Essential role of growth hormone in ischemia-induced retinal neovascularization

Validation of a Published Model to Reduce Burden of Retinopathy of Prematurity Screening

PURPOSE

The E-ROP study evaluated 1257 patients screened for retinopathy of prematurity (ROP), and found that no infant born at or after 27 weeks' gestational age and having a birthweight over 750 g developed treatable disease if they had no ROP at 37 weeks' gestational age. The study investigators suggested that there is little value in continued screening of infants meeting these criteria who have no ROP at 37 weeks. We attempted to replicate these published data in a larger multi-center cohort to validate or refute this hypothesis.

DESIGN

Retrospective cohort study.

METHODS

We conducted a chart review of every infant treated for ROP from February 2004 through April 2022 at 6 medical centers located in the mid-southern region of the United States. We evaluated gestational age, birthweight, and presence or absence of ROP at 37 weeks' gestational age to determine whether any treated infants would have been "missed" using these screening criteria.

RESULTS

Of 6729 infants screened, 298 (4.43%) received treatment. Ten infants who required treatment developed first evidence of ROP after 37 weeks' gestational age. However, only 1 infant was >750 g birthweight and >27 weeks' gestational age. This patient developed zone 2, stage 3 with pre-plus disease and was treated because of limited access to care at a remote hospital; however, ROP was detected at the first examination after 37 weeks, so this infant would have been identified for continued follow-up.

CONCLUSION

Our results, in a cohort 5 times that of the original study, replicated that infants >750 g birthweight and >27 weeks' gestational age did not develop treatable ROP if they had no ROP at 37 weeks, supporting the termination of examination at that time in patients meeting these criteria.

Pathophysiology of Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is a complex disease involving development of the neural retina, ocular circulations, and other organ systems of the premature infant. The external stresses of the ex utero environment also influence the pathophysiology of ROP through interactions among retinal neural, vascular, and glial cells. There is variability among individual infants and presentations of the disease throughout the world, making ROP challenging to study. The methods used include representative animal models, cell culture, and clinical studies. This article describes the impact of maternal-fetal interactions; stresses that the preterm infant experiences; and biologic pathways of interest, including growth factor effects and cell-cell interactions, on the complex pathophysiology of ROP phenotypes in developed and emerging countries.

Progress in Research on Stem Cells in Neonatal Refractory Diseases

With the development and progress of medical technology, the survival rate of premature and low-birth-weight infants has increased, as has the incidence of a variety of neonatal diseases, such as hypoxic-ischemic encephalopathy, intraventricular hemorrhage, bronchopulmonary dysplasia, necrotizing enterocolitis, and retinopathy of prematurity. These diseases cause severe health conditions with poor prognoses, and existing control methods are ineffective for such diseases. Stem cells are a special type of cells with self-renewal and differentiation potential, and their mechanisms mainly include anti-inflammatory and anti-apoptotic properties, reducing oxidative stress, and boosting regeneration. Their paracrine effects can affect the microenvironment in which they survive, thereby affecting the biological characteristics of other cells. Due to their unique abilities, stem cells have been used in treating various diseases. Therefore, stem cell therapy may open up the possibility of treating such neonatal diseases. This review summarizes the research progress on stem cells and exosomes derived from stem cells in neonatal refractory diseases to provide new insights for most researchers and clinicians regarding future treatments. In addition, the current challenges and perspectives in stem cell therapy are discussed.

Covert actions of growth hormone: fibrosis, cardiovascular diseases and cancer

Since its discovery nearly a century ago, over 100,000 studies of growth hormone (GH) have investigated its structure, how it interacts with the GH receptor and its multiple actions. These include effects on growth, substrate metabolism, body composition, bone mineral density, the cardiovascular system and brain function, among many others. Recombinant human GH is approved for use to promote growth in children with GH deficiency (GHD), along with several additional clinical indications. Studies of humans and animals with altered levels of GH, from complete or partial GHD to GH excess, have revealed several covert or hidden actions of GH, such as effects on fibrosis, cardiovascular function and cancer. In this Review, we do not concentrate on the classic and controversial indications for GH therapy, nor do we cover all covert actions of GH. Instead, we stress the importance of the relationship between GH and fibrosis, and how fibrosis (or lack thereof) might be an emerging factor in both cardiovascular and cancer pathologies. We highlight clinical data from patients with acromegaly or GHD, alongside data from cellular and animal studies, to reveal novel phenotypes and molecular pathways responsible for these actions of GH in fibrosis, cardiovascular function and cancer.

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%.

Comparison of before versus after intravitreal bevacizumab injection, growth factor levels and fibrotic markers in vitreous samples from patients with proliferative diabetic retinopathy

PURPOSE

In diabetic retinopathy patients, intravitreal bevacizumab (IVB) injections are widely used to facilitate dissection of retinal fibrovascular membranes during surgery, reduce the rate of perioperative hemorrhage, and prevent recurrent neovascularization. Previous studies have shown that IVB may worsen fibrosis and thereby impair vision. The aim of this study was to determine which markers are associated with fibrosis.

METHODS

Twenty-three patients with proliferative diabetic retinopathy (PDR) underwent pars plana vitrectomy (PPV) with IVB pretreatment for intraocular hemorrhage (IOH) and/or tractional retinal detachment (TRD). Vitreous samples were obtained at the time of IVB injection and again at the beginning of PPV, about a week later. Using Western blot analysis, the concentrations of vascular endothelial growth factor (VEGF), placental growth factor (PIGF), insulin like growth factor-1 (IGF-1), angiogenin-1 (Ang-1), and vascular endothelial cadherin (VE-cadherin) were measured in vitreous samples.

RESULTS

After treatment with IVB, VEGF, PIGF, and VE-cadherin concentrations in the vitreous significantly decreased (p < 0.001, p < 0.001, and p = 0.001, respectively), whereas the concentrations of IGF-1 increased (p = 0.001). There were no significant changes in Ang-1 concentrations in the vitreous after IVB injection (p = 0.732). There were no statistically significant differences in VEGF-A, PIGF, VE-cadherin, IGF, and Ang-1 levels before and after IVB injection when the IOH and TRD groups underwent subgroup analysis (p = 0.696, p = 0.516, p = 0.498, p = 0.188, and p = 0.243, respectively).

CONCLUSION

The levels of VEGF and other cytokines changed in the vitreous after IVB. The adverse effects associated with IVB, such as fibrosis, may result from modulation of vitreous cytokine concentrations. In the treatment of PDR, drugs that optimize the effects of PIGF, IGF-1, and VE-cadherin to reduce these side effects may be useful.

Dose Response of Bumetanide on Aquaporins and Angiogenesis Biomarkers in Human Retinal Endothelial Cells Exposed to Intermittent Hypoxia

Aquaporins (AQPs) are important for regulating cellular water, solute transport, and balance. Recently, AQPs have also been recognized as playing a key role in cell migration and angiogenesis. In the retina, hypoxia induces vascular endothelial growth factor (VEGF), a potent angiogenic and vascular permeability factor, resulting in retinal edema, which is facilitated by AQPs. Bumetanide is a diuretic agent and AQP 1–4 blocker. We tested the hypothesis that bumetanide suppression of AQPs ameliorates intermittent hypoxia (IH)-induced angiogenesis and oxidative stress in human microvascular retinal endothelial cells (HMRECs). HMRECs were treated with a low-dose (0.05 µg/mL) or high-dose (0.2 µg/mL) of bumetanide and were exposed to normoxia (Nx), hyperoxia (50% O₂), or IH (50% O₂ with brief hypoxia 5% O₂) for 24, 48, and 72 h. Angiogenesis and oxidative stress biomarkers were determined in the culture media, and the cells were assessed for tube formation capacity and AQP-1 and -4 expression. Both doses of bumetanide significantly decreased oxidative stress and angiogenesis biomarkers. This response was reflected by reductions in tube formation capacity and AQP expression. These findings confirm the role of AQPs in retinal angiogenesis. Therapeutic targeting of AQPs with bumetanide may be advantageous for IH-induced aberrant retinal development.

Retinal Phenotyping of Ferrochelatase Mutant Mice Reveals Protoporphyrin Accumulation and Reduced Neovascular Response

Purpose

Heme depletion, through inhibition of ferrochelatase (FECH), blocks retinal and choroidal neovascularization. Both pharmacologic FECH inhibition and a partial loss-of-function Fech mutation (Fech^m1Pas) are associated with decreased neovascularization. However, the ocular physiology of Fech^m1Pas mice under basal conditions has not been characterized. Here, we aimed to characterize the retinal phenotype of Fech^m1Pas mice.

Methods

We monitored retinal vasculature at postnatal day 17, 2 months, and 6 months in Fech^m1Pas homozygotes, heterozygotes, and their wild-type littermates. We characterized Fech substrate protoporphyrin (PPIX) fluorescence in the eye (excitation = 403 nm, emission = 628 nm), retinal function by electroretinogram, visual acuity by optomotor reflex, and retinal morphology by optical coherence tomography and histology. We stained vasculature using isolectin B4 and fluorescein angiography. We determined endothelial sprouting of retinal and choroidal tissue ex vivo and bioenergetics of retinal punches using a Seahorse flux analyzer.

Results

Fundi, retinal vasculature, venous width, and arterial tortuosity showed no aberrations. However, VEGF-induced retinal and choroidal sprouting was decreased in Fech^m1Pas mutants. Homozygous Fech^m1Pas mice had pronounced buildup of PPIX in the posterior eye with no damage to visual function, bioenergetics, and integrity of retinal layers.

Conclusions

Even with a buildup of PPIX in the retinal vessels in Fech^m1Pas homozygotes, the vasculature remains normal. Notably, stimulus-induced ex vivo angiogenesis was decreased in Fech^m1Pas mutants, consistent with reduced pathologic angiogenesis seen previously in neovascular animal models. Our findings indicate that Fech^m1Pas mice are a useful model for studying the effects of heme deficiency on neovascularization due to Fech blockade.

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.

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.

Increased Expression of Growth Hormone-Releasing Hormone in Fibrinous Inflammation of Proliferative Diabetic Retinopathy

PURPOSE

To investigate the involvement of growth hormone-releasing hormone (GHRH) - growth hormone (GH) signaling in pathogenesis of proliferative diabetic retinopathy (PDR).

DESIGN

Experimental laboratory study.

METHODS

Vitreous humor, aqueous humor, and serum were obtained from 36 eyes of 36 patients with or without type 2 diabetes from 2017 to 2019. For histologic examination, 6 fibrovascular membranes were excised from eyes with active PDR. Three fibrovascular membranes were excised from nondiabetic patients with proliferative vitreoretinopathy (PVR) as controls.

RESULTS

In PDR, the fibrovascular tissues consisted of a mature region containing fibrocytes, and an immature region populated by abundant polymorphonuclear leukocytes in a fibrinogen meshwork. Clusters of leukocytes were found adhering to the vascular walls. In PVR, no fibrinogen and polymorphonuclear leukocyte was observed in the fibrovascular membranes. The levels of GHRH and GH in PDR were significantly increased (P < .001), with 1.8-fold and 72.8-fold in vitreous humor, and 2-fold and 4.9-fold in aqueous humor, respectively, when compared with corresponding levels in controls. No significant difference was detected for insulin-like growth factor-1. Immunohistochemistry showed intense expression of GHRH and its receptor GHRH-R in polymorphonuclear leukocytes, vascular endothelial cells, and fibrocytes in fibrovascular membranes of PDR. GHRH staining was not detectable in infiltrating cells within the fibrovascular membrane of PVR.

CONCLUSIONS

These findings reveal a possible involvement of GHRH/GHRH-R in fibrinous inflammation that might contribute to the formation of fibrovascular membrane in PDR through mediating activities of leukocytes, vascular endothelial cells, and fibrocytes. Targeting GHRH/GHRH-R may be considered as a potential therapeutic approach for the treatment of PDR.

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.

Retinal Vasculature in Development and Diseases

The retina is one of the most metabolically active tissues in the body, consuming high levels of oxygen and nutrients. A well-organized ocular vascular system adapts to meet the metabolic requirements of the retina to ensure visual function. Pathological conditions affect growth of the blood vessels in the eye. Understanding the neuronal biological processes that govern retinal vascular development is of interest for translational researchers and clinicians to develop preventive and interventional therapeutics for vascular eye diseases that address early drivers of abnormal vascular growth. This review summarizes the current knowledge of the cellular and molecular processes governing both physiological and pathological retinal vascular development, which is dependent on the interaction among retinal cell populations, including neurons, glia, immune cells, and vascular endothelial cells. We also review animal models currently used for studying retinal vascular development.

Targeting growth hormone function: strategies and therapeutic applications

Human growth hormone (GH) is a classical pituitary endocrine hormone that is essential for normal postnatal growth and has pleiotropic effects across multiple physiological systems. GH is also expressed in extrapituitary tissues and has localized autocrine/paracrine effects at these sites. In adults, hypersecretion of GH causes acromegaly, and strategies that block the release of GH or that inhibit GH receptor (GHR) activation are the primary forms of medical therapy for this disease. Overproduction of GH has also been linked to cancer and the microvascular complications that are associated with diabetes. However, studies to investigate the therapeutic potential of GHR antagonism in these diseases have been limited, most likely due to difficulty in accessing therapeutic tools to study the pharmacology of the receptor in vivo. This review will discuss current and emerging strategies for antagonizing GH function and the potential disease indications.

Emerging therapies are offering an expanded toolkit for combatting the effects of human growth hormone overproduction. Human growth hormone (GH) is a major driver of postnatal growth; however, systemic or localized overproduction is implicated in the aberrant growth disease acromegaly, cancer, and diabetes. In this review, researchers led by Jo Perry, from the University of Auckland, New Zealand, discuss strategies that either inhibit GH production, block its systemic receptor, or interrupt its downstream signaling pathways. The only licensed GH receptor blocker is pegvisomant, but therapies are in development that include long-acting protein and antibody-based blockers, and nucleotide complexes that degrade GHR production have also shown promise. Studies investigating GHR antagonism are limited, partly due to difficulty in accessing therapeutic tools which block GHR function, but overcoming these obstacles may yield advances in alleviating chronic disease.

Inhibition of Aberrant IGF-I Signaling in Diabetic Male Rat Retina Prevents and Reverses Changes of Diabetic Retinopathy

Hyperglycemia results in inhibition of cleavage of integrin-associated protein (IAP) thereby allowing it to bind to SHPS-1 which results in pathophysiologic changes in endothelial function. This study determined if an anti-rat IAP antibody directed against the SHPS-1 binding site which disrupts IAP/SHPS-1 association could inhibit these pathophysiologic changes. The anti-IAP antibody inhibited IGF-I-stimulated SHPS-1, p52Shc, MAP kinase phosphorylation, and proliferation in endothelial cells. To determine if it could reverse established pathophysiologic changes in vivo, this antibody or normal rat IgG F(ab)2 was injected intraperitoneally for 6 weeks into rats that had diabetes for 4 weeks. Optical coherence tomography (OCT) showed that retinal thickness increased at 4 weeks and this increase was maintained in rats treated with the control antibody for an additional 6 weeks. The increase was reversed by anti-IAP antibody treatment (84.6 ± 2.0 compared to 92.3 ± 2.5 μm, p < 0.01). This value was similar to nondiabetic animals (82.2 ± 1.6 μm, p, NS). The anti-IAP antibody also decreased retinal vascular permeability (0.62 ± 0.12 vs. 0.96 ± 0.25%/g/h, p < 0.001). To determine if it was effective after local injection, this antibody or control was administered via intravitreal injection. After 3 weeks, retinal thickness increased to 6.4 ± 2.8% in diabetic rats, and IAP antibody treatment prevented this increase (0.8 ± 2.5%, p < 0.01). It also prevented the increase of retinal vascular permeability (0.92 ± 0.62 vs. 1.63 ± 0.99%/g/h, p < 0.001). Biochemical analyses of retinal extracts showed that the anti-IAP antibody inhibited IAP/SHPS-1 association and SHPS-1 phosphorylation. This resulted in inhibition of AKT activation and VEGF synthesis in the retina: changes associated with increased vascular permeability. We conclude the anti-rat IAP antibody disrupts IAP/SHPS-1 association and attenuates aberrant IGF-I signaling thereby preventing or reversing the progression of retinal pathophysiological changes.

Pediatric Eales Disease: An Indian Tertiary Eye Center Experience

PURPOSE

To report the clinical profiles, etiologies, treatment modalities, and outcomes for Eales disease in patients younger than age 16 years in India.

METHODS

Retrospective review of medical records of patients with Eales disease who had a minimum 5-year follow-up period.

RESULTS

A total of 25 eyes of 13 patients were included. Of these 13 patients, 12 (94%) had bilateral Eales disease and 11 (84.6%) were men. Mean patient age was 14.1 years (range: 11 to 16 years). Diminution of vision (36%) was the most common presenting complaint, followed by both diminutions of vision and floaters (32%). Sclerosed vessels were seen in all eyes, and 21 (84%) eyes had active periphlebitis at presentation. Neovascularization elsewhere was seen in 20 (80%) eyes and neovascularization of the optic disc was seen in 1 (4%) eye. Veno-venous shunts were found in 12 (48%) eyes, and 18 (72%) eyes had vitreous hemorrhage. All eyes received photocoagulation; 84.6% of patients received oral steroids, with 7.7% of patients treated with azathioprine and 38.4% treated with anti-tubercular therapy. Vitrectomy was performed in 36% of eyes for non-clearing vitreous hemorrhage and tractional retinal detachment. Vision improved in 7 (28%) eyes, was stable in 12 (48%) eyes, and worsened in 6 (24%) eyes. Recurrence of the disease more than five times during the 5-year follow-up period occurred in 20% of patients.

CONCLUSIONS

Recurrent vasculitis and vitreous hemorrhage in children should raise the suspicion of pediatric Eales disease. [J Pediatr Ophthalmol Strabismus. 2018;55(4):270-274.].

Mini-peptide RPL41 attenuated retinal neovascularization by inducing degradation of ATF4 in oxygen-induced retinopathy mice

Endoplasmic reticulum (ER) stress signaling is activated in retinal degeneration disease. Activating transcription factor 4 (ATF4), an important mediator of the unfolded protein response (UPR), is a key element that maintains cell survival and proliferation in hypoxic conditions. Our previous studies showed that a small ribosomal protein L41 (RPL41) inhibits ATF4 by inducing its phosphorylation and degradation. In the present study, the effects of mini-peptide RPL41 on retinal neovascularization (RNV) in oxygen-induced retinopathy (OIR) mice was investigated. We induced OIR in C57BL/6 mice and obtained retinas from normoxia, OIR, OIR control (treated with PBS), and OIR treated (treated with RPL41) mice. Our results showed that ER stress signaling was activated and ATF4 was overexpressed in the retinas of OIR mice. After intravitreal injection of RPL41, the size of RNV and vaso-obliteration, and the number of preretinal neovascular cell nuclei in the retinas of OIR mice were significantly decreased. Western blot analysis and quantitative real-time polymerase chain reaction (qPCR) showed ATF4 and VEGF expression decreased after intravitreal injection of RPL41. Furthermore, the expression levels of inflammatory genes including TNF-α, IL-1β, and IL-6 were significantly decreased compared with the OIR control mice. In conclusion, RPL41 prevented pathologic neovascularization and exerted anti-inflammatory effects by degrading the important ER stress factor ATF4, thus, RPL41 could be a promising therapeutic agent for the treatment of neovascular eye diseases, especially retinopathy of prematurity (ROP).

Systemic Inflammation-Associated Proteins and Retinopathy of Prematurity in Infants Born Before the 28th Week of Gestation

Purpose

To assess the association between systemic levels of inflammation-associated proteins and severe retinopathy of prematurity (ROP) in extremely preterm infants.

Methods

We collected whole blood on filter paper on postnatal days 1, 7, 14, 21, and 28 from 1205 infants born before the 28th week of gestation, and measured the concentrations of 27 inflammation-associated, angiogenic, and neurotrophic proteins. We calculated odds ratios with 95% confidence intervals for the association between top quartile concentrations of each protein and prethreshold ROP.

Results

During the first three weeks after birth, high concentrations of VEGF-R1, myeloperoxidase (MPO), IL-8, intercellular adhesion molecule (ICAM)-1, matrix metalloproteinase 9, erythropoietin, TNF-α, and basic fibroblast growth factor were associated with an increased risk for prethreshold ROP. On day 28, high levels of serum amyloid A, MPO, IL-6, TNF-α, TNF-R1/-R2, IL-8, and ICAM-1 were associated with an increased risk. Top quartile concentrations of the proinflammatory cytokines TNF-α and IL-6 were associated with increased risks of ROP when levels of neuroprotective proteins and growth factors, including BDNF, insulin-like growth factor 1, IGFBP-1, VEGFR-1 and -2, ANG-1 and PlGF, were not in the top quartile. In contrast, high concentrations of NT-4 and BDNF appeared protective only in infants without elevated inflammatory mediators.

Conclusions

Systemic inflammation during the first postnatal month was associated with an increased risk of prethreshold ROP. Elevated concentrations of growth factors, angiogenic proteins, and neurotrophins appeared to modulate this risk, and were capable of reducing the risk even in the absence of systemic inflammation.

What is next after anamorelin?

PURPOSE OF REVIEW

In spite of its relevance, treatments for the cancer anorexia and cachexia syndrome (CACS) are not available. One of the agents that recently reached phase III clinical trials is anamorelin. Its development, along with that of other agents for this indication, will be reviewed here, with a focus on the gaps in the current knowledge and future directions.

RECENT FINDINGS

In spite of several targets showing promising results in early development, their difficulties obtaining regulatory approval underscore the need to reconsider the current strategies in drug development and the challenges in the field of CACS.

SUMMARY

Further research is needed in order to meet the challenges of developing treatments for CACS. Preclinical studies should expand our understanding about key regulators of appetite, muscle, and energy metabolism in this setting using models that can be translated reliably to humans. Clinical research efforts should focus on validating the entry criteria, endpoints, outcomes, and the potential synergistic effects and interaction between different targets, nutrition, and exercise interventions. Clinical meaningfulness and significance should be taken into account in the design of clinical trials. It is essential that all key stakeholders are included in the design of future strategies.

A predictive score for retinopathy of prematurity by using clinical risk factors and serum insulin-like growth factor-1 levels

AIM

To detect the impact of insulin-like growth factor-1 (IGF-1) and other risk factors for the early prediction of retinopathy of prematurity (ROP) and to establish a scoring system for ROP prediction by using clinical criteria and serum IGF-1 levels.

METHODS

The study was conducted with 127 preterm infants. IGF-1 levels in the 1^st day of life, 1^st, 2^nd, 3^rd and 4^th week of life was analyzed. The score was established after logistic regression analysis, considering the impact of each variable on the occurrences of any stage ROP. A validation cohort containing 107 preterm infants was included in the study and the predictive ability of ROP score was calculated.

RESULTS

Birth weights (BW), gestational weeks (GW) and the prevalence of breast milk consumption were lower, respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD) and necrotizing enterocolitis (NEC) were more frequent, the duration of mechanical ventilation and oxygen supplementation was longer in patients with ROP (P<0.05). Initial serum IGF-1 levels tended to be lower in newborns who developed ROP. Logistic regression analysis revealed that low BW (<1250 g), presence of intraventricular hemorrhage (IVH) and formula feeding increased the risk of ROP. Afterwards, the scoring system was validated on 107 infants. The negative predictive values of a score less than 4 were 84.3%, 74.7% and 79.8% while positive predictive values were 76.3%, 65.5% and 71.6% respectively.

CONCLUSION

In addition to BW <1250 g and IVH, formula consumption was detected as a risk factor for the development of ROP. Breastfeeding is important for prevention of ROP in preterm infants.

Gene expression levels of the insulin-like growth factor family in patients with AMD before and after ranibizumab intravitreal injections

Purpose

The present study focused on the assessment of the mRNA levels of the insulin-like growth factor (IGF) family in patients with the exudative form of age-related macular degeneration (AMD) before and after ranibizumab intravitreal injections.

Patients and methods

An analysis of the expression profile of the IGF family of genes in patients with AMD was carried out using the oligonucleotide microarray and quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) methods.

Results

In the peripheral blood mononuclear cells (PBMCs) obtained from AMD group receiving ranibizumab compared to the peripheral blood mononuclear cells from AMD group before ranibizumab treatment using oligonucleotide microarray technique, six statistically significant differentially expressed transcripts related to the IGF family were detected (unpaired t-test, p<0.05, fold change >1.5). Moreover, analysis using the real-time RT-qPCR technique revealed statistically significant differences in the IGF2 and IGF2R mRNA levels (Mann–Whitney U test, p<0.05) between the two groups that were studied. Statistical analyses of both oligonucleotide microarray and real-time RT-qPCR results demonstrated a significant decreased expression only for IGF2 mRNA.

Conclusion

Our results revealed a changed expression of IGF2 mRNA after ranibizumab treatment.

Choroidal thickness measurements in children with isolated growth hormone deficiency

PurposeThe aim of this study was to determine the choroidal thickness measurement values in cases with isolated growth hormone deficiency (IGHD), to compare them with the healthy control group by using enhanced depth imaging optical coherence tomography (EDI-OCT), and to evaluate the effect of growth hormone (GH) treatment on choroid.Patients and methodsIn this study, 23 cases who were diagnosed with IGHD as a study group and 46 healthy subjects as a control group were included. All patients and controls underwent a complete ophthalmologic examination, including an examination with EDI-OCT. Choroidal thickness (CT) was measured at the fovea and at 1000 μm intervals from the foveal center in both temporal and nasal directions.ResultsThe mean subfoveal choroidal thickness (SFCT) was 329.04±88.49 μm in the cases with IGHD and 365.35±50.48 μm in the control group (P=0.033). The mean CT at temporal 1 and 2 mm were thinner in the IGHD group than that of control group (P=0.033 and P=0.043, respectively). Nasal quadrant measurements were also found to be thinner in the IGHD cases than that of control group, but the difference was not statistically significant. We found a significant positive correlation between pubertal staging and SFCT (r_s=0.607, P=0.006). There was no statistically significant difference in CT values of the study group between before and 12 months after GH treatment (P>0.05).ConclusionThis study shows patients with IGHD has a thinner CT when compared with healthy pediatric cases. GH treatment seems to be not associated with the choroidal development.

Retinal and choroidal angiogenesis: a review of new targets

Retinal and choroidal neovascularization are a major cause of significant visual impairment, worldwide. Understanding the various factors involved in the accompanying physiopathology is vital for development of novel treatments, and most important, for preserving patient vision. The intraocular use of anti-vascular endothelial growth factor therapeutics has improved management of the retinal and choroidal neovascularization but some patients do not respond, suggesting other vascular mediators may also contribute to ocular angiogenesis. Several recent studies examined possible new targets for future anti-angiogenic therapies. Potential targets of retinal and choroidal neovascularization therapy include members of the platelet-derived growth factor family, vascular endothelial growth factor sub-family, epidermal growth factor family, fibroblast growth factor family, transforming growth factor-β superfamily (TGF-β1, activins, follistatin and bone morphogenetic proteins), angiopoietin-like family, galectins family, integrin superfamily, as well as pigment epithelium derived factor, hepatocyte growth factor, angiopoietins, endothelins, hypoxia-inducible factors, insulin-like growth factors, cytokines, matrix metalloproteinases and their inhibitors and glycosylation proteins. This review highlights current antiangiogenic therapies under development, and discusses future retinal and choroidal pro- and anti-angiogenic targets as wells as the importance of developing of new drugs.

Impact of minocycline on vascularization and visual function in an immature mouse model of ischemic retinopathy

The role of microglia in the pathophysiology of ischemic retinal diseases has been extensively studied. Retinal microglial activation may be correlated with retinal neovascularization in oxygen-induced retinopathy (OIR), an animal model that has been widely used in retinopathy of prematurity (ROP) research. Minocycline is an antibiotic that decreases microglial activation following hyperoxic and hypoxic-ischemic phases in neonatal rodents. Here, we investigated the effects of minocycline on vascularization and visual function. In our results, we found that after the administration of minocycline, microglial reactivity was reduced in the retina, which was accompanied by an increase in the avascular area at P12, P14 and P17. Although microglial reactivity was reduced at P17, minocycline treatment did not attenuate retinal neovascularization. A changing trend in microglial number was observed, and the apoptosis and proliferation states on different days partly contributed to this change. Further study also revealed that although minocycline downregulated the levels of proinflammatory factors, visual function appeared to be significantly worsened. Collectively, we demonstrated that minocycline disturbed the physiological vascularization of the avascular area and exacerbated visual dysfunction, indicating that minocycline may not be an effective drug and may even be detrimental for the treatment of ischemic retinopathy in immature mammals.

Advances in understanding and management of retinopathy of prematurity

The understanding, diagnosis, and treatment of retinopathy of prematurity have changed in the 70 years since the original description of retrolental fibroplasia associated with high oxygenation. It is now recognized that retinopathy of prematurity differs in appearance worldwide and as ever smaller and younger premature infants survive. New methods are being evaluated to image the retina, diagnose severe retinopathy of prematurity, and determine windows of time for treatment to save eyes and improve visual and neural outcomes. New treatments to promote physiologic retinal vascular development, vascular repair, and inhibit vasoproliferation by regulating proteins involved in vascular endothelial growth factor, insulin-like growth factor, or erythropoietin signaling. Reducing excessive oxidative/nitrosative stress and understanding progenitor cells and neurovascular and glial vascular interactions are being studied.

Growth hormone modulates in vitro endothelial cell migration and formation of capillary-like structures

The generation of new blood vessels is a complex process mediated by a variety of growth factors, and the growth hormone (GH) has been shown to act as a proangiogenic factor. In fact, human GH deficiency or excess are associated with endothelial dysfunction. Moreover, mouse models have revealed the action of GH in both tissue repair and in the microvascular circulation of normal tissues. In this study, we investigated the in vitro effects of GH on endothelial cells. Using a murine endothelioma cell line (tEnd.1), we demonstrated that GH has a mitogenic effect. The hormone also affected the endothelial cellular morphology and augmented the deposition of the extracellular matrix molecules, laminin, and fibronectin, on tEnd.1 surface. GH could stimulate tEnd.1 cell fugetaxis, in transwell chambers migration assay, and increased the formation of capillary-like structures in Matrigel®-coated plates. Given the important role of angiogenesis during tissue injury, for example, at ischemic lesions, these findings shed light on therapeutic angiogenesis, particularly in pathologies where the cardiovascular system has been compromised.

Pegvisomant: a growth hormone receptor antagonist used in the treatment of acromegaly

PURPOSE

To review published data on pegvisomant and its therapeutic role in acromegaly.

METHODS

Electronic searches of the published literature were conducted using the keywords: acromegaly, growth hormone (GH) receptor (antagonist), pegvisomant, therapy. Relevant articles (n = 141) were retrieved and considered for inclusion in this manuscript.

RESULTS

Pegvisomant is a genetically engineered, recombinant growth hormone receptor antagonist, which is effective in normalizing serum insulin-like growth factor 1 (IGF-1) levels in the majority of patients with acromegaly and ameliorating symptoms and signs associated with GH excess. Pegvisomant does not have direct antiproliferative effects on the underlying somatotroph pituitary adenoma, which is the etiology of GH excess in the vast majority of patients with acromegaly. Therefore, patients receiving pegvisomant monotherapy require regular pituitary imaging in order to monitor for possible increase in tumor size. Adverse events in patients on pegvisomant therapy include skin rashes, lipohypertrophy at injection sites, and idiosyncratic liver toxicity (generally asymptomatic transaminitis that is reversible upon drug discontinuation), thus necessitating regular patient monitoring.

CONCLUSIONS

Pegvisomant is an effective therapeutic agent in patients with acromegaly who are not in remission after undergoing pituitary surgery. It mitigates excess GH action, as demonstrated by IGF-1 normalization, but has no direct effects on pituitary tumors causing acromegaly. Regular surveillance for possible tumor growth and adverse effects (hepatotoxicity, skin manifestations) is warranted.

Review of the mechanisms and therapeutic avenues for retinal and choroidal vascular dysfunctions in retinopathy of prematurity

Retinopathy of prematurity (ROP) is a multifactorial disease and the main cause of visual impairment and blindness in premature neonates. The inner retina has been considered the primary region affected in ROP, but choroidal vascular degeneration and progressive outer retinal dysfunctions have also been observed. This review focuses on observations regarding neurovascular dysfunctions in both the inner and outer immature retina, the mechanisms and the neuronal-derived factors implicated in the development of ROP, as well potential therapeutic avenues for this disorder.

CONCLUSION

Alterations in the neurovascular integrity of the inner and outer retina contribute to the development of ROP.

Expanded criteria for retinopathy of prematurity screening in moderately preterm infants: Single-center pilot study

BACKGROUND

While developed countries seek to lower the gestational age and birthweight parameters in retinopathy of prematurity (ROP) screening, older, larger infants still develop ROP in other parts of the world. The aim of this study was therefore to define criteria to identify potential ROP developers who are outliers of the common screening range.

METHODS

A retrospective medical record review was performed in 147 inborn moderately preterm infants admitted to the neonatal intensive care unit during the study period. Univariate and logistic regression analysis was carried out.

RESULTS

Forty-two infants developed ROP. Gestational age (31.4 ± 1.1 vs 32.4 ± 1.0 weeks, P = 0.000) and birthweight (1607.7 ± 339.4 vs 1846.4 ± 317.2 g, P = 0.000) were lower in those who developed ROP. Respiratory distress syndrome (P = 0.026) and documented sepsis (P = 0.003) were significant comorbidities on univariate analysis. Inotrope need >72 h starting in the first week of life (P = 0.004; OR, 5.181) and more than three transfusions of packed red blood cells (P = 0.028; OR, 3.891) were also significant, both on univariate and multivariate analysis.

CONCLUSIONS

In moderately preterm infants, status should be evaluated in order to effectively select candidates for ROP screening without missing potential ROP developers.

IGF-1 in retinopathy of prematurity, a CNS neurovascular disease

The retina is part of the central nervous system and both the retina as well as the brain can suffer from severe damage after very preterm birth. Retinopathy of prematurity is one of the major causes of blindness in these children and brain neuronal impairments including cognitive defects, cerebral palsy and intraventricular hemorrhage (IVH) are also complications of very preterm birth. Insulin-like growth factor 1 (IGF-1) acts to promote proliferation, maturation, growth and survival of neural cells. Low levels of circulating IGF-1 are associated with ROP and defects in the IGF-1 gene are associated with CNS disorders including learning deficits and brain growth restriction. Treatment of preterm infants with recombinant IGF-1 may potentially prevent ROP and CNS disorders. This review compares the role of IGF-1 in ROP and CNS disorders. A recent phase 2 study showed a positive effect of IGF-1 on the severity of IVH but no effect on ROP. A phase 3 trial is planned.

IGF-I in the clinics: Use in retinopathy of prematurity

Retinopathy of prematurity is a potentially blinding disease, which is associated with low neonatal IGF-I serum concentrations and poor growth. In severe cases impaired retinal vessel growth is followed by pathologic neovascularization, which may lead to retinal detachment. IGF-I may promote growth even in catabolic states. Treating preterm infants with recombinant human (rh) IGF-I to concentrations normally found during gestation has been suggested to have a preventative effect on ROP. A recent phase 2 study treating infants (gestational age between 23weeks+0days and 27weeks +6days) with rhIGF-I/IGF binding protein-3 until 30 postmenstrual weeks showed no effect on ROP but a 53% reduction in severe bronchopulmonary dysplasia and 44% reduction in severe intraventricular hemorrhage. Oxygen is a major risk factor for ROP and during the phase 2 study oxygen saturation targets were increased to 90-95%, due to national guidelines, which might have affected ROP rate and severity making increased IGF-I a weaker preventative factor for ROP.

Growth hormone and ocular dysfunction: Endocrine, paracrine or autocrine etiologies?

The eye is a target site for GH action and growth hormone has been implicated in diabetic retinopathy and other ocular dysfunctions. However, while this could reflect the hypersecretion of pituitary GH, the expression of the GH gene is now known to occur in ocular tissues and it could thus also reflect excess GH production within the eye itself. The possibility that ocular dysfunctions might arise from endocrine, autocrine or paracrine etiologies of GH overexpression is therefore the focus of this brief review.

Tat PTD-Endostatin-RGD: A novel protein with anti-angiogenesis effect in retina via eye drops

BACKGROUND

Diabetic retinopathy is a leading cause of blindness. The objective was to design a novel fusion protein, Tat PTD-Endostatin-RGD, to treat retinal neovascularization via eye drops instead of traditional intravitreal injection trepapeutical methods.

METHOD

The anti-angiogenesis ability was evaluated in vitro by chick embryo chorioallantoic membrane assay, wound healing assay and tube formation assay. Corneal barrier and blood-retina barrier were constructed in vitro to investigate the penetration ability of Tat PTD-Endostatin-RGD. Western blot was used to detect the integrin αvβ3 expression level in rat retina microvascular endothelial cells which was stimulated by S-nitroso-N-acetylpenicillamine. The binding affinity of Tat PTD-Endostatin-RGD to integrin αvβ3 was investigated by evaluating the penetration ability on blood-retina barriers treated with S-nitroso-N-acetylpenicillamine. The pharmacodynamics and efficacy analysis were further carried out in the oxygen-induced retinopathy model in vivo. In addition, the pharmacokinetic profile via eye drops was studied on a C57BL/6 mice model.

RESULT

Tat PTD-Endostatin-RGD showed high anti-angiogenesis activity and high ability to penetrate these two barriers in vitro. The Western blot results indicated S-nitroso-N-acetylpenicillamine upregulated the expression level of integrin αvβ3 in a dose-dependent manner. Tat PTD-Endostatin-RGD showed a high affinity to rat retina microvascular endothelial cells treated with S-nitroso-N-acetylpenicillamine. The results showed that Tat PTD-Endostatin-RGD could inhibit abnormal angiogenesis in retina via eye drops.

CONCLUSION

Tat PTD-Endostatin-RGD showed high penetration ability through ocular barriers, bound specifically to integrin αvβ3 and effectively inhibited the abnormal angiogenesis.

GENERAL SIGNIFICANCE

Tat PTD-Endostatin-RGD represents a potent novel drug applied via eye drops for fundus oculi neovascularization diseases.

Retinopathy of prematurity: the need for prevention

More than 450,000 babies are born prematurely in the USA every year. The improved survival of even the most vulnerable low body weight preterm infants has, despite improving health outcomes, led to the resurgence in preterm complications including one of the major causes for blindness in children, retinopathy of prematurity (ROP). The current mainstay in ROP therapy is laser photocoagulation and the injection of vascular endothelial growth factor (VEGF) antibodies in the late stages of the disease after the onset of neovascularization. Both are proven options for ophthalmologists to treat the severe forms of late ROP. However, laser photocoagulation destroys major parts of the retina, and the injection of VEGF antibodies, although rather simple to administer, may cause a systemic suppression of normal vascularization, which has not been studied in sufficient depth. However, the use of neither VEGF antibody nor laser treatment prevents ROP, which should be the long-term goal. It should be possible to prevent ROP by more closely mimicking the intrauterine environment after preterm birth. Such preventive measures include preventing the toxic postbirth influences (eg, oxygen excess) as well as providing the missing intrauterine factors (eg, insulin growth factor 1) and are likely to also reduce other complications of premature birth as well as ROP. This review is meant to summarize the current knowledge on the prevention of ROP with a particular emphasize on the use of insulin growth factor 1 supplementation.

Effect of Guibi-Tang, a Traditional Herbal Formula, on Retinal Neovascularization in a Mouse Model of Proliferative Retinopathy

Ocular pathologic angiogenesis is an important causative risk factor of blindness in retinopathy of prematurity, proliferative diabetic retinopathy, and neovascular macular degeneration. Guibi-tang (GBT) is a frequently used oriental herbal formula in East Asian countries, and is also called Qui-pi-tang in Chinese and Kihi-To in Japanese. In the present study, we investigated the preventive effect of GBT on retinal pathogenic neovascularization in a mouse model of oxygen-induced retinopathy (OIR). C57BL/6 mice were exposed to 75% hyperoxia for five days on postnatal day 7 (P7). The mice were then exposed to room air from P12 to P17 to induce ischemic proliferative retinopathy. GBT (50 or 100 mg/kg/day) was intraperitoneally administered daily for five days (from P12 to P16). On P17, Retinal neovascularization was measured on P17, and the expression levels of 55 angiogenesis-related factors were analyzed using protein arrays. GBT significantly decreased retinal pathogenic angiogenesis in OIR mice, and protein arrays revealed that GBT decreased PAI-1 protein expression levels. Quantitative real-time PCR revealed that GBT reduced vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), and plasminogen activator inhibitor 1 (PAI-1) mRNA levels in OIR mice. GBT promotes potent inhibitory activity for retinal neovascularization by decreasing VEGF, FGF2, and PAI-1 levels.

Therapeutic uses of somatostatin and its analogues: Current view and potential applications

Somatostatin is an endogeneous cyclic tetradecapeptide hormone that exerts multiple biological activities via five ubiquitously distributed receptor subtypes. Classified as a broad inhibitory neuropeptide, somatostatin has anti-secretory, anti-proliferative and anti-angiogenic effects. The clinical use of native somatostatin is limited by a very short half-life (1 to 3min) and the broad spectrum of biological responses. Thus stable, receptor-selective agonists have been developed. The majority of these somatostatin therapeutic agonists bind strongly to two of the five receptor subtypes, although recently an agonist of wider affinity has been introduced. Somatostatin agonists are established in the treatment of acromegaly with recently approved indications in the therapy of neuroendocrine tumours. Potential therapeutic uses for somatostatin analogues include diabetic complications like retinopathy, nephropathy and obesity, due to inhibition of IGF-1, VEGF together with insulin secretion and effects upon the renin-angiotensin-aldosterone system. Wider uses in anti-neoplastic therapy may also be considered and recent studies have further revealed anti-inflammatory and anti-nociceptive effects. This review provides a comprehensive, current view of the biological functions of somatostatin and potential therapeutic uses, informed by the wide range of pharmacological advances reported since the last published review in 2004 by P. Dasgupta. The pharmacology of somatostatin receptors is explained, the current uses of somatostatin agonists are discussed, and the potential future of therapeutic applications is explored.

Transplantation of Human Neural Progenitor Cells Expressing IGF-1 Enhances Retinal Ganglion Cell Survival

We have previously characterized human neuronal progenitor cells (hNP) that can adopt a retinal ganglion cell (RGC)-like morphology within the RGC and nerve fiber layers of the retina. In an effort to determine whether hNPs could be used a candidate cells for targeted delivery of neurotrophic factors (NTFs), we evaluated whether hNPs transfected with an vector that expresses IGF-1 in the form of a fusion protein with tdTomato (TD), would increase RGC survival in vitro and confer neuroprotective effects in a mouse model of glaucoma. RGCs co-cultured with hNP^IGF-TD cells displayed enhanced survival, and increased neurite extension and branching as compared to hNP^TD or untransfected hNP cells. Application of various IGF-1 signaling blockers or IGF-1 receptor antagonists abrogated these effects. In vivo, using a model of glaucoma we showed that IOP elevation led to reductions in retinal RGC count. In this model, evaluation of retinal flatmounts and optic nerve cross sections indicated that only hNP^IGF-TD cells effectively reduced RGC death and showed a trend to improve optic nerve axonal loss. RT-PCR analysis of retina lysates over time showed that the neurotrophic effects of IGF-1 were also attributed to down-regulation of inflammatory and to some extent, angiogenic pathways. This study shows that neuronal progenitor cells that hone into the RGC and nerve fiber layers may be used as vehicles for local production and delivery of a desired NTF. Transplantation of hNP^IGF-TD cells improves RGC survival in vitro and protects against RGC loss in a rodent model of glaucoma. Our findings have provided experimental evidence and form the basis for applying cell-based strategies for local delivery of NTFs into the retina. Application of cell-based delivery may be extended to other disease conditions beyond glaucoma.

Glycemic variability and diabetes retinopathy: a missing link

Daily glucose variability, such as fasting plasma glucose fluctuation or postprandial hyperglycemia, has been proposed as contributors to diabetes-related macrovascular complications. However, its impacts on microvascular complications, such as diabetes retinopathy remain controversial. We reviewed the current evidence of the relationship between glycemic variability and diabetes retinopathy in patients with type 1 or type 2 diabetes. In general, the short-term glycemic fluctuation, either expressed as standard deviation of fasting glucose or mean glucose levels, may contribute to the development or progression of diabetic retinopathy in patients with type 2 diabetes, whereas long-term glycemic fluctuation, reflected by variation of levels of HbA1c, appeared to show a stronger association with diabetes retinopathy both in patients with type 1 and type 2 diabetes. These findings emphasize the need to reduce glycemic variability by various measures in order to reduce development and progression of diabetes retinopathy both in type 1 and type 2 diabetes patients.

Bone morphogenetic protein 2: a potential new player in the pathogenesis of diabetic retinopathy

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus. Vision loss in DR principally occurs due to breakdown of the blood-retinal barrier (BRB), leading to macular edema, retinal detachment and inner retinal and vitreous hemorrhage. Several growth factors have been shown to play crucial role in the development of these vascular changes; however, the cellular and molecular mechanisms of DR are not yet fully revealed. In the current study we investigated the role of bone morphogenetic protein-2 (BMP2) in DR. We examined the changes in the protein levels of BMP2 in human vitreous and retina in addition to the mouse retina of streptozotocin-induced diabetes. To detect the source of BMP2 during diabetes, human retinal endothelial cells (hRECs) were subjected to high glucose (HG) for 5 days and levels of BMP2 protein were analyzed in conditioned media of these cells relative to control. We also evaluated the effect of BMP2 on the levels of VEGF in cultured rat Müller cells (rMC1). In addition, we tested the pro-inflammatory effects of BMP2 by examining its effect on leukocyte adhesion to cultured hRECs, and levels of adhesion molecules and cytokines production. Finally, the effect of different concentrations of BMP2 on permeability of confluent monolayer of hRECs was evaluated using FITC-Dextran flux permeability assay and by measuring Transcellular Electrical Resistance (TER) using Electric Cell-substrate Impedance Sensing (ECIS). Our results show, for the first time, the up-regulation of BMP2 in diabetic human and mouse retinas in addition to its detection in vitreous of patients with proliferative DR (72 ± 7 pg/ml). In vitro, hRECs showed upregulation of BMP2 in HG conditions suggesting that these cells are a potential source of BMP2 in diabetic conditions. Furthermore, BMP2 induced VEGF secretion by Müller cells in-vitro; and showed a dose response in increasing permeability of cultured hRECs. Meanwhile, BMP2 pro-inflammatory effects were recognized by its ability to induce leukocyte adhesion to the hRECs, intercellular adhesion molecule-1 (ICAM-1) and upregulation of interleukin-6 and 8 (IL-6 and IL-8). These results show that BMP2 could be a contributing growth factor to the development of microvascular dysfunction during DR via enhancing both pro-angiogenic and inflammatory pathways. Our findings suggest BMP2 as a potential therapeutic target to prevent/treat DR.

Somatostatin and diabetic retinopathy: current concepts and new therapeutic perspectives

Somatostatin (SST) is abundantly produced by the human retina, and the main source is the retinal pigment epithelium (RPE). SST exerts relevant functions in the retina (neuromodulation, angiostatic, and anti-permeability actions) by interacting with SST receptors (SSTR) that are also expressed in the retina. In the diabetic retina, a downregulation of SST production does exist. In this article, we give an overview of the mechanisms by which this deficit of SST participates in the main pathogenic mechanisms involved in diabetic retinopathy (DR): neurodegeneration, neovascularization, and vascular leakage. In view of the relevant SST functions in the retina and the reduction of SST production in the diabetic eye, SST replacement has been proposed as a new target for treatment of DR. This could be implemented by intravitreous injections of SST analogs or gene therapy, but this is an aggressive route for the early stages of DR. Since topical administration of SST has been effective in preventing retinal neurodegeneration in STZ-induced diabetic rats, it seems reasonable to test this new approach in humans. In this regard, the results of the ongoing clinical trial EUROCONDOR will provide useful information. In conclusion, SST is a natural neuroprotective and antiangiogenic factor synthesized by the retina which is downregulated in the diabetic eye and, therefore, its replacement seems a rational approach for treating DR. However, clinical trials will be needed to establish the exact position of targeting SST in the treatment of this disabling complication of diabetes.

Growth hormone replacement in patients with PHACE association and hypopituitarism

Partially empty sella with growth hormone (GH) deficiency is rarely reported in association with PHACE (posterior fossa anomalies, cervicofacial infantile hemangiomas [IHs], arterial anomalies, cardiac defects, eye anomalies, and midline/ventral defects). Consequently, little is known about the effect of GH replacement on the proliferation and involution of IHs in children with PHACE. We describe two children with PHACE and partially empty sella, both of whom received GH replacement for treatment of hypopituitarism. In our first patient we observed erythema and prominence of the vasculature in the hemangioma shortly after initiation of therapy at age 20 months, although after 4 weeks of treatment the appearance of the hemangioma stabilized and little change was seen during eight additional years of therapy. In our second patient we noted enlargement of the hemangioma after starting low-dose GH at age 5 years, prompting discontinuation of GH replacement after 3 months of therapy. The hemangiomas continued to grow after discontinuation of GH treatment. GH administration in our patients was associated with erythema and prominence of IHs. Our findings suggest that GH replacement therapy may promote transient or more prolonged proliferation of IHs and should be administered with close clinical monitoring.

TGF-β1 and IGF-I gene variations in type 1 diabetes microangiopathic complications

Background

Growth factors are generally believed to have a perpetuating role in the development of diabetic complications, However there is ample of evidence of a protective or therapeutic potential for some of them. IGF-I, according to some reports, may contribute to complication development, although a protective role for IGF-I has been claimed for all late diabetic complications, making it an exception among growth factors. Transforming growth factor (TGF)-β1 as a pleiotropic cytokine is a key player in immunoregulation. Dysregulation of TGF-β1 in diabetes has been addressed as a leading event of kidney pathologies, while there is no similar pivotal role for TGF-β1 in diabetic retinopathy or neuropathy. An association study was conducted to evaluate the distinctive roles of TGF-β1 and IGF-I in T1DM microvascular complications by gene variation-based regulatory mechanisms that are operational in modulation of both in situ and systemic levels of the gene product.

Methods

Two polymorphisms of the IGF-I gene at positions −383*C/T and −1089*C/T and two functional TGF-β1 gene polymorphisms, including codons 10 (+869*C/T) and 25 (+915*G/C) were examined in 248 British Caucasian T1DM patients and 113 healthy controls.

Results

The distribution of IGF-1 gene polymorphisms did not reflect any significant association with different endpoints among the cases or different subgroups (complication triad) and controls. For TGF-β1 gene codon 25 polymorphism the low producer variant (allele C) were more frequent in cases than controls, which is compatible with the anti-inflammatory role of TGF-β1 and for codon 10 polymorphism the frequency of allele C was highest in retinopaths and, on the contrary and expectedly, nephropathy was more frequently accompanied by allele T (high producer). The frequency of allele G (high producer) of codon 25 polymorphism was slightly higher in the complication free group than in other subgroups.

Conclusion

Although there were some differences in distribution of allele and genotype frequencies of TGF-β1 gene polymorphism in diabetes microvascular complications the differences were not statistically significant. Regarding IGF-1 our result firstly questions the functionality of the employed polymorphic marker and secondly may entail that the main regulator of IGF-I functionality resides elsewhere rather than the IGF-I gene itself, such as post-transcriptional regulation.

Targeting Neovascularization in Ischemic Retinopathy: Recent Advances

Pathological retinal neovascularization (RNV) is a common micro-vascular complication in several retinal diseases including retinopathy of prematurity, diabetic retinopathy, age-related macular degeneration and central vein occlusion. The current therapeutic modalities of RNV are invasive and although they may slow or halt the progression of the disease they are unlikely to restore normal acuity. Therefore, there is an urgent need to develop treatment modalities, which are less invasive and therefore associated with fewer procedural complications and systemic side effects. This review article summarizes our understanding of the pathophysiology and current treatment of RNV in ischemic retinopathies; lists potential therapeutic targets; and provides a framework for the development of future treatment modalities.

Retinopathy of prematurity

The immature retinas of preterm neonates are susceptible to insults that disrupt neurovascular growth, leading to retinopathy of prematurity. Suppression of growth factors due to hyperoxia and loss of the maternal-fetal interaction result in an arrest of retinal vascularisation (phase 1). Subsequently, the increasingly metabolically active, yet poorly vascularised, retina becomes hypoxic, stimulating growth factor-induced vasoproliferation (phase 2), which can cause retinal detachment. In very premature infants, controlled oxygen administration reduces but does not eliminate retinopathy of prematurity. Identification and control of factors that contribute to development of retinopathy of prematurity is essential to prevent progression to severe sight-threatening disease and to limit comorbidities with which the disease shares modifiable risk factors. Strategies to prevent retinopathy of prematurity will depend on optimisation of oxygen saturation, nutrition, and normalisation of concentrations of essential factors such as insulin-like growth factor 1 and ω-3 polyunsaturated fatty acids, as well as curbing of the effects of infection and inflammation to promote normal growth and limit suppression of neurovascular development.

Arginase in retinopathy

Ischemic retinopathies, such as diabetic retinopathy (DR), retinopathy of prematurity and retinal vein occlusion are a major cause of blindness in developed nations worldwide. Each of these conditions is associated with early neurovascular dysfunction. However, conventional therapies target clinically significant macula edema or neovascularization, which occur much later. Intra-ocular injections of anti-VEGF show promise in reducing retinal edema, but the effects are usually transient and the need for repeated injections increases the risk of intraocular infection. Laser photocoagulation can control pathological neovascularization, but may impair vision and in some patients the retinopathy continues to progress. Moreover, neither treatment targets early stage disease or promotes repair. This review examines the potential role of the ureahydrolase enzyme arginase as a therapeutic target for the treatment of ischemic retinopathy. Arginase metabolizes l-arginine to form proline, polyamines and glutamate. Excessive arginase activity reduces the l-arginine supply for nitric oxide synthase (NOS), causing it to become uncoupled and produce superoxide and less NO. Superoxide and NO react and form the toxic oxidant peroxynitrite. The catabolic products of polyamine oxidation and glutamate can induce more oxidative stress and DNA damage, both of which can cause cellular injury. Studies indicate that neurovascular injury during retinopathy is associated with increased arginase expression/activity, decreased NO, polyamine oxidation, formation of superoxide and peroxynitrite and dysfunction and injury of both vascular and neural cells. Furthermore, data indicate that the cytosolic isoform arginase I (AI) is involved in hyperglycemia-induced dysfunction and injury of vascular endothelial cells whereas the mitochondrial isoform arginase II (AII) is involved in neurovascular dysfunction and death following hyperoxia exposure. Thus, we postulate that activation of the arginase pathway causes neurovascular injury by uncoupling NOS and inducing polyamine oxidation and glutamate formation, thereby reducing NO and increasing oxidative stress, all of which contribute to the retinopathic process.

Microvascular complications and diabetic retinopathy: recent advances and future implications

Retinal microvascular alterations have been observed during diabetic retinopathy (DR) due to the retinal susceptibility towards subtle pathological alterations. Therefore, retinal microvascular pathology is essential to understand the nature of retinal degenerations during DR. In this review, the role of retinal microvasculature complications during progression of DR, along with recent efforts to normalize such alterations for better therapeutic outcome, will be underlined. In addition, current therapeutics and future directions for advancement of standard treatment for DR patients will be discussed.