Placental growth factor expression is reversed by antivascular endothelial growth factor therapy under hypoxic conditions

Human retinal secretome: A cross-link between mesenchymal and retinal cells

In recent years, mesenchymal stem cells (MSC) have been considered the most effective source for regenerative medicine, especially due to released soluble paracrine bioactive components and extracellular vesicles. These factors, collectively called the secretome, play crucial roles in immunomodulation and in improving survival and regeneration capabilities of injured tissue. Recently, there has been a growing interest in the secretome released by retinal cytotypes, especially retinal pigment epithelium and Müller glia cells. The latter trophic factors represent the key to preserving morphofunctional integrity of the retina, regulating biological pathways involved in survival, function and responding to injury. Furthermore, these factors can play a pivotal role in onset and progression of retinal diseases after damage of cell secretory function. In this review, we delineated the importance of cross-talk between MSCs and retinal cells, focusing on common/induced secreted factors, during experimental therapy for retinal diseases. The cross-link between the MSC and retinal cell secretomes suggests that the MSC secretome can modulate the retinal cell secretome and vice versa. For example, the MSC secretome can protect retinal cells from degeneration by reducing oxidative stress, autophagy and programmed cell death. Conversely, the retinal cell secretome can influence the MSC secretome by inducing changes in MSC gene expression and phenotype.

Retinopathy of prematurity: A review of pathophysiology and signaling pathways

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

Effects of Anti-Vascular Endothelial Growth Factor Drugs Before and After Pars Plana Vitrectomy in Patients with Polypoidal Choroidal Vasculopathy and Vitreous Hemorrhage

Purpose: To compare the clinical effects of postoperative versus perioperative injection of anti-vascular endothelial growth factor (VEGF) drugs before and after pars plana vitrectomy (PPV) in patients with vitreous hemorrhage secondary to polypoidal choroidal vasculopathy (PCV). Methods: This was a retrospective study of patients who underwent PPV due to vitreous hemorrhage between October 2013 and June 2019 at Ningbo Eye Hospital. The patients who underwent PPV surgery due to PCV-secondary vitreous hemorrhage were included. The primary outcome was the changes in best-corrected visual acuity. The secondary outcome was the central macular thickness. Results: Compared with the postoperative group (n = 20), the perioperative group (n = 18) showed a smaller number of postoperative anti-VEGF injections (5.1 ± 0.8 vs. 8.0 ± 1.5, P < 0.05) and lower frequencies of early hyphema (5.6% vs. 30.0%, P < 0.05), and recurrent vitreous hemorrhage (11.1% vs. 30.0%, P < 0.05). The logarithm of minimal angle resolution (LogMAR) was smaller in the perioperative group compared with the postoperative group at 1 week, 1 month, and 3 months after PPV (P < 0.05), but there were no differences thereafter. Compared with the postoperative group, the perioperative group had thinner fovea at 1 week, 1 month, and 3 months (P < 0.05), but the differences disappeared after 3 months. Conclusion: In patients with PCV and vitreous hemorrhage, compared with postoperative anti-VEGF, perioperative anti-VEGF could reduce the difficulty of surgery and reduce the occurrence of postoperative complications, but there were no differences in long-term vision and macular thickness after surgery.

Angiographic Review of Choroidal Involution in Eyes with Retinopathy of Prematurity Treated with Bevacizumab

PURPOSE

Retinopathy of prematurity (ROP) is considered a disease of the inner retina; however, there is increasing evidence that demonstrates choroidal vasculature loss in ROP, leading to degeneration of outer retinal function and visual deterioration. Central choroidal thinning is noted in children with history of ROP using optical coherence tomography (OCT) imaging. This study characterizes the presence and persistence of choroidal loss angiographically in eyes of infants treated with intravitreal bevacizumab (IVB) for stage 3 ROP.

METHODS

Retrospectively reviewed the fluorescein angiography (FA) images of 62 eyes of 31 infants treated with IVB monotherapy. The eyes with good quality early-, mid-, and late-phase imaging were included in this study. The presence of choroidal hypofluoresence involving the central and or peripheral retina were noted. In infants with multiple FAs, serial FAs were analyzed for persistence of choroidal hypofluorescence.

RESULTS

The mean age and birth weight of infants was 24.4 weeks PMA and 683 grams, respectively. All infants received IVB monotherapy. 24 of 62 angiography images of sufficient quality reviewed showed the presence of choroidal hypofluorescence involving central and peripheral lobular loss in the early phase and its persistence into mid and late phases. 12 eyes demonstrated persistent choroidal loss on sequential FA until three years chronological age.

CONCLUSIONS

The study demonstrates the presence of choroidal vascular loss angiographically both central and peripheral fundus in infants with ROP. It highlights the critical role of choroidal involution in outer retinal function that could affect visual outcomes.

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.

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.

Anti-angiogenic Therapy for Retinal Disease

Recent breakthroughs in our understanding of the molecular pathophysiology of retinal vascular disease have allowed us to specifically target pathological angiogenesis while minimizing damage to the neurosensory retina. This is perhaps best exemplified by the development of therapies targeting the potent angiogenic growth factor and vascular permeability mediator, vascular endothelial growth factor (VEGF). Anti-VEGF therapies, initially introduced for the treatment of choroidal neovascularization in patients with age-related macular degeneration, have also had a dramatic impact on the management of retinal vascular disease and are currently an indispensable component for the treatment of macular edema in patients with diabetic eye disease and retinal vein occlusions. Emerging evidence supports expanding the use of therapies targeting VEGF for the treatment of retinal neovascularization in patients with diabetic retinopathy and retinopathy of prematurity. However, VEGF is among a growing list of angiogenic and vascular hyperpermeability factors that promote retinal vascular disease. Many of these mediators are expressed in response to stabilization of a single family of transcription factors, the hypoxia-inducible factors (HIFs), that regulate the expression of these angiogenic stimulators. Here we review the basic principles driving pathological angiogenesis and discuss the current state of retinal anti-angiogenic pharmacotherapy as well as future directions.

Different effects of various anti-angiogenic treatments in an experimental mouse model of retinopathy of prematurity

BACKGROUND

Anti-vascular endothelial growth factor (VEGF) drugs are an option for the treatment of retinopathy of prematurity (ROP). Blocking of other angiogenic factors is also of interest. We therefore investigated in which effects would result blocking of placental growth factor (PlGF).

METHODS

C57BL/6 mice were exposed to 75% oxygen from P7 to P12. Intravitreal injections were performed at P12. Mice of control groups remained untouched after oxygen treatment, or phosphate buffered saline or neutral IgG molecules were injected. In the treatment groups, antibodies against VEGF or PlGF, a mixture of anti-VEGF and anti-PlGF, aflibercept or sunitinib were injected. On P17, electroretinographic (ERG) measurements were performed. Avascular zones and neovascularization were evaluated in retinal flat-mounts. Results are expressed as percent of total retinal area (median with median absolute deviation, MAD).

RESULTS

Eyes of control groups showed similar neovascularization (1.4-3.3%, MAD 0.4-0.9%). Neovascularization was significantly less (0.5-0.7%, MAD 0.1-0.3%) in all treatment groups. Avascular zones in the retinas of control groups showed similar values (18.3-25.7%, MAD 4.8-8.8%). Avascular zones were significantly reduced down to 3.6 ± 1.3% after anti-VEGF injection, but they were not reduced significantly in the other treatment groups (13.3-22%, MAD 3.6-6.1%). ERG measurements did not reveal significant differences between the controls and the treatment groups.

CONCLUSIONS

Blocking of PlGF or injection of sunitinib results in a similar inhibition of neovascularization as by anti-VEGF treatment in the mouse model of ROP. However, physiological angiogenesis that occurs after anti-VEGF treatment is blocked by anti-PlGF or sunitinib treatment, indicating that pathological neovascularization may follow different pathways than physiological angiogenesis.

Identification of proteins associated with clinical and pathological features of proliferative diabetic retinopathy in vitreous and fibrovascular membranes

Purpose

To identify the protein profiles in vitreous associated with retinal fibrosis, angiogenesis, and neurite formation in epiretinal fibrovascular membranes (FVMs) in patients with proliferative diabetic retinopathy (PDR).

Methods

Vitreous samples of 5 non-diabetic control patients with vitreous debris and 7 patients with PDR membranes were screened for 507 preselected proteins using the semi-quantitative RayBio® L-series 507 antibody array. From this array, 60 proteins were selected for a custom quantitative antibody array (Raybiotech, Human Quantibody® array), analyzing 7 control patients, 8 PDR patients with FVMs, and 5 PDR patients without FVMs. Additionally, mRNA levels of proteins of interest were measured in 10 PDR membranes and 11 idiopathic membranes and in retinal tissues and cells to identify possible sources of protein production.

Results

Of the 507 proteins screened, 21 were found to be significantly elevated in PDR patients, including neurogenic and angiogenic factors such as neuregulin 1 (NRG1), nerve growth factor receptor (NGFR), placental growth factor (PlGF) and platelet derived growth factor (PDGF). Angiopoietin-2 (Ang2) concentrations were strongly correlated to the degree of fibrosis and the presence of FVMs in patients with PDR. Protein correlation analysis showed PDGF to be extensively co-regulated with other proteins, including thrombospondin-1 and Ang2. mRNA levels of glial-derived and brain/derived neurotrophic factor (GDNF and BDNF) were elevated in PDR membranes. These results were validated in a second study of 52 vitreous samples of 32 PDR patients and 20 control patients.

Conclusions

This exploratory study reveals protein networks that potentially contribute to neurite outgrowth, angiogenesis and fibrosis in the formation of fibrovascular membranes in PDR. We identified a possible role of Ang2 in fibrosis and the formation of FVMs, and of the neurotrophic factors NRG1, PDGF and GDNF in neurite growth that occurs in all FVMs in PDR.

Retinopathy of prematurity: inflammation, choroidal degeneration, and novel promising therapeutic strategies

Retinopathy of prematurity (ROP) is an important cause of childhood blindness globally, and the incidence is rising. The disease is characterized by initial arrested retinal vascularization followed by neovascularization and ensuing retinal detachment causing permanent visual loss. Although neovascularization can be effectively treated via retinal laser ablation, it is unknown which children are at risk of entering this vision-threatening phase of the disease. Laser ablation may itself induce visual field deficits, and there is therefore a need to identify targets for novel and less destructive treatments of ROP. Inflammation is considered a key contributor to the pathogenesis of ROP. A large proportion of preterm infants with ROP will have residual visual loss linked to loss of photoreceptor (PR) and the integrity of the retinal pigment epithelium (RPE) in the macular region. Recent studies using animal models of ROP suggest that choroidal degeneration may be associated with a loss of integrity of the outer retina, a phenomenon so far largely undescribed in ROP pathogenesis. In this review, we highlight inflammatory and neuron-derived factors related to ROP progression, as well, potential targets for new treatment strategies. We also introduce choroidal degeneration as a significant cause of residual visual loss following ROP. We propose that ROP should no longer be considered an inner retinal vasculopathy only, but also a disease of choroidal degeneration affecting both retinal pigment epithelium and photoreceptor integrity.

Smouldering retinopathy of prematurity: a case treated by multiple antivascular endothelial growth factor therapy

A 13 months old female baby born at 24 weeks of gestational age (GA) presented with stage 4A retinopathy of prematurity (ROP) with plus disease in the right eye and stage 3 with plus disease in the left eye. The baby was diagnosed with stage 3 zone 2 ROP in both eyes with plus disease at 32 weeks of GA and received intravitreal bevacizumab in both eyes. The baby received intravitreal bevacizumab and ranibizumab injections at 39 and 57 weeks of postmenstrual age (PMA), respectively for recurrence. Laser treatment to peripheral avascular retina was carried out at 67 weeks of PMA. The right eye progressed to stage 4A and left eye developed pre-retinal haemorrhages. This case reports late recurrence treated with initial multiple antivascular endothelial growth factor (VEGF) injections alone. One should be cautious in using anti-VEGF agents as a monotherapy in cases of ROP that appear different from the current understanding of the natural course of the disease.