Distribution of growth factors in subfoveal neovascular membranes in age-related macular degeneration and presumed ocular histoplasmosis syndrome

Exploring Current Molecular Targets in the Treatment of Neovascular Age-Related Macular Degeneration toward the Perspective of Long-Term Agents

Long-lasting anti-vascular endothelial growth factor (anti-VEGF) agents have become an option to reduce treatment frequency, with ongoing research exploring optimal responses and safety profiles. This review delves into molecular targets, pharmacological aspects, and strategies for achieving effective and enduring disease control in neovascular age-related macular degeneration (AMD). The molecular pathways involved in macular neovascularization, including angiogenesis and arteriogenesis, are explored. VEGF, PlGF, Ang-1, and Ang-2 play crucial roles in regulating angiogenesis, influencing vessel growth, maturation, and stability. The complex interplay of these factors, along with growth factors like TGFβ and bFGF, contributes to the pathogenesis of neovascular membranes. Current anti-VEGF therapies, including bevacizumab, ranibizumab, aflibercept, brolucizumab, and faricimab, are discussed with a focus on their pharmacokinetics and clinical applications. Strategies to achieve sustained disease control in AMD involve smaller molecules, increased drug dosages, and novel formulations. This narrative review provides a comprehensive overview of the molecular targets and pharmacological aspects of neovascular AMD treatment.

Induced retinal pigment epithelial cells with anti-epithelial-to-mesenchymal transition ability delay retinal degeneration

The hostile microenvironment of the retina in patients with age-related macular degeneration (AMD) may trigger epithelial-to-mesenchymal transition (EMT) of grafted retinal pigment epithelial (RPE) cells, thus attenuating the therapeutic outcome. Here, we transformed human dedifferentiated induced pluripotent stem cell-derived RPE (iPSC-RPE) cells into induced RPE (iRPE) cells using a cocktail of four transcription factors (TFs)—CRX, MITF-A, NR2E1, and C-MYC. These critical TFs maintained the epithelial property of iRPE cells by regulating the expression of bmp7, forkhead box f2, lin7a, and pard6b, and conferred resistance to TGF-β-induced EMT in iRPE cells by targeting ppm1a. The iRPE cells with Tet-on system-regulated c-myc expression exhibited EMT resistance and better therapeutic function compared with iPSC-RPE cells in rat AMD model. Our study demonstrates that endowing RPE cells with anti-EMT property avoids the risk of EMT after cells are grafted into the subretinal space, and it may provide a suitable candidate for AMD treatment.

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CRX, MITF-A, NR2E1, and C-MYC transform De-iPSC-RPE cells into iRPE cells

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iRPE cells have resistance to TGF-β-induced EMT

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BMP7, FOXF2, LIN7A, PARD6B, and PPM1A mediate the functions of TFs in iRPE cells

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iRPE cells have better retinal protective function than iPSC-RPE cells

Direct conversion of human umbilical cord mesenchymal stem cells into retinal pigment epithelial cells for treatment of retinal degeneration

Age-related macular degeneration (AMD) is a major vision-threatening disease. Although mesenchymal stem cells (MSCs) exhibit beneficial neural protective effects, their limited differentiation capacity in vivo attenuates their therapeutic function. Therefore, the differentiation of MSCs into retinal pigment epithelial (RPE) cells in vitro and their subsequent transplantation into the subretinal space is expected to improve the outcome of cell therapy. Here, we transdifferentiated human umbilical cord MSCs (hUCMSCs) into induced RPE (iRPE) cells using a cocktail of five transcription factors (TFs): CRX, NR2E1, C-MYC, LHX2, and SIX6. iRPE cells exhibited RPE specific properties, including phagocytic ability, epithelial polarity, and gene expression profile. In addition, high expression of PTPN13 in iRPE cells endows them with an epithelial-to-mesenchymal transition (EMT)-resistant capacity through dephosphorylating syntenin1, and subsequently promoting the internalization and degradation of transforming growth factor-β receptors. After grafting into the subretinal space of the sodium iodate-induced rat AMD model, iRPE cells demonstrated a better therapeutic function than hUCMSCs. These results suggest that hUCMSC-derived iRPE cells may be promising candidates to reverse AMD pathophysiology.

[Current view on the issue of insufficient effectiveness of anti-VEGF therapy for age-related macular degeneration]

Due to the significant medical and social importance of neovascular (wet) age-related macular degeneration (wAMD), increasing the effectiveness of anti-VEGF therapy used to treat this disease is one of the high-priority problems in modern retinology. This article focuses on pathobiological aspects and clinical manifestations of incomplete responses to anti-VEGF therapy of wAMD, considers the proposed ways to improve the terminology and classification of responses to therapy, as well as the assessment of its correctness and effectiveness of the treatment. It also discusses the available ways to optimize anti-VEGF therapy and define the criteria of its termination in cases when the treatment proves to be futile.

Transcriptomic analysis of choroidal neovascularization reveals dysregulation of immune and fibrosis pathways that are attenuated by a novel anti-fibrotic treatment

Neovascular AMD (nAMD) leads to vision loss and is a leading cause of visual impairment in the industrialised world. Current treatments that target blood vessel growth have not been able to treat subretinal fibrosis and nAMD patients continue to lose vision. The molecular mechanisms involved in the development of fibrotic lesions in nAMD are not well understood. The aim of this study was to further understand subretinal fibrosis in the laser photocoagulation model of choroidal neovascularization (CNV) by studying the whole transcriptome of the RPE/choroid following CNV and the application of an anti-fibrotic following CNV. Seven days after laser induced CNV, RPE and choroid tissue was separated and underwent RNAseq. Differential expression analysis and pathway analysis revealed an over representation of immune signalling and fibrotic associated pathways in CNV compared to control RPE/choroid tissue. Comparisons between the mouse CNV model to human CNV revealed an overlap in upregulated expression for immune genes (Ccl2, Ccl8 and Cxcl9) and extracellular matrix remodeling genes (Comp, Lrcc15, Fndc1 and Thbs2). Comparisons between the CNV model and other fibrosis models showed an overlap of over 60% of genes upregulated in either lung or kidney mouse models of fibrosis. Treatment of CNV using a novel cinnamoyl anthranilate anti-fibrotic (OCX063) in the laser induced CNV model was selected as this class of drugs have previously been shown to target fibrosis. CNV lesion leakage and fibrosis was found to be reduced using OCX063 and gene expression of genes within the TGF-beta signalling pathway. Our findings show the presence of fibrosis gene expression pathways present in the laser induced CNV mouse model and that anti-fibrotic treatments offer the potential to reduce subretinal fibrosis in AMD.

Inhibition of hypoxia-inducible factor-1 by Salidroside in an in vitro model of choroidal neovascularization

PURPOSE

As a characteristic of age-related macular degeneration (AMD), choroidal neovascularization (CNV) causes severe vision loss. The current treatment has limited efficacy. This study was to investigate effects of Salidroside against CNV and explore its underlying mechanisms.

METHODS

RF/6A cells were treated with 200 mM cobalt chloride (CoCl₂) for 6 hr to mimic hypoxic condition. Cells were then treated with Salidroside at 10, 30 and 100 µM for 24 hr. Cells treated with DMSO were used as negative control. The cell proliferation was assessed using 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium-bromid assay. The tube formation was investigated on Matrigel. The cell migration was measured by a Transwell assay. RT-qPCR was used to detect the gene expression. Immuohistochemistry and western blot were used to detect the expression of proteins.

RESULTS

Salidroside significantly inhibited the cell migration and tube formation activity of RF/6A cells under hypoxia. Moreover, Salidroside reduced the expression levels of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1 (HIF-1) in RF/6A cells.

CONCLUSIONS

Our data suggested that Salidroside could be a potential novel therapeutic agent against CNV.

Incomplete response to Anti-VEGF therapy in neovascular AMD: Exploring disease mechanisms and therapeutic opportunities

Intravitreal anti-vascular endothelial growth factor (VEGF) drugs have revolutionized the treatment of neovascular age-related macular degeneration (NVAMD). However, many patients suffer from incomplete response to anti-VEGF therapy (IRT), which is defined as (1) persistent (plasma) fluid exudation; (2) unresolved or new hemorrhage; (3) progressive lesion fibrosis; and/or (4) suboptimal vision recovery. The first three of these collectively comprise the problem of persistent disease activity (PDA) in spite of anti-VEGF therapy. Meanwhile, the problem of suboptimal vision recovery (SVR) is defined as a failure to achieve excellent functional visual acuity of 20/40 or better in spite of sufficient anti-VEGF treatment. Thus, incomplete response to anti-VEGF therapy, and specifically PDA and SVR, represent significant clinical unmet needs. In this review, we will explore PDA and SVR in NVAMD, characterizing the clinical manifestations and exploring the pathobiology of each. We will demonstrate that PDA occurs most frequently in NVAMD patients who develop high-flow CNV lesions with arteriolarization, in contrast to patients with capillary CNV who are highly responsive to anti-VEGF therapy. We will review investigations of experimental CNV and demonstrate that both types of CNV can be modeled in mice. We will present and consider a provocative hypothesis: formation of arteriolar CNV occurs via a distinct pathobiology, termed neovascular remodeling (NVR), wherein blood-derived macrophages infiltrate the incipient CNV lesion, recruit bone marrow-derived mesenchymal precursor cells (MPCs) from the circulation, and activate MPCs to become vascular smooth muscle cells (VSMCs) and myofibroblasts, driving the development of high-flow CNV with arteriolarization and perivascular fibrosis. In considering SVR, we will discuss the concept that limited or poor vision in spite of anti-VEGF may not be caused simply by photoreceptor degeneration but instead may be associated with photoreceptor synaptic dysfunction in the neurosensory retina overlying CNV, triggered by infiltrating blood-derived macrophages and mediated by Müller cell activation Finally, for each of PDA and SVR, we will discuss current approaches to disease management and treatment and consider novel avenues for potential future therapies.

Immunological Aspects of Age-Related Macular Degeneration

Increasing evidence over the past two decades points to a pivotal role for immune mechanisms in age-related macular degeneration (AMD) pathobiology. In this chapter, we will explore immunological aspects of AMD, with a specific focus on how immune mechanisms modulate clinical phenotypes of disease and severity and how components of the immune system may serve as triggers for disease progression in both dry and neovascular AMD. We will briefly review the biology of the immune system, defining the role of immune mechanisms in chronic degenerative disease and differentiating from immune responses to acute injury or infection. We will explore current understanding of the roles of innate immunity (especially macrophages), antigen-specific immunity (T cells, B cells, and autoimmunity), immune amplifications systems, especially complement activity and the NLRP3 inflammasome, in the pathogenesis of both dry and neovascular AMD, reviewing data from pathology, experimental animal models, and clinical studies of AMD patients. We will also assess how interactions between the immune system and infectious pathogens could potentially modulate AMD pathobiology via alterations in in immune effector mechanisms. We will conclude by reviewing the paradigm of "response to injury," which provides a means to integrate various immunologic mechanisms along with nonimmune mechanisms of tissue injury and repair as a model to understand the pathobiology of AMD.

The Effect of Systemic Hyperoxia and Hypoxia on Scotopic Thresholds in People with Early and Intermediate Age-related Macular Degeneration

Purpose: Morphological retinal changes combined with functional evidence implicate hypoxia in the pathogenesis of age-related macular degeneration (AMD). However, the role of hypoxia in the scotopic threshold deficit reported in AMD has not been investigated. This study compared scotopic thresholds in participants with early and intermediate AMD recorded under conditions of systemic hypoxia, hyperoxia and normoxia. Materials and Methods: Over two sessions scotopic thresholds were measured with participants breathing 21% and 60% oxygen (n = 12 early AMD, n = 11 age-similar controls) or 21% and 14% oxygen (n = 16 early AMD, n = 20 age-similar controls). Thresholds were measured using a 'white', annular 12 degrees stimulus, using a QUEST procedure. Results: There was no statistically significant change in scotopic thresholds within the AMD or control group when breathing the hyperoxic gas mixture (60% oxygen) or the hypoxic gas mixture (14% oxygen) when compared to the normoxic condition (21% oxygen). There was also no statistically significant difference in scotopic thresholds between groups under the hyperoxic or hypoxic gas conditions. The difference between groups under the normoxic condition was not statistically significant for the hyperoxia study (p = .70), but did reach significance in the hypoxia study (p = .05). Conclusion: This study provided no evidence that breathing that breathing 14% or 60% oxygen altered scotopic thresholds in those with early AMD when compared to controls. However, the lack of elevated scotopic thresholds in the AMD group of the hyperoxia study is of note, as it is unlikely that hyperoxia would reduce thresholds which were not significantly raised at baseline, regardless of whether hypoxia was a factor in the disease pathogenesis. The findings of this study do not rule out a role for hypoxia in early AMD, but this needs to be assessed in future experiments using measures that differ significantly between people with AMD and controls.

Age-Related Macular Degeneration: Review of Pathogenesis

Age-related macular degeneration is a condition (a) characterized by accumulation of membranous debris on both sides of the retinal pigment epithelium (RPE) basement membrane. Clinical manifestations of drusen, atrophy of the RPE/choriocapillaris, RPE detachment, and choroidal new vessel (CNV) formation occur after age 50 years. A hypothetical pathogenic sequence of events consistent with known data is: 1) RPE dysfunction (e.g., precipitated by an inherited susceptibility and/or environmental exposure); 2) accumulation of intracellular material in the RPE (e.g., accumulation of normal substrate material that is not enzymatically degraded properly vs. abnormal substrate material); 3) abnormal accumulation of extracellular material (basal laminar and basal linear deposit); 4) change in Bruch's membrane composition (e.g., increased lipid deposition and protein crosslinking); 5) change in Bruch's membrane parmeability to nutrients (e.g., impaired diffusion of water soluble plasma constituents across Bruch's membrane); and 6) response of the RPE to metabolic distress (i.e., atrophy vs. CNV growth). Histopathological and clinical studies indicate that areas of choroidal ischemia often are seen near CNVs in AMD patients. In response to decreased oxygen delivery/metabolic “distress”, the RPE may elaborate substances leading to CNV growth. Perhaps RPE atrophy, followed by choriocapillaris and photoreceptor atrophy, is a response to decreased nutrients/increasing metabolic abnormalities in areas of excessive accumulation of extracellular debris. Unanswered questions regarding AMD include: 1) is AMD an ocular manifestation of a systemic disease or purely an ocular disease?; 2) what determines whether CNVs vs.atrophy of the RPE-choriocapillaris-photoreceptors develops?; and 3) what induces the maturation of CNVs into an inactive scar, and what limits the growth of most CNVs to the area centralis?

Therapeutic Antibody-Like Immunoconjugates against Tissue Factor with the Potential to Treat Angiogenesis-Dependent as Well as Macrophage-Associated Human Diseases

Accumulating evidence suggests that tissue factor (TF) is selectively expressed in pathological angiogenesis-dependent as well as macrophage-associated human diseases. Pathological angiogenesis, the formation of neovasculature, is involved in many clinically significant human diseases, notably cancer, age-related macular degeneration (AMD), endometriosis and rheumatoid arthritis (RA). Macrophage is involved in the progression of a variety of human diseases, such as atherosclerosis and viral infections (human immunodeficiency virus, HIV and Ebola). It is well documented that TF is selectively expressed on angiogenic vascular endothelial cells (VECs) in these pathological angiogenesis-dependent human diseases and on disease-associated macrophages. Under physiology condition, TF is not expressed by quiescent VECs and monocytes but is solely restricted on some cells (such as pericytes) that are located outside of blood circulation and the inner layer of blood vessel walls. Here, we summarize TF expression on angiogenic VECs, macrophages and other diseased cell types in these human diseases. In cancer, for example, the cancer cells also overexpress TF in solid cancers and leukemia. Moreover, our group recently reported that TF is also expressed by cancer-initiating stem cells (CSCs) and can serve as a novel oncotarget for eradication of CSCs without drug resistance. Furthermore, we review and discuss two generations of TF-targeting therapeutic antibody-like immunoconjugates (ICON and L-ICON1) and antibody-drug conjugates that are currently being tested in preclinical and clinical studies for the treatment of some of these human diseases. If efficacy and safety are proven in current and future clinical trials, TF-targeting immunoconjugates may provide novel therapeutic approaches with potential to broadly impact the treatment regimen of these significant angiogenesis-dependent, as well as macrophage-associated, human diseases.

Aqueous vascular endothelial growth factor and clinical outcomes correlation after single intravitreal injection of bevacizumab in patients with neovascular age-related macular degeneration

Purpose

To evaluate the concentration of vascular endothelial growth factor (VEGF) in aqueous humor after a single intravitreal injection of bevacizumab (IVB) in eyes with neovascular age-related macular degeneration (AMD).

Methods

In this prospective interventional case series study, 24 eyes of 24 patients with types 1 and 2 choroidal neovascularization secondary to neovascular AMD were treated with a single intravitreal injection of bevacizumab. Aqueous humor samples were obtained before the intravitreal injection and at one week, one month, and three months follow-up periods. Best-corrected visual acuity (BCVA) and three spectral-domain optical coherence tomography parameters (central retinal thickness, macular volume and macular area) were also analyzed and correlated with VEGF expression at the baseline and each follow-up period.

Results

All of the ninety-six aqueous humor study taps were well tolerated by the study patients without adverse events. Increased VEGF levels (mean ± SD = 179.7 ± 88.3 pg/mL) were observed in the aqueous humor of all study patients before the intravitreal injection of bevacizumab. At all follow-up periods, compared to baseline, levels of VEGF significantly reduced (P < 0.0001), and BCVA significantly improved (P < 0.005). The lowest VEGF expression was observed at 1 week, and the greatest BCVA improvement occurred 1 month after treatment. At 1 month, central retinal thickness (CRT), macular volume (MV), and macular area (MA) significantly reduced compared to baseline (P < 0.0001, P = 0.0005, P = 0.007, P = 0.009, respectively). At 1 week and 3 months, although without statistical significance (P > 0.005), CRT, MV and MA also reduced in comparison to baseline.

Conclusions

Single intravitreal bevacizumab injection in eyes with neovascular AMD resulted in a substantial decrease of aqueous VEGF levels 1 week after treatment with the greatest improvement of clinical outcomes occurring at 1 month follow-up.

Association of the polymorphism Y402H in the CFH gene with response to anti-VEGF treatment in age-related macular degeneration: a systematic review and meta-analysis

To explore whether the complement factor H (CFH) polymorphism rs1061170/Y402H is associated with responsiveness to antivascular endothelial growth factor (VEGF) agents in age-related macular degeneration (AMD). We reviewed the English literature to examine the association between the polymorphism rs1061170/Y402H of the CFH gene and responsiveness to treatment with anti-VEGF drugs in AMD patients. A meta-analysis of eligible studies was also performed. Pooled odds ratios (ORs) and 95% CIs were estimated using Stata V.12.0. Statistical heterogeneity was measured using Q-statistic testing. Fourteen relevant studies including a total of 2963 AMD patients were eligible. In AMD patients without a treatment history, individuals carrying the rs1061170/Y402H TT genotype were more likely to achieve a better outcome (OR = 1.932, 95% CI = 1.125-3.317, p = 0.017) than those carrying the CC genotype. The polymorphism rs1061170/Y402H might be a genetic predictor of treatment response to anti-VEGF therapy in AMD patients. Further prospective research including a larger number of patients is needed to validate this finding.

Molecular mechanisms of subretinal fibrosis in age-related macular degeneration

Subretinal fibrosis is a result of a wound healing response that follows choroidal neovascularization in neovascular age-related macular degeneration (nAMD). Although anti-vascular endothelial growth factor therapy has become a standard treatment that improves visual acuity in many nAMD patients, unsuccessful treatment outcomes have often been attributed to the progression of subretinal fibrosis. In this review, we summarize the cellular and extracellular components of subretinal fibrous membranes and also discuss the possible molecular mechanisms including the functional involvement of growth factors and the inflammatory response in the process. Moreover, we present an murine animal model of subretinal fibrosis that might facilitate greater understanding of the pathophysiology and the development of novel therapeutic strategies for the inhibition of subretinal fibrosis in nAMD.

The stereotypical molecular cascade in neovascular age-related macular degeneration: the role of dynamic reciprocity

This review summarises our current understanding of the molecular basis of subretinal neovascularisation (SRNV) in age-related macular degeneration (AMD). The term neovascular AMD (NVAMD) is derived from the dominant early clinical features of haemorrhage, fluid, and lipid in the subretinal space (SRS) and the historical role of fluorescein angiography in detecting the presence of NV tissue. However, at the cellular level, SRNV resembles an aberrant but stereotypical tissue repair response that incorporates both an early inflammatory phase and a late fibrotic phase in addition to the neovascular (NV) component that dominates the early clinical presentation. This review will seek not only to highlight the important molecules involved in each of these components but to demonstrate that the development of SRNV has its origins in the earliest events in non-NV AMD pathogenesis. Current evidence suggests that this early-stage pathogenesis is characterised by complement-mediated immune dysregulation, leading to a state of chronic inflammation in the retinal pigment epithelium/Bruch's membrane/choriocapillaris complex. These initial events can be seamlessly and inextricably linked to late-stage development of SRNV in AMD by the process of dynamic reciprocity (DyR), the ongoing bidirectional communication between cells, and their surrounding matrix. Moreover, this correlation between disease onset and eventual outcome is reflected in the temporal and spatial correlation between chronic inflammation, NV, and fibrosis within the reparative microenvironment of the SRS. In summary, the downstream consequences of the earliest dysfunctional molecular events in AMD can result in the late-stage entity we recognize clinically as SRNV and is characterized by a spectrum of predictable, related, and stereotypical processes referred to as DyR.

Trophic factors in the pathogenesis and therapy for retinal degenerative diseases

Trophic factors are endogenously secreted proteins that act in an autocrine and/or paracrine fashion to affect vital cellular processes such as proliferation, differentiation, and regeneration, thereby maintaining overall cell homeostasis. In the eye, the major contributors of these molecules are the retinal pigment epithelial (RPE) and Müller cells. The primary paracrine targets of these secreted proteins include the photoreceptors and choriocapillaris. Retinal degenerative diseases such as age-related macular degeneration and retinitis pigmentosa are characterized by aberrant function and/or eventual death of RPE cells, photoreceptors, choriocapillaris, and other retinal cells. We discuss results of in vitro and in vivo animal studies in which candidate trophic factors, either singly or in combination, were used in an attempt to ameliorate photoreceptor and/or retinal degeneration. We also examine current trophic factor therapies as they relate to the treatment of retinal degenerative diseases in clinical studies.

Monocyte chemoattractant protein-1 in the aqueous humour of patients with age-related macular degeneration

BACKGROUND

  To investigate the role of inflammation in age-related macular degeneration by measuring the levels of cytokines in the aqueous humour.

METHODS

  Samples of aqueous humour were collected from 34 patients with age-related macular degeneration and 16 age-matched control subjects undergoing cataract surgery. Age-related macular degeneration stage was determined clinically, before surgery. Levels of cytokines were measured using Luminex X-MAP technology, and positive results were verified by Western blot.

RESULTS

  Age-related macular degeneration was moderate in 18 patients and advanced in 16. The advanced age-related macular degeneration group was further divided into patients with active choroidal neovascularization (n = 7), disciform scar (n = 7) or central geographic atrophy (n = 2). Higher-than-normal levels of monocyte chemoattractant protein-1 in the aqueous humour were associated with advanced age-related macular degeneration (200 ± 140 pg/mL vs. 100 ± 61 pg/mL; P = 0.03), especially active choroidal neovascularization (255 ± 155 pg/mL; P = 0.02), Western blot analysis verified the monocyte chemoattractant protein-1 findings. Patients with disciform scar showed a trend of abnormally high levels of interleukin-12 (p70) (1.7 ± 2.4 pg/mL vs. 0.2 ± 1 pg/mL; P = 0.07), tumour necrosis factor-α (1.8 ± 2.4 pg/mL vs. 0.3 ± 1 pg/mL; P = 0.06) and interleukin-12 (4.7 ± 6.4 pg/mL vs. 1.2 ± 2.1 pg/mL; P = 0.08).

CONCLUSION

  Elevated levels of inflammation-related cytokines in the aqueous humour in various stages of age-related macular degeneration may suggest a pathogenic role of inflammation. Monocyte chemoattractant protein-1 may be indicative of the angiogenic phase. Further corroborative studies are required.

Aqueous humor levels of vascular endothelial growth factor before and after intravitreal bevacizumab in type 3 versus type 1 and 2 neovascularization. A prospective, case-control study

PURPOSE

To determine the aqueous levels of vascular endothelial growth factor (VEGF) in patients with type 3 neovascularization (NV) secondary to age-related macular degeneration (AMD) and to compare the levels of those with type 1 and 2 NV secondary to AMD before and after administration of intravitreal bevacizumab (IVB).

DESIGN

Prospective, case-control study.

METHODS

Aqueous samples were collected from 29 eyes of 29 patients with untreated wet AMD at baseline (day of the first IVB), month 1 (day of the second IVB), and month 2 (day of the third IVB). Among them, 10 eyes presented with type 1, 9 with type 2, and 10 with type 3 NV. A group of 14 aqueous samples from 14 patients who underwent cataract surgery without other ocular or systemic disease comprised the controls. Main outcome measures were concentration of VEGF at baseline and after IVB in the 3 NV groups; secondary outcome measures included best-corrected visual acuity (BCVA) and central macular thickness (CMT) changes after IVB. Levels of VEGF were determined by commercially available enzyme-linked immunosorbent assay kits.

RESULTS

VEGF concentrations in aqueous humor at baseline were higher in patients with type 3 NV when compared to controls (P = .0001) and type 1 and 2 NV patients (P = .002 and P = .0001 respectively). At month 1, levels of VEGF were significantly reduced compared to baseline (P < .05) and significantly lower compared to the controls (P < .005) in each NV group. These low levels were maintained at the 2-month interval. BCVA significantly improved in type 1 and 2 NV groups (P < .05). CMT significantly reduced in each NV group compared to baseline (P < .05).

CONCLUSION

In eyes with untreated wet AMD, aqueous levels of VEGF are significantly higher in type 3 NV than in type 1 or 2 NV. Regardless of the type of NV, aqueous VEGF levels significantly reduce 1 month after IVB as compared to both the baseline measurements and the values recorded in age-matched controls. These decreases are maintained at 2 months after administering a second IVB 30 days after the initial injection.

MCP-1-activated monocytes induce apoptosis in human retinal pigment epithelium

PURPOSE

The inflammatory response in age-related macular degeneration (AMD) is characterized by mononuclear leukocyte infiltration of the outer blood-retina barrier formed by the retinal pigment epithelium (RPE). A key mechanistic element in AMD progression is RPE dysfunction and apoptotic cell loss. The purpose of this study was to evaluate whether monocyte chemoattractant protein (MCP)-1-activated monocytes induce human RPE apoptosis and whether Ca(2+) and reactive oxygen species (ROS) are involved in this process.

METHODS

A cell-based fluorometric assay was used to measure intracellular Ca(2+) concentrations ([Ca(2+)](i)) in RPE cells loaded with fluorescent Ca(2+) indicator. Intracellular RPE ROS levels were measured by using the 5- and 6-chloromethyl-2',7'-dichlorodihydrofluorescence diacetate acetyl ester (CM-H(2)DCFDA) assay. RPE apoptosis was evaluated by activated caspase-3, Hoechst staining, and apoptosis ELISA.

RESULTS

MCP-1-activated human monocytes increased [Ca(2+)](i), ROS levels, and apoptosis in RPE cells, all of which were inhibited by 8-bromo-cyclic adenosine diphosphoribosyl ribose (8-Br-cADPR), an antagonist of cADPR. Although the ROS scavengers pyrrolidinedithiocarbamate (PDTC) and N-acetylcysteine (NAC) significantly inhibited ROS production and apoptosis induced by activated monocytes, they did not affect induced Ca(2+) levels. The induced Ca(2+) levels and apoptosis in RPE cells were inhibited by an antibody against cluster of differentiation antigen 14 (CD14), an adhesion molecule expressed by these cells.

CONCLUSIONS

These results indicate that CD14, Ca(2+), and ROS are involved in activated monocyte-induced RPE apoptosis and that cADPR contributes to these changes. Understanding the complex interactions among CD14, cADPR, Ca(2+), and ROS may provide new insights and treatments of retinal diseases, including AMD.

Inflammatory choroidal neovascularization

Purpose and Methods:

Choroidal neovascularization (CNV) can be a severe sight-threatening sequela, which can be secondary to both infectious and noninfectious uveitis. This review summarizes the different diseases associated with CNV, highlighting new treatment modalities and the possible strategies, which could be applied for the therapy of this occurrence.

Results:

Since CNV can often originate from posterior pole lesions and can be hard to identify, an accurate examination is mandatory in order to identify the correct diagnosis. In the majority of cases, fluorescein angiography (FA), indocyanine green angiography (ICGA) and optical coherence tomography (OCT) enable the determination of the clinical characteristics of the CNV. An infectious disease should be looked for to include a suitable therapy when available. The treatment strategy for CNV secondary to noninfectious uveal inflammations should be directed at controlling the inflammatory process. Systemic corticosteroids with or without immunosuppressive agents are indicated even when the CNV occurs with apparently inactive uveitis: Chronic subclinical inflammation can be the basis for the pathogenesis of CNV. Additional therapies aimed directly at the neovascular process, such as the intravitreal anti-Vascular Endothelial Growth Factor (VEGF) agents, are recommended particularly when the therapy shows an insufficient response.

Conclusion:

CNV secondary to uveitis is a severe sequela leading to significant visual impairment. ICGA is mandatory in order to obtain relevant information about the choroidal status. Several therapeutic options have been considered, but no guidelines are provided at the moment. Moreover, the current data are still only based on case reports or small series. For such reasons, further trials are mandatory to validate the preliminary available results.

Association of superoxide anions with retinal pigment epithelial cell apoptosis induced by mononuclear phagocytes

PURPOSE

Oxidative stress of the retinal pigment epithelium by reactive oxygen species and monocytic infiltration have been implicated in age-related macular degeneration. The purpose of this study was to determine the role of superoxide anions (O(2)(-)) in mononuclear phagocyte-induced RPE apoptosis.

METHODS

Mouse RPE cell cultures were established from wild-type and heterozygous superoxide dismutase 2-knockout (Sod2(+/-)) mice. The intracellular reactive oxygen species, O(2)(-) and hydrogen peroxide, were measured by using dihydroethidium assay and 5-(and 6)-chloromethyl-2',7'-dichlorodihydrofluorescence diacetate, acetyl ester assay, respectively. RPE apoptosis was evaluated by Hoechst staining and terminal deoxynucleotidyltransferase dUTP nick-end labeling assay. Changes in mitochondrial membrane potential were detected by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide dye. Activated caspases and caspase-3 were detected in situ by FITC-VAD-fmk staining and caspase-3 substrate, respectively.

RESULTS

Mononuclear phagocytes and interferon-gamma-activated mononuclear phagocytes induced the production of intracellular RPE O(2)(-), a decrease in RPE mitochondrial membrane potential, caspase activation, and apoptosis of mouse RPE cells. All theses changes were significantly enhanced in the Sod2(+/-) RPE cells. Activated mononuclear phagocytes induced more of these oxidative and apoptotic changes in RPE cells than did unstimulated mononuclear phagocytes.

CONCLUSIONS

The authors have shown that the decreased expression of SOD2 and increased superoxide production correlate with RPE apoptosis induced by unstimulated and activated mononuclear phagocytes. The authors suggest that elevated O(2)(-) levels due to genetic abnormalities of SOD2 or immunologic activation of mononuclear phagocytes lead to greater levels of RPE apoptosis. The present study could serve as a useful model to characterize RPE/phagocyte interaction in AMD and other retinal diseases.

Combinatory inhibition of VEGF and FGF2 is superior to solitary VEGF inhibition in an in vitro model of RPE-induced angiogenesis

BACKGROUND

Choroidal neovascularisation (CNV) as a feature of exudative age-related macular degeneration (AMD) is partially regulated by retinal pigment epithelium (RPE). In this study, the effect of combinatory anti-angiogenic treatment was evaluated using a novel in vitro assay of RPE-induced angiogenesis.

METHODS

RPE isolated from surgically excised CNV-membranes (CNV-RPE) was used to stimulate sprouting of endothelial cell (EC) spheroids in a 3D collagen matrix. The anti-angiogenic effect of solitary anti-VEGF antibodies (bevacizumab) was compared to a combinatory treatment with anti-VEGF and anti-FGF2 antibodies.

RESULTS

Anti-VEGF treatment inactivated all RPE-derived VEGF but was unable to fully inhibit EC sprouting induced by CNV-RPE. Combined anti-VEGF/anti-FGF treatment inactivated both growth factors and reduced EC sprouting significantly.

CONCLUSIONS

RPE from CNV patients expresses angiogenic growth factors that act in part independently of VEGF. Targeted combinatory therapy can be superior to solitary anti-VEGF therapy. One possible candidate for combinatory therapy is FGF2.

Pro-inflammatory cytokines increase reactive oxygen species through mitochondria and NADPH oxidase in cultured RPE cells

Reactive oxygen species (ROS) generated during inflammation are believed to play critical roles in various ocular diseases. However, the underlying mechanisms remain poorly understood. We investigated if pro-inflammatory cytokines, tumor necrosis factor (TNF)-alpha, interleukin-1 beta (IL-1 beta), and interferon-gamma (IFN-gamma), induce ROS in human retinal pigment epithelial (RPE) cells. TNF-alpha, IL-1 beta and IFN-gamma increased both intracellular and extracellular ROS production in a time- and dose-dependent manner. Thenoyltrifluoroacetone (TTFA), an inhibitor of mitochondrial respiratory chain, blocked TNF-alpha- and IFN-gamma-, but not IL-1 beta-induced ROS, whereas other two mitochondrial respiratory chain inhibitors, rotenone and antimycin A, had no effect. NADPH oxidase inhibitor (diphenylene iodinium) abolished the ROS production induced by IL-1 beta or IFN-gamma, but not by TNF-alpha, whereas 6-aminonicotinamide (6AN), an inhibitor of the hexose monophosphate shunt (HMS), had no significant effects on the ROS induced by all three cytokines. ROS scavengers, pyrrolidinedithiocarbamate (PDTC) and N-acetyl-cysteine (NAC), reduced the levels of ROS induced by TNF-alpha, IL-1 beta and IFN-gamma (P<0.05). Collectively, these results demonstrate that TNF-alpha, IL-1 beta and IFN-gamma increase mitochondrial- and NADPH oxidase-generated ROS in human RPE cells.

Photodynamic treatment versus photodynamic treatment associated with systemic steroids for idiopathic choroidal neovascularisation

AIM

To compare photodynamic therapy (PDT) with PDT associated with systemic steroids (SS) for the control of juxta/subfoveal idiopathic choroidal neovascularisation (ICNV).

METHODS

Patients with juxta/subfoveal ICNV were randomised and then treated. Visual gain and loss were defined as improvement in or worsening for two or more lines of best-corrected visual acuity (BCVA), respectively. Choroidal neovascularisation size after treatment was classified as "increased" and "reduced" if it was increased or reduced by >200 microm(2), respectively.

RESULTS

10 patients were treated with PDT, 10 with SS followed by PDT. The median follow-up time was 22 and 21 months for the "steroid+PDT group" and the "PDT group", respectively. At 1 year, in the PDT group, five patients had stable/improved BCVA, and five became worse; the mean number of PDT was 2.3; in the steroid+PDT group, all patients were stable/improved and the mean number of PDT was 1.2. The difference between the two groups was significant (p<0.05). At 1 year, the ICNV size after treatment was better in the steroid+PDT group than in the PDT group (p<0.05).

CONCLUSION

The use of SS before PDT has shown better BCVA outcome than PDT alone (p<0.05), reducing the mean number of PDT applications (1.2 vs 2.3, respectively), with smaller scar size.

Aqueous humor levels of vascular endothelial growth factor and pigment epithelium-derived factor in polypoidal choroidal vasculopathy and choroidal neovascularization

PURPOSE

To determine the aqueous levels of vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in patients with active polypoidal choroidal vasculopathy (PCV) and choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) and pathologic myopia.

DESIGN

Prospective, comparative control study.

METHODS

Aqueous humors were collected from 32 eyes of 32 patients for either active PCV or CNV. Among them, 11 eyes had active and symptomatic PCV, 12 eyes had active CNV secondary to AMD, and nine eyes had active CNV of pathologic myopia. Levels of VEGF and PEDF were determined by commercially available enzyme-linked immunosorbent assay kits. A group of 10 aqueous samples from 10 patients who underwent cataract surgery without other ocular or systemic diseases comprised the controls.

RESULTS

VEGF concentrations in aqueous humor were markedly increased in patients with PCV, CNV of AMD, and CNV of myopia when compared with the controls (analysis of variance [ANOVA], P < .001). VEGF levels in eyes with PCV were, however, significantly lower than those of exudative AMD (P = .045). The PEDF levels were also significantly different among the groups (ANOVA, P = .001), and we observed increased levels in PCV, CNV of AMD, and CNV of myopia.

CONCLUSIONS

VEGF and PEDF factors were coexpressed and increased with positive correlation in aqueous humor of eyes with active PCV. The different levels of both factors in eyes of PCV and AMD might suggest distinct clinical entities or different angiogenesis courses between PCV and AMD.

EXPRESSION OF CONNECTIVE TISSUE GROWTH FACTOR AND ITS POTENTIAL ROLE IN CHOROIDAL NEOVASCULARIZATION

BACKGROUND

To determine the expression of connective tissue growth factor (CTGF) in choroidal neovascularization.

METHODS

Surgically excised choroidal neovascular membranes (CNVMs) were obtained at vitrectomy from eight eyes with age-related macular degeneration, five eyes with high myopia, and two eyes with angioid streaks. Light microscopic immunohistochemical analysis was performed to detect CTGF, transforming growth factor beta 1 (TGF-beta1), vascular endothelial growth factor (VEGF), pancytokeratin, and smooth muscle actin (SMA).

RESULTS

CNVMs were classified by fibrotic status as cellular CNVM, moderate fibrous CNVM, and extensive fibrous CNVM. CTGF expression was found in vascular cells, stromal cells, and retinal pigment epithelium (RPE) cells. For the stromal cells, fibroblastlike cells were most strongly positive for CTGF. CTGF immunoreactivity in the stroma was stronger in the fibrous CNVMs than in the cellular CNVMs. Immunohistochemical analysis of serial sections revealed colocalization of CTGF with TGF-beta1 and VEGF; colocalization of CTGF with pancytokeratin and SMA was also found.

CONCLUSION

Our findings suggest that transdifferentiated RPE cells and vascular cells possess remarkable CTGF expression in CNVMs. This expression of CTGF may stimulate fibroblasts to produce extracellular matrix and may promote angiogenesis in vascular cells. Colocalized TGF-beta1 and VEGF may also contribute the upregulation of CTGF.

Future pharmacological treatment options for nonexudative and exudative age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in the industrialised world. Within the past decade, researchers have introduced many promising prevention and treatment options in an attempt to minimise the central vision loss imparted from AMD. Based on large-scale, randomised, prospective, placebo-controlled trials, a specially formulated combination of the antioxidants vitamin C, vitamin E, beta-carotene, copper and zinc is the only proven means of AMD prophylaxis. Thermal laser photocoagulation and photodynamic therapy with verteporfin are the only standard treatment options. However, efficacy is limited and treatment is only applicable to a minority of AMD patients. Thus, alternative pharmacological interventions are in all phases of clinical development. Researchers are guardedly optimistic that these advances may change the entire approach to AMD management in the near future. This review article will detail the currently accepted treatment options, as well as describe several of the more promising investigational pharmacological approaches to AMD.

EVALUATION OF PHOTOPOINT PHOTOSENSITIZER MV6401, INDIUM CHLORIDE METHYL PYROPHEOPHORBIDE, AS A PHOTODYNAMIC THERAPY AGENT IN PRIMATE CHORIOCAPILLARIS AND LASER-INDUCED CHOROIDAL NEOVASCULARIZATION

PURPOSE

To assess the potential of a new photosensitizer, indium chloride methyl pyropheophorbide (PhotoPoint MV6401), for ocular photodynamic therapy (PDT) in normal choriocapillaris vessels and experimentally induced choroidal neovascularization in New-World monkeys (Saimiri sciureus).

METHODS

PhotoPoint MV6401 (Miravant Pharmaceuticals, Inc., Santa Barbara, CA) was activated at 664 nm using a DD3-0665 (Miravant Systems, Inc., Santa Barbara, CA) 0.5 W diode laser. The efficacy of MV6401 was evaluated by indirect ophthalmoscopy, fundus photography, fluorescein angiography, and histology. The drug and light doses were 0.10 micromoles/kg to 0.3 micromoles/kg and 10 J/cm to 40 J/cm, respectively, and post-injection activation times ranged from +10 minutes to +120 minutes.

RESULTS

Best closure of normal choriocapillaris was achieved at a dosage level of 0.15 micromoles/kg in primates. Histology demonstrated that increased post-injection activation times (+60 minutes to +90 minutes) and low laser light doses (10 J/cm to 20 J/cm) in the primate model resulted in selective closure of the choriocapillaris and medium sized choroidal vessels with minimal effect to the retina. Histology from neovascular lesions PDT-treated with MV6401 revealed significant diminution of vascularity, correlating with diminution of leakage observed on angiography.

CONCLUSION

PhotoPoint MV6401, indium chloride methyl pyropheophorbide, is a potent photosensitizer that demonstrates both efficacy and selectivity in primate choriocapillaris and laser-induced choroidal neovascularization occlusion. Maximum selectivity was achieved using a post infusion interval of +60 to +90 minutes.

Expression of pigment epithelium derived factor and vascular endothelial growth factor in choroidal neovascular membranes and polypoidal choroidal vasculopathy

AIMS

To determine whether pigment epithelium derived factor (PEDF), a protein that inhibits angiogenesis, is expressed in human choroidal neovascular membranes (CNVMs) and in tissues from an eye with polypoidal choroidal vasculopathy (PCV). In addition, to compare the expression of PEDF with that of vascular endothelial growth factor (VEGF), a known stimulator of angiogenesis, in these tissues.

METHODS

CNVMs, associated with age related macular degeneration (AMD), angioid streaks, and PCV, were obtained during surgery. The expression of PEDF and VEGF in the excised subretinal fibrovascular membranes was determined by immunohistochemistry.

RESULTS

PEDF and VEGF were strongly expressed in the vascular endothelial cells and retinal pigment epithelial (RPE) cells in the CNVMs where numerous new vessels were prominent (clinically active CNVMs). On the other hand, immunoreactivity for PEDF and VEGF was weak in the new vessels where fibrosis was prominent (clinically quiescent CNVMs). However, the RPE cells were still positive for PEDF and VEGF. The specimens from the eye with PCV also showed strong expression of PEDF and VEGF in the vascular endothelial cells and the RPE cells.

CONCLUSION

Because PEDF is an inhibitor of ocular angiogenesis and an inhibitor of ocular cell proliferation, our results suggest that PEDF along with VEGF may modulate the formation of subfoveal fibrovascular membranes.

Recruitment of marrow-derived endothelial cells to experimental choroidal neovascularization by local expression of vascular endothelial growth factor

PURPOSE

The question of whether adult animals maintain a reservoir of endothelial progenitor cells (EPCs) in the bone marrow that is involved in neovascularization is under investigation. The following study was undertaken to examine the potential contribution of EPCs to the development of choroidal neovascularization (CNV) in adult mice and to examine the role of local expression of vascular endothelial growth factor (VEGF) in this process.

METHODS

Lethally irradiated, adult female nude mice were engrafted with whole bone marrow isolated from male transgenic mice expressing LacZ driven by the endothelial specific Tie-2 promoter. Two months, following bone marrow reconstitution, confirmed by quantitative Taqman PCR, an E1-deleted adenoviral vector expressing vascular endothelial growth factor (165) (Ad.VEGF(165)) was injected subretinally to induce CNV, confirmed by collagen IV immunohistochemistry. Bone marrow-derived endothelial cells were detected using either X-gal staining or Y chromosome in situ hybridization. Y chromosome positive cells within the CNV were confirmed to be endothelial cells by lectin staining.

RESULTS

Subretinal Ad.VEGF(165) was capable of inducing CNV. Four-week old lesions were found to contain LacZ expressing cells within the CNV in bone marrow transplanted animals but not in negative control animals. Eighteen percent of all Y chromosome positive cells within the CNV were found to be lectin positive while 27% of all endothelial cells within the CNV were Y chromosome positive.

CONCLUSION

Engrafted bone marrow-derived EPCs were shown to differentiate into endothelial cells at the site of subretinal VEGF-induced CNV in mice. These results suggest that EPCs contribute to the formation of neovascularization and that subretinal expression of VEGF might play an important role in recruitment of these cells to the site of CNV.

Corticosteroids in posterior segment disease: an update on new delivery systems and new indications

PURPOSE OF REVIEW

Corticosteroids are traditionally used for inflammatory disorders because of their ability to diminish neutrophil transmigration, limit access to sites of inflammation, and decrease cytokine production. More recently, however, investigators have focused on the angiostatic and antipermeability properties of corticosteroids for posterior segment diseases such as age-related macular degeneration (AMD), diabetic retinopathy, and macular edema. Both new angiostatic and traditional corticosteroids are currently undergoing evaluation as new delivery techniques such as intravitreal injection and intraocular sustained-release devices facilitate high local angiostatic and antipermeability concentrations while minimizing extraocular toxicity. The purpose of this review is to discuss recent work concerning both the mechanism and effectiveness of these newer treatments.

RECENT FINDINGS

Steroids may exert a beneficial effect in AMD-related choroidal neovascular membranes (CNVM) through inhibition of CNVM-promoting macrophages and direct inhibition of angiogenic growth factors. They may also alter extracellular matrix turnover and inhibit matrix metalloproteinases involved in CNVM formation. Intravitreal steroid injections potently inhibit experimental CNVM in primates and rats and have shown promise in some early human pilot trials. In proliferative diabetic retinopathy, steroids may directly inhibit growth factors such as vascular endothelial derived growth factor and inhibit leukocytes that play an important role in early microvascular alterations. Intravitreal steroid injections inhibit experimental preretinal neovascularization in pigs and rats, and rubeosis in some early human studies. In addition, the effect of steroids on vascular permeability has led to their use for macular edema from many causes such as diabetes and venous occlusive disease.

SUMMARY

The use of steroids to treat a number of retinal diseases is gaining wide spread acceptance. The apparent short-term success must be balanced by the fact that the long-term safety and efficacy have yet to be determined for any of these approaches. A number of large randomized prospective clinical trials of steroid compounds and new delivery systems are currently under way for AMD, diabetic retinopathy, uveitis, and other retinovascular diseases, and hopefully these studies will provide guidance about the use of these new modalities.

Choroidal neovascularization

PURPOSE

To review clinicopathologic findings of choroidal neovascularization (CNV) in a historical framework with emphasis on pathobiology and correlation with treatment.

DESIGN

Selective literature review combined with authors' experience.

RESULTS

Choroidal neovascularization represents a stereotypic, nonspecific response to a specific stimulus. Although CNV differs among patients, the general growth patterns are subretinal pigment epithelium (type 1), subretinal (type 2), or combined. Choroidal neovascularization occurs over time in dynamic stages of initiation, active and involutional. Treatments are now being designed based on modern understanding of CNV growth.

CONCLUSIONS

Progress continues to be made concerning understanding the pathobiology and treatment of CNV.

Squalamine lactate reduces choroidal neovascularization in a laser-injury model in the rat

PURPOSE

To determine if systemically administered squalamine lactate, a novel aminosterol with antineoplastic and antiangiogenic activity, inhibits the development of experimental choroidal neovascularization membranes (CNVMs) induced by laser trauma in a rat model.

METHODS

Twenty anesthetized male Brown-Norway rats received a series of 8 krypton red laser lesions per eye (647 nm, 0.05 second, 50 microm, 150 mW). One half the animals received an intraperitoneal injection of squalamine and the other one half received an injection of 5% dextrose in water, all performed in a masked fashion. Fundus photography and fluorescein angiography were performed at postlaser treatment days 14 and 28, and ocular tissues were processed for light microscopic examination following euthanasia of the rats on postlaser treatment day 28.

RESULTS

Although fundus photography and fluorescein angiography yielded no statistically significant quantitative differences between the two groups, histologic analysis of the lesion sites revealed a partial but statistically significant reduction of experimental CNVM development in the squalamine-treated population. In particular, the squalamine-treated eyes (n = 20) demonstrated lesions (n = 149) with a mean CNVM thickness +/- SD of 47 +/- 11 microm, as compared with the control eyes (n = 20) that had lesions (n = 142) with a mean CNVM thickness +/- SD of 63 +/- 14 microm (P < 0.001).

CONCLUSION

Systemically administered squalamine lactate partially reduced choroidal neovascular membrane development induced by laser trauma in this animal model. In conjunction with other existing and developing therapies, this agent may have a potential role in the treatment of human CNVM formation. Further study of squalamine lactate for treatment of neovascular eye disease is warranted.

Differential expression of angioregulatory factors in normal and CNV-derived human retinal pigment epithelium

BACKGROUND

Choroidal neovascularization (CNV) causes loss of vision in age-related macular degeneration (AMD). In CNV, choroidal capillaries penetrate Bruch's membrane and the retinal pigment epithelium (RPE). Angiogenic factors produced by RPE cells are suspected as major contributors to CNV development. We therefore studied the differential expression of angioregulatory factors in normal and CNV-derived RPE.

METHODS

Cultures of normal (ARPE-19) and CNV-derived RPE (CNV-RPE) were compared by quantitative PCR. Differential expression was verified on the protein level by immunohistochemistry in tissue samples.

RESULTS

The angioregulatory factors VEGF-A, VEGF-B, VEGF-C, Angiopoietin-1 (Ang-1) and Angiopoietin-2, Semaphorin-3A, PEDF, HIF-1, FGF-2, and the receptors VEGF-R2, Neuropilin-1 and Neuropilin-2 were detected in both, ARPE-19 and CNV-RPE. Transcription of PEDF, FGF-2, Neuropilin-2, Ang-1 and Ang-2 was significantly upregulated in CNV-RPE. EphA7, VEGF-R1 and leptin were transcribed exclusively in CNV-RPE and Eph-A7 and VEGF-R1 proteins were present exclusively in CNV specimens.

CONCLUSIONS

A set of common factors controlling angiogenesis was detected in both, ARPE-19 cells and CNV-RPE cells. Surprisingly, PEDF and other factors inhibiting angiogenesis are strongly upregulated in CNV-RPE; thus, at least in later stages, the RPE has a potential to control angiogenesis in age-related macular degeneration.

Current and Future Treatment Options for Nonexudative and Exudative Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in the industrialised world. Although relatively simple to diagnose through direct visualisation augmented with rapid sequence fluorescein angiography, treatment has presented a far greater challenge because the true aetiology of AMD is largely unknown. Within the past decade, researchers have introduced many new, potentially promising treatment and prevention options in an attempt to minimise the damage imparted from AMD. They capitalise on many of the theoretical and known factors contributing to AMD progression. A high-dose of an orally administered combination of the antioxidants ascorbic acid (vitamin C), tocopherol (vitamin E) and beta-carotene, in addition to copper and zinc, is the only widely accepted preventive therapy. Thermal laser photocoagulation and verteporfin photodynamic therapy are the only standard treatment options available based on large scale, randomised, prospective, placebo-controlled trials; however, efficacy is limited and only a minority of patients who present with AMD are eligible for these treatments. Many other preventive and treatment options are in all phases of clinical studies and expected to change the entire approach to AMD management in the near future. For example, alternative antioxidants, drusen ablation, apheresis and HMG-CoA reductase inhibitors have shown promise in some studies by preventing or slowing the progression of certain forms of AMD. In addition, alternative photodynamic therapies, low-intensity laser, antiangiogenic medications, radiation treatment and surgery have demonstrated the ability, albeit to differing degrees, to inhibit or possibly even reverse the severe vision loss often associated with AMD characterised by choroidal neovascularisation.

Activated monocytes induce human retinal pigment epithelial cell apoptosis through caspase-3 activation

Dysfunction and loss of human retinal pigment epithelial (HRPE) cells is a significant component of many ocular diseases, in which mononuclear phagocyte infiltration at the HRPE-related interface is also observed. In this study, we investigated whether HRPE cell apoptosis may be induced by overlay of IFN-gamma-activated monocytes. Human monocytes primed with IFN-gamma overlaid directly onto HRPE cells elicited significant increases in terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive HRPE cells (p < 0.0001) and decreases of proliferating cell nuclear antigen-positive (p < 0.0001) HRPE cells. The activated monocytes also induced HRPE cell caspase-3 activation, which was inhibited by the caspase-3 inhibitor, Z-DEVD-fmk. However, co-incubations in which activated monocytes were prevented from direct contact with HRPE cells or in which the monocytes were separated from the HRPE cells after 30 minutes of direct contact, did not induce significant HRPE cell apoptosis. Function-blocking anti-CD18 and anti-intercellular adhesion molecule-1 (ICAM-1) antibodies significantly reduced activated monocyte-induced TUNEL-positive HRPE cells by 48% (p = 0.0051) and 38% (p = 0.046), respectively. Anti-CD18 and anti-ICAM-1 antibodies significantly inhibited caspase-3 activity by 56% (p < 0.0001) and 45% (p < 0.0001), respectively. However, antibodies to vascular cell adhesion molecule-1, TNF-alpha, IL-1beta, or TNF-related apoptosis-inducing ligand did not inhibit apoptosis or caspase-3 activation. Direct overlay of monocytes also induced reactive oxygen metabolites (ROM) within HRPE cells. The intracellular HRPE cell ROM production was inhibited by the anti-CD18 and anti-ICAM-1 antibodies, but not by superoxide dismutase, presumably due to its failure to penetrate into HRPE cells. Accordingly, neither superoxide dismutase nor N(G)-monomethyl-L-arginine had significant effects on HRPE cell apoptosis or caspase-3 activation. Our results suggest that activated monocytes may induce ROM in HRPE cells through cell-to-cell contact, in part via CD18 and ICAM-1, and promote HRPE cell apoptosis. These mechanisms may compromise HRPE cell function and survival in a variety of retinal diseases.

Choroidal neovascular membrane inhibition in a laser treated rat model with intraocular sustained release triamcinolone acetonide microimplants

AIM

To determine if intravitreal microimplants containing triamcinolone acetonide (TAAC) inhibit experimental fibrovascular proliferation (FVP) induced by laser trauma in a rat as a model of choroidal neovascular membranes (CNVMs).

METHODS

20 anaesthetised male Brown Norway rats received a series of eight krypton red laser lesions per eye (647 nm, 0.05 s, 50 micro m, 150 mW). Three types of sterilised TAAC microimplant designs were evaluated: implant A consisting of 8.62% TAAC/20% polyvinyl alcohol (PVA) matrix (by dry weight); implant B consisting of 3.62% TAAC/20% PVA matrix; and implant C consisting of a dual 8.62% TAAC/20% PVA matrix design combined with a central core (0.5 mm) of compressed TAAC to extend the implant release time. For each animal studied, one eye received one of the three aforementioned TAAC implant designs, while the fellow eye received a control implant consisting of PVA but without TAAC. The animals were sacrificed at day 35 and ocular tissues were processed for histological analysis. Serial histological specimens were methodically assessed in a masked fashion to analyse each laser lesion for the presence or absence of FVP; maximum FVP thickness for each lesion was measured from the choriocapillaris.

RESULTS

All three types of TAAC implants inhibited FVP relative to controls in a statistically significant fashion. In the eyes that received implant A (n = 8), the mean thickness of the recovered lesions (n = 36) measured 32 (SD 22) micro m, compared to 52 (30) micro m (p <0.005) for the recovered lesions (n = 40) from the fellow control eyes. In the eyes that received implant B (n = 6), the mean thickness of the recovered lesions (n = 31) measured 28 (15) micro m, compared to 50 (29) micro m (p <0.001) for the lesions (n = 19) recovered from the fellow control eyes. In the eyes that received implant C (n = 6), the mean thickness of the recovered lesions (n = 21) measured 39 (24) micro m, compared to 65 (30) micro m (p <0.001) for the lesions (n = 39) recovered from the fellow control eyes.

CONCLUSIONS

All three of the tested TAAC microimplant designs produced potent inhibition of FVP in a rat model of CNVMs. There were no differences in inhibition of FVP between the three different types of implants evaluated. This study provides evidence that: (1) corroborates previous investigations that propose TAAC as a potential treatment for CNVMs in humans, and (2) demonstrates TAAC can be effectively delivered via long acting sustained release intraocular microimplants. It should be noted, however, that the FVP observed in this rat laser trauma may not reflect the CNVM observed in human with exudative age related macular degeneration (AMD).

Age-related macular degeneration: etiology, pathogenesis, and therapeutic strategies

Age-related macular degeneration is the principal cause of registered legal blindness among those aged over 65 in the United States, western Europe, Australia, and Japan. Despite intensive research, the precise etiology of molecular events that underlie age-related macular degeneration is poorly understood. However, investigations on parallel fronts are addressing this prevalent public health problem. Sophisticated biochemical and biophysical techniques have refined our understanding of the pathobiology of drusen, geographic atrophy, and retinal pigment epithelial detachments. Epidemiological identification of risk factors has facilitated an intelligent search for underlying mechanisms and fueled clinical investigation of behavior modification. Gene searches have not only brought us to the cusp of identifying the culpable gene loci in age-related macular degeneration, but also localized genes responsible for other macular dystrophies. Recent and ongoing investigations, often cued by tumor biology, have revealed an important role for various growth factors, particularly in the neovascular form of the condition. Transgenic and knockout studies have provided important mechanistic insights into the development of choroidal neovascularization, the principal cause of vision loss in age-related macular degeneration. This in turn has culminated in preclinical and clinical trials of directed molecular interventions.

Expression of extradomain-B-containing fibronectin in subretinal choroidal neovascular membranes

PURPOSE

To investigate the presence of the fibronectin isoform containing the extradomain B (B-FN), a marker-protein of angiogenesis, in surgically excised human choroidal neovascular membranes (CNVM) to evaluate whether B-FN could be used as a therapeutic target for specific antibody-photosensitizer immunoconjugates.

DESIGN

Laboratory investigation.

METHODS

The setting was an institutional practice. The study population consisted of 15 eyes (15 patients) with CNVM undergoing membrane excision (four eyes with age-related macular degeneration, seven with pathologic myopia and four with multifocal choroiditis). The control group consisted of eight eye bank eyes (four subjects) without choroidal neovascularization. Light microscopic immunohistochemistry on cryostat sections of tissues was obtained. B-FN was detected by a human recombinant antibody, CGS-1, and compared with immunostaining for endothelial cells with factor VIII-related antigen. The main outcome measure was the presence of CGS-1 positively stained cells or areas of the extracellular matrix. Staining of CGS-1 was scored on a scale from 0 to 3.

RESULTS

Fourteen of 15 neovascular membranes stained strongly with CGS-1 (score 2 or 3). One membrane from a patient with pathologic myopia was negatively stained (score 0). CGS-1 positive staining was detected around endothelial cells and in the extracellular matrix of CNVMs. The retina of eyes without choroidal neovascularization was negative with CGS-1 in all eight donor eyes, while the choroid contained some weakly CGS-1 positive cells (score 0 and 1, respectively).

CONCLUSIONS

The extradomain B is abundantly expressed in CNVMs, but its expression is more restricted in eyes harboring no apparent choroidal neovascularization. In the future, B-FN might serve as a target for the delivery of antibody-photosensitizer immunoconjugates to newly developed vessels to enhance the selectivity of photodynamic therapy.