Hepatocyte growth factor in vitreous and serum from patients with proliferative diabetic retinopathy

Management after cataract surgery for patients with diabetic retinopathy: a systematic review and meta-analysis

PURPOSE

To evaluate the safety and effectiveness of various treatment modalities in patients with diabetic retinopathy (DR) who underwent cataract surgery.

METHODS

A comprehensive search for randomized controlled trials (RCTs) was conducted using the PubMed, Embase, Cochrane Library, and CNKI databases up to December 22, 2021. The safety and efficacy of treatment modalities were assessed using the risk ratio (RR) to compare the progression of DR and the mean difference to evaluate the best corrected visual acuity (BCVA) and macular thickness (MT).

RESULTS

The meta-analysis of the RCTs revealed that anti-VEGF (anti-vascular endothelial growth factor) drugs significantly reduced the progression of DR [RR: 0.37 (95%CI 0.19, 0.70), P = 0.002] and improved BCVA [mean difference = - 0.06 (- 0.12, - 0.01), P = 0.03] in patients with pre-existing DR who underwent cataract surgery. Steroid drugs also showed a significant reduction in macular thickness [mean difference = - 55.63 (- 90.73, - 20.53), I2 = 56%, P = 0.002] in DR patients two weeks after cataract surgery compared to the control group. The safety profiles of different management options did not differ significantly.

CONCLUSION

The present meta-analysis suggests that anti-VEGF drugs can effectively slow down the progression of diabetic retinopathy, improve BCVA, and reduce MT in DR patients who underwent cataract surgery. Steroid drugs also show promise in reducing MT. However, further studies with larger sample sizes are required to compare the efficacy and safety of different management options in a multi-center clinical setting.

MicroRNA-21: A critical underestimated molecule in diabetic retinopathy

Diabetes mellitus (DM) has grown in attention in recent years as a result of its debilitating complications and chronic disabilities. Diabetic retinopathy (DR) is a chronic microvascular complication of DM and is considered as the primary reason for blindness in adults. Early diagnosis of diabetes complications along with targeted therapy options are critical in avoiding morbidity and mortality associated with complications of diabetes. miR-21 is an important and widely studied non-coding-RNA (ncRNA) with considerable roles in various pathologic conditions including diabetic complications. miR-21 is one of the most elevated miRNAs in response to hyperglycemia and its role in angiogenesis is a major culprit of a wide range of disorders including DR. The main role of miR-21 in DR pathophysiology is believed to be through regulating angiogenesis in retina. This article aims to outline miR-21 biogenesis and distribution in human body along with discussions about its role in DR pathogenesis and its biomarker value in order to facilitate understanding of the new characteristics of miR-21 in DR management.

Diabetic Retinopathy: Soluble and Imaging Ocular Biomarkers

Diabetic retinopathy (DR), the most common microvascular complication of diabetes mellitus, represents the leading cause of acquired blindness in the working-age population. Due to the potential absence of symptoms in the early stages of the disease, the identification of clinical biomarkers can have a crucial role in the early diagnosis of DR as well as for the detection of prognostic factors. In particular, imaging techniques are fundamental tools for screening, diagnosis, classification, monitoring, treatment planning and prognostic assessment in DR. In this context, the identification of ocular and systemic biomarkers is crucial to facilitate the risk stratification of diabetic patients; moreover, reliable biomarkers could provide prognostic information on disease progression as well as assist in predicting a patient's response to therapy. In this context, this review aimed to provide an updated and comprehensive overview of the soluble and anatomical biomarkers associated with DR.

Gene therapy for diabetic peripheral neuropathy: A randomized, placebo-controlled phase III study of VM202, a plasmid DNA encoding human hepatocyte growth factor

VM202 is a plasmid DNA encoding two isoforms of hepatocyte growth factor (HGF). A previous phase II study in subjects with painful diabetic peripheral neuropathy (DPN) showed significant reductions in pain. A phase III study was conducted to evaluate the safety and efficacy of VM202 in DPN. The trial was conducted in two parts, one for 9 months (DPN 3-1) with 500 subjects (VM202: 336 subjects; and placebo: 164) and a preplanned subset of 101 subjects (VM202: 65 subjects; and placebo: 36) with a noninterventional extension to 12 months (DPN 3-1b). VM202 or placebo was administered to calf muscles on days 0 and 14, and on days 90 and 104. The primary end point in DPN 3-1 was change from baseline in the mean 24-h Numerical Rating Scale (NRS) pain score. In DPN 3-1b, the primary end point was safety, whereas the secondary efficacy end point was change in the mean pain score. VM202 was well-tolerated in both studies without significant adverse events. VM202 failed to meet its efficacy end points in DPN 3-1. In DPN 3-1b, however, VM202 showed significant and clinically meaningful pain reduction versus placebo. Pain reduction in DPN 3-1b was even greater in subjects not receiving gabapentin or pregabalin, confirming an observation noted in the phase II study. In DPN 3-1b, symptomatic relief was maintained for 8 months after the last injection suggesting that VM202 treatment might change disease progression. Despite the perplexing discrepancy between the two studies, the safety and long-lasting pain-relieving effects of VM202 observed in DPN 3-1b warrant another rigorous phase III study. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Current therapies for painful diabetic peripheral neuropathy (DPN) are palliative and do not target the underlying mechanisms. Moreover, symptomatic relief is often limited with existing neuropathic pain drugs. Thus, there is a great medical need for safer and effective treatments for DPN. WHAT QUESTION DID THIS STUDY ADDRESS? Can nonviral gene delivery of hepatocyte growth factor reduce pain in patients with DPN and potentially modify progression of the disorder? WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? Nonviral gene therapy can be used safely and practically to treat DPN. HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? As the first gene medicine to enter advanced clinical trials for the treatment of DPN, this study provides the proof of concept of an entirely new potential approach to the disorder.

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.

Hepatocyte growth factor is upregulated in ischemic retina and contributes to retinal vascular leakage and neovascularization

In patients with macular edema due to ischemic retinopathy, aqueous levels of hepatocyte growth factor (HGF) correlate with edema severity. We tested whether HGF expression and activity in mice with oxygen-induced ischemic retinopathy supports a role in macular edema. In ischemic retina, HGF was increased in endogenous cells and macrophages associated with retinal neovascularization (NV). HGF activator was increased in and around retinal vessels potentially providing vascular targeting. One day after intravitreous injection of HGF, VE-cadherin was reduced and albumin levels in retina and vitreous were significantly increased indicating vascular leakage. Injection of VEGF caused higher levels of vitreous albumin than HGF, and co-injection of both growth factors caused significantly higher levels than either alone. HGF increased the number of macrophages on the retinal surface, which was blocked by anti-c-Met and abrogated in chemokine (C-C motif) ligand 2 (CCL2)-/- mice. Injection of anti-c-Met significantly decreased leakage within 24 hours and after 5 days it reduced retinal NV in mice with ischemic retinopathy, but had no effect on choroidal NV. These data indicate that HGF is a pro-permeability, pro-inflammatory, and pro-angiogenic factor and along with its activator is increased in ischemic retina providing support for a potential role of HGF in macular edema in ischemic retinopathies.

Human vitreous in proliferative diabetic retinopathy: Characterization and translational implications

Diabetic retinopathy (DR) is one of the leading causes of visual impairment in the working-age population. DR is a progressive eye disease caused by long-term accumulation of hyperglycaemia-mediated pathological alterations in the retina of diabetic patients. DR begins with asymptomatic retinal abnormalities and may progress to advanced-stage proliferative diabetic retinopathy (PDR), characterized by neovascularization or preretinal/vitreous haemorrhages. The vitreous, a transparent gel that fills the posterior cavity of the eye, plays a vital role in maintaining ocular function. Structural and molecular alterations of the vitreous, observed during DR progression, are consequences of metabolic and functional modifications of the retinal tissue. Thus, vitreal alterations reflect the pathological events occurring at the vitreoretinal interface. These events are caused by hypoxic, oxidative, inflammatory, neurodegenerative, and leukostatic conditions that occur during diabetes. Conversely, PDR vitreous can exert pathological effects on the diabetic retina, resulting in activation of a vicious cycle that contributes to disease progression. In this review, we recapitulate the major pathological features of DR/PDR, and focus on the structural and molecular changes that characterize the vitreal structure and composition during DR and progression to PDR. In PDR, vitreous represents a reservoir of pathological signalling molecules. Therefore, in this review we discuss how studying the biological activity of the vitreous in different in vitro, ex vivo, and in vivo experimental models can provide insights into the pathogenesis of PDR. In addition, the vitreous from PDR patients can represent a novel tool to obtain preclinical experimental evidences for the development and characterization of new therapeutic drug candidates for PDR therapy.

CAMKII as a therapeutic target for growth factor-induced retinal and choroidal neovascularization

While anti-VEGF drugs are commonly used to inhibit pathological retinal and choroidal neovascularization, not all patients respond in an optimal manner. Mechanisms underpinning resistance to anti‑VEGF therapy include the upregulation of other proangiogenic factors. Therefore, therapeutic strategies that simultaneously target multiple growth factor signaling pathways would have significant value. Here, we show that Ca2+/calmodulin-dependent kinase II (CAMKII) mediates the angiogenic actions of a range of growth factors in human retinal endothelial cells and that this kinase acts as a key nodal point for the activation of several signal transduction cascades that are known to play a critical role in growth factor-induced angiogenesis. We also demonstrate that endothelial CAMKIIγ and -δ isoforms differentially regulate the angiogenic effects of different growth factors and that genetic deletion of these isoforms suppresses pathological retinal and choroidal neovascularization in vivo. Our studies suggest that CAMKII could provide a novel and efficacious target to inhibit multiple angiogenic signaling pathways for the treatment of vasoproliferative diseases of the eye. CAMKIIγ represents a particularly promising target, as deletion of this isoform inhibited pathological neovascularization, while enhancing reparative angiogenesis in the ischemic retina.

Assessment of biomarkers using multiplex assays in aqueous humor of patients with diabetic retinopathy

Background

With the high prevalence of type 2 diabetes, diabetic retinopathy (DR) has become a leading health problem worldwide. The pathogenesis of DR is complex and several vascular, inflammatory, and neuronal mechanisms are involved. The purpose of this study was to assess the levels of immune and inflammatory biomarkers in the aqueous humor of patients with different severities of DR and to analyze the correlations between Interleukin-6 (IL-6) and these biomarkers, and between IL-6 and the severity of the disease.

Methods

Aqueous humor samples were obtained from 51 non-diabetic patients and 151 diabetic patients. Levels of 45 different cytokines, chemokines, and growth factors were measured using a multiplex bead immunoassay.

Results

IL-6, IL-8, Inducible Protein-10 (IP-10), leukemia inhibitory factor (LIF), hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF)-A were significantly higher (p < 0.05) in the aqueous humor of the DR patients compared to the non-diabetic patients, while the concentrations of IL-1α, IL-4, IL-9, IL-21, IL-23, IL-27, IL-31, RANTES, interferon-α, growth regulated oncogene (GRO), and tumor necrosis factor (TNF)-α were significantly lower (p < 0.05) in the DR patients. The IL-6 levels increased as the severity of DR increased. In addition, the IL-6 level positively correlated with the IL-8, HGF and LIF levels, while negatively with the IL-31and GRO levels.

Conclusions

These findings suggest that inflammation and immune response may contribute to the pathogenesis of DR, and these biomarkers may potentially be new therapeutic targets for DR.

Topical Squalamine 0.2% and Intravitreal Ranibizumab 0.5 mg as Combination Therapy for Macular Edema Due to Branch and Central Retinal Vein Occlusion: An Open-Label, Randomized Study

BACKGROUND AND OBJECTIVE

To evaluate the effects of squalamine (OHR-102; Ohr Pharmaceuticals, New York, NY) and ranibizumab (Lucentis; Genentech, South San Francisco, CA) on macular edema (ME) secondary to retinal vein occlusion (RVO).

PATIENTS AND METHODS

Twenty consecutive, treatment-naïve patients with RVO-related ME received topical squalamine and intravitreal ranibizumab 0.5 mg for 10 weeks, followed by randomization to continue or discontinue squalamine. Groups received as-needed ranibizumab from weeks 2 through 34. The primary endpoint was the proportion of eyes gaining 15 or more Early Treatment Diabetic Retinopathy Study (ETDRS) letters at week 38. Safety and tolerability were assessed. Data from 13 treatment-naïve control eyes previously enrolled in three similar trials evaluating monthly ranibizumab 0.5 mg for RVO-related ME were included for comparison.

RESULTS

At baseline, mean best-corrected visual acuity (BCVA) measures were 55.6 ETDRS letters and 55.0 ETDRS letters in the squalamine and control groups, respectively. At week 38, BCVA improved 25.6 letters in the squalamine group; at month 9, BCVA improved 16.3 letters in the control group. This corresponds to a between-treatment-group difference of 9.2 letters. Squalamine and ranibizumab combination therapy was well-tolerated.

CONCLUSIONS

In patients with RVO-related ME, topical squalamine combined with early, as-needed ranibizumab appears to enhance visual recovery versus ranibizumab alone. Combination therapy appears safe and was well-tolerated. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:914-923.].

Regulatory SNPs Alter the Gene Expression of Diabetic Retinopathy Associated Secretary Factors

OBJECTIVES

Diabetic retinopathy (DR) is a common microvascular complication in both type I and type II diabetes. Several previous reports indicated the serum centration of some secretary factors were highly associated with DR. Therefore, we hypothesis regulatory SNPs (rSNPs) genotype in secretary factors may alter these gene expression and lead to DR.

METHODS

At first, pyrosequencing were applying to screen the SNPs which present allele frequency different in DR and DNR. Then individual genotyping was processed by Taqman assays in Taiwanese DR and DNR patients. To evaluate the effect of SNP allele on transcriptional activity, we measured promoter activity using luciferase reporter constructs.

RESULTS

We found the frequencies of the CC, CG, and GG genotype of the rs2010963 polymorphism were 15.09%, 47.14%, and 37.74% in DR and 12.90%, 19.35%, and 67.74% in DNR, respectively (p = 0.0205). The prevalence of DR was higher (p = 0.00793) in patients with the CC or CG genotype (62.26% and 32.26% for DR and DNR, respectively) compared with the patients with the GG genotype. To evaluate the effect of rs2010963-C allele on transcriptional activity, we measured promoter activity using luciferase reporter constructs. The rs2010963-C reporter showed 1.6 to 2-fold higher luciferase activity than rs2010963-G in 3 cell lines.

CONCLUSION

Our data proposed rs2010963-C altered the expression level of VEGFA in different tissues. We suggested small increase but long term exposure to VEGFA may lead to DR finally.

Effect of shRNA-mediated knockdown of vascular endothelial growth factor on the proliferation of choroid-retinal endothelial cells under hypoxic conditions

The aim of the present study was to investigate the role of vascular endothelial growth factor (VEGF) in cell proliferation under hypoxic conditions. Gene knockdown of VEGF was conducted in the choroid-retinal endothelial RF/6A cell line by transfection with short hairpin RNA (shRNA), in which a shRNA fragment against VEGF was synthesized and cloned into the vector, pSilencer 2.1-U6 neo. Subsequently, a model of hypoxia was established in the RF/6A cell line via treatment with CoCl₂, into which the recombinant plasmids, containing the VEGF-targeting shRNA (p-shRNA), were transfected. The study included four treatment groups, namely a control group (normal group), a hypoxia group treated with CoCl₂ (CoCl₂ group), a control plasmid group that were subjected to CoCl₂ treatment and transfection with a pSilencer 2.1-U6 neo plasmid without the shRNA (CoCl₂ + p-NC group), and a group treated with CoCl₂ and transfected with a pSilencer 2.1-U6 neo plasmid containing the VEGF-targeting shRNA (CoCl₂ + p-shRNA group). Subsequent to treatment, the mRNA and protein expression levels of VEGF were evaluated using quantitative polymerase chain reaction and western blot analysis, respectively, In addition, cell proliferation was assessed. RF/6A cells treated with CoCl₂ reduced cell connectivity, irregular morphology and reduced thickness compared with the cells in the normal group. However, cells in the CoCl₂ + p-shRNA group exhibited an improved morphology compared with the CoCl₂ and CoCl₂ + p-NC groups. Cell proliferation in the CoCl₂ group was enhanced in a time-dependent manner. However, the hypoxia-induced increase in cell proliferation was significantly inhibited in the CoCl₂ + p-shRNA group, with inhibition rates of 16, 32 and 38% at 24, 48 and 72 h, respectively. The mRNA and protein expression levels of VEGF were increased in the CoCl₂ group when compared with the normal group, and these hypoxia-induced increases in VEGF expression were reduced in the CoCl₂ + p-shRNA group. Therefore, the results indicated that the targeted knockdown of VEGF in vascular endothelial cells may be effective for the treatment of retinal neovascularization diseases.

Increased expression of angiogenic and inflammatory proteins in the vitreous of patients with ischemic central retinal vein occlusion

Background

Central retinal vein occlusion (CRVO) is a common disease characterized by a disrupted retinal blood supply and a high risk of subsequent vision loss due to retinal edema and neovascular disease. This study was designed to assess the concentrations of selected signaling proteins in the vitreous and blood of patients with ischemic CRVO.

Methods

Vitreous and blood samples were collected from patients undergoing surgery for ischemic CRVO (radial optic neurotomy (RON), n = 13), epiretinal gliosis or macular hole (control group, n = 13). Concentrations of 40 different proteins were determined by an ELISA-type antibody microarray.

Results

Expression of proteins enriched in the vitreous (CCL2, IGFBP2, MMP10, HGF, TNFRSF11B (OPG)) was localized by immunohistochemistry in eyes of patients with severe ischemic CRVO followed by secondary glaucoma. Vitreal expression levels were higher in CRVO patients than in the control group (CRVO / control; p < 0.05) for ADIPOQ (13.6), ANGPT2 (20.5), CCL2 (MCP1) (3.2), HGF (4.7), IFNG (13.9), IGFBP1 (14.7), IGFBP2 (1.8), IGFBP3 (4.1), IGFBP4 (1.7), IL6 (10.8), LEP (3.4), MMP3 (4.3), MMP9 (3.6), MMP10 (5.4), PPBP (CXCL7 or NAP2) (11.8), TIMP4 (3.8), and VEGFA (85.3). In CRVO patients, vitreal levels of CCL2 (4.2), HGF (23.3), IGFBP2 (1.23), MMP10 (2.47), TNFRSF11B (2.96), and VEGFA (29.2) were higher than the blood levels (vitreous / blood, p < 0.05). Expression of CCL2, IGFBP2, MMP10, HGF, and TNFRSF11B was preferentially localized to the retina and the retinal pigment epithelium (RPE).

Conclusion

Proteins related to hypoxia, angiogenesis, and inflammation were significantly elevated in the vitreous of CRVO patients. Moreover, some markers known to indicate atherosclerosis may be related to a basic vascular disease underlying RVO. This would imply that local therapeutic targeting might not be sufficient for a long term therapy in a systemic disease but hypothetically reduce local changes as an initial therapeutic approach.

Modulation of CD44 Activity by A6-Peptide

Hyaluronan (HA) is a non-sulfated glycosaminoglycan distributed throughout the extracellular matrix that plays a major role in cell adhesion, migration, and proliferation. CD44, a multifunctional cell surface glycoprotein, is a receptor for HA. In addition, CD44 is known to interact with other receptors and ligands, and to mediate a number of cellular functions as well as disease progression. Studies have shown that binding of HA to CD44 in cancer cells activates survival pathways resulting in cancer cell survival. This effect can be blocked by anti-CD44 monoclonal antibodies. A6 is a capped, eight l-amino acid peptide (Ac-KPSSPPEE-NH2) derived from the biologically active connecting peptide domain of the serine protease, human urokinase plasminogen activator (uPA). A6 neither binds to the uPA receptor (uPAR) nor interferes with uPA/uPAR binding. A6 binds to CD44 resulting in the inhibition of migration, invasion, and metastasis of tumor cells, and the modulation of CD44-mediated cell signaling. A6 has been shown to have no dose-limiting toxicity in animal studies. A6 has demonstrated efficacy and an excellent safety profile in Phase 1a, 1b, and 2 clinical trials. In animal models, A6 has also exhibited promising results for the treatment of diabetic retinopathy and wet age-related macular degeneration through the reduction of retinal vascular permeability and inhibition of choroidal neovascularization, respectively. Recently, A6 has been shown to be directly cytotoxic for B-lymphocytes obtained from patients with chronic lymphocytic leukemia expressing the kinase, ZAP-70. This review will discuss the activity of A6, A6 modulation of HA and CD44, and a novel strategy for therapeutic intervention in disease.

Diabetic Retinopathy: Vascular and Inflammatory Disease

Diabetic retinopathy (DR) is the leading cause of visual impairment in the working-age population of the Western world. The pathogenesis of DR is complex and several vascular, inflammatory, and neuronal mechanisms are involved. Inflammation mediates structural and molecular alterations associated with DR. However, the molecular mechanisms underlying the inflammatory pathways associated with DR are not completely characterized. Previous studies indicate that tissue hypoxia and dysregulation of immune responses associated with diabetes mellitus can induce increased expression of numerous vitreous mediators responsible for DR development. Thus, analysis of vitreous humor obtained from diabetic patients has made it possible to identify some of the mediators (cytokines, chemokines, and other factors) responsible for DR pathogenesis. Further studies are needed to better understand the relationship between inflammation and DR. Herein the main vitreous-related factors triggering the occurrence of retinal complication in diabetes are highlighted.

Gene expression of IGF1, IGF1R, and IGFBP3 in epiretinal membranes of patients with proliferative diabetic retinopathy: preliminary study

The molecular mechanism formation of secondary epiretinal membranes (ERMs) after proliferative diabetic retinopathy (PDR) or primary idiopathic ERMs is still poorly understood. Therefore, the present study focused on the assessment of IGF1, IGF1R, and IGFBP3 mRNA levels in ERMs and PBMCs from patients with PDR. The examined group comprised 6 patients with secondary ERMs after PDR and the control group consisted of 11 patients with idiopathic ERMs. Quantification of IGF1, IGF1R, and IGFBP3 mRNAs was performed by real-time QRT-PCR technique. In ERMs, IGF1 and IGF1R mRNA levels were significantly higher in patients with diabetes compared to control subjects. In PBMCs, there were no statistically significant differences of IGF1, IGF1R, and IGFBP3 expression between diabetic and nondiabetic patients. In conclusion, our study indicated IGF1 and IGF1R differential expression in ERMs, but not in PBMCs, of diabetic and nondiabetic patients, suggesting that these factors can be involved in the pathogenesis or progression of proliferative vitreoretinal disorders. This trial is registered with NCT00841334.

Phase 1/2 open-label dose-escalation study of plasmid DNA expressing two isoforms of hepatocyte growth factor in patients with painful diabetic peripheral neuropathy

This study aimed to evaluate the safety and preliminary efficacy of intramuscular injections of plasmid DNA (VM202) expressing two isoforms of hepatocyte growth factor (HGF) in subjects with painful diabetic peripheral neuropathy (PDPN). Twelve patients in three cohorts (4, 8, and 16 mg) received two sets of VM202 injections separated by two weeks. Safety and tolerability were evaluated and the visual analog scale (VAS), the short form McGill questionnaire (SF-MPQ), and the brief pain inventory for patients with diabetic peripheral neuropathy (BPI-DPN) measured pain level throughout 12 months after treatment. No serious adverse events (AEs) were observed. The mean VAS was reduced from baseline by 47.2% (P = 0.002) at 6 months and by 44.1% (P = 0.005) at 12 months after treatment. The VAS scores for the 4, 8, and 16 mg dose cohorts at 6 months follow-up decreased in a dose-responsive manner, by 21% (P = 0.971), 53% (P = 0.014), and 62% (P = 0.001), respectively. The results with the BPI-DPN and SF-MPQ showed patterns similar to the VAS scores. In conclusion, VM202 treatment appeared to be safe, well tolerated, and sufficient to provide long term symptomatic relief and improvement in the quality of life in patients with PDPN.

Novel targets against retinal angiogenesis in diabetic retinopathy

Proliferative diabetic retinopathy (PDR), characterized by pathologic retinal angiogenesis, is a major cause of blindness in the USA and globally. Treatments targeting vascular endothelial growth factor (VEGF) have emerged as a beneficial part of the therapeutic armamentarium for this condition, highlighting the utility of identifying and targeting specific pathogenic molecules. There continues to be active research into the molecular players regulating retinal angiogenesis, including pro-angiogenic factors, anti-angiogenic factors, and integrins and matrix proteinases. New insights have been especially prominent regarding molecules which regulate specialized endothelial cells called tip cells, which play a lead role in endothelial sprouting. Together, these research efforts are uncovering new, important molecular regulators of retinal angiogenesis, which provide fertile areas for therapeutic exploration. This review discusses potential molecular targets, with an emphasis towards newer targets.

Prevention of vision loss after cataract surgery in diabetic macular edema with intravitreal bevacizumab: a pilot study

PURPOSE

To determine whether an intravitreal bevacizumab injection after phacoemulsification can improve cataract surgery visual outcomes in patients with diabetic macular edema by acting on the degree of edema.

SETTING

Fundación Oftalmológica del Mediterráneo, Valencia, Spain.

METHODS

We selected 26 consecutive diabetic patients with nonproliferative diabetic retinopathy and macular edema who were to undergo cataract surgery, and we divided them into two randomized groups to be studied prospectively. Group I included 13 eyes that were injected with intravitreal bevacizumab upon completion of cataract surgery; Group II included 13 control eyes that were injected with balanced salt solution.

RESULTS

Preoperative macular thickness was 282.62 microm +/- 57.64 in Group I and 310.38 microm +/- 82.99 in Group II. Preoperative Snellen best-corrected visual acuity was 0.27 +/- 0.17 and 0.24 +/- 0.16 in Groups I and II, respectively. Best-corrected visual acuity at 3 and 6 months was better in Group I--0.4 +/- 0.28 and 0.4 +/- 0.27--whereas poorer results were observed in the control group--0.21 +/- 0.13 and 0.14 +/- 0.13. These mean macular thickness values differed significantly between groups at 3 months (P = 0.040) and 6 months (P = 0.004). Optical coherence tomography measured macular thickness was also better in Group I, 292.46 +/- 104.75 microm at 3 months and 277.62 +/- 92.99 microm at 6 months. For Group II, the results were 367.62 +/- 75.24 microm at 3 months and 387.46 +/- 74.11 microm at 6 months. These mean macular thickness values differed significantly between groups at 3 months (P = 0.046) and 6 months (P = 0.002).

CONCLUSION

Intravitreal bevacizumab immediately after phacoemulsification prevents exacerbation of the macular edema seen in many diabetic patients undergoing cataract surgery. In addition, this effect seems to hold in the short term.

Bioinformatics analysis of diabetic retinopathy using functional protein sequences

Diabetic retinopathy is the leading cause of blindness among patients with diabetes mellitus. We evaluated the role of several proteins that are likely to be involved in diabetic retinopathy by employing multiple sequence alignment using ClustalW tool and constructed a phylogram tree using functional protein sequences extracted from NCBI. Phylogram was constructed using Neighbor-Joining Algorithm in bioinformatics approach. It was observed that aldose reductase and nitric oxide synthase are closely associated with diabetic retinopathy. It is likely that vascular endothelial growth factor, pro-inflammatory cytokines, advanced glycation end products, and adhesion molecules that also play a role in diabetic retinopathy may do so by modulating the activities of aldose reductase and nitric oxide synthase. These results imply that methods designed to normalize aldose reductase and nitric oxide synthase activities could be of significant benefit in the prevention and treatment of diabetic retinopathy.

Pathogenesis and classification of proliferative diabetic vitreoretinopathy

PURPOSE

To review the current knowledge regarding the pathogenesis of proliferative diabetic vitreoretinopathy (PDVR) and to present recommendations for its clinical staging.

DESIGN

Focused literature review and authors' clinical experience.

RESULTS

Although several biochemical mediators may be responsible for the pathogenesis of PDVR, no common biochemical pathway exists. Of those mediators, vascular endothelial growth factor is the one most studied so far. However, since in proliferative diabetic retinopathy (PDR) the thickened posterior vitreous cortex is one of the main factors in the development of proliferations, a consequent shrinkage of the posterior vitreous cortex leads to hemorrhages and tractive retinal detachments. Therefore, PDR should be called PDVR. In consequence, the authors present a new morphological classification of PDVR.

CONCLUSIONS

There is no consensus about the biochemical pathway responsible for the progression of PDVR. Although several classifications are described in the literature, the classification suggested here is important in the judgment of, the communication about and the therapy of diabetic retinopathy. Furthermore, it is the only reliable classification for predicting the surgical outcome in diabetics.

A chronic grey matter penumbra, lateral microvascular intussusception and venous peduncular avulsion underlie diabetic vitreous haemorrhage

The landmark publications that gave such impetus to our understanding of proliferative diabetic retinopathy are reviewed in the light of more recent reports. Briefly, confluence of small areas of capillary closure in the midperipheral and peripheral retina results in arteriovenous shunting and abnormal oxygen partial pressure gradients. These gradients embrace a chronic ischaemic penumbra that stimulates neuroglial secretion of angiogenic growth factors and upregulation of their receptors in the retinal venous endothelium and adventitia. The blood shunting produces biomechanical stresses within the veins and induces microvascular intussusception near arteriovenous crossings, giving way to neovascular outgrowths and/or segmental venous lesions (such as omega loops and coils) that penetrate the inner limiting lamina. The lamellar collagenous matrix of the vitreous cortex is then exploited for integrin-dependent rete expansion along chemotactic gradients. During posterior vitreous detachment, haemorrhaging takes place from the arterialised veins as venous neovascular peduncles are avulsed.

Vitreous fluid biomarkers

Interactions between cells and the network of secreted proteins are associated with the ocular disease. In most cases, clinical appearcance is sufficiently diagnostic. However, in cases of nonspecific or atypical clinical presentation, diagnostic sampling of vitreous fluid can aid diagnosis and treatment for ocular disease. Progresses in the basic sciences, particularly molecular biology, and advances in surgical instrumentation have greatly enhanced the diagnostic armamentarium. These developments also have led to a better understanding of the pathophysiological processes involved in ocular diseases and have prompted evolution of new therapeutic modalities. In this chapter, we review techniques for vitreous fluid sampling and biomarker quantitation thereof. The molecular biology of bioactive vitreous fluid factors is also discussed with respect to their clinical involvement in the development of ocular disease.

Diabetic cataract removal: postoperative progression of maculopathy--growth factor and clinical analysis

BACKGROUND

Diabetic cataract extraction can be frequently complicated by macular oedema, progression of retinopathy, or development of iris neovascularisation. The pathogenesis of these complications may be the result of changes in the concentration of angiogenic and anti-angiogenic cytokines in the immediate postoperative period. The study aims to prospectively analyse this.

METHODS

Uneventful phacoemulsification with intraocular lens implant was performed in seven eyes of six patients with diabetic retinopathy ranging from severe non-proliferative to quiescent proliferative. Patients were reviewed 1 day, 1 week, 1 month, and 3 months after surgery with fundus fluorescein angiography (FFA) and aqueous sampling. Each sample was analysed for VEGF, HGF, Il-1 beta (pg/ml), and PEDF (microg/ml) by sandwich ELISA.

RESULTS

Clinically significant macular oedema (CSMO) occurred in one patient although increased macular hyperfluorescence occurred in three patients on FFA at 1 month. VEGF 165 concentration increased 1 day after surgery from a median baseline of 68 pg/ml (range 22-87 pg/ml) to 723 pg/ml (range 336-2071) at day 1. By 1 month it had decreased to 179 (range 66-811 pg/ml). HGF concentrations steadily increased over the month while IL-1 beta and PEDF concentrations demonstrated an acute rise on day 1 after surgery and then IL-1beta returned to baseline concentrations while PEDF decreased to below baseline.

CONCLUSION

These results confirm altered concentrations of angiogenic and antiangiogenic growth factors after cataract surgery, which may induce subclinical and clinical worsening of diabetic maculopathy.

The role of cytokines and trophic factors in epiretinal membranes: Involvement of signal transduction in glial cells

Idiopathic epiretinal membranes (ERMs) in the macular region can cause a reduction in vision and sometimes recurs after surgical removal, but its pathogenic mechanisms are still unknown. On the other hand, the presence of secondary ERMs has been associated with various clinical conditions including proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR). Recent studies have shown a significant association between clinical grades of PDR or PVR, and the expression levels of specific cytokines and/or growth factors in the vitreous fluid. Expression of these factors and their receptors are also observed in secondary ERMs. ERMs are composed of many cell types such as retinal pigment epithelial cells and vascular endothelial cells, however the role of glial cells is yet unclear. Interestingly, glial cells in ERMs express some trophic factor receptors and transcription factors, such as NF-kappaB, suggesting an involvement of glial signal transduction in the pathogenesis of ERMs. In this review, we summarize recent progress regarding the clinical and laboratory findings of ERMs.

Intravitreous hepatocyte growth factor in patients with proliferative diabetic retinopathy: a case-control study

The aim of the present study was to evaluate the vitreous levels of hepatocyte growth factor (HGF) in patients with proliferative diabetic retinopathy (PDR) and to investigate its relationship with vascular endothelial growth factor (VEGF) and retinopathy activity. In addition, the relationship between intravitreous HGF levels and the presence of epiretinal membranes (ERM), as well as the expression of c-Met in ERM were also investigated. In this case-control study, serum and vitreous samples as well as ERM specimens were obtained during vitrectomy from 28 diabetic patients with PDR and 30 non-diabetic control subjects. HGF and VEGF were determined by ELISA and c-Met expression by immunohistochemistry. Vitreal levels of both VEGF and HGF were higher in patients with PDR in comparison with the control group (p<0.0001). However, after correcting for total vitreous protein concentration, HGF (ng/mg of proteins) was lower in diabetic patients than in non-diabetic control subjects (p=0.02). No correlation was detected between the vitreal levels of HGF and VEGF. In addition, intravitreous VEGF but not HGF was found to be related to PDR activity. Both diabetic patients and non-diabetic patients in whom ERM had been excised presented higher HGF intravitreous levels. Finally, a significant expression of c-Met in ERM membranes were observed in both diabetic patients with PDR and in non-diabetic subjects. In conclusion, both HGF and VEGF increased, but were not related, in the vitreous fluid of diabetic patients with PDR. Our findings suggest that HGF is related to pathological conditions in which fibroproliferative processes or wound healing are involved rather than with angiogenesis itself.

Involvement of protein kinase CK2 in angiogenesis and retinal neovascularization

PURPOSE

The purpose of the study was to characterize signaling intermediates involved in angiogenic responses of retinal endothelial cells (RECs) to the extracellular matrix and growth factors, by using specific inhibitors.

METHODS

Tubelike structure formation and the development of secondary sprouts on a basement membrane (BM) matrix, cell proliferation, and cell migration were studied in cultures of bovine and human RECs. Specific inhibitors were tested for inhibition of retinal neovascularization in a mouse model of oxygen-induced retinopathy (OIR).

RESULTS

In initial experiments, the broad-spectrum protein kinase inhibitors, H7 and H89, stabilized REC tubes on BM matrix and inhibited secondary sprouting, cell migration, and cell proliferation. Among more specific kinase inhibitors tested, only inhibitors of protein kinase CK2 (formerly, casein kinase II), such as emodin and DRB, were able to duplicate the effects of H7 and H89. Actinomycin D caused only minor changes in angiogenic assays, suggesting that CK2's effects on REC did not involve its known impact on transcription. The extent of retinal neovascularization in a mouse OIR model was reduced >70% (versus untreated or vehicle-treated groups) after treatment with emodin (6 days at 60 mg/kg per day) and by approximately 60% after treatment at the same dose with TBB, the most specific CK2 inhibitor known. In the treated retinas, the main vascular tree had minimal changes, but the neovascular tufts were greatly reduced in number or absent.

CONCLUSIONS

This is the first demonstration of the involvement of ubiquitous protein kinase CK2 in angiogenesis. Naturally derived CK2 inhibitors may be useful for treatment of proliferative retinopathies.

Intravitreous levels of hepatocyte growth factor/scatter factor and vascular cell adhesion molecule-1 in the vitreous fluid of diabetic patients with proliferative retinopathy

OBJECTIVE

Hepatocyte growth factor, also know as the scatter factor (HGF/SF) has been involved in the etiopathogenesis of proliferative diabetic retinopathy (PDR). To further explore this issue we have determine the intravitreous levels of HGF/SF taking into account the problems that could lead to misinterpretation of the results when the vitreous fluid is used to indirectly explore the events that are taking place in the retina. In addition, the relationship between HGF/SF and vascular cell adhesion molecule 1 (VCAM-1) was also investigated.

PATIENTS AND METHODS

Serum and vitreous samples were obtained during vitrectomy from 22 diabetic patients with PDR and 25 non-diabetic control subjects. Patients in whom intravitreous hemoglobin was detectable were excluded. A correction for plasma levels of either HGF/SF and VCAM-1 and intravitreal proteins was performed.

RESULTS

Vitreal levels of both HGF/SF and VCAM-1 were higher in patients with PDR in comparison with the control group (p<0.001 and p=0.003, respectively). However, after correcting for total vitreal proteins both HGF/SF and VCAM-1 (ng/mg of proteins) were lower in diabetic patients than in non-diabetic control subjects (p=0.03 and p<0.0001, respectively). No relationship between the vitreous levels of either HGF/SF or VCAM-1 with PDR activity was detected. Finally, a correlation between the vitreal levels of HGF/SF and VCAM-1 was observed in diabetic patients (r=0.61, p=0.005) but not in the control group.

CONCLUSION

Our results suggest that intraocular production of HGF/SF might be more important in mediating inflammatory and fibroproliferative processes rather than in angiogenesis itself.

Intravitreous leptin concentrations in patients with proliferative diabetic retinopathy

BACKGROUND

Previous studies have demonstrated that leptin is an angiogenic factor, and an increase in intravitreous leptin concentrations in diabetic patients with proliferative diabetic retinopathy (PDR) has also been described. The aim of the present study was to investigate the source of intravitreal leptin and to determine whether it is related to PDR activity.

METHODS

Serum and vitreous fluid samples were obtained simultaneously at the time of vitreoretinal surgery from 25 patients with PDR and 32 nondiabetic patients with nonproliferative ocular diseases (controls). Both groups were matched by age, sex, and body mass index. Leptin levels were determined by ELISA.

RESULTS

We did not observe any significant differences in vitreal levels of leptin between diabetic patients with PDR and controls (4.22 [2.6-9.7] versus 3.49 [1.9-9.7] ng/mL; P = not significant). Leptin concentrations were lower in vitreous fluid than in serum samples from diabetic patients with PDR (P < 0.001) and controls (P < 0.001). A direct correlation between serum and vitreous leptin concentrations was detected in diabetic patients with PDR (r = 0.60; P = 0.01) and controls (r = 0.51; P = 0.01). Finally, we did not observe any relationship between intravitreous leptin levels and PDR activity.

CONCLUSIONS

The intraocular production of leptin is not critically involved in the etiopathogenesis of PDR. In addition, our results suggest that serum diffusion is a relevant source of leptin in vitreous fluid.

Vitreous levels of pigment epithelium-derived factor and vascular endothelial growth factor: implications for ocular angiogenesis

PURPOSE

Pigment epithelium-derived factor (PEDF) has been demonstrated to suppress ocular angiogenesis in several animal models. In this study, we sought to measure the levels of PEDF and vascular endothelial growth factor (VEGF) in the vitreous of patients with and without ocular neovascular disorders.

DESIGN

Case-control study of patients undergoing intraocular surgery for a variety of neovascular and nonneovascular conditions.

METHODS

Vitreous samples were collected from 65 eyes of 65 patients with no neovascular disorder (n = 24), choroidal neovascularization (n = 9), active proliferative diabetic retinopathy (n = 16), and inactive proliferative diabetic retinopathy (n = 16). The levels of VEGF and PEDF in these vitreous samples were determined by enzyme-linked immunosorbent assay.

RESULTS

The VEGF levels were at or below the level of detectability in the reference and choroidal neovascularization groups. The VEGF levels were significantly elevated in both the active and inactive PDR groups, and significantly higher in the active PDR group as compared with the inactive PDR group. The PEDF levels, which were present at relatively high concentrations in all groups, were higher in patients with active PDR compared with the control and choroidal neovascularization groups.

CONCLUSIONS

High levels of immunoreactive PEDF are present in the vitreous of individuals with or without ocular neovascularization, but PEDF levels are significantly higher in patients with active PDR compared with patients with choroidal neovascularization or nonneovascular retinal diseases. Although these results do not preclude the possibility that endogenous PEDF helps to modulate ocular neovascularization, they do not support ischemia-induced downregulation of PEDF as a mechanism for such modulation.

Thrombosis increases circulatory hepatocyte growth factor by degranulation of mast cells

BACKGROUND

Plasma concentrations of hepatocyte growth factor (HGF), a powerful angiogenic growth factor inducible by heparin, increase in thrombus-associated disorders such as myocardial infarction and unstable angina. The mechanism of this thrombus-associated HGF release, however, is unknown.

METHODS AND RESULTS

Wistar rats received through the tail vein (1) normal saline (NS), (2) 50 micro g of the mast cell-degranulating agent CP48/80, or (3) 1000 U/kg heparin. Blood samples were collected at 10 minutes or 30 minutes after the injections, or from untreated rats, for measurements of HGF. The same experiments were performed in mast cell-deficient white spotting (Ws) rats. Ws rats have a small deletion of the c-kit gene and are deficient in mast cells. Intravenous heparin immediately increased plasma HGF in both Wistar (38.02+/-2.08 ng/mL versus 1.11+/-0.70 ng/mL in untreated rats, P<0.0001) and Ws rats (36.39+/-4.15 ng/mL versus 0.66+/-0.18 ng/mL in NS-treated rats, P<0.0001). Injection of CP48/80 also increased plasma HGF in Wistar rats (9.12+/-1.11 ng/mL versus 0.65+/-0.24 ng/mL in NS group, P=0.004) but not in Ws rats (0.67+/-0.27 ng/mL versus 0.66+/-0.18 ng/mL in NS group, P=0.997). In a rat carotid artery microthrombus model, intra-arterial thrombus formation increased circulating HGF in Wistar rats (2.12+/-0.70 ng/mL versus sham 0.61+/-0.15 ng/mL in sham-operated Wistar rats, P=0.0064) but not in Ws rats (0.76+/-0.33 ng/mL versus 0.21+/-0.04 ng/mL in sham-operated Ws rats, P=0.29). In addition, in vitro stimulation of rat peritoneal mast cells with thrombin rapidly induced degranulation in a dose-dependent manner.

CONCLUSIONS

These observations indicate that mast cell degranulation stimulated by thrombin is necessary for the rapid induction of plasma HGF in intravascular thrombus-associated disorders.

Effects of angiogenic growth factor combinations on retinal endothelial cells

The aim of this paper was to determine if growth factors, known to be upregulated in proliferative diabetic retinopathy, exerted combined effects on retinal endothelial cells. The authors explored the individual and collective actions of insulin-like growth factor I (IGF-I), vascular endothelial growth factor (VEGF), platelet-derived growth factor-BB (PDGF-BB), fibroblast growth factor-2 (FGF-2) and placenta growth factor (PlGF) on several parameters that reflect the angiogenic potential of endothelial cells. The effect of growth factors on cell migration and survival/proliferation was examined using primary cultures of bovine retinal endothelial cells (BREC). The authors also determined the growth factor action on capillary-like tube formation on a reconstituted basement membrane matrix and on the newly described phenomenon of secondary sprouting, in which endothelial cell colonies spontaneously survive, proliferate, migrate and invade the matrix after the original capillary-like tubes have collapsed. Sprouting cells were positive for von Willebrand factor and could aggregate into larger tubes with lumens. Incubation with VEGF+IGF-I or PlGF+FGF-2 enhanced tube stability by 40-50%, more than each growth factor alone or other combinations (5-20%). The concurrent addition of four growth factors did not improve the response seen with growth factor pairs. Surprisingly, PDGF-BB induced tube collapse. IGF-I and FGF-2 mildly enhanced BREC proliferation/survival (5-15%). However, VEGF+IGF-I or PlGF+FGF-2 increased BREC proliferation/survival by 25% under low serum conditions, whereas combinations of all four growth factors exerted a clearly synergistic effect (250% increase). PDGF-BB or FGF-2 stimulated secondary sprouting and were the only factors capable of exerting this effect alone. Even though VEGF, IGF-I or PlGF were not effective, if administered in pairs, they demonstrated increased responses. PDGF-BB was also able to enhance the effect of FGF-2+IGF-I+VEGF on BREC secondary sprouting, but not of any of them individually. No other growth factor tested was able to significantly improve the action of combinations of three other growth factors. VEGF increased cell migration in a wounded monolayer assay two-fold and PDGF-BB, 2.5 times, but other individual growth factors were ineffective. PlGF+FGF-2 enhanced cell migration more than each factor alone. VEGF+IGF-I+PlGF+FGF-2, however, increased cell migration four-fold. In summary, this study indicates that growth factors, overexpressed in diabetic retinopathy eyes, enhance the angiogenic characteristics of cultured cells (tube formation, proliferation, secondary sprouting and migration). Their effects, however, can be greatly augmented by other growth factors that alone exert little or no action. Therefore, diabetic retinal neovascularization may result from the additive or synergistic action of several growth factors.

Hepatocyte growth factor is increased in the aqueous humor of glaucomatous eyes

PURPOSE

To assess the concentrations of hepatocyte growth factor (HGF) in the aqueous humor of eyes with glaucoma compared with control eyes with cataract only.

METHODS

Concentrations of HGF were measured in aqueous humor aspirates taken during anterior segment surgery from 84 patients, of whom 72 had glaucoma (38 cases of primary open-angle glaucoma, 17 angle-closure glaucoma, and 17 exfoliative glaucoma) and 12 had cataract only, using a sandwich enzyme-linked immunosorbent assay kit.

RESULTS

Hepatocyte growth factor was detected in all samples. The concentration in eyes with cataract only was 563.3 +/- 178.8 pg/mL (mean +/- standard deviation), which was significantly lower than that in eyes with glaucoma (967.1 +/- 514.7 pg/mL, P < 0.01). Eyes with exfoliative glaucoma had significantly higher HGF concentrations (1,425.5 +/- 586.7 pg/mL) than did eyes with primary open-angle glaucoma (855.0 +/- 341.5 pg/mL) and angle-closure glaucoma (759.4 +/- 511.4 pg/mL) (P < 0.01). There was no effect of age, sex, or history of medical, laser, or surgical treatment on the aqueous humor HGF concentration (P > 0.05). Aqueous humor and plasma HGF concentrations were measured and compared in 28 patients. The aqueous humor HGF concentration (908 +/- 586.2 pg/mL) was significantly higher (P < 0.01) than the plasma concentration (521.3 +/- 183.1 pg/mL). No significant correlation could be found between aqueous humor and plasma HGF concentrations.

CONCLUSIONS

The relatively high concentration of HGF in human aqueous humor suggests that HGF may play an important role in ocular physiology and disease. The higher concentration in patients with glaucoma may indicate a response to injury.