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Purpose: To describe a novel corneal surgical technique combining Deep Anterior Lamellar Keratoplasty (DALK) with grafting of allogeneic limbus (Limbo-DALK) for the treatment of eyes with corneal stromal pathology and limbal stem cell deficiency (LSCD)., Methods: Clinical records of six Limbo-DALKs performed in five patients diagnosed with LSCD and corneal stromal pathology requiring keratoplasty were retrospectively reviewed. All patients were diagnosed with LSCD due to various pathologies including thermal and chemical burns, congenital aniridia or chronic inflammatory ocular surface disease. Parameters analysed included demographics, diagnoses, clinical history, thickness measurements using anterior segment OCT, visual acuity, and epithelial status. Regular follow-up visits were scheduled at 6 weeks as well as 3, 6, 9, and 12 and 18 months postoperatively. Main outcome measures were time to graft epithelialisation and the occurrence of corneal endothelial decompensation., Results: Two grafts showed complete epithelial closure at 2 days, two at 14 days. In one eye, complete epithelial closure was not achieved after the first Limbo-DALK, but was achieved one month after the second Limbo-DALK. No endothelial decompensation occurred except in one patient with silicone oil associated keratopathy. Endothelial graft rejection was not observed in any of the grafts., Conclusion: Based on the data from this pilot series, limbo-DALK appears to be a viable surgical approach for eyes with severe LSCD and corneal stromal pathology, suitable for emergency situations (e.g. corneal ulceration with impending corneal perforation), while minimising the risk of corneal endothelial decompensation., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Schöneberger et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Angiogenesis and immune protection are essential at the onset of tumorigenesis. Angiogenesis serves to nourish the tumor, and prevention of immune defenses, for example, by dendritic cells (DCs), allows tumor growth. In this study, we investigated whether there are factors with dual functions that are both angiogenic and immunomodulatory and represent a therapeutic target. We analyzed 1) innate immune responses intratumorally and in draining lymph nodes and 2) angiogenic factors in conjunctival melanoma (CM), a potentially lethal malignant tumor at the ocular surface whose immune and vascular responses are largely unknown. For this purpose, an HGF-Cdk4R24C model in immunocompetent C57BL/6 mice was used and revealed that CD103- type 2 classical DC (cDC2s) were the most abundant DC subtype in healthy conjunctiva, whereas in CM, CD103- cDC2s, CD103+ type 1 cDCs, monocyte-derived DCs, and plasmacytoid DCs were significantly increased. In our analysis of angiogenic factors in CM, the examination of 53 angiogenesis-related factors that might interact with DCs identified osteopontin (OPN) as a major tumor-derived protein that interacts with DCs. Consistent with these findings, 3) a dual therapeutic strategy that inhibited tumor cell function by an OPN blocking Ab while enhancing the immune response by cDC2 vaccination resulted in 35% failure of tumor development. Moreover, tumor progression, monocyte-derived DC infiltration, and intratumoral angiogenesis were significantly reduced, whereas survival and CD8+ T cell infiltration were increased in treated mice compared with the control group. Therefore, we identified OPN blockade in combination with cDC2 vaccination as a potential future therapeutic intervention for early stages of CM by combining antiangiogenic and host immune stimulating effects., (Copyright © 2024 by The American Association of Immunologists, Inc.)

Purpose: The aim of this study was to assess the long-term outcome of excimer laser phototherapeutic keratectomy (PTK) for treating remaining anterior corneal opacities after Descemet membrane endothelial keratoplasty (DMEK)., Methods: This cohort study analyzed 67 eyes of 66 patients undergoing PTK in addition to and after DMEK between 2012 and 2021 at the Department of Ophthalmology, University of Cologne. Patients who were treated by PTK after previous DMEK on the same eye were included. The outcome parameters were best corrected visual acuity (BCVA), changes in refraction, endothelial cell density, corneal densitometry, central corneal thickness, and total corneal higher order aberrations. Patients with visual limitations in addition to anterior opacification were analyzed separately for their visual outcome. Eyes with severe visual limitations that have a very limited visual potential were excluded from the study. In addition, patients with not at least 1 postoperative follow-up examination were excluded from the study., Results: In this study, 67 eyes of 66 patients met all inclusion criteria. The median follow-up period was 13.1 (quartiles: 4.1; 30.7; interquartile range 26.6) months. The mean (±SD) BCVA improved from (logarithm of the minimum angle of resolution) 0.54 (±0.32) to 0.38 (±0.27) at the first postoperative visit ( P < 0.001) and remained significantly improved at all follow-up examinations compared with preoperative BCVA. Refraction and endothelial cell density did not change significantly after PTK. There was a significant decrease in corneal backscatter in the anterior corneal layer ( P < 0.001), and the total higher order aberration ( P = 0.02) and central corneal thickness were significantly reduced at the most recent postoperative visit ( P < 0.001). No immune reactions were observed., Conclusions: Excimer laser PTK after DMEK for persisting anterior corneal opacities has the potential to significantly improve patients' vision without affecting refractive parameters or endothelial cell density., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Background: Congenital corneal opacities are comparatively rare diseases with high amblyogenic potential., Purpose: The present work provides an overview of the diagnostics, clinical aspects and genetics of congenital corneal opacities., Methods: A literature search was carried out to compile an overview and illustration with own clinical case examples., Results: Differentiated diagnostics are of high importance in the treatment of patients with congenital corneal opacities. A close cooperation between the medical departments involved and also the parents is absolutely essential. The structured classification of congenital corneal opacities provides the basis for a targeted treatment., Discussion: The causes and the clinical symptoms of congenital corneal opacities are manifold. The correct diagnosis should be made early and in an interdisciplinary manner. Based on this, conservative and surgical treatment measures can be planned and an impending development of amblyopia can be specifically counteracted., (© 2022. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

Background: Due to the risk of amblyopia congenital and infantile corneal opacities have a narrow therapeutic window, frequently with a complex surgical treatment., Objective: The present study gives an overview of the current treatment options for congenital and infantile corneal opacities., Methods: The results of a literature search are presented and own clinical data and examples are shown., Results: In children ophthalmologic operations are surgically more demanding and the prognosis is generally worse. Surgical options include phototherapeutic keratectomy, crosslinking, corneal sutures, sectoral iridectomy, block excision and lamellar, penetrating, and auto-keratoplasty. An equally important part of the treatment is conservative treatment, when necessary with bandage lenses, glasses, contact lenses and occlusion., Discussion: Whenever possible treatment of congenital and infantile corneal opacities should be limited to the affected layers/areas. Nevertheless, children and parents have to be prepared for many examinations, sometimes with the patient under anesthesia and should be well-informed about the prognosis and the risks., (© 2022. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

Conjunctival melanoma (CM) accounts for 5% of all ocular melanomas and arises from malignantly transformed melanocytes in the conjunctival epithelium. Current therapies using surgical excision in combination with chemo- or cryotherapy still have high rates for recurrences and metastatic disease. Lately, novel signal transduction-targeted and immune checkpoint inhibitors like cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors, programmed cell death protein-1 (PD-1) receptor inhibitors, BRAF- or MEK-inhibitors for systemic treatment of melanoma have improved the outcome even for unresectable cutaneous melanoma, improving patient survival dramatically. The use of these therapies is now also recommended for CM; however, the immunological background of CM is barely known, underlining the need for research to better understand the immunological basics when treating CM patients with immunomodulatory therapies. Immune checkpoint inhibitors activate tumor defense by interrupting inhibitory interactions between tumor cells and T lymphocytes at the so-called checkpoints. The tumor cells exploit these inhibitory targets on T-cells that are usually used by dendritic cells (DCs). DCs are antigen-presenting cells at the forefront of immune response induction. They contribute to immune tolerance and immune defense but in the case of tumor development, immune tolerance is often prevalent. Enhancing the immune response via DCs, interfering with the lymphatic pathways during immune cell migration and tumor development and specifically targeting tumor cells is a major therapeutic opportunity for many tumor entities including CM. This review summarizes the current knowledge on the function of lymphatic vessels in tumor growth and immune cell transport and continues to compare DC subsets in CM with related melanomas, such as cutaneous melanoma and mucosal melanoma.

To discuss and evaluate new technologies for a better diagnosis of corneal diseases and limbal stem cell deficiency, the outcomes of a consensus process within the European Vision Institute (and of a workshop at the University of Cologne) are outlined. Various technologies are presented and analyzed for their potential clinical use also in defining new end points in clinical trials. The disease areas which are discussed comprise dry eye and ocular surface inflammation, imaging, and corneal neovascularization and corneal grafting/stem cell and cell transplantation. The unmet needs in the abovementioned disease areas are discussed, and realistically achievable new technologies for better diagnosis and use in clinical trials are outlined. To sum up, it can be said that there are several new technologies that can improve current diagnostics in the field of ophthalmology in the near future and will have impact on clinical trial end point design., (© 2020 S. Karger AG, Basel.)

Purpose: To assess the long-term outcome of Descemet membrane endothelial keratoplasty (DMEK) following failed penetrating keratoplasty (PK)., Methods: Retrospective review of 1840 consecutive DMEK surgeries from the prospective Cologne DMEK database performed between 07/2011 and 08/2017 at the Department of Ophthalmology, University of Cologne., Results: Fifty-two eyes received a DMEK surgery after failed PK. Main indications for initial PK were Fuchs endothelial corneal dystrophy (23.1%), keratoconus and herpetic keratitis (each 15.4%). Best-corrected visual acuity (BCVA) at 3, 6 and 12 months was 0.72 ± 0.39 (n = 33), 0.56 ± 0.36 (n = 32) and 0.38 ± 0.28 (n = 23), respectively. Two- and 3-year BCVA was 0.37 ± 0.21 (n = 21) and 0.32 ± 0.18 (n = 10). Mean improvement in visual outcome in logMAR lines was +4.3 ± 3.4 at 6 months, +5.0 ± 3.6 at 12 months, +6.0 ± 2.3 at 24 months and +5.4 ± 2.7 at 36 months, respectively. 59.6% received at least one rebubbling and 40.4% did not necessitate a rebubbling. Endothelial cell density (ECD)-decrease at 6 months was 36% (n = 17), 37% at 12 months (n = 17), 40% at 2 years (n = 8) and 32% at 3 years (n = 2). 34.6% of transplants needed a regraft., Conclusion: Descemet membrane endothelial keratoplasty (DMEK) is a feasible treatment option after failed PK having a relatively good long-term outcome., (© 2020 The Authors. Acta Ophthalmologica published by John Wiley & Sons Ltd on behalf of Acta Ophthalmologica Scandinavica Foundation.)

Purpose: Avascular tissues can be used to identify antilymph- or antihemangiogenic factors. The human sclera-the outer covering layer of the eye, lacks lymphatic vessels and contains only a superficial network of blood vessels and was used here to identify endogenous antiangiogenic factors., Methods: Expression levels of a panel of 96 known pro- and antiangiogenic factors were analyzed in 12 scleral or conjunctival control samples from normal human donors using real-time PCR. In vitro, scleral homogenate was cocultured with blood- and lymphatic endothelial cells (BECs and LECs) and immunohistochemistry was performed of scleral fibroblasts and BECs., Results: Three antiangiogenic factors were significantly upregulated in the human sclera compared to the conjunctiva, including FBLN5 (fibulin 5), SERPINF1 (serpin peptidase inhibitor, clade F, member 1 = pigment epithelium derived factor) and TIMP2 (Tissue inhibitor of metalloproteinases 2). Six proangiogenic factors were significantly downregulated in the sclera, including FLT4 (Fms-related tyrosine kinase 4=VEGF-R3), HGF (hepatocyte growth factor), KIT (CD117 / c-kit), PROX1 (prospero homeobox 1), SEMA3F (semaphorin-3F) and TGFA (transforming growth factor alpha). In vitro, scleral homogenate inhibited the growth of both BECs and LECs. Immunohistochemistry labeling of three major antiangiogenic factors from scleral tissue confirmed TIMP3 and PEDF expression both in scleral fibroblasts and in blood endothelial cells, whereas TIMP2 was not detectable., Conclusion: Balancing anti- and proangiogenic factors actively regulates human scleral avascularity, inhibits endothelial cell growth in vitro, and thus may help maintaining the vascular privilege of the inner eye.

Purpose: The sclera is mainly made of collagen and fibroblasts. The aim of this study was to analyze whether immune cells are present in the healthy human sclera., Methods: Ten human anterior episcleral or stromal tissue samples from globe donors were immunohistochemically examined using confocal microscopy. The expression of the macrophage markers CD68, CD163 and CD11b, CD45 (a general leukocyte marker), MHCII (expressed by antigen-presenting cells [APCs]), CD11c (dendritic cell marker), lymphatic endothelium hyaluronan receptor-1 (LYVE1; expressed on lymphatic endothelium and macrophage subsets), chemokine receptor 7 (CCR7, a homing receptor for leukocytes), CXCL12 (expressed by activated leukocytes), CCR2 (a marker for inflammatory monocytes), and glial fibrillary acidic protein (GFAP; expressed by astrocytes) was analyzed and quantified., Results: In the episclera, a high number of cells (≥40 cells/mm2) were immunoreactive for CD68, CD45, MHCII, CCR7, LYVE1, and CD11b. Lower numbers (<20 cells/mm2) were positive for CXCL12, CCR2, and GFAP. The episclera showed a significantly higher number of cells compared to the stroma (P = 0.008). MHCII+ cells could be double positive for CCR7, CD45, CD11c, or CD11b and seldom CXCL12. Macrophages were most likely from the M1 type (CD68+, CD163-)., Conclusions: The healthy human sclera contains several macrophage populations, which can function as APCs, with the highest density being present in the episclera. Most cells express macrophage markers and may function as APCs. The presence of these cells might indicate that scleral immune cells are important for maintaining physiological functions in the eye and may potentially contribute to blood vessel homeostasis.

Allergic eye disease, as in most forms of atopy, ranges in severity among individuals from immediate hypersensitivity to a severe and debilitating chronic disease. Dendritic cells play a key role in stimulating pathogenic T cells in allergen re-exposure, or secondary responses. However, molecular cues by dendritic cells underpinning allergic T cell response levels and the impact that this control has on consequent severity of allergic disease are poorly understood. Here, we show that a deficiency in thrombospondin-1, a matricellular protein known to affect immune function, has subsequent effects on downstream T cell responses during allergy, as revealed in an established mouse model of allergic eye disease. More specifically, we demonstrate that a thrombospondin-1 deficiency specific to dendritic cells leads to heightened secondary T cell responses and consequent clinical disease. Interestingly, whereas thrombospondin-1-deficient dendritic cells augmented activity of allergen-primed T cells, this increase was not recapitulated with naïve T cells in vitro. The role of dendritic cell-derived thrombospondin-1 in regulating secondary allergic T cell responses was confirmed in vivo, as local transfer of thrombospondin-1-sufficient dendritic cells to the ocular mucosa of thrombospondin-1 null hosts prevented the development of augmented secondary T cell responses and heightened allergic eye disease clinical responses. Finally, we demonstrate that topical instillation of thrombospondin-1-derived peptide reduces T cell activity and clinical progression of allergic eye disease. Taken together, this study reveals an important modulatory role of dendritic cell-derived thrombospondin-1 on secondary allergic T cell responses and suggests the possible dysregulation of dendritic cell-derived thrombospondin-1 expression as a factor in allergic eye disease severity., (© Society for Leukocyte Biology.)

The sclera is a dense connective tissue that covers and protects the eye. It mainly consists of dense collagen bundles (types I, III, IV, V, VI, and VII). Due to its autofluorescence, opaqueness, and thickness, it has not been found suitable for confocal microscopy. An alternative approach to the one presented here, which uses formalin-fixed sclera embedded in paraffin for immunohistochemistry, has technical challenges, especially when preheating the tissue for antigen retrieval. Since the sclera is relatively poor in both cells and vessels, the use of larger tissue samples was explored to help prevent overlooking cells and to understand their localization in relation to vessels and other anatomical sites. To allow for the analysis of larger tissue samples under the confocal microscope, a laminating technique was performed to create thin layers from the sclera. Following the analysis of results of CD31 blood vessels and lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1) positive cells, for which approval for scientific examination was obtained, the advantages and limitations of this method are discussed.

Purpose: Conjunctival melanoma (CM) is an ocular surface tumor that can lead to fatal metastases. Patients developing, tumor-associated lymphangiogenesis have a significantly increased risk of metastatic disease, because tumor spread primarily occurs via lymphatic vessels to the draining lymph node. Here, we describe a novel immune-competent mouse model of CM that displays tumor-associated lymphangiogenesis with development of metastatic tumors., Methods: C57BL/6N mice received C57BL/6N-derived dermal melanoma cells (hepatocyte growth factor [HGF] cyclin dependent kinase-4 [Cdk4]+) or B16F10 via subconjunctival injection. A clinical score quantified primary tumor growth and metastases were identified by macroscopic examination of the draining lymph nodes, lung, and spleen. Confirmation of tumors and metastases was achieved by immunohistochemical staining for markers of pigmented cells (tyrosinase related protein-2 [TRP2]) and S-100, and of cell proliferation (Ki67). The intra- and peritumoral CD31+ blood and lymphatic vessel endothelium hyaluronan receptor-1 (LYVE-1)+ lymphatic vessels were quantified immunohistochemically., Results: All mice rapidly developed aggressive TRP2+, S100+, and Ki67+ CM. Metastatic tumors were found in the lymph node (9%) and lung (6%) of HGF-Cdk4(R24C)-treated mice and in the spleen (8%) and lung (17%) of B16F10-treated mice. The amount of peri- and intratumoral blood vessels was significantly increased compared with lymphatic vessels., Conclusions: This CM model in immune-competent animals offers new possibilities to study the pathobiology of tumor growth, invasion, and mechanisms of metastatic tumor spread, and provides a robust model to explore new immune-based and antilymphangiogenic treatment modalities of this malignancy.

Purpose: Malignant melanomas of the ocular surface (conjunctival melanoma [CM]) and within the eye (uveal melanoma [UM]) show different types of metastatic behavior. While CM has a propensity to spread first to regional lymph nodes, UM metastasizes almost exclusively via the hematogenic route to the liver. We investigated whether these different metastatic patterns might be attributable to differential hem- and lymphangiogenic characteristics of CM and UM cells., Methods: Human CM (CM2005.1, CRMM1, CRMM2) and UM (Mel270, Mel290, OM431) cell lines were analyzed for VEGF-A, -C, and -D expression by RT-PCR and ELISA. The influence of CM- or UM-conditioned medium on blood (BEC) and lymphatic (LEC) endothelial cell proliferation and migration was measured using 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyl-tetrazolium bromide (MTT) and scratch assays, respectively., Results: Vascular endothelial growth factor-A, -C and -D mRNA, and VEGF-A and -D protein were expressed by all CM and UM cell lines, while VEGF-C protein was only expressed by UM cell lines. The CM- and UM-conditioned medium did neither differentially affect BEC (P = 0.86) and LEC (P = 0.90) proliferation, nor BEC (P = 0.56) and LEC (P = 0.90) migration., Conclusions: Conjunctival melanoma cell lines did not show a higher prolymphangiogenic potential, and UM cell lines did not show a higher prohemangiogenic potential. Accordingly, other mechanisms within the tumor microenvironment might account for the diverging metastatic patterns of conjunctival versus uveal melanomas.

Purpose: Reports of lymphatics in the anterior human uvea are contradictory. This might be caused due to a certain topography, which has not been considered yet. Therefore, here we systematically analyze iris and adjacent ciliary body with immunohistochemistry by combining various lymphatic markers., Methods: Human iris and ciliary body were obtained from cornea donors and prepared for cryosectioning. Cross sections of tissue blocks at 12/3/6/9 o'clock position and at corresponding intersections (1:30/4:30/7:30/10:30) were processed for immunohistochemistry of LYVE-1, PDPN, PROX1, FOXC2, VEGFR3, and CCL21, and when necessary, these lymphatic markers were combined with CD31, α-smooth muscle-actin, CD68, and 4',6-diamidino-2 phenylindole dihydrochloride (DAPI). Double, triple, and quadruple marker combinations were documented using confocal microscopy., Results: Numerous podoplanin+ cells were mainly located at the anterior border of the iris while LYVE-1+ cells were distributed throughout the nonpigmented part. Both cell populations were PROX1/FOXC2/CCL21/VEGFR3-. Blood vessels, iris smooth muscles, and individual cells were VEGFR3+. While PDPN+ cells were rarely detected posteriorly of the iris root, many LYVE-1+ cells were present within the ciliary body muscle and villi. Within the muscle, occasionally PDPN+ vessel-like structures were detectable, but these were never colocalized with LYVE-1. Similar vessel-like structures were VEGFR3+/PROX1-/CCL21-, but CD31+. Further, ciliary muscle fibers and ciliary epithelium were immunoreactive for VEGFR3/CCL21, but were LYVE-1/PDPN-. A certain topography of structures at the various uvea-positions investigated was not obvious. The majority of LYVE-1+ cells displayed immunoreactivity for CD68., Conclusions: Lymphatic vessels colocalizing for at least two lymphatic markers were not detectable. Therefore, if present, putative lymphatic channels of the anterior uvea might display a different marker panel than generally presumed.

The lymphatic vasculature is - amongst other tasks - essentially involved in inflammation, (auto)immunity, graft rejection and cancer metastasis. The eye is mainly devoid of lymphatic vessels except for its adnexa, the conjunctiva and the limbus. However, several pathologic conditions can result in the secondary ingrowth of lymphatic vessels into physiologically alymphatic parts of the eye such as the cornea or the inner eye. Therefore, the cornea has served as an excellent in vivo model system to study lymphangiogenesis, and findings from such studies have substantially contributed to the understanding of central principles of lymphangiogenesis also with relevance outside the eye. Grafting experiments at the cornea have been extensively used to analyze the role of lymphangiogenesis in transplant immunology. In this regard, we recently demonstrated the crucial role of lymphatic vessels in mediating corneal allograft rejection and could show that antilymphangiogenic therapy increases graft survival. In the field of cancer research, we recently detected tumor-associated lymphangiogenesis in the most common malignant tumors of the eye, such as conjunctival carcinoma and melanoma, and ciliochoroidal melanoma with extraocular extension. These neolymphatics correlate with an increased risk of local recurrence, metastasis and tumor related death, and may offer potential therapeutic targets for the treatment of these tumors. This review will focus on corneal and tumor-associated ocular lymphangiogenesis. First, we will describe common experimentally used corneal lymphangiogenesis models and will recapitulate recent findings regarding the involvement of lymphatic vessels in corneal diseases and transplant immunology. The second part of this article will summarize findings about the participation of tumor-associated lymphangiogenesis in ocular malignancies and their implications for the development of future therapeutic strategies., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

There is currently considerable controversy about existence and classification of "lymphatic vessels" in the eye. Some of the confusion is certainly caused by inappropriate use (or nonuse) of the correct immunohistochemical markers. Many experts in the field expressed the need for a consensus statement, and, in this perspective, authors offer arguments and solutions to reliably continue with immunohistochemical ocular lymphatic research., (Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.)

During human ocular development, expression of proteins varies in different maturation stages. This study aims to characterize structures in human fetal eyes stained by the lymphatic marker podoplanin (D2-40) with emphasis on the stage of maturation and the presence of intraocular lymphatic structures. Formalin-fixed paraffin-embedded eyes from 40 human fetuses between 10 and 38 weeks of gestation (WoG) were investigated. Immunohistochemical stains were performed for D2-40, LYVE-1 as a secondary lymphatic marker, and CD34 as a control for endothelial reactivity. A semiquantitative analysis of antigen expression in different segments of the eye was performed by light microscopy. The intensity of antigen expression was graded with a score ranging from 0 to 3. Podoplanin expression was found with a variable intensity in 97.5% of the eyes, in particular in lymphatic vessels of the conjunctiva (n = 26), conjunctival and corneal epithelium (n = 33), corneal endothelium (n = 4), trabecular meshwork (n = 28), and optic nerve sheaths (n = 23). A slight, equivocal staining reaction was noted in the choroid (n = 14). There was a correlation of antigen reactivity and the gestational age for corneal endothelial reactivity in earlier gestational stages (p = 0.003) and trabecular meshwork in older eyes (p = 0.031). D2-40 positive Müller cells were detected in two eyes ≥32 WoG. Thus, aside from conjunctival lymphatic vessels, podoplanin was expressed in several structures of the human fetal eye and the ocular adnexae at different gestational stages. Podoplanin positive structures were also found in the choroid and the chamber angle. However, lymphatic vessels or its progenitors could not be unequivocally identified in intraocular structures during 10-38 weeks of gestation. There is no evidence from our data that transient intraocular lymphactics develop in the fetal eye between 10 and 38 weeks of gestation., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The adult sclera is free of lymphatic vessels, but contains a net of blood vessels. Whether and when this selectively lymphangiogenic privilege is achieved during embryologic development is not known yet. Therefore, we investigated the developing human sclera for blood- and lymphatic vessels in 34 abortions/stillborns (12-38 weeks of gestation). The probes were subdivided into three groups (group 1: 12-18 weeks of gestation, n = 10; group 2: 19-23 weeks of gestation, n = 13; group 3: 24-38 weeks of gestation, n = 11), and prepared for paraffin sections followed by immunohistochemistry against CD31 to detect blood vessels, and against lymphatic vessel endothelial hyaluronan receptor-1 (LYVE1)/podoplanin to detect lymphatic vessels. We could show, that in the human episclera distinct CD31 + blood vessels are present as early as week of gestation 13. Their amount increased during pregnancy, whereas stromal CD31 + blood vessels were elevated in early pregnancy and regressed with ongoing pregnancy. In the lamina fusca CD31 + blood vessels were absent at any time point investigated. Single LYVE1 + cells were identified primarily in the episclera; their amount decreased significantly with increasing gestational ages (group 1 compared to group 3: p < 0.01). However, LYVE1+/podoplanin + lymphatic vessels were not detectable in the sclera at any gestational ages analyzed. In contrast to the conjunctiva where LYVE1+/podoplanin + lymphatic vessels were detectable as early as week 17, the amount of LYVE1 + cells in the sclera was highest in early pregnancy (group 1), with a significant decrease during continuing pregnancy (p < 0.001). These findings are the first evidence for a fetal lymphangiogenic privilege of the sclera and show, that the fetal human sclera contains CD31 + blood vessels, but is primarily alymphatic. Our findings suggest a strong expression of selectively antilymphangiogenic factors, making the developing sclera a potential model to discern antilymphangiogenic mechanisms., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Purpose: To explore the function of natural killer (NK) cells in inflammatory angiogenesis in mice., Methods: To study ocular angiogenic responses we used the cornea BFGF micropellet and the laser-induced choroidal neovascularization (CNV) mouse models (C57BL/6). To deplete NK cells in these models, we injected an anti-NK1.1 antibody or an isotype antibody as a control. Corneas or choroids were immunohistochemically stained for blood vessels (CD31), macrophages (F4/80), or CNV (isolectin-IB4). Vascular endothelial growth factors (VEGF), IFN-γ, or TNF-α levels were measured by real-time quantitative PCR (qPCR) or flow cytometry. A coculture assay of macrophages, NK cells, and human umbilical vein endothelial cells (HUVECs) was analyzed morphometrically to examine the ability of NK cells to induce angiogenesis in vitro., Results: Our data demonstrate that in vivo depletion of NK cells leads to a significant reduction of corneal angiogenesis and CNV. Furthermore, NK cell depletion reduces macrophage infiltration into the cornea and mRNA expression levels of VEGF-A, VEGF-C, and VEGFR3 at day 7 after micropellet insertion. In the laser-induced CNV model, our data show that NK cell depletion leads to decreased areas of CNV and significantly reduced mRNA expression of VEGFs and IFN-γ in the choroid. An in vitro coculture assay shows an IFN-γ-dependent increase in VEGF expression levels, thereby increasing endothelial cell proliferation., Conclusions: Our findings demonstrate a novel pro-angiogenic function for NK cells, indicating that IFN-γ-secreting NK cells can induce angiogenesis by promoting enhanced VEGF expression by macrophages.

Purpose: Tumor-derived VEGF-A, apart from expediting sufficient vascularization, subsequent tumor growth, and metastatic spread, can act on malignant cells themselves provided that VEGF receptors 1 or 2 (VEGF-R1, -R2) are co-expressed. The study goal was to investigate whether such autocrine VEGF-A signaling exists in uveal melanoma (UM)., Methods: Primary (MEL-270, OM-431) and metastatic (OMM-2.3, OMM-2.5) UM cell lines were analyzed for VEGF-A, VEGF-R1, and VEGF-R2 expression by RT-PCR, ELISA (VEGF-A protein), and immunocytochemistry (VEGF receptors). Proliferation of UM cells incubated with neutralizing anti-VEGF-A antibody bevacizumab (≤ 2.5 mg/mL), or VEGF-A (≤ 100 ng/mL) was assessed by bromodeoxyuridine (BrdU) ELISA. It was measured by real-time PCR, whether VEGF-A (100 ng/mL) modulated the expression ratio of VEGF-A itself and its antiangiogenic antagonist pigment epithelium-derived factor (PEDF)., Results: All UM cells expressed VEGF-A, VEGF-R1, VEGF-R2 mRNA, and protein. In each cell line, the proliferation was stimulated by VEGF-A or inhibited by blocking VEGF-A, or both: bevacizumab significantly decreased the proliferation in MEL-270 (P = 0.005), OMM-2.3 (P = 0.001), and OMM-2.5 (P = 0.011). Increased VEGF-A signaling significantly raised the proliferation in MEL-270, OM-431 (P < 0.001, respectively), and OMM-2.3 (P = 0.043) in a dose-dependent manner but did not significantly change the VEGF-A/PEDF mRNA expression ratio., Conclusions: Autocrine VEGF-A signaling seems to be present in UM, sustaining the proliferation of both primary and metastatic UM cells. Apparently, VEGF-A signaling in UM cells neither acts retroactively on VEGF-A expression, in the sense of a feedback loop, nor contributes to a pro-angiogenic shift of the VEGF-A/PEDF ratio.

Purpose: To investigate whether the normal adult human sclera contains lymphatic vessels and to study their relation to immune cells and blood vessel anatomy., Methods: Scleral tissue probes from 35 adult human donor bulbi were analyzed by immunohistochemistry and confocal microscopy for blood vessels (CD31+), lymphatic vessels (lymphatic vessel endothelial hyaluronan receptor 1 [LYVE1]+, podoplanin+), and macrophages (CD68+) at 12 locations (anterior, equatorial, and posterior at 3, 6, 9, and 12 o'clock positions of the eye) in all three scleral layers (episclera, stroma, and lamina fusca). Approval for scientific examination was obtained., Results: CD31+ blood vessels were detectable in the human sclera, where the percentage area covered by CD31+ blood vessels was highest in the anterior episclera, followed by equatorial and posterior episclera, and was lowest in the scleral stroma (regardless of location). LYVE1+ podoplanin+ lymphatic vessels were not detectable in any location investigated, although there was a high number of LYVE1+ CD68+ macrophages. These macrophages were concentrated around blood vessels. In contrast, in the episclera, the number of detected LYVE1+ CD68+ macrophages was comparable in all locations; within the stroma, their number increased toward the posterior part of the eye., Conclusions: The adult sclera contains blood vessels but lacks, as revealed by immunohistochemistry and confocal microscopy, true lymphatic vessels. LYVE1+ CD68+ macrophages are located adjacent to the longitudinal axis of blood vessels. The function of these cells needs further investigation, but could be a next step toward a better understanding of pathological disorders such as inflammation, tumor, trauma, or glaucoma.

Lymphangiogenesis is a very early step in lymphatic metastasis. It is regulated and promoted not only by the tumor cells themselves, but also by cells of the tumor microenvironment, including cancer associated fibroblasts, mesenchymal stem cells, dendritic cells, or macrophages. Even the extracellular matrix as well as cytokines and growth factors are involved in the process of lymphangiogenesis and metastasis. The cellular and noncellular components influence each other and can be influenced by the tumor cells. The knowledge about mechanisms behind lymphangiogenesis in the tumor microenvironmental crosstalk is growing and offers starting points for new therapeutic approaches.

Purpose: Penetrating keratoplasty has a very poor outcome compared with adults if performed in the first years of life. Rejection in these young patients occurs even in the absence of known immunological risk factors. Recently, a baby rat model was introduced and an essential contribution of natural killer (NK) cells during allograft rejection was suggested. To analyze this, NK cells were depleted in baby rats before keratoplasty., Methods: Allogeneic keratoplasty was performed between Lewis and Fisher rats. The recipient's ages were 10 and 3 weeks, respectively. NK cells were depleted by an intraperitoneal injection of a monoclonal antibody. All experiments were controlled by the injection of isotypic control antibodies and syngeneically. Survival rates were calculated and cellular infiltrates were analyzed histologically., Results: NK cell depletion did delay median graft survival times in a statistically significantly way compared with the control animals (p<0.01). At median rejection time points, macrophages, CD4(+) T cells and CD25(+) leukocytes infiltrated to a greater extent in the depleted recipients. No significant changes in the cell numbers of infiltrating CD8(+) T cells were observed., Conclusions: We conclude that NK cells play a role during allograft rejection in baby rats, but their effect is replaceable. A greater infiltration of macrophages and CD4(+) T cells suggests that they might compensate for the missing NK cells' response in this experimental setting. Our results represent another step toward understanding the complex mechanisms of an accelerated corneal graft rejection in infant recipients.