Deniz Hos

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.

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: NCT05870566. Registered on 22 May 2023.

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.

(Lymph)angiogenesis into the cornea prior to and after corneal transplantation is a critical risk factor for allograft rejection. Lymphatic vessels even more than blood vessels seem important in mediating immune responses, as they facilitate allograft sensitization in the draining lymph nodes. Thus, the concept of modulating lymphatic trafficking to promote corneal graft survival seems promising. A variety of approaches has been developed to inhibit progressive lymphangiogenesis in experimental settings. Recently, additionally to pharmacological approaches, clinically available techniques such as UVA-based corneal collagen crosslinking and fine needle diathermy were reported to be effective in regressing lymphatic vessels and to experimentally promote graft survival. Clinical pilot studies also suggest the efficacy of blocking antigen presenting cell trafficking to regional lymph nodes by regressing corneal lymphatic vessels to enhance allograft survival in high-risk eyes. In this article, we will give an overview of current strategies to modulate lymphatic trafficking with a special focus on recently reported strategies, which may be easy to translate into clinical practice. This novel concept of temporary, pretransplant regression of lymphatic vessels at the site of transplantation to promote subsequent corneal transplant survival (“lymphangioregressive preconditioning”) may also be applicable to other transplantation sites later.

Zusammenfassung Hintergrund Die „Descemet membrane endothelial keratoplasty“ (DMEK) als Goldstandard für die Behandlung von endothelialen Dysfunktionen führt in der Regel zu sehr guten postoperativen Ergebnissen. Inzwischen gibt es auch erste Erfahrungen zur DMEK in sog. „Hochrisikoaugen“. Methoden Es werden relevante Literatur und eigene Daten zur DMEK bei Transplantatversagen nach perforierender Keratoplastik und in vaskularisierten Hochrisikoaugen präsentiert und diskutiert. Ergebnisse Eine DMEK zur Therapie des Transplantatversagens nach perforierender Keratoplastik kommt für Augen ohne stromale Narben und ohne hohen Astigmatismus infrage. Eine retrospektive Analyse von 52 Patienten aus dem eigenen Haus zeigte, dass eine DMEK in diesen Fällen zu einem signifikanten, im Vergleich zur primären DMEK allerdings verzögerten Visusanstieg führt. Die Abstoßungs- und Transplantatversagensraten scheinen ähnlich wie nach perforierender Re-Keratoplastik und damit deutlich höher als nach primärer DMEK zu sein. Eine DMEK kann auch für Augen mit Hornhautvaskularisationen ohne stromale Narben infrage kommen. Eine eigene retrospektive Analyse von 24 Augen mit mindestens 2 vaskularisierten Hornhautquadranten zeigte, dass eine DMEK in diesen Augen zu einer signifikanten Erholung der Sehschärfe und einem deutlichen Rückgang der Hornhautvaskularisationen führt. Die Abstoßungsrate in dieser Kohorte lag bei 4,2 % und ist damit geringgradig höher als nach „Niedrigrisiko“-DMEK in Augen ohne Hornhautvaskularisationen, aber deutlich unter dem Abstoßungsrisiko einer penetrierenden Hochrisikokeratoplastik. Zusammenfassung Das Indikationsspektrum der DMEK wird zunehmend breiter. So kann die DMEK bei Transplantatversagen nach perforierender Keratoplastik eine geeignete Therapieoption mit akzeptablen Ergebnissen und deutlich schnellerer und sicherer Visuserholung sein. Weiterhin scheint die DMEK eine gute Option zur Therapie der endothelialen Dysfunktion auch bei vaskularisierten Hochrisikoaugen ohne stromale Narben zu sein.