VEGF-A regulates the expression of VEGF-C in human retinal pigment epithelial cells

Phase 1b Dose Escalation Study of Sozinibercept Inhibition of Vascular Endothelial Growth Factors C and D With Aflibercept for Diabetic Macular Edema

Purpose

Sozinibercept inhibits vascular endothelial growth factors (VEGFs) C and D. This study evaluated outcomes following switching from anti-VEGF-A monotherapy to intravitreal injections of three dose levels of sozinibercept in combination with aflibercept in patients with diabetic macular edema (DME).

Methods

A phase 1b, open-label, multicenter dose-escalation study with a 24-week follow-up. Patients received 3 loading doses of aflibercept (2 mg) in combination with sozinibercept (0.3, 1, or 2 mg) once every 4 weeks and were followed through week 24. The primary endpoint was safety, and secondary endpoints included mean change from baseline in best-corrected visual acuity (BCVA) and anatomic changes on imaging.

Results

Nine patients received sozinibercept in combination with aflibercept after a mean (SD) of 6.3 (2.4) injections of previous anti-VEGF-A. Sozinibercept combination therapy was well tolerated with no dose-limiting toxicities. Mean change in BCVA at week 12 was +7.7 letters (95% confidence interval [CI], 2-13.3) from baseline (65 letters [SD 5.5]) with a dose response for increasing doses of sozinibercept. At week 12, central subfield thickness (CST) was decreased by -71 µm (95% CI, -117 to -26) from baseline (434 µm [SD 58]), and 6 of 9 (67%) patients had a ≥50% reduction in excess foveal thickness.

Conclusions

In prior-treated patients with center-involved DME, switching to sozinibercept in combination with aflibercept was well tolerated with improved visual and anatomic outcomes.

Translational Relevance

This first-in-human study builds upon basic research by providing safety and preliminary efficacy of sozinibercept (anti-VEGF-C/-D) in combination with aflibercept for DME.

Single-cell transcriptomics analysis of proliferative diabetic retinopathy fibrovascular membranes reveals AEBP1 as fibrogenesis modulator

The management of preretinal fibrovascular membranes, a devastating complication of advanced diabetic retinopathy (DR), remains challenging. We characterized the molecular profile of cell populations in these fibrovascular membranes to identify potentially new therapeutic targets. Preretinal fibrovascular membranes were surgically removed from patients and submitted for single-cell RNA-Seq (scRNA-Seq). Differential gene expression was implemented to define the transcriptomics profile of these cells and revealed the presence of endothelial, inflammatory, and stromal cells. Endothelial cell reclustering identified subclusters characterized by noncanonical transcriptomics profile and active angiogenesis. Deeper investigation of the inflammatory cells showed a subcluster of macrophages expressing proangiogenic cytokines, presumably contributing to angiogenesis. The stromal cell cluster included a pericyte-myofibroblast transdifferentiating subcluster, indicating the involvement of pericytes in fibrogenesis. Differentially expressed gene analysis showed that Adipocyte Enhancer-binding Protein 1, AEBP1, was significantly upregulated in myofibroblast clusters, suggesting that this molecule may have a role in transformation. Cell culture experiments with human retinal pericytes (HRP) in high-glucose condition confirmed the molecular transformation of pericytes toward myofibroblastic lineage. AEBP1 siRNA transfection in HRP reduced the expression of profibrotic markers in high glucose. In conclusion, AEBP1 signaling modulates pericyte-myofibroblast transformation, suggesting that targeting AEBP1 could prevent scar tissue formation in advanced DR.

VEGF-targeting drugs for the treatment of retinal neovascularization in diabetic retinopathy

Diabetic retinopathy (DR) is the most common microangiopathic complication of diabetes mellitus, representing a major cause of visual impairment in developed countries. Proliferative DR (PDR) represents the last stage of this extremely complex retinal disease, characterized by the development of neovascularization induced by the abnormal production and release of vascular endothelial growth factor (VEGF). The term VEGF includes different isoforms; VEGF-A represents one of the most important pathogenic factors of DR. Anti-VEGF intravitreal therapies radically changed the outcome of DR, due to combined anti-angiogenic and anti-edematous activities. Nowadays, several anti-VEGF molecules exist, characterized by different pharmacological features and duration. With respect to PDR, although anti-VEGF treatments represented a fundamental step forward in the management of this dramatic complication, a big debate is present in the literature regarding the role of anti-VEGF as substitute of panretinal photocoagulation or if these two approaches may be used in combination. In the present review, we provided an update on VEGF isoforms and their role in DR pathogenesis, on current anti-VEGF molecules and emerging new drugs, and on the current management strategies of PDR. There is an overall agreement regarding the relative advantage provided by anti-VEGF, especially looking at the management of PDR patients requiring vitrectomy, with respect to laser. Based on the current data, laser approaches might be avoided when a perfectly planned anti-VEGF therapeutic strategy can be adopted. Conversely, laser treatment may have a role for those patients unable to guarantee enough compliance to anti-VEGF injections.Key messagesVEGF increased production, stimulated by retinal hypoperfusion and ischaemia, is a major pathogenic factor of neovascular complication onset in diabetic retinopathy and of DR stages progression.Nowadays, several anti-VEGF molecules are available in clinical practice and other molecules are currently under investigation. Each anti-VEGF molecule is characterized by different targets and may interact with multiple biochemical pathways within the eye.All the data agreed in considering anti-VEGF molecules as a first line choice for the management of diabetic retinopathy. Laser treatments may have a role in selected advanced cases and for those patients unable to guarantee enough compliance to intravitreal treatments schemes.

Effect of hydroxychloroquine on antiphospholipid antibodies-inhibited endometrial angiogenesis

BACKGROUND

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombotic events and/or pregnancy morbidity (≥3 recurrent early miscarriage or fetal death or a prematurity <34 weeks of gestation) with persistently positive antiphospholipid antibodies (aPLs). It is reported that aPLs damage the placental tissue by binding to β2-glycoprotein I (β2GPI) on the surface of trophoblast and endothelial cells. Hydroxychloroquine (HCQ) is considered to be beneficial in the treatment of obstetrical APS and shown to restore the aPL-inhibited invasion and differentiation of trophoblast. However, not enough evidence exists regarding the effect of HCQ on endometrial angiogenesis. The aim of our study was to assess whether HCQ has an effect on aPL-inhibited endothelial angiogenesis.

METHODS

In this research, to explore the effect of HCQ for angiogenesis, we investigated: (1) Human umbilical vein endothelial cells (HUVECs) viability by CCK-8; (2) HUVECs migration by wound healing; (3) HUVEC angiogenesis by Matrigel assay in vitro; (4) mRNA expression of MMP-2 and VEGF by real-time quantitative Polymerase Chain Reaction (RT-PCR); (5) protein expression of VEGF, MMP-2 by western blot.

RESULTS

We found that HCQ treatment significantly restored the expression of aPL-inhibited VEGF and MMP-2. HCQ restored aPL-inhibited HUVEC proliferation, migration, and angiogenesis in vitro.

CONCLUSION

In conclusion, aPLs inhibit HUVECs angiogenesis, however, HCQ can restore the effect of aPL-inhibited HUVECs migration and angiogenesis in vitro, demonstrating its beneficial therapeutic role in obstetrical APS.

Role of VEGFR2 in Mediating Endoplasmic Reticulum Stress Under Glucose Deprivation and Determining Cell Death, Oxidative Stress, and Inflammatory Factor Expression

Retinal pigment epithelium (RPE), a postmitotic monolayer located between the neuroretina and choroid, supports the retina and is closely associated with vision loss diseases such as age-related macular degeneration (AMD) upon dysfunction. Although environmental stresses are known to play critical roles in AMD pathogenesis and the roles of other stresses have been well investigated, glucose deprivation, which can arise from choriocapillary flow voids, has yet to be fully explored. In this study, we examined the involvement of VEGFR2 in glucose deprivation-mediated cell death and the underlying mechanisms. We found that VEGFR2 levels are a determinant for RPE cell death, a critical factor for dry AMD, under glucose deprivation. RNA sequencing analysis showed that upon VEGFR2 knockdown under glucose starvation, endoplasmic reticulum (ER) stress and unfolded protein response (UPR) are reduced. Consistently, VEGFR2 overexpression increased ER stress under the same condition. Although VEGFR2 was less expressed compared to EGFR1 and c-Met in RPE cells, it could elicit a higher level of ER stress induced by glucose starvation. Finally, downregulated VEGFR2 attenuated the oxidative stress and inflammatory factor expression, two downstream targets of ER stress. Our study, for the first time, has demonstrated a novel role of VEGFR2 in RPE cells under glucose deprivation, thus providing valuable insights into the mechanisms of AMD pathogenesis and suggesting that VEGFR2 might be a potential therapeutic target for AMD prevention, which may impede its progression.

Picolinafen exerts developmental toxicity via the suppression of oxidative stress and angiogenesis in zebrafish embryos

Picolinafen, a phytoene desaturase-inhibiting herbicide, has been used since 2001 to control the growth of broadleaf weeds. Picolinafen has lower solubility and volatility, and shows lower toxicity to non-target insect species than other types of herbicide. Although picolinafen has been detected in lakes near urban environments and induces chronic toxicity in the mammals, birds, and some aquatic organisms, no study has investigated the toxicity or mode of action of picolinafen in zebrafish. In this study, we demonstrated the lethality and acute LC₅₀ value of picolinafen towards zebrafish embryos. Picolinafen hampered the development of embryos by the induction of morphological abnormalities via apoptosis. Additionally, picolinafen suppressed the generation of reactive oxygen species and angiogenesis. Also, the angiogenesis related genes, flt1 and flt4 mRNA expression was decreased in zebrafish embryos. This study provides a mechanistic understanding of the developmental toxicity of picolinafen in vertebrates.

Induced Expression of VEGFC, ANGPT, and EFNB2 and Their Receptors Characterizes Neovascularization in Proliferative Diabetic Retinopathy

Purpose

To investigate whole transcriptional differences between proliferative diabetic retinopathy (PDR) neovascular membranes (NVMs) and retinas, and the regulatory genes participating in retinal neovascularization in PDR.

Methods

We used high-throughput sequencing technology to capture the whole-genome gene expression levels of all participants, including 23 patients with PDR or branch retinal vein occlusion (BRVO), 3 normal retinal samples, and 2 retinal samples from type II diabetic (T2D) eyes by donation, followed by analyses of expression patterns using bioinformatics methods, then validation of the data by in situ hybridization and Western blotting.

Results

We showed that transcriptional profiles of the NVMs were distinct from those of the retinas. Angiogenesis growth factors VEGFC, ANGPT1, ANGPT2, and EFNB2, and their receptors FLT4, TIE1, TIE2, and EPHB4, respectively, were overexpressed. Expression of VEGFA was highly upregulated in T2D retina, but low in the NVMs, while angiogenesis transcription factors, including ETS1 and ERG, were coordinately upregulated in NVMs.

Conclusions

This study described a PDR neovascularization model in which pathological retina-secreted vascular endothelial growth factor A (VEGFA) enhanced the expression of a set of angiogenesis transcription factors and growth factors, to cooperatively induce the retinal neovascularization. Based on these results, novel potential therapeutic targets and biomarkers for PDR treatment and diagnosis are suggested.

Intra-individual variability and circadian rhythm of vascular endothelial growth factors in subjects with normal glucose tolerance and type 2 diabetes

Increased levels of systemic vascular endothelial growth factors (VEGFs) in patients with diabetes are associated with increased risk of microvessel disease. On the other hand, low VEGF levels after intravitreal antibody application may be associated with acute cardiovascular complications and treatment failure. Individual levels of systemic VEGF vary in a wide range depending on analytical methods and quality of diabetes control. So far only limited information exists on intraindividual fluctuations over longer periods and circadian rhythms. We analysed the intraindividual variance of VEGF-A, VEGF-C and placental growth factor (PLGF) in CTAD (citrate-theophylline-adenine-dipyridamol) plasma as well as VEGF-A in serum over a period of 6 months in patients with stable controlled type 2 diabetes (10 M, 10 F) and age and sex matched subjects with normal glucose tolerance (NGT). Furthermore, circadian levels of VEGFs were controlled hourly from 7:30 a.m. to 7:30 p.m. under standardized metabolic ward conditions. In addition, the relationship to metabolic, hormonal and inflammatory biomarkers was analyzed. VEGF-A, VEGF-C and PLGF remained stable in plasma and VEGF-A in serum over 6 months in both groups. No circadian change was observed in VEGF-A serum and plasma concentrations. A minor decrease of VEGF-C plasma levels was evident after 5 p.m. in both groups and a significant peak of PLGF concentrations occurred after lunch, which was more pronounced in T2DM. In multivariate analysis, only serum VEGF-A correlated to diabetes duration, whereas VEGF-C only correlated to HbA1c and fasting blood glucose. We did not observe significant intraindividual variances for VEGF-A in serum and VEGF-A, VEGF-C and PLGF in CTAD plasma over a period of 6 months. Taken together, a single morning measurement of systemic VEGF levels after 7:30 am appears to be a reliable parameter for the individual risk associated with abnormal VEGF concentrations in blood.

Trial Registration: NCT02325271

Osmotic induction of placental growth factor in retinal pigment epithelial cells in vitro: contribution of NFAT5 activity

One risk factor of neovascular age-related macular degeneration is systemic hypertension; hypertension is mainly caused by extracellular hyperosmolarity after consumption of dietary salt. In retinal pigment epithelial (RPE) cells, high extracellular osmolarity induces vascular endothelial growth factor (VEGF)-A (Hollborn et al. in Mol Vis 21:360-377, 2015). The aim of the present study was to determine whether extracellular hyperosmolarity and chemical hypoxia trigger the expression of further VEGF family members including placental growth factor (PlGF) in human RPE cells. Hyperosmotic media were made up by addition of 100 mM NaCl or sucrose. Chemical hypoxia was induced by CoCl2. Gene expression was quantified by real-time RT-PCR, and secretion of PlGF-2 was investigated with ELISA. Nuclear factor of activated T cell 5 (NFAT5) was depleted using siRNA. Extracellular hyperosmolarity triggered expression of VEGF-A, VEGF-D, and PlGF genes, and secretion of PlGF-2. Hypoosmolarity decreased PlGF gene expression. Hypoxia induced expression of VEGF-A, VEGF-B, VEGF-D, and PlGF genes. Extracellular hyperosmolarity and hypoxia produced additive PlGF gene expression. Both hyperosmolarity and hypoxia induced expression of KDR and FLT-4 receptor genes, while hyperosmolarity caused neuropilin-2 and hypoxia neuropilin-1 gene expression. The hyperosmotic, but not the hypoxic, PlGF gene expression was in part mediated by NFAT5. The expression of PlGF in RPE cells depends on the extracellular osmolarity. The data suggest that high consumption of dietary salt may exacerbate the angiogenic response of RPE cells in the hypoxic retina via transcriptional activation of various VEGF family member genes.

Response to anti-VEGF-A treatment of retinal pigment epithelial cells in vitro

PURPOSE

The neovascular or wet form of age-related macular degeneration is characterized by the growth of abnormal blood vessels in the retina stimulated by vascular endothelial growth factors (VEGF). In the last decade, several anti-VEGF drugs have been developed for treating neovascular diseases of the eyes. This study was conducted to compare the effects of 2 anti-VEGF-A drugs, ranibizumab and aflibercept, on the expression and secretion of VEGF family members in retinal pigment epithelial cells (RPE) in vitro.

METHODS

ARPE-19 cells were exposed for 24 hours to ranibizumab or aflibercept at clinical dose concentration. Cell viability and expression and secretion of VEGF-A, VEGF-B, VEGF-C, and placental growth factor (PlGF) were evaluated respectively by real-time polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

Ranibizumab and aflibercept did not affect ARPE-19 cell viability after 24 hours of treatment. Ranibizumab increased expression of VEGF-A and PlGF. On the contrary, expression and secretion of VEGF-C was decreased by ranibizumab. PlGF secretion was not affected by ranibizumab. Aflibercept strongly increased VEGF-A and PlGF expression but reduced their detection on the culture media, and decreased expression and secretion of VEGF-C. No effect on expression and secretion of VEGF-B was observed after exposure to these drugs.

CONCLUSIONS

Ranibizumab and aflibercept exert similar effects on VEGF expression and secretion, leading to establishing an antiangiogenic environment. Increased VEGF-A expression observed in RPE cells treated with these drugs suggests a compensatory response of the cells to the lack of VEGF-A.

Two Bioactive Molecular Weight Fractions of a Conditioned Medium Enhance RPE Cell Survival on Age-Related Macular Degeneration and Aged Bruch's Membrane

PURPOSE

To characterize molecular weight fractions of bovine corneal endothelial cell conditioned medium (CM) supporting retinal pigment epithelium (RPE) cell survival on aged and age-related macular degeneration (AMD) Bruch's membrane.

METHODS

CM was subject to size separation using centrifugal filters. Retentate and filtrate fractions were tested for bioactivity by analyzing RPE survival on submacular Bruch's membrane of aged and AMD donor eyes and behavior on collagen I-coated tissue culture wells. Protein and peptide composition of active fractions was determined by mass spectrometry.

RESULTS

Two bioactive fractions, 3-kDa filtrate and a 10-50-kDa fraction, were necessary for RPE survival on aged and AMD Bruch's membrane. The 3-kDa filtrate, but not the 10-50-kDa fraction, supported RPE growth on collagen 1-coated tissue culture plates. Mass spectrometry of the 10-50-kDa fraction identified 175 extracellular proteins, including growth factors and extracellular matrix molecules. Transforming growth factor (TGF)β-2 was identified as unique to active CM. Peptides representing 29 unique proteins were identified in the 3-KDa filtrate.

CONCLUSIONS

These results indicate there is a minimum of two bioactive molecules in CM, one found in the 3-kDa filtrate and one in the 10-50-kDa fraction, and that bioactive molecules in both fractions must be present to ensure RPE survival on Bruch's membrane. Mass spectrometry analysis suggested proteins to test in future studies to identify proteins that may contribute to CM bioactivity.

TRANSLATIONAL RELEVANCE

Results of this study are the first steps in development of an adjunct to cell-based therapy to ensure cell transplant survival and functionality in AMD patients.

Hypoxia and Dark Adaptation in Diabetic Retinopathy: Interactions, Consequences, and Therapy

In diabetes, retinal blood flow is compromised, and retinal hypoxia is likely to be further intensified during periods of darkness. During dark adaptation, rod photoreceptors in the outer retina are maximally depolarized and continuously release large amounts of the neurotransmitter glutamate-an energetically demanding process that requires the highest oxygen consumption per unit volume of any tissue of the body. In complete darkness, even more oxygen is consumed by the outer retina, producing a steep fall in the retinal oxygen tension curve which reaches a nadir at the depth of the mitochondrial-rich rod inner segments. In contrast to the normal retina, the diabetic retina cannot meet the added metabolic load imposed by the dark-adapted rod photoreceptors; this exacerbates retinal hypoxia and stimulates the overproduction of vascular endothelial growth factor (VEGF). The use of nocturnal illumination to prevent dark adaptation, specifically reducing the rod photoreceptor dark current, should ameliorate diabetic retinopathy.

Nornicotine and Nicotine Induced Neovascularization via Increased VEGF/PEDF Ratio

PURPOSE

The purpose of the current study was to evaluate the influences of nornicotine and nicotine (NT) in cigarette smoke on the expression of vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in retinal pigment epithelium cells and human umbilical vein endothelial cells (HUVECs). Furthermore, the angiogenic behaviors of endothelial cells under nornicotine and NT treatment were assessed by using in vitro methods.

METHODS

ARPE-19 cells and HUVECs were treated with different concentrations of either nornicotine or NT for different periods of time. The cell proliferative effect was investigated by using the method of MTT analysis. HUVEC migration and tube formation were assessed by using the scratch assay and Matrigel models. The expressions of VEGF and PEDF gene and protein in both types of cells were examined by real-time RT-PCR and Western blot.

RESULTS

There was no proliferation of ARPE-19 cells following treatment with various concentrations of nornicotine or NT. In contrast, nornicotine or NT significantly stimulated HUVEC proliferation, migration and tube formation. Nornicotine and NT upregulated the expression of VEGF but suppressed the expression of PEDF at both mRNA and protein levels in a dose- and time-dependent manner in ARPE-19 cells and HUVECs.

CONCLUSIONS

Our results demonstrate that nornicotine and NT promoted endothelial cellular proliferation, migration and tube formation of HUVECs in vitro. These effects might be partly due to simultaneous modulation of VEGF/PEDF signaling in ARPE-19 cells and HUVECs.

Emerging roles for nuclear receptors in the pathogenesis of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of vision loss in the elderly in the Western world. Over the last 30 years, our understanding of the pathogenesis of the disease has grown exponentially thanks to the results of countless epidemiology, genetic, histological, and biochemical studies. This information, in turn, has led to the identification of multiple biologic pathways potentially involved in development and progression of AMD, including but not limited to inflammation, lipid and extracellular matrix dysregulation, and angiogenesis. Nuclear receptors are a superfamily of transcription factors that have been shown to regulate many of the pathogenic pathways linked with AMD and as such they are emerging as promising targets for therapeutic intervention. In this review, we will present the fundamental phenotypic features of AMD and discuss our current understanding of the pathobiological disease mechanisms. We will introduce the nuclear receptor superfamily and discuss the current literature on their effects on AMD-related pathophysiology.

Vascular endothelial growth factor-C secretion is increased by advanced glycation end-products: possible implication in ocular neovascularization

PURPOSE

Neovascularization is a common complication of many degenerative and vascular diseases of the retina. Advanced glycation end-products (AGEs) have a pathologic role in the development of retinal neovascularization, mainly for their ability in upregulating vascular endothelial growth factor-A (VEGF-A) secretion. The aim of this study was to investigate whether AGEs are able to modulate the secretion of VEGF-C, another angiogenic factor that increases the effect of VEGF-A.

METHODS

A human retinal pigment epithelial cell line (ARPE-19) and human endothelial vascular cell line (HECV) cells were cultured for 24 h in presence of AGEs, and then mRNA expression of VEGF-C was analyzed with reverse transcription-polymerase chain reaction (RT-PCR). To verify whether AGEs-induced VEGF secretion is mediated by RAGE (Receptor for AGEs), RAGE expression was depleted using the small interfering RNA method. To investigate whether VEGF-A is involved in upregulating VEGF-C secretion, the cells were cultured for 24 h in the presence of bevacizumab, a monoclonal antibody against VEGF-A, alone or in combination with AGEs. VEGF-A and VEGF-C levels in the supernatants of the treated cells were evaluated with enzyme-linked immunosorbent assay.

RESULTS

Exposure to AGEs significantly increased VEGF-C gene expression in ARPE-19 cells. AGEs-induced VEGF-C secretion was upregulated in retinal pigment epithelium (RPE) and endothelial cells. Downregulation of RAGE expression decreased VEGF-A secretion in cell models, and increased VEGF-C secretion in ARPE-19 cells. Adding bevacizumab to the culture medium upregulated constitutive VEGF-C secretion but did not affect AGEs-induced VEGF-C secretion.

CONCLUSIONS

These findings suggest that AGEs take part in the onset of retinal neovascularization, not only by modulating VEGF-A but also by increasing VEGF-C secretion. In addition, our results suggest that VEGF-C may compensate for treatments that reduce VEGF-A.

Effect of subconjunctival and intraocular bevacizumab injections on corneal neovascularization in a mouse model

PURPOSE

This study sought to evaluate the efficacy of bevacizumab (Avastin), an anti-VEGF agent, in the reduction of corneal neovascularization in a rodent model, and compare between the effect of intraocular and subconjunctival injection.

METHODS

Corneal neovascularization was induced by application of a mixture of 75% silver nitrate and 25% potassium nitrate to the corneal center of the right eye of 125 mice. Immediately thereafter, 75 eyes were treated with subconjunctival, anterior chamber, or intravitreal injection of bevacizumab. The remaining mice served as a control. The groups were compared at different postoperative time points for percentage area of neovascularization evaluated by digital photos, the presence of corneal stromal vascular endothelial cells studied by immunohistochemical staining, and VEGF levels measured by real-time PCR.

RESULTS

In the untreated eyes, percentage area of neovascularization increased from 11.3 +/- 7% on day 2 to 20 +/- 8.9% on day 4, 47 +/- 25.4% on day 8, and 51 +/- 24.7% on day 10. The percentage area of neovascularization following subconjunctival injection was 7 +/- 2.9% on day 2, 15.7 +/- 6% on day 4, 32.2 +/- 15.2% on day 8, and 39.7 +/- 14.5% on day 10. The percentage area of neovascularization following anterior chamber injection was 14.4 +/- 3% on day 2, 16.5 +/- 6.3% on day 4, 26.3 +/- 6.5% on day 8, and 19.8 +/- 1.2% on day 10. The percentage area of neovascularization following intravitreal injection was 11 +/- 2.5% on day 2, 14.7 +/- 5% on day 4, 23.5 +/- 6.5% on day 8, and 24.2 +/- 14.9% on day 10.

CONCLUSIONS

Bevacizumab injections partially inhibit the growth of corneal neovascularization induced by acute chemical injury in a mouse model. The intraocular routes of injection were found to be the most effective, and the subconjunctival route of injection yielded the earliest peak response.

FOXO1 plays an essential role in apoptosis of retinal pericytes

PURPOSE

An early and significant event in diabetic retinopathy is the loss of retinal microvascular pericytes. Studies were performed to investigate pathways through which an advanced glycation endproduct and tumor necrosis factor (TNF)-alpha stimulate apoptosis in retinal pericytes through the activation of the pro-apoptotic transcription factor Forkhead box O1 (FOXO1).

METHODS

Human retinal pericytes were stimulated by carboxymethyllysine (CML)-collagen, an advanced glycation endproduct, or TNF-alpha in vitro. Apoptosis was assessed by measuring cytoplasmic histone-associated DNA. The role of FOXO1 was examined by RNA interference (RNAi), and specific inhibitors were used to investigate the role of p38 and Jun N-terminal kinase mitogen-activated protein kinase (JNK MAP) kinases, Akt, and nuclear factor kappa B (NF-kappaB). Caspase-3 activity was measured with a luminescent substrate, and FOXO1 DNA-binding activity was measured by electrophoretic mobility shift assay (EMSA).

RESULTS

TNF-alpha and CML-collagen but not control collagen stimulated apoptosis, caspase-3 activity, and FOXO1 DNA-binding activity in pericytes. Silencing FOXO1 by small interfering RNA prevented apoptosis of pericytes in response to both TNF-alpha and CML-collagen. By use of specific inhibitors, we demonstrated that both FOXO1 activation and subsequent apoptosis was mediated, in part, by p38 and JNK MAP kinases. In contrast Akt and NF-kappaB inhibitors had the opposite effect on pericyte apoptosis.

CONCLUSIONS

The results demonstrate pathways through which two different mediators, TNF-alpha and an advanced glycation endproduct, can induce pericyte apoptosis through activation of the transcription factor FOXO1.

RPE transplantation and its role in retinal disease

Retinal pigment epithelial (RPE) transplantation aims to restore the subretinal anatomy and re-establish the critical interaction between the RPE and the photoreceptor, which is fundamental to sight. The field has developed over the past 20 years with advances coming from a large body of animal work and more recently a considerable number of human trials. Enormous progress has been made with the potential for at least partial restoration of visual function in both animal and human clinical work. Diseases that have been treated with RPE transplantation demonstrating partial reversal of vision loss include primary RPE dystrophies such as the merTK dystrophy in the Royal College of Surgeons (RCS) rat and in humans, photoreceptor dystrophies as well as complex retinal diseases such as atrophic and neovascular age-related macular degeneration (AMD). Unfortunately, in the human trials the visual recovery has been limited at best and full visual recovery has not been demonstrated. Autologous full-thickness transplants have been used most commonly and effectively in human disease but the search for a cell source to replace autologous RPE such as embryonic stem cells, marrow-derived stem cells, umbilical cord-derived cells as well as immortalised cell lines continues. The combination of cell transplantation with other modalities of treatment such as gene transfer remains an exciting future prospect. RPE transplantation has already been shown to be capable of restoring the subretinal anatomy and improving photoreceptor function in a variety of retinal diseases. In the near future, refinements of current techniques are likely to allow RPE transplantation to enter the mainstream of retinal therapy at a time when the treatment of previously blinding retinal diseases is finally becoming a reality.