Vascular endothelial growth factor receptor 1 morpholino decreases angiogenesis in a murine corneal suture model

A SU6668 pure nanoparticle-based eyedrops: toward its high drug Accumulation and Long-time treatment for corneal neovascularization

Corneal neovascularization (CNV) is one of the common blinding factors worldwide, leading to reduced vision or even blindness. However, current treatments such as surgical intervention and anti-VEGF agent therapy still have some shortcomings or evoke some adverse effects. Recently, SU6668, an inhibitor targeting angiogenic tyrosine kinases, has demonstrated growth inhibition of neovascularization. But the hydrophobicity and low ocular bioavailability limit its application in cornea. Hereby, we proposed the preparation of SU6668 pure nanoparticles (NanoSU6668; size ~135 nm) using a super-stable pure-nanomedicine formulation technology (SPFT), which possessed uniform particle size and excellent aqueous dispersion at 1 mg/mL. Furthermore, mesenchymal stem cell membrane vesicle (MSCm) was coated on the surface of NanoSU6668, and then conjugated with TAT cell penetrating peptide, preparing multifunctional TAT-MSCm@NanoSU6668 (T-MNS). The T-MNS at a concentration of 200 µg/mL was treated for CNV via eye drops, and accumulated in blood vessels with a high targeting performance, resulting in elimination of blood vessels and recovery of cornea transparency after 4 days of treatment. Meanwhile, drug safety test confirmed that T-MNS did not cause any damage to cornea, retina and other eye tissues. In conclusion, the T-MNS eye drop had the potential to treat CNV effectively and safely in a low dosing frequency, which broke new ground for CNV theranostics.

A cell-permeable peptide inhibitor of p55PIK signaling alleviates suture-induced corneal neovascularization and inflammation

To prepare an ophthalmic solution with a cell-permeable TAT peptide (TAT-N24) as the main cell-permeable peptide inhibitor of p55PIK signaling and observe its therapeutic effect on suture-induced corneal neovascularization (CNV) in rats. Sprague-Dawley rats were used to establish a corneal suture (CS) model of CNV. The vehicle and 0.9% TAT-N24 ophthalmic solution was topically administered. CNV induction was assessed on the basis of the clinical performance of each group. Hematoxylin-eosin staining was used to observe pathological changes, and immunohistochemical staining and confocal immunofluorescence were used to determine the localization of factors associated with corneal tissue. The mRNA expression levels of hypoxia-inducible factor (HIF-1α), vascular endothelial growth factor (VEGF-A), nuclear transcription factor κB (NF-κB p65), tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), and interleukin (IL)-6 were determined using real-time quantitative polymerase chain reaction. Western blotting was performed to detect the protein expression levels of HIF-1α and NF-κB p65. TAT-N24 slowed CNV production and reduced the expression of HIF-1α and inflammatory factors in CS models. The mRNA levels of HIF-1α, VEGF-A, NF-kB, TNF-α, IL-1β, and IL-6 significantly decreased. Moreover, the protein levels of HIF-1α and NF-κB p65 were significantly decreased. TAT-N24 can treat CNV and ocular inflammation by inhibiting the HIF-1α/NF-κB signaling pathway in CS. In the early treatment of corneal foreign body trauma, topical application of TAT-N24 can not only reduce the inflammatory response but also inhibit corneal neovascularization.

Promotion of corneal angiogenesis by sensory neuron-derived calcitonin gene-related peptide

The normal cornea has no blood vessels but has abundant innervation. There is emerging evidence that sensory nerves, originated from the trigeminal ganglion (TG) neurons, play a key role in corneal angiogenesis. In the current study, we examined the role of TG sensory neuron-derived calcitonin gene-related peptide (CGRP) in promoting corneal neovascularization (CNV). We found that CGRP was expressed in the TG and cultured TG neurons. In the cornea, minimal CGRP mRNA was detected and CGRP immunohistochemical staining was exclusively co-localized with corneal nerves, suggesting corneal nerves are likely the source of CGRP in the cornea. In response to intrastromal suture placement and neovascularization in the cornea, CGRP expression was increased in the TG. In addition, we showed that CGRP was potently pro-angiogenic, leading to vascular endothelial cell (VEC) proliferation, migration, and tube formation in vitro and corneal hemangiogenesis and lymphangiogenesis in vivo. In a co-culture system of TG neurons and VEC, blocking CGRP signaling in the conditioned media of TG neurons led to decreased VEC migration and tube formation. More importantly, subconjunctival injection of a CGRP antagonist CGRP8-37 reduced suture-induced corneal hemangiogenesis and lymphangiogenesis in vivo. Taken together, our data suggest that TG sensory neuron and corneal nerve-derived CGRP promotes corneal angiogenesis.

Antiangiogenesis Effect of Albendazole on the Cornea

Purpose: To investigate the anti-(lymph)angiogenic and anti-inflammatory effects of albendazole and to study whether these effects are additive with bevacizumab therapy in a murine corneal suture model. Methods: Corneal neovascularization (NV) and lymphangiogenesis (LY) were compared in a corneal suture model after administration of a subconjunctival injection of albendazole, bevacizumab, dexamethasone, or phosphate-buffered saline (PBS). Immunohistochemical staining and analysis were performed in each group. Real-time polymerase chain reaction (RT-PCR) was performed to quantify the expression of inflammatory cytokines (tumor necrosis factor [TNF]-alpha and interleukin-6), vascular endothelial growth factor (VEGF)-A, VEGF-C, vascular endothelial growth factor receptor (VEGFR)-2, and VEGFR-3. To evaluate the additive effect of albendazole, corneal NV and LY were also analyzed in a combined group of albendazole and bevacizumab therapy and the additive effect was compared with that in the group of double dose of bevacizumab. Results: The albendazole group showed less NV and less LY compared with the PBS control group (P < 0.01). When albendazole was combined with bevacizumab therapy, a significant decrease in NV and LY was seen compared with bevacizumab treatment alone, and with albendazole alone (all P values <0.05). The combination group showed better antilymphangiogenesis effect than the group of double dose bevacizumab. The albendazole-treated group showed reduced expression of VEGF-A, VEGF-C, TNF-alpha, and VEGFR-2 compared with corneas from the PBS group (P value <0.05 in all respective comparisons). Conclusion: Albendazole significantly decreased NV and LY in the cornea. This beneficial effect is additively enhanced when combined with bevacizumab treatment.

Phase-specific functions of macrophages determine injury-mediated corneal hem- and lymphangiogenesis

Macrophages are critical mediators of injury-associated corneal hemangiogenesis (HA) and lymphangiogenesis (LA). Yet, molecular regulators of the hem- and lymphangiogenic potential of corneal wound macrophages are poorly understood. Using two different mouse models of acute (perforating corneal incision injury) and chronic (corneal suture placement model) corneal injury, here we identified distinct functions of early- versus late-phase corneal wound macrophages in corneal HA and LA. Whereas early-phase wound macrophages are essential for initiation and progression of injury-mediated corneal HA and LA, late-phase wound macrophages control maintenance of established corneal lymphatic vessels, but not blood vessels. Furthermore, our findings reveal that the hem- and lymphangiogenic potential of corneal wound macrophages is controlled by the type of the corneal damage. Whereas perforating corneal incision injury induced primarily wound macrophages with lymphangiogenic potential, corneal suture placement provoked wound macrophages with both hem- and lymphangiogenic potential. Our findings highlight a previously unrecognized injury-context dependent role of early- versus late-phase corneal wound macrophages with potential clinical impact on therapy development for sight-threatening corneal neovascular diseases.

RNA activating-double stranded RNA targeting flt-1 promoter inhibits endothelial cell proliferation through soluble FLT-1 upregulation

Short-activating RNA (saRNA), which targets gene promoters, has been shown to increase the target gene expression. In this study, we describe the use of an saRNA (Flt a-1) to target the flt-1 promoter, leading to upregulation of the soluble isoform of Flt-1 and inhibition of angiogenesis. We demonstrate that Flt a-1 increased sFlt-1 mRNA and protein levels, while reducing VEGF expression. This was associated with suppression of human umbilical vascular endothelial cell (HUVEC) proliferation and cell cycle arrest at the G0/G1 phase. HUVEC migration and tube formation were also suppressed by Flt a-1. An siRNA targeting Flt-1 blocked the effects of Flt a-1. Flt a-1 effects were not mediated via argonaute proteins. However, trichostatin A and 5'-deoxy-5'-(methylthio) adenosine inhibited Flt a-1 effects, indicating that histone acetylation and methylation are mechanistically involved in RNA activation of Flt-1. In conclusion, RNA activation of sFlt-1 can be used to inhibit angiogenesis.

Angiogenesis and lymphangiogenesis in corneal transplantation-A review

Corneal transplantation has been proven effective for returning the gift of sight to those affected by corneal disorders such as opacity, injury, and infections that are a leading cause of blindness. Immune privilege plays an important role in the success of corneal transplantation procedures; however, immune rejection reactions do occur, and they, in conjunction with a shortage of corneal donor tissue, continue to pose major challenges. Corneal immune privilege is important to the success of corneal transplantation and closely related to the avascular nature of the cornea. Corneal avascularity may be disrupted by the processes of angiogenesis and lymphangiogenesis, and for this reason, these phenomena have been a focus of research in recent years. Through this research, therapies addressing certain rejection reactions related to angiogenesis have been developed and implemented. Corneal donor tissue shortages also have been addressed by the development of new materials to replace the human donor cornea. These advancements, along with other improvements in the corneal transplantation procedure, have contributed to an improved success rate for corneal transplantation. We summarize recent developments and improvements in corneal transplantation, including the current understanding of angiogenesis mechanisms, the anti-angiogenic and anti-lymphangiogenic factors identified to date, and the new materials being used. Additionally, we discuss future directions for research in corneal transplantation.

Corneal Mesenchymal Stromal Cells Are Directly Antiangiogenic via PEDF and sFLT-1

Purpose

To evaluate the angiogenic properties of corneal derived mesenchymal stromal cells (Co-MSC).

Methods

Co-MSCs were extracted from human cadaver, and wild-type (C57BL/6J) and SERPINF1^−/− mice corneas. The MSC secretome was collected in a serum-free medium. Human umbilical vein endothelial cell (HUVEC) tube formation and fibrin gel bead assay (FIBA) sprout formation were used to assess the angiogenic properties of Co-MSC secretome. Complete corneal epithelial debridement was used to induce corneal neovascularization in wild-type mice. Co-MSCs embedded in fibrin gel was applied over the debrided cornea to evaluate the angiogenic effects of Co-MSCs in vivo. Immunoprecipitation was used to remove soluble fms-like tyrosine kinase-1 (sFLT-1) and pigment epithelium-derived factor (PEDF, SERPINF1 gene) from the Co-MSC secretome.

Results

Co-MSC secretome significantly inhibited HUVECs tube and sprout formation. Co-MSCs from different donors consistently contained high levels of antiangiogenic factors including sFLT-1 and PEDF; and low levels of the angiogenic factor VEGF-A. In vivo, application of Co-MSCs to mouse corneas after injury prevented the development of corneal neovascularization. Removing PEDF or sFLT-1 from the secretome significantly diminished the antiangiogenic effects of Co-MSCs. Co-MSCs isolated from SERPINF1^−/− mice had significantly reduced antiangiogenic effects compared to SERPINF1^+/+ (wild-type) Co-MSCs.

Conclusions

These results illustrate the direct antiangiogenic properties of Co-MSCs, the importance of sFLT-1 and PEDF, and their potential clinical application for preventing pathologic corneal neovascularization.

Gene therapy in corneal transplantation

Corneal transplantation is the most commonly performed organ transplantation. Immune privilege of the cornea is widely recognized, partly because of the relatively favorable outcome of corneal grafts. The first-time recipient of corneal allografts in an avascular, low-risk setting can expect a 90% success rate without systemic immunosuppressive agents and histocompatibility matching. However, immunologic rejection remains the major cause of graft failure, particularly in patients with a high risk for rejection. Corticosteroids remain the first-line therapy for the prevention and treatment of immune rejection. However, current pharmacological measures are limited in their side-effect profiles, repeated application, lack of targeted response, and short duration of action. Experimental ocular gene therapy may thus present new horizons in immunomodulation. From efficient viral vectors to sustainable alternative splicing, we discuss the progress of gene therapy in promoting graft survival and postulate further avenues for gene-mediated prevention of allogeneic graft rejection.

Corneal angiogenesis and lymphangiogenesis

PURPOSE OF REVIEW

The purpose of the present review is to describe new antilymphangiogenic treatment strategies and recent findings on strain-dependency of corneal lymphangiogenesis and the interdependency between blood and lymphatic vessel growth.

RECENT FINDINGS

Studies on mice have revealed that apart from haemangiogenesis, lymphangiogenesis can also differ markedly between several mouse strains under normal and inflammatory conditions. Although haemangiogenesis and lymphangiogenesis are closely interconnected in their spatial-temporal patterning, recent data suggest that they can also occur independently.

SUMMARY

Understanding the coordinated regulation of blood and lymphatic vessel growth and genetic factors determining lymphangiogenesis in more detail could improve the development of specifically targeted antihaemangiogenic or antilymphangiogenic strategies.

Vascular Endothelial Growth Factor Receptor 1 morpholino increases graft survival in a murine penetrating keratoplasty model

PURPOSE

This study sought to determine whether a Vascular Endothelial Growth Factor Receptor 1 (VEGFR1)-specific morpholino (MO) could decrease neovascularization, thereby enhancing murine cornea transplant survival, and if this effect is synergistic with steroid therapy.

METHODS

Graft survival, corneal neovascularization, and corneal lymphangiogenesis were compared among the VEGFR1_MO, STD MO and PBS groups following subconjunctival injection in mice that underwent normal risk penetrating keratoplasty (NR PK) and high-risk penetrating keratoplasty (HR PK). Graft survival, corneal neovascularization, and corneal lymphangiogenesis in groups treated with both VEGFR1_MO and steroid therapy were also analyzed in HR PK.

RESULTS

In NR PK, the VEGFR1_MO decreased angiogenesis, lymphangiogenesis, and increased graft survival compared with the PBS group (P = 0.055, P = 0.003, P = 0.043, respectively). In HR PK, VEGFR1_MO decreased angiogenesis, lymphangiogenesis, and increased graft survival compared with the STD MO (P = 0.000, P = 0.000, P = 0.029, respectively) and PBS groups (P = 0.004, P = 0.002, P = 0.024). In HR PK, when the VEGFR1_MO was combined with steroid therapy, a significant increase in graft survival was seen compared with steroid treatment alone (P = 0.045). The 2-month graft survival rate for HR PK was 27% in the combination group compared with 0% in the triamcinolone only group.

CONCLUSIONS

VEGFR1_MO decreased angiogenesis and lymphangiogenesis, resulting in increased graft survival in both NR PK and HR PK. This beneficial effect is synergistically enhanced with steroid treatment in HR PK.