Allogeneic limbo-deep anterior lamellar keratoplasty (Limbo-DALK)-A novel surgical technique in corneal stromal disease and limbal stem cell deficiency.

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.

Combined Osteopontin Blockade and Type 2 Classical Dendritic Cell Vaccination as Effective Synergetic Therapy for Conjunctival Melanoma.

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.

P49-A103†Allogeneic limbo-DALK: a novel surgical technique for patients with corneal stromal disease and limbal stem cell deficiency.

PURPOSE: To describe a novel corneal surgical technique combining Deep Anterior Lamellar Keratoplasty (DALK) with grafting of allogeneic limbal stem cells (limbo-DALK) as treatment for eyes with corneal stromal pathology and limbal stem cell deficiency (LSCD). METHODS: This is a series of six Limbo-DALKs in five eyes of five patients. One patient received a second limbo-DALK after graft failure following the first procedure. Two of the donor corneae were HLA matched. Clinical records of included patients were reviewed retrospectively. All patients had been diagnosed with LSCD due to various pathologies. Analysed data included demographic data, diagnoses and clinical history, graft visualization and thickness measurements by anterior segment OCT, visual acuity and epithelial status. Follow-up visits were 6 weeks and 3, 6, 9, 12 and 18 months postoperatively with final suture removal at 18 months and further follow-up examinations twice yearly thereafter. RESULTS: Two grafts showed total epithelial closure after 2 days, two after 14 days. In one eye, full closure of corneal epithelium did not occur after the first limbo-DALK, but could be achieved one month after second limbo-DALK. No endothelial graft rejection was seen. CONCLUSION: Based on data from this pilot series, limbo-DALK seems to be a novel viable surgical approach for eyes with severe LSCD and stromal corneal pathology.

Blood-Aqueous Barrier Disruption in Penetrating and Posterior Lamellar Keratoplasty: Implications for Clinical Outcome. / Blut-Kammerwasser-Schranken-Störungen bei perforierender und posteriorer lamellärer Keratoplastik: Implikationen für das klinische Ergebnis.

BACKGROUND: The blood-aqueous barrier (BAB) separates immunoprivileged tissue of the eye from the blood circulation. Disruption of the BAB is therefore a risk factor for rejection after keratoplasty. PURPOSE: The present work provides a review of the work of our group and others on BAB disruption in penetrating and posterior lamellar keratoplasty and its implications for clinical outcome. METHODS: A PubMed literature search was performed to generate a review paper. RESULTS: Laser flare photometry provides an objective and reproducible method to assess the integrity of the BAB. Studies of the flare after penetrating and posterior lamellar keratoplasty demonstrate a mostly regressive disruption of the BAB in the postoperative course, which is influenced in extent and duration by multiple factors. Persistently elevated flare values or an increase in flare after initial postoperative regeneration may indicate an increased risk of rejection. DISCUSSION: In case of persistent or recurrent elevated flare values after keratoplasty, intensified (local) immunosuppression may potentially be useful. This could become important in the future, especially for the monitoring of patients after high-risk keratoplasty. Whether an increase of the laser flare is a reliable early indicator of an impending immune reaction after penetrating or posterior lamellar keratoplasty has to be shown in prospective studies.

Corneal Hydrops - Aetiology and Advanced Therapeutic Strategies. / Der korneale Hydrops ­ Ursachen und moderne Therapieansätze.

Acute hydrops refers to sudden corneal edema caused by rupture of Descemet's membrane (DM) - often in progressive keratectasia. It leads to a sudden decrease in visual acuity, pain, and foreign body sensation as well as an increased glare sensation. Acute hydrops usually heals with scarring within months, but complications such as corneal perforation, infectious keratitis, and corneal vascularization may occur. The prevalence in keratoconus patients is 2.6 to 2.8%. Risk factors include keratoconjunctivitis vernalis, atopic dermatitis, high keratometry, male gender, and eye rubbing. Keratoplasty should be avoided in the acute phase. The prognosis of the graft is reduced, and after scar healing of the hydrops, wearing contact lenses or glasses may be possible again. Conservative therapy alone with lubricants and hyperosmolar eye drops, prophylactic antibiotic eye drops to prevent superinfection, and topical steroids was long considered the only possible form of treatment. However, healing under conservative therapy takes an average of over 100 days. In the meantime, there are different surgical strategies that rapidly shorten the healing and thus the recovery phase of the patients to a few days. If the DM is detached without tension, a simple injection of gas into the anterior chamber can already lead to reattachment and thus to almost immediate deswelling of the cornea. If the DM is under tension, predescemetal sutures combined with a gas injection into the anterior chamber can flatten the cornea and reattach the DM. Mini-Descemet membrane endothelial keratoplasty (mini-DMEK) allows for sutureless closure of the DM defect by transplantation of a small (< 5 mm) graft. In cases of particularly large DM tears and very pronounced hydrops, suture loosening and relapse may occur after the placement of predescemetal sutures. Mini-DMEK can then lead to permanent healing, but in contrast to simple corneal sutures, it is usually performed under general anesthesia and by aid of intraoperative optical coherence tomography. The very good results with regard to the rapid healing prove that surgical therapy makes sense in the vast majority of patients with acute hydrops and should be initiated quickly.

The novel role of lymphatic vessels in the pathogenesis of ocular diseases.

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.

[Surgical treatment options for congenital/infantile corneal opacities and anterior segment dysgenesis]. / Chirurgische Therapieoptionen bei kongenitalen/kindlichen Hornhauttrübungen und Vorderabschnittsdysgenesien.

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.

New Therapeutic Approaches for Conjunctival Melanoma-What We Know So Far and Where Therapy Is Potentially Heading: Focus on Lymphatic Vessels and Dendritic Cells.

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.

New Technologies in Clinical Trials in Corneal Diseases and Limbal Stem Cell Deficiency: Review from the European Vision Institute Special Interest Focus Group Meeting.

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.

Long-term outcome of descemet membrane endothelial keratoplasty (DMEK) following failed penetrating keratoplasty (PK).

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.

Detection of Pro- and Antiangiogenic Factors in the Human Sclera.

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.

Characterization of Antigen-Presenting Macrophages and Dendritic Cells in the Healthy Human Sclera.

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.

Using a Laminating Technique to Perform Confocal Microscopy of the Human Sclera.

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.

A Novel Model of Metastatic Conjunctival Melanoma in Immune-Competent Mice.

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.

Comparing the Hem- and Lymphangiogenic Profile of Conjunctival and Uveal Melanoma Cell Lines.

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.

Topography of Lymphatic Markers in Human Iris and Ciliary Body.

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.

Antilymphangiogenic therapy to promote transplant survival and to reduce cancer metastasis: what can we learn from the eye?

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.

Consensus statement on the immunohistochemical detection of ocular lymphatic vessels.

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.

Impact of the prolymphangiogenic crosstalk in the tumor microenvironment on lymphatic cancer metastasis.

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.