Intravitreal Administration of Stanniocalcin-1 Rescues Photoreceptor Degeneration with Reduced Oxidative Stress and Inflammation in a Porcine Model of Retinitis Pigmentosa.

PURPOSE: To investigate the effect of stanniocalcin-1 (STC-1), a secreted polypeptide exhibiting multiple functions in cell survival and death, on photoreceptor degeneration in a porcine model of retinitis pigmentosa (RP). METHODS: P23H transgenic pigs (TG P23H) and wild-type hybrid littermates were obtained from the National Swine Resource and Research Center. Human recombinant STC-1 was injected intravitreally every 2 weeks from postnatal day 15 (P15) to P75. The contralateral eye was injected with balanced salt solution as a control. Electroretinography (ERG) and spectral domain optical coherence tomography (SD-OCT) were performed to evaluate retinal function and morphology in vivo at P90. Retinal tissue was collected for histologic analysis and molecular assays to evaluate the antioxidative and anti-inflammatory mechanisms by which STC-1 may rescue photoreceptor degeneration. RESULTS: Intravitreal injection of STC-1 improved retinal function in TG P23H pigs with increased photopic and flicker ERG a- and b-wave amplitudes. Greater integrity of the ellipsoid zone (EZ) band on SD-OCT and morphologic rescue with preservation of cone photoreceptors were observed in STC-1-treated TG P23H pigs. STC-1 altered gene expression in TG P23H pig retina on microarray analysis and increased photoreceptor specific gene expression by reverse transcription-polymerase chain reaction analysis. STC-1 significantly decreased oxidative stress and the expressions of NLRP3 inflammasome, cleaved caspase-1, and IL-1ß in TG P23H pig retina. CONCLUSIONS: Intravitreal administration of STC-1 enhances cone photoreceptor function, improves EZ integrity, and reduces retinal degeneration through antioxidative and anti-inflammatory effects in a large animal (pig) model of the most common form of autosomal dominant RP in the United States.

Newly Identified Peptide, Peptide Lv, Promotes Pathological Angiogenesis.

Background We recently discovered a small endogenous peptide, peptide Lv, with the ability to activate vascular endothelial growth factor receptor 2 and its downstream signaling. As vascular endothelial growth factor through vascular endothelial growth factor receptor 2 contributes to normal development, vasodilation, angiogenesis, and pathogenesis of various diseases, we investigated the role of peptide Lv in vasodilation and developmental and pathological angiogenesis in this study. Methods and Results The endothelial cell proliferation, migration, and 3-dimensional sprouting assays were used to test the abilities of peptide Lv in angiogenesis in vitro. The chick chorioallantoic membranes and early postnatal mice were used to examine its impact on developmental angiogenesis. The oxygen-induced retinopathy and laser-induced choroidal neovascularization mouse models were used for in vivo pathological angiogenesis. The isolated porcine retinal and coronary arterioles were used for vasodilation assays. Peptide Lv elicited angiogenesis in vitro and in vivo. Peptide Lv and vascular endothelial growth factor acted synergistically in promoting endothelial cell proliferation. Peptide Lv-elicited vasodilation was not completely dependent on nitric oxide, indicating that peptide Lv had vascular endothelial growth factor receptor 2/nitric oxide-independent targets. An antibody against peptide Lv, anti-Lv, dampened vascular endothelial growth factor-elicited endothelial proliferation and laser-induced vascular leakage and choroidal neovascularization. While the pathological angiogenesis in mouse eyes with oxygen-induced retinopathy was enhanced by exogenous peptide Lv, anti-Lv dampened this process. Furthermore, deletion of peptide Lv in mice significantly decreased pathological neovascularization compared with their wild-type littermates. Conclusions These results demonstrate that peptide Lv plays a significant role in pathological angiogenesis but may be less critical during development. Peptide Lv is involved in pathological angiogenesis through vascular endothelial growth factor receptor 2-dependent and -independent pathways. As anti-Lv dampened the pathological angiogenesis in the eye, anti-Lv may have a therapeutic potential to treat pathological angiogenesis.

Intravitreal Stanniocalcin-1 Enhances New Blood Vessel Growth in a Rat Model of Laser-Induced Choroidal Neovascularization.

Purpose: The purpose of this study was to investigate the impact of stanniocalcin-1 (STC-1), a photoreceptor-protective glycoprotein, on the development of choroidal neovascularization (CNV) in relation to VEGF and its main receptor (VEGFR2) expression after laser injury. Methods: In rats, CNV was induced by laser photocoagulation in both eyes, followed by intravitreal injection of STC-1 in the right eye and vehicle or denatured STC-1 injection in the left eye as control. Two weeks after laser injury, fundus autofluorescence (FAF) imaging and fundus fluorescein angiography (FFA) were performed. Fluorescein leakage from CNV was graded using a defined scale system. The size of CNV was quantified with spectral domain optical coherence tomography (SD-OCT), fluorescein-labeled choroid-sclera flat mounts, and hematoxylin-eosin staining. Protein expressions were evaluated by Western blot. Results: Photocoagulation produced a well-circumscribed area of CNV. With STC-1 treatment, CNV lesions assessed by FAF were increased by 50% in both intensity and area. The CNV lesions were also increased with SD-OCT, flat-mount, and histologic analyses. FFA disclosed enhanced fluorescein leakage in CNV lesions in STC-1 treated eyes. The STC-1 protein was detected in the choroidal tissue and its level was increased with CNV lesions in correlation with VEGF and VEGFR2 expressions. Intravitreal administration of STC-1 significantly increased choroidal expression of both VEGF and VEGFR2 proteins. Conclusions: Chorodial tissue expresses STC-1, which seemingly acts as a stress response protein by enhancing pathological new blood vessel growth in laser-induced CNV. It is likely that STC-1 promotes CNV development via VEGF signaling.

Alterations of Ocular Hemodynamics Impair Ophthalmic Vascular and Neuroretinal Function.

Hypertension is associated with numerous diseases, but its direct impact on the ocular circulation and neuroretinal function remains unclear. Herein, mouse eyes were challenged with different levels of hemodynamic insult via transverse aortic coarctation, which increased blood pressure and flow velocity by 50% and 40%, respectively, in the right common carotid artery, and reduced those parameters by 30% and 40%, respectively, in the left common carotid artery. Blood velocity in the right central retinal artery gradually increased up to 40% at 4 weeks of transverse aortic coarctation, and the velocity in the left central retinal artery gradually decreased by 20%. The fundus and retinal architecture were unaltered by hemodynamic changes. Endothelium-dependent vasodilations to acetylcholine and adenosine were reduced only in right (hypertensive) ophthalmic arteries. Increased cellularity in the nerve fiber/ganglion cell layers, enhanced glial fibrillary acidic protein expression, and elevated superoxide level were found only in hypertensive retinas. The electroretinogram showed decreased scotopic b-waves in the hypertensive eyes and decreased scotopic oscillatory potentials in both hypertensive and hypotensive eyes. In conclusion, hypertension sustained for 4 weeks causes ophthalmic vascular dysfunction, retinal glial cell activation, oxidative stress, and neuroretinal impairment. Although ophthalmic vasoregulation is insensitive to hypotensive insult, the ocular hypoperfusion causes neuroretinal dysfunction.

The expression of the Slit-Robo signal in the retina of diabetic rats and the vitreous or fibrovascular retinal membranes of patients with proliferative diabetic retinopathy.

PURPOSE: The Slit-Robo signal has an important role in vasculogenesis and angiogenesis. Our study examined the expression of Slit2 and its receptor, Robo1, in a rat model of streptozotocin-induced diabetes and in patients with proliferative diabetic retinopathy. METHODS: Diabetes was induced in male Sprague-Dawley rats via a single, intraperitoneal injection of streptozotocin. The rats were sacrificed 1, 3 or 6 months after the injection. The expression of Slit2 and Robo1 in retinal tissue was measured by real-time reverse transcription polymerase chain reaction (RT-PCR), and protein levels were measured by western blotting and immunohistochemistry. Recombinant N-Slit2 protein was used to study the effects of Slit2 on the expression of VEGF in vivo. The concentration of Slit2 protein in human eyes was measured by enzyme-linked immunosorbent assay in 27 eyes with proliferative diabetic retinopathy and 28 eyes in control group. The expression of Slit2, Robo1 and VEGF in the excised human fibrovascular membranes was examined by fluorescence immunostaining and semi-quantitative RT-PCR. RESULTS: The expression of Slit2 and Robo1 in the retina was altered after STZ injection. Recombinant N-Slit2 protein did not increase the retinal VEGF expression. Vitreous concentrations of Slit2 were significantly higher in the study group than in the control group. In the human fibrovascular membranes of the study group, the co-localization of VEGF with the markers for Slit2 and Robo1was observed. The expression of Slit2 mRNA, Robo1 mRNA, and VEGF mRNA was significantly higher in human fibrovascular proliferative diabetic retinopathy membranes than in the control membranes. CONCLUSIONS: The alteration of Slit2 and Robo1 expression in the retinas of diabetic rats and patients with proliferative diabetic retinopathy suggests a role for the Slit-Robo signal in the various stages diabetic retinopathy. Further studies should address the possible involvement of the Slit-Robo signal in the pathophysiological progress of diabetic retinopathy.

Expression of Total Vascular Endothelial Growth Factor and the Anti-angiogenic VEGF 165 b Isoform in the Vitreous of Patients with Retinopathy of Prematurity.

BACKGROUND: This study was to examine the expression of total vascular endothelial growth factor (VEGF) and the anti-angiogenic VEGF 165 b isoform in the vitreous body of retinopathy of prematurity (ROP) patients, and to further study the role of the VEGF splicing in the development of ROP. METHODS: This was a prospective clinical laboratory investigation study. All patients enrolled received standard ophthalmic examination with stage 4 ROP that required vitrectomy to collect the vitreous samples. The control samples were from congenital cataract patients. The expression of total VEGF and the anti-angiogenic VEGF 165 b were measured by enzyme-linked immunosorbent assay. Results were analyzed statistically using nonparametric tests. RESULTS: The total VEGF level was markedly elevated in ROP samples while VEGF 165 b was markedly decreased compared to control group. The relative protein expression level of VEGF 165 b isoform was significantly decreased in ROP patients which were correlated with the ischemia-induced neovascularization. CONCLUSIONS: There was a switch of VEGF splicing from anti-angiogenic to pro-angiogenic family in ROP patients. A specific inhibitor that more selectively targets VEGF 165 and controls the VEGF splicing between pro- and anti-angiogenic families might be a more effective therapy for ROP.

Association of complement factor H gene polymorphisms with age-related macular egeneration susceptibility.

OBJECTIVE: This study was aimed to confirm whether I62V and Y402H polymorphisms of complement factor H (CFH) were risk factors for age-related macular degeneration (AMD). METHOD: 109 AMD patients and 165 AMD-free controls were enrolled in the study. The I62V and Y402H polymorphisms were analyzed by polymerase chain reaction-restriction fragment length of polymorphism (PCR-RFLP). Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by the X2 test to assess the relationship of I62V and Y402H polymorphisms with AMD risk. Analysis of haplotype and stratification by age and smoking status was conducted as well. RESULTS: AA genotype and A allele of I62V polymorphism was significantly associated with increased risk for AMD (OR=3.75, 95% CI=1.70-8.30; OR=1.64, 95% CI=1.14-2.36). For Y402H polymorphism, CT genotype showed strong effects on the occurrence of AMD (OR=2.10, 95% CI=1.04-4.27). Moreover, C allele was also a risk factor for AMD (OR=1.95, 95% CI=1.02-3.72). The haplotypes analysis suggested that the risk for AT haplotype carriers was high, compared with GT haplotype (OR=3.91, 95% CI=2.58-5.94). In addition, we found that smoking status could affect the genotype distribution of Y402H polymorphism (P<0.05). CONCLUSIONS: Our results revealed that CFH polymorphisms I62V and Y402H might be associated with the susceptibility to AMD in Chinese population.

Interleukin-1ß Level Is Increased in Vitreous of Patients with Neovascular Age-Related Macular Degeneration (nAMD) and Polypoidal Choroidal Vasculopathy (PCV).

PURPOSE: To examine the expression of pro-interleukin-1ß (pro-IL-1ß) and interleukin-1ß (IL-1ß) in the vitreous body of patients with neovascular age-related macular degeneration(nAMD), polypoidal choroidal vasculopathy (PCV), proliferative diabetic retinopathy (PDR), retinal vein occlusion (RVO) or Eales' disease to further elucidate the role of IL-1ß and inflammation in the pathogenesis of neovascular retinal disease. DESIGN: Prospective clinical laboratory investigation study. METHODS: All patients enrolled had vitreous hemorrhage due to nAMD, PCV, PDR, RVO or Eales' disease that required vitrectomy. Patients were excluded for any history of active intraocular inflammation, or other ophthalmic surgery besides vitrectomy. Control samples were obtained from patients with idiopathic macular epiretinal membrane. A total of fifty vitreous samples were collected from patient during vitrectomy. Pro-IL-1ß and IL-1ß expression were measured by enzyme-linked immunosorbent assay (ELISA). Results were analyzed statistically using nonparametric tests. RESULTS: Expression of pro-IL-1ß protein was increased by 2.83-fold and 9.19-fold in PCV and nAMD vitreous samples relative to control, respectively. Expression of IL-ß protein was increased by 10-fold and 4.83-fold in PCV and nAMD vitreous samples relative to control, respectively. CONCLUSIONS: Our results demonstrate that expression of pro-IL-1ß and IL-1ß proteins is higher in PCV and nAMD. The roles of pro-IL-1ß and IL-1ß as inflammatory mediators in the development of PCV and nAMD may be associated with photoreceptor degeneration and neovascularization which necessitates further study.

Inhibition of neovascularization and expression shift of pro-/anti-angiogenic vascular endothelial growth factor isoforms after intravitreal bevacizumab injection in oxygen-induced-retinopathy mouse model.

BACKGROUND: Retinopathy of prematurity (ROP) has become one of the leading causes of visual loss in children. Vascular endothelial growth factor A (VEGF-A) is the principal stimulator of angiogenesis. VEGF was differentially spliced from exon 8 to exons 8a and 8b to form two families: the pro-angiogenic VEGFxxx family and the anti-angiogenic VEGFxxxb family. Previous research has shown variable effeteness of bevacizumab in inhibiting retinal neovascularization in ROP. This study aimed to investigate whether the effectiveness of this inhibition depends on the relative ratio of the two VEGF isoforms. METHODS: Intravitreal bevacizumab injection (IVB) was performed in the oxygen-induced-retinopathy (OIR) mice on postnatal day 12 (P12) (intravitreal phosphate buffered saline (PBS) injection as control). The Evans blue perfused retina were used to test the retinal neovascularization-leakage (NVL) area and non-perfusion (NP) area. RESULTS: The retinal NVL and NP area in the IVB group were significantly smaller than the intravitreal PBS injection group (IVP group). On P17, the protein level of total VEGF isoforms was significantly inhibited compared to IVP group (P < 0.05) while VEGF(165)b isoform was slight reduced (P > 0.05). The switch from pro-angiogenic isoforms to anti-angiogenic isoforms after IVB could be found. The relative protein expression of VEGF(165)b isoform was significantly higher in IVB group than in IVP group (P < 0.05) on P17 which was correlated with the reduced ischemia-induced angiogenesis in OIR mice after IVB. CONCLUSIONS: The anti-angiogenic effectiveness might depend on the relative high expression of VEGF(165)b after intravitreal bevacizumab injection. Anti-angiogenic therapy is a more effective therapy for ROP.

Targeting of integrin-linked kinase with small interfering RNA inhibits VEGF-induced angiogenesis in retinal endothelial cells.

BACKGROUND: The pathological angiogenesis in the retina is a major cause of vision loss at all ages. Vascular endothelial growth factor (VEGF) has been reported as the most potent inducer of retinal neovascularization. We previously demonstrated that integrin-linked kinase (ILK) regulates retinal vascular endothelial proliferation, migration and tube formation. However, little is known about the existence of cross-talk between ILK and VEGF signaling in retinal vascular endothelial cells and the probable regulatory role of ILK during VEGF-induced retinal endothelial cell migration. The purpose of this work was to investigate the role of ILK in VEGF-induced retinal neovascularization. METHODS: Cultured retinal endothelial cells (RF/6A) were knocked down for ILK using a small interfering RNA (siRNA). For this, cellular ILK expression was quantified by real-time quantitative PCR, Western blot analysis and immunocytochemical assay, and cytotoxicity of transfection was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. ILK siRNA-transfected RF/6A cells were induced by VEGF, and cell proliferation was determined by the MTT assay, cell migration was measured by cell counting in modified Boyden chambers and cell spreading and tube formation assays were performed. Furthermore, the impact of ILK-specific siRNA on VEGF-induced VEGF receptor 2 (VEGFR-2) phosphorylation and activation of downstream signal pathways were tested by Western blot analysis. RESULTS: Both ILK mRNA and protein levels were virtually undetectable after transfection with ILK siRNA, and blocking the expression of ILK by siRNA significantly inhibited VEGF-induced retinal endothelial cell proliferation, attachment, spreading, migration and tube formation. Knockdown of ILK effectively suppressed VEGF-induced p38 mitogen-activated protein kinase (MAPK) and Akt phosphorylation, but had no effects on VEGFR-2, extracellular signal-regulated protein kinase and Jun N terminus kinase phosphorylation. CONCLUSION: We conclude that knockdown of ILK with siRNA effectively inhibited VEGF-induced retinal endothelial cell attachment, spreading, migration and tube formation. p38 MAPK and Akt are downstream signaling pathways of the ILK that regulated VEGF-induced retinal neovascularization. Targeting ILK may be a potentially useful therapeutic approach for treating ocular neovascularization.

Expression of pro- and anti-angiogenic isoforms of VEGF in the mouse model of oxygen-induced retinopathy.

Retinopathy of prematurity (ROP) has become one of the leading causes of blindness and visual loss in children over the last half century. Vascular endothelial growth factor (VEGF-A) is the principal stimulator of angiogenesis. Recently, it has been identified that VEGF was differentially spliced from exons 8 to exons 8a and 8b to form two families: the pro-angiogenic VEGFxxx family and the anti-angiogenic VEGFxxxb family. This alternate splicing produced VEGFxxxb proteins of the same length as VEGFxxx family, but with different C terminal amino acid sequences. VEGFxxxb appeared to be able to inhibit VEGFxxx-dependent angiogenesis. In our study, we investigated the protein expression course of VEGFxxx and VEGFxxxb by Western-blot in a mouse model of Oxygen-induced Retinopathy (OIR) from postnatal day 1 (P1) to postnatal day 21 (P21). We also analyzed the relative protein expression level of VEGF(165)b isoform in the OIR mouse model. We found that both VEGFxxx and VEGFxxxb were present in the mouse retina, among which, VEGF(164) and VEGF(165)b appeared to be predominant VEGFxxx and VEGFxxxb isoforms respectively in the mouse retina. We also found that the two family had different expression pattern correlated with neovascularization development and that the relative expression level of VEGF(165)b isoform switched during the neovascularization development in the OIR mouse model. In OIR group, the protein level of total VEGF isoforms (a mix of VEGF(164) and VEGF(165)b, detected by pan-VEGF antibody) continuously increased and peaked at P17 while VEGF(165)b continuously decreased from P9 which was well related with the vessel obliteration and neovascularization development in the mouse model of OIR. The neovascularization development correlates with an increase of total VEGF isoforms and the decrease of VEGF(165)b, indicating that there is a pro-angiogenic VEGF shift. Therefore, anti-angiogenic therapy that could alter the ratio of VEGFxxxb/VEGFxxx may be more effective.

The role of SLIT-ROBO signaling in proliferative diabetic retinopathy and retinal pigment epithelial cells.

PURPOSE: SLIT-ROBO signaling acts as a cue in neuronal guidance and plays a role in vasculogenesis and angiogenesis. The aim of this study is to explore the effects of robo1 and slit2 on the formation of fibrovascular membranes (FVMs) in samples from patients with proliferative diabetic retinopathy. The effects of advanced glycation end products (AGEs) on robo1 and slit2 expression in human retinal pigment epithelium (RPE) cells and the role of recombinant N-SLIT2 protein in human RPE cell regulation were investigated. METHODS: Immunohistochemistry was performed to determine the presence and distribution of robo1 and slit2 in FVMs, and to confirm the effects of SLIT-ROBO signaling on FVM formation. The expression levels of robo1 and slit2 in RPE cells under basal and differential concentrations of AGEs were measured using real-time reverse transcription-polymerase chain reaction (RT-PCR), immunoblotting, or enzyme-linked immunosorbent assay. LY294002, an inhibitor of phosphoinositide 3-kinase (PI3K), was used to help determine the AGE signaling mechanism. Recombinant N-SLIT2 protein was used to study the effects of slit2 on RPE cells in vitro. Cell proliferation, migration, and cell cycling were assessed using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay assay (MTT) assay, a Boyden chamber assay, and flow cytometry. Real-time RT-PCR and enzyme-linked immunosorbent assay were used to study vascular endothelial growth factor (VEGF) mRNA expression in and VEGF protein secretion from RPE cells. RESULTS: Robo1 and Slit2 were expressed in FVMs in RPE cells coimmunostained for pancytokeratin. AGEs resulted in an increase in robo1 and slit2 levels in RPE cells, and inhibition of PI3K-blocked robo1 and slit2 expression. Recombinant N-SLIT2 protein increased proliferation, attachment, and migration of the RPE cells, and these cells demonstrated significant accumulation in the S phase compared to control cells. Furthermore, RPE cells treated with exogenous N-SLIT2 protein had higher levels of VEGF mRNA expression and VEGF protein secretion (p<0.05). CONCLUSIONS: Robo1 and slit2 may play a role in the formation of FVMs. The presence of AGEs increased levels of robo1 and slit2 in human RPE cells via signaling through the PI3K/Akt pathway. Recombinant N-SLIT2 protein increased the biologic activity of RPE cells, as well as the expression of VEGF. From these results, we may conclude that SLIT-ROBO signaling potentially contributes to the development of diabetic retinopathy.