Diabetic retinopathy: a complex pathophysiology requiring novel therapeutic strategies

Exploring the Pharmacological Mechanism of Liuwei Dihuang Decoction for Diabetic Retinopathy: A Systematic Biological Strategy-Based Research

OBJECTIVE

To explore the pharmacological mechanism of Liuwei Dihuang decoction (LDD) for diabetic retinopathy (DR).

METHODS

The potential targets of LDD were predicted by PharmMapper. GeneCards and other databases were used to collect DR genes. Cytoscape was used to construct and analyze network DR and LDD's network, and DAVID was used for Gene Ontology (GO) and pathway enrichment analysis. Finally, animal experiments were carried out to verify the results of systematic pharmacology.

RESULTS

Five networks were constructed and analyzed: (1) diabetic retinopathy genes' PPI network; (2) compound-compound target network of LDD; (3) LDD-DR PPI network; (4) compound-known target network of LDD; (5) LDD known target-DR PPI network. Several DR and treatment-related targets, clusters, signaling pathways, and biological processes were found. Animal experiments found that LDD can improve the histopathological changes of the retina. LDD can also increase erythrocyte filtration rate and decrease the platelet adhesion rate (P < 0.05) and decrease MDA and TXB2 (P < 0.05). Compared with the model group, the retinal VEGF and HIF-1α expression in the LDD group decreased significantly (P < 0.05).

CONCLUSION

The therapeutic effect of LDD on DR may be achieved by interfering with the biological processes (such as response to insulin, glucose homeostasis, and regulation of angiogenesis) and signaling pathways (such as insulin, VEGF, HIF-1, and ErbB signaling pathway) related to the development of DR that was found in this research.

Inflammatory and angiogenic biomarkers in diabetic retinopathy

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes mellitus (DM) and a leading cause of blindness in working-age adults in developed countries. Numerous investigations have recognised inflammation and angiogenesis as important factors in the development of this complication of diabetes. Current methods of DR treatment are predominantly used at advanced stages of the disease and could be associated with serious side effects. Therefore, new diagnostic methods are needed in order to identify the initial stages of DR as well as monitoring the effects of applied therapy. Biochemical biomarkers are molecules found in blood or other biological fluid and tissue that indicate the existence of an abnormal condition or disease. They could be a valuable tool in detecting early stages of DR, identifying patients most susceptible to retinopathy progression and monitoring treatment outcomes. Biomarkers related to DR can be measured in the blood, retina, vitreous, aqueous humour and recently in tears. As the retina represents a small part of total body mass, a circulating biomarker for DR needs to be highly specific. Local biomarkers are more reliable as indicators of the retinal pathology; however, obtaining a sample of aqueous humour, vitreous or retina is an invasive procedure with potential serious complications. As a non-invasive novel method, tear analysis offers a promising direction in further research for DR biomarker detection. The aim of this paper is to review systemic and local inflammatory and angiogenic biomarkers relevant to this sight threatening diabetic complication.

Gene Therapy Intervention in Neovascular Eye Disease: A Recent Update

Aberrant growth of blood vessels (neovascularization) is a key feature of severe eye diseases that can cause legal blindness, including neovascular age-related macular degeneration (nAMD) and diabetic retinopathy (DR). The development of anti-vascular endothelial growth factor (VEGF) agents has revolutionized the treatment of ocular neovascularization. Novel proangiogenic targets, such as angiopoietin and platelet-derived growth factor (PDGF), are under development for patients who respond poorly to anti-VEGF therapy and to reduce adverse effects from long-term VEGF inhibition. A rapidly advancing area is gene therapy, which may provide significant therapeutic benefits. Viral vector-mediated transgene delivery provides the potential for continuous production of antiangiogenic proteins, which would avoid the need for repeated anti-VEGF injections. Gene silencing with RNA interference to target ocular angiogenesis has been investigated in clinical trials. Proof-of-concept gene therapy studies using gene-editing tools such as CRISPR-Cas have already been shown to be effective in suppressing neovascularization in animal models, highlighting the therapeutic potential of the system for treatment of aberrant ocular angiogenesis. This review provides updates on the development of anti-VEGF agents and novel antiangiogenic targets. We also summarize current gene therapy strategies already in clinical trials and those with the latest approaches utilizing CRISPR-Cas gene editing against aberrant ocular neovascularization.

Importance of the Use of Oxidative Stress Biomarkers and Inflammatory Profile in Aqueous and Vitreous Humor in Diabetic Retinopathy

Diabetic retinopathy is one of the leading causes of visual impairment and morbidity worldwide, being the number one cause of blindness in people between 27 and 75 years old. It is estimated that ~191 million people will be diagnosed with this microvascular complication by 2030. Its pathogenesis is due to alterations in the retinal microvasculature as a result of a high concentration of glucose in the blood for a long time which generates numerous molecular changes like oxidative stress. Therefore, this narrative review aims to approach various biomarkers associated with the development of diabetic retinopathy. Focusing on the molecules showing promise as detection tools, among them we consider markers of oxidative stress (TAC, LPO, MDA, 4-HNE, SOD, GPx, and catalase), inflammation (IL-6, IL-1ß, IL-8, IL-10, IL-17A, TNF-α, and MMPs), apoptosis (NF-kB, cyt-c, and caspases), and recently those that have to do with epigenetic modifications, their measurement in different biological matrices obtained from the eye, including importance, obtaining process, handling, and storage of these matrices in order to have the ability to detect the disease in its early stages.

Oxidative Stress and Vascular Dysfunction in the Retina: Therapeutic Strategies

Many retinal diseases, such as diabetic retinopathy, glaucoma, and age-related macular (AMD) degeneration, are associated with elevated reactive oxygen species (ROS) levels. ROS are important intracellular signaling molecules that regulate numerous physiological actions, including vascular reactivity and neuron function. However, excessive ROS formation has been linked to vascular endothelial dysfunction, neuron degeneration, and inflammation in the retina. ROS can directly modify cellular molecules and impair their function. Moreover, ROS can stimulate the production of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) causing inflammation and cell death. However, there are various compounds with direct or indirect antioxidant activity that have been used to reduce ROS accumulation in animal models and humans. In this review, we report on the physiological and pathophysiological role of ROS in the retina with a special focus on the vascular system. Moreover, we present therapeutic approaches for individual retinal diseases targeting retinal signaling pathways involving ROS.

Intractable Ocular Diseases and Treatment Progress

In recent years, with the aging of the population and the frequent use of electronic devices, many eye diseases have shown a linear upward trend, such as dry eye disease, glaucoma, cataract, age-related macular degeneration, and diabetic retinopathy. These diseases are often chronic and difficult to cure. Based on the structure and barrier of the human eye, this review describes the pathogenesis and treatments of several intractable eye diseases and summarizes the advanced ocular drug delivery systems to provide new treatment ideas for these diseases. Finally, we also look forward to the prospect of RNAi therapy in the treatment of eye diseases.

The potential role of lncRNAs in diabetes and diabetic microvascular complications

Long noncoding RNAs (lncRNAs) are a group of noncoding RNAs that are longer than 200 nucleotides without protein-coding potential. Becasuse of which these RNAs have no significant protein-coding potential, they were initially considered as "junk-products" of transcription without biological meaning. Nevertheless, recent research advancements have shown that lncRNAs are involved in many physiological processes such as cell cycle regulation, cell apoptosis and survival, cancer migration and metabolism. This review described the function of lncRNAs and the potential underlying mechanism involved in diabetes and diabetic microvascular complications. The roles of lncRNAs in the pathogenesis of type 2 diabetes mellitus have only recently been recognized, involving hepatic glucose production and insulin resistance. We further investigated the mechanisms of lncRNAs in diabetic nephropathy (DN), including the roles of lncRNAs in mesangial cells (MCs) proliferation and fibrosis, inflammatory processes, extracellular matrix accumulation in the glomeruli and tubular injury. We also discussed the potential mechanism of lncRNAs in diabetic retinopathy (DR), including aberrant neovascularization and neuronal dysfunction. This review summarized the current knowledge of the functions and underlying mechanisms of lncRNAs in type 2 diabetes mellitus and related renal and retinal complications. Accumulating evidence suggests the potential of lncRNAs as therapeutic targets for clinical applications in the management of diabetes.

Oxidative Stress Induces a VEGF Autocrine Loop in the Retina: Relevance for Diabetic Retinopathy

BACKGROUND

Oxidative stress (OS) plays a central role in diabetic retinopathy (DR), triggering expression and release of vascular endothelial growth factor (VEGF), the increase of which leads to deleterious vascular changes. We tested the hypothesis that OS-stimulated VEGF induces its own expression with an autocrine mechanism.

METHODS

MIO-M1 cells and ex vivo mouse retinal explants were treated with OS, with exogenous VEGF or with conditioned media (CM) from OS-stressed cultures.

RESULTS

Both in MIO-M1 cells and in retinal explants, OS or exogenous VEGF induced a significant increase of VEGF mRNA, which was abolished by VEGF receptor 2 (VEGFR-2) inhibition. OS also caused VEGF release. In MIO-M1 cells, CM induced VEGF expression, which was abolished by a VEGFR-2 inhibitor. Moreover, the OS-induced increase of VEGF mRNA was abolished by a nuclear factor erythroid 2-related factor 2 (Nrf2) blocker, while the effect of exo-VEGF resulted Nrf2-independent. Finally, both the exo-VEGF- and the OS-induced increase of VEGF expression were blocked by a hypoxia-inducible factor-1 inhibitor.

CONCLUSIONS

These results are consistent with the existence of a retinal VEGF autocrine loop triggered by OS. This mechanism may significantly contribute to the maintenance of elevated VEGF levels and therefore it may be of central importance for the onset and development of DR.

Eyeing the Extracellular Matrix in Vascular Development and Microvascular Diseases and Bridging the Divide between Vascular Mechanics and Function

The extracellular matrix (ECM) is critical in all aspects of vascular development and health: supporting cell anchorage, providing structure, organization and mechanical stability, and serving as a sink for growth factors and sustained survival signals. Abnormal changes in ECM protein expression, organization, and/or properties, and the ensuing changes in vascular compliance affect vasodilator responses, microvascular pressure transmission, and collateral perfusion. The changes in microvascular compliance are independent factors initiating, driving, and/or exacerbating a plethora of microvascular diseases of the eye including diabetic retinopathy (DR) and vitreoretinopathy, retinopathy of prematurity (ROP), wet age-related macular degeneration (AMD), and neovascular glaucoma. Congruently, one of the major challenges with most vascular regenerative therapies utilizing localized growth factor, endothelial progenitor, or genetically engineered cell delivery, is the regeneration of blood vessels with physiological compliance properties. Interestingly, vascular cells sense physical forces, including the stiffness of their ECM, through mechanosensitive integrins, their associated proteins and the actomyosin cytoskeleton, which generates biochemical signals that culminate in a rapid expression of matricellular proteins such as cellular communication network 1 (CCN1) and CCN2 (aka connective tissue growth factor or CTGF). Loss or gain of function of these proteins alters genetic programs of cell growth, ECM biosynthesis, and intercellular signaling, that culminate in changes in cell behavior, polarization, and barrier function. In particular, the function of the matricellular protein CCN2/CTGF is critical during retinal vessel development and regeneration wherein new blood vessels form and invest a preformed avascular neural retina following putative gradients of matrix stiffness. These observations underscore the need for further in-depth characterization of the ECM-derived cues that dictate structural and functional properties of the microvasculature, along with the development of new therapeutic strategies addressing the ECM-dependent regulation of pathophysiological stiffening of blood vessels in ischemic retinopathies.

NADPH oxidases and HIF1 promote cardiac dysfunction and pulmonary hypertension in response to glucocorticoid excess

Cardiovascular side effects are frequent problems accompanying systemic glucocorticoid therapy, although the underlying mechanisms are not fully resolved. Reactive oxygen species (ROS) have been shown to promote various cardiovascular diseases although the link between glucocorticoid and ROS signaling has been controversial. As the family of NADPH oxidases has been identified as important source of ROS in the cardiovascular system we investigated the role of NADPH oxidases in response to the synthetic glucocorticoid dexamethasone in the cardiovascular system in vitro and in vivo in mice lacking functional NADPH oxidases due to a mutation in the gene coding for the essential NADPH oxidase subunit p22phox. We show that dexamethasone induced NADPH oxidase-dependent ROS generation, leading to vascular proliferation and angiogenesis due to activation of the transcription factor hypoxia-inducible factor-1 (HIF1). Chronic treatment of mice with low doses of dexamethasone resulted in the development of systemic hypertension, cardiac hypertrophy and left ventricular dysfunction, as well as in pulmonary hypertension and pulmonary vascular remodeling. In contrast, mice deficient in p22phox-dependent NADPH oxidases were protected against these cardiovascular side effects. Mechanistically, dexamethasone failed to upregulate HIF1α levels in these mice, while vascular HIF1α deficiency prevented pulmonary vascular remodeling. Thus, p22phox-dependent NADPH oxidases and activation of the HIF pathway are critical elements in dexamethasone-induced cardiovascular pathologies and might provide interesting targets to limit cardiovascular side effects in patients on chronic glucocorticoid therapy.

Adjuvant Therapies in Diabetic Retinopathy as an Early Approach to Delay Its Progression: The Importance of Oxidative Stress and Inflammation

Diabetes mellitus (DM) is a progressive disease induced by a sustained state of chronic hyperglycemia that can lead to several complications targeting highly metabolic cells. Diabetic retinopathy (DR) is a multifactorial microvascular complication of DM, with high prevalence, which can ultimately lead to visual impairment. The genesis of DR involves a complex variety of pathways such as oxidative stress, inflammation, apoptosis, neurodegeneration, angiogenesis, lipid peroxidation, and endoplasmic reticulum (ER) stress, each possessing potential therapeutic biomarkers. A specific treatment has yet to be developed for early stages of DR since no management is given other than glycemic control until the proliferative stage develops, offering a poor visual prognosis to the patient. In this narrative review article, we evaluate different dietary regimens, such as the Mediterranean diet, Dietary Pattern to Stop Hypertension (DASH) and their functional foods, and low-calorie diets (LCDs). Nutraceuticals have also been assessed in DR on account of their antioxidant, anti-inflammatory, and antiangiogenic properties, which may have an important impact on the physiopathology of DR. These nutraceuticals have shown to lower reactive oxygen species (ROS), important inflammatory factors, cytokines, and endothelial damage biomarkers either as monotherapies or combined therapies or concomitantly with established diabetes management or nonconventional adjuvant drugs like topical nonsteroidal anti-inflammatory drugs (NSAIDs).

Prospective exploratory study to assess the safety and efficacy of aflibercept in cystoid macular oedema associated with retinitis pigmentosa

Aims

To report the safety and efficacy of intravitreal aflibercept (Eylea) (ivA) for retinitis pigmentosa-associated cystoid macular oedema (RP-CMO) at 12 months via mean central macular thickness (CMT) and reported adverse events.

Methods

A prospective, exploratory, phase II, non-randomised, single-centre, open-label, 1-arm clinical trial involving 30 eyes of 30 patients. Serial ivA was given via loading dose (three injections) followed by treat and extend protocol over 12 months.

Results

Twenty-nine out of 30 (96.7%) patients completed 12 months of follow-up. A total of four to 11 injections per patient were given over the 12 month study. No statistically significant reduction of CMT or visual acuity (VA) improvement was demonstrated in the group overall. Eleven out of 29 (37.9%) participants were considered as ‘responders’, demonstrating at least an 11% reduction of CMT at 12 months on spectral domain optical coherence tomography compared with baseline. A reduction of CMT by mean (SD) 28.1% (12.9 %) was observed in responders at 12 months, however, no statistically significant corresponding improvement in best corrected VA was seen. Baseline characteristics were similar between responder and non-responder groups. No clinically significant adverse events were deemed secondary to ivA.

Conclusion

This first prospective exploratory study demonstrates both the safety and acceptability of serial ivA in patients with RP-CMO, effective at reducing CMT in 37.9% of patients. All patients demonstrating anatomical response did so after their first injection. Longer duration of CMO did not negatively affect response to anti-VEGF. Further study in a larger cohort of patients with shorter CMO duration would be valuable to better establish the utility of VEGF blockade in RP-CMO.

Trial registration numbers

EudraCT (2015-003723-65); ClinicalTrials.gov (NCT02661711).

MicroRNA-29b-3p Promotes Human Retinal Microvascular Endothelial Cell Apoptosis via Blocking SIRT1 in Diabetic Retinopathy

Background

Diabetic retinopathy (DR) is a main complication of diabetes mellitus (DM). Recent studies have implicated microRNAs in human retinal microvascular endothelial cell (HRMEC) dysfunction. In this study, we aim to investigate the apoptotic promotion of miR-29b-3p by blocking SIRT1 in HRMEC for DR situation.

Method

Blood samples were obtained from DR patients and controls. Dual-luciferase reporter assay using HEK-293T cells was performed to show the direct interaction of miR-29b-3p and the 3′UTR of SIRT1. HRMECs were exposed to 5.5 mmol/L of glucose (normal control), 5.5 mmol/L of glucose and 24.5 mmol/L of mannitol (osmotic pressure control), 30 mmol/L of glucose [hyperglycemia (HG)], 150 μmol/L of CoCl₂ (hypoxia), and 30 mmol/L of glucose plus 150 μmol/L of CoCl₂ (HG-CoCl₂). To identify the regulating relationship between miR-29b-3p and SIRT1, HRMECs were transfected with miR-29b-3p mimics/inhibitors or their negative controls. SRT1720 was used as a SIRT1 agonist. Cell viability was assessed with the cell counting kit-8 (CCK-8) assay, and apoptotic cells were stained by one-step terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay kit. Gene and protein expression were assayed by quantitative real-time reverse transcriptase-PCR (RT-qPCR) and western blotting separately.

Result

MiR-29b-3p was upregulated to 3.2-fold, and SIRT1 protein was downregulated to 65% in DR patients. Dual-luciferase reporter assay showed the direct interaction of miR-29b-3p and SIRT1. HRMECs were identified as >95% positive for CD31 and von Willebrand factor (vWF). MiR-29b-3p and Bax/Bcl-2 ratio was upregulated, whereas SIRT1 was downregulated in HRMECs in the HG-CoCl₂ condition. Decreased cell viability and upregulated apoptosis were also found in HRMECs of the HG-CoCl₂ condition. Upregulated miR-29b-3p decreased the expression of SIRT1 and increased the ratio of Bax/Bcl-2, whereas downregulated miR-29b-3p increased the expression of SIRT1 protein and downregulated the ratio of Bax/Bcl-2. SRT1720 rescued miR-29b-3p-induced HRMEC apoptosis via upregulating the expression of SIRT1 protein.

Conclusion

The dysregulation of miR-29b-3p/SIRT1 is a potential mechanism of HRMEC apoptosis in DR. MiR-29b-3p/SIRT1 may be a potential therapeutic target for DR.

VEGF-Trap is a potent modulator of vasoregenerative responses and protects dopaminergic amacrine network integrity in degenerative ischemic neovascular retinopathy

Retinal hypoxia triggers abnormal vessel growth and microvascular hyper-permeability in ischemic retinopathies. Whereas vascular endothelial growth factor A (VEGF-A) inhibitors significantly hinder disease progression, their benefits to retinal neurons remain poorly understood. Similar to humans, oxygen-induced retinopathy (OIR) mice exhibit severe retinal microvascular malformations and profound neuronal dysfunction. OIR mice are thus a phenocopy of human retinopathy of prematurity, and a proxy for investigating advanced stages of proliferative diabetic retinopathy. Hence, the OIR model offers an excellent platform for assessing morpho-functional responses of the ischemic retina to anti-angiogenic therapies. Using this model, we investigated the retinal responses to VEGF-Trap (Aflibercept), an anti-angiogenic agent recognizing ligands of VEGF receptors 1 and 2 that possesses regulatory approval for the treatment of neovascular age-related macular degeneration, macular edema secondary to retinal vein occlusion and diabetic macular edema. Our results indicate that Aflibercept not only reduces the severity of retinal microvascular aberrations but also significantly improves neuroretinal function. Aflibercept administration significantly enhanced light-responsiveness, as revealed by electroretinographic examinations, and led to increased numbers of dopaminergic amacrine cells. Additionally, retinal transcriptional profiling revealed the concerted regulation of both angiogenic and neuronal targets, including transcripts encoding subunits of transmitter receptors relevant to amacrine cell function. Thus, Aflibercept represents a promising therapeutic alternative for the treatment of further progressive ischemic retinal neurovasculopathies beyond the set of disease conditions for which it has regulatory approval. Cover Image for this issue: doi: 10.1111/jnc.14743.

Oxidative Stress as the Main Target in Diabetic Retinopathy Pathophysiology

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus (DM) causing vision impairment even at young ages. There are numerous mechanisms involved in its development such as inflammation and cellular degeneration leading to endothelial and neural damage. These mechanisms are interlinked thus worsening the diabetic retinopathy outcome. In this review, we propose oxidative stress as the focus point of this complication onset.

Fushiming Capsule Attenuates Diabetic Rat Retina Damage via Antioxidation and Anti-Inflammation

AIMS

Diabetic retinopathy (DR) remains one of the leading causes of acquired blindness. Fushiming capsule (FSM), a compound traditional Chinese medicine, is clinically used for DR treatment in China. The present study was to investigate the effect of FSM on retinal alterations, inflammatory response, and oxidative stress triggered by diabetes.

MAIN METHODS

Diabetic rat model was induced by 6-week high-fat and high-sugar diet combined with 35 mg/kg streptozotocin (STZ). 30 days after successful establishment of diabetic rat model, full field electroretinography (ffERG) and optical coherence tomography (OCT) were performed to detect retinal pathological alterations. Then, FSM was administered to diabetic rats at different dosages for 42-day treatment and diabetic rats treated with Calcium dobesilate (CaD) capsule served as the positive group. Retinal function and structure were observed, and retinal vascular endothelial growth factor-α (VEGF-α), glial fibrillary acidic (GFAP), and vascular cell adhesion protein-1 (VCAM-1) expressions were measured both on mRNA and protein levels, and a series of blood metabolic indicators were also assessed.

KEY FINDINGS

In DR rats, FSM (1.0 g/kg and 0.5 g/kg) treatment significantly restored retinal function (a higher amplitude of b-wave in dark-adaptation 3.0 and OPs2 wave) and prevented the decrease of retinal thickness including inner nuclear layer (INL), outer nuclear layer (ONL), and entire retina. Additionally, FSM dramatically decreased VEGF-α, GFAP, and VCAM-1 expressions in retinal tissues. Moreover, FSM notably improved serum antioxidative enzymes glutathione peroxidase, superoxide dismutase, and catalase activities, whereas it reduced serum advanced glycation end products, methane dicarboxylic aldehyde, nitric oxide, and total cholesterol and triglycerides levels.

SIGNIFICANCE

FSM could ameliorate diabetic rat retina damage possibly via inhibiting inflammation and improving antioxidation.

The role of inflammation in diabetic eye disease

Mounting evidence suggests that immunological mechanisms play a fundamental role in the pathogenesis of diabetic retinopathy (DR) and diabetic macular edema (DME). Upregulation of cytokines and other proinflammatory mediators leading to persistent low-grade inflammation is believed to actively contribute to the DR-associated damage to the retinal vasculature, inducing breakdown of the blood-retinal barrier, subsequent macular edema formation, and promotion of retinal neovascularization. This review summarizes the current knowledge of the biological processes providing an inflammatory basis for DR and DME. In addition, emerging therapeutic approaches targeting inflammation are discussed, including blockade of angiopoietin 2 and other molecular targets such as interleukin (IL)-6, IL-1β, plasma kallikrein, and integrins.

Intravitreal ranibizumab injection at the end of vitrectomy for diabetic vitreous hemorrhage (Observational Study)

To evaluate the outcomes and complications of intravitreal injections of ranibizumab in patients during pars plana vitrectomy for treatment of diabetic vitreous hemorrhage. This retrospective, observational, comparative study included 103 patients (103 eyes) who underwent pars plana vitrectomy for treatment of diabetic vitreous hemorrhage. Sixty-six patients received an intravitreal injection of 0.05 mg (0.05 cc) of ranibizumab at the end of surgery. Main outcome measures were the occurrence of recurrent early vitreous hemorrhage, reoperation, intraocular pressure, best corrected visual acuity. Mean follow-up time was 6 months. The rate of rebleeding in the intravitreal ranibizumab (IVR) group was 6.1% (4 eyes), which is significantly lower than the control group (24.3%, 9 eyes, P < .01). The incidence of postoperative diabetic vitreous hemorrhage (PDVH) was significantly lower in the IVR group than the control group, OR=0.26, 95% CI= (0.06, 0.95). Visual acuity 6 months after operation was better in IVR group (P<.01) There was no difference in mean intraocular pressure between the 2 groups (P=.56). The present clinical study suggests that intravitreal injection of ranibizumab is effective in the prevention of postoperative diabetic vitreous hemorrhage in eyes undergoing pars plana vitrectomy for the treatment of diabetic vitreous hemorrhage.

Angiopoietins in Diabetic Retinopathy: Current Understanding and Therapeutic Potential

Diabetic retinopathy (DR) is the commonest cause of blindness in the working-age population of the developed world. The molecular pathophysiology of DR is complex, and a complete spatiotemporal model of the disease is still being elucidated. Recently, a role for angiopoietin (Ang) proteins in the pathophysiology of DR has been proposed by several research groups, and several aspects of Ang signalling are being explored as novel therapeutic strategies. Here, we review the role of the Ang proteins in two important forms of DR, diabetic macular oedema and proliferative diabetic retinopathy. The function of the Ang proteins in regulating blood vessel permeability and neovascularisation is discussed, and we also evaluate recent preclinical and clinical studies highlighting the potential benefits of modulating Ang signalling as a treatment for DR.