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

The transcription factor BMAL1 inhibits endothelial cell apoptosis by targeting STAT6 to repress its expression

Corneal transparency is critical for optimal visual function, and corneal neovascularization represents the primary cause of visual impairment globally. Recent studies have identified the transcription factor BMAL1 as a significant regulator of angiogenesis. However, its specific role and underlying mechanisms in endothelial cell apoptosis remain inadequately understood. This study seeks to elucidate the role and underlying mechanisms of BMAL1 in endothelial cell apoptosis by employing genetic modification, alkali-burned mouse corneal neovascularization models, lentiviral transfection, proteomic analysis, and other complementary methodologies. Our results showed that BMAL1 expression is significantly elevated in corneal neovascularization induced by alkali burn and removal of Bmal1 in endothelial cells resulted in the suppression of corneal neovascularization in alkali burn mouse models. In vivo experiments have demonstrated that the knockout of Bmal1 in endothelial cells leads to an increase in endothelial cell apoptosis. Complementary in vitro studies revealed that overexpression of BMAL1 in endothelial cells inhibits apoptosis, while knockdown of BMAL1 promotes apoptosis. Proteomic analysis identified STAT6 as a downstream target of BMAL1 involved in the regulation of endothelial cell apoptosis. Further cell salvage experiments confirmed that BMAL1 modulates endothelial cell apoptosis through the regulation of STAT6 expression. Finally, the results of dual-luciferase reporter assay demonstrated that BMAL1 exerts transcriptional repressive effects on the promoter bound by STAT6. This study elucidates the novel role and mechanism of BMAL1 in the regulation of angiogenesis and endothelial cell apoptosis, thereby identifying a potential therapeutic target for the treatment of vascular diseases such as corneal neovascularization.

Neutrophil extracellular traps-mediated upregulation of HIF-1α promotes corneal neovascularization

OBJECTIVES

The objective of this study is to examine the impact of neutrophil extracellular traps (NETs) on angiogenesis, both in vitro and in vivo contexts, as well as to elucidate the regulatory function of hypoxia-inducible factor (HIF-1α).

METHODS

The study focused on investigating the regulatory function of HIF-1α in the induction of NETs formation. In vivo, following NaOH stimulation, the formation of NETs was quantitatively assessed through immunofluorescence staining employing specific markers, namely SYTOX Green and PicoGreen. Furthermore, mice were administered with HIF-1α, and seven days post-alkali burn, the formation of NETs in the cornea was evaluated by immunofluorescence staining techniques. Protein immunoblotting analysis validated an increase inHIF-1α expression within human umbilical vein endothelial cells (HUVECs) that were induced to form by NETs. In vitro, human neutrophils were subjected to HIF-1α treatment. Subsequent to NaOH stimulation, the NETs mesh was isolated and co-cultured with HUVECs. The migratory capacity and angiogenic potential of HUVECs were then quantitatively evaluated.

RESULTS

Upon exposure to NaOH, a notable increase in SYTOX fluorescence was observed in neutrophils, indicative of the formation of a prominent network structure. Furthermore, a marked elevation in HIF-1α protein expression was detected in mouse corneal tissue that had undergone NETs formation, hinting at a potential role of NETs in mediating the up-regulation of HIF-1α. The outcomes of hematoxylin and eosin (H&E) staining, coupled with immunofluorescence staining, revealed an augmentation in neutrophils counts, with NETs exhibiting a marked potentiation of corneal neovascularization. In vitro assessments further demonstrated that HIF-1α played a stimulatory role in promoting the migration and tubular morphogenesis of HUVECs.

CONCLUSION

Exposure to sodium hydroxide serves as a trigger for the induction of NETs formation. NETs mediated an up-regulation of HIF-1α, which subsequently promotes angiogenesis and inflammatory activation in HUVECs. Consequently, this process leads to an enhancement of corneal neovascularization and inflammatory response.

Cohesin Complex Interacting with Promoters of MMP Genes for in Pterygium Occurrence

PURPOSE

Pterygium is a common ocular surface disease characterized by a high recurrence rate and unknown etiology.

METHODS

In this study, we investigated the upregulation of matrix metalloproteinase genes, including MMP1, MMP2, MMP3, MMP7, MMP9, MMP11, MMP12, MMP13, MMP23B, and MMP28, in pterygium tissue using RNA sequencing, Western blotting, and immunohistochemistry.

RESULTS

Employing the MEME tool, we identified a conserved DNA motif within the promoter regions of these matrix metalloproteinase genes. Mass spectrometry analysis revealed an interaction between the cohesin complex and this motif. Disrupting the cohesin complex through RNA interference of RAD21 cohesin complex component or structural maintenance of chromosomes 3 in primary pterygial fibroblasts led to decreased matrix metalloproteinase gene expression and reduced recruitment of twist family bHLH transcription factor 1 and transcription factor 4 to matrix metalloproteinase gene promoters.

CONCLUSION

Overall, our findings suggest a novel epigenetic mechanism regulating matrix metalloproteinase transcription in pterygium.

Characterization of T cells in the progression of dry eye disease using single-cell RNA sequencing in mice

BACKGROUND

Increasing evidence indicated that T cells have significant effects in dry eye disease (DED). However, the regulatory role of T cells in DED remains unclear.

METHODS

In this study, we examined immune responses throughout the progression in murine DED model. Using cytometry by time-of-flight (CyTOF) and single-cell RNA sequencing (scRNA-seq), we observed dynamic alterations in the proportions of immune cell landscape. Pseudotime trajectory and cell-cell communication analyses further illustrated T-cell differentiation and interaction networks.

RESULTS

CD4+ and CD8+ T cells exhibited an initial decline on Day 3 (D3) and followed by a recovery on Day 7 (D7). Single-cell transcriptomics provided insights into 15 distinct subsets of T cells with heterogeneous functional states. Pseudotime trajectory analysis demonstrated coordinated differentiation patterns of CD4+ and CD8+ T cells, indicating their collaborative involvement in the inflammatory process.

CONCLUSIONS

Our results clarify the dynamics of the adaptive immune response in DED and indicate that targeting T cells may serve as a promising immune-modulatory approach in the treatment of DED model.

Desiccation stress triggers and exacerbates experimental ocular Graft-versus-host-disease

INTRODUCTION

Chronic ocular graft-versus-host disease (oGVHD) is one of the most common complications after allogeneic hematopoietic stem cell transplantation (aHSCT). Recent studies indicate that desiccating stress by air-conditioning in transplantation wards increases the incidence of oGVHD. To test the hypothesis that experimental desiccating stress is a risk factor for oGVHD a mouse model of oGVHD was subjected to experimental desiccating stress.

MATERIALS/METHODS

A previously established chemo-induced minor-mismatch mouse model of oGVHD was used. One group was challenged with desiccating stress for 18 days and compared to non-desiccated GVHD animals. Clinical phenotyping was performed weekly and ocular tissue and regional lymph nodes were collected on days 7 and 28 for flow-cytometry, tear film cytokine analysis, histology for corneal lymphatics and dendritic cell counts, and corneal gene expression.

RESULTS

Desiccating stress leads to significant earlier and more severe systemic and oGVHD accompanied by higher numbers of activated corneal dendritic cells, higher expression of TNF in tear film and earlier corneal lymphangiogenesis. Gene expression analysis suggests that systemic GVHD severity may influence oGVHD. Different inflammatory pathways are upregulated at d28 following desiccating stress in contrast to non-desiccated GVHD.

CONCLUSIONS

The data presented strengthens the hypothesis, that desiccating stress during aHSCT is a risk factor for oGVHD. Together with already published clinical data, there is increasing evidence that implicates protecting patients from desiccation during the engraftment of allogeneic hematopoietic stem cells. Furthermore, specific prophylactic therapies should be developed and tested to reduce the incidence and severity of oGVHD.

Engineered Neutrophil Nanovesicles for Inhibiting Corneal Neovascularization by Synergistic Anti-Inflammatory, Anti-VEGF, and Chemoexcited Photodynamic Therapy

Corneal neovascularization (CorNV) develops under various pathological conditions and is one of the main causes of blindness. Due to that CorNV progression involves multiple steps, anti-vascular endothelial growth factor (VEGF) drugs alone could not sufficiently suppress this process, highlighting an urgent need for an efficient delivery system for the multi-step management of CorNV. In this study, a neutrophil nanovesicle-based eye drop (NCCR) is developed for CorNV therapy that simultaneously inhibits angiogenesis and inflammation, while eliminating pathological cells through chemoexcited photodynamic therapy (PDT). NCCR targets inflammatory lesions by leveraging the expression of chemokine receptors from the source cells. Then, NCCR exerts inhibitory effects on the sequential steps of neovascularization. First, it acts as a decoy and exerts an anti-inflammatory effect by neutralizing cytokines via its receptors on the surface of nanovesicles. Second, thioketals bond-linked ranibizumab is released in the high reactive oxygen species microenvironment of CorNV sites to bind VEGF, inhibiting vascular endothelial cell activation and proliferation. Finally, chemoexcited PDT eliminates preformed corneal blood vessels, disrupting tube formation and pericyte recruitment. The synergistic effects of NCCR on angiogenesis and inflammation, combined with the induction of apoptosis in neovessels via chemoexcited PDT, offer a novel and efficient strategy for CorNV treatment.

Neuropsin, TRPV4 and intracellular calcium mediate intrinsic photosensitivity in corneal epithelial cells

PURPOSE

To investigate intrinsic phototransduction in the corneal epithelium and its role in intracellular and inflammatory signaling.

METHODS

Optical imaging in isolated corneal epithelial cells (CECs) and debrided epithelia was combined with molecular, biochemical, pharmacological assays and gene deletion studies to track UVB-induced calcium signaling and release of cytokines, chemokines and matrix remodeling enzymes. Results from wild type mouse CECs were compared to data obtained from Opn5-/- and Trpv4-/- cells.

RESULTS

UVB stimuli and TRPV4 activity induced epithelial release of IL-1β, IL-17, matrix metalloproteinases MMP-3/MMP-9, and thymic stromal lymphopoietin (TSLP). UVB stimuli evoked [Ca2+]i elevations in dissociated mouse CECs that were partially reduced by inhibition of TRPV4 channels, Trpv4 knockdown and replacement of control saline with Ca2+-free saline. UVB-induced Ca2+ responses were significantly suppressed by OPN5 deletion and by inhibition of phospholipase C signaling, and responses were abrogated in cells with depleted intracellular Ca2+ stores.

CONCLUSIONS

Mammalian CECs are intrinsically and constitutively photosensitive. UVB photons are transduced by neuropsin, phospholipase C and CICR signaling, with mouse but not human CE transduction exhibiting a UVB-sensitive TRPV4 component. TRPV4 activity and UVB transduction are linked to cell-autonomous release of proinflammatory, matrix remodeling and nociceptive interleukins and MMPS. TRPV4-induced cytokine release may contribute to the pain induced by mechanical injury of the cornea and CEC photosensing may alert and protect the visual system from ultraviolet B (UVB) radiation -induced snow blindness, injury, vision loss and cancer.

Prox1 Protein in Corneal Limbal Lymphatic Vessels Maintains Limbal Stem Cell Stemness and Regulates Corneal Injury Repair

Purpose

The purpose of this study was to elucidate the role of the corneal lymphatic Prox1 gene in modulating limbal stem cell stemness and facilitating corneal injury repair.

Methods

The limbal Prox1 gene was knocked down by adeno-associated virus (AAV). The alkali burn model was induced in the naive group, the AAV-sham group, and the AAV-shProx1 group. Anterior segment photography, fluorescein sodium staining, and hematoxylin and eosin (H&E) staining were conducted immediately on days 1, 3, 7, 14, and 21 post-injury. Immunofluorescent (IF) staining was used to assess Ki67, ΔNp63, and K14. Additionally, seq-mRNA technology facilitated a comparative transcriptomic analysis between the AAV-sham and the AAV-shProx1 groups 7 days post-injury. Key regulated genes were verified by protein level. Furthermore, a co-culture model of lymphatic endothelial cells (LECs) and limbal stem cells (LSCs) was used to investigate the proliferation capacity and stemness expression of LSCs.

Results

Fluorescein sodium staining revealed that the epithelial defect area was significantly larger in the AAV-shProx1 group than in the AAV-sham group on days 1 and 3 post-injury (P < 0.05). Ki67, ΔNp63, and K14 expressions were consistently lower in the AAV-shProx1 group than in the AAV-sham group at distinct time points. Additionally, seq-mRNA results demonstrated that genes (Prox1 and Lyve1) were downregulated while inflammatory factors (Ccl2, Ccl7, IL16, IL1R, and TNFsf11) were upregulated in the AAV-shProx1 group compared with the AAV-sham group. When Prox1 was silenced in LECs, the proliferation and stemness of LSCs were markedly downregulated.

Conclusions

The Prox1 and Lyve1 proteins in lymphatic vessels served as pivotal regulated proteins in corneal injury repair. The draining role of lymphatic vessels during corneal injury was indispensable.

Advances in the Understanding of ocular and nasal lymphatics

Recent research advancements have enhanced our understanding of the lymphatic system in the eye and nasal region and its involvement in health and disease. The eye is an anatomical extension of the central nervous system and was previously believed to be devoid of lymphatic structures, except for the conjunctiva. However, Lymphatic vessels have been recently identified in the cornea (under pathological conditions), limbus, ciliary body, extraocular muscles, conjunctiva, lacrimal gland, optic nerve sheath, and lymphoid structures in the choroid and Schlemm's duct. These novel findings have significant implications in eye disease treatment; however, the mechanisms by which they preserve immune balance in the eye and eliminate metabolic waste and inflammatory cells remain nebulous. Furthermore, connections have been observed between ocular and nasal lymphatic vessels via the lymphatic network accompanying the nasolacrimal duct. The nasal lymphatic vessels are the primary pathway for cerebrospinal fluid drainage and a new route for drug delivery and treatment of brain-related diseases. This review provides an overview of recent advancements in understanding the structure and function of the ocular and nasal lymphatic systems and their association with cerebrospinal fluid drainage and various diseases.

Deep learning-based intratumoral and peritumoral features for differentiating ocular adnexal lymphoma and idiopathic orbital inflammation

OBJECTIVES

To evaluate the value of deep-learning-based intratumoral and peritumoral features for differentiating ocular adnexal lymphoma (OAL) and idiopathic orbital inflammation (IOI).

METHODS

Nighty-seven patients with histopathologically confirmed OAL (n = 43) and IOI (n = 54) were randomly divided into training (n = 79) and test (n = 18) groups. DL-based intratumoral and peritumoral features were extracted to characterize the differences in heterogeneity and tissue invasion between different lesions, respectively. Subsequently, an attention-based fusion model was employed to fuse the features extracted from intra- and peritumoral regions and multiple MR sequences. A comprehensive comparison was conducted among different methods for extracting intratumoral, peritumoral, and fused features. Area under the curve (AUC) was used to evaluate the performance under a 10-fold cross-validation and independent test. Chi-square and student's t-test were used to compare discrete and continuous variables, respectively.

RESULTS

Fused intra-peritumoral features achieved AUC values of 0.870-0.930 and 0.849-0.924 on individual MR sequences in the validation and test sets, respectively. This was significantly higher than those using intratumoral features (p < 0.05), but not significantly different than those using peritumoral features (p > 0.05). By combining multiple MR sequences, AUC values of the intra-peritumoral features were boosted to 0.943 and 0.940, higher than those obtained from each sequence alone. Moreover, intra-peritumoral features yielded higher AUC values compared to entire orbital cone features extracted by either the intra- or the peritumoral DL model, although no significant difference was found from the latter (p > 0.05).

CONCLUSION

DL-based intratumoral, peritumoral, and especially fused intra-peritumoral features may help differentiate between OAL and IOI.

KEY POINTS

Question What is the diagnostic value of the peritumoral region and its combination with the intratumoral region for radiomic analysis of orbital lymphoproliferative disorders? Findings Fused intra- and peritumoral features achieved significantly higher performance than intratumoral features, but had no significant difference to the peritumoral features. Clinical relevance Peritumoral contextual features, which characterize the invasion patterns of orbital lesions within the surrounding areas of the entire orbital cone, might serve as an independent imaging marker for differentiating between OAL and IOI.

Targeting glycolytic reprogramming by tsRNA-0032 for treating pathological lymphangiogenesis

Lymphangiogenesis is vital for tissue fluid homeostasis, immune function, and lipid absorption. Abnormal lymphangiogenesis has been implicated in several diseases such as cancers, inflammatory, and autoimmune diseases. In this study, we elucidate the role of tsRNA-0032 in lymphangiogenesis and its molecular mechanism. tsRNA-0032 expression is significantly decreased in corneal suture model and human lymphatic endothelial cell (HLEC) model under inflammatory condition. Overexpression of tsRNA-0032 exerts anti-lymphangiogenic effects by inhibiting HLEC proliferation, migration, and tube formation. Moreover, overexpression of tsRNA-0032 inhibits suture-induced corneal lymphangiogenesis. tsRNA-0032 is mainly located in the cytoplasm and interacts with Ago2 protein. Overexpression of tsRNA-0032 reduces ATP production and decreases pyruvate and lactate levels by targeting PKM2, a key enzyme in glycolysis. This regulation of glycolysis alters cellular energy and metabolic balance in HLECs, contributing to anti-lymphangiogenic effects. Clinical data reveals that tsRNA-0032 levels are significantly reduced in corneal tissues of transplant recipients compared to donors, while PKM2 expression is elevated, highlighting the clinical relevance of tsRNA-0032/PKM2 axis in corneal lymphangiogenesis. This study offers new insights into the regulation of lymphangiogenesis and presents potential therapeutic targets for lymphangiogenesis-related diseases.

Harnessing Tumor Cell-Derived Exosomes for Immune Rejection Management in Corneal Transplantation

Transplantation remains the definitive treatment for end-stage organ failures, but its efficacy is frequently compromised by immune rejection. This study introduces a novel strategy by utilizing tumor-derived exosomes from B16-F10 melanoma cells (B16-Exo), diverging from the conventional use of immune cell-derived exosomes, to alleviate post-transplantation immune rejection. Utilizing murine corneal transplantation as a model, it is demonstrated that B16-Exo significantly reduces immune rejection, evidenced by decreased corneal opacity, neovascularization, and immune dysregulation, while enhancing postoperative survival. Proteomic analyses reveal differential expression of pivotal proteins in B16-Exo, notably the JAK2 protein within the JAK-STAT signaling pathway, which has been mechanistically demonstrated to amplify the activity of myeloid-derived suppressor cells (MDSCs) and inhibit T cell proliferation. These findings demonstrate the significant immunomodulatory effect of B16-Exo in transplant immunology, supporting the continued exploration of tumor-derived exosomes as a platform to uncover novel immunosuppressive mechanisms in transplantation.

Evaluation of the clinical efficacy of modified LSC transplantation plus BCL implantation in the treatment of pterygium

OBJECTIVE

To explore the clinical efficacy of modified limbal stem cell transplantation(Modified LSC transplantation) and bandage contact lens(BCL) implantation in pterygium surgery.

METHODS

A total of 479 patients with primary pterygium who were admitted to our hospital from March 2019 to March 2023 were randomly divided into three groups: the normal group (Group A: 89 patients), the control group (Group B: 195 patients), and the modified group (Group C: 195 patients). Each group received different intervention measures. Group A did not undergo surgical treatment and were required to follow up as outpatients. Group B received LSC transplantation combined with interrupted suturing plus BCL, whereas Group C received modified LSC transplantation combined with BCL. The degree of corneal irritation symptoms, wound healing and graft status under slit lamp, incidence and recurrence rate of complications, tear film rupture time, tear secretion test, intraocular pressure, ocular surface inflammation response(IL-1β, PGE2, TNF-α, VEGF), and visual quality were compared and analyzed at various time points after surgery.

RESULTS

Compared with those in the Group B, patients in the Group C experienced faster normalization of corneal epithelium recovery, fewer corneal irritation symptoms, and better wound healing. The break-up time (BUT) of the tear film at 1 week to 1 year postoperatively was significantly greater in the Group C than Group B, with values approaching those of Group A by 3 months (P < 0.05). The Schirmer test results revealed a similar trend to that of the BUT. Further analysis of intraocular pressure (IOP) at different time points revealed no significant differences among the three groups at postoperative Day 1. However, due to the use of corticosteroid eye drops postoperatively, IOP was greater in both the Group B(17.24 ± 2.12 mmHg) and Group C (17.02 ± 2.37 mmHg) than Group A (13.92 ± 1.57 mmHg) at 1 week. By 1 month, Group C had a lower IOP (15.77 ± 1.63 mmHg) than Group B(17.78 ± 2.41 mmHg). There were no significant differences in IOP among the three groups from 3 months to 1 year (P > 0.05). The ELISA results indicated that the expression levels of the ocular surface inflammatory factors IL-1β, TNF-α, PEG2, and VEGF in the Group C were lower than those in Group B from 1 week to 1 year post surgery. Under both natural light and low-light conditions (spatial frequency/6 cd), Group C had better best-corrected visual acuity and contrast sensitivity than Group B at 1 week to 1 year postoperatively. Additionally, Group C had lower corneal higher-order aberrations (including astigmatism, spherical aberrations, and total higher-order aberrations) and superior vision-related quality of life scores at 1 year postoperatively than Group B, with statistically significant differences (P < 0.05).

CONCLUSION

Modified LSC transplantation combined with BCL implantation provided superior treatment outcomes for patients with pterygium, which was worthy of further clinical promotion.

Efficacy and safety of combined UV-light corneal crosslinking and fine-needle diathermy to regress pathological murine corneal (lymph)angiogenesis in vivo

PURPOSE

To compare safety and efficacy of isolated and combined UV-light corneal crosslinking (CXL) and fine-needle diathermy (FND) to regress pathological corneal vessels in vivo.

METHODS

Mice with inflamed and pathologically vascularized corneas received CXL or FND as monotherapy or a combination of both treatments. Corneal pathological blood and lymphatic vessels, immune cells and the morphology of anterior segment structures were evaluated.

RESULTS

All three approaches were able to regress blood and lymphatic vessels in mice. A comparative analysis of the three methods revealed that the FND monotherapy and the CXL + FND combination were significantly more effective than the CXL monotherapy, one and 2 weeks after therapy and especially in regressing lymphatic vessels. Furthermore, the combination therapy induced significantly less immune cell recruitment compared to the monotherapies. All three methods were safe to use in regards of corneal integrity.

CONCLUSIONS

A combination of FND and CXL led to regression of pathological corneal lymphatic and blood vessels and reduced the infiltration of immune cells into inflamed murine corneas. This approach offers a new effective, safe and clinically usable strategy to treat eyes with mature pathological blood vessels and even more so for lymphatic vessels, for example prior to high-risk corneal transplantation.

[Pathogenesis of Fuchs endothelial corneal dystrophy, the fibrillar layer and individualized treatment]

Fuchs endothelial corneal dystrophy (FECD) is a genetic and age-associated corneal disease characterized by an accelerated loss of corneal endothelial cells and an increased subendothelial deposition of extracellular matrix (ECM). Clinically, advanced disease leads to corneal edema with subsequent reduction in visual acuity. In the majority of patients with advanced FECD, a fibrillar layer (FL) appears on the posterior corneal surface. This FL is mostly localized in the inferotemporal corneal quadrant, marks areas with significantly reduced endothelial cell density and increased corneal thickness in the sense of edema and can be visualized and measured using Scheimpflug backscatter analysis due to increased backscatter. FECD is currently the most common indication for corneal transplantation worldwide, usually in the form of Descemet membrane endothelial keratoplasty (DMEK). New treatment approaches include variations of DMEK surgery such as hemi- or quarter DMEK with individualized and smaller grafts or Descemet membrane stripping only (DSO). In the future, clinical imaging of the FL as a particularly affected endothelial area could be important for FECD progression assessment and planning of surgical interventions. This article provides an overview of the current state of research on the clinical aspects, pathogenesis, fibrillar layer and individualized treatment of FECD.

Lymphatic-specific methyltransferase-like 3-mediated m6A modification drives vascular patterning through prostaglandin metabolism reprogramming

Lymphangiogenesis plays a pivotal role in the pathogenesis of various vascular disorders, including ocular vascular diseases and cancers. Deregulation of N 6-methyladenosine (m6A) modification has been identified as a key contributor to human diseases. However, the specific involvement of m6A modification in lymphatic remodeling remains poorly understood. In this study, we demonstrate that inflammatory stimulation and corneal sutures induce elevated levels of methyltransferase-like 3 (METTL3)-mediated m6A modification. METTL3 knockdown inhibits lymphatic endothelial viability, proliferation, migration, and tube formation in vitro. METTL3 knockdown attenuates corneal sutures-induced lymphangiogenesis and intratumoral lymphangiogenesis initiated by subcutaneous grafts, consequently restraining corneal neovascularization, tumor growth, and tumor neovascularization in vivo. Mechanistically, METTL3 knockdown upregulates prostaglandin-endoperoxide synthase 2 expression through an m6A-YTHDF2-dependent pathway, enhancing the synthesis of cyclopentenone prostaglandins (CyPGs). Aberrant CyPG production in lymphatic endothelial cells impairs mitochondrial oxidative phosphorylation, contributing to pathological lymphangiogenesis. Moreover, selective inhibition of METTL3 with STM2457 reduces m6A levels in lymphatic endothelial cells, effectively suppressing pathological lymphangiogenesis. This study provides compelling evidence that lymphatic-specific METTL3 plays a critical role in vascular patterning through prostaglandin metabolism reprogramming. Thus, METTL3 emerges as a promising target for treating lymphangiogenesis-related diseases.

Lymphangiogenesis: novel strategies to promote cutaneous wound healing

The cutaneous lymphatic system regulates tissue inflammation, fluid balance and immunological responses. Lymphangiogenesis or lymphatic dysfunction may lead to lymphedema, immune deficiency, chronic inflammation etc. Tissue regeneration and healing depend on angiogenesis and lymphangiogenesis during wound healing. Tissue oedema and chronic inflammation can slow wound healing due to impaired lymphangiogenesis or lymphatic dysfunction. For example, impaired lymphangiogenesis or lymphatic dysfunction has been detected in nonhealing wounds such as diabetic ulcers, venous ulcers and bedsores. This review summarizes the structure and function of the cutaneous lymphatic vessel system and lymphangiogenesis in wounds. Furthermore, we review wound lymphangiogenesis processes and remodelling, especially the influence of the inflammatory phase. Finally, we outline how to control lymphangiogenesis to promote wound healing, assess the possibility of targeting lymphangiogenesis as a novel treatment strategy for chronic wounds and provide an analysis of the possible problems that need to be addressed.

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

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

Therapeutic intervention in neuroinflammation for neovascular ocular diseases through targeting the cGAS-STING-necroptosis pathway

The microglia-mediated neuroinflammation have been shown to play a crucial role in the ocular pathological angiogenesis process, but specific immunotherapies for neovascular ocular diseases are still lacking. This study proposed that targeting GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) might be a novel immunotherapy for these angiogenesis diseases. We found a significant upregulation of CGAS and STING genes in the RNA-seq data derived from retinal tissues of the patients with proliferative diabetic retinopathy. In experimental models of ocular angiogenesis including laser-induced choroidal neovascularization (CNV) and oxygen-induced retinopathy (OIR), the cGAS-STING pathway was activated as angiogenesis progressed. Either genetic deletion or pharmacological inhibition of STING resulted in a remarkable suppression of neovascularization in both models. Furthermore, cGAS-STING signaling was specifically activated in myeloid cells, triggering the subsequent RIP1-RIP3-MLKL pathway activation and leading to necroptosis-mediated inflammation. Notably, targeted inhibition of the cGAS-STING pathway with C-176 or SN-011 could significantly suppress pathological angiogenesis in CNV and OIR. Additionally, the combination of C-176 or SN-011 with anti-VEGF therapy led to least angiogenesis, markedly enhancing the anti-angiogenic effectiveness. Together, our findings provide compelling evidence for the importance of the cGAS-STING-necroptosis axis in pathological angiogenesis, highlighting its potential as a promising immunotherapeutic target for treating neovascular ocular diseases.

Alkali injury-induced pathological lymphangiogenesis in the iris facilitates the infiltration of T cells and ocular inflammation

Inflammatory lymphangiogenesis is intimately linked to immune regulation and tissue homeostasis. However, current evidence has suggested that classic lymphatic vessels are physiologically absent in intraocular structures. Here, we show that neolymphatic vessels were induced in the iris after corneal alkali injury (CAI) in a VEGFR3-dependent manner. Cre-loxP-based lineage tracing revealed that these lymphatic endothelial cells (LECs) originate from existing Prox1+ lymphatic vessels. Notably, the ablation of iridial lymphangiogenesis via conditional deletion of VEGFR3 alleviated the ocular inflammatory response and pathological T cell infiltration. Our findings demonstrate that iridial neolymphatics actively participate in pathological immune responses following injury and suggest intraocular lymphangiogenesis as a valuable therapeutic target for the treatment of ocular inflammation.

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

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.

The role of lymphatic vessels in corneal fluid homeostasis and wound healing

The cornea, essential for vision, is normally avascular, transparent, and immune-privileged. However, injuries or infections can break this privilege, allowing blood and lymphatic vessels to invade, potentially impairing vision and causing immune responses. This review explores the complex role of corneal lymphangiogenesis in health and diseases. Traditionally, the cornea was considered devoid of lymphatic vessels, a phenomenon known as "corneal (lymph)angiogenic privilege." Recent advances in molecular markers have enabled the discovery of lymphatic vessels in the cornea under certain conditions. Several molecules contribute to preserving both immune and lymphangiogenic privileges. Lymphangiogenesis, primarily driven by VEGF family members, can occur directly or indirectly through macrophage recruitment. Corneal injuries and diseases disrupt these privileges, reducing graft survival rates following transplantation. However, modulation of lymphangiogenesis offers potential interventions to promote graft survival and expedite corneal edema resolution.This review underscores the intricate interplay between lymphatic vessels, immune privilege, and corneal pathologies, highlighting innovative therapeutic possibilities. Future investigations should explore the modulation of lymphangiogenesis to enhance corneal health and transparency, as well as corneal graft survival, and this benefits patients with various corneal conditions.

Current Advances in Corneal Stromal Stem Cell Biology and Therapeutic Applications

Corneal stromal stem cells (CSSCs) are of particular interest in regenerative ophthalmology, offering a new therapeutic target for corneal injuries and diseases. This review provides a comprehensive examination of CSSCs, exploring their anatomy, functions, and role in maintaining corneal integrity. Molecular markers, wound healing mechanisms, and potential therapeutic applications are discussed. Global corneal blindness, especially in more resource-limited regions, underscores the need for innovative solutions. Challenges posed by corneal defects, emphasizing the urgent need for advanced therapeutic interventions, are discussed. The review places a spotlight on exosome therapy as a potential therapy. CSSC-derived exosomes exhibit significant potential for modulating inflammation, promoting tissue repair, and addressing corneal transparency. Additionally, the rejuvenation potential of CSSCs through epigenetic reprogramming adds to the evolving regenerative landscape. The imperative for clinical trials and human studies to seamlessly integrate these strategies into practice is emphasized. This points towards a future where CSSC-based therapies, particularly leveraging exosomes, play a central role in diversifying ophthalmic regenerative medicine.

Ontogenesis of the Mouse Ocular Surface Lymphatic Vascular Network

Purpose

Ocular lymphatic vessels play major physiological role in eye homeostasis and their dysfunction can contribute to the progression of several eye diseases. In this study, we characterized their spatiotemporal development and the cellular mechanisms occurring during their ontogenesis in the mouse eye.

Methods

Whole mount immunofluorescent staining and imaging by standard or lightsheet fluorescence microscopy were performed on late embryonic and early postnatal eye mouse samples.

Results

We observed that the ocular surface lymphatic vascular network develops at the early postnatal stages (between P0 and P5) from two nascent trunks arising at the nasal side on both sides of the nictitating membrane. These nascent vessels further branch and encircle the whole eye surface by sprouting lymphangiogenesis. In addition, we got evidence for the existence of a transient lymphvasculogenesis process generating lymphatic vessel fragments that will mostly formed the corneolimbal lymphatic vasculature which further connect to the conjunctival lymphatic network. Our results also support that CD206-positive macrophages can transdifferentiate and then integrate into the lymphatic neovessels.

Conclusions

Several complementary cellular processes participate in the development of the lymphatic ocular surface vasculature. This knowledge paves the way for the design of new therapeutic strategies to interfere with ocular lymphatic vessel formation when needed.

Detailed protocol for a corneal thermal cauterization-based (lymph-)angiogenesis assay in mice

Angiogenesis and lymphangiogenesis, the formation of new blood or lymphatic vessels, respectively, from preexisting vasculature is essential during embryonic development, but also occurs during tissue repair and in pathological conditions (cancer; ocular disease; ischemic, infectious and inflammatory disorders), which are all characterized to a certain extent by inflammatory conditions. Hence, a rapid, inexpensive, feasible / technically easy, reliable assay of inflammation-induced (lymph-)angiogenesis is highly valuable. In this context, the corneal thermal cauterization assay in mice is a simple, low-cost, reproducible, insightful and labor-saving assay to gauge the role of inflammation in angiogenesis and lymphangiogenesis. However, to the best of our knowledge, there is no standardized protocol to perform this assay. Here, we provide a step-by-step description of the model's procedures, which include:•The thermal cauterization of the corneas,•Enucleation and dissection of the corneas,•Subsequent immunofluorescence staining of the neovasculature, and morphometric analysis. We also discuss ethical considerations and aspects related to animal welfare guidelines. Altogether, this paper will help to increase the reproducibility of the corneal thermal cauterization model and facilitate its use for angiogenesis and lymphangiogenesis research.