Inhibition of oxygen-induced ischemic retinal neovascularization with adenoviral 15-lipoxygenase-1 gene transfer via up-regulation of PPAR-γ and down-regulation of VEGFR-2 expression

Corneal Regeneration Using Gene Therapy Approaches

One of the most remarkable advancements in medical treatments of corneal diseases in recent decades has been corneal transplantation. However, corneal transplants, including lamellar strategies, have their own set of challenges, such as graft rejection, delayed graft failure, shortage of donor corneas, repeated treatments, and post-surgical complications. Corneal defects and diseases are one of the leading causes of blindness globally; therefore, there is a need for gene-based interventions that may mitigate some of these challenges and help reduce the burden of blindness. Corneas being immune-advantaged, uniquely avascular, and transparent is ideal for gene therapy approaches. Well-established corneal surgical techniques as well as their ease of accessibility for examination and manipulation makes corneas suitable for in vivo and ex vivo gene therapy. In this review, we focus on the most recent advances in the area of corneal regeneration using gene therapy and on the strategies involved in the development of such therapies. We also discuss the challenges and potential of gene therapy for the treatment of corneal diseases. Additionally, we discuss the translational aspects of gene therapy, including different types of vectors, particularly focusing on recombinant AAV that may help advance targeted therapeutics for corneal defects and diseases.

Annexin A2 promotes development of retinal neovascularization through PI3K/ AKT signaling pathway

PURPOSE

Retinal Neovascularization (RNV) is a pathological characteristic of ocular diseases. Annexin A2 (ANXA2) plays important roles in RNV while the mechanism remains unclear. The study aimed to explore relationship between ANXA2 and PI3K/AKT signaling pathway in RNV.

METHODS

We used human retinal vascular endothelial cells (HRECs) and oxygen-induced retinopathy (OIR) mice model to show ANXA2 can promote the development of RNV through PI3K/AKT signaling pathway. We divided HRECs into six groups by infecting lentivirus containing appropriate plasmid and adding corresponding solution. Assays showing ability of HRECs were performed in vitro. Mice were randomly divided into three groups and treated accordingly.

RESULTS

Expression of ANXA2 and activity of PI3K/AKT signaling pathway in HRECs were detected. RNV and expression of ANXA2 in mice retinas were detected. Results showed that ANXA2 expression is positively related with RNV-forming ability of HRECs in vitro and development of RNV in vivo while low activity of PI3K/AKT signaling pathway could attenuate the role of ANXA2.

CONCLUSIONS

We can make ANXA2 and PI3K/ AKT signaling pathway as a promising target for the regulation of pathological neovascularization of the retina, which also provides a novel idea for effective prevention and treatment of diseases related to RNV in future.

Efficacy of Vincamine treatment in a rat model of anterior ischemic optic neuropathy

Non-arteritic anterior ischemic optic neuropathy (NAION) is characterized by the progressive and irreversible death of retinal ganglion cells (RGCs) which is caused by the insufficient blood supply to the optic nerve (ON) head. At present, hormone therapy is used to reduce optic edema, followed by nerve nutrition therapy to protect the ON. However, no surgical or medical therapy has proven to be beneficial consistently in treating NAION. Vincamine is an alkaloid extracted from the Apocynaceae Vinca plant. Vincamine and its derivatives acting as cerebral vasodilators can easily cross the blood-brain barrier, improve the metabolism of ischemic tissue and protect the neuron. In this study, we aimed to investigate the potential neuroprotection of Vincamine in the photodynamic induced rat model of NAION (rAION), to evaluate its effects and possible mechanisms. We found that Vincamine can rescue RGC death and reduce the number of apoptotic cells. The protection of Vincamine might play through the PI3K/Akt/eNOS signaling pathway. Therefore, Vincamine can be an effective therapy method for NAION.

The G-protein-coupled chemoattractant receptor Fpr2 exacerbates neuroglial dysfunction and angiogenesis in diabetic retinopathy

Diabetic retinopathy (DR) as a retinal neovascularization‐related disease is one of the leading causes of irreversible blindness in patients. The goal of this study is to determine the role of a G‐protein‐coupled chemoattractant receptor (GPCR) FPR2 (mouse Fpr2) in the progression of DR, in order to identify novel therapeutic targets. We report that Fpr2 was markedly upregulated in mouse diabetic retinas, especially in retinal vascular endothelial cells, in associated with increased number of activated microglia and Müller glial cells. In contrast, in the retina of diabetic Fpr2^−/− mice, the activation of vascular endothelial cells and glia was attenuated with reduced production of proinflammatory cytokines. Fpr2 deficiency also prevented the formation of acellular capillary during diabetic progression. Furthermore, in oxygen‐induced retinopathy (OIR) mice, the absence of Fpr2 was associated with diminished neovasculature formation and pathological vaso‐obliteration region in the retina. These results highlight the importance of Fpr2 in exacerbating the progression of neuroglial degeneration and angiogenesis in DR and its potential as a therapeutic target.

PPARs and Angiogenesis-Implications in Pathology

Peroxisome proliferator-activated receptors (PPARs) belong to the family of ligand-activated nuclear receptors. The PPAR family consists of three subtypes encoded by three separate genes: PPARα (NR1C1), PPARβ/δ (NR1C2), and PPARγ (NR1C3). PPARs are critical regulators of metabolism and exhibit tissue and cell type-specific expression patterns and functions. Specific PPAR ligands have been proposed as potential therapies for a variety of diseases such as metabolic syndrome, cancer, neurogenerative disorders, diabetes, cardiovascular diseases, endometriosis, and retinopathies. In this review, we focus on the knowledge of PPAR function in angiogenesis, a complex process that plays important roles in numerous pathological conditions for which therapeutic use of PPAR modulation has been suggested.

PPARG Polymorphisms Are Associated with Unexplained Mild Vision Loss in Patients with Type 2 Diabetes Mellitus

Objectives

To investigate whether the presence of peroxisome proliferator-activated receptor gamma (PPARG) gene polymorphisms is associated with unexplained mild visual impairment (UMVI) in patients with type 2 diabetes mellitus (T2DM).

Methods

A total of 135 T2DM residents with UMVI and 133 with normal vision (NV; best-corrected visual acuity ≥ 20/25 in both eyes) were enrolled. UMVI was defined as best-corrected visual acuity (BCVA) < 20/25 and ≥ 20/63 in both eyes, with no visual impairment-causing diseases found. Four PPARG gene single-nucleotide polymorphisms (SNPs) (rs3856806, rs1801282, rs709158, and rs10865710) were assessed with the HAPLOVIEW 4.0 software to examine the statistical association of PPARG polymorphisms and UMVI in patients with T2DM.

Results

Four SNPs qualified the Hardy-Weinberg equilibrium (p > 0.05). The frequency of genotype GC at SNP rs10865710 was significantly higher in the UMVI group than in the NV group (p < 0.001; GG + GC versus CC) (OR = 8.94, 95% CI: 4.90-16.31), whereas genotype CC decreased the risk (OR = 0.07, 95% CI: 0.03-0.14). Genotype TT at SNP rs3856806 was strongly associated with UMVI (p < 0.0001, TT + TC versus CC) (OR = 4.74, 95% CI: 2.68-8.54), whereas genotype CC appeared to be protective for UMVI (OR = 0.55, 95% CI: 0.37-0.82).

Conclusions

Susceptibilities of PPARG variants may lead to differences in PPARG transcription, result in early function loss of retinal photoreceptor cells, and eventually cause UMVI.

Is There A Role for Abscisic Acid, A Proven Anti-Inflammatory Agent, in the Treatment of Ischemic Retinopathies?

Ischemic retinopathies (IRs) are the main cause of severe visual impairment and sight loss, and are characterized by loss of blood vessels, accompanied by hypoxia, and neovascularization. Actual therapies, based on anti-vascular endothelial growth factor (VEGF) strategies, antioxidants or anti-inflammatory therapies are only partially effective or show some adverse side effects. Abscisic acid (ABA) is a phytohormone present in vegetables and fruits that can be naturally supplied by the dietary intake and has been previously studied for its benefits to human health. It has been demonstrated that ABA plays a key role in glucose metabolism, inflammation, memory and tumor growth. This review focuses on a novel and promising role of ABA as a potential modulator of angiogenesis, oxidative status and inflammatory processes in the retina, which are the most predominant characteristics of the IRs. Thus, this nutraceutical compound might shed some light in new therapeutic strategies focused in the prevention or amelioration of IRs-derived pathologies.

Emerging cellular functions of the lipid metabolizing enzyme 15-Lipoxygenase-1

The oxygenation of polyunsaturated fatty acids such as arachidonic and linoleic acid through lipoxygenases (LOXs) and cyclooxygenases (COXs) leads to the production of bioactive lipids that are important both in the induction of acute inflammation and its resolution. Amongst the several isoforms of LOX that are expressed in mammals, 15-LOX-1 was shown to be important both in the context of inflammation, being expressed in cells of the immune system, and in epithelial cells where the enzyme has been shown to crosstalk with a number of important signalling pathways. This review looks into the latest developments in understanding the role of 15-LOX-1 in different disease states with emphasis on the emerging role of the enzyme in the tumour microenvironment as well as a newly re-discovered form of cell death called ferroptosis. We also discuss future perspectives on the feasibility of use of this protein as a target for therapeutic interventions.

Exogenous erythropoietin aggravates retinal neovascularizationin a murine model of proliferative retinopathy

Background/aim: Erythropoietin (EPO) has been proven recently to be a critical mediator in retinal neovascularization (RNV). Previous studies have indicated that the use of recombinant human EPO (rEPO) is a high risk factor in the development of retinopathy of prematurity. In this study, we aimed to investigate the effect of rEPO administration on RNV and its underlying mechanism in a mouse model of oxygen-induced retinopathy (OIR). Materials and methods: A murine model of OIR was used to generate RNV. After daily intraperitoneal injection of rEPO from postnatal day 12 (P12), mice were euthanized at P17. Whole-mount retina staining was used to indicate the nonperfused area and neovascularization tufts. Preretinal neovascular cells were calculated through hematoxylin and eosin staining. The expression levels of vascular endothelial growth factor (VEGF) and inducible nitric oxide synthase (iNOS) were detected via western blot analysis. Results: We found that injection of rEPO promoted the severity of RNV. The areas of neovascular tufts and preretinal neovascular cells were increased after administration of rEPO. When mice were injected with rEPO, a dose-dependent upregulation in VEGF and iNOS was observed. Conclusion: The study indicates the proangiogenic role of EPO, suggesting that rEPO contributes to the pathogenesis of RNV.

Suppression of Retinal Neovascularization by Inhibition of Galectin-1 in a Murine Model of Oxygen-Induced Retinopathy

Galectin-1 (Gal-1) has been proved to be an important factor in the process of tumor angiogenesis recently. As a small molecule, OTX008 serves as a selective inhibitor of Gal-1. In this study, the role of Gal-1 and the antiangiogenic effect of OTX008 on retinal neovascularization (RNV) were investigated using a mouse model of oxygen-induced retinopathy. The outcome indicated that Gal-1 was overexpressed and closely related to retinal neovessels in OIR. After intravitreal injection of OTX008 at P12, the RNV was significantly reduced at P17, measuring by cross-sectional H&E staining and whole-mount fluorescence. Our results demonstrate the inhibitory function of OTX008 on RNV, which provides a promising strategy of treating retinal angiogenic diseases such as retinopathy of prematurity and proliferative diabetic retinopathy.