Aufgrund des kornealen Immun- und (lymph)angiogenen Privileges sind Abstoßungsreaktionen nach perforierender Keratoplastik relativ selten (Niedrigrisiko-Keratoplastik) und lokale Kortikosteroide sind in der Regel ausreichend, um diese zu vermeiden. Müssen Hornhäute allerdings in stark entzündete Empfänger und/oder Empfänger mit pathologischen kornealen Neovaskularisationen transplantiert oder eine Re-Keratoplastik durchgeführt werden, steigt das Risiko einer Abstoßungsreaktion signifikant an (sog. „Hochrisiko-Keratoplastik“). Hier ist zur Prophylaxe von Abstoßungsreaktionen neben einer lokalen Kortikosteroidtherapie auch häufig eine systemische immunmodulatorische Therapie erforderlich. Aufgrund von Fortschritten in den Transplantationstechniken können die meisten Keratoplastiken heutzutage lamellär durchgeführt werden. Bei der Deep Anterior Lamellar Keratoplasty (DALK) gibt es kein Risiko einer endothelialen Transplantatabstoßung mehr, es können allerdings epitheliale, subepitheliale oder stromale Abstoßungsreaktionen auftreten. Diese sind in der Regel gut behandelbar. Das Risiko einer endothelialen Transplantatabstoßung nach Descemet Membrane Endothelial Keratoplasty (DMEK) ist im Vergleich zur perforierenden Keratoplastik signifikant geringer, verläuft in der Regel relativ mild und führt nur selten zu einem Transplantatversagen.

Pathologische korneale Neovaskularisationen des Empfängers vor Keratoplastik erhöhen signifikant das Risiko von Transplantatabstoßungen (Hockrisiko-Keratoplastik). Experimentelle Studien haben gezeigt, dass eine Reduktion kornealer Neovaskularisationen vor Hochrisiko-Keratoplastik das Transplantatüberleben verbessern kann. Diese "Präkonditionierung" des Empfängers vor Keratoplastik kann mit verschiedenen Methoden wie z. B. mittels Gefäßkauterisierung/Feinnadel-Diathermie (FND) oder kornealem Crosslinking (CXL) durchgeführt werden. Beide Methoden werden bereits in der klinischen Praxis zu diesem Zweck eingesetzt und die Ergebnisse erster Pilotstudien sind vielversprechend.

Purpose: The novel endothelial keratoprosthesis EndoArt improves corneal edema by reducing the inflow of aqueous humor into the cornea. We assessed the early outcome after EndoArt implantation in patients at a high risk of graft failure after keratoplasty. Methods: This retrospective study included 14 patients with high-risk eyes owing to at least one of the following risk factors for graft failure after keratoplasty: multiple previous surgeries (glaucoma surgery, keratoplasty) and recurrent intraocular inflammation because of uveitis, aniridia, or anterior synechia. After descemetorhexis, the EndoArt keratoprosthesis was placed on the posterior stroma, secured with a gas bubble and 1 to 3 transcorneal holding sutures. Best spectacle-corrected visual acuity and central corneal thickness were calculated preoperatively and postoperatively. In addition, detachment of the keratoprosthesis and the need for additional gas injections (rebubbling) were analyzed. Results: Octafluoropropane (C3F8) 12% in 11 patients and sulfur hexafluoride 20% in 3 patients were used to attach EndoArt. Detachments requiring at least 1 rebubbling occurred in 8 eyes. Preoperative best spectacle-corrected visual acuity was 1.6 (±0.6) logarithm of the minimal angle of resolution and improved to 1.3 (±0.6) after 12 weeks. Preoperative central corneal thickness (771.8 μm ± 157) significantly decreased postoperatively in all patients (622.1 μm ± 184.7 [P = 0.025] and 562.8 μm ± 183.6 [P = 0.012] after 6 and 12 weeks, respectively). Conclusions: EndoArt improved visual acuity and significantly reduced corneal thickness within 3 months postoperatively, subjectively, but not statistically significantly. The rebubbling rates in this cohort with an altered anterior segment anatomy were relatively high. Patients at a high risk of graft failure may benefit from this novel endothelial keratoprosthesis.

Vision is one of the most important sensory functions of all. Good vision highly depends on the transparency of the cornea, the avascular "windshield" and the most important refractive element of the eye.Loss of corneal transparency is a major cause of blindness globally, with corneal transplantation being the primary treatment. The cornea is normally free of blood and lymphatic vessels, but severe inflammation can lead to corneal neovascularization, affecting the success of a transplantation. While transplants in non‐vascularized recipient beds have very good long‐term success rates, those in so‐called high‐risk recipients with pre‐existing vascularization are much lower. In fact, rejection rates in these vascularized high‐risk eyes reach more than 50 % and even HLA matching and systemic immunosuppression in addition to standard local immunomodulation have not been able to significantly improve this poor prognosis. Therefore, there is a high unmet need for further optimization of high‐risk keratoplasty.We and other groups were able to show in preliminary work that the extent of pathological corneal neovascularization, blood and lymphatic in the recipient before keratoplasty correlates strongly with the risk of subsequent graft rejection. Based on these findings, we and others have shown that targeting blood and lymphatic vessels in pathologically vascularized eyes prior to keratoplasty can significantly improve graft survival in mouse models. This novel concept of improving graft survival by preconditioning the recipient through (lymph)angioregressive pretreatment prior to keratoplasty was subsequently validated using various models and (lymph)angioregressive approaches (such as fine needle diathermy [FND], photodynamic therapy and CXL).Based on these preclinical findings, we and others have used such angioregressive therapeutic approaches in small pilot series in patients with prevascularized high‐risk eyes and could confirm the previous results from the preclinical studies.However, it should be noted that all mentioned studies so far were retrospective in nature without internal controls and with small sample sizes.Since december 2023 we started the CrossCornealVision Study at Cologne University Eye Hospital and six further sites (University of: Berlin, Duesseldorf, Freiburg, Homburg Saar, Munich, Rostock) an exploratory investigator‐initiated trial with the purpose to improve the survival of transplanted corneal grafts by treating pathologically vascularized recipient corneas with (lymph)angioregressive therapy using corneal crosslinking (CXL) before high‐risk transplantation. Prior to high‐risk transplantation, patients will be randomized to receive either CXL or no CXL (control). Subsequently, the incidence of graft rejection after keratoplasty will be evaluated and safety evaluated. The primary endpoint is the incidence of graft rejection episodes over 24 months, while secondary endpoints include overall graft survival and regression of corneal vessels.If successful, this novel approach of graft preconditionning by (lymph)angioregressive treatment would be the first to improve graft survival in high‐risk transplants in decades and would thus significantly improve the vision and quality of life of affected patients suffering from corneal blindness.

Macrophages are critical for the innate immune defense against the facultative intracellular Gram-negative bacterium Salmo\nella enterica serovar Typhimurium. Following phagocytosis by macrophages, S. Typhimurium activates cytoplasmic NLRC3 and NLRP4 inflammasomes, which share the adaptor ASC, resulting in the secretion of the pro-inflammatory cytokine IL-1β. To prevent excessive inflammation and tissue damage, inflammatory signaling pathways are tightly controlled. Recently, autophagy has been suggested to limit inflammation by targeting activated inflammasomes for autophagic degradation. However, the importance of the autophagic adaptor Sequestome-1 (hereafter, p62) for regulating inflammasome activation remains poorly understood. We report here that p62 restricts inflammasome availability and subsequent IL-1β secretion in macrophages infected with S. Typhimurium by targeting the inflammasome adaptor ASC for autophagic degradation. Importantly, loss of p62 resulted in impaired autophagy and increased IL-1β secretion, as well as IL-10 and IFN-β release. In summary, our results demonstrate a novel role for p62 in inducing autophagy and balancing major pro- and anti-inflammatory signaling pathways to prevent excessive inflammation during S. Typhimurium infection of macrophages.

Background Good 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. Methods This 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). Discussion Based 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 registration ClinicalTrials.gov NCT05870566. Registered on 22 May 2023.

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.

Macrophages play a pivotal role in the innate immune response. While their most characteristic function is phagocytosis, it is important not to solely characterize macrophages by this activity. Their crucial roles in body development, homeostasis, repair, and immune responses against pathogens necessitate a broader understanding. Macrophages exhibit remarkable plasticity, allowing them to modify their functional characteristics in response to the tissue microenvironment (tissue type, presence of pathogens or inflammation, and specific signals from neighboring cells) swiftly. While there is no single defined “macrophage” entity, there is a diverse array of macrophage types because macrophage ontogeny involves the differentiation of progenitor cells into tissue-resident macrophages, as well as the recruitment and differentiation of circulating monocytes in response to tissue-specific cues. In addition, macrophages continuously sense and respond to environmental cues and tissue conditions, adjusting their functional and metabolic states accordingly. Consequently, it is of paramount importance to comprehend the heterogeneous origins and functions of macrophages employed in in vitro studies, as each available in vitro macrophage model is associated with specific sets of strengths and limitations. This review centers its attention on a comprehensive comparison between immortalized mouse macrophage cell lines and primary mouse macrophages. It provides a detailed analysis of the strengths and weaknesses inherent in these in vitro models. Finally, it explores the subtle distinctions between diverse macrophage cell lines, offering insights into numerous factors beyond the model type that can profoundly influence macrophage function.

Historically, the eye has been considered as an organ free of lymphatic vessels. In recent years, however, it became evident, that lymphatic vessels or lymphatic-like vessels contribute to several ocular pathologies at various peri- and intraocular locations. The aim of this review is to outline the pathogenetic role of ocular lymphatics, the respective molecular mechanisms and to discuss current and future therapeutic options based thereon. We will give an overview on the vascular anatomy of the healthy ocular surface and the molecular mechanisms contributing to corneal (lymph)angiogenic privilege. In addition, we present (i) current insights into the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea triggered e.g. by inflammation or trauma, (ii) the role of lymphatic vessels in different ocular surface pathologies such as dry eye disease, corneal graft rejection, ocular graft versus host disease, allergy, and pterygium, (iii) the involvement of lymphatic vessels in ocular tumors and metastasis, and (iv) the novel role of the lymphatic-like structure of Schlemm's canal in glaucoma. Identification of the underlying molecular mechanisms and of novel modulators of lymphangiogenesis will contribute to the development of new therapeutic targets for the treatment of ocular diseases associated with pathological lymphangiogenesis in the future. The preclinical data presented here outline novel therapeutic concepts for promoting transplant survival, inhibiting metastasis of ocular tumors, reducing inflammation of the ocular surface, and treating glaucoma. Initial data from clinical trials suggest first success of novel treatment strategies to promote transplant survival based on pretransplant corneal lymphangioregression.

The osmosensitive transcription factor nuclear factor of activated T cells 5 (NFAT5; or tonicity-responsive enhancer binding protein; TonEBP) plays a key role in macrophage-driven regulation of cutaneous salt and water balance. In the immune-privileged and transparent cornea, disturbances in fluid balance and pathological edema result in corneal transparency loss, which is one of the main causes of blindness worldwide. The role of NFAT5 in the cornea has not yet been investigated. We analyzed the expression and function of NFAT5 in naive corneas and in an established mouse model of perforating corneal injury (PCI), which causes acute corneal edema and transparency loss. In uninjured corneas, NFAT5 was mainly expressed in corneal fibroblasts. In contrast, after PCI, NFAT5 expression was highly upregulated in recruited corneal macrophages. NFAT5 deficiency did not alter corneal thickness in steady state; however, loss of NFAT5 led to accelerated resorption of corneal edema after PCI. Mechanistically, we found that myeloid cell-derived NFAT5 is crucial for controlling corneal edema, as edema resorption after PCI was significantly enhanced in mice with conditional loss of NFAT5 in the myeloid cell lineage, presumably due to increased pinocytosis of corneal macrophages. Collectively, we uncovered a suppressive role for NFAT5 in corneal edema resorption, thereby identifying a novel therapeutic target to combat edema-induced corneal blindness.

The study aims to compare outcomes after deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) in keratoconic eyes with or without previous hydrops. Retrospective analysis of 211 eyes who received PK (group 1, n = 74 [history of hydrops: n = 33]) or DALK (group 2, n = 137 [history of hydrops: n = 9]) from 2012 to 2019 at the Department of Ophthalmology, University of Cologne, Germany. Analysis included best spectacle-corrected visual acuity (BSCVA), complications, immune reactions, graft survival and keratometry, and subgroup analyses for subjects with or without previous hydrops. Follow-up was 34.0 ± 23.6 months in group 1 and 30.7 ± 22.5 months in group 2. No significant difference was found in the course of BSCVA between groups 1 and 2 (p = 0.182) and in postoperative BSCVA between eyes with and without previous hydrops, regardless of the surgical method (p = 0.768). Endothelial immune reactions occurred exclusively in group 1 and did not occur more frequently in eyes with previous hydrops (p = 0.377). A higher risk of complications for eyes with previous hydrops was observed (p = 0.022). There was no difference in astigmatism and maximum keratometry (Kmax) preoperatively and postoperatively between eyes with and without history of hydrops. The prognosis for visual outcome after keratoplasty including visual acuity, astigmatism, and Kmax for keratoconic eyes with previous hydrops is as good as for keratoconic eyes without previous hydrops, irrespective of the surgical method. However, eyes after hydrops seem to have an increased risk of complications.

Purpose: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.Methods: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.Results: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.Conclusions: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."