Subsequent Corneal Transplantation Research Articles

Selective, Temporary Postoperative Inhibition of Lymphangiogenesis by Integrin α5β1 Blockade Improves Allograft Survival in a Murine Model of High-Risk Corneal Transplantation.

Background: Corneal inflammatory hem- and lymphangiogenesis significantly increase the risk for immune rejection after subsequent allogeneic corneal transplantation. The purpose of this study was to analyze the impact of temporary selective inhibition of lymphangiogenesis after transplantation on graft survival. Methods: Allogeneic transplantation from C57BL/6 mice to BalbC mice was performed as "high-risk" keratoplasty in a prevascularized corneal host bed (suture-induced inflammatory corneal neovascularization). The treatment group received integrin α5β1-blocking small molecules (JSM6427) at the time of transplantation and for two weeks afterwards. Control mice received a vehicle solution. Grafts were evaluated weekly for graft rejection using an opacity score. At the end of the follow-up, immunohistochemical staining of corneal wholemounts for lymphatic vessels as well as CD11b+ immune cells was performed. Results: Temporary postoperative inhibition of lymphangiogenesis by JSM6427 improved the corneal graft survival significantly. At the end of the follow-up, no significant reduction in CD11b+ immunoreactive cells within the graft compared to controls was found. Conclusions: The significant improvement of corneal graft survival by the selective, temporary postoperative inhibition of lymphangiogenesis after keratoplasty using integrin antagonists shows the impact of lymphatic vessels in the early postoperative phase. Retarding lymphatic vessel ingrowth into the graft might be sufficient for the shift to immunological tolerance in the postoperative period, even after high-risk keratoplasty.

UV light-mediated corneal crosslinking as (lymph)angioregressive pretreatment to promote graft survival after subsequent high-risk corneal transplantation (CrossCornealVision): protocol for a multicenter, randomized controlled trial

BackgroundGood vision highly depends on the transparency of the cornea, which is the “windscreen” of the eye. In fact, corneal blindness due to transparency loss is the second most common cause of blindness worldwide, and corneal transplantation is the main cure. Importantly, the cornea is normally avascular but can secondarily be invaded by pathological (blood and lymphatic) vessels due to severe inflammation, and the survival prognosis of a corneal graft mainly depends on the preoperative vascular condition of the recipient’s cornea. Whereas transplants placed into avascular recipient beds enjoy long-term survival rates of > 90%, survival rates significantly decrease in pathologically pre-vascularized, so-called high-risk recipients, which account for around 10% of all performed transplants in Germany and > 75% in lower and middle-income countries worldwide.MethodsThis parallel-grouped, open-randomized, multicenter, prospective controlled exploratory investigator-initiated trial (IIT) intends to improve graft survival by preconditioning pathologically vascularized recipient corneas by (lymph)angioregressive treatment before high-risk corneal transplantation. For this purpose, corneal crosslinking (CXL) will be used, which has been shown to potently regress corneal blood and lymphatic vessels. Prior to transplantation, patients will be randomized into 2 groups: (1) CXL (intervention) or (2) no pretreatment (control). CXL will be repeated once if insufficient reduction of corneal neovascularization should be observed. All patients (both groups) will then undergo corneal transplantation. In the intervention group, remaining blood vessels will be additionally regressed using fine needle diathermy (on the day of transplantation). Afterwards, the incidence of graft rejection episodes will be evaluated for 24 months (primary endpoint). Overall graft survival, as well as regression of corneal vessels and/or recurrence, among other factors, will be analyzed (secondary endpoints).DiscussionBased on preclinical and early pilot clinical evidence, we want to test the novel concept of temporary (lymph)angioregressive pretreatment of high-risk eyes by CXL to promote subsequent corneal graft survival. So far, there is no evidence-based approach to reliably improve graft survival in the high-risk corneal transplantation setting available in clinical routine. If successful, this approach will be the first to promote graft survival in high-risk transplants. It will significantly improve vision and quality of life in patients suffering from corneal blindness.Trial registrationClinicalTrials.gov NCT05870566. Registered on 22 May 2023.

Different Murine High-Risk Corneal Transplant Settings Vary Significantly in Their (Lymph)angiogenic and Inflammatory Cell Signatures.

Pathologic conditions in the cornea, such as transplant rejection or trauma, can lead to corneal neovascularization, creating a high-risk environment that may compromise subsequent transplantation. This study aimed to evaluate the impact of different types of corneal injury on hemangiogenesis (HA), lymphangiogenesis (LA) and immune cell pattern in the cornea. We used five different corneal injury models, namely, incision injury, alkali burn, suture placement, and low-risk keratoplasty, as well as high-risk keratoplasty and naïve corneas as control. One week after incision and 2 weeks after all other different injuries, corneal HA and LA were quantified by morphometric analysis. In addition, immune cell patterns of the whole cornea and the recipient rim were analyzed by immunohistochemistry. Immune cells in the draining lymph nodes (dLNs) were quantified by flow cytometry. Different types of corneal injury caused significantly different HA and LA responses (both P < 0.0001). The infiltration of corneal macrophages, dendritic cells, neutrophils, major histocompatibility complex (MHC) II+ cells, CD4+ T cells, and CD8+ T cells varied significantly in different high-risk settings (all P < 0.0001). Both the expression of MHC II on macrophages (P = 0.0005) and the frequency of MHC II+ dendritic cells (P = 0.0014) in the draining lymph nodes were significantly different across the various high-risk scenarios. Murine high-risk settings caused by different underlying pathologies vary significantly in their (lymph)angiogenic and inflammatory cell patterns. Therefore, anti(lymph)angiogenic or immunomodulatory strategies to prevent and/or treat immune responses after subsequent corneal transplantation may need to be customized according to their immune-vascular "signatures."

Mini-Conjunctival Limbal Autograft (Mini-CLAU) Using Platelet-Rich Plasma Eye Drops (E-PRP): A Case Series.

The purpose of this study was to introduce a new method of limbal stem cell transplantation using autologous platelet-rich plasma (E-PRP) eye drops for unilateral total limbal stem cell deficiency. Patients with total unilateral limbal stem cell deficiency due to chemical burn underwent mini-conjunctival limbal autograft using autologous E-PRP drops. One small limbal block, measuring 2 × 2 mm, was harvested from the patients' contralateral healthy eye and transplanted to the diseased eye. All patients received E-PRP drops until achieving complete corneal epithelialization. Subsequent corneal transplantation was performed in eyes with significant stromal opacification. Corneal buttons obtained during corneal transplantation underwent immunohistochemistry for the evaluation of limbal stem cell markers (ABCG2 and P63). Visual acuity, epithelial healing, corneal clarity, and regression of corneal conjunctivalization/vascularization were evaluated after surgery. Ten patients with acid (n = 7) or alkali (n = 3) burn were included. The mean follow-up period was 21.7 ± 5.8 months (range, 12-32 months). Corneas were completely reepithelialized within 14.9 ± 3.5 days (range, 11-21 days). Corneal conjunctivalization/vascularization dramatically regressed 1 to 2 months after surgery in all cases, and corneal clarity considerably improved in 7 patients. In the 3 eyes with significant stromal opacification, subsequent optical penetrating keratoplasty was performed. The ocular surface was stable throughout the follow-up period in all eyes. BSCVA improved to 0.60 ± 0.0.32 and 0.46 ± 0.0.25 logMAR in eyes with and without corneal transplantation, respectively, at the final follow-up visit. ABCG2 and P63 markers were detected on corneal buttons after keratoplasty. Based on our clinical and laboratory findings, mini-conjunctival limbal autograft using E-PRP can be considered as a promising alternative to ocular surface reconstruction.

One-step thermokeratoplasty for pain alleviating and pre-treatment of severe acute corneal hydrops in keratoconus.

To observe the efficacy of simplified one-step thermokeratoplasty for the treatment of severe acute corneal hydrops in keratoconus. In this retrospective, noncomparative clinical study, 10 patients (10 eyes) with acute hydrops in keratoconus were treated with simplified one-step thermokeratoplasty. Pain, changes in the corneal curvature, thickness, and size and morphology of the Descemet membrane breaks were detected before and after surgery. Eight patients were successfully treated using modified deep anterior lamellar keratoplasty (DALK). Graft transparency, visual acuity, and immunological rejection were evaluated for 6 to 12mo. Pain and corneal oedema were promptly alleviated, and the intrastromal ruptures diminished within 3 to 6wk after thermokeratoplasty. At 3 to 6wk after corneal oedema was faded, Descemet membrane breaks and intrastromal ruptures were healed. Two patients did not undergo subsequent corneal transplantation after thermokeratoplasty. Eight patients underwent DALK successfully and safely after thermokeratoplasty, without corneal perforation. Central corneal opacity faded or disappeared within 6mo. The mean best-corrected visual acuity was increased to 20/30 at 12 mo after DALK. No one was observed with any immune rejection. One-step thermokeratoplasty can successfully and efficiently accelerate the absorption of prominent corneal oedema in severe acute hydrops patients. This simple procedure with no complications can be performed in the emergency department by residents. This method can improve the safety of DALK and obtain good postoperative vision. Long-term management of acute corneal hydrops using simplified one-step thermokeratoplasty seems promising.

Effect of shunt type on rates of tube-cornea touch and corneal decompensation after tube shunt surgery in uveitic glaucoma.

To evaluate the effect of tube shunt type [Ahmed (AGV) versus Baerveldt (BGI)] on the frequency of tube-cornea touch and corneal decompensation after tube shunt surgery. This retrospective comparative study included 145 eyes of 130 patients with uveitic glaucoma who underwent AGV (75 eyes) or BGI (70 eyes) implantations. Electronic medical records were reviewed to document demographic factors, intraocular pressure (IOP) reduction, frequency of tube-cornea touch, corneal decompensation, and need for subsequent corneal transplantation. The mean follow-up was 27.7±3.3 months for AGV and 32.8±3.8 months for BGI (p=0.30). Tube-cornea touch was observed in 5 eyes after BGI and 1 eye in the AGV group (p=0.08). The BGI group reported a significantly higher rate of corneal decompensation (9 versus 0; p=0.001) and transplantation (6 versus 0; p=0.01) compared to the AGV group. Previous trabeculectomy was a significant risk factor for corneal complications in eyes undergoing BGI implantation (odds ratio [OR]= 8.17, 95% confidence interval [CI]=1.78-37.45, p=0.007). Similar rates of tube-cornea touch were observed in both shunt types; BGI shunts were associated with a greater incidence of corneal complications and transplantation as compared to AGV in this retrospective series of uveitic glaucoma cases.

Topical VEGF-C/D Inhibition Prevents Lymphatic Vessel Ingrowth into Cornea but Does Not Improve Corneal Graft Survival.

Vascular endothelial growth factor-C/D (VEGF-C/D) regulates lymphangiogenesis. Ingrowth of lymphatic vessels is negatively associated with corneal transplantation success. In this study, we therefore analyzed the effect local blockade of VEGF-C/D has on inflamed corneas. We used the murine model of suture-induced neovascularization and subsequent high-risk corneal transplantation. Mice were treated with a VEGF-C/D trap prior to transplantation. Topical inhibition of VEGF-C/D significantly reduced lymphatic vessel ingrowth, but increased Macrophage numbers in the cornea. Furthermore, corneal transplantation success was not improved by the topical application of the compound. This study demonstrates that local VEGF-C/D inhibition is insufficient to increases corneal transplantation success, likely due to interaction with immune cells.

Role of Endogenous Regulators of Hem- And Lymphangiogenesis in Corneal Transplantation.

Under normal conditions, the cornea, being the transparent “windscreen” of the eye, is free of both blood and lymphatic vessels. However, various diseases of the eye, like infections, can interfere with the balance between promoting and inhibiting factors, which leads to ingrowth of blood and lymphatic vessels. The newly formed lymphatic vessels increase the risk of graft rejection after subsequent corneal transplantation. Corneal transplantation is one of the most commonly performed transplantations worldwide, with more than 40,000 surgeries per year in Europe. To date, various anti-hem- and anti-lymphangiogenic treatment strategies have been developed specifically for the corneal vascular endothelial growth factor (VEGF) pathway. Currently, however, no treatment strategies are clinically available to specifically modulate lymphangiogenesis. In this review, we will give an overview about endogenous regulators of hem- and lymphangiogenesis and discuss potential new strategies for targeting pathological lymphangiogenesis. Furthermore, we will review recently identified modulators and demonstrate that the cornea is a suitable model for the identification of novel endogenous modulators of lymphangiogenesis. The identification of novel modulators of lymphangiogenesis and a better understanding of the signaling pathways involved will contribute to the development of new therapeutic targets for the treatment of pathological lymphangiogenesis. This, in turn, will improve graft rejection, not only for the cornea.

Local VEGF-A blockade modulates the microenvironment of the corneal graft bed.

The microenvironment plays an important role in several immunological processes. Vascular endothelial growth factor-A (VEGF-A) not only regulates angiogenesis, but is known as a modulator of the immune microenvironment. Modulating the site of transplantation might be beneficial for subsequent transplant survival. In this study, we therefore analyzed the effect that a local blockade of VEGF-A in the inflamed cornea as the graft receiving tissue has on the immune system. We used the murine model of suture-induced neovascularization and subsequent high-risk corneal transplantation, which is an optimal model for local drug application. Mice were treated with VEGFR1/R2 trap prior to transplantation. We analyzed corneal gene expression, as well as protein levels in the cornea and serum on the day of transplantation, 2 and 8weeks later. Local VEGF depletion prior to transplantation increases the expression of pro-inflammatory as well as immune regulatory cytokines only in the corneal microenvironment, but not in the serum. Furthermore, local VEGFR1/R2 trap treatment significantly inhibits the infiltration of CD11c+ dendritic cells into the cornea. Subsequent increased corneal transplantation success was accompanied by a local upregulation of Foxp3 gene expression. This study demonstrates that locally restricted VEGF depletion increases transplantation success by modulating the receiving corneal microenvironment and inducing tolerogenic mechanisms.

Novel strategies for angioregression at the ocular surface

AbstractThe normal human cornea is avascular. This avascularity is actively maintained by expression of antiangiogenic and antilymphangiogenic factors. Corneal neovascularization (NV) can occur after numerous corneal diseases and leads to decreased visual acuity and poor prognosis in subsequent corneal transplantation since corneal immune privilege is lost. We recently demonstrated that bevacizumab eye drops significantly inhibit progressive corneal angiogenesis. In contrast, limited treatment options exist for mature corneal vessels, which — because of their pericyte‐covered vessel wall—do not depend on VEGF anymore. Here, we report on the short‐ and long‐term visual acuity changes and changes in vascularized corneal area after e.g. feeder vessel coagulation combined with topical bevacizumab application for the treatment of mature pathological corneal NV . These angioregressive therapies may not only improve corneal transparency but also “preconditions” such a cornea for future keratoplasty.

Recurrent Bacterial Keratitis

To investigate the rate of recurrent bacterial keratitis, associated bacteria, and surgical intervention. Patients with suspected bacterial keratitis were identified from microbiological requests over a 16-year period between 1995 and 2010. Recurrences and number of surgical interventions were analyzed according to bacterial type. A total of 2418 patients were included, of whom 2124 (87.84%) had only one episode of keratitis, 294 (12.15%) at least two, 88 (3.63%) at least three, 40 (1.65%) at least four, and 22 (0.91%) five or more episodes. The bacterial isolation rate was 35.74% (SD 9.41%), increasing to 56.01% in patients with two or more episodes. There was an increase in the isolation of Staphylococcus aureus with increasing number of episodes (P = 0.008), and S. aureus occurred more commonly in patients with recurrent disease due to the same bacterial group (P = 0.04). Patients whose recurrent keratitis was associated with S. aureus had a higher rate of requiring subsequent corneal transplantation (7 of 10) compared to those with Enterobacteriaceae (2 of 7), Pseudomonas aeruginosa (2 of 4), streptococci (2 of 5), or coagulase-negative staphylococci (none of 8) (P = 0.02). S. aureus is particularly associated with recurrent keratitis. Identification and treatment of the possible source of the infection may be necessary to reduce the risk of recurrent disease. The potential for the autocthonous S. aureus colonizing the nasopharynx or conjunctiva or lid margin to be a reservoir for recurrent keratitis suggests that decolonization of S. aureus could be considered as a potential intervention in those patients with recurrent disease.

Novel anti(lymph)angiogenic treatment strategies for corneal and ocular surface diseases

The cornea is one of the few tissues which actively maintain an avascular state, i.e. the absence of blood and lymphatic vessels (corneal [lymph]angiogenic privilege). Nonetheless do several diseases interfere with this privilege and cause pathologic corneal hem- and lymphangiogenesis. The ingrowths of pathologic blood and lymphatic vessels into the cornea not only reduce transparency and thereby visual acuity up to blindness, but also significantly increases the rate of graft rejections after subsequent corneal transplantation. Therefore great interest exists in new strategies to target pathologic corneal (lymph)angiogenesis to promote graft survival. This review gives an overview on the vascular anatomy of the normal ocular surface, on the molecular mechanisms contributing to the corneal (lymph)angiogenic privilege and on the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea. In addition we summarize the current preclinical and clinical evidence for three novel treatment strategies against ocular surface diseases based on targeting pathologic (lymph)angiogenesis: (a) modulation of the immune responses after (corneal) transplantation by targeting pathologic (lymph)angiogenesis prior to and after transplantation, (b) novel concepts against metastasis and recurrence of ocular surface tumors such as malignant melanoma of the conjunctiva by anti(lymph)angiogenic therapy and (c) new ideas on how to target ocular surface inflammatory diseases such as dry eye by targeting conjunctival and corneal lymphatic vessels. Based on compelling preclinical evidence and early data from clinical trials the novel therapeutic concepts of promoting graft survival, inhibiting tumor metastasis and dampening ocular surface inflammation and dry eye disease by targeting (lymph)angiogenesis are on their way to translation into the clinic.

Development and progression of cataract in patients required repeated corneal transplantation.

To evaluate the incidence of cataract development in patients required repeated corneal transplantations, the types of cataract and the effect of cataract extraction on the corneal regrafts survival. The charts of all the patients that underwent repeated corneal transplantation between 1985 and 1998 were reviewed for the development of cataract after the first or subsequent keratoplasties. In all, 80 patients underwent 122 repeated corneal transplantations, of which six underwent surgery in both eyes. The average follow-up period of all the patients with repeated keratoplasty was 89.5 months from the first keratoplasty. Of 86 eyes 19 (22%) that underwent repeated keratoplasties developed cataract. The cataract developed between 1 month and 17 years (average 61.3 months) after the first transplantation. The incidence of cataract development was independent of the number of repeated keratoplasties. In certain patients, such as patients with acute and severe regraft immune rejection, the cataract progressed more rapidly. Despite different cataract extraction procedures, the grafts in 17 eyes of the 19 (89.5%) failed following cataract surgery and 16 of them underwent additional corneal regrafting. The regrafts in eight of the 16 regrafted eyes (50%) remained clear with improvement in visual acuity. At the end of the follow-up, 10 eyes of the 19 had clear regraft (53%) comparable with the rate of clear grafts in the entire regrafted group (51%, P=NS). Corneal transplantation may be a trigger for slow development of cataract over years but repeated keratoplasties did not increase the risk for cataract development. Although failure of regrafts may occur after cataract extraction, subsequent corneal transplantation has a comparable survival and visual outcome with the entire regrafted group.

Phenotypic study of a case receiving a keratolimbal allograft and amniotic membrane for total limbal stem cell deficiency

Purpose To report the expression pattern of key molecules by the reconstructed corneal epithelium after a keratolimbal allograft (KLAL) and amniotic membrane transplantation (AMT) for total limbal stem cell deficiency. Design Interventional case report. Method A 50-year-old woman with severe chemical burns in both eyes received an AMT as a temporary patch at the acute stage, and a KLAL with AMT as a graft at the chronic stage for total limbal stem cell deficiency. The corneal button removed during subsequent corneal transplantation was submitted for immunofluorescence staining with monoclonal antibodies against keratin K3, MUC5AC, connexin 43, integrins α3β1 and α6β4, and laminin 5 for comparison with a normal cornea. Results Histologically, a normal stratified corneal epithelium has five to six cell layers that lay on the thick amniotic membrane basement membrane. The phenotype was of a corneal origin, based on expression of positive keratin K3, negative MUC5AC, and positive connexin 43. Furthermore, intact basement membrane complexes were present, evidenced by positive staining to integrins α3β1 and α6β4 and to laminin 5. Conclusions A normal corneal epithelial phenotype with normal basement membrane complexes was restored after a KLAL and AMT in a case with total limbal stem cell deficiency.

Excimer laser surgery for keratoconus

Purpose: To determine whether there is increased risk associated with excimer laser surgery of primary keratoconus.Setting: Department of Ophthalmology, County Council Hospital, Ryhov, Jönköping, Sweden.Methods: Twenty-four eyes in 23 patients with keratoconus had photorefractive keratectomy (PRK) to reduce the steepness of the cone. A VISX Twenty-Twenty B laser (193 nm) was used for the treatments. Spherical ablations, cylindrical ablations, or both were used. Patients were followed for a mean of 22 months (range 6 to 46 months).Results: Fourteen patients (58%) had improved visual acuity. Eleven (46%) could manage with only spectacles, and three (13%) were fitted with contact tenses to get adequate visual function. All treated corneas healed, and no acceleration of the keratoconus was seen.Conclusion: No increased risk was associated with treating primary keratoconus with excimer laser PRK. We found that excimer laser surgery can improve vision and the ability to wear contact lenses, and it did not interfere with subsequent corneal transplantation surgery.