Subconjunctival and/or intrastromal bevacizumab injections as preconditioning therapy to promote corneal graft survival

The landscape of clinical trials in corneal regeneration: A systematic review of tissue engineering approaches in corneal disease

The limited availability of a healthy donor cornea and the incidence of allograft failure led researchers to seek other corneal substitutes via tissue engineering. Exploring the trend of clinical trials of the cornea with the vision of tissue engineering provides an opportunity to reveal future potential corneal substitutes. The results of this clinical trial are beneficial for future study designs to overcome the limitations of current therapeutic approaches. In this study, registered clinical trials of bio-based approaches were reviewed for corneal regeneration on March 22, 2024. Among the 3955 registered trials for the cornea, 392 trials were included in this study, which categorized in three main bio-based scaffolds, stem cells, and bioactive macromolecules. In addition to the acellular cornea and human amniotic membrane, several bio-based materials have been introduced as corneal substrates such as collagen, fibrin, and agarose. However, some synthetic materials have been introduced in recent studies to improve the desired properties of bio-based scaffolds for corneal substitutes. Nevertheless, new insights into corneal regenerative medicine have recently emerged from cell sheets with autologous and allogeneic cell sources. In addition, the future perspective of corneal regeneration is described through a literature review of recent experimental models.

Suppression of Neovascularization by Topical and Subconjunctival Bevacizumab After High-Risk Corneal Transplantation

Purpose

To assess the effectiveness of topical and subconjunctival bevacizumab in suppressing vascularization in graft and host bed after high-risk corneal transplantation.

Design

Secondary analysis of prospective, randomized, double-blind, placebo-controlled multicentric clinical trial.

Participants

The study includes patients aged > 18 years who underwent high-risk penetrating keratoplasty, which was defined as corneal vascularization in ≥ 1 quadrants of the corneal graft and host bed, excluding the limbus.

Methods

Patients were randomized to treatment and control groups. The patients in the treatment group received subconjunctival injection of bevacizumab (2.5 mg/0.1 ml) on the day of the procedure, followed by topical bevacizumab (10 mg/ml) 4 times per day for 4 weeks. The patients in control group received injection of vehicle (0.9% sodium chloride) on the day of procedure, followed by topical vehicle (carboxymethylcellulose sodium 1%) 4 times a day for 4 weeks.

Main Outcome Measures

Vessel and invasion area of vessels in the corneal graft and host beds.

Results

This study included 56 eyes of 56 patients who underwent high-risk corneal transplantation, with equal numbers in the bevacizumab and vehicle (control) treatment groups. The mean age of patients who received bevacizumab was 61.2 ± 15.9 years, and the mean age of those treated with vehicle was 60.0 ± 16.1 years. The vessel area at baseline was comparable in the bevacizumab (16.72% ± 3.19%) and control groups (15.48% ± 3.12%; P = 0.72). Similarly, the invasion areas were also similar in the treatment (35.60% ± 2.47%) and control (34.23% ± 2.64%; P = 0.9) groups at baseline. The reduction in vessel area was significantly higher in the bevacizumab-treated group (83.7%) over a period of 52 weeks compared with the control group (61.5%; P < 0.0001). In the bevacizumab-treated group, invasion area was reduced by 75.8% as compared with 46.5% in the control group. The vessel area was similar at 52 weeks postprocedure in cases of first (3.54% ± 1.21%) and repeat (3.80% ± 0.40%) corneal transplantation in patients who received bevacizumab treatment. In the vehicle-treated patients, the vessel area was significantly higher in repeat (9.76% ± 0.32%) compared with first (8.06% ± 1.02%; P < 0.0001) penetrating keratoplasty. In the bevacizumab treatment group, invasion areas at week 52 were comparable in first (11.70% ± 3.38%) and repeat (11.64% ± 1.74%) procedures, whereas invasion area was significantly higher in repeat (27.87% ± 2.57%) as compared with first (24.11% ± 2.17%) penetrating keratoplasty in vehicle-treated patients.

Conclusions

In patients undergoing vascularized high-risk corneal transplantation, bevacizumab is efficacious in reducing vascularization of corneal graft and host bed, thereby reducing the risk of corneal graft rejection in vascularized host beds.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Current trends in the management of corneal neovascularization

PURPOSE OF REVIEW

The aim of this study was to highlight recent developments in the medical and surgical management of corneal neovascularization (NV).

RECENT FINDINGS

Improved understanding and diagnostic criteria among clinicians have led to advancements in the characterization of corneal NV and objective assessment of treatment response through ancillary imaging devices. Developments in corneal NV treatments, such as antivascular endothelial growth factor, fine needle diathermy, and photodynamic therapy, have improved treatment success rates and visual outcomes. More recent surgical treatment advancements include corneal cross-linking, endothelial keratoplasty, and mitomycin intravascular chemoembolization. Finally, a greater appreciation of the molecular pathogenesis and angiogenic factors involved in corneal NV has identified numerous potential targeted therapies in the future.

SUMMARY

The management of corneal NV has evolved to include several standalone and combination medical and surgical options. Additionally, improvements in quantifying corneal NV and understanding its molecular basis have contributed to new management strategies with improved outcomes.

Corneal transplantation: A walk to vision

Corneal diseases are a major cause of blindness in the world. Corneal transplantation has been a cornerstone in the management of several of these advanced pathologies. This article discusses the evolution of corneal transplantation over a century, its indications, complications and briefly the various surgical techniques. Such tremendous technical improvisations from total corneal transplantation to lamellar keratoplasties have generated significant interest in the ophthalmic world and garnered momentum to the fight against blindness. Armed Forces Medical Services are also in vogue more than ever in this forward surge.

Efficacy and safety of anti-vascular endothelial growth factor agents on corneal neovascularization: A meta-analysis

BACKGROUND

Corneal neovascularization (CoNV) is the second major cause of blindness. Vascular endothelial growth factor (VEGF) inhibitors, e.g., bevacizumab, have been used to prevent CoNV.

AIM

We conducted an updated systematic review and meta-analysis of clinical trials to examine the efficacy and safety of anti-VEGF in CoNV.

METHODS

A literature search was conducted using three electronic databases. Mean difference (MD), standard mean difference (SMD), and relative risk (RR) are used to estimate the effect size.

RESULTS

Nine randomized controlled and three non-randomized trials were obtained. The pooled results demonstrated a significant reduction of CoNV area/Length (SMD = -1.17, 95%CI: -1.58 to -0.75), best corrected visual acuity (MD = -0.54, 95%CI: -0.91 to -0.17), and graft rejection (RR = 0.44, 95%CI: 0.24 to 0.8) and failure (RR = 0.39, 95%CI: 0.19 to 0.78) rates in the anti-VEGF group than the placebo group. A non-significant reduction of the epithelial defect was also observed in the bevacizumab group compared with the placebo (RR = 0.56, 95%CI: 0.30 to 1.06). Compared with a placebo, the unsynthesizable trials also support that bevacizumab improves visual acuity, CoNV, graft rejection, and failure rates. Trials reporting other comparisons revealed the superiority of combined remedy with bevacizumab compared to other treatments in reducing CoNV.

CONCLUSION

Anti-VEGF agents, mainly bevacizumab, are an effective and safe treatment for CoNV of all causes and prevent corneal graft rejection and failure in corneal transplantation.

Successful regression of newly formed corneal neovascularization by subconjunctival injection of bevacizumab in patients with chemical burns

Purpose

To investigate the effect and timing of subconjunctival bevacizumab injection on inhibiting corneal neovascularization (CorNV) in patients after chemical burns.

Methods

Patients with CorNV secondary to chemical burns were involved. Two subconjunctival injections of bevacizumab (2.5 mg/0.1 mL per involved quadrant) with an interval of 4 weeks were administered, and followed up a year. The area occupied by neovascular vessels (NA), accumulative neovascular length (NL), mean neovascular diameter (ND), best-corrected visual acuity (BCVA) and intraocular pressure (IOP) were evaluated. Complication was also recorded.

Results

Eleven patients with CorNV were involved. Eight patients had a history of surgery (four had amniotic grafts, one had keratoplasty, and three had amniotic grafts and keratoplasty). Decreasing in NA, NL, and ND were statistically significant at each time point compared to the baseline (p < 0.01). CorNV that developed within 1 month was considerably regressed, and vessels with fibrovascular membranes were found to be narrower and shorter than pretreatment. BCVA improved in five patients (from one to five lines), remained unchanged in five patients, and decreased in one patient compared to pretreatment.

Conclusion

Subconjunctival bevacizumab injection has a particular potential for the regression of CorNV, especially newly formed within 1 month in patients after chemical burns.

Outcomes of mitomycin C intravascular chemoembolization (MICE) in refractory corneal neovascularization after failed keratoplasty

Corneal neovascularization is a determinant of corneal graft survival and preservation of immune privilege after keratoplasty. We report the outcomes in 2 patients with failed corneal grafts who underwent mitomycin C (MMC) intravascular chemoembolization (MICE) in the affected eye. A 30-year-old woman with failed penetrating keratoplasty (PK) in the right eye was started on prednisolone acetate eyedrops. Graft sutures were removed, and bevacizumab was injected subconjunctivally. The eye remained intermittently painful, and MICE was performed on the main feeding vessel, with regression of the vessels apparent within the first day following the procedure. The second case was a 40-year-old man who had a history of repaired penetrating injury in the left eye followed by failed PK. Prednisolone acetate eyedrops were initiated, and corneal sutures were removed. The patient failed to improve with three subconjunctival injections of bevacizumab. MICE was performed, but in this case neovascularization did not regress until 20 weeks post-procedure. MMC is thought to inhibit vascular endothelial cell proliferation, but its use in corneal injection is debated. In these cases, MICE was not associated with any concerning adverse events.

Corneal thinning following bevacizumab intrastromal injection for the treatment of idiopathic lipid keratopathy

Purpose

To describe the occurrence of corneal thinning in a patient following intrastromal injection of bevacizumab to treat lipid keratopathy.

Observations

A 36-year-old female presented with decreased vision in her right eye with central posterior corneal haze and underwent a treatment regimen including artificial tears, cyclosporine 0.05% drops, prednisolone 1% and oral Valacyclovir 1g with no improvement. Neovascularization was noted at 18 months follow up and treated with intrastromal bevacizumab injections at 24 months. The feeder vessel was attenuated at 3- and 6-months post-injection, but tomography indicated sustained thinning and flattening of the cornea at the injection site contributing to the development of irregular astigmatism.

Conclusions and Importance

Corneal thinning is an uncommon potential side effect of intrastromal bevacizumab injection that may affect postoperative visual acuity.

Bevacizumab in High-Risk Corneal Transplantation: A Pilot Multicenter Prospective Randomized Control Trial

PURPOSE

To determine the efficacy of local (subconjunctival and topical) bevacizumab (Avastin) treatment in patients undergoing vascularized high-risk corneal transplantation.

DESIGN

Pilot, prospective, randomized, double-blind, placebo-controlled clinical trial conducted at 5 clinical centers in the United States, India, and Brazil.

PARTICIPANTS

Patients aged > 18 years undergoing high-risk penetrating keratoplasty, defined as corneal neovascularization (NV) in 1 or more quadrants ≥2 mm from the limbus or extension of corneal NV to the graft-host junction in a previously failed graft.

METHODS

Patients were randomized to receive subconjunctival bevacizumab (2.5 mg/0.1 ml) or placebo at the time of surgery, followed by topical bevacizumab (10 mg/ml) or topical placebo, administered 4 times per day for 4 weeks.

MAIN OUTCOME MEASURE

The 52-week endothelial immune rejection rate.

RESULTS

Ninety-two patients were randomized to receive bevacizumab (n = 48) or control (n = 44). The 52-week endothelial rejection rate was 10% in the bevacizumab group and 19% in the control group (P = 0.20). Post hoc, extended follow-up at the lead study site showed an endothelial rejection rate of 3% in the bevacizumab group and 38% in the control group (P = 0.003). Treatment with bevacizumab was found to have a hazard ratio of 0.15 (95% confidence interval, 0.03-0.65, P = 0.01) in a post hoc Cox regression analysis.

CONCLUSIONS

In patients undergoing vascularized high-risk corneal transplantation, there was no statistically significant difference in the rate of endothelial rejection at 1 year in the bevacizumab treatment group compared with the control group. This study may have been underpowered to detect a difference between treatment groups, and taken together, our data suggest that, in the current trial design, bevacizumab has a positive but not (yet) significant effect on endothelial rejection.

Corneal Lymphangiogenesis: Current Pathophysiological Understandings and Its Functional Role in Ocular Surface Disease

The cornea is a transparent and avascular tissue that plays a central role in light refraction and provides a physical barrier to the external environment. Corneal avascularity is a unique histological feature that distinguishes it from the other parts of the body. Functionally, corneal immune privilege critically relies on corneal avascularity. Corneal lymphangiogenesis is now recognized as a general pathological feature in many pathologies, including dry eye disease (DED), corneal allograft rejection, ocular allergy, bacterial and viral keratitis, and transient corneal edema. Currently, sizable data from clinical and basic research have accumulated on the pathogenesis and functional role of ocular lymphangiogenesis. However, because of the invisibility of lymphatic vessels, ocular lymphangiogenesis has not been studied as much as hemangiogenesis. We reviewed the basic mechanisms of lymphangiogenesis and summarized recent advances in the pathogenesis of ocular lymphangiogenesis, focusing on corneal allograft rejection and DED. In addition, we discuss future directions for lymphangiogenesis research.

Corneal xenotransplantation: Where are we standing?

The search for alternatives to allotransplants is driven by the shortage of corneal donors and is demanding because of the limitations of the alternatives. Indeed, current progress in genetically engineered (GE) pigs, the introduction of gene-editing technology by clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9, and advanced immunosuppressants have made xenotransplantation a possible option for a human trial. Porcine corneal xenotransplantation is considered applicable because the eye is regarded as an immune-privileged site. Furthermore, recent non-human primate studies have shown long-term survival of porcine xenotransplants in keratoplasty. Herein, corneal immune privilege is briefly introduced, and xenogeneic reactions are compared with allogeneic reactions in corneal transplantation. This review describes the current knowledge on special issues of xenotransplantation, xenogeneic rejection mechanisms, current immunosuppressive regimens of corneal xenotransplantation, preclinical efficacy and safety data of corneal xenotransplantation, and updates of the regulatory framework to conduct a clinical trial on corneal xenotransplantation. We also discuss barriers that might prevent xenotransplantation from becoming common practice, such as ethical dilemmas, public concerns on xenotransplantation, and the possible risk of xenozoonosis. Given that the legal definition of decellularized porcine cornea (DPC) lies somewhere between a medical device and a xenotransplant, the preclinical efficacy and clinical trial data using DPC are included. The review finally provides perspectives on the current standpoint of corneal xenotransplantation in the fields of regenerative medicine.

Collagen-based scaffolds with infused anti-VEGF release system as potential cornea substitute for high-risk keratoplasty: A preliminary in vitro evaluation

Currently the only widely accepted corneal blindness treatment is human donor cornea transplantation. However, increasing shortage of donor corneas as well as high risk of rejection in some corneal diseases remain two major problems, which limit the success of corneal transplantation. Corneal neovascularization is considered as one of the main risk factors of graft failure. Different cell-free biosynthetic scaffolds fabricated from collagens or collagen-like peptides are being tested as donor cornea substitutes (DCS). Here, we report for the first-time composite biosynthetic DCS with integrated sustained release system of anti-VEGF drug, bevacizumab and their preliminary in vitro validation. We have tethered gold nanoparticles with bevacizumab and integrated into a collagen-based cell-free hydrogel scaffold. Developed grafts preserved good optical properties and were confirmed not toxic to human corneal epithelial cells. Bevacizumab has been shown to constantly releasing from the DCS up to 3 weeks and preserved its anti-angiogenic properties. These results provide background for further use of infused composite biosynthetic DCS with integrated nanosystem of bevacizumab sustained release in corneal disease accompanied by neovascularisation where conventional corneal transplantation might fail.

Anti-VEGF Treatment in Corneal Diseases

BACKGROUND

Corneal neovascularization (CN) is a clue feature of different ocular pathological conditions and can lead to corneal edema and opacification with subsequent vision loss. Vascular endothelial growth factor (VEGF), which plays a key role in new vessels formation, proliferation and migration, was found to be up-regulated in these conditions. Nowadays, it is possible to downregulate the angiogenic process by using anti-VEGF agents administered by different routes.

OBJECTIVE

To evaluate the efficacy, safety and possible future directions of anti-VEGF agents used for the treatment of CNV owing to different aetiologies.

METHODS

A computerized search of articles dealing with the topic of anti-VEGF therapy in CN was conducted in PubMed, Scopus and Medline electronic databases. The following key phrases were used: anti-VEGF agents, corneal neovascularization, bevacizumab, ranibizumab, vascular endothelial growth factor, angiogenesis.

RESULTS

The use of anti-VEGF therapy in the treatment of CN reduced pathological vessel density without causing significant side effects. Various administration routes such as topical, subconjunctival and intrastromal ones are available, and the choice depends on patient and disease characteristics. Much more effectiveness is achieved in case of early administration before mature and wellestablished vessels take place. A combined approach between various drugs including anti-VEGF agents should be adopted in those cases at higher risk of neovascularization recurrence such as chronic long-standing diseases where ischemic and inflammatory stimuli are not definitively reversed.

CONCLUSION

The efficacy and safety of anti-VEGF agents support their adoption into the daily clinical practice for the management of CN.

[Antiangiogenic therapy in high-risk keratoplasty]

PURPOSE

To analyze the effectiveness and safety of VEGF inhibitor used to improve keratoconus transplant survival in patients with corneal neovascularization as stand-alone and in combination with laser coagulation of ingrowing vessels before keratoplasty.

MATERIAL AND METHODS

The study included 56 patients (56 eyes) with corneal opacifications of various etiology complicated by corneal neovascularization (CNV). The patients were divided into three groups. The 1st group included 27 patients with diffuse CNV who were undergoing an antiangiogenic therapy using anti-VEGF drug, the 2nd group - 14 patients with stem cell CNV who underwent laser coagulation of major corneal vessels combined with subconjunctival administration of drug before keratoplasty; the control group consisted of 15 patients with mixed type CNV who were undergoing conventional treatment without antiangiogenic therapy.

RESULTS

During the follow-up (24.5±4.84 months, 4 to 25 months), transplant rejection reaction was recorded in 7 (23%) patients of the 1^st group, 5 (35%) patients of the 2^nd group and 9 (60%) patients of the control group.

CONCLUSION

Subconjunctival administration of Aflibercept as a stand-alone measure and in combination with laser coagulation of ingrowing vessels may increase the chances of transparent transplant acceptance in high-risk keratoplasty.

Early Application of Bevacizumab After Sclerocorneal Grafting for Patients With Severe Late-Stage Ocular Chemical Burns

PURPOSE

To investigate whether subconjunctival bevacizumab help prevent corneal graft neovascularization and prolong the graft survival of patients with chemical burns.

METHODS

We performed a prospective nonrandomized comparative case series study. Twenty-six eyes received subconjunctival bevacizumab (10 mg/0.4 mL) once and topical immunosuppressive agents after sclerocorneal lamellar keratoplasty as the treatment, and 13 eyes received a topical immunosuppressant alone and served as the control group. The main outcomes were a cumulative probability of graft survival, development of corneal neovascularization, and complications.

RESULTS

The postoperative follow-up time was 14.3 months (range, 2-62 mo). The cumulative graft survival time was significantly longer in the treatment group than that in the control group (42.9 ± 5.9 vs. 4.8 ± 0.7 mo; log rank < 0.001). In the treatment group, 19 of the 26 grafts (73.1%) survived as transparent with a mean follow-up of 18.7 ± 3.0 months. At the end of the follow-up, 4 grafts remained free of neovascularization, 2 developed edema without neovascularization, and 15 remained transparent with a stable ocular surface and some neovascular vessels in the peripheral transplant interface. The other 5 grafts became opaque and neovascularized. In the control group, all grafts became opaque and neovascularized within the follow-up period (5.5 ± 0.7 mo). During the follow-up, a corneal epithelial defect developed in 9 eyes in the treatment group and 7 in the control group.

CONCLUSIONS

Early application of subconjunctival bevacizumab after sclerocorneal lamellar keratoplasty can significantly prevent corneal neovascularization and promote graft survival for severe late-stage ocular chemical burns.

Regression of corneal neovascularization: Adiponectin versus bevacizumab eye drops

PURPOSE

Comparing the effect of adiponectin versus bevacizumab in decreasing corneal neovascularization.

METHODS

This study was conducted on 30 eyes of 30 New Zealand Albino male rabbits. Corneal neovascularization was induced by a single 7-0 silk suture 2 mm long and 1 mm in front of the limbus for 2 weeks. Rabbits were randomly divided into three groups of adiponectin (20 µg/mL), bevacizumab (5 mg/mL) and artificial tears. The treatments continued up to 14 days.

RESULTS

At the end of 14 days, the average length of vessels in rabbits treated with adiponectin, bevacizumab and control groups decreased from 2.12 ± 0.32 mm to 0.89 ± 0.46 mm (57.68% ± 19.98%) (P < 0.001), 2.30 ± 0.41 mm to 1.30 ± 0.58 mm (42.49% ± 27.17%) (P = 0.048) and from 2.12 ± 0.44 mm to 1.81 ± 0.42 mm (14.81% ± 5.64%) (P = 0.112), respectively. The length of vessels decreased 57.68% ± 19.98% and 42.49% ± 27.17% in adiponectin versus bevacizumab groups, respectively (P = 0.527). The average surface area of vessels in rabbits treated with adiponectin, bevacizumab and control groups reduced from 5.02 ± 1.50 mm² to 1.40 ± 0.75 mm² (70.64% ± 17.76%) (P < 0.001) 0.34 ± 1.1 mm² to 2.80 ± 1.04 mm² (48.24% ± 19.23%) (P = 0.039) and 5.12 ± 2.92 mm² to 4.4 ± 2.55 mm² (14.68% ± 4.19%) (P = 0.117). Mean surface area of vascularization decreased 70.64% ± 17.76% and 48.24% ± 19.23% in adiponectin versus bevacizumab, respectively (P = 0.013).

CONCLUSIONS

The results of this study suggest that topical adiponectin can decrease recent corneal neovascularization.

Immune reactions after modern lamellar (DALK, DSAEK, DMEK) versus conventional penetrating corneal transplantation

In the past decade, novel lamellar keratoplasty techniques such as Deep Anterior Lamellar Keratoplasty (DALK) for anterior keratoplasty and Descemet stripping automated endothelial keratoplasty (DSAEK)/Descemet membrane endothelial keratoplasty (DMEK) for posterior keratoplasty have been developed. DALK eliminates the possibility of endothelial allograft rejection, which is the main reason for graft failure after penetrating keratoplasty (PK). Compared to PK, the risk of endothelial graft rejection is significantly reduced after DSAEK/DMEK. Thus, with modern lamellar techniques, the clinical problem of endothelial graft rejection seems to be nearly solved in the low-risk situation. However, even with lamellar grafts there are epithelial, subepithelial and stromal immune reactions in DALK and endothelial immune reactions in DSAEK/DMEK, and not all keratoplasties can be performed in a lamellar fashion. Therefore, endothelial graft rejection in PK is still highly relevant, especially in the "high-risk" setting, where the cornea's (lymph)angiogenic and immune privilege is lost due to severe inflammation and pathological neovascularization. For these eyes, currently available treatment options are still unsatisfactory. In this review, we will describe currently used keratoplasty techniques, namely PK, DALK, DSAEK, and DMEK. We will summarize their indications, provide surgical descriptions, and comment on their complications and outcomes. Furthermore, we will give an overview on corneal transplant immunology. A specific focus will be placed on endothelial graft rejection and we will report on its incidence, clinical presentation, and current/future treatment and prevention options. Finally, we will speculate how the field of keratoplasty and prevention of corneal allograft rejection will develop in the future.

Programmed Cell Death 1 (PD-1) Inhibitors in Renal Transplant Patients with Advanced Cancer: A Double-Edged Sword?

Given advancements in cancer immunity, cancer treatment has gained breakthrough developments. Immune checkpoint inhibitors, such as programmed cell death 1 (PD-1) inhibitors, are the most promising drugs in the field and have been approved to treat various types of cancer, such as metastatic melanoma, head and neck squamous cell carcinoma, and urothelial carcinoma. However, whether PD-1 inhibitors should be administered to renal transplant patients with advanced cancer remains unclear because the T-cells produced after administration of these inhibitors act against not only tumor antigens but also donor alloantigens. Thus, the use of PD-1 inhibitors in kidney-transplanted patients with advanced cancer is limited on account of the high risk of graft failure due to acute rejection. Hence, finding optimal treatment regimens to enhance the tumor-specific T-cell response and decrease T-cell-mediated alloreactivity after administration of a PD-1 inhibitor is necessary. Thus far, no recommendations for the use of PD-1 inhibitors to treat cancer in renal transplant patients are yet available, and very few cases reporting kidney-transplanted patients treated with PD-1 inhibitors are available in the literature. Therefore, in this work, we review the published cases and suggest feasible approaches for renal transplant patients with advanced malignancy treated by a PD-1 inhibitor. Of the 22 cases we obtained, four patients maintained intact grafts without tumor progression after treatment with a PD-1 inhibitor. Among these patients, one maintained steroid dose before initiation of anti-PD1, two received immunosuppressive regimens with low-dose steroid and calcineurin inhibitor (CNI)-elimination with sirolimus before initiation of anti-PD-1 therapy, and one received combined anti-PD-1, anti-vascular endothelial growth factor (VEGF), and chemotherapy with unchanged immunosuppressive regimens. mammalian target of rapamycin (mTOR) inhibitors and anti-VEGF may act as regulators of tumor-specific and allogenic T-cells. However, more studies are necessary to explore the optimal therapy and ensure the safety and efficacy of PD-1 inhibitors in kidney-transplanted patients.

Therapeutic approaches for induction of tolerance and immune quiescence in corneal allotransplantation

The cornea is the most commonly transplanted tissue in the body. Corneal grafts in low-risk recipients enjoy high success rates, yet over 50% of high-risk grafts (with inflamed and vascularized host beds) are rejected. As our understanding of the cellular and molecular pathways that mediate rejection has deepened, a number of novel therapeutic strategies have been unveiled. This manuscript reviews therapeutic approaches to promote corneal transplant survival through targeting (1) corneal lymphangiogenesis and hemangiogenesis, (2) antigen presenting cells, (3) effector and regulatory T cells, and (4) mesenchymal stem cells.

Transcriptome Profiling of Neovascularized Corneas Reveals miR-204 as a Multi-target Biotherapy Deliverable by rAAVs

Corneal neovascularization (NV) is the major sight-threatening pathology caused by angiogenic stimuli. Current drugs that directly target pro-angiogenic factors to inhibit or reverse the disease require multiple rounds of administration and have limited efficacies. Here, we identify potential anti-angiogenic corneal microRNAs (miRNAs) and demonstrate a framework that employs discovered miRNAs as biotherapies deliverable by recombinant adeno-associated viruses (rAAVs). By querying differentially expressed miRNAs in neovascularized mouse corneas induced by alkali burn, we have revealed 39 miRNAs that are predicted to target more than 5,500 differentially expressed corneal mRNAs. Among these, we selected miR-204 and assessed its efficacy and therapeutic benefit for treating injured corneas. Our results show that delivery of miR-204 by rAAV normalizes multiple novel target genes and biological pathways to attenuate vascularization of injured mouse cornea. Importantly, this gene therapy treatment alternative is efficacious and safe for mitigating corneal NV. Overall, our work demonstrates the discovery of potential therapeutic miRNAs in corneal disorders and their translation into viable treatment alternatives.

Blockade of angiopoietin-2/Tie2 signaling pathway specifically promotes inflammation-induced angiogenesis in mouse cornea

AIM

To investigate angiopoietin-2 (Ang-2)/Tie2 signaling pathway involving in inflammatory angiogenesis.

METHODS

Three interrupted 11-0 nylon sutures were placed into the corneal stroma of BALB/c mice (6wk old) to induce inflammatory neovascularization. Expression of Ang-2 and Tie2 protein on neovascularization were examined by immunofluorescence. The dynamic expression of Ang-2 mRNA on neovascularization was examined by quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Finally, the mouse model of suture-induced corneal neovascularization was used to assess the role of Ang-2/Tie2 signaling pathway in inflammatory angiogenesis by systemic application of L1-10, an Ang-2 specific inhibitor. Mouse corneal hemangiogenesis were evaluated by whole mount immunofluorescence.

RESULTS

Both Ang-2 and Tie2 were expressed on newly generated blood vessels in inflammatory cornea. Ang-2 expression was gradually upregulated around 2wk following injury, which was concurrent with an increased number of blood vessels. Blockade of Ang-2/Tie2 signaling pathway obviously promoted angiogenesis in inflammatory cornea.

CONCLUSION

Ang-2/Tie2 signaling pathway seems to play an important role during angiogenesis in inflammatory cornea. This may open new therapeutic applications in pathological processes such as corneal graft survival, wound healing and carcinogenesis.

Update on the Management of High-Risk Penetrating Keratoplasty

PURPOSE OF REVIEW

In this article, we review the indications and latest management of high-risk penetrating keratoplasty.

RECENT FINDINGS

Despite the immune-privilege status of the cornea, immune-mediated graft rejection still remains the leading cause of corneal graft failure. This is particularly a problem in the high-risk graft recipients, namely patients with previous graft failure due to rejection and those with inflamed and vascularized corneal beds. A number of strategies including both local and systemic immunosuppression are currently used to increase the success rate of high-risk corneal grafts. Moreover, in cases of limbal stem cell deficiency, limbal stem cells transplantation is employed.

SUMMARY

Corticosteroids are still the top medication for prevention and treatment in cases of corneal graft rejection. Single and combined administration of immunosuppressive agents e.g. tacrolimus, cyclosporine and mycophenolate are promising adjunctive therapies for prolonging graft survival. In the future, cellular and molecular therapies should allow us to achieve immunologic tolerance even in high-risk grafts.

Management of high-risk corneal transplantation

The cornea is the most commonly transplanted tissue in medicine. The main cause of corneal graft failure is allograft rejection. The incidence of graft rejection depends on the presence of high-risk characteristics, most notably corneal neovascularization. Although corneal grafting has high success rates in the absence of these risk factors, high-risk keratoplasty is associated with low success rates because of a high incidence of immune-mediated graft rejection. To improve the survival of high-risk corneal transplantation, various preoperative, intraoperative, and postoperative measures can be considered; however, the key step in the management of these grafts is the long-term use of local and/or systemic immunosuppressive agents. Although a number of immunosuppressive agents have been used for this purpose, the results vary significantly across different studies. This is partly due to the lack of an optimized method for their use, as well as the lack of a precise stratification of the degree of risk in each individual patient. New targeted biologic treatments, as well as tolerance-inducing methods, show promising horizons in the management of high-risk corneal transplantation in near future.

[Management of corneal neovascularization prior to corneal transplantation: Report of 112 cases]

INTRODUCTION

The avascular nature of the cornea results from a balance between angiogenic factors and anti-angiogenic factors. Under pathological conditions, this homeostasis can be disturbed, resulting in the onset of corneal neovascularization. The purpose of our study was to report our experience in the management of corneal neovascularization prior to keratoplasty.

MATERIALS AND METHODS

This is a prospective study of 112 patients with corneal neovascularization and candidates for possible corneal transplant.

RESULTS

The average age of patients was 38 years, ranging from 15 to 72 years. The etiologies of neovascularization were dominated by ocular trauma (26.8 %). In total, 48.33 % of patients had superficial neovascularization, 18.52 % moderately deep and 33.2 % deep neovascularization. All patients received topical corticosteroids, 29.4 % received subconjunctival injections of bevacizumab, and 22.32 % intrastromal bevacizumab injections. Clinical course was marked by a decrease in the percentage of corneal neovascularization compared to the total corneal surface area, from 45 % (between 16 and 82 %) to 28 % (between 0 and 69 %) at Day 120. There was no statistically significant improvement in visual acuity.

DISCUSSION

Corneal neovascularization is a major risk factor for graft rejection; its management is crucial prior to every keratoplasty.

CONCLUSION

Corneal neovascularization can lead to increased risk of graft rejection. Proper management increases the success rate of penetrating keratoplasty.

Three-year corneal graft survival rate in high-risk cases treated with subconjunctival and topical bevacizumab

PURPOSE

To evaluate the effect of combined subconjunctival and topical bevacizumab treatment on corneal graft survival rate in high-risk eyes.

METHODS

Prospective, consecutive, interventional case series. Fifty eyes of 50 high-risk patients scheduled for penetrating keratoplasty (PK) were included in the study; two Stevens-Johnson syndromes (SJS), five corneal combustions due to chemical burn, seven post-traumatic vascularised leucomas, 11 post-infectious vascularised leucomas, 19 rejected grafts and six corneal ulcers. Additional surgeries such as autologous limbal stem cell and/or amniotic membrane transplantation were performed together with PK in ten cases. All eyes received subconjunctival injection of 0.5 ml bevacizumab (25 mg/ml) after PK. Eyes with more than two quadrants of neovascularisation (NV) received bevacizumab drops (25 mg/ml) postoperatively for up to 12 weeks. Donor grafts were followed up for best-corrected visual acuity, graft clarity, change in NV, endothelial cell density loss (ECD), and adverse events. Mean follow-up was 36.5 months (range 32-61).

RESULTS

Best-corrected visual acuity increase was statistically significant in 82 % (41/50) of eyes 3 years after PK (paired t-test, p = 0.02). Thirty-five (70 %) high-risk grafts remained clear throughout the 3-year follow-up period. Decrease of corneal NV was observed in 84 % (42/50) of eyes treated with bevacizumab. ECD changed from preoperative 2,864 ± 301 down to 1,905 ± 187 cells/mm(2) at 3 postoperative years. A non-healing epithelial defect was recorded in one patient with SJS after 12 weeks of topical bevacizumab.

CONCLUSION

Combined subconjunctival and topical bevacizumab treatment may improve corneal graft survival rate in the majority of high-risk cases.