Corneal Flat Mounts Research Articles

Subconjunctival aflibercept inhibits corneal angiogenesis and VEGFR-3+CD11b+ cells.

This study aimed to investigate the effects of subconjunctival injection of aflibercept, a soluble protein decoy for VEGFR-1 and VEGFR-2, on corneal angiogenesis and VEGFR-expressing CD11b+ cells in a mouse model of suture-induced corneal neovascularization. Corneal neovascularization was induced in BALB/c mice by placing three sutures on the cornea. Immediately after surgery, either 200µg aflibercept (5 µL) or an equal volume of phosphate-buffered saline (PBS) was administered into the subconjunctival space. Seven days after later, corneal new vessels were quantified through clinical examination and measurement of the CD31-stained area in corneal flat mounts. The levels of pro-angiogenic and inflammatory markers in the cornea were evaluated using RT-qPCR. The percentages of VEGFR-2+CD11b+ cells and VEGFR-3+CD11b+ cells were analyzed in the cornea, blood, and draining cervical lymph nodes (DLNs) using flow cytometry. Subconjunctival injection of aflibercept significantly reduced the growth of corneal new vessels compared to subconjunctival PBS injection. The mRNA levels of Cd31, vascular growth factors (Vegfc and Angpt1), and pro-angiogenic/inflammatory markers (Tek/Tie2, Mrc1, Mrc2, and Il6) in the cornea were downregulated by subconjunctival aflibercept. Also, the percentage of VEGFR-3+CD11b+ cells in the cornea, blood, and DLNs was decreased by aflibercept, whereas that of VEGFR-2+CD11b+ cells was unaffected. Subconjunctival aflibercept administration inhibits inflammatory angiogenesis in the cornea and reduces the numbers of cornea-infiltrating and circulating VEGFR-3+CD11b+ cells.

Modulation of steroid pathway to preserve corneal transparency

Purpose: Corneal neovascularization (CN) is a major cause of blindness worldwide. We previously showed that endothelial mineralocorticoid receptor (MR) contributed to CN in mice. In this study, we investigated the mechanisms of action of MRA in a rat model of limbal deficiency.Methods: CN was induced in Lewis rats by total corneal de‐epithelialization and limbal scratching. Spironolactone (SPL, 25 mg/kg) or eplerenone was administered daily. Control eyes received vehicle. Rats were euthanized at day 3 and 7, and corneas were dissected for transcriptomic analysis. Proteins extracted from corneas at day 7 were used for western blot. Corneal innervation was evaluated by immunostaining of TUBB3 on corneal flat mounts at day 16. Corneal morphology and CN were assessed in vivo by Micron III optical coherence tomography and fluorescein angiography at day 14.Results: MR antagonists (MRA) favoured epithelial regeneration and nerve growth, reduced corneal angiogenesis, edema and inflammation in a rat model of CN. Transcriptomic analysis showed 75 differentially expressed genes in SPL groups. Gene set enrichment analysis highlighted pathways including wound healing and differentiation, inflammatory and immune responses, hypoxia, angiogenesis and neuroprotection. SPL upregulated Dcn, Col1a1, Timp2 and downregulated Lrg1 at day 3, and induced Pedf at day 7. Increase in DCN protein by SPL was confirmed by western blot.Conclusions: MRA regulates genes/proteins involved in anti‐inflammatory and anti‐angiogenic processes, and improves corneal re‐innervation in CN model. Dcn is one of the downstream regulated targets.

Macrophage infiltration in the cornea in a mouse model of sepsis

AbstractPurpose: To analyse the effect of a systemic inflammatory insult induced by lipopolysaccharide (LPS) administration on the cornea in mice.Methods: Male and female C57BL/6J mice were injected with a single intraperitoneal injection of LPS (5 mg/kg). Intact animals were used as control. At 21 days after LPS administration animals were sacrificed with sodium pentobarbital. Corneas were dissected as flat mounts or histological sections (16 μM) and Iba1 (microglia and macrophages) and CD45 (activated microglia and macrophages) immunodetected.Results: In LPS treated animals but not in intact ones, microglia/macrophages were found in all corneal layers while in corneal flat mounts Iba1 + Cd45+ cells were observed through the corneal surface with higher density in the periphery.Conclusions: Sepsis causes infiltration and activation of microglia/ macrophages in the murine cornea that lasts up to 21 days.

Effects of TNFα receptor TNF-Rp55- or TNF-Rp75- deficiency on corneal neovascularization and lymphangiogenesis in the mouse.

Tumor necrosis factor (TNF)α is an inflammatory cytokine likely to be involved in the process of corneal inflammation and neovascularization. In the present study we evaluate the role of the two receptors, TNF-receptor (TNF-R)p55 and TNF-Rp75, in the mouse model of suture-induced corneal neovascularization and lymphangiogenesis. Corneal neovascularization and lymphangiogenesis were induced by three 11-0 intrastromal corneal sutures in wild-type (WT) C57BL/6J mice and TNF-Rp55-deficient (TNF-Rp55d) and TNF-Rp75-deficient (TNF-Rp75d) mice. The mRNA expression of VEGF-A, VEGF-C, Lyve-1 and TNFα and its receptors was quantified by qPCR. The area covered with blood- or lymphatic vessels, respectively, was analyzed by immunohistochemistry of corneal flatmounts. Expression and localization of TNFα and its receptors was assessed by immunohistochemistry of sagittal sections and Western Blot. Both receptors are expressed in the murine cornea and are not differentially regulated by the genetic alteration. Both TNF-Rp55d and TNF-Rp75d mice showed a decrease in vascularized area compared to wild-type mice 14 days after suture treatment. After 21 days there were no differences detectable between the groups. The number of VEGF-A-expressing macrophages did not differ when comparing WT to TNF-Rp55d and TNF-Rp75d. The mRNA expression of lymphangiogenic markers VEGF-C or LYVE-1 does not increase after suture in all 3 groups and lymphangiogenesis showed a delayed effect only for TNF-Rp75d. TNFα mRNA and protein expression increased after suture treatment but showed no difference between the three groups. In the suture-induced mouse model, TNFα and its ligands TNF-Rp55 and TNF-Rp75 do not play a significant role in the pathogenesis of neovascularisation and lymphangiogenesis.

Sex differences in corneal neovascularization in response to superficial corneal cautery in the rat.

Sex-based differences in susceptibility have been reported for a number of neovascular ocular diseases. We quantified corneal neovascularization, induced by superficial silver nitrate cautery, in male and female inbred albino Sprague-Dawley, inbred albino Fischer 344, outbred pigmented Hooded Wistar and inbred pigmented Dark Agouti rats of a range of ages. Corneal neovascular area was quantified on haematoxylin-stained corneal flatmounts by image analysis. Pro-and anti-angiogenic gene expression was measured early in the neovascular response by quantitative real-time polymerase chain reaction. Androgen and estrogen receptor expression was assessed by immunohistochemistry. Male rats from all strains, with or without ocular pigmentation, exhibited significantly greater corneal neovascular area than females: Sprague-Dawley males 43±12% (n = 8), females 25±5% (n = 12), p = 0.001; Fischer 344 males 38±10% (n = 12) females 27±8% (n = 8) p = 0.043; Hooded Wistar males 32±6% (n = 8) females 22±5% (n = 12) p = 0.002; Dark Agouti males 37±11% (n = 9) females 26±7% (n = 9) p = 0.015. Corneal vascular endothelial cells expressed neither androgen nor estrogen receptor. The expression in cornea post-cautery of Cox-2, Vegf-a and Vegf-r2 was significantly higher in males compared with females and Vegf-r1 was significantly lower in the cornea of males compared to females, p<0.001 for each comparison. These data suggest that male corneas are primed for angiogenesis through a signalling nexus involving Cox-2, Vegf-a, and Vegf receptors 1 and 2. Our findings re-enforce that pre-clinical animal models of human diseases should account for sex-based differences in their design and highlight the need for well characterized and reproducible pre-clinical studies that include both male and female animals.

An Anti-VEGF-B Antibody Fragment Induces Regression of Pre-Existing Blood Vessels in the Rat Cornea.

We tested the ability of an antibody fragment with specificity for vascular endothelial growth factor-B (VEGF-B) to regress nascent and established corneal blood vessels in the rat. A single chain variable antibody fragment (scFv) with specificity for VEGF-B was engineered from the 2H10 hybridoma. Binding to rat, mouse, and human VEGF-B was confirmed by surface plasmon resonance. Activity of the anti-VEGF-B scFv on developing and established corneal blood vessels was assessed following unilateral superficial cautery in male and female outbred Sprague Dawley rats. Groups (untreated, control scFv-treated, or anti-VEGF-B scFv-treated) comprised 6 to 22 rats. Treatment consisted of 5 μL scFv, 1 mg/mL, applied topically five times per day for 14 days, or two subconjunctival injections, 50 μg scFv each, applied 7 days apart, or combined topical and subconjunctival treatment. Corneal vessel area was quantified on hematoxylin-stained corneal flat-mounts, and groups were compared using the Mann-Whitney U test, with post hoc Bonferroni correction. Immunohistochemistry for cleaved caspase-3 was performed. Topical anti-VEGF-B scFv therapy alone did not regress corneal blood vessels significantly (P > 0.05). Subconjunctival injection and combined treatment regressed 14-day established corneal blood vessels (25% reduction in vessel area [P = 0.04] and 37% reduction in vessel area [P < 0.001], respectively, compared to results in untreated controls). Cleaved caspase-3 was identified in vascular endothelial cells of anti-VEGF-B scFv-treated corneas. In scFv-treated rats, corneal endothelial cell function was maintained to 12 weeks after treatment and a normal blink reflex was present. The anti-VEGF-B scFv significantly regressed established but not developing corneal blood vessels in rats.

Label-Free In Vivo Imaging of Corneal Lymphatic Vessels Using Microscopic Optical Coherence Tomography

Corneal neovascularization, in particular lymphangiogenesis, is a limiting factor in corneal transplant survival. Novel treatment approaches focus on (selective) inhibition and regression of lymphatic vessels. Imaging clinically invisible corneal lymphatic vessels is a prerequisite for these strategies. Using a murine model, this study investigates whether corneal lymphatic vessels can be imaged using microscopic optical coherence tomography (mOCT). Corneal neovascularization was induced by intrastromal placement of 11.0 nylon sutures in one eye of BALB/c mice. After 2 weeks, cross-sectional images and volumes of the corneas with a 0.5 mm lateral and axial field of view were acquired using a custom-built mOCT system enabling a resolution of 1 μm at a B-scan rate of 165/s. Three of the six animals received an additional intrastromal injection of India ink 24 hours before the measurement to stain the corneal lymphatic system in vivo. Immunohistochemistry using CD31 and LYVE-1 was used to validate the mOCT findings. Using mOCT, lymphatic vessels were visible as dark vessel-like structures with the lumen lacking a hyperreflective wall and mostly lacking cells. However, individual, slowly moving particles, which most likely are immune cells, occasionally could be observed inside the lumen. In lymphatic vessels of ink-stained corneas, hyperreflection and shadowing underneath was observed. Ink-filled lymphatic vessels were colocalized in consecutive corneal flat mounts of the same specimen. Corneal lymphatic vessels can be imaged using mOCT. This novel approach opens new options for noninvasive clinical imaging of corneal lymphatic vessels for diagnostic and therapeutic indications.

Photodynamic Therapy Leads to Time-Dependent Regression of Pathologic Corneal (Lymph) Angiogenesis and Promotes High-Risk Corneal Allograft Survival.

Pathologic corneal (lymph) angiogenesis is a known risk factor for immune-mediated allograft rejections after corneal transplantation. However, there is no established treatment to regress pre-existing pathological corneal blood and lymphatic vessels. This study assessed the possibility to regress both vessel types by photodynamic therapy (PDT) after intravenous (i.v.) verteporfin injection, the influence of timing of PDT after verteporfin injection, and the effect on graft survival in high-risk keratoplasty. BALB/c mice were used for suture-induced inflammatory corneal neovascularization to induce combined hem- and lymphangiogenesis. The treated group received PDT 3 minutes, 1 hour, and 24 hours after an i.v. verteporfin injection (control group: phosphate buffered saline). Corneal flatmounts were excised 3 days, 1 week, and 2 weeks after corneal PDT and stained with cluster of differentiation 31 (CD31) and lymphatic vessel endothelial hyaluronan receptor 1 antibodies (LYVE-1) to quantify hem- and lymphangiogenesis. Graft survival rates were compared between high-risk recipients with and without preoperative PDT. Corneal blood vessels were significantly reduced when PDT was performed 3 minutes after i.v. verteporfin injection, whereas lymphatic vessels showed no significant difference. Both blood and lymphatic vessels were regressed when PDT was performed 1 hour or 24 hours after i.v. verteporfin application. Long-term allograft survival increased significantly in PDT-pretreated eyes when compared with controls. PDT after i.v. verteporfin injection can selectively regress pre-existing corneal blood vessels or both blood and lymphatic vessels depending on the timing of PDT after verteporfin injection. The pretreatment of recipients with PDT and i.v. verteporfin might be a promising new method to improve graft survival in high-risk eyes.

Inhibition of lymphangiogenesis in vitro and in vivo by the multikinase inhibitor nintedanib.

PurposeTo investigate the feasibility of nintedanib, a novel triple angiokinase inhibitor, for inhibiting lymphatic endothelial cell (LEC)-induced lymphangiogenesis in vitro and inflammatory corneal lymphangiogenesis in vivo.Materials and methodsMethylthiazolyldiphenyl-tetrazolium bromide (MTT) test, transwell system, and tube-formation assay were used to evaluate the effects of nintedanib on the proliferation, migration, and tube formation of LECs stimulated by vascular endothelial growth factor-C (VEGF-C), basic fibroblast growth factor (bFGF), or platelet-derived growth factor-BB (PDGF-BB). The murine model of suture-induced corneal neovascularization was used to assess the anti-hemangiogenic and anti-lymphangiogenic effects of nintedanib via systemic and topical applications. Corneal flatmounts were stained with lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1) and CD31, and the areas of involved blood and lymph vessels were analyzed morphometrically. Corneal cryosections were stained with F4/80 to evaluate inflammatory cell recruitment.ResultsWe observed a significant enhanced effect of LEC proliferation, migration, and tube formation with the administration of VEGF-C, PDGF-BB, and bFGF, respectively, which was diminished by nintedanib. Both topical and systemic applications of nintedanib inhibited suture-induced hemangiogenesis and lymphangiogenesis in the murine cornea. A reduction in F4/80+ cell infiltration was observed at day 14 after corneal suture for both systemic and topical applications of nintedanib. In comparison with controls, 61% of F4/80+ cell recruitment was inhibited via the systemic application of nintedanib, while 49% of F4/80+ cell recruitment was inhibited with the topical application of nintedanib.ConclusionNintedanib was shown to inhibit in vitro lymphangiogenesis stimulated by VEGF-C, bFGF, and PDGF-BB. Applied topically or systemically, it effectively inhibited corneal hemangiogenesis and lymphangiogenesis, accompanied by reduced inflammatory cell recruitment, which represents a new promising treatment for graft rejection after penetrating keratoplasty.

Effect of Histone Deacetylase Inhibitor, Butyroyloxymethyl-Diethyl Phosphate (AN-7), on Corneal Neovascularization in a Mouse Model.

To examine whether butyroyloxymethyl-diethyl phosphate (AN-7), a histone deacetylase inhibitor, inhibits chemically induced corneal neovascularization (NV) in mice. Corneal NV was induced in the right eye of male C57BL mice by application of a mixture of 75% silver nitrate and 25% potassium nitrate to the corneal center. Immediately thereafter, the mice were randomized into 2 groups, receiving an intraperitoneal injection of AN-7 or saline, which served as control. Corneal NV was evaluated at constant time intervals from the corneal injury by corneal photographs and the area of corneal NV was measured. Centricity and density of the corneal vascularization were graded. Corneal flat mounts blood vessels staining and histological studies were performed on day 10. Unpaired t-test was used for group comparisons. The corneal neovascular area was statistically significantly reduced by AN-7 treatment on days 10 and 14 postinjury and compared with the untreated group. The centricity and density of the corneal NV between treated and untreated groups showed no significant difference at any time point. Systemic treatment with AN-7 had a significant inhibitory effect on chemical burn-induced corneal NV in mice. These results suggest that AN-7 should be further evaluated for its therapeutic potential for the treatment of corneal NV.

Innervation of the chick embryo cornea during development

Background To understand the distribution and development of corneal nerve in animal or human has an important significance for clinical and basic research of corneal diseases.At present, some studies on cornea nerve development and location have been performed.However, the quantified study on innervation and distribution of corneal nerve fibers as embryonic development has not been reported. Objective This study attempted to understand the distribution of corneal nerve fibers in the development of chick embryo, and to evaluate the changes of the length and density of corneal nerve fibers with aging of chick embryo. Methods Whole chick corneas with limbus were obtained from chick embryo aged 6-20 days (E6-E20), and corneal nerve fiber was labeled using immunofluorescence technique by anti-neuron-specific β-Ⅲ tubulin antibody.The corneas were radially cut into 4 parts, and the integrate corneal flat mounts were prepared with the upward epithelium and mounting with anti-fade fluorescent quenching buffer glycerin containing DAPI.Fluorescence microscope was used to capture the nerve fiber images in cornea, and cornea area and the number of nerve fiber bundles were exhibited by using Photoshop CS4.Cornea nerve fiber density and total length were measured by Imaris x64 7.4.2 software. Results Total cornea flat mounts showed that the nerve bundles grew from temporal scleral forward cornea limbus at E6-E8, and the nerve fibers formed the ring surrounding by limbus during E9-E10.Then the fibers extended forward the central cornea in E11 to E15 and developed into nerve fiber plexus on the whole cornea in E16 to E20.During the period of E6-E20, the corneal surface area, the length and density of corneal nerve fibers were gradually increased with the aging of chick embryo, showing statistically significant differences among different time points (F=127.007, 227.051, 67.748, all at P<0.01). The increase of the corneal area of the chick embryo presented a strong positive correlation with the extending of length of the corneal nerve fiber (r=0.863, P<0.01). Chick corneal nerve fiber bundle appeared at E13, with a number of (59.00±1.14)/mm2 and then increased to a peak of (576.75±29.16)/mm2 at E18 and reduced to (299.67±25.46)/mm2 at E20, with a significant difference among them (F=13.759, P=0.000). Conclusions Corneal nerve starts to develop in E9 of chick embryo, and the corneal surface area, the total length of the corneal nerve fibers and the density rapidly increase concurrently with the development of chick embryo. Key words: Cornea/innervation; Nerve fibers, corneal/embryology; Development; Ophthalmic nerve/physiology; Chick embryo

Longitudinal Changes to Tight Junction Expression and Endothelial Cell Integrity in a Mouse Model of Sterile Corneal Inflammation.

We previously reported that applying toll-like receptor (TLR) ligands to an injured cornea induces corneal edema at 24 hours, which subsides by 1 week. We tested the hypotheses that endothelial expression of the tight-junction protein, zonula occludens-1 (ZO-1), would be altered during experimental sterile corneal inflammation and that endothelial cell density (ECD) would remain unaffected. Anesthetized C57BL/6J mice received central 1-mm corneal abrasions followed by topical application of saline or cytosine-phosphate-guanosine oligodeoxynucleotide (CpG-ODN, TLR-9 agonist). At 24 hours, 1 week and 4 weeks post treatment, spectral-domain optical coherence tomography images were captured. Eyes were enucleated and processed for zonula occludens-1 (ZO-1) immunofluorescent staining. Corneal flatmounts were analyzed for endothelial ZO-1 expression, cell density, polymegethism, and polymorphism. Corneal stromal inflammatory cell infiltration was evaluated at 4 weeks by immunostaining for CD45. Central corneal thickness (CCT) was increased in CpG-ODN treated eyes at 24 hours, had normalized by 1 week, but was again thickened by 4 weeks. In eyes with CpG-ODN, endothelial cell ZO-1 expression was reduced at 24 hours but returned to normal levels by 1 week. Endothelial cell density was not altered at 24 hours or 1 week. By 4 weeks, only CpG-ODN eyes showed relatively reduced ECD, as well as large numbers of CD45+ cells in the stroma. Changes to ECD correlated with CCT (r = -0.53, P < 0.01). Compared with naïve controls, more saline- and CpG-ODN-treated eyes exhibited polymegethism. This study provides novel insights into the interplay between endothelial cell integrity, corneal edema, and chronic stromal leukocyte activation during sterile corneal inflammation in mice.

Longitudinal Changes to Tight Junction Expression and Endothelial Cell Integrity in a Mouse Model of Sterile Corneal Inflammation.

PURPOSE: We previously reported that applying toll-like receptor (TLR) ligands to an injured cornea induces corneal edema at 24 hours, which subsides by 1 week. We tested the hypotheses that endothelial expression of the tight-junction protein, zonula occludens-1 (ZO-1), would be altered during experimental sterile corneal inflammation and that endothelial cell density (ECD) would remain unaffected. METHODS: Anesthetized C57BL/6J mice received central 1-mm corneal abrasions followed by topical application of saline or cytosine-phosphate-guanosine oligodeoxynucleotide (CpG-ODN, TLR-9 agonist). At 24 hours, 1 week and 4 weeks post treatment, spectral-domain optical coherence tomography images were captured. Eyes were enucleated and processed for zonula occludens-1 (ZO-1) immunofluorescent staining. Corneal flatmounts were analyzed for endothelial ZO-1 expression, cell density, polymegethism, and polymorphism. Corneal stromal inflammatory cell infiltration was evaluated at 4 weeks by immunostaining for CD45. RESULTS: Central corneal thickness (CCT) was increased in CpG-ODN treated eyes at 24 hours, had normalized by 1 week, but was again thickened by 4 weeks. In eyes with CpG-ODN, endothelial cell ZO-1 expression was reduced at 24 hours but returned to normal levels by 1 week. Endothelial cell density was not altered at 24 hours or 1 week. By 4 weeks, only CpG-ODN eyes showed relatively reduced ECD, as well as large numbers of CD45+ cells in the stroma. Changes to ECD correlated with CCT (r = −0.53, P < 0.01). Compared with naive controls, more saline- and CpG-ODN–treated eyes exhibited polymegethism. CONCLUSIONS: This study provides novel insights into the interplay between endothelial cell integrity, corneal edema, and chronic stromal leukocyte activation during sterile corneal inflammation in mice.

VesselJ: A New Tool for Semiautomatic Measurement of Corneal Neovascularization.

To quantify blood and lymph angiogenesis in mouse corneal flat mounts by means of a novel plug-in for ImageJ, called VesselJ, based on a dynamic threshold algorithm. Corneal neovascularization (CNV) was induced in the right corneas of 20 C57BL6/N mice by means of alkali burn (n = 10) or intrastromal sutures (n = 10). All corneal flat mounts were stained for blood vessels with CD31 and for lymphatics with LYVE1. Three independent operators measured blood and lymphatic CNV with both a published manual method (mCNV) and VesselJ (automatic method; aCNV). Both methods showed a strong reliability, defined as intraclass correlation coefficient (ICC) > 0.90, in quantifying hemangiogenesis for sutures and alkali burn. However, reliability of lymphatic mCNV varied from moderate in alkali burn (ICC: 0.700) to poor in sutures (ICC: 0.415), whereas it remained high in aCNV (alkali ICC: 0.996; sutures ICC: 0.959). Among sutures, a significant correlation between mCNV and aCNV was found among all the three operators for blood vessels and just for one operator for lymphatic vessels (P < 0.001). In the alkali burn model, correlation between blood mCNV and aCNV was significant for all operators after excluding three noisy flat mounts (P < 0.001), whereas no significant correlation was seen for lymphatic vessels. VesselJ is a semiautomatic, reliable, and fast method to quantify corneal hem- and lymphangiogenesis in corneal flat mounts. VesselJ can be easily used in the sutures model; it should be applied to other models (e.g., alkali burn) only after checking for background hyperfluorescence. Italian Abstract.

Inhibition of Lymphangiogenesis and Hemangiogenesis in Corneal Inflammation by Subconjunctival Prox1 siRNA Injection in Rats.

Prospero homeobox 1 (Prox1) siRNA is a small interfering RNA that is designed to specifically bind Prox1 mRNA. We determined whether Prox1 siRNA inhibits lymphangiogenesis and hemangiogenesis after acute corneal inflammation. Three Prox1 siRNAs were synthesized and investigated for their effects on Prox1 mRNA expression and tube formation in human dermal lymphatic endothelial cells (HDLECs) in vitro. The in vivo effects of Prox1 siRNA were assessed in alkali burn-induced inflammatory corneal neovascularization in rats. Prox1 siRNA was administered via subconjunctival injection. Corneal flat mounts were stained for lymphatic vessel endothelial hyaluronan receptor (LYVE)-1 to show lymphatic vessels. Lymphangiogenesis and hemangiogenesis were analyzed morphometrically using Image J software. Corneal inflammatory cell infiltration was evaluated by immunostaining for F4/80 and CD45. Protein levels of LYVE-1, podoplanin, VEGF receptor 2 (VEGFR2), and VEGFR3 were analyzed by Western blotting. Prox1 siRNA treatment decreased Prox1 mRNA expression and tube formation in cultured HDLECs. Subconjunctival injection of Prox1 siRNA significantly inhibited alkali burn-induced lymphangiogenesis and hemangiogenesis in the cornea compared with those of scrambled siRNA (negative control). This inhibition was comparable to that induced by bevacizumab (positive control). Prospero homeobox 1 knockdown by Prox1 siRNA also inhibited macrophage and leukocyte infiltration into the cornea. Prox1 siRNA downregulated the expression of all four proteins. Prox1 siRNA is a strong inhibitor of inflammatory corneal lymphangiogenesis and hemangiogenesis in vivo. Prox1 siRNA may be useful in preventing immune rejection after penetrating keratoplasty by suppressing lymphangiogenesis.

The effects of paclitaxel on angiogenesis and lymphangiogenesis in the mouse cornea.

AbstractPurpose Paclitaxel is a cytoskeletal agent that interacts with mitotic activity and inhibits microtuble disassembly. Consequently its antiproliferative effect has raised interest as antiangiogenic compound and is currently used in oncology and cardiology. Therefore we investigated the effects of paclitaxel on the angiogenesis and lymphangiogenesis process in a murine corneal neovascularization model.Methods The mouse model of suture‐induced corneal neovascularization was used to assess the anti‐hemangiogenic and anti‐lymphangiogenic effect of paclitaxel by topical application, paclitaxel coated suture. As positive control we used dexamethason eye drops and as negative control – albumin eye drops. Application of eye drops was performed (3x/day) for 2 weeks beginning at the day of the suture‐treatment. Corneal neovascularization formation (angiogenesis and lymphangiogenesis) was quantified on corneal flatmounts stained with CD31 and LYVE‐1.Results Topical applications of paclitaxel significantly inhibited the outgrowth of lymphatic vessels. In contrast, we did not detect an anti‐angiogenic effect of paclitaxel on corneal neovascularization, although the extend of corneal neovascularization was significantly reduced in animals treated with dexamethason (positive control).Conclusion Topical application of paclitaxel inhibits lymphangiogenesis in the cornea. This finding suggests a potential role of paclitaxel in the treatment of corneal diseases.

Host-Derived Endothelial Regeneration of Corneal Transplants in a Rat Keratoplasty Model

Background: It has been observed that formerly rejected opaque corneal transplants can regain clarity in the rat. We hypothesized that graft endothelium is regenerated by the host. Therefore, we used green fluorescent protein (GFP) transgenic rats to assess the origin of cells following keratoplasty. Methods: Allogeneic corneal transplantations were carried out between Fischer strain rats as graft donors and GFP-transgenic Lewis rats as recipients. In a second group, syngeneic transplantations were performed between GFP-negative Lewis donors and GFP-positive Lewis recipients, where endothelial-cell-free grafts after mechanical endothelial debridement were used. All grafts were followed up clinically for signs of opacity and rejection. After 6 weeks, corneal flatmounts counterstained with DAPI were analyzed by confocal microscopy. Results: Syngeneic transplantation of endothelial-cell-free grafts led to medium opacity levels without rejection and to subsequent clearing. All grafts showed a population of GFP-positive, host-derived endothelial cells on the graft after 6 weeks. In the allogeneic transplantation group, all grafts but one were rejected after a median of 17 days. While the graft that was not rejected maintained the GFP-negative transplant endothelium, all formerly rejected grafts showed GFP-positive endothelium on the transplant after 6 weeks, accompanied by clinical clearing of the graft. Conclusion: GPF positivity shows that in both a syngeneic and an allogeneic setting, the host-derived corneal endothelium can compensate for the endothelial cell loss of the graft. Following rejection, the grafts are repopulated by host-derived endothelial cells in the rat. This finding demonstrates a high regenerative capacity of the peripheral corneal endothelium in the rat, which should be considered whenever interpreting rat keratoplasty results.

Nerves and Neovessels Inhibit Each Other in the Cornea

To evaluate the regulatory cross-talk of the vascular and neural networks in the cornea. b-FGF micropellets (80 ng) were implanted in the temporal side of the cornea of healthy C57Bl/6 mice. On day 7, blood vessels (hemangiogenesis) and nerves were observed by immunofluorescence staining of corneal flat mounts. The next group of mice underwent either trigeminal stereotactic electrolysis (TSE), or sham operation, to ablate the ophthalmic branch of the trigeminal nerve. Blood vessel growth was detected by immunohistochemistry for PECAM-1 (CD31) following surgery. In another set of mice following TSE or sham operation, corneas were harvested for ELISA (VEGFR3 and pigment epithelium-derived factor [PEDF]) and for quantitative RT-PCR (VEGFR3, PEDF, and CD45). PEDF, VEGFR3, beta-3 tubulin, CD45, CD11b, and F4/80 expression in the cornea were evaluated using immunostaining. No nerves were detected in the areas subject to corneal neovascularization, whereas they persisted in the areas that were neovessel-free. Conversely, 7 days after denervation, significant angiogenesis was detected in the cornea, and this was associated with a significant decrease in VEGFR3 (57.5% reduction, P = 0.001) and PEDF protein expression (64% reduction, P < 0.001). Immunostaining also showed reduced expression of VEGFR3 in the corneal epithelial layer. Finally, an inflammatory cell infiltrate, including macrophages, was observed. Our data suggest that sensory nerves and neovessels inhibit each other in the cornea. When vessel growth is stimulated, nerves disappear and, conversely, denervation induces angiogenesis. This phenomenon, here described in the eye, may have far-reaching implications in understanding angiogenesis.

B-FGF Induces Corneal Blood and Lymphatic Vessel Growth in a Spatially Distinct Pattern

To study the spatial variances in ligand expression and angiogenic effect in response to the inflammatory response induced by basic fibroblast growth factor (b-FGF). b-FGF micropellets (80 ng) were implanted in the temporal side of the cornea of Balb/c mice. On days 1, 3, and 7, blood (heme-) and lymphangiogenesis were observed by immunofluorescence staining of corneal flat mounts with LYVE-1 and CD31 to identify lymphatic and blood vessels, respectively. A second group of corneas were harvested for quantitative real-time polymerase chain reaction. Each cornea was divided into 2 different areas: (1) pre-pellet area and (2) opposite-pellet area. Expression of vascular endothelial growth factor (VEGF) ligands was evaluated using real-time polymerase chain reaction in each respective zone. Blood vessels grew into the cornea from the pre-pellet area, whereas corneal lymphatic vessels grew from the opposite-pellet area toward the center of the cornea. VEGF-A was upregulated in the pre-pellet, whereas VEGF-D expression was mostly observed in the opposite-pellet area. VEGF-C level increased simultaneously in both areas. A single inducing factor, that is, b-FGF, may simultaneously provoke hemangiogenesis and lymphangiogenesis in different locations of the cornea through differential expression of VEGF ligands. This distinctive spatial pattern should be considered while evaluating the corneal predilection for inflammation beyond that which is directly visible by slit lamp examination.

Combination of vascular endothelial growth factor receptor/platelet-derived growth factor receptor inhibition markedly improves the antiangiogenic efficacy for advanced stage mouse corneal neovascularization

Pericytes, which are recruited to vessels via platelet-derived growth factor (PDGF), are linked to vessel formation and stabilization during pathological corneal neovascularization. In advanced stage, maturated vessels are restricted to anti-VEGF therapy. This study was undertaken to investigate the potential anti-angiogenesis effect of PDGF receptor inhibitor and the therapeutic effect of simultaneously targeting VEGF/PDGF signaling in advanced stage mouse corneal neovascularization. Corneal neovascularization was induced in wild-type BALB/C mice by removal of the corneal and limbal epithelia. To study the effects of anti-angiogenic inhibitor on new vessel growth prevention, mice were treated with VEGF receptor tyrosin kinase inhibitor II(anti-VEGF/VEGFR group) for 10days immediately following injury at day 0 (D0). To study the effects of anti-angiogenic inhibitors on vessel regression, mice were treated with VEGF receptor tyrosin kinase inhibitor II or PDGF receptor inhibitor AG 1296 (anti-PDGF/PDGFR group) or both (combined group) for 10days starting at day 10 (D10) post-injury. Corneas were harvested and immunostained with CD31 for endothelial cells and Ng2 for pericytes. Threshold analysis was used to calculate the area of corneal new vessels. Corneal flatmounts were studied under fluorescence microscope and confocal microscope. Mice treated with the VEGF receptor tyrosin kinase inhibitor II from D0 showed an inhibition of corneal neovascularization of 15.4% compared with untreated animals (P < 0.01). But the same amount of VEGF receptor tyrosin kinase inhibitor II had no significant anti-angiogenic effect when used at D10 (P > 0.05). Mice treated with either AG1296 or AG1296 plus VEGF receptor tyrosin kinase inhibitor II at D10 showed an inhibition of corneal neovascularization of 12.59% (P < 0.05) and 20.85% (P < 0.01) respectively. Decreased pericyte coverage and vessel density was observed in AG1296 group. Compared to the anti-VEGF/VEGFR group, only the combined therapy group showed a significant anti-angiogenesis effect (P < 0.01). Inhibition of the PDGF signal pathway results in loss of pericytes and a reduction in vessel density in advanced stage mouse corneal neovascularization. Furthermore, pericyte attenuation caused by blockade PDGF signaling can enhance the anti-angiogenesis efficacy of VEGF receptor inhibitor. Combined treatment against both endothelial cells and pericytes is required for advanced stage corneal new vessels.