Role of miR-132 in angiogenesis after ocular infection with herpes simplex virus

MicroRNAs (miRNAs) are small regulatory molecules that control diverse biological processes that include angiogenesis. Herpes simplex virus (HSV) causes a chronic immuno-inflammatory response in the eye that may result in corneal neovascularization during blinding immunopathological lesion stromal keratitis (SK). miR-132 is a highly conserved miRNA that is induced in endothelial cells in response to growth factors, such as vascular endothelial growth factor (VEGF). In this study, we show that miR-132 expression was up-regulated (10- to 20-fold) after ocular infection with HSV, an event that involved the production of both VEGF-A and IL-17. Consequently, blockade of VEGF-A activity using soluble VEGF receptor 1 resulted in significantly lower levels of corneal miR-132 after HSV infection. In addition, low levels of corneal miR-132 were detected in IL-17 receptor knockout mice after HSV infection. In vivo silencing of miR-132 by the provision of anti-miR-132 (antagomir-132) nanoparticles to HSV-infected mice led to reduced corneal neovascularization and diminished SK lesions. The anti-angiogenic effect of antagomir-132 was reflected by a reduction in angiogenic Ras activity in corneal CD31-enriched cells (presumably blood vessel endothelial cells) during SK. To our knowledge, this is one of the first reports of miRNA involvement in an infectious ocular disease. Manipulating miRNA expression holds promise as a therapeutic approach to control an ocular lesion that is an important cause of human blindness.

Human tears reveal insights into corneal neovascularization

Corneal neovascularization results from the encroachment of blood vessels from the surrounding conjunctiva onto the normally avascular cornea. The aim of this study is to identify factors in human tears that are involved in development and/or maintenance of corneal neovascularization in humans. This could allow development of diagnostic tools for monitoring corneal neovascularization and combination monoclonal antibody therapies for its treatment. In an observational case-control study we enrolled a total of 12 patients with corneal neovascularization and 10 healthy volunteers. Basal tears along with reflex tears from the inferior fornix, superior fornix and using a corneal bath were collected along with blood serum samples. From all patients, ocular surface photographs were taken. Concentrations of the pro-angiogenic cytokines interleukin (IL)-6, IL-8, Vascular Endothelial Growth Factor (VEGF), Monocyte Chemoattractant Protein 1 (MCP-1) and Fas Ligand (FasL) were determined in blood and tear samples using a flow cytometric multiplex assay. Our results show that the concentration of pro-angiogenic cytokines in human tears are significantly higher compared to their concentrations in serum, with highest levels found in basal tears. Interestingly, we could detect a significantly higher concentration of IL- 6, IL-8 and VEGF in localized corneal tears of patients with neovascularized corneas when compared to the control group. This is the first study of its kind demonstrating a significant difference of defined factors in tears from patients with neovascularized corneas as compared to healthy controls. These results provide the basis for future research using animal models to further substantiate the role of these cytokines in the establishment and maintenance of corneal neovascularization.

Altered angiogenesis in caveolin-1 gene-deficient mice is restored by ablation of endothelial nitric oxide synthase

Caveolin-1 is an essential structural protein of caveolae, specialized plasma membrane organelles highly abundant in endothelial cells, where they regulate multiple functions including angiogenesis. Caveolin-1 exerts a tonic inhibition of endothelial nitric oxide synthase (eNOS) activity. Accordingly, caveolin-1 gene-disrupted mice have enhanced eNOS activity as well as increased systemic nitric oxide (NO) levels. We hypothesized that excess eNOS activity, secondary to caveolin deficiency, would mediate the decreased angiogenesis observed in caveolin-1 gene-disrupted mice. We tested tumor angiogenesis in mice lacking either one or both proteins, using in vitro, ex vivo, and in vivo assays. We show that endothelial cell migration, tube formation, cell sprouting from aortic rings, tumor growth, and angiogenesis are all significantly impaired in both caveolin-1-null and eNOS-null mice. We further show that these parameters were either partially or fully restored in double knockout mice that lack both caveolin-1 and eNOS. Furthermore, the effects of genetic ablation of eNOS are mimicked by the administration of the NOS inhibitor N-nitro-L-arginine methyl ester hydrochloride (L-NAME), including the reversal of the caveolin-1-null mouse angiogenic phenotype. This study is the first to demonstrate the detrimental effects of unregulated eNOS activity on angiogenesis, and shows that impaired tumor angiogenesis in caveolin-1-null mice is, at least in part, the result of enhanced eNOS activity.

Cellular level characterization of capillary regression in inflammatory angiogenesis using an in vivo corneal model

In this study, we introduce a technique for repeated, microscopic observation of single regressing capillaries in vivo in inflamed murine corneas. Natural capillary regression was initiated by removal of inflammatory stimulus during an active pro-angiogenic phase, while the additional impact of anti-angiogenic treatment with triamcinolone or bevazicumab was investigated. Capillaries regressed naturally within 1 week and treatments did not further enhance the natural regression. Morphologically, early-phase regression was characterized by significant lumen narrowing and a significant reduction in CD11b+ myeloid cell infiltration of the extracellular matrix. By 1 week, vascular remodeling occurred concomitant with CD11b+CD68+KiM2R+ mature macrophage localization on capillary walls. Empty conduits without blood flow, positive for collagen IV and devoid of vascular endothelium and pericytes, were apparent in vivo and by 3 weeks were more numerous than perfused capillaries. By 3 weeks, macrophages aggregated around remaining perfused capillaries and were observed in apposition with degrading capillary segments. Abrupt termination of capillary sprouting in our regression model further revealed vascular endothelial abandonment of sprout tips and perfused capillary loop formation within a single angiogenic sprout, possibly as an intussusceptive response to cessation of the stimulus. Finally, we observed lumen constriction and macrophage localization on capillary walls in vivo in a clinical case of corneal capillary regression that paralleled findings in our murine model.

Potential anti-angiogenic role of Slit2 in corneal neovascularization

Slits are large secreted proteins critical for axon guidance and neuronal precursor cell migration in nervous system. Evidence suggests that classical neuronal guidance cues also regulate vascular development. Our objective was to investigate whether neuronal guidance cue Slit2 and Roundabout (Robo) receptors are involved in corneal neovascularization (NV). Corneal NV model in rats was induced by implantation of agarose-coated gelfoam pellets containing basic fibroblast growth factor (bFGF) into corneal stroma. Differential expression of Slit2 and Robo1-4 between normal and neovascularized cornea was detected by real-time RT-PCR and visualized by immunohistochemistry and in situ hybridization. Primary human umbilical vein endothelial cells (HUVECs) were harvested and their expression of Robo1-4 was detected by RT-PCR. Recombinant human Slit2 protein was prepared and the effect of it on the migration of vascular endothelial cells was examined using cell migration assay. Agarose-coated gelfoam pellets were able to induce well-localized and reproducible corneal NV model. A significant down-regulation of Slit2 and a strong up-regulation of Robo1 and Robo4 were seen in neovascularized cornea when compared with normal cornea (P < 0.05). Slit2, Robo1 and Robo4 were throughout the epithelium in normal cornea and markedly weak or absent in epithelium in neovascularized cornea, with Robo1 and Robo4 being prominent in vascular endothelial cells invading the stroma. Primary HUVECs were confirmed to express both Robo1 and Robo4 receptors and their migration was inhibited by Slit2 (P < 0.05). This is the first study to assess the association between Slit2 and corneal NV. Our findings suggest that the interaction of Slit2 with Robo1 and Robo4 receptors plays an essential role in inhibiting pathological neovascular processes of the cornea and may represent a new therapeutic target for corneal NV.

Delayed neovascularization in inflammation-induced corneal neovascularization in interleukin-10-deficient mice

PURPOSE

To investigate the potential modulatory role of interleukin-10 (IL-10) in the suture model for corneal neovascularization.

METHODS

Neovascularized areas were measured on corneal flat-mounts in IL-10(-/-) and wild-type C57BL6 mice. The inflammatory cellular response was characterized with immunohistochemistry. Gene expression was measured by real-time polymerase chain reaction.

RESULTS

IL-10(-/-) mice showed a delayed neovascular response compared to wild-type animals at day 6 after suture, when approximately half of the cornea was neovascularized. No apparent differences in inflammatory responses or in messenger RNA (mRNA) expression for proangiogenic factors were detected in IL-10(-/-) versus wild-type mice.

CONCLUSION

IL-10 appears to have a proangiogenic effect in the suture model for corneal neovascularization that cannot be explained by either IL-10's anti-inflammatory effect or apparent cross-talk with the angiogenic factors vascular endothelial growth factor (VEGF)-A, metalloproteinase (MMP)-2 and MMP-9, angiopoietin (Ang)-1 and Ang-2.

[Small interference RNA targeting vascular endothelial growth factor inhibits rat corneal neovascularization]

OBJECTIVE

To test the effects of VEGF-siRNA-transfected corneal epithelium on corneal neovascularization (CNV).

METHODS

It was an experimental study. Cultured rat corneal epithelial cells and keratocytes were transfected with synthesize VEGF siRNA by lipofectamine 2000. The level of VEGF mRNA was analyzed by real time PCR, and the protein levels were determined by enzyme-linked immunosorbent assay (ELISA). CNV was induced by cauterization with 1 mol/L sodium hydroxide in rat corneas. The VEGF-siRNA-transfected-corneal epithelium cells were transplanted to the CNV lesions. Immediately after transplantation, the VEGF-siRNA combined with lipofectamine 2000 were directly transfected rat cornea through injecting into the anterior chamber. After surgery, the surface areas occupied by new vessels were measured, and VEGF protein was localized by immunohistochemistry.

RESULTS

The levels of VEGF expression at both mRNA and protein in the VEGF-siRNA transfected corneal epithelial cells and keratocytes were significantly lower than those of control cells. VEGF siRNA could inhibit the expression of VEGF mRNA in corneal epithelial cells and keratocytes to 57% - 85% and 59% - 78%, respectively. The VEGF-siRNA-transfected-corneal epithelium transplantation significantly decreased the surface areas occupied by new vessels. VEGF expression level in interference groups was lower than that in the control group.

CONCLUSIONS

The development of CNV is markedly suppressed by VEGF-siRNA transfection in vivo.

Tolerability and safety of GS-101 eye drops, an antisense oligonucleotide to insulin receptor substrate-1: a 'first in man' phase I investigation

AIMS

GS-101 (GeneSignal, Epalinges, Switzerland) is an antisense oligonucleotide that inhibits the expression of the scaffold protein insulin receptor substrate-1 (IRS-1). Inhibition of IRS-1 results in the prevention of neovascular growth and was shown to prevent the angiogenic process in preclinical in vitro and in vivo experiments. There is therefore a strong therapeutic rational for targeting angiogenesis in pathological neovascularization. We aimed to investigate the safety, tolerability and bioavailability of GS-101 eye drops.

METHODS

This was a Phase I open-label study. The investigation was performed in two steps. Local ocular tolerability was first assessed with the application of one single low dose in one eye. After no signs of intolerance were observed in the subjects, the dose escalation phase of the study was initiated, and the remaining subjects received three times daily escalating doses of GS-101 in one eye for 14 days.

RESULTS

The 14 healthy volunteers tolerated well 14 days' continued use of escalating doses of GS-101 from 43 to 430 microg per day. Other than itching, experienced also in the control eye by one subject and determined to be unrelated to the study treatment, no signs of intolerance were observed.

CONCLUSIONS

The tolerability profile obtained from this study suggests that GS-101 is safe for human use. Further clinical evaluations in diseases related to abnormal angiogenesis are being targeted. In particular, the neovascularization-related orphan indications of corneal graft rejection, retinopathy of pre-maturity and neovascular glaucoma are currently under Phase II clinical investigation and are showing promising results.

Inhibition of corneal neovascularization with plasmid pigment epithelium-derived factor (p-PEDF) delivered by synthetic amphiphile INTeraction-18 (SAINT-18) vector in an experimental model of rat corneal angiogenesis

The use of Synthetic Amphiphile INTeraction-18 (SAINT-18) carrying plasmid pigment epithelium-derived factor (p-PEDF) as an anti-angiogenesis strategy to treat corneal neovascularization in a rat model was evaluated. Four partially dried forms (Group A: 0 microg, B: 0.1 microg, C: 1 microg, D: 10 microg) of a p-PEDF-SAINT-18 were prepared and implanted into the rat subconjunctival substantia propria 1.5 mm from the limbus at the temporal side. The 1 microg of plasmid-basic fibroblast growth factor--SAINT-18 (p-bFGF-SAINT-18) (1 microg) was prepared and implanted into the rat corneal stroma 1.5 mm from the limbus on the same side. Inhibition of neovascularization was observed and quantified from day 1 to day 60. PEDF (50-kDa) and bFGF (18-kDa) protein expression were analyzed by biomicroscopic examination, Western blot analysis, and immunohistochemistry. Gene expression in corneal and conjunctival tissue was observed as early as 3 days after gene transfer and stably lasted for over 3 months with minimal immune reaction. Subconjunctival injection of a highly efficient p-PEDF-SAINT-18 successfully inhibited corneal neovascularization. Successful gene expression of bFGF, PEDF and a mild immune response of HLA-DR were shown by immunohistochemistry staining. We concluded that SAINT-18 was capable of directly delivering genes to the ocular surface by way of subconjunctival injection, and delivered sustained, high levels of gene expression in vivo to inhibit angiogenesis.

[Relationship between corneal neovascularization and various relevant biological factors in surrounding cornea stroma of rats]

OBJECTIVE

To study the relationship between corneal neovascularization and various biological factors in corneal stroma of rats.

METHODS

It was an experimental study. Corneal neovascularization was induced by alkali burn in 40 rats. Transforming growth factor-beta1 (TGF-beta1), alpha-smooth muscle actin (alpha-SMA) and fibroblast activation protein (FAP) in the stroma surrounding corneal neovascularization were detected by immunohistochemical studies on day 1, 3 and 7 after chemical burn. Platelet-endothelial cell adhesion molecule-1 (CD31) was used to identify the vascular endothelial cells. RT-PCR was used to identify FAP in the cornea 3 and 7 days after chemical burn. Picrosirius staining and polarization microscopy were used to detect changes of collagen types I and III in the cornea.

RESULTS

After alkali burn, TGF-beta1 was first expressed in the cornea stroma. Then, some stroma cells expressed both alpha-SMA and FAP. The FAP(+) keratocytes were found surrounding the CD31(+) endothelium of angiogenesis. RT-PCR study showed that FAP mRNA was only present in neovascularized cornea and not in normal cornea. Polarization microscopy revealed that the collagen types I and III were rearranged in neovascularized cornea.

CONCLUSIONS

Various biological factors in corneal stroma are changed when the cornea shows neovascularization. FAP(+) keratocytes are present in the stroma, and the appearance of these cells parallels the growth of vascular endothelial cells. Collagen types I and III are rearranged during the process of angiogenesis.

[The effect of rapamycin liposome gutta inhibiting rat corneal neovascularization]

OBJECTIVE

To explore the inhibiting effect of rapamycin (RAPA) on corneal neovascularization (CNV) of rats and the functional mechanism.

METHODS

A design group was adopted. 102 Wistar rats were divided into four groups at random, including rapamycin liposome treated group (24 rats), the rapamycin solved in bean oil treated group (24 rats), blank liposome treated group (24 rats), blank treated group (24 rats) and normal control group (6 rats). All right eyes of 96 rats were induced by alkali cauterization. Rapamycin liposome were prepared by thin film hydration and the major factors were studied by the method of orthogonal design. After alkali burn, cauterized rats were observed by slitlamp biomicroscope every day. On the 1st, 4th, 7th, 14th days after operation, the expression of HIF-1alpha and VEGF were examined by immunohistochemical method and semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). The analysis of variance and q test groups for analysis were adopted to analyze the results.

RESULTS

(1) The bodies of RAPA liposome were intact kinds of spheres, the average diameter was 145.2 nm, and the envelopment rate was 90.02%. (2) After the burn of 14 d, CNV area of B, C, D and E group were (28.289 +/- 0.703), (28.005 +/- 0.801), (20.002 +/- 1.005) and (22.300 +/- 0.853) mm(2) (F = 159.62, P < 0.05). The CNV of both the rapamycin liposome treated group and the rapamycin solved in bean oil group grew slowly and smaller than that of blank liposome treated group and blank treated group (q = 47.80, 46.20, 34.60, 32.90;P = 0.00). While the rapamycin liposome treated group changed more obviously than the rapamycin solved in bean oil group (q = 13.20, P = 0.00). After alkali burn, the expression of HIF-1alpha and VEGF increased dramatically, meanwhile the expression of HIF-1alpha and VEGF were significantly decreased by RAPA.

CONCLUSIONS

Liposome body is an excellent medicine carrier for the RAPA. RAPA can obviously suppress the growth of CNV. The possibly mechanism is weakening VEGF expression by inhibiting the transcription factor HIF-1alpha.

Analysis of angiogenesis induced by cultured corneal and oral mucosal epithelial cell sheets in vitro

The aim of this study was to compare angiogenesis-induction capabilities of cultured corneal epithelial cells (CCE) and cultured oral mucosal epithelial cells (COE) in vitro, and identify candidate factors that induce corneal neovascularization after transplantation of COE sheets. Rabbit corneal and oral mucosal epithelial cells were co-cultured with mitomycin C-treated NIH/3T3 cells on culture plates and inserts. After CCE and COE were multilayered, culture medium was replaced by basal medium and incubated. Angiogenic potential was examined by invasion, migration and tube formation assays with human umbilical vein endothelial cells (HUVECs). Protein secretion of fibroblast growth factor 2 (FGF2), vascular endothelial growth factor (VEGF), angiopoietin-1 and transforming growth factor beta1 was assessed in conditioned medium by ELISA. Gene expression of FGF2 and VEGF was also quantified by real-time RT-PCR and neutralizing antibodies against FGF2 and VEGF were employed for blocking assays. COE induced significantly greater invasion, migration and tube formation of HUVECs, when compared to CCE. CCE secreted a significantly lower amount of FGF2 than COE, while amounts of VEGF were approximately equal in both culture media. Similarly, significantly higher expression of FGF2 mRNA was observed with COE, while no significant difference in VEGF mRNA expression was observed between COE and CCE. Only anti-FGF2 neutralizing antibody significantly suppressed HUVEC invasion and migration induced by COE, without suppression in CCE. In conclusion, angiogenic potential of COE is greater than that of CCE and FGF2 is a candidate involved in the induction of corneal neovascularization after COE sheet transplantation.

Lymphangiogenesis concurrent with haemangiogenesis in the human cornea

BACKGROUND

Corneal transplant rejection can occur with and without neovascularization; therefore, it is necessary to elucidate what other factors allow for rejection. It has been suggested that the lymphatic system may play a role in graft failure, but it has also been held that the cornea is devoid of lymphatics. Use of a new monoclonal antibody against a lymphatic endothelial marker, D2-40, has been used to detect lymphatics in other tissues. The purpose of this study was to use this new tool to determine if the human cornea can undergo lymphangiogenesis.

METHODS

Twelve corneal buttons submitted for routine pathology were subjected to immunohistochemical staining with a monoclonal antibody against D2-40 to detect the presence/absence of lymphatics by light microscopy.

RESULTS

By the criteria defined, lymphatic vessels were identified in seven out of 12 corneal buttons. In these cases, there was also evidence of neovascularization. Lymphatic positive buttons included four cases where there were histological markers of inflammation. There were no identifiable lymphatics in the remaining five cases and no sign of vascularization.

CONCLUSIONS

Corneal lymphatics were identified in association with corneal neovascularization, via the use of a monoclonal antibody against D2-40. In non-vascularized corneas, lymphatics were absent.

Blockade of VEGFR3-signalling specifically inhibits lymphangiogenesis in inflammatory corneal neovascularisation

PURPOSE

Inflammatory corneal hem- and lymphangiogenesis occurring both prior to as well as after penetrating keratoplasty significantly increase the risk for subsequent immune rejections. The purpose of this study was to analyze whether the blocking anti-VEGFR3 antibody mF4-31C1 is able to inhibit the outgrowth of pathologic new lymphatic vessels in a mouse model of suture-induced, inflammatory corneal neovascularisation, and whether this antibody specifically inhibits lymphangiogenesis without affecting hemangiogenesis.

METHODS

Three interrupted 11-0 nylon sutures were placed into the corneal stroma of BALB/c mice (6 weeks old) and left in place for 7 days to induce neovascularisation. The treatment group (n = 9) received the anti-VEGFR3 antibody mF4-31C1 intraperitoneally on the day of surgery and 3 days later (0.5 mg/mouse). Control mice received an equal amount of control IgG solution. For immunohistochemistry, corneal flat mounts were stained with LYVE-1 as a specific lymphatic vascular endothelial marker and with CD31 as panendothelial marker. Morphometry was performed with the image analysis software analySIS;B (Soft Imaging Systems GmbH, Münster, Germany). To improve the objectivity and precision of the morphometrical analysis, we established a modified method using grey filter sampling on monochromatic pictures.

RESULTS

The mF4-31C1 antibody-treated mice displayed nearly complete inhibition of lymphangiogenesis compared with IgG controls (p < 0.006). In contrast, there was no significant inhibitory effect observed with respect to blood vessel growth (p > 0.05).

CONCLUSIONS

Inflammatory corneal lymphangiogenesis seems to depend on VEGFR3-signalling. By blocking this receptor the ingrowths of lymphatic vessels can be inhibited almost completely, and specifically without affecting hemangiogenesis. This may open new treatment options to promote (corneal) graft survival without affecting hemangiogenesis.

Comparison of EphA receptor tyrosine kinases and ephrinA ligand expression to EphB-ephrinB in vascularized corneas

PURPOSE

Eph cell surface receptors and their ligands, ephrins, are involved in neuronal patterning and neovascularization. Our purpose is to compare and characterize the expression of ephrinA ligands and EphA receptors to ephrinB ligands and EphB receptors in excised mouse corneal tissue, in corneal epithelial and keratocyte cell lines, and during corneal angiogenesis.

METHODS

Mouse corneal epithelial cells and keratocytes were immortalized using SV40T antigen viral infection of primary cultures. The immortalized epithelial cells and keratocytes were cloned and characterized using antibodies to keratin, vimentin, integrin alpha5beta1, and alpha-smooth muscle actin. Basic fibroblast growth factor pellets were implanted to induce corneal neovascularization. The eyes of wild-type, ephrinB2(tlacZ/+), and EphB4(tlacZ/+) heterozygous mice were harvested and sectioned 7 days after pellet implantation. Confocal immunohistochemistry was performed to compare the expression of the Eph/ephrinA family (EphA1-8, ephrinA1-5) and Eph/ephrinB family (EphB1-4, EphB6 ephrinB1-3).

RESULTS

EphA1, EphA3, ephrinA1, ephrinA2, EphB1, EphB4, ephrinB1, and ephrinB2 were detected in wild-type mouse corneal epithelial cells and keratocytes. EphA2 was immunolocalized only in epithelial cells. Also, EphA3, ephrinA1, EphB1, EphB4, and ephrinB1 were immunolocalized to the corneal epithelium and stroma. In the vascularized corneas, ephrinB1 was immunolocalized mainly to the keratocytes around the vessels, and ephrinB2, EphB1, and EphB4 were colocalized mainly with CD31 to the vascular endothelial cells.

CONCLUSIONS

The characterization of ephrin ligand and Eph receptor expression during cornea angiogensis in this study suggests that the Eph/ephrin family of receptor tyrosine kinases and their ligands may play a role in the regulation of corneal angiogenesis.

Estrogen-mediated endothelial progenitor cell biology and kinetics for physiological postnatal vasculogenesis

Estrogen has been demonstrated to promote therapeutic reendothelialization after vascular injury by bone marrow (BM)-derived endothelial progenitor cell (EPC) mobilization and phenotypic modulation. We investigated the primary hypothesis that estrogen regulates physiological postnatal vasculogenesis by modulating bioactivity of BM-derived EPCs through the estrogen receptor (ER), in cyclic hormonally regulated endometrial neovascularization. Cultured human EPCs from peripheral blood mononuclear cells (PB-MNCs) disclosed consistent gene expression of ER alpha as well as downregulated gene expressions of ER beta. Under the physiological concentrations of estrogen (17beta-estradiol, E2), proliferation and migration were stimulated, whereas apoptosis was inhibited on day 7 cultured EPCs. These estrogen-induced activities were blocked by the receptor antagonist, ICI182,780 (ICI). In BM transplanted (BMT) mice with ovariectomy (OVX) from transgenic mice overexpressing beta-galactosidase (lacZ) regulated by an endothelial specific Tie-2 promoter (Tie-2/lacZ/BM), the uterus demonstrated a significant increase in BM-derived EPCs (lacZ expressing cells) incorporated into neovasculatures detected by CD31 immunohistochemistry after E2 administration. The BM-derived EPCs that were incorporated into the uterus dominantly expressed ER alpha, rather than ER beta in BMT mice from BM of transgenic mice overexpressing EGFP regulated by Tie-2 promoter with OVX (Tie-2/EGFP/BMT/OVX) by ERs fluorescence immunohistochemistry. An in vitro assay for colony forming activity as well as flow cytometry for CD133, CD34, KDR, and VE-cadherin, using human PB-MNCs at 5 stages of the female menstrual-cycle (early-proliferative, pre-ovulatory, post-ovulatory, mid-luteal, late-luteal), revealed cycle-specific regulation of EPC kinetics. These findings demonstrate that physiological postnatal vasculogenesis involves cyclic, E2-regulated bioactivity of BM-derived EPCs, predominantly through the ER alpha.

Endogenous TNFα Suppression of Neovascularization in Corneal Stroma in Mice

PURPOSE

To examine the role of tumor necrosis factor alpha (TNFalpha) in stromal neovascularization in injured cornea in vivo and in cytokine-enhanced vessel-like endothelial cell tube formation in vitro.

METHODS

An in vitro model of angiogenesis was used to examine the roles of TNFalpha on tube formation by human umbilical vein endothelial cells (HUVECs) cocultured with fibroblasts on induction by transforming growth factor beta1 (TGFbeta1) and vascular endothelial growth factor (VEGF). Central cauterization was used to induce stromal neovascularization in corneas of wild-type (WT) and TNFalpha-null (Tnfalpha(-/-)) mice. At 7, 14, or 21 days of injury, experimental mice were killed, and the eyes were enucleated and subjected to histologic and immunohistochemical examination and real-time reverse transcription-polymerase chain reaction.

RESULTS

HUVECs formed a vessel-like tube structure on the fibroblast feeder layer. Adding TGFbeta1, VEGF, or both augmented vessel-like tube formation by HUVECs cocultured with fibroblasts. Adding TNFalpha (5 ng/mL) completely abolished the formation of tube-like structures despite the presence or absence of TGFbeta1 or VEGF in coculture. In vivo, cauterization of the central cornea induced the formation of CD31(+) new vessels surrounding the limbus in WT mice. More prominent central stromal neovascularization accompanied by increased expression of TGFbeta1 and VEGF was found in Tnfalpha(-/-) mice compared with WT mice.

CONCLUSIONS

In addition to inhibiting TGFbeta1 and VEGF expression by fibroblasts, endogenous TNFalpha may counter the induction effects of TGFbeta1 and VEGF on vascular endothelial cells and may block neovascularization.

Nanoparticles sustain expression of Flt intraceptors in the cornea and inhibit injury-induced corneal angiogenesis

PURPOSE

To determine whether long-term expression of intraceptors can be achieved using plasmid albumin nanoparticles and whether nanoparticles can inhibit and cause regression of murine corneal neovascularization induced by mechanical-chemical trauma.

METHODS

Albumin nanoparticles encapsulating pCMV.Flt23K were developed as a lyophilized product that is easily redispersed in an aqueous medium. Nanoparticles were injected into the corneas of uninjured BALB/c mice and observed for toxicity for 3 weeks. Entry of nanoparticles into corneal cells was demonstrated through transmission electron microscopy and confocal imaging. Naked pCMV.Flt23K, nanoparticles encapsulating pCMV.Flt23K, or empty pCMV nanoparticles were injected into uninjured mouse corneas. These corneas were subjected to mechanical alkali trauma 3 weeks after injection.

RESULTS

Nanoparticles were nontoxic to the cornea and entered into corneal keratocyte cytoplasm. They persisted for at least 4 weeks in the cornea, expressed effective intraceptor levels for at least 5 weeks, and reduced corneal neovascularization by approximately 40% (P = 0.035) at 5 weeks after administration.

CONCLUSIONS

Albumin nanoparticles are not toxic to the cornea and can express intraceptors for extended periods that are effective in suppressing injury-induced corneal neovascularization.

Inhibition of angiogenesis induced by cerebral arteriovenous malformations using Gamma Knife irradiation

Object

The authors studied the effect of Gamma Knife irradiation on angiogenesis induced by cerebral arteriovenous malformation (AVM) tissues implanted in the corneas of rats.

Methods

Ten AVM specimens obtained from tissue resections performed at Marmara University between 1998 and 2004 were used. A uniform amount of tissue was implanted into the micropocket between the two epithelial layers of the cornea. Gamma Knife irradiation was applied with dose prescriptions of 15 or 30 Gy to one cornea at 100% iso-dose. Dosing was adjusted so that the implanted cornea of one eye received 1.5 Gy when 15 Gy was applied to the other cornea. Similarly, one cornea received 3 Gy when 30 Gy was applied to the other cornea. Angiogenic activity was graded daily by biomicroscopic observations. Forty-eight other rats were used for microvessel counting and vascularendothelial growth factor (VEGF) staining portions of the experiment. Micropieces of the specimens were again used for corneal implantation. Rats from each group were killed on Days 5, 10, 15, and 20, and four corneas from each group were examined.

Gamma Knife irradiation dose dependently decreased AVM-induced neovascularization in the rat cornea as determined by biomicroscopic grading of angiogenesis, microvessel count, and VEGF expression.

Conclusions

The results suggest that Gamma Knife irradiation inhibits angiogenesis induced by AVM tissue in the cornea angiogenesis model. The data are not directly related to understanding how Gamma Knife irradiation occludes existing AVM vasculature, but to understanding why properly treated AVMs do not recur and do not show neovascularization after Gamma Knife irradiation.

Changes of extracellular matrix of rat cornea after exposure to hypoxia

The purpose of the study was to check whether hypoxia of corneal tissue increases the collagenolytic activity due to release of reactive oxygen and nitrogen species. Rats were exposed to hypoxia 10% O(2) for 4, 14, and 21 days. The radical tissue injury was measured by the level of nitrotyrosine and changes in the lipoperoxide-related fluorophores. Collagen protein composition was analyzed by slab gel electrophoresis. The activity of gelatinolytic enzymes was studied using the zymography. The vascularization of the corneas was measured. We found no differences in the corneal tissue in the gel electrophoretic profile of collagenous proteins and gelatinolytic activity between normoxic and hypoxic rats. We did not find any sign of radical tissue injury. There were no changes in the vascularization of corneas after exposition to hypoxia. The environmental 10% hypoxia does not induce radical tissue injury and an increase of collagenolytic activity in the rat cornea.

The expression of nuclear factor kappa B in inflammation-induced rat corneal neovascularization

PURPOSE

To investigate the involvement of the nuclear-transfactor-kappa B (NF-kappa B) in the rat model of inflammation-induced corneal neovascularization (CNV).

METHODS

The CNV model in Sprague-Dawley rats was induced by alkaline cauterization of the central cornea. The corneas were examined by a slit lamp microscope. NF-kappa B was assayed by Western blot. Vascular endothelial growth factor (VEGF) protein was evaluated by immunohistochemistry. VEGF mRNA levels were determined by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Morphologically, the CNV was shown on the second day after cautery. In corneas after cautery, NF-kappa B protein increased 6 hours after cautery, peaked 4 days after cautery, and decreased to near baseline by day 14. VEGF protein and mRNA increased gradually in the early stage after cautery, reached the highest level on the fourth day, and then decreased to near baseline slowly after 7 days.

CONCLUSIONS

The activated NF-kappa B was up-regulated in the early stage of CNV of rat induced by cauterization, which suggests it may participate in the pathogenesis of wound healing, inflammation, and neovascularization processes in the cornea.

Proangiogenic role of ephrinB1/EphB1 in basic fibroblast growth factor-induced corneal angiogenesis

Corneal neovascularization is a vision-threatening condition caused by various ocular pathological conditions. The aim of this study was to evaluate the function of the ephrin ligands and Eph receptors in vitro and in vivo in corneal angiogenesis in a mouse model. The Eph tyrosine kinase receptors and their ligands, ephrins, are expressed on the cell surface. The functions of Eph and ephrins have been shown to regulate axonal guidance, segmentation, cell migration, and angiogenesis. Understanding the roles of Eph and ephrin in corneal angiogenesis may provide a therapeutic intervention for the treatment of angiogenesis-related disorders. Immunohistochemical studies demonstrated that ephrinB1 and EphB1 were expressed in basic fibroblast growth factor (bFGF)-induced vascularized corneas. EphB1 was specifically colocalized with vascular endothelial marker CD31 surrounded by type IV collagen. EphrinB1 was expressed in corneal-resident keratocytes and neutrophils. Recombinant ephrinB1-Fc, which induces EphB receptor activation, enhanced bFGF-induced tube formation in an in vitro aortic ring assay and promoted bFGF-induced corneal angiogenesis in vivo in a corneal pocket assay. Synergistically enhanced and sustained activation of extracellular signal-regulated kinase was noted in vascular endothelial cell lines after stimulation with ephrin B1 and bFGF combinations. These results suggest that ephrinB1 plays a synergistic role in corneal neovascularization.

Unique Homologous siRNA Blocks Hypoxia-Induced VEGF Upregulation in Human Corneal Cells and Inhibits and Regresses Murine Corneal Neovascularization

PURPOSE

To evaluate the results of amniotic membrane transplantation (AMT) for ocular surface reconstruction in chemical and thermal injuries.

METHODS

Retrospective review of case records of patients who had undergone AMT for chemical injuries (January 1998 to May 2001).

RESULTS

Seventy two eyes of 69 patients were studied of which 24 were acute cases (median-2 days, range, 1-20 days) and 48 were chronic cases (median-12.4 months, range, 1.02-95.8 months). Mean age was 22.4 years (SD +/- 13.34 years) and average follow up duration was 7.8 months (SD +/- 7.1). Main clinical findings were symblephara (52.8%), corneal vascularization (51.3%), conjunctivalization (45.8%), Limbal ischemia (45.8%), Limbal stem cell deficiency (55.5%) and epithelial defect (48.6%). 18 cases were due to acid injuries (5 acute, 13 chronic), 52 were due to alkali (18 acute and 34 chronic) and 2 cases were due to thermal burns (1 each acute and chronic). Overall success rate was 87.5% in acute cases and 72.9% in chronic cases. Indication-wise success rates were 94.3% for epithelial defect healing, 88.2% for symptomatic relief, 59.7% for ocular surface reconstruction, and 55% for improving limbal stem cell function. Success was not achieved in any outcome measure in 1/24 (4.2%) in acute group and 6/48 (12.5%) in chronic group.

CONCLUSION

AMT helps in ocular surface reconstruction, promotes rapid epithelial healing and partially restores limbal stem cell function. It can be considered as an effective modality for the ocular surface restoration in chemical and thermal injuries in selected cases. Success rates in acute and chronic cases are comparable.

Ocular neovascularization: Implication of endogenous angiogenic inhibitors and potential therapy

Ocular neovascularization (NV) is the primary cause of blindness in a wide range of ocular diseases, such as diabetic retinopathy (DR) and age-related macular degeneration (AMD). The exact mechanism underlying the pathogenesis of ocular NV is not yet well understood, and as a consequence, there is no satisfactory therapy for ocular NV. In the last 10 years, a number of studies provided increasing evidence demonstrating that the imbalance between angiogenic stimulating factors and angiogenic inhibitors is a major contributor to the angiogenesis induced by various insults, such as hypoxia or ischemia, inflammation and tumor. The angiogenic inhibitors alone or in combination with other existing therapies are, therefore, believed to be promising in the treatment of ocular NV in the near future. This article reviews recent progress in studies on the mechanisms and treatment of ocular NV, focusing on the implication and therapeutic potential of endogenous angiogenic inhibitors in ocular NV.

Flt-1 intraceptor induces the unfolded protein response, apoptotic factors, and regression of murine injury-induced corneal neovascularization

PURPOSE

To determine whether Flt24K, a recombinant construct of domains 2 to 4 of VEGFR-1 (Flt) coupled with an endoplasmic reticulum retention signal (KDEL) can bind VEGFR-2 and induce apoptosis, unfolded protein response (UPR), and regression of injury-induced corneal neovascularization.

METHODS

Human microvascular endothelial cells were transfected with pCMV.Flt24K and subjected to hypoxia. Cell lysates underwent Western blot analysis with anti-XBP-1 antibody and RT-PCR for CHOP. Human malignant melanoma cells (which express VEGFR-2 but not Flt), were transfected with pCMV.Flt24K, and lysates underwent immunoprecipitation with anti-FLT antibody, and Western blot analysis for VEGF and VEGFR-2. Mouse corneas sustained injury induced by topical NaOH and mechanical scraping and were injected with pCMV.Flt24K 2 weeks later. Corneas were harvested 2 days later for Western blot analysis for XBP-1 and caspase-3 or 1 week later for quantification of neovascularization and TUNEL staining. Saline and empty pCMV vector were used in control experiments.

RESULTS

The mean percentage area of corneal neovascularization in mice 3 weeks after corneal injury and 1 week after intrastromal injection of empty pCMV vector or pCMV.Flt24K was 55.4% +/- 2.7% vs. 19.3% +/- 6.1%, respectively (P < 0.001). Flt24K was found to bind VEGFR-2 and upregulate activated XBP-1 and CHOP in vitro. In vivo, pCMV.Flt24K upregulated activated XBP-1 and caspase-3. Apoptosis was observed in corneal neovascular endothelium in corneas treated with pCMV.Flt24K but not in the control.

CONCLUSIONS

The Flt24K intraceptor can bind VEGFR-2 within cells, induce the unfolded protein response in vitro and in vivo, elicit apoptosis of vascular endothelial cells in vivo, and induce regression of corneal neovascularization in vivo.