Retinopathy of prematurity: molecular pathology and therapeutic strategies

Tetrahedral framework nucleic acids-based delivery of MicroRNA-22 inhibits pathological neovascularization and vaso-obliteration by regulating the Wnt pathway

The objective of this study was to investigate the effects and molecular mechanisms of tetrahedral framework nucleic acids-microRNA22 (tFNAs-miR22) on inhibiting pathological retinal neovascularization (RNV) and restoring physiological retinal vessels. A novel DNA nanocomplex (tFNAs-miR22) was synthesised by modifying microRNA-22 (miR22) through attachment onto tetrahedral frame nucleic acids (tFNAs), which possess diverse biological functions. Cell proliferation, wound healing, and tube formation were employed for in vitro assays to investigate the angiogenic function of cells. Oxygen-induced retinopathy (OIR) model was utilised to examine the effects of reducing pathological neovascularization (RNV) and inhibiting vascular occlusion in vivo. In vitro, tFNAs-miR22 demonstrated the ability to penetrate endothelial cells and effectively suppress cell proliferation, tube formation, and migration in a hypoxic environment. In vivo, tFNAs-miR22 exhibited promising results in reducing RNV and promoting the restoration of normal retinal blood vessels in OIR model through modulation of the Wnt pathway. This study provided a theoretical basis for the further understanding of RNV, and highlighted the innovative and potential of tFNAs-miR22 as a therapeutic option for ischemic retinal diseases.

Tetrahedral framework nucleic acids inhibit pathological neovascularization and vaso-obliteration in ischaemic retinopathy via PI3K/AKT/mTOR signalling pathway

This study aimed to explore the effect and the molecular mechanism of tetrahedral framework nucleic acids (tFNAs), a novel self-assembled nanomaterial with excellent biocompatibility and superior endocytosis ability, in inhibition of pathological retinal neovascularization (RNV) and more importantly, in amelioration of vaso-obliteration (VO) in ischaemic retinopathy. tFNAs were synthesized from four single-stranded DNAs (ssDNAs). Cell proliferation, wound healing and tube formation assays were performed to explore cellular angiogenic functions in vitro. The effects of tFNAs on reducing angiogenesis and inhibiting VO were explored by oxygen-induced retinopathy (OIR) model in vivo. In vitro, tFNAs were capable to enter endothelial cells (ECs), inhibit cell proliferation, tube formation and migration under hypoxic conditions. In vivo, tFNAs successfully reduce RNV and inhibit VO in OIR model via the PI3K/AKT/mTOR/S6K pathway, while vascular endothelial growth factor fusion protein, Aflibercept, could reduce RNV but not inhibit VO. This study provides a theoretical basis for the further understanding of RNV and suggests that tFNAs might be a novel promising candidate for the treatment of blind-causing RNV.

Growth and neurodevelopmental status in patients with retinopathy of prematurity treated with intravitreal bevacizumab: a case-control study

Background

The current study aimed to evaluate growth and neurodevelopmental status in patients with retinopathy of prematurity (ROP) treated with intravitreal bevacizumab (IVB).

Methods

This historical cohort study was conducted on neonates with ROP who were treated with IVB and age and birth weight-matched controls who did not need IVB. Apgar score less than five, history of blood transfusion and history of infectious diseases were among exclusion criteria. Indirect ophthalmoscopic examinations were performed till complete retinal vascularization. Growth and neurodevelopmental status were evaluated by Age and Stages Questionnaire (ASQ) at the ages of 6, 12, and 18 months. Developmental milestones were assessed in five areas (gross motor, fine motor, personal-social status, problem-solving, and relationship) and overall issues.

Results

A total of 34 cases and 36 controls were included in the present study. Birth weight and corrected gestational age were not statistically different between the groups. In a follow-up period of 18 months, bevacizumab was effective as a primary treatment in the treatment of severe cases of ROP. There was no significant difference between the two groups regarding the five areas and overall issues in follow-up intervals (P > 0.05).

Conclusions

The obtained results did not show any growth and neurodevelopmental differences between treatment-naïve infants and those receiving IVB for the treatment of ROP.

Efficacy of ultra-low-dose (0.1 mg) ranibizumab intravitreal injection for treatment of prethreshold type 1 retinopathy of prematurity: A case series

AIM

To report the results of treatment of type 1 prethreshold retinopathy of prematurity using intravitreal injection of ultra-low dose of ranibizumab (0.1 mg in 0.01 mL).

DESIGN

A retrospective observational case series study.

METHODS

Review of files of eligible infants who received this form of treatment to determine the outcome of treatment and any associated ocular or systemic side effects.

RESULTS

The study included 24 eyes of 12 preterm infants with mean gestational age of 29.75 ± 1.54 weeks and mean birth weight of 1074.58 ± 320.59 g. A total of 22 eyes (91.67%) had zone II disease while 2 eyes of one infant (8.33%) had zone I disease. All cases showed regression of the signs of the active retinopathy of prematurity with complete retinal vascularization. None of the cases required retreatment. Three eyes developed ocular complications. Apart from mild feeding intolerance that lasted for 24 h after injection in one infant, none of the cases developed systemic side effects.

CONCLUSION

Intravitreal injection of ultra-low-dose ranibizumab showed promising efficacy and good ocular safety. However, further large-scale studies are required to give stronger evidence about the efficacy and safety of ultra-low-dose ranibizumab.

Comparison of intravitreal bevacizumab injection and laser photocoagulation for type 1 zone II retinopathy of prematurity

Purpose

To compare the efficacy of intravitreal bevacizumab (IVB) injection with conventional laser photocoagulation in eyes with type 1 zone II retinopathy of prematurity (ROP).

Methods

Preterm infants with type 1 ROP in zone II (stage 2 or 3 ROP with plus disease) were randomly assigned to intravitreal injection of 0.625 mg/0.025 ml bevacizumab (Group 1) or laser photocoagulation (Group 2). Patients were followed weekly for 4 weeks and then biweekly till 90 weeks gestational age. Also, spherical and cylindrical refractive errors were compared at 90 weeks postmenstrual age (PMA).

Results

A total of 116 preterm infants (232 eyes) were treated and completed the follow-up period. IVB injection was done in 154 eyes (77 cases), and laser photocoagulation was done in 78 eyes (39 cases). ROP regressed after single IVB injection in 149 eyes (96.8%) and in 5 eyes (3.2%) after the second injection. Cataract developed in one eye (0.63%) after IVB injection. ROP regressed in 94.7% of treated eyes (76 eyes) in the laser photocoagulation group; however, retinal fold and traction developed in 2 eyes. Spherical and also cylindrical refractive errors had no significant difference.

Conclusions

Both IVB injection and laser photocoagulation are effective methods for the treatment of type 1 zone II ROP. However, re-treatment requirement may be higher in the IVB injection group. IVB re-injection is an effective option for re-treatment in persistent cases.

Chronic Placental Inflammation as a Risk Factor of Severe Retinopathy of Prematurity

Background

Chronic placental inflammation (CPI) has been implicated in the pathogenesis of diseases in premature infants, whereas retinopathy of prematurity (ROP) is a major complication primarily affecting preterm and very low-birth-weight (VLBW) infants. This study aims to investigate the association between CPI and ROP in VLBW infants.

Methods

We performed a retrospective review of clinical records of VLBW infants born between 2013 and 2016. Placental pathology findings including CPI cases were analyzed using logistic regression to study infants’ morbidities and other clinical characteristics.

Results

A total of 402 infants with a mean (standard deviation) gestational age of 28.5 (2.8) weeks and birth weight of 1,027.2 (304.4) g were included. The incidence of ROP was 24.1%. CPI was found in 90 infants (22.4%), among which 28.9% (26 of 90) developed ROP, and 21.1% (19 of 90) underwent laser photocoagulation. Lower gestational age, lower birth weight, longer duration of oxygen supply, and presence of CPI were associated with the development of ROP. After adjustment for gestational age, birth weight, sex, duration of oxygen supply, and other overlapping placental pathology, CPI was associated with the odds for type 1 ROP that required laser photocoagulation (adjusted odds ratio, 2.739; 95% confidence interval, 1.112 to 6.749; p = .029).

Conclusions

CPI was associated with severe ROP requiring treatment with laser photocoagulation in VLBW infants.

Efficacy of Intravitreal Bevacizumab for the Treatment of Zone I Type 1 Retinopathy of Prematurity

Purpose

To describe the efficacy of intravitreal bevacizumab for the treatment of type 1 retinopathy of prematurity (ROP) in zone I.

Methods

Preterm infants with type 1 ROP in zone I (zone I ROP, any stage with plus disease or zone I ROP, stage 3 without plus disease) were enrolled in this prospective study. Intravitreal bevacizumab (0.625 mg/0.025 ml) was injected under topical anesthesia. Patients were followed weekly for 4 weeks and then biweekly till 90 weeks gestational age.

Results

Seventy eyes of 35 patients with type 1 ROP in zone I were enrolled. At a gestational age of 90 weeks, ROP regressed with complete or near-complete peripheral retinal vascularization, in 82.9% of eyes after a single injection and in 92.9% of eyes after up to two injections. In five eyes (7.1%), ROP progressed to stage 4B or 5, so surgical management was required. There were no major complications such as endophthalmitis, cataract, or vitreous hemorrhage after injection.

Conclusion

Intravitreal bevacizumab injection is an effective method for the management of patients with Zone I ROP requiring treatment; however, some cases may progress to more advanced stages and require surgical management. Close monitoring for recurrence or progression is necessary. Eyes with persistent zone I ROP may progress to advanced stages when treated with intravitreal bevacizumab injection and re-treatment may be needed.

Wnt Signaling in Cardiac Disease

Wnt signaling encompasses multiple and complex signaling cascades and is involved in many developmental processes such as tissue patterning, cell fate specification, and control of cell division. Consequently, accurate regulation of signaling activities is essential for proper embryonic development. Wnt signaling is mostly silent in the healthy adult organs but a reactivation of Wnt signaling is generally observed under pathological conditions. This has generated increasing interest in this pathway from a therapeutic point of view. In this review article, the involvement of Wnt signaling in cardiovascular development will be outlined, followed by its implication in myocardial infarct healing, cardiac hypertrophy, heart failure, arrhythmias, and atherosclerosis. The initial experiments not always offer consensus on the effects of activation or inactivation of the pathway, which may be attributed to (i) the type of cardiac disease, (ii) timing of the intervention, and (iii) type of cells that are targeted. Therefore, more research is needed to determine the exact implication of Wnt signaling in the conditions mentioned above to exploit it as a powerful therapeutic target.

The alternative complement pathway aids in vascular regression during the early stages of a murine model of proliferative retinopathy

Proliferative retinopathic diseases often progress in 2 phases: initial regression of retinal vasculature (phase 1) followed by subsequent neovascularization (NV) (phase 2). The immune system has been shown to aid in vascular pruning in such retinopathies; however, little is known about the role of the alternative complement pathway in the initial vascular regression phase. Using a mouse model of oxygen-induced retinopathy (OIR), we observed that alternative complement pathway-deficient mice (Fb(-/-)) exhibited a mild decrease in vascular loss at postnatal day (P)8 compared with age- and strain-matched controls (P = 0.035). Laser capture microdissection was used to isolate the retinal blood vessels. Expression of the complement inhibitors Cd55 and Cd59 was significantly decreased in blood vessels isolated from hyperoxic retinas compared with those from normoxic control mice. Vegf expression was measured at P8 and found to be significantly lower in OIR mice than in normoxic control mice (P = 0.0048). Further examination of specific Vegf isoform expression revealed a significant decrease in Vegf120 (P = 0.00032) and Vegf188 (P = 0.0092). In conjunction with the major modulating effects of Vegf during early retinal vascular development, our data suggest a modest involvement of the alternative complement pathway in targeting vessels for regression in the initial vaso-obliteration stage of OIR.

A new role for cofilin in retinal neovascularization

Pak1 plays an important role in several cellular processes, including cell migration, but its role in pathological angiogenesis is not known. Here, we have determined its role in pathological retinal angiogenesis using an oxygen-induced retinopathy (OIR) model. VEGFA induced phosphorylation of Pak1 and its effector cofilin in a manner that was dependent on time as well as p38MAPKβ (also known as MAPK11) in human retinal microvascular endothelial cells (HRMVECs). Depletion of the levels of any of these molecules inhibited VEGFA-induced HRMVEC F-actin stress fiber formation, migration, proliferation, sprouting and tube formation. In accordance with these observations, hypoxia induced Pak1 and cofilin phosphorylation with p38MAPKβ being downstream to Pak1 and upstream to cofilin in mouse retina. Furthermore, Pak1 deficiency abolished hypoxia-induced p38MAPKβ and cofilin phosphorylation and abrogated retinal endothelial cell proliferation, tip cell formation and neovascularization. In addition, small interfering RNA (siRNA)-mediated downregulation of p38MAPKβ or cofilin levels in the wild-type mouse retina also diminished endothelial cell proliferation, tip cell formation and neovascularization. Taken together, these observations suggest that, although the p38MAPKβ-Pak1-cofilin axis is required for HRMVEC migration, proliferation, sprouting and tubulogenesis, Pak1-p38MAPKβ-cofilin signaling is also essential for hypoxia-induced mouse retinal endothelial cell proliferation, tip cell formation and neovascularization.

Seeing through VEGF: innate and adaptive immunity in pathological angiogenesis in the eye

The central role of vascular endothelial growth factor (VEGF) signaling in regulating normal vascular development and pathological angiogenesis has been documented in multiple studies. Ocular anti-VEGF therapy is highly effective for treating a subset of patients with blinding eye disorders such as diabetic retinopathy and neovascular age-related macular degeneration (AMD). However, chronic VEGF suppression can lead to adverse effects associated with poor visual outcomes due to the loss of prosurvival and neurotrophic capacities of VEGF. In this review, we discuss emerging evidence for immune-related mechanisms that regulate ocular angiogenesis in a VEGF-independent manner. These novel molecular and cellular pathways may provide potential therapeutic avenues for a multitarget strategy, preserving the neuroprotective functions of VEGF in those patients whose disease is unresponsive to VEGF neutralization.

The alternative complement pathway regulates pathological angiogenesis in the retina

A defining feature in proliferative retinopathies is the formation of pathological neovessels. In these diseases, the balance between neovessel formation and regression determines blindness, making the modulation of neovessel growth highly desirable. The role of the immune system in these retinopathies is of increasing interest, but it is not completely understood. We investigated the role of the alternative complement pathway during the formation and resolution of aberrant neovascularization. We used alternative complement pathway-deficient (Fb(-/-)) mice and age- and strain-matched control mice to assess neovessel development and regression in an oxygen-induced retinopathy (OIR) mouse model. In the control mice, we found increased transcription of Fb after OIR treatment. In the Fb(-/-) mice, we prepared retinal flatmounts and identified an increased number of neovessels, peaking at postnatal day 17 (P17; P=0.001). Subjecting human umbilical vein endothelial cells (HUVECs) to low oxygen, mimicking a characteristic of neovessels, decreased the expression of the complement inhibitor Cd55. Finally, using laser capture microdissection (LCM) to isolate the neovessels after OIR, we found decreased expression of Cd55 (P=0.005). Together, our data implicate the alternative complement pathway in facilitating neovessel clearance by down-regulating the complement inhibitor Cd55 specifically on neovessels, allowing for their targeted removal while leaving the established vasculature intact.-Sweigard, J. H., Yanai, R., Gaissert, P., Saint-Geniez, M., Kataoka, K., Thanos, A., Stahl, G. L., Lambris, J. D., Connor, K. M. The alternative complement pathway regulates pathological angiogenesis in the retina.

Roles of EphA2 in Development and Disease

The Eph family of receptor tyrosine kinases (RTKs) has been implicated in the regulation of many aspects of mammalian development. Recent analyses have revealed that the EphA2 receptor is a key modulator for a wide variety of cellular functions. This review focuses on the roles of EphA2 in both development and disease.

Associations of VEGF/VEGF-receptor and HGF/c-Met promoter polymorphisms with progression/regression of retinopathy of prematurity

PURPOSE

To determine the effect(s) of vascular endothelial growth factor (VEGF), VEGF receptor-2 (VEGFR-2), hepatocyte growth factor (HGF), and HGF receptor (c-Met) polymorphisms on progression/regression of retinopathy of prematurity (ROP) in premature infants.

MATERIALS AND METHODS

This study comprised both a prospective analysis and a clinically relevant laboratory investigation. Enrolled were 123 Turkish preterm infants--gestational age (GA), ≤34 weeks; birth weight (BW), ≤1500 g--from a single tertiary care center. Infants were grouped as those who had undergone laser therapy (Group 1, n = 42), those with spontaneously regressed ROP (Group 2, n = 50), and those with no ROP (controls) (Group 3, n = 31). VEGF (-634) C and VEGF (-460) C polymorphisms were analyzed using the PCR-restriction fragment length polymorphism (RFLP) (PCR-RFLP) technique. VEGFR-2, HGF, and c-Met gene promoter polymorphisms were determined by direct sequencing.

RESULTS

Mean GAs and BWs of infants in Groups 1 and 2 were statistically significantly lower than those of Group 3 (p = 0.001). Frequencies of VEGF (-634) C and VEGF (-460) C polymorphisms were similar for all groups. We found a +32G→A single-nucleotide polymorphism (SNP) in the promoter region of the VEGFR-2 gene. HGF and c-Met gene promoter polymorphisms were not found in any group.

CONCLUSIONS

Our results indicate that there is no association between the carrier states of gene promoter polymorphisms VEGF (-634) C, VEGF (-460) C, and VEGFR-2, and progression or spontaneous regression of ROP in preterm infants. The absence of HGF and c-Met polymorphisms in our study groups suggests that polymorphisms in the minimal promoters of these genes are not involved in the pathogenesis of ROP.

Incidence of retinopathy of prematurity and risk factors in the South-Western region of iran

AIMS

The aim of this study was to report the incidence of retinopathy of prematurity (ROP) and the contribution of various risk factors to ROP in the south-western region of Iran.

MATERIAL AND METHODS

This cross-sectional case-control series reviewed all low birth weight (LBW, ≤2000 g) neonates and/or neonates less than 32 weeks gestational age who had been hospitalized in the Neonatal Intensive Care Unit from 2006 to 2010. The cohort was divided into infants without ROP (nonROP group) and infants with ROP (ROP group). Infants were first examined by a group of pediatric ophthalmologists 6 weeks after delivery, and then were followed every 1-2 weeks until death, discharge or complete retinal avascularization. If an infant developed ROP, further examinations were performed based on the Early Treatment for Retinopathy of Prematurity Study protocol. Demographic data, medical treatment, and ophthalmic disorders were all statistically analyzed.

RESULTS

A total of 576 infants met the criteria for evaluation. Of 576 total patients, 183 infants (32%) (88 males, 95 females) had ROP. There were significant differences between groups in gestational age, body weight, and duration of oxygen administration, and sepsis (P<0.05). Male/female ratio, single and multiple births, and jaundice, phototherapy, and blood transfusion were not significant. The majority of ROP was stage I or II (137, 74.8%). Stage III or greater developed in 46 infants (25.1%) [Note: The ocular history and ocular outcomes are not risk factors.]

CONCLUSIONS

The incidence of ROP in this study is higher than that in other parts of the world. Awareness and knowledge of ROP and its relative risks need to be reinforced in ophthalmologists and other health practitioners.

Impacts of hypoxia-inducible factor-1 knockout in the retinal pigment epithelium on choroidal neovascularization

PURPOSE

Hypoxia-inducible factor (HIF)-1 is a key oxygen sensor and is believed to play an important role in neovascularization (NV). The purpose of this study is to determine the role of retinal pigment epithelium (RPE)-derived HIF-1α on ocular NV.

METHODS

Conditional HIF-1α knockout (KO) mice were generated by crossing transgenic mice expressing Cre in the RPE with HIF-1α floxed mice, confirmed by immunohistochemistry, Western blot analysis, and fundus fluorescein angiography. The mice were used for the oxygen-induced retinopathy (OIR) and laser-induced choroidal neovascularization (CNV) models.

RESULTS

HIF-1α levels were significantly decreased in the RPE layer of ocular sections and in primary RPE cells from the HIF-1α KO mice. Under normal conditions, the HIF-1α KO mice exhibited no apparent abnormalities in retinal histology or visual function as shown by light microscopy and electroretinogram recording, respectively. The HIF-1α KO mice with OIR showed no significant difference from the wild-type (WT) mice in retinal levels of HIF-1α and VEGF as well as in the number of preretinal neovascular cells. In the laser-induced CNV model, however, the disruption of HIF-1α in the RPE attenuated the over expression of VEGF and the intercellular adhesion molecule 1 (ICAM-1), and reduced vascular leakage and CNV area.

CONCLUSIONS

RPE-derived HIF-1α plays a key role in CNV, but not in ischemia-induced retinal NV.

The association between respiratory tract Ureaplasma urealyticum colonization and severe retinopathy of prematurity in preterm infants ≤1250 g

AIM

To evaluate the association between respiratory tract Ureaplasma urealyticum (Uu) colonization and development of retinopathy of prematurity (ROP) requiring treatment.

METHODS

The infants with birthweight (BW) ≤1250 g born in a third-level neonatal intensive care unit between March 2009 and May 2010 were prospectively identified. Nasopharyngeal swabs for Uu colonization were taken in postnatal first 3 days. Culture-positive patients were reevaluated on the twelfth day by nasopharyngeal swabs for Uu. The primary outcome was to define whether there was an association between respiratory tract Uu colonization and severe ROP requiring treatment. Independent sample's t-test or Mann-Whitney U-test was used to compare continuous variables and Chi-square test or Fisher's exact test for categorical variables. Multivariate (backward) logistic regression analysis was performed to simultaneously measure the influence of the independent variables with ROP as the dependent variable.

RESULTS

A total of 25 (12.1%) infants developed severe ROP requiring treatment among 206 infants who underwent ROP screening. Mean BW and gestational age of total cohort were 1013±159 g and 27.9±1.6 weeks, respectively. Multivariate analysis demonstrated that BW (OR: 0.64 (95% Cl 0.47-0.88); P=0.006), duration of mechanical ventilation (OR: 1.17 (95% Cl 1.06-1.28); P=0.001), premature rupture of membrane >18 h (OR: 3.83 (95% Cl 1.2-12.2); P=0.02), and Uu positivity in both cultures (OR: 5.02 (95% Cl 1.8-13.9); P=0.002) were independent risk factors for the development of severe ROP requiring treatment.

CONCLUSIONS

Respiratory tract colonization with Uu was independently associated with severe ROP requiring treatment.

Angiogenesis: possible analogies between the eye and the inner ear

Angiogenesis is a phenomenon concerning both physiological conditions linked to development and pathological conditions; in the latter it is aimed at providing an enhancement in blood supply to tumours, on one hand, and to restore the circulation in peripheral arterial and ischemic diseases, on the other hand, thus resulting in a controversial effect depending on the circumstances. When occurring in the eye, angiogenesis clearly proved to represent a threaten, whereas an univocal interpretation of the action of angiogenesis on the inner ear homeostasis is still lacking despite the morphologic and functional analogies between eye and labyrinth. These analogies can raise same doubt on the supposed role of angiogenesis in terms of preserving the function of a threatened inner ear: even this organ could be further damaged by microvascular disorders and/or mechanical changes able to jeopardize its architecture and consequently its function. If a parallelism between ear and eye is extendable to this aspect, this could open new perspectives in the treatment of certain affections of the inner ear by borrowing therapeutic strategies that have given appreciable and consolidate responses in the treatment of degenerative retinopathy.

Serum concentrations of bevacizumab (avastin) and vascular endothelial growth factor in infants with retinopathy of prematurity

PURPOSE

To determine the serum concentrations of bevacizumab and vascular endothelial growth factor (VEGF) in infants with retinopathy of prematurity (ROP) who received intravitreal bevacizumab; and to determine whether the changes in the serum concentration of bevacizumab were significantly correlated with the serum concentration of VEGF after intravitreal bevacizumab.

DESIGN

Case series.

METHODS

Eleven infants (4 girls and 7 boys) with ROP were studied. They received 0.25 mg or 0.5 mg of intravitreal bevacizumab to either 1 eye (unilateral cases) or both eyes (bilateral cases) with vascularly active ROP. Serum samples were collected before and 1 day, 1 week, and 2 weeks after the intravitreal bevacizumab. The serum concentrations of bevacizumab and VEGF were measured by enzyme-linked immunosorbent assay, and the correlation in the serum levels between the 2 was determined.

RESULTS

The serum concentration of bevacizumab before and 1 day, 1week, and 2 weeks after a total of 0.5 mg of intravitreal bevacizumab was 0 ng/mL, 195 ± 324 ng/mL, 946 ± 680 ng/mL, and 1214 ± 351 ng/mL, respectively. The serum bevacizumab level before and 1 day and 1 week after a total 1.0 mg of intravitreal bevacizumab was 0 ng/mL, 248 ± 174 ng/mL, and 548 ± 89 ng/mL, respectively. The serum concentration of VEGF before and 1 day, 1 week, and 2 weeks after a total of 0.5 mg intravitreal bevacizumab was 1628 ± 929 pg/mL, 427 ± 140 pg/mL, 246 ± 110 pg/mL, and 269 ± 157 pg/mL, respectively. There was a significant negative correlation (r = -0.575, P = .0125) between the serum concentration of bevacizumab and VEGF when a total of 0.25 mg or 0.5 mg of bevacizumab was injected.

CONCLUSIONS

These results indicate that bevacizumab can escape from the eye into the systemic circulation and reduce the serum level of VEGF in infants with ROP. Continued extensive evaluations of infants are warranted for possible effects after intravitreal bevacizumab in ROP patients.

Complement involvement in neovascular ocular diseases

Pathological neovascularization (NV) is a hallmark of late stage neovascular age-related macular degeneration (AMD), diabetic retinopathy (DR), and retinopathy of prematurity (ROP). There is accumulating evidence that alterations in inflammatory and immune system pathways that arise from genetic differences, injury, and disease can predispose individuals to retinal neovascular eye diseases. Yet the mechanism of disease progression with respect to the complement system in these maladies is not fully understood. Recent studies have implicated the complement system as an emerging player in the etiology of several retinal diseases. We will summarize herein several of the complement system pathways known to be involved in ocular neovascular pathologies. Current treatment for many neovascular eye diseases focuses on suppression of NV with laser ablation, photodynamic therapy, or anti-VEGF angiogenic inhibitors. However, these treatments do not address the underlying cause of many of these diseases. A clear understanding of the cellular and molecular mechanisms could bring a major shift in our approach to disease treatment and prevention.

Early experience with intravitreal bevacizumab combined with laser treatment for retinopathy of prematurity

OBJECTIVE

This study was designed to present our early experience with intravitreal bevacizumab combined with laser treatment for retinopathy of prematurity (ROP) at a single institution over a 13-month-period.

METHODS

A retrospective case series of eight children with ROP who received intravitreal bevacizumab combined with laser treatment between June 2007 and July 2008 were reported. A chart review was conducted to evaluate if stability of the ROP lesion had been achieved. Main information collected included data on demographics, gestational age, birth weight, length of stay in neonatal intensive care unit, and stage of ROP.

RESULTS

Fifteen eyes of eight subjects were treated. One eye did not receive any treatment due to complete retinal detachment. The median age at treatment was 8 weeks (range, 6 weeks to 1 year). The most common stage of ROP was 3+. All eyes remained stable at 1 year or later after treatment.

CONCLUSION

Intravitreal bevacizumab in conjunction with laser treatment had promising results at our institution. We recommend prospective, randomized, controlled clinical trials to compare the effect of laser treatment alone, of bevacizumab treatment alone (at different doses), and of combined bevacizumab and laser treatment.

Vitreous levels of angiopoietin-1 and angiopoietin-2 in eyes with retinopathy of prematurity

PURPOSE

To determine the vitreous levels of angiopoietin (Ang)-1 and Ang-2 in eyes with retinopathy of prematurity (ROP), and to determine the correlation between the 2 levels.

DESIGN

Retrospective case-control study.

METHODS

Forty-eight eyes with stage 4 ROP were studied. Six eyes with congenital cataract were used as controls. The ROP eyes were classified by the vascular activity into highly (n = 22), moderately (n = 15), and mildly (n = 11) vascular-active ROP. Eyes with highly vascular-active ROP initially received 0.5 mg of intravitreal bevacizumab (IVB) and underwent vitrectomy within 1 week. The others underwent vitrectomy without IVB. Vitreous samples were collected at the beginning of vitrectomy, and the vitreous levels of Angs were measured by enzyme-linked immunosorbent assay.

RESULTS

The mean concentrations of Ang-1 and Ang-2 were 201.9 and 7832.1 pg/mL in highly vascular-active ROP eyes, 216.1 and 7731.2 pg/mL in moderately vascular-active ROP eyes, 533.8 and 1685.9 pg/mL in mildly vascular-active ROP eyes, and 0 and 41.5 pg/mL in control eyes. The vitreous Ang-1 level was significantly higher (P < .05) in highly, moderately, and mildly vascular-active ROP eyes than in control eyes. The vitreous Ang-2 level was significantly higher (P < .05) in highly and moderately vascular-active ROP eyes than in control eyes. There was a significant negative correlation (r = -0.406; P = .040) between the Ang-1 and Ang-2 levels in moderately and mildly vascular-active ROP eyes.

CONCLUSIONS

The balance of Ang-1 and Ang-2 in the vitreous may be important in the pathogenesis of ROP.

Preterm birth and neurodevelopmental outcome: a review

BACKGROUND

The incidence of preterm delivery and the survival rate of preterm newborns are rising, due to the increased use of assisted reproductive technology associated with multiple gestations and improved technology in obstetrics and neonatology, which allow saving preterm infants at earlier gestational ages. As a consequence, the risk of developmental disabilities in preterm children is high, and clinical pictures need to be fully defined.

METHODS

Narrative review including articles regarding neurodevelopmental disorders published in the international medical literature and reported in PubMed between the years 2000 and January 2010.

RESULTS

Although survival rates of extremely low birth weight infants (ELBW) significantly increased during the last decade, the substantial stability of disability trends in this population was disappointing. Late-preterm infants, who account for about 75% of all preterm births and had not been considered at risk for adverse long-term neurodevelopmental outcomes in the past, are now reconsidered as more likely to develop such events, though their risk remains lower than in ELBW.

CONCLUSIONS

The findings of the studies discussed in our article support the importance of early diagnosis in order to make decision about appropriate treatment of preterm infants.

Genetic susceptibility to advanced retinopathy of prematurity (ROP)

Retinopathy of prematurity (ROP) is a vascular vitreoretinopathy that affects infants with short gestational age and low birth-weight. The condition is a multifactorial disease and is clinically similar to familial exudative vitreoretinopathy (FEVR), which is a bilateral hereditary eye disorder affecting full-term infants. Both of them are characterized by the abnormal vessel growth in the vitreous that can lead to vitreoretinal traction, retinal detachment and other complications resulting in blindness. Despite the recent advances in diagnosis and treatment, ROP remains a major cause of childhood blindness in developed countries. The etiology of pathogenesis of advanced ROP is currently unknown. In the past, many causative factors such as length of time exposed to supplemental oxygen, excessive ambient light exposure and hypoxia have been suggested but evidence for these as independent risk factors in recent years is not compelling. It is not clear why ROP in a subset of infants with low birth-weight progresses to a severe stage (retinal detachment) despite timely intervention whereas in other infants with similar clinical characteristics ROP regresses spontaneously. Recent research with candidate gene approach, higher concordance rate in monozygotic twins and other clinical and experimental animal studies, suggest a strong genetic predisposition to ROP besides environmental factors such as prematurity. Three genes, which are involved in the Wnt signaling pathway, are mutated in both FEVR and in a small percentage of ROP disorder. However, none of the genetic factors identified thus far in ROP, account for a substantial number of patient population. Future studies involving genomics, bioinformatics and proteomics may provide a better understanding of the pathophysiology and management of ROP.

The mouse retina as an angiogenesis model

The mouse retina has been used extensively over the past decades to study both physiologic and pathologic angiogenesis. Over time, various mouse retina models have evolved into well-characterized and robust tools for in vivo angiogenesis research. This article is a review of the angiogenic development of the mouse retina and a discussion of some of the most widely used vascular disease models. From the multitude of studies performed in the mouse retina, a selection of representative works is discussed in more detail regarding their role in advancing the understanding of both the ocular and general mechanisms of angiogenesis.

Atrial natriuretic peptide reduces vascular leakage and choroidal neovascularization

Atrial natriuretic peptide (ANP) is a hormone with diuretic, natriuretic, and vasodilatory properties. ANP blocks vascular endothelial growth factor (VEGF) production and signaling in vitro; however, its role in vascular leakage and angiogenesis is unknown. In vitro, retinal barrier permeability (transepithelial electrical resistance (TEER)) was measured in cultured retinal endothelial (HuREC) and retinal epithelial (ARPE-19) cells with VEGF (10 ng/ml), ANP (1 pM to 1 micromol/L), and/or isatin, an ANP receptor antagonist. In vivo, blood-retinal barrier (BRB) leakage was studied using the Evans Blue dye technique in rats treated with intravitreal injections of ANP, VEGF, or vehicle. Choroidal neovascularization was generated by laser injury, and 7 days later, lesion size and leakage was quantitated. ANP significantly reversed VEGF-induced BRB TEER reduction in both HuREC and ARPE-19 cells, modeling the inner and the outer BRB, respectively. Isatin, a specific ANP receptor antagonist, reversed ANP's effect. ANP reduced the response of ARPE-19 cells to VEGF apically but not basolaterally, suggesting polarized expression of the ANP receptors in these cells. ANP's TEER response was concentration but not time dependent. In vivo, ANP significantly reduced VEGF-induced BRB leakage and the size of laser-induced choroidal neovascularization lesions. In sum, ANP is an effective inhibitor of VEGF-induced vascular leakage and angiogenesis in vivo. These results may lead to new treatments for ocular diseases where VEGF plays a central role, such as age-related macular degeneration or diabetic retinopathy.

Modulation of Hypoxia-Induced Neovascularization by JSM6427, an Integrin α5β 1 Inhibiting Molecule

PURPOSE

Integrin alpha5beta1, a fibronectin receptor, is involved in endothelial cell migration and proliferation. Here we investigate the effect of JSM6427, an integrin alpha5beta1 inhibiting molecule, on the development of retinal vascular system using the mouse model of oxygen-induced retinopathy (OIR).

METHODS

Endothelial cell migration and sprouting was analyzed in vitro using a 2D migration assay and a 3D sprouting/angiogenesis assay in fibrin gel. C57BL/C6 mice were exposed to 75% oxygen from postnatal day 7 (P7) to P12 and returned to room air thereafter. Intravitreal injection of 40 microg JSM6427 was performed in each one eye on P14. On P17, vascular area, avascularized area, and neovascular blood vessel tufts were quantified after perfusion with fluorescein-coupled concanavalin A. The number of retinal neovascular cell nuclei was determined in hematoxylin-stained cross sections of the eyes. Integrin alpha 5 expression was determined by immunohistochemistry.

RESULTS

In vitro, JSM6427 inhibits the migration of HUVEC and the tube formation induced by both bFGF and VEGF. In vivo, integrin alpha 5 expression was detectable in neovascular retinal blood vessels. Oxygen treatment (positive control) in comparison with no oxygen treatment (negative control) reduced significantly the vascularized area and increased the avascularized area. A single intravitreal injection of 40 microg JSM6427 resulted in a significant reduction of the vascularized area and the number of preretinal nuclei in comparison with the intravitreal injection of the vehicle while the avascularized area increased significantly.

CONCLUSIONS

These results imply an essential role of integrin alpha5beta1 in the refining of the retinal vasculature in OIR and suggest JSM6427 may have a possible therapeutic function for neovascular disease.

Immaturity, perinatal inflammation, and retinopathy of prematurity: a multi-hit hypothesis

OBJECTIVE

To explore the relationship among markers of infection/inflammation in their association with retinopathy of prematurity (ROP).

METHODS

We studied clinical characteristics and 4 single nucleotide polymorphisms in infection/inflammation-associated genes in a group of 73 children with a gestational age<32 weeks. Forty-four children (60%) had ROP, of whom 13 (30% of those with ROP) progressed to stage 3 ROP. No child had grade 4 or 5 ROP. We employed both descriptive and analytic statistical methods.

RESULTS

Clinical variables of infection/inflammation were consistently associated with an increased risk of ROP. Among infants with ROP, they were also associated with progression to ROP grade 3. Genetic markers were not associated with ROP occurrence, but with progression to high grade disease. In tri-variable analyses exploring the effects of gestational age <29 weeks, clinical chorioamnionitis (CAM) and neonatal systemic inflammatory response syndrome (SIRS) on ROP occurrence, low gestational age was the most important antecedent, while additional individual or joint exposure to SIRS and CAM add appreciably to this risk of progression to high grade disease.

CONCLUSION

Both antenatal and neonatal exposure to inflammation appear to contribute to the increased ROP risk in preterm infants.

Wnt/Frizzled signaling in angiogenesis

The roles of growth factors such as angiopoietin (Ang) and vascular endothelial growth factor (VEGF) in angiogenesis have been known for some time, yet we have just an incipient appreciation for the contribution of Wnts to this process. Cellular proliferation and polarity, apoptosis, branching morphogenesis, inductive processes, and the maintenance of stem cells in an undifferentiated, proliferative state are all regulated by Wnt signaling. The development and maintenance of vascular structures are dependent on all these processes, and their orchestration has, to some extent, been revealed in studies of VEGF and Ang receptors. Recent evidence links the Wnt/Frizzled signaling pathway to proper vascular growth in mammals but our knowledge of Wnt function in the vasculature is rudimentary. Further insight into vascular development and the process of angiogenesis depends on evaluating the function of novel endothelial regulatory pathways such as Wnt/Frizzled signaling.

Lack of association of the VEGF gene promoter (-634 G-->C and -460 C-->T) polymorphism and the risk of advanced retinopathy of prematurity

BACKGROUND

Recently, it has been reported that genetic polymorphism (-634 G-->C and -460 C-->T) in the promoter region of the vascular endothelial growth factor (VEGF) gene can influence the progression of retinopathy of prematurity (ROP). In order to evaluate its general applicability as a screening procedure in clinics and to replicate the above result, we have undertaken the following study.

METHODS

We have analyzed a cohort of 61 patients with advanced ROP (stage 4 and 5) along with 61 normal controls for the VEGF gene promoter polymorphism. For this purpose, blood samples were collected from each patient and leukocyte DNA was isolated. Genomic DNA was amplified by the polymerase chain reaction (PCR) method with two pairs of primers designed to amplify separately the promoter region (containing -634 G-->C and -460 C-->T polymorphism) of the VEGF gene. The amplified product was subjected to restriction enzyme digestion. The base change in the restriction site was further confirmed by a BigDye terminator cycle sequencing of the amplified product.

RESULTS

Our analysis suggests that there is no significant difference in allelic frequency of the VEGF gene between normal subjects and patients with advanced ROP in our cohort.

CONCLUSION

Our results do not support the association of the VEGF gene promoter polymorphism and the risk of advanced ROP. In order to adapt this method for the identification of high-risk infants in clinics in the future, a large-scale study involving a mixed ethnically diverse population is much needed.

Inflammation, brain damage and visual dysfunction in preterm infants

Antenatal intrauterine infection and the fetal inflammatory response appear to be important pathogenetic factors in preterm birth and subsequent neonatal disorders of the lung and brain. In this paper, we expand this concept to include visual dysfunction. Although present data tend to support our notion, we suggest that more experimental and epidemiological research is needed to elucidate mechanisms of infection/inflammation-induced damage to the eye and visual brain pathways of preterm infants.

Wnt/beta-catenin signaling induces proliferation, survival and interleukin-8 in human endothelial cells

Wnts are secreted signaling proteins able to control diverse biological processes such as cell differentiation and proliferation. Many Wnts act through a canonical, beta-catenin signaling pathway. Here, we report that Wnt receptors and transcriptional effectors are expressed in primary human endothelial cells and that Wnt/beta-catenin signaling promotes angiogenesis. Human umbilical vein and microvascular endothelial cells express Wnt receptors, Frizzled-4, -5, -6, and beta-catenin-associated transcription factors, Tcf-1, -3, -4 and Lef-1. In endothelial cells, ectopic expression of Wnt-1 stabilized cytosolic beta-catenin, demonstrating activation of the Wnt/beta-catenin canonical signaling pathway. Expression of Wnt-1 or a stabilized and active form of beta-catenin, beta-cateninS37A, promoted endothelial cell proliferation. Proliferation induced by Wnt/beta-catenin signaling was optimal in the presence of bFGF. beta-cateninS37A expression in endothelial cells promoted survival after growth factor deprivation. Using matrigel assays, Wnt-1 or beta-cateninS37A expression promoted the formation of capillary-like networks. To help define the effectors of Wnt angiogenic function, microarray analysis was used to compare endothelial cells expressing Wnt-1 to control cells. Interleukin-8, a known angiogenic factor, was identified as a transcriptional target of Wnt/beta-catenin signaling in endothelial cells. Expression of either Wnt-1 or beta-cateninS37A induced Interleukin-8 transcripts and secreted protein. We thus conclude that Wnt/beta-catenin signaling promotes angiogenesis possibly via the induction of known angiogenic regulators such as Interleukin-8.

MMP-1 activation by serine proteases and MMP-10 induces human capillary tubular network collapse and regression in 3D collagen matrices

Previous work has shown that endothelial cell (EC)-derived matrix metalloproteinases (MMPs) regulate regression of capillary tubes in vitro in a plasmin- and MMP-1 dependent manner. Here we report that a number of serine proteases can activate MMP-1 and cause capillary tube regression; namely plasma kallikrein, trypsin, neutrophil elastase, cathepsin G, tryptase and chymase. Plasma prekallikrein failed to induce regression without coactivators such as high molecular weight kininogen (HMWK) or coagulation Factor XII. The addition of trypsin, the neutrophil serine proteases (neutrophil elastase and cathepsin G) and the mast cell serine proteases (tryptase and chymase) each caused MMP-1 activation and collagen type I proteolysis, capillary tubular network collapse, regression and EC apoptosis. Capillary tube collapse is accompanied by collagen gel contraction, which is strongly related to the wound contraction that occurs during regression of granulation tissue in vivo. We also report that proMMP-10 protein expression is markedly induced in ECs undergoing capillary tube morphogenesis. Addition of each of the serine proteases described above led to activation of proMMP-10, which also correlated with MMP-1 activation and capillary tube regression. Treatment of ECs with MMP-1 or MMP-10 siRNA markedly delayed capillary tube regression, whereas gelatinase A (MMP-2), gelatinase B (MMP-9) and stromelysin-1 (MMP-3) siRNA-treated cells behaved in a similar manner to controls and regressed normally. Increased expression of MMP-1 or MMP-10 in ECs using recombinant adenoviral delivery markedly accelerated serine protease-induced capillary tube regression. ECs expressing increased levels of MMP-10 activated MMP-1 to a greater degree than control ECs. Thus, MMP-10-induced activation of MMP-1 correlated with tube regression and gel contraction. In summary, our work demonstrates that MMP-1 zymogen activation is mediated by multiple serine proteases and MMP-10, and that these events are central to EC-mediated collagen degradation and capillary tube regression in 3D collagen matrices.

Expression of angiogenesis factors in human umbilical vein endothelial cells and their regulation by PEDF

The VEGFs and FGF-2 stimulate angiogenesis. Pigment epithelium-derived factor (PEDF) and thrombospondin-1 (TSP-1) strongly inhibit angiogenesis. Human umbilical vein endothelial cells (HUVECs) expressed VEGF-A, -B, -C, the VEGF receptors R1, R2, and R3, PEDF, FGF-2, and TSP-1, but VEGF-D transcripts were barely detectable. Hypoxia reduced the transcript levels of VEGF-C and its cognate receptor, VEGF-R3. PEDF blocked the effect of CoCl(2) on these two factors. The expression of VEGF-A and -B as well as VEGF-R1 and VEGF-R2 remained unchanged after exposure to hypoxia, PEDF, or both. There was a marked reduction in TSP-1 transcripts in CoCl(2) treated cultures and PEDF blocked this reduction. PEDF induced a small increase in FGF-2 transcripts in HUVECs, but there was no change in FGF-2 expression in HUVECs exposed to hypoxia or hypoxia plus PEDF. PEDF may control neovascularization, in part, by restoring the negative effects of hypoxia on the expression of a potent angiogenesis inhibitor, TSP-1. PEDF may also modulate vascular leakage by maintaining the transcriptional levels of the vascular homeostasis factors, VEGF-C and VEGF-R3 in hypoxic conditions.

Transient exposure of rat pups to hyperoxia at normobaric and hyperbaric pressures does not cause retinopathy of prematurity

We have shown that hyperoxia reduces brain damage in a rat model of hypoxia-ischemia. The purpose of this study was to examine the possibility of hyperoxia in inducing vision-threatening retinopathy. Two different experiments were conducted in this study. PART 1: seven-day-old rat pups were subjected to unilateral carotid artery ligation followed by 2 h of hypoxia (8% O2 at 37 degrees C). Pups were treated with 100% oxygen at 1 ATA, 1.5 ATA, and 3.0 ATA for a duration of 1 h. PART 2: Newborn rat pups were exposed to 100% oxygen at 1, 1.5, or 3.0 ATA for 1 h, the same treatment protocol used for brain protection after hypoxia-ischemia. Retinopathy was evaluated by the degree of neovascularization (measuring retinal vascular density), by the structural abnormalities (histology) in the retina, and by the expression of hypoxia-hyperoxia sensitive proteins including hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) at 24 h, 1, 2, and 10 weeks after hyperoxia exposure. Hyperoxic treatment at all pressures administered significantly reduced the hypoxia-ischemic-induced reduction in brain weight. Retinal vascular density measurements revealed no signs of neovascularization after hyperoxia exposure. There were also no abnormalities in the structure of the retina and no changes in the protein expression of HIF-1alpha and VEGF following hyperoxia exposure. Exposure to hyperoxia for 1 h at normobaric or hyperbaric pressures did not result in the structural changes or abnormal vascularization that is associated with retinopathy of prematurity, suggesting that hyperoxia is a safe treatment for hypoxic newborn infants.