ages (GAs), may require screening many low-risk preemies who might develop severe ROP. Method: All high-risk infants in the neonatal intensive care unit (NICU) of the First Affiliated Hospital of Zhengzhou University from 2017 to 2021 were included in this retrospective cohort study. Each of the 27 candidate risk factors was evaluated in univariate analysis and adjusted for known risk factors (i.e., GA and BW). The significant results were analyzed in a backward selection multivariate logistic regression model. Receiver operating characteristic (ROC) curves and a nomogram were drawn. Results: The study included 2,040 infants who underwent ROP screening. The weight gain rate [OR, 2.65; 95% confidence interval (CI), 1.49-1.21 ≤ 12 g/d vs. > 18 g/d; P = 0.001], blood transfusion (OR, 2.03; 95% CI, 1.14-3.64; P = 0.017), invasive mechanical ventilation (OR, 1.74; 95% CI, 1.15-2.66; P = 0.009) and N-terminal segment of pro-B-type natriuretic peptide (NT-proBNP) ≥ 25,000 ng/L (OR, 1.51; 95% CI, 1.00-2.28; P = 0.048) were four new statistically independent risk factors in addition to GA and BW. The area under the curve (AUC) of the final multivariate model was 0.90 (95% CI, 0.88-0.92; P < 0.001). Conclusions and Relevance: These findings add to our understanding of ROP screening because they include all eligible infants rather than only high-risk infants, as in previous studies. Under the control of BW and GA, low weight gain rate, increased number of blood transfusion, invasive mechanical ventilation and NT-proBNP ≥ 25,000 ng/L were "new" statistically independent risk factors for ROP. The ROP risk can be calculated manually or represented by a nomogram for clinical use.

Regulation of blood-retinal barrier cell-junctions in diabetic retinopathy

Loss of the blood-retinal barrier (BRB) integrity and subsequent damage to the neurovascular unit in the retina are the underlying reasons for diabetic retinopathy (DR). Damage to BRB eventually leads to severe visual impairment in the absence of prompt intervention. Diabetic macular edema and proliferative DR are the advanced stages of the disease where BRB integrity is altered. Primary mechanisms contributing to BRB dysfunction include loss of cell-cell barrier junctions, vascular endothelial growth factor, advanced glycation end products-induced damage, and oxidative stress. Although much is known about the involvement of adherens and tight-junction proteins in the regulation of vascular permeability in various diseases, there is a significant gap in our knowledge on the junctional proteins expressed in the BRB and how BRB function is modulated in the diabetic retina. In this review article, we present our current understanding of the molecular composition of BRB, the changes in the BRB junctional protein turnover in DR, and how BRB functional modulation affects vascular permeability and macular edema in the diabetic retina.

IGF1, serum glucose, and retinopathy of prematurity in extremely preterm infants

BACKGROUND

Hyperglycemia, insulin insensitivity, and low IGF1 levels in extremely preterm infants are associated with an increased risk of retinopathy of prematurity (ROP), but the interactions are incompletely understood.

METHODS

In 117 extremely preterm infants, serum glucose levels and parenteral glucose intake were recoded daily in the first postnatal week. Serum IGF1 levels were measured weekly. Mice with oxygen-induced retinopathy alone versus oxygen-induced retinopathy plus streptozotocin-induced hyperglycemia/hypoinsulinemia were assessed for glucose, insulin, IGF1, IGFBP1, and IGFBP3 in blood and liver. Recombinant human IGF1 was injected to assess the effect on glucose and retinopathy.

RESULTS

The highest mean plasma glucose tertile of infants positively correlated with parenteral glucose intake [r₍₃₉₎ = 0.67, P < 0.0001]. IGF1 plasma levels were lower in the high tertile compared with those in low and intermediate tertiles at day 28 (P = 0.038 and P = 0.03). In high versus lower glucose tertiles, ROP was more prevalent (34 of 39 versus 19 of 39) and more severe (ROP stage 3 or higher; 71% versus 32%). In oxygen-induced retinopathy, hyperglycemia/hypoinsulinemia decreased liver IGF1 expression (P < 0.0001); rh-IGF1 treatment improved normal vascular regrowth (P = 0.027) and reduced neovascularization (P < 0.0001).

CONCLUSION

In extremely preterm infants, high early postnatal plasma glucose levels and signs of insulin insensitivity were associated with lower IGF1 levels and increased ROP severity. In a hyperglycemia retinopathy mouse model, decreased insulin signaling suppressed liver IGF1 production, lowered serum IGF1 levels, and increased neovascularization. IGF1 supplementation improved retinal revascularization and decreased pathological neovascularization. The data support IGF1 as a potential treatment for prevention of ROP.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02760472 (Donna Mega).

FUNDING

This study has been supported by the Swedish Medical Research Council (14940, 4732, 20144-01-3, and 21144-01-3), a Swedish government grant (ALFGB2770), Lund medical faculty grants (ALFL, 11615 and 11601), the Skåne Council Foundation for Research and Development, the Linnéa and Josef Carlsson Foundation, the Knut and Alice Wallenberg Foundation, the NIH/National Eye Institute (EY022275, EY017017, EY017017-13S1, and P01 HD18655), European Commission FP7 project 305485 PREVENT-ROP, Deutsche Forschungsgemeinschaft (CA-1940/1-1), and Stiftelsen De Blindas Vänner.

In extremely preterm infants, high early postnatal plasma glucose levels and signs of insulin insensitivity were associated with lower IGF1 levels and increased retinopathy of prematurity severity.

Validation of the postnatal growth and retinopathy of prematurity screening criteria

The objective of this study was to validate the generalizability of the Postnatal Growth and Retinopathy of Prematurity Study screening criteria in a new cohort of infants at risk for retinopathy of prematurity (ROP). This retrospective validation study conducted at a single academic medical center included 484 infants at risk for ROP born between January 14, 2014, and December 21, 2019. The primary outcomes evaluated were sensitivity for both type 1 and type 2 ROP, as defined by the Early Treatment of Retinopathy of Prematurity Study, as well as the reduction in total number of infants requiring ROP examinations. Secondary outcomes included the total number of ROP examinations avoided and the potential cost reduction of eliminating these examinations. In a cohort of 484 infants at risk for ROP, the criteria identified 40 of 40 (100%, 95% confidence interval 91.19%-100%) type 1 ROP cases and 27 of 27 (100%, 95% confidence interval 87.23%-100%) type 2 ROP cases while reducing the total number of infants screened by 35.7%. The Postnatal Growth and Retinopathy of Prematurity Study criteria were found in this study to be generalizable to a cohort of infants at a single teaching institution in central Texas. If applied during the studied interval, these criteria could have significantly reduced the number of infants undergoing ROP examinations and maintained excellent sensitivity for type 1 ROP.

Validation of WINROP (online prediction model) to identify severe retinopathy of prematurity (ROP) in an Australian preterm population: a retrospective study

INTRODUCTION

Retinopathy of prematurity (ROP) is the most common disease leading to blindness in extreme preterm infants. Current screening guidelines recommend frequent eye examinations. There is a dearth of trained ophthalmologists for these frequent screening procedures. The ANZNN neonatal network report (2013) found that only 6.4% of all screened infants had severe ROP and less than half received treatment. WINROP (online prediction model, Sweden) uses the postnatal weight gain (surrogate marker for low insulin-like growth factor IGF-1 and poor retinal vascular growth) to identify ROP requiring treatment and aims to reduce the number of examinations. Our objective was to validate the WINROP model in an Australian cohort of preterm infants.

METHODS

Birth weight, gestational age, and weekly weight measurements were retrieved retrospectively along with the final ROP outcomes and plotted on the online WINROP software.

RESULTS

The sensitivity, specificity, positive predictive value, and negative predictive value of WINROP were 85.7%, 59.0%, 6.98%, and 99.1% respectively for a cohort of 221 preterm infants (Median birth weight, 1040 g; Gestational age, 27.9 weeks). WINROP alarm was signaled in 42.6% of all infants. WINROP did not signal an alarm in one infant who needed treatment. This infant had intra ventricular hemorrhage grade 3-4 and temporary ventricular dilatation.

CONCLUSIONS

This is the first Australian study validating WINROP model. Our findings suggest that it lacked sensitivity to be used alone. However, adjusting the algorithm for the Australian population may improve the efficacy and reduce the number of examinations when used along with the current screening guidelines.

Efficacy of Aflibercept Treatment and Its Effect on the Retinal Perfusion in the Oxygen-Induced Retinopathy Mouse Model of Retinopathy of Prematurity

INTRODUCTION

Bevacizumab and ranibizumab, which are anti-vascular endothelial growth factor (VEGF) medications, are used frequently in the treatment for retinopathy of prematurity (ROP) in infants. Aflibercept, or VEGF Trap, has been used anecdotally, but translation and clinical studies are lacking.

OBJECTIVE

This study investigates the efficacy of aflibercept at reducing areas of non-perfused retina and studies its effect on normal angiogenesis in the oxygen-induced retinopathy mouse model of ROP.

METHODS

C57BL/6 J mice were assigned to room air control (n = 21 eyes) or hyperoxia with 75% oxygen (n = 84 eyes). The hyperoxic mice were assigned to 1 of 3 groups: 0 ng (n = 14 eyes), 100 ng (n = 35 eyes), or 1,000 ng (n = 35 eyes) of intravitreal aflibercept administered on postnatal day 14. Eyes were enucleated at PN17 and PN25 postinjection. Retinas were stained with anti-collagen IV antibody and photographed with microscopy. Areas of perfused and non-perfused retina were quantified using ImageJ software. Statistical comparisons were made using ANOVA with Tukey post hoc comparisons.

RESULTS

At PN17, there was no significant difference in the area of non-perfused retina between the hyperoxic control and the 100 and 1,000 ng aflibercept groups. At PN25, the 100 ng (p < 0.05) and 1,000 ng (p = 0.008) treatment groups displayed less non-perfusion compared to hyperoxic controls. At the 1,000 ng dose, there was increased non-perfusion compared to the 100 ng dose (p = 0.02). There was reduced non-perfusion by PN25 compared to PN17 for the 100 ng group (p < 0.05), with no difference in the 1,000 ng group.

CONCLUSIONS

The study shows that the area of non-perfused retina decreases effectively with aflibercept at PN25 with 100 ng dosage. With the 1,000 ng dosage, there is an inhibition of the physiologic angiogenesis with a higher area of non-perfused retina.

The Actions of IGF-1 in the Growth Plate and Its Role in Postnatal Bone Elongation

PURPOSE OF REVIEW

Bone elongation is a complex process driven by multiple intrinsic (hormones, growth factors) and extrinsic (nutrition, environment) variables. Bones grow in length by endochondral ossification in cartilaginous growth plates at ends of developing long bones. This review provides an updated overview of the important factors that influence this process.

RECENT FINDINGS

Insulin-like growth factor-1 (IGF-1) is the major hormone required for growth and a drug for treating pediatric skeletal disorders. Temperature is an underrecognized environmental variable that also impacts linear growth. This paper reviews the current state of knowledge regarding the interaction of IGF-1 and environmental factors on bone elongation. Understanding how internal and external variables regulate bone lengthening is essential for developing and improving treatments for an array of bone elongation disorders. Future studies may benefit from understanding how these unique relationships could offer realistic new approaches for increasing bone length in different growth-limiting conditions.

Minicircle-based GCP-2 ex vivo gene therapy enhanced the reepithelialization and angiogenic capacity

Recently, minicircle (MC)-based cell therapy has been emerging as a novel technology for nonviral genetic modification. In this study, we investigated the characteristics of granulocyte chemotactic protein-2 (GCP-2)-overexpressing fibroblasts (GCP-2/MC) using MC microporation technology, as well as its therapeutic mechanism in wound healing. GCP-2 parent plasmid and MC containing GCP-2 were generated. Human dermal fibroblasts (HDF) were transfected with MC containing GCP-2. Quantitative reverse transcription polymerase chain reaction (qRT-PCR), scratch wound assay, and in vivo wound healing assay were performed. Gene and protein expression analysis revealed that GCP-2/MC highly expressed epithelialization growth factor, epidermal growth factor (EGF), chemokines, GCP-2, interleukin (IL)-8, as well as wound healing-associated genes such as insulin growth factor (IGF)-1 and hepatocyte growth factor (HGF). An in vitro scratch wound closure and matrigel tube formation assays demonstrated that the culture medium derived from GCP-2/MC substantially accelerated the wound closure and matrigel network formation. Wounds in nude mice were created by skin excisions followed by injections of GCP-2/MC. Results showed high cell survival potential and that GCP-2/MC transplantation highly accelerated skin wound closure by increasing reepithelialization, capillary density, and enhancing angiogenic factors, suggesting direct benefits for cutaneous closure. Taken together, these data suggest that MC-based GCP-2 overexpression could be a promising alternative strategy for promoting wound healing.