Combination angiostatic therapy completely inhibits ocular and tumor angiogenesis

Emerging nanotechnological approaches to regulating tumor vasculature for cancer therapy

Abnormal angiogenesis stands for one of the most striking manifestations of malignant tumor. The pathologically and structurally abnormal tumor vasculature facilitates a hostile tumor microenvironment, providing an ideal refuge exclusively for cancer cells. The emergence of vascular regulation drugs has introduced a distinctive class of therapeutics capable of influencing nutrition supply and drug delivery efficacy without the need to penetrate a series of physical barriers to reach tumor cells. Nanomedicines have been further developed for more precise regulation of tumor vasculature with the capacity of co-delivering multiple active pharmaceutical ingredients, which overall reduces the systemic toxicity and boosts the therapeutic efficacy of free drugs. Additionally, precise structure design enables the integration of specific functional motifs, such as surface-targeting ligands, droppable shells, degradable framework, or stimuli-responsive components into nanomedicines, which can improve tissue-specific accumulation, enhance tissue penetration, and realize the controlled and stimulus-triggered release of the loaded cargo. This review describes the morphological and functional characteristics of tumor blood vessels and summarizes the pivotal molecular targets commonly used in nanomedicine design, and then highlights the recent cutting-edge advancements utilizing nanotechnologies for precise regulation of tumor vasculature. Finally, the challenges and future directions of this field are discussed.

OCTA changes following loading phase with intravitreal aflibercept for DME

OBJECTIVE

To quantify changes in optical coherence tomography angiography (OCTA) parameters following intravitreal anti-vascular endothelial growth factor treatment for diabetic macular edema (DME), and to assess associations between pretreatment OCTA parameters and visual outcomes.

DESIGN

Prospective cohort study.

METHODS

Twenty-nine patients with DME received 5 monthly intravitreal injections of aflibercept. OCTA data obtained at baseline and at 6 months were compared using the Wilcoxon signed-rank test. OCTA parameters were foveal avascular zone (FAZ) area, FAZ perimeter, FAZ circularity, vessel density in the superficial vascular plexus (segmented into central, inner, outer, and full Early Treatment of Diabetic Retinopathy Study [ETDRS] map regions. Subanalysis divided patients into treatment responders (reduction of central subfield thickness >50 µm over treatment) and nonresponders. Associations between pretreatment OCTA parameters and visual acuity outcomes were analyzed using multivariable linear and logistic regression.

RESULTS

A total of 29 patients were included: 25 patients (86.2%) had nonproliferative diabetic retinopathy, and 4 patients (13.8%) had proliferative diabetic retinopathy. Vessel density was reduced in the central (p = 0.004) and inner (p = 0.013) ETDRS map regions. This effect was significant only among treatment responders (central p = 0.002; inner p = 0.017). Pretreatment OCT and OCTA parameters were not associated with final visual acuity outcomes.

CONCLUSION

Following intravitreal aflibercept treatment for DME, there was a significant decrease in vessel density of the superficial vascular plexus at the central and inner ETDRS map regions. This was seen only among treatment responders. Observations here are likely to represent the limits of OCTA technology itself, where pretreatment vessel density may have been artifactually overestimated by suspended scattering particles in motion. Pretreatment OCTA parameters did not serve as biomarkers for visual outcome following anti-vascular endothelial growth factor therapy.

Reduced Size of Telangiectatic Capillaries After Intravitreal Injection of Anti-Vascular Endothelial Growth Factor Agents in Diabetic Macular Edema

Purpose

Intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) agents reduces microaneurysms in patients with diabetic macular edema (DME). However, residual anti-VEGF-resistant telangiectatic capillaries (TelCaps) have been reported. In this study, we investigated changes in the size of TelCaps after intravitreal injection of anti-VEGF agents in DME.

Patients and Methods

Indocyanine green angiography (IA) and optical coherence tomography were performed before and 3 months after the intravitreal injection of anti-VEGF agents (pro re nata regimen after three monthly loading doses) in 12 eyes of 12 patients (7 males and 5 females, mean age 65.2 ± 8.8 years) with DME. The number and size of TelCaps within a 6-mm diameter macular region of the edema were measured using optical coherence tomography B-scan images overlaid on IA images.

Results

There were significant reductions in the number and size of TelCaps between the baseline and 3 months after anti-VEGF agent administration (P < 0.05 and P < 0.0001, respectively). The maximum corrected visual acuity (logMAR visual acuity) and the central macular thickness after anti-VEGF therapy were significantly improved (P < 0.01 and P < 0.02, respectively). The TelCaps remaining after loading three consecutive anti-VEGF agents had a significantly larger mean size at baseline than the TelCaps that resolved after the treatment (P < 0.03).

Conclusion

Our study demonstrated that intravitreal injection of anti-VEGF agents could reduce TelCap size in patients with DME. We propose that larger-sized TelCaps detected by IA might be useful predictors of refractory DME, which could thus be principal targets of laser photocoagulation.

miR-125a-5p attenuates macrophage-mediated vascular dysfunction by targeting Ninjurin1

Ninjurin1 (Ninj1), an adhesion molecule, regulates macrophage function in hyaloid regression, multiple sclerosis, and atherosclerosis. However, its biological relevance and the mechanism underlying its function in vascular network integrity have not been studied. In this study, we investigated the role of Ninj1 in physiological (postnatal vessel formation) and pathological (endotoxin-mediated inflammation and diabetes) conditions and developed a strategy to regulate Ninj1 using specific micro (mi)RNAs under pathological conditions. Ninj1-deficient mice exhibited decreased hyaloid regression, tip cell formation, retinal vascularized area, recruitment of macrophages, and endothelial apoptosis during postnatal development, resulting in delayed formation of the vascular network. Five putative miRNAs targeting Ninj1 were selected using the miRanda algorithm and comparison of expression patterns. Among them, miR-125a-5p showed a profound inhibitory effect on Ninj1 expression, and miR-125a-5p mimic suppressed the cell-to-cell and cell-to-matrix adhesion of macrophages and expression of pro-inflammatory factors mediated by Ninj1. Furthermore, miR-125a-5p mimic inhibited the recruitment of macrophages into inflamed retinas in endotoxin-induced inflammation and streptozotocin-induced diabetes in vivo. In particular, miR-125a-5p mimic significantly attenuated vascular leakage in diabetic retinopathy. Taken together, these findings suggest that Ninj1 plays a pivotal role in macrophage-mediated vascular integrity and that miR-125a-5p acts as a novel regulator of Ninj1 in the management of inflammatory diseases and diabetic retinopathy.

Disentangling the association between retinal non-perfusion and anti-VEGF agents in diabetic retinopathy

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes mellitus (DM) and the leading cause of blindness in patients with DM. In the pathogenesis of DR, chronic hyperglycemia leads to biochemical and structural alterations in retinal blood vessels' wall, resulting in hyperpermeability and non-perfusion. Since vascular endothelial growth factor (VEGF) has been found to play a significant role in the pathogenesis of DR, this review sheds light on the effect of intravitreal anti-VEGF agents on retinal non-perfusion in patients with DR. Based on the existing literature, anti-VEGF agents have been shown to improve DR severity, although they cannot reverse retinal ischemia. The results of the published studies are controversial and differ based on the location of retinal non-perfusion, as well as the imaging modality used to assess retinal non-perfusion. In cases of macular non-perfusion, most of studies showed no change in both fundus fluorescein angiography (FFA) and optical coherence tomography (OCTA) in patients with DR treated with intravitreal anti-VEGF agents, while few studies reported worsening of non-perfusion with enlargement of foveal avascular zone (FAZ). Regarding peripheral ischemia, studies using wide-field-FFA demonstrated an improvement or stability in non-perfusion areas after anti-VEGF treatment. However, the use of wide-field-OCTA revealed no signs of re-perfusion of retinal vessels post anti-VEGF treatment. Further prospective studies with long follow-up and large sample size are still needed to draw solid conclusions.

Review on Recent Trials Evaluating the Effect of Intravitreal Injections of Anti-VEGF Agents on the Macular Perfusion of Diabetic Patients with Diabetic Macular Edema

Background

Diabetic macular edema (DME) is a major cause of vision loss in diabetics worldwide. Anti-vascular endothelial growth factor (anti-VEGF) agents have become the mainstay of treatment of vision loss due to DME. Long-term effects of these agents on the macular perfusion (MP) are a current concern.

Objective

To review recently published studies that evaluated the effect of intravitreal injection of anti-VEGF agents on the MP of diabetics with DME.

Methods

Different databases were searched including PubMed, Medline, Ovid, Science Direct, and Google Scholar for relevant studies published between 2010 and 2019. All studies found were compared regarding methodology and results and included in this review. Some studies relating to retinal perfusion in general and not strictly MP were also included for comprehensiveness.

Results

Several studies utilizing different anti-VEGF agents were identified. All the large randomized controlled clinical trials identified utilized primarily fluorescein angiography (FA) and human graders and found generally no worsening of MP associated with anti-VEGF agents use in diabetic patients with DME. Some of these studies, however, depended on post-hoc analysis. Several more recent, but smaller case series, have utilized the relatively new and non-invasive optical coherence tomography angiography (OCTA) in this evaluation and found more conflicting results.

Conclusion

The large clinical trials recently performed depended mainly on FA in the analysis of MP changes following injections and generally found no worsening of MP. More recently, smaller case series have utilized OCTA in this analysis, yielding more conflicting results. Large randomized controlled trials using OCTA are thus needed.

Intravitreal Anti-Vascular Endothelial Growth Factor Agents for the Treatment of Diabetic Retinopathy: A Review of the Literature

Background: Diabetic retinopathy (DR) is the leading cause of blindness in the working-age population. The purpose of this review is to gather the existing literature regarding the use of the approved anti-vascular endothelial growth (anti-VEGF) agents in the treatment of DR. Methods: A comprehensive literature review in PubMed engine search was performed for articles written in English language up to 1 July 2021, using the keywords “diabetic retinopathy”, “ranibizumab”, “aflibercept”, and “anti-VEGF”. Emphasis was given on pivotal trials and recent robust studies. Results: Intravitreal anti-VEGF agents have been found to significantly improve visual acuity and reduce retinal thickness in patients with diabetic macular edema (DME) in a long-term follow-up ranging from 1 to 5 years and are considered the standard-of-care in such patients. Regarding DR, intravitreal anti-VEGF agents provided ≥2-step improvement in DR severity on color fundus photography in about 30–35% of patients with NPDR at baseline, in the majority of clinical trials originally designed to evaluate the efficacy of intravitreal anti-VEGF agents in patients with DME. Protocol S and CLARITY study have firstly reported that intravitreal anti-VEGF agents are non-inferior to panretinal photocoagulation (PRP) in patients with proliferative DR (PDR). However, the use of new imaging modalities, such as optical coherence tomography-angiography and wide-field fluorescein angiography, reveals conflicting results about the impact of anti-VEGF agents on the regression of retinal non-perfusion in patients with DR. Furthermore, one should consider the high “loss to follow-up” rate and its devastating consequences especially in patients with PDR, when deciding to treat the latter with intravitreal anti-VEGF agents alone compared to PRP. In patients with PDR, combination of treatment of intravitreal anti-VEGF agents and PRP has been also supported. Moreover, in the specific case of vitreous hemorrhage or tractional retinal detachment as complications of PDR, intravitreal anti-VEGF agents have been found to be beneficial as an adjunct to pars plana vitrectomy (PPV), most commonly given 3–7 days before PPV, offering reduction in the recurrence of vitreous hemorrhage. Conclusions: There is no general consensus regarding the use of intravitreal anti-VEGF agents in patients with DR. Although anti-VEGF agents are the gold standard in the treatment of DME and seem to improve DR severity, challenges in their use exist and should be taken into account in the decision of treatment, based on an individualized approach.

CD146/Soluble CD146 Pathway Is a Novel Biomarker of Angiogenesis and Inflammation in Proliferative Diabetic Retinopathy

Purpose

Inflammation, angiogenesis and fibrosis are pathological hallmarks of proliferative diabetic retinopathy (PDR). The CD146/sCD146 pathway displays proinflammatory and proangiogenic properties. We investigated the role of this pathway in the pathophysiology of PDR.

Methods

Vitreous samples from 41 PDR and 27 nondiabetic patients, epiretinal fibrovascular membranes from 18 PDR patients, rat retinas, human retinal microvascular endothelial cells (HRMECs) and human retinal Müller glial cells were studied by ELISA, Western blot analysis, immunohistochemistry and immunofluorescence microscopy analysis. Blood-retinal barrier breakdown was assessed with fluorescein isothiocyanate-conjugated dextran.

Results

sCD146 and VEGF levels were significantly higher in vitreous samples from PDR patients than in nondiabetic patients. In epiretinal membranes, immunohistochemical analysis revealed CD146 expression in leukocytes, vascular endothelial cells and myofibroblasts. Significant positive correlations were detected between numbers of blood vessels expressing CD31, reflecting angiogenic activity of PDR, and numbers of blood vessels and stromal cells expressing CD146. Western blot analysis showed significant increase of CD146 in diabetic rat retinas. sCD146 induced upregulation of phospho-ERK1/2, NF-κB, VEGF and MMP-9 in Müller cells. The hypoxia mimetic agent cobalt chloride, VEGF and TNF-α induced upregulation of sCD146 in HRMECs. The MMP inhibitor ONO-4817 attenuated TNF-α-induced upregulation of sCD146 in HRMECs. Intravitreal administration of sCD146 in normal rats significantly increased retinal vascular permeability and induced significant upregulation of phospho-ERK1/2, intercellular adhesion molecule-1 and VEGF in the retina. sCD146 induced migration of HRMECs.

Conclusions

These results suggest that the CD146/sCD146 pathway is involved in the initiation and progression of PDR.

CD160 protein as a new therapeutic target in a battle against autoimmune, infectious and lifestyle diseases. Analysis of the structure, interactions and functions

The glycosylphosphatidylinositol-anchored transmembrane glycoprotein CD160 (cluster of differentiation 160) is a member of the immunoglobulin superfamily. Four isoforms, which differ by the presence or absence of an immunoglobulin-like domain and the mode of anchoring in the cell membrane, have been identified. CD160 has a significant impact on the proper functioning of the immune system by activating natural killer cells and inhibiting T cells. CD160 is a natural ligand for herpes virus entry mediator (HVEM), a member of the tumor necrosis factor superfamily. The CD160-HVEM complex is a rare example of direct interaction between the two different superfamilies. The interaction of these two proteins leads to the inhibition of CD4⁺ T cells which, in consequence, leads to the inhibition of the correct response of the immune system. Available research articles indicate that CD160 plays a role in various types of cancer, chronic viral diseases, malaria, paroxysmal nocturnal hemoglobinuria, atherosclerosis, autoimmune diseases, skin inflammation, acute liver damage and retinal vascular disease. We present here an overview of the CD160 protein, the general characteristics of the receptor and its isoforms, details of structural studies of CD160 and the CD160-HVEM complex, as well as a description of the role of this protein in selected human diseases.

A novel method of screening combinations of angiostatics identifies bevacizumab and temsirolimus as synergistic inhibitors of glioma-induced angiogenesis

Tumor angiogenesis is critical for the growth and progression of cancer. As such, angiostasis is a treatment modality for cancer with potential utility for multiple types of cancer and fewer side effects. However, clinical success of angiostatic monotherapies has been moderate, at best, causing angiostatic treatments to lose their early luster. Previous studies demonstrated compensatory mechanisms that drive tumor vascularization despite the use of angiostatic monotherapies, as well as the potential for combination angiostatic therapies to overcome these compensatory mechanisms. We screened clinically approved angiostatics to identify specific combinations that confer potent inhibition of tumor-induced angiogenesis. We used a novel modification of the ex ovo chick chorioallantoic membrane (CAM) model that combined confocal and automated analyses to quantify tumor angiogenesis induced by glioblastoma tumor onplants. This model is advantageous due to its low cost and moderate throughput capabilities, while maintaining complex in vivo cellular interactions that are difficult to replicate in vitro. After screening multiple combinations, we determined that glioblastoma-induced angiogenesis was significantly reduced using a combination of bevacizumab (Avastin®) and temsirolimus (Torisel®) at doses below those where neither monotherapy demonstrated activity. These preliminary results were verified extensively, with this combination therapy effective even at concentrations further reduced 10-fold with a CI value of 2.42E-5, demonstrating high levels of synergy. Thus, combining bevacizumab and temsirolimus has great potential to increase the efficacy of angiostatic therapy and lower required dosing for improved clinical success and reduced side effects in glioblastoma patients.

Optical Coherence Tomography Angiography of Macular Perfusion Changes after Anti-VEGF Therapy for Diabetic Macular Edema: A Systematic Review

BACKGROUND

Diabetic macular edema (DME) is a major cause of vision loss in diabetics that is currently mainly treated by antivascular endothelial growth factor (VEGF) agents. The effect of these agents on macular perfusion (MP) is a current concern. Optical coherence tomography angiography (OCTA) is an imaging modality that allows noninvasive high-resolution retinal microvasculature imaging. Several recent studies evaluated the effect of anti-VEGF agents on the MP of DME patients using OCTA. Our aim is to provide a systematic review of these studies.

METHODS

Multiple databases were searched including PubMed, Ovid Medline, EMBASE, and Google Scholar for relevant studies published between January 2016 and November 2020 which were included in this review. Studies were compared regarding their design, the number of included patients, the machine and scanning protocol used, the inclusion and exclusion criteria, the number of injections given, the type of anti-VEGF agent used, the outcome measures assessed, and the effect of injections on different MP parameters.

RESULTS

A total of 16 studies were included. The studies assessed various OCTA parameters that define MP including the foveal avascular zone area and superficial and deep vascular density and yielded conflicting results. Seven studies showed stable or improved MP following treatment, while 7 studies showed worsening MP following treatment, and 2 studies showed inconclusive results. This could have been due to differences in study design, inclusion criteria, type of anti-VEGF agents used, treatment duration, and methods of image analysis and vascular density quantification. All identified studies were noncomparative case series, and 14 of them (87.5%) used the RTVue XR Avanti OCTA machine. Only one study compared OCTA to fluorescein angiography findings.

CONCLUSION

Analysis of MP changes following VEGF inhibition for DME could benefit from a unified scanning protocol and analysis approach that uses similar study designs to eliminate potential sources of bias. This may provide more definitive conclusions regarding the effect of treatment on MP.

Clinical Efficacy and Safety of Propranolol in the Prevention and Treatment of Retinopathy of Prematurity: A Meta-Analysis of Randomized Controlled Trials

Objective: To perform a meta-analysis of randomized controlled trials verifying clinical efficacy and safety of propranolol in pre-term newborns with retinopathy of prematurity (ROP). Methods: We searched the literature databases (Pubmed, Embase, The Cochrane Library, Web of Science, CNKI, WanFang, VIP, CBM) for publications before August 10, 2020, and the World Health Organization's International Clinical Trials Registry and ClinicalTrials.gov for ongoing trials. Randomized controlled trials (RCTs) of propranolol for the prevention or treatment of ROP were included. The quality of the included studies was primarily assessed by the RCT tool of the Cochrane Collaboration. The included studies were quantified using a meta-analysis of relative risk (RR) estimated with a random effect model. Results: Our original search identified 171 articles, and five studies met our criteria. A meta-analysis was performed that showed that infants orally treated with propranolol had a decreased risk of disease progression: stage progression had an RR = 0.65 [95% confidence interval (CI), 0.47-0.88]), plus disease had an RR = 0.43 [95% CI, 0.22-0.82]. The demands for additional treatments had similar protective results: laser photocoagulations had an RR = 0.55 [95% CI, 0.35-0.86]), and intravitreal injection of anti-vascular endothelial growth factor had an RR = 0.45 [95% CI, 0.22-0.90]). The oral administration of propranolol was associated with an increased risk of adverse events (RR = 2.01 [95% CI, 1.02-3.97]). High-risk adverse events included bradycardia, hypotension, not gaining enough weight, bronchospasm, hypoglycemia, apnea, and increasing ventilator need. Subgroup analysis of ROP phases and stages found that the risk in stage 2 ROP of the second phase and the individual risk factors (stage progression, RR = 0.42 [95% CI, 0.27-0.65]; plus disease, RR = 0.40 [95% CI, 0.17-0.93]; laser photocoagulation, RR = 0.31 [95% CI, 0.14-0.68]) have statistically significant differences compared with other phases and stages. Conclusions: Pre-term newborns with ROP, especially in stage 2 ROP of the second phase, who were orally given propranolol have a reduced risk of disease progression and demand for additional treatments, but the safety needs more attention.

An allosteric peptide inhibitor of HIF-1α regulates hypoxia-induced retinal neovascularization

Retinal neovascularization (NV), a leading cause of vision loss, results from localized hypoxia that stabilizes the hypoxia-inducible transcription factors HIF-1α and HIF-2α, enabling the expression of angiogenic factors and genes required to maintain homeostasis under conditions of oxygen stress. HIF transcriptional activity depends on the interaction between its intrinsically disordered C-terminal domain and the transcriptional coactivators CBP/p300. Much effort is currently directed at disrupting protein-protein interactions between disease-associated transcription factors like HIF and their cellular partners. The intrinsically disordered protein CITED2, a direct product of HIF-mediated transcription, functions as a hypersensitive negative regulator that attenuates the hypoxic response by competing allosterically with HIF-1α for binding to CBP/p300. Here, we show that a peptide fragment of CITED2 is taken up by retinal cells and efficiently regulates pathological angiogenesis in murine models of ischemic retinopathy. Both vaso-obliteration (VO) and NV were significantly inhibited in an oxygen-induced retinopathy (OIR) model following intravitreal injection of the CITED2 peptide. The CITED2 peptide localized to retinal neurons and glia, resulting in decreased expression of HIF target genes. Aflibercept, a commonly used anti-VEGF therapy for retinal neovascular diseases, rescued NV but not VO in OIR. However, a combination of the CITED2 peptide and a reduced dose of aflibercept significantly decreased both NV and VO. In contrast to anti-VEGF agents, the CITED2 peptide can rescue hypoxia-induced retinal NV by modulating the hypoxic response through direct competition with HIF for CBP/p300, suggesting a dual targeting strategy for treatment of ischemic retinal diseases and other neovascular disorders.

Evaluation of Changes in Macular Perfusion Detected by Optical Coherence Tomography Angiography following 3 Intravitreal Monthly Bevacizumab Injections for Diabetic Macular Edema in the IMPACT Study

Objective

To evaluate macular perfusion changes following intravitreal bevacizumab injections for diabetic macular edema (DME) using spectral domain optical coherence tomography angiography (SD-OCTA).

Methods

This study was a prospective noncomparative interventional case series. Treatment naïve patients with DME underwent full ophthalmological examination and SD-OCTA scanning at baseline and after 3 intravitreal bevacizumab injections. Both the 6 × 6 and 3 × 3 mm macular scan protocols were used. Pretreatment and posttreatment OCTA images were automatically aligned using a commercially available retina alignment software (i2k Align Retina software); then the fractal dimension (FD), vascular density (VD), and skeleton VD changes were obtained at the full retinal thickness (Full) and superficial (SCP) and deep (DCP) capillary plexuses after processing images using a semiautomated program. The foveal avascular zone (FAZ) was manually measured and FD was calculated using the FracLac plugin of ImageJ.

Results

Forty eyes of 26 patients were included. Following injections, there were an 8.1% increase in FAZ, 1.3% decrease in FD-Full and FD-SCP, 1.9% decrease in FD-DCP, 8% decrease in VD-Full, 9.1% decrease in VD-SCP, 10.6% decrease in VD-DCP, 13.3% decrease in skeleton VD-Full, 12.5% decrease in skeleton VD-SCP, and 16.3% decrease in skeleton VD-DCP in the 6 × 6 mm macular area and a 2.6% decrease in FD-Full, 3.4% decrease in FD-SCP, 11.5% decrease in VD-Full, 14.3% decrease in VD-SCP, and 25.1% decrease in skeleton VD-SCP in the 3 × 3 mm macular area which were all statistically significant (p < 0.05). Using univariate and multivariate analysis, the pretreatment FD, VD, and skeleton VD at each capillary layer significantly negatively correlated with the change in FD, VD, and skeleton VD at the corresponding capillary layer, respectively (p < 0.05).

Conclusion

OCTA is a useful noninvasive tool for quantitative evaluation of macular perfusion changes following DME treatment. This trial is registered with NCT03246152.

Galectin-1 studies in proliferative diabetic retinopathy

PURPOSE

Galectin-1 regulates endothelial cell function and promotes angiogenesis. We investigated the hypothesis that galectin-1 may be involved in the pathogenesis of proliferative diabetic retinopathy (PDR).

METHODS

Vitreous samples from 36 PDR and 20 nondiabetic patients, epiretinal fibrovascular membranes from 13 patients with PDR, rat retinas and human retinal Müller glial cells were studied by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry and Western blot analysis. In vitro angiogenesis assays were performed and the adherence of leukocytes to galectin-1-stimulated human retinal microvascular endothelial cells (HRMECs) was assessed.

RESULTS

The ELISA analysis revealed that galectin-1 and vascular endothelial growth factor (VEGF) levels were significantly higher in vitreous samples from PDR patients than in those from nondiabetics (p < 0.001 for both comparisons). A significant positive correlation was found between the levels of galectin-1 and VEGF (r = 0.354; p = 0.022). In epiretinal membranes, immunohistochemical analysis showed that galectin-1 was expressed in vascular endothelial cells expressing CD31, myofibroblasts expressing α-smooth muscle actin and leukocytes expressing CD45. The galectin-1 receptor neuropilin-1 was expressed on vascular endothelial cells. CD31 staining was used as a marker to assess microvessel density (MVD). Significant positive correlation was detected between MVD in epiretinal membranes and the number of blood vessels expressing galectin-1 (r = 0.848; p < 0.001). Western blot analysis demonstrated significant increase of galectin-1 protein in rat retinas after induction of diabetes. ELISA analysis revealed that hydrogen peroxide and cobalt chloride (CoCl₂ ) induced upregulation of galectin-1 in Müller cells. Treatment with galectin-1 induced upregulation of VEGF in Müller cells and increased leukocyte adhesion to HRMECs. The galectin-1 inhibitor OTX008 attenuated VEGF-induced HRMECs migration and CoCl₂ -induced upregulation of NF-κB, galectin-1 and VEGF in Müller cells.

CONCLUSIONS

These results suggest that galectin-1is involved in the pathogenesis of PDR.

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.

Targeting the Tie2-αvβ3 integrin axis with bi-specific reagents for the inhibition of angiogenesis

BACKGROUND

Increased activity of the receptor tyrosine kinase Tie2 has been implicated in the promotion of pathological angiogenesis. This activity is mainly mediated through angiopoietin (Ang)1- and Ang2-dependent activation of integrins by Tie2, rendering the Ang/Tie2/integrin axis an attractive putative target for cancer therapeutics.

RESULTS

To target this axis, we developed single domain, non-immunoglobulin high-affinity bi-specific protein inhibitors against both Tie2 and αvβ3 integrin. We have previously engineered the Ang2-binding domain of Tie2 (Ang2-BD) as a Tie2 inhibitor. Here, we engineered an exposed loop in Ang2-BD to generate variants that include an integrin-binding Arg-Gly-Asp (RGD) motif and used flow cytometry screening of a yeast-displayed Ang2-BD RGD loop library to identify the integrin antagonists. The bi-specific antagonists targeting both Tie2 and αvβ3 integrin inhibited adhesion and proliferation of endothelial cells cultured together with the αvβ3 integrin ligand vitronectin, as well as endothelial cell invasion and tube formation. The bi-specific reagents inhibited downstream signaling by Tie2 intracellularly in response to its agonist Ang1 more effectively than the wild-type Ang2 BD that binds Tie2 alone.

CONCLUSIONS

Collectively, this study-the first to describe inhibitors targeting all the known functions resulting from Tie2/integrin αvβ3 cross-talk-has created new tools for studying Tie2- and integrin αvβ3-dependent molecular pathways and provides the basis for the rational and combinatorial engineering of ligand-Tie2 and ligand-integrin αvβ3 receptor interactions. Given the roles of these pathways in cancer angiogenesis and metastasis, this proof of principle study paves the route to create novel Tie2/integrin αvβ3-targeting proteins for clinical use as imaging and therapeutic agents.

Matrix metalloproteinase-14 is a biomarker of angiogenic activity in proliferative diabetic retinopathy

Purpose

Matrix metalloproteinase-14 (MMP-14) is a transmembrane MMP that plays a critical role in promoting angiogenesis. We investigated the expression levels of MMP-14 and correlated the levels with clinical disease activity and with the levels of the angiogenic factors vascular endothelial growth factor (VEGF) and MMP-9 in proliferative diabetic retinopathy (PDR). To reinforce the findings at the functional level, we examined the expression of MMP-14 in the retinas of diabetic rats.

Methods

Vitreous samples from 34 patients with PDR and 18 nondiabetic patients and epiretinal membranes from 13 patients with PDR and the retinas of rats were studied with enzyme-linked immunosorbent assay, immunohistochemistry, western blotting, and real-time reverse transcription PCR (RT-PCR).

Results

The MMP-14, VEGF, and MMP-9 levels were statistically significantly higher in the vitreous samples from patients with PDR than in the samples from the nondiabetic controls (p<0.001 for all comparisons). The MMP-14 levels in patients with PDR with active neovascularization were statistically significantly higher than those in patients with inactive PDR (p<0.001). There were statistically significant positive correlations between levels of MMP-14 and levels of VEGF (r = 0.3; p = 0.032) and MMP-9 (r = 0.54; p<0.001). In the epiretinal membranes, MMP-14 was expressed in vascular endothelial cells, leukocytes, and myofibroblasts. Statistically significant positive correlations were detected between the numbers of blood vessels expressing CD31 and the numbers of blood vessels (r = 0.74; p = 0.004) and stromal cells (r = 0.72; p = 0.005) expressing MMP-14. Statistically significant increases of MMP-14 mRNA and protein were detected in rat retinas after induction of diabetes.

Conclusions

These results suggest that MMP-14 is involved in PDR angiogenesis.

Differential expression and localization of human tissue inhibitors of metalloproteinases in proliferative diabetic retinopathy

PURPOSE

Tissue inhibitors of metalloproteinases (TIMPs) block the catalysis by matrix metalloproteinases (MMPs) and have additional biologic activities, including regulation of cell growth and differentiation, apoptosis, angiogenesis and oncogenesis. We investigated the expression levels of all the four human TIMPs and correlated these levels with those of MMP-9 and vascular endothelial growth factor (VEGF) in proliferative diabetic retinopathy (PDR).

METHODS

Vitreous samples from 38 PDR and 21 nondiabetic control patients and epiretinal membranes from 14 patients with PDR and 10 patients with proliferative vitreoretinopathy (PVR) were studied by enzyme-linked immunosorbent assay, Western blot analysis and immunohistochemistry.

RESULTS

Tissue inhibitor of metalloproteinases-1, TIMP-4, MMP-9 and VEGF levels were significantly higher in vitreous samples from PDR patients than in nondiabetic controls (p < 0.0001 for all comparisons), whereas TIMP-2 and TIMP-3 levels did not differ significantly. TIMP-1, TIMP-4, MMP-9 and VEGF levels in PDR with active neovascularization were significantly higher than those in inactive PDR (p < 0.0001, 0.001, 0.013, 0.004, respectively). Significant positive correlations existed between levels of TIMP-1 and levels of TIMP-4 (r = 0.37; p = 0.004), MMP-9 (r = 0.65; p < 0.0001) and VEGF (r = 0.59; p < 0.0001), between levels of TIMP-4 and levels of MMP-9 (r = 0.61; p < 0.0001) and VEGF (r = 0.62; p < 0.0001) and between levels of MMP-9 and VEGF (r = 0.62; p < 0.0001). TIMP-1 and TIMP-3 were expressed in vascular endothelial cells in PDR epiretinal membranes and in myofibroblasts and leucocytes in PDR and PVR epiretinal membranes.

CONCLUSION

The differential expression of TIMPs in PDR suggests that among the 4 TIMPs, TIMP-1 and TIMP-4 may be possible biomarkers of disease activity.

Extracellular matrix metalloproteinase inducer (EMMPRIN) is a potential biomarker of angiogenesis in proliferative diabetic retinopathy

PURPOSE

Extracellular matrix metalloproteinase inducer (EMMPRIN) promotes angiogenesis through matrix metalloproteinases (MMPs) and vascular endothelial growth factor (VEGF) production. We investigated the expression levels of EMMPRIN and correlated these levels with VEGF, MMP-1 and MMP-9 in proliferative diabetic retinopathy (PDR). In addition, we examined the expression of EMMPRIN in the retinas of diabetic rats and the effect of EMMPRIN on the induction of angiogenesis regulatory factors in human retinal microvascular endothelial cells (HRMECs).

METHODS

Vitreous samples from 40 PDR and 19 non-diabetic patients, epiretinal membranes from 12 patients with PDR, retinas of rats and HRMECs were studied by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, Western blot analysis, zymography analysis and RT-PCR.

RESULTS

We showed a significant increase in the expression of EMMPRIN, VEGF, MMP-1 and MMP-9 in vitreous samples from PDR patients compared with non-diabetic controls (p < 0.0001; p = 0.001; p = 0.009; p < 0.0001, respectively). Significant positive correlations were found between the levels of EMMPRIN and the levels of VEGF (r = 0.38; p = 0.003), MMP-1 (r = 0.36; p = 0.005) and MMP-9 (r = 0.46; p = 0.003). In epiretinal membranes, EMMPRIN was expressed in vascular endothelial cells and stromal cells. Significant increase of EMMPRIN mRNA was detected in rat retinas after induction of diabetes. EMMPRIN induced hypoxia-inducible factor-1α, VEGF and MMP-1 expression in HRMEC.

CONCLUSIONS

These results suggest that EMMPRIN/MMPs/VEGF pathway is involved in PDR angiogenesis.

Unbalanced Vitreous Levels of Osteoprotegerin, RANKL, RANK, and TRAIL in Proliferative Diabetic Retinopathy

PURPOSE

We investigated the expression of the proinflammatory and proangiogenic factor osteoprotegerin (OPG) and its ligands, receptor activator of nuclear factor-κB ligand (RANKL), tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), and the receptor RANK in proliferative diabetic retinopathy (PDR).

MATERIALS AND METHODS

Vitreous samples from PDR and nondiabetic control patients and epiretinal membranes from PDR patients were studied by enzyme-linked immunosorbent assay, immunohistochemistry, and Western blot analysis.

RESULTS

Vascular endothelial growth factor, OPG, and soluble RANK levels in vitreous samples from PDR patients were significantly higher than that in nondiabetic controls. Soluble TRAIL levels were significantly lower in PDR patients than that in nondiabetic control, whereas soluble RANKL levels did not differ significantly. RANKL, RANK, and TRAIL were expressed in vascular endothelial cells, myofibroblasts, and CD45-expressing leukocytes in PDR epiretinal membranes.

CONCLUSIONS

Dysregulated expression of OPG/RANKL/RANK pathway and TRAIL might be related to inflammation and angiogenesis in PDR.

Antibody-Mediated Inhibition of Tspan12 Ameliorates Vasoproliferative Retinopathy Through Suppression of β-Catenin Signaling

Background:

Anti-angiogenic biologicals represent an important concept for the treatment of vasoproliferative diseases. However, the need for continued treatment, the presence of nonresponders, and the risk of long-term side effects limit the success of existing therapeutic agents. Although Tspan12 has been shown to regulate retinal vascular development, nothing is known about its involvement in neovascular disease and its potential as a novel therapeutic target for the treatment of vasoproliferative diseases.

Methods:

Rodent models of retinal neovascular disease, including the mouse model of oxygen-induced retinopathy and the very low density lipoprotein receptor knockout mouse model were analyzed for Tspan/β-catenin regulation. Screening of a phage display of a human combinatorial antibody (Ab) library was used for the development of a high-affinity Ab against Tspan12. Therapeutic effects of the newly developed Ab on vascular endothelial cells were tested in vitro and in vivo in the oxygen-induced retinopathy and very low density lipoprotein receptor knockout mouse model.

Results:

The newly developed anti-Tspan12 Ab exhibited potent inhibitory effects on endothelial cell migration and tube formation. Mechanistic studies confirmed that the Ab inhibited the interaction between Tspan12 and Frizzled-4 and effectively modulates β-catenin levels and target genes in vascular endothelial cells. Tspan12/β-catenin signaling was activated in response to acute and chronic stress in the oxygen-induced retinopathy and very low density lipoprotein receptor mouse model of proliferative retinopathy. Intravitreal application of the Ab showed significant therapeutic effects in both models without inducing negative side effects on retina function. Moreover, combined intravitreal injection of the Ab with a known vascular endothelial growth factor inhibitor, Aflibercept, resulted in significant enhancement of the therapeutic efficacy of each monotherapy. Combination therapy with the Tspan12 blocking antibody can be used to reduce anti-vascular endothelial growth factor doses, thus decreasing the risk of long-term off-target effects.

Conclusions:

Tspan12/β-catenin signaling is critical for the progression of vasoproliferative disease. The newly developed anti-Tspan12 antibody has therapeutic effects in vasoproliferative retinopathy and can enhance the potency of existing anti- vascular endothelial growth factor agents.

Diabetic complications in the cornea

Diabetic corneal alterations, such as delayed epithelial wound healing, edema, recurrent erosions, neuropathy/loss of sensitivity, and tear film changes are frequent but underdiagnosed complications of both type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes mellitus. The disease affects corneal epithelium, corneal nerves, tear film, and to a lesser extent, endothelium, and also conjunctiva. These abnormalities may appear or become exacerbated following trauma, as well as various surgeries including retinal, cataract or refractive. The focus of the review is on mechanisms of diabetic corneal abnormalities, available animal, tissue and organ culture models, and emerging treatments. Changes of basement membrane structure and wound healing rates, the role of various proteinases, advanced glycation end products (AGEs), abnormal growth and motility factors (including opioid, epidermal, and hepatocyte growth factors) are analyzed. Experimental therapeutics under development, including topical naltrexone, insulin, inhibitors of aldose reductase, and AGEs, as well as emerging gene and cell therapies are discussed in detail.

Engineered ligand-based VEGFR antagonists with increased receptor binding affinity more effectively inhibit angiogenesis

Pathologic angiogenesis is mediated by the coordinated action of the vascular endothelial growth factor (VEGF)/vascular endothelial growth factor receptor 2 (VEGFR2) signaling axis, along with crosstalk contributed by other receptors, notably α_vβ₃ integrin. We build on earlier work demonstrating that point mutations can be introduced into the homodimeric VEGF ligand to convert it into an antagonist through disruption of binding to one copy of VEGFR2. This inhibitor has limited potency, however, due to loss of avidity effects from bivalent VEGFR2 binding. Here, we used yeast surface display to engineer a variant with VEGFR2 binding affinity approximately 40‐fold higher than the parental antagonist, and 14‐fold higher than the natural bivalent VEGF ligand. Increased VEGFR2 binding affinity correlated with the ability to more effectively inhibit VEGF‐mediated signaling, both in vitro and in vivo, as measured using VEGFR2 phosphorylation and Matrigel implantation assays. High affinity mutations found in this variant were then incorporated into a dual‐specific antagonist that we previously designed to simultaneously bind to and inhibit VEGFR2 and α_vβ₃ integrin. The resulting dual‐specific protein bound to human and murine endothelial cells with relative affinities of 120 ± 10 pM and 360 ± 50 pM, respectively, which is at least 30‐fold tighter than wild‐type VEGF (3.8 ± 0.5 nM). Finally, we demonstrated that this engineered high‐affinity dual‐specific protein could inhibit angiogenesis in a murine corneal neovascularization model. Taken together, these data indicate that protein engineering strategies can be combined to generate unique antiangiogenic candidates for further clinical development.

Production of heparin and λ-carrageenan anti-heparanase derivatives using a combination of physicochemical depolymerization and glycol splitting

Strongly associated with tumor angiogenesis and metastasis, the enzyme heparanase is an endo-β-d-glucuronidase which is overexpressed in the tumor microenvironment. Its inhibition could be one of the most promising anti-angiogenic approaches to date. Although heparin is known as a good heparanase inhibitor, it also possesses major anticoagulant properties that may be incompatible with its use as an anti-angiogenic agent, hence the considerable interest for other sources of sulfated polysaccharides. Recent investigations point to λ-carrageenans, highly sulfated galactans with a tremendous potential that are found in red algae. This study describes the production of low-molecular-weight (LMW) heparins and λ-carrageenans, using a combination of glycol splitting and ultrasonically-assisted radical hydrolysis using hydrogen-peroxide. The structural characteristics, as well as the anticoagulant and antiheparanase activities of the resulting products were assessed. The best candidate was a LMW glycol-split λ-carrageenan that displayed major anti-heparanase properties, with an IC₅₀ of 7.32ng/mL and a close-to-zero anticoagulant activity.

A Dual-Modality System for Both Multi-Color Ultrasound-Switchable Fluorescence and Ultrasound Imaging

Simultaneous imaging of multiple targets (SIMT) in opaque biological tissues is an important goal for molecular imaging in the future. Multi-color fluorescence imaging in deep tissues is a promising technology to reach this goal. In this work, we developed a dual-modality imaging system by combining our recently developed ultrasound-switchable fluorescence (USF) imaging technology with the conventional ultrasound (US) B-mode imaging. This dual-modality system can simultaneously image tissue acoustic structure information and multi-color fluorophores in centimeter-deep tissue with comparable spatial resolutions. To conduct USF imaging on the same plane (i.e., x-z plane) as US imaging, we adopted two 90°-crossed ultrasound transducers with an overlapped focal region, while the US transducer (the third one) was positioned at the center of these two USF transducers. Thus, the axial resolution of USF is close to the lateral resolution, which allows a point-by-point USF scanning on the same plane as the US imaging. Both multi-color USF and ultrasound imaging of a tissue phantom were demonstrated.

Natural products against cancer angiogenesis

The process of angiogenesis is quite well-known nowadays. Some medicines and extracts affecting this process are already used routinely in supporting the conventional treatment of many diseases that are considered angiogenic such as cancer. However, we must be aware that the area of currently used drugs of this type is much narrower than the theoretical possibilities existing in therapeutic angiogenesis. Plant substances are a large and diverse group of compounds that are found naturally in fruits, vegetables, spices, and medicinal plants. They also have different anticancer properties. The aim of this literature review article is to present the current state of knowledge concerning the molecular targets of tumor angiogenesis and the active substances (polyphenols, alkaloids, phytohormones, carbohydrates, and terpenes) derived from natural sources, whose activity against cancer angiogenesis has been confirmed.

Construction of a disulfide-stabilized diabody against fibroblast growth factor-2 and the inhibition activity in targeting breast cancer

Fibroblast growth factor‐2 (FGF‐2) is one of the most important angiogenic factors to promote tumor growth, progression and metastasis. Neutralizing antibodies against FGF‐2 may suppress the growth of tumor cells by blocking the FGF‐2 signaling pathway. In this study, a disulfide‐stabilized diabody (ds‐Diabody) that specifically targets FGF‐2 was designed. Compared to its parent antibody, the introduction of disulphide bonds in the diabody could significantly increase the stability of ds‐Diabody and maintain its antigen binding activity. The ds‐Diabody against FGF‐2 could effectively inhibit the tube formation and migration of vascular endothelial cells and block the proliferation and invasion of human breast cancer cells. In the mouse model of breast cancer xenograft tumors, the ds‐Diabody against FGF‐2 could significantly inhibit the growth of tumor cells. Moreover, the densities of microvessels stained with CD31 and lymphatic vessels stained with LYVE1 in tumors showed a significant decrease following treatment with the ds‐Diabody against FGF‐2. Our data indicated that the ds‐Diabody against FGF‐2 could inhibit tumor angiogenesis, lymphangiogenesis and tumor growth.

Tunable release of chemotherapeutic and vascular disrupting agents from injectable fiber fragments potentiates combination chemotherapy

Cancer progression and metastasis relies much on vasculature networks in tumor microenvironment, and the combination treatment with chemotherapeutic drugs and vascular disrupting agents represents apparent clinical benefits. In the current study, fiber fragments with loadings of hydroxycamptothecin (HCPT) or combretastatin A-4 (CA4) were proposed for tumor inhibition and blood vessel disruption after local administration in tumors. To address challenges in balancing the disruption of tumor vessels and intratumoral uptake of chemotherapeutic agents, this study is focus on release tuning of HCPT and CA4 from the fiber fragment mixtures. Hydroxypropyl-β-cyclodextrin (HPCD) was blended at ratios from 0 to 10% into CA4-loaded fiber fragments (Fc) to modulate CA4 release durations from 0.5 to 24days, and HCPT-loaded fiber fragments (Fh) indicated a sustained release for over 35days. In vitro cytotoxicity tests indicated a sequential inhibition on the endothelial and tumor cell growth, and the growth inhibition of tumor cells was more significant after treatment with mixtures of Fh and Fc containing 2% HPCD (Fc2) than that of other mixtures. In an orthotopic breast tumor model, compared with those of free CA4, or Fc with a fast or slow release of CA4, Fh/Fc mixtures with CA4 release durations from 2 to 12days indicated a lower tumor growth rate, a prolonged animal survival, a lower vessel density in tumors, and a less significant tumor metastasis. In addition, the tumor cell proliferation rate, hypoxia-inducible factor-1α expression within tumors, and the number of surface metastatic nodules in lungs were significantly lower after treatment with Fh/Fc2 mixtures with a CA4 release duration of 5days than those of other mixtures. It demonstrates the advantages of fiber fragment mixtures in independently modulating the release of multiple drugs and the essential role of release tuning of chemotherapeutic drugs and vascular disrupting agents in improving the therapeutic efficacy.

Lecithin-Bound Iodine Prevents Disruption of Tight Junctions of Retinal Pigment Epithelial Cells under Hypoxic Stress

Aim. We investigated whether lecithin-bound iodine (LBI) can protect the integrity of tight junctions of retinal pigment epithelial cells from hypoxia. Method. Cultured human retinal pigment epithelial (ARPE-19) cells were pretreated with LBI. To mimic hypoxic conditions, cells were incubated with CoCl2. We compared the integrity of the tight junctions (TJs) of control to cells with either LBI alone, CoCl2 alone, or LBI + CoCl2. The levels of cytokines in the conditioned media were also determined. Results. Significant decrease in the zonula occludens-1 (ZO-1) intensity in the CoCl2 group compared to the control (5787.7 ± 4126.4 in CoCl2 group versus 29244.6 ± 2981.2 in control; average ± standard deviation). But the decrease was not significant in the LBI + CoCl2 (27189.0 ± 11231.1). The levels of monocyte chemoattractant protein-1 (MCP-1) and Chemokine (C-C Motif) Ligand 11 (CCL-11) were significantly higher in the CoCl2 than in the control (340.8 ± 43.3 versus 279.7 ± 68.3 pg/mL for MCP-1, and 15.2 ± 12.9 versus 12.5 ± 6.1 pg/mL for CCL-11. With LBI pretreatment, the levels of both cytokines were decreased to 182.6 ± 23.8 (MCP-1) and 5.46 ± 1.9 pg/mL for CCL-11). Blockade of MCP-1 or CCL-11 also shows similar result representing TJ protection from hypoxic stress. Conclusions. LBI results in a protective action from hypoxia.

Dual blockade of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2) exhibits potent anti-angiogenic effects

Both vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF or FGF-2) are potent pro-angiogenic factors and play a critical role in cancer development and progression. Clinical anti-VEGF therapy trials had a major challenge due to upregulated expression of other pro-angiogenic factor, like FGF-2. This study developed a novel chimeric decoy receptor VF-Trap fusion protein to simultaneously block activity of both VEGF and FGF pathways in order to achieve an additive or synergistic anti-tumor effect. Our in vitro data showed that VF-Trap potently blocked proliferation and migration of both VEGF- and FGF-2-induced vascular endothelial cells. In animal models, treatment of xenograft tumors with VF-Trap resulted in significant inhibition of tumor growth compared to blockage of the single molecule, like VEGF or FGF blocker. In addition, VF-Trap was also more potent in inhibition of ocular angiogenesis in a mouse oxygen-induced retinopathy (OIR) model. These data demonstrated the potent anti-angiogenic effects of this novel VF-Trap fusion protein on blockage of VEGF and FGF-2 activity in vitro and in animal models. Further study will assess its effects in clinic as a therapeutic agent for angiogenesis-related disorders, such as cancer and ocular vascular diseases.

Axitinib inhibits retinal and choroidal neovascularization in in vitro and in vivo models

Age-related Macular Degeneration (AMD) is the leading cause of visual impairment and blindness in the elderly in developed countries. Neovascular/exudative (wet) AMD is the aggressive form of AMD and can involve choroidal neovascularization and vascular leakage. Anti-vascular endothelial growth factor (anti-VEGF) medications have significantly improved treatment of wet-AMD. However, only approximately 40% of patients obtain full benefit from anti-VEGF therapy and the medications are given by intravitreal injection. Axitinib, a small molecule multi-receptor tyrosine kinase inhibitor used for the treatment of advanced renal cell carcinoma, is taken orally and inhibits VEGF activity by blocking VEGF receptors. Axitinib also has the advantage of blocking platelet derived growth factor (PDGF) receptors which play a role in neovascularization. Using in vitro human retinal microvascular endothelial cells (HRMVECs), human brain vascular pericytes (HBVRs), 3D co-culture vessel sprout assay, and in vivo laser induced rat choroidal neovascularization (CNV) models, the effect of axitinib on neovascularization was evaluated. Axitinib inhibited neovascularization better than anti-VEGF and/or anti-hPDGF-B mAb in the in vitro models demonstrating that combined inhibition of both VEGF and PDGF pathways may be synergistic in treating wet-AMD. Additionally, axitinib showed good efficacy at a low dose (0.875 mg/day) in laser-induced CNV model in rats. In conclusion our data shows that axitinib, an inhibitor of VEGF and PDGF-B pathways may be useful in ameliorating wet-AMD therapy.

Alternative splicing creates two new architectures for human tyrosyl-tRNA synthetase

Many human tRNA synthetases evolved alternative functions outside of protein synthesis. These functions are associated with over 200 splice variants (SVs), most of which are catalytic nulls that engender new biology. While known to regulate non-translational activities, little is known about structures resulting from natural internal ablations of any protein. Here, we report analysis of two closely related, internally deleted, SVs of homodimeric human tyrosyl-tRNA synthetase (TyrRS). In spite of both variants ablating a portion of the catalytic core and dimer-interface contacts of native TyrRS, each folded into a distinct stable structure. Biochemical and nuclear magnetic resonance (NMR) analysis showed that the internal deletion of TyrRSΔE2–4 SV gave an alternative, neomorphic dimer interface ‘orthogonal’ to that of native TyrRS. In contrast, the internal C-terminal splice site of TyrRSΔE2–3 prevented either dimerization interface from forming, and yielded a predominantly monomeric protein. Unlike ubiquitous TyrRS, the neomorphs showed clear tissue preferences, which were distinct from each other. The results demonstrate a sophisticated structural plasticity of a human tRNA synthetase for architectural reorganizations that are preferentially elicited in specific tissues.

Differential expression of vascular endothelial growth factor-a isoforms in neovascular age-related macular degeneration

PURPOSE

To investigate the role of vascular endothelial growth factor-A (VEGF-A) isoforms in neovascular age-related macular degeneration.

METHODS

Choroidal neovascular membranes (CNV) were excised in 24 patients, 8 of them underwent previous photodynamic therapy. All procedures were performed before anti-VEGF therapies were implemented in Germany. Normal human donor eyes served as controls. Messenger RNA expression of total VEGF-A and VEGF-A isoforms was measured.

RESULTS

Vascular endothelial growth factor-A121 is the most abundant isoform in CNV and control tissues. In controls, VEGF-A121 is lowest in neural retina and highest in choroids. For total VEGF-A and VEGF-A165, this is vice versa. VEGF-A165 and VEGF-A189 are significantly higher in CNV than in control choroids, the opposite is found for VEGF-A121. After photodynamic therapy, total VEGF-A and VEGF-A121 are increased, VEGF-A165 and VEGF-A189 are decreased. Age-dependently, there is an increase in VEGF-A165 and a decrease in VEGF-A121.

CONCLUSION

Vascular endothelial growth factor-A isoforms are differentially distributed, suggesting that tissue-specific regulation of various isoforms is physiologically important. The disruption of this homeostasis in CNV membranes may be significant in the onset and progression of neovascular age-related macular degeneration. Our findings support the dominant role of VEGF-A121 in neovascular age-related macular degeneration but hint that VEGF-A165 may have an equivalent role in other neovascular retinal pathology.

Neurovascular crosstalk between interneurons and capillaries is required for vision

Functional interactions between neurons, vasculature, and glia within neurovascular units are critical for maintenance of the retina and other CNS tissues. For example, the architecture of the neurosensory retina is a highly organized structure with alternating layers of neurons and blood vessels that match the metabolic demand of neuronal activity with an appropriate supply of oxygen within perfused blood. Here, using murine genetic models and cell ablation strategies, we have demonstrated that a subset of retinal interneurons, the amacrine and horizontal cells, form neurovascular units with capillaries in 2 of the 3 retinal vascular plexuses. Moreover, we determined that these cells are required for generating and maintaining the intraretinal vasculature through precise regulation of hypoxia-inducible and proangiogenic factors, and that amacrine and horizontal cell dysfunction induces alterations to the intraretinal vasculature and substantial visual deficits. These findings demonstrate that specific retinal interneurons and the intraretinal vasculature are highly interdependent, and loss of either or both elicits profound effects on photoreceptor survival and function.

The emerging quest for the optimal angiostatic combination therapy

Angiostatic therapies are now routinely embedded in the daily clinical management of cancer. Although these agents clearly benefit patient survival rates, the effect is only moderate with sometimes considerable side effects. A major cause of failure in this respect is the induction of resistance and tolerability against these drugs. Most angiostatic drugs are tyrosine kinase inhibitors that aim to inhibit or neutralize the activity of tumour-produced growth factors. Frustrating the tumour cells in this way results in genetic adaptations in the cells, turning them into mutants that are dependent on other growth mechanisms. It may therefore be necessary to shift to another class of drugs that directly target the tumour vasculature. It is evident that improvement of future angiogenesis inhibitors can only arise from two efforts. First, through the identification of better targets, preferably specifically expressed in the tumour vasculature. Secondly, through the development of combination therapies. The present review highlights the current efforts and challenges in trying to develop effective angiostatic combination therapies.

Antimetastasis and antitumor efficacy promoted by sequential release of vascular disrupting and chemotherapeutic agents from electrospun fibers

The vasculature in tumor microenvironment plays important roles in the tumor growth and metastasis, and the combination of vascular disrupting agents with chemotherapeutic drugs should be effective in inhibiting tumor progression. But the dosing schedules are essential to achieve a balance between vascular collapse and intratumoral uptake of chemotherapeutic agents. In the current study, emulsion and blend electrospinning were used to create compartmental fibers accommodating both combretastatin A-4 (CA4) and hydroxycamptothecin (HCPT). The release durations of CA4 and HCPT were modulated through the structure of fibers for dual drug loadings and the inoculation of 2-hydroxypropyl-β-cyclodextrin in fiber matrices. Under a noncontact cell coculture in Transwell, the sequential release of CA4 and HCPT indicated a sequential killing of endothelial and tumor cells. In an orthotopic breast tumor model, all the CA4/HCPT-loaded fibers showed superior antitumor efficacy and higher survival rate than fibers with loaded individual drug. Compared with fibrous mats with infiltrated free CA4 and fibers with extended release of CA4 for over 30 days, fibers with sustained release of CA4 for 3-7 days from CA4/HCPT-loaded fibers resulted in the most significant antitumor efficacy, tumor vasculature destruction, and the least tumor metastasis to lungs. A judicious selection of CA4 release durations in the combination therapy should be essential to enhance the tumor suppression efficacy and antimetastasis activity.

tRNA synthetase: tRNA aminoacylation and beyond

The aminoacyl-tRNA synthetases are prominently known for their classic function in the first step of protein synthesis, where they bear the responsibility of setting the genetic code. Each enzyme is exquisitely adapted to covalently link a single standard amino acid to its cognate set of tRNA isoacceptors. These ancient enzymes have evolved idiosyncratically to host alternate activities that go far beyond their aminoacylation role and impact a wide range of other metabolic pathways and cell signaling processes. The family of aminoacyl-tRNA synthetases has also been suggested as a remarkable scaffold to incorporate new domains that would drive evolution and the emergence of new organisms with more complex function. Because they are essential, the tRNA synthetases have served as pharmaceutical targets for drug and antibiotic development. The recent unfolding of novel important functions for this family of proteins offers new and promising pathways for therapeutic development to treat diverse human diseases.

Livistona chinensis seeds inhibit hepatocellular carcinoma angiogenesis in vivo via suppression of the Notch pathway

Livistona chinensis seeds have been used for centuries to clinically treat various types of cancer. Our published data suggest that Livistona chinensis seeds are able to inhibit hepatocellular carcinoma (HCC) growth in vitro and in vivo via promotion of mitochondrial-dependent apoptosis. To further elucidate the molecular mechanisms of its antitumor activity, in the present study, we used an HCC xenograft mouse model to evaluate the effect of an ethanol extract of Livistona chinensis seeds (EELC) on tumor angiogenesis and on the activation of the Notch pathway. Intratumoral microvessel density (MVD) in HCC xenograft mouse tumors was evaluated via immunohistochemical (IHC) staining for CD31. The mRNA and protein expression of vascular endothelial growth factor A (VEGF-A), VEGFR-2, Notch, Dll4 and Jagged1 was evaluated using RT-PCR and IHC, respectively. We found that EELC profoundly reduced MVD in the HCC mouse tumors, demonstrating the in vivo inhibitory effect of EELC on tumor angiogenesis. In addition, EELC treatment reduced the expression of VEGF-A and VEGFR-2 in tumor tissues. Furthermore, EELC treatment inhibited the expression of Notch, Dll4 and Jagged1. Our findings suggest that Livistona chinensis seeds inhibit tumor angiogenesis through suppression of the Notch pathway.

Ras pathway inhibition prevents neovascularization by repressing endothelial cell sprouting

Vascular networks develop from a growing vascular front that responds to VEGF and other guidance cues. Angiogenesis is required for normal tissue function, but, under conditions of stress, inappropriate vascularization can lead to disease. Therefore, inhibition of angiogenic sprouting may prevent neovascularization in patients with blinding neovascular eye diseases, including macular degeneration. VEGF antagonists have therapeutic benefits but also can elicit off-target effects. Here, we found that the Ras pathway, which functions downstream of a wide range of cytokines including VEGF, is active in the growing vascular front of developing and pathological vascular networks. The endogenous Ras inhibitor p120RasGAP was expressed predominately in quiescent VEGF-insensitive endothelial cells and was ectopically downregulated in multiple neovascular models. MicroRNA-132 negatively regulated p120RasGAP expression. Experimental delivery of α-miR-132 to developing mouse eyes disrupted tip cell Ras activity and prevented angiogenic sprouting. This strategy prevented ocular neovascularization in multiple rodent models even more potently than the VEGF antagonist, VEGF-trap. Targeting microRNA-132 as a therapeutic strategy may prove useful for treating multiple neovascular diseases of the eye and for preventing vision loss regardless of the neovascular stimulus.

The mouse retina in 3D: quantification of vascular growth and remodeling

The mouse retina has become a prominent model for studying angiogenesis. The easy access and well-known developmental progression have significantly propelled our ability to examine and manipulate blood vessels in vivo. Nonetheless, most studies have restricted their evaluations to the superficial plexus (an upper vascular layer in contact with the vitreous). Here we present experimental data and quantification for the developmental progression of the full retina including the intermediate and deeper plexus that sprouts from the superficial layer. We analyze the origin and advancement of vertical sprouting and present the progression of vascular perfusion within the tissue. Furthermore, we introduce the use of Minkowsky functionals to quantify remodeling in the superficial and deeper plexus. The work expands information on the retina towards a 3D structure. This is of particular interest, as recent data have demonstrated differential effects of gene deletion on the upper and deeper plexus, highlighting the concept of distinct operational pathways during sprouting angiogenesis.

Expression of SIRT1 in choroidal neovascular membranes

PURPOSE

SIRT1 is a deacetylase that has been shown to be instrumental in embryonic and pathologic vascular formation. The purpose of this study was to evaluate the potential role of SIRT1 in the pathogenesis of choroidal neovascularization in age-related macular degeneration.

METHODS

The expression of SIRT1 was assessed via immunohistochemistry in nine excised human choroidal neovascularization membranes and seven non-age-related macular degeneration donor eyes. Enzyme-linked immunosorbent assay-based angiogenesis arrays were used to assess the potential of an SIRT1 inhibitor, nicotinamide, to reduce secretion of 10 unique proangiogenic cytokines from retinal pigment epithelial cells.

RESULTS

SIRT1 was expressed more frequently in choroidal neovascularization membranes than donor eyes about vascular endothelial cells (78 vs. 29% positive cases) and retinal pigment epithelial cells (57 vs. 14% positive cases). SIRT1 inhibition in retinal pigment epithelial cells correlated with significantly decreased secretion of three potent proangiogenic cytokines: angiogenin, platelet-derived growth factor BB, and vascular endothelial growth factor A.

CONCLUSION

SIRT1 levels appear elevated in human choroidal neovascularization membranes compared with control eyes. Moreover, inhibition of SIRT1 activity is correlated with decreased secretion of potent proangiogenic cytokines. Collectively, these data support a potential role for SIRT1 in the pathogenesis of neovascular age-related macular degeneration.

EMMPRIN promotes angiogenesis, proliferation, invasion and resistance to sunitinib in renal cell carcinoma, and its level predicts patient outcome

PURPOSE

Extracellular matrix metalloproteinase inducer (EMMPRIN) has been reported to play crucial roles, including in angiogenesis, in several carcinomas. However, the correlation between EMMPRIN levels and angiogenesis expression profile has not been reported, and the role of EMMPRIN in renal cell carcinoma (RCC) is unclear. In the present study, we evaluated the association of EMMPRIN with angiogenesis, its value in prognosis, and its roles in RCC.

EXPERIMENTAL DESIGN

EMMPRIN expression was examined in 50 RCC patients treated with radical nephrectomy. Angiogenesis, proliferation, and invasion activity were evaluated using EMMPRIN knockdown RCC cell lines. The size of EMMPRIN-overexpressing xenografts was measured and the degree of angiogenesis was quantified. EMMPRIN expression was evaluated in RCC patients who received sunitinib therapy and in sunitinib-resistant cells. Further, the relation between EMMPRIN expression and sensitivity to sunitinib was examined.

RESULTS

EMMPRIN score was significantly associated with clinicopathological parameters in RCC patients, as well as being significantly correlated with microvessel area (MVA) in immature vessels and with prognosis. Down-regulation of EMMPRIN by siRNA led to decreased VEGF and bFGF expression, cell proliferation, and invasive potential. EMMPRIN over-expressing xenografts showed accelerated growth and MVA of immature vessels. EMMPRIN expression was significantly increased in patients who received sunitinib therapy as well as in sunitinib-resistant 786-O cells (786-suni). EMMPRIN-overexpressing RCC cells were resistant to sunitinib.

CONCLUSION

Our findings indicate that high expression of EMMPRIN in RCC plays important roles in tumor progression and sunitinib resistance. Therefore, EMMPRIN could be a novel target for the treatment of RCC.

Compensation: a contemporary regulatory machinery in cardiovascular diseases?

Both clinical and experimental findings at the molecular, cellular, tissue, organ and systematic levels have depicted the presence of a contemporary regulatory machinery namely compensation in various forms of cardiovascular diseases. Compensation is believed to be present and regulated within the scope of a biological entity and represents the initiation of dyshomeostasis. Compensation can be identified in multiple categories and organs in cardiovascular diseases at multiple levels. The capacity to reduce the unfavorable pathological compensation may be a criterion to evaluate the therapeutic effectiveness for cardiovascular diseases. This mini-review tries to take compensation into consideration in the understanding of onset and progression of cardiovascular diseases in particular, and thus, better or optimal therapeutic approaches may be achieved for the prevention and management of cardiovascular diseases.