Expression of Total Vascular Endothelial Growth Factor and the Anti-angiogenic VEGF 165 b Isoform in the Vitreous of Patients with Retinopathy of Prematurity

Differences in activation of intracellular signaling in primary human retinal endothelial cells between isoforms of VEGFA 165

Purpose

There are reports that a b-isoform of vascular endothelial growth factor-A 165 (VEGFA₁₆₅b) is predominant in normal human vitreous, switching to the a-isoform (VEGFA₁₆₅a) in the vitreous of some diseased eyes. Although these isoforms appear to have a different ability to activate the VEGF receptor 2 (VEGFR2) in various endothelial cells, the nature of their ability to activate intracellular signaling pathways is not fully characterized, especially in retinal endothelial cells. We determined their activation potential for two key intracellular signaling pathways (MAPK, AKT) over complete dose-response curves and compared potential effects on the expression of several VEGFA₁₆₅ target genes in primary human retinal microvascular endothelial cells (HRMECs).

Methods

To determine full dose-response curves for the activation of MAPK (ERK1/2), AKT, and VEGFR2, direct in-cell western assays were developed using primary HRMECs. Potential differences in dose-response effects on gene expression markers related to endothelial cell and leukocyte adhesion (ICAM1, VCAM1, and SELE) and tight junctions (CLDN5 and OCLN) were tested with quantitative PCR.

Results

Activation dose-response analysis revealed much stronger activation of MAPK, AKT, and VEGFR2 by the a-isoform at lower doses. MAPK activation in primary HRMECs displayed a sigmoidal dose-response to a range of VEGFA ₁₆₅ a concentrations spanning 10-250 pM, which shifted higher into the 100-5,000 pM range with VEGFA ₁₆₅ b. Similar maximum activation of MAPK was achieved by both isoforms at high concentrations. Maximum activation of AKT by VEGFA ₁₆₅ b was only half of the maximum activation from VEGFA ₁₆₅ a. At a lower intermediate dose, where VEGFA ₁₆₅ a activated intracellular signaling stronger than VEGFA ₁₆₅ b, the changes in VEGFA target gene expression were generally greater with VEGFA ₁₆₅ a.

Conclusions

In primary HRMECs, VEGFA ₁₆₅ a could maximally activate MAPK and AKT at lower concentrations where VEGFA ₁₆₅ b had relatively little effect. The timing for maximum activation of MAPK was similar for the isoforms, which is different from that reported for non-retinal endothelial cells. Although differences in VEGFA ₁₆₅ a and VEGFA ₁₆₅ b are limited to the sequence of their six C-terminal six amino acids, this results in a large difference in their ability to activate at least two key intracellular signaling pathways and VEGF-target gene expression in primary human retinal endothelial cells.

Tear Fluid Angiogenic Factors: Potential Noninvasive Biomarkers for Retinopathy of Prematurity Screening in Preterm Infants

Purpose

To determine the status of proangiogenic factors in the tear fluid of preterm infants with and without retinopathy of prematurity (ROP).

Methods

Preterm infants (n = 36) undergoing routine ROP screening included in the prospective study were categorized as No-ROP (n = 13, no ROP at any visits), ROP (if ROP was present at first visit; n = 18), or No-ROP to ROP (no disease at first visit, but developed ROP subsequently; n = 5). Infants with ROP were also grouped as progressing (n = 7) and regressing (n = 16) based on ROP evolution between the first and subsequent visits. Schirmer's strips were used to collect tear fluid and proangiogenic factors (VEGF, angiogenin, soluble vascular cell adhesion molecule, and fractalkine) levels (in picograms per milliliter) in tear fluid were measured by multiplex ELISA.

Results

Lower levels of VEGF (135 ± 69; mean ± standard deviation) and higher levels of angiogenin (6568 ± 4975) were observed in infants with ROP compared with infants without ROP (172.5 ± 54.0; 4139 ± 3909) at the first visit. Significantly lower levels of VEGF were observed in the No-ROP to ROP group compared with the No-ROP and ROP groups. The VEGF and angiogenin levels at the first visit were significantly lower in infants with ROP with progressing disease. Angiogenin levels negatively correlated with birth weight and gestational age in ROP. The area under the curve (AUC) and odds ratio (OR) analysis demonstrated that angiogenin/birth weight (AUC = 0.776; OR, 8.6); angiogenin/gestational age (AUC = 0.706; OR, 7.3) and Angiogenin/VEGF (AUC = 0.806; OR, 14.3) ratios were able to differentiated preterm infants with and without ROP.

Conclusions

The association between angiogenin and ROP suggests its possible role in ROP. The ratio of angiogenin level with birth weight, gestational age, and/or VEGF could serve as a potential noninvasive screening biomarker for ROP.

Toward the Clinical Application of Therapeutic Angiogenesis Against Pediatric Ischemic Retinopathy

Therapeutic angiogenesis refers to strategies of inducing angiogenesis to treat diseases involving ischemic conditions. Historically, most attempts and achievements have been related to coronary and peripheral artery diseases. In this review, we propose the clinical application of therapeutic angiogenesis for the treatment of pediatric ischemic retinopathy, including retinopathy of prematurity, familial exudative retinopathy, and NDP-related retinopathy. These diseases are all characterized by the reduction of physiological angiogenesis and the following induction of pathological angiogenesis. Therapeutic angiogenesis, which supplements insufficient physiological angiogenesis, may be a therapeutic approach for ischemic conditions. Various molecules and modalities can be utilized to apply therapeutic angiogenesis for the treatment of ischemic retinopathy, as in coronary and peripheral artery diseases. Experiences with cardiovascular diseases provide a useful reference for the further clinical application of therapeutic angiogenesis in pediatric ischemic retinopathy. Recombinant proteins and gene therapy are powerful tools to deliver angiogenic factors to retinal tissues directly. Furthermore, endothelial progenitor or bone marrow-derived cells can be injected into the vitreous cavity of the eye for therapeutic angiogenesis. Intraocular injections are highly promising for the delivery of therapeutics for therapeutic angiogenesis. We expect that therapeutic angiogenesis will be a breakthrough in the treatment of pediatric ischemic retinopathy.

Serum levels of cytokines in infants treated with conbercept for retinopathy of prematurity

Intravitreal anti-vascular endothelial growth factor (VEGF) agents have revolutionized the treatment of retinopathy of prematurity (ROP); however, there are concerns regarding the potential systemic complications caused by those treatments. This study aimed to determine the serum concentrations of cytokines in infants with ROP and to evaluate the changes in serum VEGF concentrations after intravitreal conbercept (IVC). Sixty infants with ROP treated with IVC 0.25 mg were included. Blood samples were collected before treatment as well as 1 week and 4 weeks after treatment. Serum levels of 45 types of cytokines were measured by a multiplex bead assay. We observed that IVC 0.25 mg in ROP patients suppressed the circulating levels of VEGF-A and VEGF-D as of 1 week after injection, and these growth factor levels returned to baseline at 4 weeks. No significant differences were observed in the serum levels of the other cytokines between baseline and 1 or 4 weeks after IVC.

Newly Identified Peptide, Peptide Lv, Promotes Pathological Angiogenesis

Background We recently discovered a small endogenous peptide, peptide Lv, with the ability to activate vascular endothelial growth factor receptor 2 and its downstream signaling. As vascular endothelial growth factor through vascular endothelial growth factor receptor 2 contributes to normal development, vasodilation, angiogenesis, and pathogenesis of various diseases, we investigated the role of peptide Lv in vasodilation and developmental and pathological angiogenesis in this study. Methods and Results The endothelial cell proliferation, migration, and 3-dimensional sprouting assays were used to test the abilities of peptide Lv in angiogenesis in vitro. The chick chorioallantoic membranes and early postnatal mice were used to examine its impact on developmental angiogenesis. The oxygen-induced retinopathy and laser-induced choroidal neovascularization mouse models were used for in vivo pathological angiogenesis. The isolated porcine retinal and coronary arterioles were used for vasodilation assays. Peptide Lv elicited angiogenesis in vitro and in vivo. Peptide Lv and vascular endothelial growth factor acted synergistically in promoting endothelial cell proliferation. Peptide Lv-elicited vasodilation was not completely dependent on nitric oxide, indicating that peptide Lv had vascular endothelial growth factor receptor 2/nitric oxide-independent targets. An antibody against peptide Lv, anti-Lv, dampened vascular endothelial growth factor-elicited endothelial proliferation and laser-induced vascular leakage and choroidal neovascularization. While the pathological angiogenesis in mouse eyes with oxygen-induced retinopathy was enhanced by exogenous peptide Lv, anti-Lv dampened this process. Furthermore, deletion of peptide Lv in mice significantly decreased pathological neovascularization compared with their wild-type littermates. Conclusions These results demonstrate that peptide Lv plays a significant role in pathological angiogenesis but may be less critical during development. Peptide Lv is involved in pathological angiogenesis through vascular endothelial growth factor receptor 2-dependent and -independent pathways. As anti-Lv dampened the pathological angiogenesis in the eye, anti-Lv may have a therapeutic potential to treat pathological angiogenesis.

Role of VEGF165b/VEGFTOTAL ratio in gestational diabetes mellitus

Proper vascular function is important for well-being of mother and growing fetus. VEGF_TOTAL, and VEGF_165b levels and its vascular endothelial complications in gestational diabetes mellitus (GDM) together with the association of inflammation and advanced glycation end products (AGEs) are less studied. VEGF_165b/VEGF_TOTAL (VEGF RATIO) in GDM pregnant women was investigated in this study. Plasma VEGF_TOTAL was lower in GDM (17.68 ± 1.30 pg/mL) compared to non-GDM (25.69 ± 1.40 pg/mL). VEGF_165b, ICAM-1, and AGEs were higher in GDM (9.9 ± 1.4 pg/mL, 201.04 ± 7.85 µg/mL, and 10.40 ± 0.98 µg/mL, respectively) and lower in non-GDM (6.47 ± 0.70 pg/mL, 174.1 ± 7.11 µg/mL, and 4.71 ± 0.39 µg/mL, respectively). Compared to non GDM (0.25 ± 0.02), VEGF RATIO was higher in GDM (0.45 ± 0.04) and correlated with -ICAM-1 (r = 0.375, p < .001) and AGEs (r = 0.199, p < .05). Tertile stratification of VEGF RATIO implied that frequency of GDM increases with increasing tertiles of VEGF RATIO (p for trend <.001). Association of VEGF RATIO with GDM was significant even after adjusting for AGEs (OR = 1.279, CI = 1.118-1.462, p < .0010) but it lost its significance when adjusted for ICAM-1 (OR = 1.006, CI = 0.995-1.017, p = .308). VEGF RATIO plays an important role in GDM in association with vascular inflammation.

Intravitreal Ranibizumab Injection for the Treatment of Retinopathy of Prematurity

OBJECTIVES

To evaluate the efficacy of a single injection of 0.3 mg intravitreal ranibizumab for the treatment of retinopathy of prematurity (ROP).

METHODS

We conducted this retrospective case series study at King Abdul Aziz Medical City, Riyadh, Saudi Arabia. Seventy-four eyes of 37 preterm infants with ROP stage III with plus disease in zone I, posterior zone II, and aggressive posterior ROP received a single injection of 0.3 mg intravitreal ranibizumab. The favorable outcome measure was complete regression of the disease with normal vascularization of the retina of those infants.

RESULTS

The gestational age of the 37 included cases was in the range of 23-28 weeks and their body weight at birth was between 510 and 1,235 g except for one case with 2,550 g under oxygen therapy <7days with severe hypoglycemia. All eyes showed a favorable response in terms of regression of plus disease from the first day after treatment, followed by regression of stage III retinopathy. All patients developed complete vascularization over variable periods of time.

CONCLUSION

One injection of 0.3 mg intravitreal ranibizumab is effective in treating ROP stage III mainly in zones I and II.

The treatment and risk factors of retinopathy of prematurity in neonatal intensive care units

Background

Retinopathy of prematurity (ROP) is a vascular proliferative disorder of the developing retina and a significant cause of childhood blindness around the world. The incidence of ROP is affected by many factors, and the incidence rate varies from country to country. The purpose of this study is to report the incidence and risk factors of ROP in neonatal intensive care unit (NICU) of Guangzhou First People’s Hospital in China.

Methods

A retrospective review was performed on 436 premature infants who were consecutive ROP screened in the NICU of Guangzhou First People’s Hospital from March 2013 to October 2017. The single-factor analysis and the logistic multivariate regression analysis were used to detect risk factors of ROP.

Results

Total 436 premature infants were consecutive ROP screened, 138 (31.65%) were found ROP, and 61(13.99%) were treated. The single-factor analysis revealed that the incidence of ROP was associated with multiple births, gestational age, birth weight, mechanical ventilation, intravascular hemolysis, the number of operations and blood culture results. The logistic multivariate regression analysis revealed that gestational age; birth weight, mechanical ventilation, minimum SaO2 and daily weight gain were independent risk factors for ROP onset. Forty-nine patients underwent retinal laser photocoagulation with recurrence 20 patients. Twelve patients underwent anti-VEGF drug (Ranibizumab) via intraocular injection with 5 patients of recurrence.

Conclusions

The incidence of ROP in NICU of Guangzhou China will match those in middle-income countries, but higher than high-income countries. Anti-VEGF drugs could be preferred as a good treatment method for zone 1 ROP and aggressive posterior ROP.

SERUM LEVELS OF VASCULAR ENDOTHELIAL GROWTH FACTOR BEFORE AND AFTER INTRAVITREAL INJECTION OF RANIBIZUMAB OR CONBERCEPT FOR NEOVASCULAR AGE-RELATED MACULAR DEGENERATION

OBJECTIVE

To investigate the serum levels of vascular endothelial growth factor (VEGF) before and after intravitreal injection of conbercept or ranibizumab for neovascular age-related macular degeneration and polypoidal choroidal vasculopathy patients.

METHODS

This study is a prospective, interventional case series and involved 28 patients, 18 treated with 0.5 mg of conbercept and 10 treated with 0.5 mg of ranibizumab. Serum concentrations of VEGF were determined by enzyme-linked immunosorbent assay before the injection and at 1 day, 1 week, and 1 month after anti-VEGF treatments.

RESULTS

The baseline serum VEGF level of the ranibizumab group was 367.11 ± 311.87 pg/mL, whereas that of the conbercept group was 315.06 ± 170.88 pg/mL (P = 0.653). In the conbercept group, VEGF level significantly decreased to 36.32 ± 72.11 pg/mL at 1 day (P = 0.03) and returned to 136.55 ± 144.62 pg/mL at 1 week (P = 0.03). At 1 month, the concentration increased to 334.48 ± 197.41 pg/mL and showed no significant difference compared with the baseline. In the ranibizumab group, the serum VEGF levels were 292.42 ± 239.80 pg/mL, 282.60 ± 201.36 pg/mL, and 308.83 ± 266.89 pg/mL at 1 day, 1 week, and 1 month after intravitreal injection, respectively. There was no significant difference in the ranibizumab group at each detection time point (P = 0.45).

CONCLUSION

Conbercept significantly decreased serum VEGF level 1 day and 1 week after injection, but this effect was not sustained for 1 month. In contrast, ranibizumab had no significant effect on serum VEGF concentration changes. The reduction in serum VEGF by conbercept may affect its systemic safety profile.

Insulin-Like Growth Factor Binding Protein-Related Protein 1 Inhibit Retinal Neovascularization in the Mouse Model of Oxygen-Induced Retinopathy

PURPOSE

To explore the inhibitory effect of insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) on retinal angiogenesis and its underlying molecular mechanisms in the mouse model of oxygen-induced retinopathy (OIR).

METHODS

C57BL/6J mice were classified into three groups as control group, OIR nonintervention group, and OIR intervention group. Postnatal day 12 (P12) mice in OIR intervention group were received recombinant mouse IGFBP-rP1 (50, 100, and 200 ng/mL) intravitreal injection. Five days later, the proliferative neovascular responses were estimated by quantifying the new vessel areas in flattening retinal tissues stained by high molecular fluorescein isothiocyanate-dextran and counting the numbers of neovascular cell nuclei breaking through the internal limiting membrane in cross sections. Expressions of phospho-extracellular signal-regulated kinase 1/2 (p-ERK1/2), ERK1/2, and vascular endothelial growth factor (VEGF) proteins in retinal tissues were assessed by western blot analysis.

RESULTS

Irregular neovascularization, nonperfusion region, and fluorescence leakage were observed in OIR models. The expression of retinal p-ERK1/2 and VEGF proteins were significantly upregulated in OIR nonintervention group compared with control group. The area ratio of retinal new vessels and the number of neovascular cell nuclei in OIR intervention group both decreased significantly, following the downregulation of retinal p-ERK1/2 protein expression and VEGF protein expression in a dose-dependent manner. Moreover, there was no significant difference in retinal ERK1/2 protein expression.

CONCLUSIONS

IGFBP-rP1 inhibits retinal angiogenesis by blocking ERK signaling pathway and downregulating VEGF expression in the mouse model of OIR. It highlights the potential importance of IGFBP-rP1 serving as a target of gene therapy for retinal neovascularization in the future.

Risk of recurrence of retinopathy of prematurity after initial intravitreal ranibizumab therapy

We report our experience with the use of intravitreal ranibizumab for the treatment of retinopathy of prematurity (ROP). A retrospective review was performed on 138 consecutive infants screened at a single centre over 18 months. Intravitreal ranibizumab was offered in selected cases requiring treatment, such as aggressive posterior ROP or poor mydriasis. 2 eyes of 1 infant received intravitreal ranibizumab alone and 8 eyes of 5 infants received combined intravitreal ranibizumab and laser therapy. 3 out of 8 eyes treated initially with intravitreal ranibizumab monotherapy had persistent disease requiring laser therapy, and 3 out of 5 eyes with initial regression suffered disease recurrence at a mean of 7.6 weeks post-injection. 2 eyes treated first with laser followed by intravitreal ranibizumab had disease regression without recurrence. Our cohort demonstrate a significant rate of persistent disease and recurrence in ROP eyes treated initially with intravitreal ranibizumab monotherapy, which is greater and earlier than that reported for intravitreal bevacizumab in the BEAT-ROP study. Intravitreal ranibizumab may be useful as an initial treatment in selected cases of ROP when laser therapy as first line is suboptimal. However, close monitoring is important and adjunctive laser therapy may subsequently be needed in a majority of cases.