Corneal Endothelial Cell Migration and Proliferation Enhanced by Rho Kinase (ROCK) Inhibitors in In Vitro and In Vivo Models

Preclinical Models for Studying Fuchs Endothelial Corneal Dystrophy

Fuchs Endothelial Corneal Dystrophy (FECD) is a corneal endothelial disease that causes microenvironment alterations and endothelial cell loss, which leads to vision impairment. It has a high global prevalence, especially in elderly populations. FECD is also one of the leading indications of corneal transplantation globally. Currently, there is no clearly defined canonical pathway for this disease, and it has been proposed that the combinatorial effects of genetic mutations and exogenous factors cause FECD. Clinical studies and observations have provided valuable knowledge and understanding of FECD, while preclinical studies are essential for gaining insights into disease progression and mechanisms for the development and testing of regenerative medicine therapies. In this review, we first introduce the proposed genetic and molecular pathologies of FECD. Notably, we discuss the impact of abnormal extracellular matrix deposition (guttata), endothelial-to-mesenchymal transition, cell senescence, and oxidative stress on the pathology and etiology of FECD. We review and summarize the in vitro cell models, ex vivo tissues, and in vivo animal models used to study FECD. The benefits and challenges of each model are also discussed.

Concurrent Descemet Stripping Only With Excision of Iris Pigment Epithelial Cysts

PURPOSE

To describe a case of bilateral large iris pigment epithelial (IPE) cysts causing corneal endothelial dysfunction that was successfully managed with a surgical cyst excision combined with Descemet stripping only (DSO) procedure followed by postoperative rho kinase inhibitor (ROCK-I) administration.

METHODS

Case report.

RESULTS

A 27-year-old woman presented with bilateral large IPE cysts adhering to the corneal endothelium, causing endothelial dysfunction with overlying corneal edema. Ultrasound biomicroscopy of both eyes revealed multiple thick-walled cysts, with points of adhesion to the pupillary margin, occupying the central part of the anterior chamber and adhering anteriorly to the corneal endothelium. Baseline pachymetry measurements were 631 μm in the right eye and 980 μm in the left. Following surgical excision, cystic lesions are removed from the posterior aspect of the cornea, in a similar fashion to the DSO technique. Pathology confirmed the presence of iris epithelium and Descemet membrane without evidence of malignancy. Topical netarsudil 0.02% was administered postoperatively, resulting in significant improvement in vision, complete resolution of corneal edema, reduction in corneal pachymetry, and a significant increase in central endothelial cell count at 6 months postoperatively, without recurrence of cysts.

CONCLUSIONS

DSO combined with cyst excision, followed by topical ROCK-I administration, is a viable approach for the management of corneal decompensation associated with IPE cysts that are adherent to the endothelium. We herein demonstrate complete clearance of corneal edema and excellent visual outcomes without cyst recurrence, potentially avoiding the need for endothelial keratoplasty.

Establishment of an Ex Vivo Human Corneal Endothelium Wound Model

Purpose

A human model able to simulate the manifestation of corneal endothelium decompensation could be advantageous for wound healing and future cell therapy assessment. The study aimed to establish an ex vivo human cornea endothelium wound model where endothelium function can be evaluated by measuring corneal thickness changes.

Methods

The human cornea was maintained in an artificial anterior chamber, with a continuous culture medium infusion system designed to sustain corneal endothelium and epithelium simultaneously. The corneal thickness was used to assess corneal endothelial cell function. Immunostaining was used to evaluate cell viability and endothelial cell marker expression, ZO-1 and Na/K ATPase.

Results

Human corneas with intact corneal endothelium were maintained in the ex vivo model for 28 days, showing normal corneal thickness with a clear and transparent appearance. Corneal endothelial cells were alive and expressed ZO-1 and Na/K ATPase at the end of the organ culture. The endothelium wounded corneas showed persistent corneal edema with an increase in corneal thickness at 654.6 ± 31.7 µm. Staining results showed that no cells migrated to cover the wound and no expression of ZO-1 and Na/K ATPase on the posterior surface of the cornea was found.

Conclusions

This study provided a novel method to establish an ex vivo human cornea organ culture model, where corneal endothelium function can be evaluated by accessing the corneal thickness.

Translational Relevance

The ex vivo model established in this study can provide an alternative to the animal model in studying corneal endothelium decompensation.

Ocular effects of Rho kinase (ROCK) inhibition: a systematic review

Topical therapies targeting Rho-associated protein kinase (ROCK) signalling, including netarsudil (Rhopressa®) and ripasudil (Glanatec®), have become widely adopted as part of standard clinical practice to lower intraocular pressure (IOP) in patients with ocular hypertension or glaucoma. Given the pleiotropic roles of ROCK signalling, ROCK inhibition has the potential to cause unintended ocular side effects beyond IOP lowering in other substructures of the eye, both beneficial and deleterious. Additional experience and observation of patients treated with this class of medications have uncovered both new side effects not reported in the initial clinical trials, as well as potential benefits that have inspired off-label uses and that have been the topic of numerous clinical studies, case series, case reports, and translational studies. Here, we performed a comprehensive systematic review and identified 170 studies describing ocular effects of ROCK inhibition. In addition to describing well-established ocular effects associated with inhibition of ROCK signalling, such as conjunctival hyperaemia, corneal verticillata, and reticular corneal epithelial oedema, we also highlight other effects, such as corneal haemorrhages, changes in corneal contour, anterior subcapsular opacities, contact dermatitis, punctal stenosis, and eyelid wound dehiscence, which have been described in case series and case reports. Finally, we evaluated studies describing potential novel applications of ROCK inhibition for treating disorders affecting the cornea, the retina, and the optic nerve, finding strong evidence in support of a beneficial effect of ROCK inhibitors on corneal oedema due to corneal endothelial cell dysfunction. The other potential applications require further research.

Outcomes of Descemet Stripping Only Without Postoperative Use of Topical Rho-Associated Protein Kinase Inhibitors

PURPOSE

Descemet stripping only (DSO) is a promising surgical option for select patients with Fuchs endothelial dystrophy (FED). There is growing support for the use of topical Rho-associated protein kinase inhibitors (ROCKi) to optimize DSO outcomes. However, in many settings, ROCKi are either unavailable or not approved to treat corneal diseases. This study sought to characterize patient outcomes after DSO in the absence of ROCKi and potentially broaden the settings where DSO can be offered to patients.

METHODS

Single-center retrospective case series of 15 eyes/11 patients (66 years; 52-74) that underwent DSO, alone or combined with cataract surgery, by one surgeon between August 2020 and January 2023. Patients included in analyses had FED with central guttae, no clinical evidence of corneal edema, and a clinically healthy peripheral corneal endothelium.

RESULTS

Mean follow-up time was 14 months (2-34). Fourteen of 15 eyes achieved corneal clearance (93.3%). Mean time to clearance was 8.5 weeks (3-23). Eleven eyes (73%) achieved corrected distance visual acuity of ≤0.2 with a significant postoperative improvement at 4 to 8 months ( P < 0.05) and sustained improvements at >12 months. No significant astigmatism was introduced by the procedure. Two eyes developed cystoid macular edema postoperatively. A trend toward earlier clearance was observed in the <65 years old group.

CONCLUSIONS

Despite a longer time to corneal clearance in this cohort compared with the few studies using ROCKi, the overall success rate and visual outcomes for the patients in our cohort supports the use of DSO in settings where ROCKi are not readily available.

Exploring the Role of ROCK Inhibition in Corneal Edema Through Crosstalk Between Epithelial and Endothelial Cells

The maintenance of corneal transparency and normal vision is dependent on preservation of epithelial and endothelial cell layer homeostases. Different types of corneal injury can induce swelling and losses in transparency. Fuchs endothelial corneal dystrophy (FECD) is one type of injury that is commonly treated with rho-associated coiled-coil-containing protein kinase (ROCK) inhibitors. While their clinical benefit is apparent, certain aspects of their mechanism of action require clarification. Specifically, although topical eye drops containing ROCK inhibitors have been employed to treat corneal endothelial dysfunction-associated corneal edema, it remains unclear whether interactions between both corneal epithelial and endothelial cell contribute to mitigating clinical signs that compromise normal vision. To address this question, we first review the intricate ROCK signaling pathways and their role in modulating a variety of functions that are related to the maintenance of corneal transparency and normal vision. We also review the results of ongoing clinical trials employing current FDA-approved ROCK inhibitors, highlighting the prominent role of Y-27632 in the treatment of a variety of ocular conditions, particularly FECD, and its promising results in reversing losses in normal vision through facilitating cell proliferation and suppressing apoptosis. This review shows that the ROCK inhibitor clinical benefit is affected by their interactions between the epithelium and the endothelium. This realization makes it likely that ROCK inhibitors will be approved for use in a clinical setting to treat FECD.

Hepatocyte Growth Factor Modulates Corneal Endothelial Wound Healing In Vitro

In this study, we assessed the impact of hepatocyte growth factor (HGF) on corneal endothelial cells (CECs), finding that HGF concentrations of 100-250 ng/mL significantly increased CEC proliferation by 30%, migration by 32% and improved survival under oxidative stress by 28% compared to untreated controls (p < 0.05). The primary objective was to identify non-fibrotic pharmacological strategies to enhance corneal endothelial regeneration, addressing a critical need in conditions like Fuchs' endothelial dystrophy (FED), where donor tissue is scarce. To confirm the endothelial nature of the cultured CECs, Na+/K+-ATPase immunohistochemistry was performed. Proliferation rates were determined through BrdU incorporation assays, while cell migration was assessed via scratch assays. Cell viability was evaluated under normal and oxidative stress conditions using WST-1 assays. To ensure that HGF treatment did not trigger epithelial-mesenchymal transition, which could lead to undesirable fibrotic changes, α-SMA staining was conducted. These comprehensive methodologies provided robust data on the effects of HGF, confirming its potential as a therapeutic agent for corneal endothelial repair without inducing harmful EMT, as indicated by the absence of α-SMA expression. These findings suggest that HGF holds therapeutic promise for enhancing corneal endothelial repair, warranting further investigation in in vivo models to confirm its clinical applicability.

Neuropeptide alpha-Melanocyte stimulating hormone preserves corneal endothelial morphology in a murine model of Fuchs dystrophy

Fuchs endothelial corneal dystrophy is a heterogenous disease with multifactorial etiology, and genetic, epigenetic, and exogenous factors contributing to its pathogenesis. DNA damage plays a significant role, with ultraviolet-A (UV-A) emerging as a key contributing factor. We investigate the potential application of neuropeptide α-melanocyte stimulating hormone (α-MSH) in mitigating oxidative stress induced endothelial damage. First, we examined the effects of α-MSH on a cultured human corneal endothelial cell line (HCEnC-21T) exposed to hydrogen peroxide (H2O2) induced oxidative DNA damage. We performed immunofluorescence and flow cytometry to assess DNA damage and cell death in the cultured cells. Additionally, we used an established mouse model that utilizes ultraviolet light to induce corneal endothelial cell damage resulting in decreased CEnC number, increased cell size variability, and decreased percentage of hexagonal cells. This endothelial decompensation leads to an increase in corneal thickness. Following UV-A exposure, the mice were systemically treated with α-MSH, either immediately after exposure (early treatment) or beginning two weeks post-exposure (delayed treatment). To evaluate treatment efficacy, we analyzed CEnC density and morphology using in vivo confocal microscopy, and central corneal thickness using anterior segment optical coherence tomography. Our findings demonstrated that α-MSH treatment effectively protects HCEnC-21T from free-radical induced oxidative DNA damage and subsequent cell death. In vivo, α-MSH treatment, mitigated the loss of CEnC density, deterioration of cell morphology and suppression of the resultant corneal swelling. These results underline the potential application of α-MSH as a therapeutic agent for mitigating corneal endothelial damage.

The ROCK inhibitor netarsudil in the treatment of corneal endothelial decompensation caused by corneal endotheliitis: A case report and literature review

Proper hydration and the clarity of the cornea are maintained through the crucial function of the corneal endothelium. Inflammation of the corneal endothelium, known as endotheliitis, can disrupt endothelial function, resulting in alterations to vision. Corneal endotheliitis is characterised by corneal oedema, the presence of keratic precipitates, inflammation within the anterior chamber, and occasionally, limbal injection, neovascularisation, and the concurrent or overlapping presence of uveitis. The aetiology of this condition is diverse, predominantly viral, but it may also be drug-induced, result from bacterial or fungal infections, be associated with systemic diseases and procedures, or remain idiopathic with no identifiable cause. To date, no standardised protocol for the treatment of this ocular disease exists, and in severe cases, corneal transplantation may be required. A 31-year-old male was transferred to our hospital for the management of corneal endothelial decompensation resulting from corneal endotheliitis. Hormonal therapy and antiviral medications proved ineffective, rendering the patient a candidate for corneal transplantation. As a final measure, treatment with the ROCK inhibitor netarsudil was initiated. The patient demonstrated significant improvement in symptoms, and the inflammation was successfully managed after nine months. In this study, a novel approach employing ROCK inhibitor therapy was utilised for the treatment of corneal endotheliitis, leading to marked recovery during patient follow-up. This case report represents the inaugural application of the ROCK inhibitor netarsudil in managing corneal endothelial decompensation attributed to corneal endotheliitis. These findings suggest that this method warrants consideration as a potential novel treatment option for similar conditions.

Enhanced Migration of Fuchs Corneal Endothelial Cells by Rho Kinase Inhibition: A Novel Ex Vivo Descemet's Stripping Only Model

Descemet's Stripping Only (DSO) is a surgical technique that utilizes the peripheral corneal endothelial cell (CEnC) migration for wound closure. Ripasudil, a Rho-associated protein kinase (ROCK) inhibitor, has shown potential in DSO treatment; however, its mechanism in promoting CEnC migration remains unclear. We observed that ripasudil-treated immortalized normal and Fuchs endothelial corneal dystrophy (FECD) cells exhibited significantly enhanced migration and wound healing, particularly effective in FECD cells. Ripasudil upregulated mRNA expression of Snail Family Transcriptional Repressor (SNAI1/2) and Vimentin (VIM) while decreasing Cadherin (CDH1), indicating endothelial-to-mesenchymal transition (EMT) activation. Ripasudil activated Rac1, driving the actin-related protein complex (ARPC2) to the leading edge, facilitating enhanced migration. Ex vivo studies on cadaveric and FECD Descemet's membrane (DM) showed increased migration and proliferation of CEnCs after ripasudil treatment. An ex vivo DSO model demonstrated enhanced migration from the DM to the stroma with ripasudil. Coating small incision lenticule extraction (SMILE) tissues with an FNC coating mix and treating the cells in conjunction with ripasudil further improved migration and resulted in a monolayer formation, as detected by the ZO-1 junctional marker, thereby leading to the reduction in EMT. In conclusion, ripasudil effectively enhanced cellular migration, particularly in a novel ex vivo DSO model, when the stromal microenvironment was modulated. This suggests ripasudil as a promising adjuvant for DSO treatment, highlighting its potential clinical significance.

Current state of endothelial cell therapy

PURPOSE OF REVIEW

Currently, there is heightened interest surrounding endothelial cell therapy for the treatment of corneal edema. The purpose of this review article is to describe and summarize the background information as well as the research surrounding the emerging treatment modalities for endothelial cell therapy.

RECENT FINDINGS

Marked advancements have been made in the translational research in this area, and increasing refinements have been demonstrated in the treatment protocols for cell therapy. Human clinical trials in this field are ongoing, specifically, in the area of injected human corneal endothelial cells (HCECs), with early results showing favorable safety and efficacy profiles.

SUMMARY

Efficient and effective delivery of HCECs to patients with corneal edema and dysfunction now appears feasible, and the results from ongoing human clinical trials are much anticipated. Adjunct therapeutics-in the form of pharmacological agents and/or surgical techniques, such as descemetorhexis-will likely continue to play an important role in defining the future of endothelial cell therapy.

Rho-Associated Protein Kinase Activity Is Required for Tissue Homeostasis in the Xenopus laevis Ciliated Epithelium

Lung epithelial development relies on the proper balance of cell proliferation and differentiation to maintain homeostasis. When this balance is disturbed, it can lead to diseases like cancer, where cells undergo hyperproliferation and then can undergo migration and metastasis. Lung cancer is one of the deadliest cancers, and even though there are a variety of therapeutic approaches, there are cases where treatment remains elusive. The rho-associated protein kinase (ROCK) has been thought to be an ideal molecular target due to its role in activating oncogenic signaling pathways. However, in a variety of cases, inhibition of ROCK has been shown to have the opposite outcome. Here, we show that ROCK inhibition with y-27632 causes abnormal epithelial tissue development in Xenopus laevis embryonic skin, which is an ideal model for studying lung cancer development. We found that treatment with y-27632 caused an increase in proliferation and the formation of ciliated epithelial outgrowths along the tail edge. Our results suggest that, in certain cases, ROCK inhibition can disturb tissue homeostasis. We anticipate that these findings could provide insight into possible mechanisms to overcome instances when ROCK inhibition results in heightened proliferation. Also, these findings are significant because y-27632 is a common pharmacological inhibitor used to study ROCK signaling, so it is important to know that in certain in vivo developmental models and conditions, this treatment can enhance proliferation rather than lead to cell cycle suppression.

Status and prospects for the development of regenerative therapies for corneal and ocular diseases

Among the regenerative therapies being put into clinical use, the field of corneal regenerative therapy is one of the most advanced, with several regulatory approved products. This article describes the progress from initial development through to clinical application in the eye field, with a particular focus on therapies for corneal epithelial and endothelial diseases that have already been regulatory approved as regenerative therapy products. The applications of regenerative therapy to the corneal epithelium were attempted and confirmed earlier than other parts of the cornea, following advancements in basic research on corneal epithelial stem cells. Based on these advances, four regenerative therapy products for corneal epithelial disease, each employing distinct cell sources and culture techniques, have been commercialized since the regulatory approval of Holoclar® in Italy as a regenerative therapy product for corneal epithelial disease in 2015. Corneal endothelial regenerative therapy was started by the development of an in vitro method to expand corneal endothelial cells which do not proliferate in adults. The product was approved in Japan as Vyznova® in 2023. The development of regenerative therapies for retinal and ocular surface diseases is actively being pursued, and these therapies use somatic stem cells and pluripotent stem cells (PSCs), especially induced pluripotent stem cells (iPSCs). Accordingly, the eye field is anticipated to play a pioneering role in regenerative therapy development going forward.

Transcription factor 4 promotes increased corneal endothelial cellular migration by altering microtubules in Fuchs endothelial corneal dystrophy

Fuchs endothelial corneal dystrophy (FECD) is a complex corneal disease characterized by the progressive decline and morphological changes of corneal endothelial cells (CECs) that leads to corneal edema and vision loss. The most common mutation in FECD is an intronic CTG repeat expansion in transcription factor 4 (TCF4) that leads to its altered expression. Corneal endothelial wound healing occurs primarily through cell enlargement and migration, and FECD CECs have been shown to display increased migration speeds. In this study, we aim to determine whether TCF4 can promote cellular migration in FECD CECs. We generated stable CEC lines derived from FECD patients that overexpressed different TCF4 isoforms and investigated epithelial-to-mesenchymal (EMT) expression, morphological analysis and cellular migration speeds. We found that full length TCF4-B isoform overexpression promotes cellular migration in FECD CECs in an EMT-independent manner. RNA-sequencing identified several pathways including the negative regulation of microtubules, with TUBB4A (tubulin beta 4A class IVa) as the top upregulated gene. TUBB4A expression was increased in FECD ex vivo specimens, and there was altered expression of cytoskeleton proteins, tubulin and actin, compared to normal healthy donor ex vivo specimens. Additionally, there was increased acetylation and detyrosination of microtubules in FECD supporting that microtubule stability is altered in FECD and could promote cellular migration. Future studies could be aimed at investigating if targeting the cytoskeleton and microtubules would have therapeutic potential for FECD by promoting cellular migration and regeneration.

Dynamic changes of endothelial and stromal cilia are required for the maintenance of corneal homeostasis

Primary cilia are distributed extensively within the corneal epithelium and endothelium. However, the presence of cilia in the corneal stroma and the dynamic changes and roles of endothelial and stromal cilia in corneal homeostasis remain largely unknown. Here, we present compelling evidence for the presence of primary cilia in the corneal stroma, both in vivo and in vitro. We also demonstrate dynamic changes of both endothelial and stromal cilia during corneal development. In addition, our data show that cryoinjury triggers dramatic cilium formation in the corneal endothelium and stroma. Furthermore, depletion of cilia in mutant mice lacking intraflagellar transport protein 88 compromises the corneal endothelial capacity to establish the effective tissue barrier, leading to an upregulation of α-smooth muscle actin within the corneal stroma in response to cryoinjury. These observations underscore the essential involvement of corneal endothelial and stromal cilia in maintaining corneal homeostasis and provide an innovative strategy for the treatment of corneal injuries and diseases.

The Role of Rho Kinase Inhibitors in Corneal Diseases

The cornea, as the outermost layer of the eye, plays a crucial role in vision by focusing light onto the retina. Various diseases and injuries can compromise its clarity, leading to impaired vision. This review aims to provide a thorough overview of the pharmacological properties, therapeutic potential and associated risks of Rho-associated protein kinase (ROCK) inhibitors in the management of corneal diseases. The article focuses on four key ROCK inhibitors: Y-27632, fasudil, ripasudil, and netarsudil, providing a comparative examination. Studies supporting the use of ROCK inhibitors highlight their efficacy across diverse corneal conditions. In Fuchs' endothelial corneal dystrophy, studies on the application of Y-27632, ripasudil, and netarsudil demonstrated noteworthy enhancements in corneal clarity, endothelial cell density, and visual acuity. In pseudophakic bullous keratopathy, the injection of Y-27632 together with cultured corneal endothelial cells into the anterior chamber lead to enhanced corneal endothelial cell density and improved visual acuity. Animal models simulating chemical injury to the cornea showed a reduction of neovascularization and epithelial defects after application of fasudil and in a case of iridocorneal endothelial syndrome netarsudil improved corneal edema. Addressing safety considerations, netarsudil and ripasudil, both clinically approved, exhibit adverse events such as conjunctival hyperemia, conjunctival hemorrhage, cornea verticillata, conjunctivitis, and blepharitis. Monitoring patients during treatment becomes crucial to balancing the potential therapeutic benefits with these associated risks. In conclusion, ROCK inhibitors, particularly netarsudil and ripasudil, offer promise in managing corneal diseases. The comparative analysis of their pharmacological properties and studies supporting their efficacy underscore their potential therapeutic significance. However, ongoing research is paramount to comprehensively understand their safety profiles and long-term outcomes in diverse corneal conditions, guiding their optimal application in clinical practice.

A Case of Transparent Cornea Maintained after Removal of Dislocated Graft from Descemet's Stripping Automated Endothelial Keratoplasty

Introduction

Corneal graft detachment is a major postoperative complication of Descemet's stripping automated endothelial keratoplasty (DSAEK). When a corneal graft becomes detached, corneal endothelial function generally fails, and repeat corneal transplantation is required. Herein, we report a rare case in which a transparent cornea was maintained after the removal of a dislocated DSAEK graft.

Case Presentation

A 79-year-old woman with a residual lens cortex who had undergone cataract surgery was referred to our hospital. The cortex was removed, and bullous keratopathy progressed. Six months after the initial surgery, DSAEK was performed under topical anesthesia without any complications. Although the corneal graft had attached fairly well, it detached from the host cornea 3 weeks later. Two months after DSAEK, an air tamponade was used to treat the anterior chamber with single interrupted suturing; however, the graft detached again, except for the suture site. Because the detached cornea became cloudy in the anterior chamber, it was surgically removed 8 months after DSAEK. Accordingly, the host cornea transparency improved to a best-corrected visual acuity of 0.8 with a rigid gas permeable lens and a central corneal thickness of 580 μm. The corneal endothelial cell density was 995 cells/mm2.

Conclusion

Removal of the corneal graft from the dislocated cloudy graft improved the visual acuity of this patient after DSAEK. The condition of the cornea should be carefully monitored after corneal endothelial transplantation, even after the graft has been dislocated.

ROCK Inhibitors as an Alternative Therapy for Corneal Grafting: A Systematic Review

Currently, corneal blindness is affecting >10 million individuals worldwide, and there is a significant unmet medical need because only 1.5% of transplantation needs are met globally due to a lack of high-quality grafts. In light of this global health disaster, researchers are developing corneal substitutes that can resemble the human cornea in vivo and replace human donor tissue. Thus, this review examines ROCK (Rho-associated coiled-coil containing protein kinases) inhibitors as a potential corneal wound-healing (CWH) therapy by reviewing the existing clinical and nonclinical findings. The systematic review was done from PubMed, Scopus, Web of Science, and Google Scholar for CWH, corneal injury, corneal endothelial wound healing, ROCK inhibitors, Fasudil, Netarsudil, Ripasudil, Y-27632, clinical trial, clinical study, case series, case reports, preclinical study, in vivo, and in vitro studies. After removing duplicates, all downloaded articles were examined. The literature search included the data till January 2023. This review summarized the results of ROCK inhibitors in clinical and preclinical trials. In a clinical trial, various ROCK inhibitors improved CWH in individuals with open-angle glaucoma, cataract, iris cyst, ocular hypertension, and other ocular diseases. ROCK inhibitors also improved ocular wound healing by increasing cell adhesion, migration, and proliferation in vitro and in vivo. ROCK inhibitors have antifibrotic, antiangiogenic, anti-inflammatory, and antiapoptotic characteristics in CWH, according to the existing research. ROCK inhibitors were effective topical treatments for corneal infections. Ripasudil, Y-27632, H-1152, Y-39983, and AMA0526 are a few new ROCK inhibitors that may help CWH and replace human donor tissue.

A Protective Effect of Pirfenidone in Lung Fibroblast-Endothelial Cell Network via Inhibition of Rho-Kinase Activity

Pulmonary fibrosis is a life-threatening disease that has been attributed to several causes. Specifically, vascular injury is thought to be involved in the pathogenesis of fibrosis. The effects of the antifibrotic drug pirfenidone on angiogenesis have not been fully elucidated. This study aimed to investigate the effects of pirfenidone in human lung fibroblast-endothelial cell co-culture network formation and to analyze the underlying molecular mechanisms. Human lung fibroblasts were co-cultured with human umbilical vein endothelial cells to establish a co-culture network cell sheet. The influence of pirfenidone was evaluated for protective effect on the endothelial network in cell sheets stimulated with transforming growth factor β (TGF-β). Results indicated that TGF-β disrupted the network formation. Pirfenidone and Y27632 (Rho-associated coiled-coil containing protein kinase [Rho-kinase or ROCK] inhibitor) protected against the TGF-β-induced endothelial network disruption. TGF-β activated Rho-kinase signaling in cells composing the co-culture cell sheet, whereas pirfenidone and Y27632 inhibited these effects. In conclusion, TGF-β-induced Rho-kinase activation and disrupted endothelial network formation. Pirfenidone suppressed TGF-β-induced Rho-kinase activity in cell sheets, thereby enabling vascular endothelial cells networks to be preserved in the cell sheets. These findings suggest that pirfenidone has potential vascular network-preserving effect via inhibiting Rho-kinase activity in vascular injury, which is a precursor to pulmonary fibrosis.

Role of NADPH Oxidase 4 in Corneal Endothelial Cells Is Mediated by Endoplasmic Reticulum Stress and Autophagy

Human corneal-endothelial cells (hCEnCs) are located on the inner layer of the cornea. Injury to CEnCs leads to permanent corneal edema, requiring corneal transplantation. NADPH oxidase 4 (NOX4) has been reported to be implicated in the pathogenesis of CEnCs diseases. Thus, we investigated the role of NOX4 in CEnCs in this study. In an animal study, siRNA for NOX4 (siNOX4) or plasmid for NOX4 (pNOX4) was introduced into the corneal endothelium of rats by electroporation, using a square-wave electroporator (ECM830, Havard apparatus) to decrease or increase the expression of NOX4, respectively, and the rat corneas were cryoinjured through contact with a metal rod of 3 mm diameter frozen in liquid nitrogen for 10 min. The immunofluorescence staining of NOX4 and 8-OHdG showed that the levels of NOX4 and 8-OHdG were decreased in the siNOX4 group compared to the siControl, and increased in the pNOX4 group compared to the pControl at one week after treatment. Without cryoinjury, corneal opacity was more severe, and the density of CEnCs was lower, in pNOX4-treated rats compared to pControl. After cryoinjury, the corneas were more transparent, and the CEnC density was higher, in siNOX4-treated rats. The hCEnCs were cultured and transfected with siNOX4 and pNOX4. The silencing of NOX4 in hCEnCs resulted in a normal cell shape, higher viability, and higher proliferation rate than those transfected with the siControl, while NOX4 overexpression had the opposite effect. NOX4 overexpression increased the number of senescent cells and intracellular oxidative stress levels. NOX4 overexpression increased ATF4 and ATF6 levels, and nuclear translocation of XBP-1, which is the endoplasmic reticulum (ER) stress marker, while the silencing of NOX4 had the opposite effect. Additionally, the mitochondrial membrane potential was hyperpolarized by the silencing of NOX4, and depolarized by NOX4 overexpression. The LC3II levels, a marker of autophagy, were decreased by the silencing of NOX4, and increased by NOX4 overexpression. In conclusion, NOX4 plays a pivotal role in the wound-healing and senescence of hCEnCs, by modulating oxidative stress, ER stress, and autophagy. The regulation of NOX4 may be a potential therapeutic strategy for regulating the homeostasis of CEnCs, and treating corneal-endothelial diseases.

A p-Tyr42 RhoA Inhibitor Promotes the Regeneration of Human Corneal Endothelial Cells by Ameliorating Cellular Senescence

The development of treatment strategies for human corneal endothelial cells (hCECs) disease is necessary because hCECs do not regenerate in vivo due to the properties that are similar to senescence. This study is performed to investigate the role of a p-Tyr42 RhoA inhibitor (MH4, ELMED Inc., Chuncheon) in transforming growth factor-beta (TGF-β)- or H₂O₂-induced cellular senescence of hCECs. Cultured hCECs were treated with MH4. The cell shape, proliferation rate, and cell cycle phases were analyzed. Moreover, cell adhesion assays and immunofluorescence staining for F-actin, Ki-67, and E-cadherin were performed. Additionally, the cells were treated with TGF-β or H₂O₂ to induce senescence, and mitochondrial oxidative reactive oxygen species (ROS) levels, mitochondrial membrane potential, and NF-κB translocation were evaluated. LC3II/LC3I levels were determined using Western blotting to analyze autophagy. MH4 promotes hCEC proliferation, shifts the cell cycle, attenuates actin distribution, and increases E-cadherin expression. TGF-β and H₂O₂ induce senescence by increasing mitochondrial ROS levels and NF-κB translocation into the nucleus; however, this effect is attenuated by MH4. Moreover, TGF-β and H₂O₂ decrease the mitochondrial membrane potential and induce autophagy, while MH4 reverses these effects. In conclusion, MH4, a p-Tyr42 RhoA inhibitor, promotes the regeneration of hCECs and protects hCECs against TGF-β- and H₂O₂-induced senescence via the ROS/NF-κB/mitochondrial pathway.

Descemet Stripping Only Technique for Corneal Endothelial Damage in Mice

PURPOSE

Descemet stripping only is an emerging surgical technique used to remove central Descemet membrane and corneal endothelial cells in patients with corneal endothelial disease. Here, we describe a murine model of this procedure to help facilitate basic science investigation and evaluation of postoperative outcomes using this surgical technique.

METHODS

Slitlamp biomicroscopy, central corneal thickness assessment (by optical coherence tomography), and immunohistochemistry were used to assess the model through 7 weeks of follow-up.

RESULTS

Complete removal of the endothelium and Descemet membrane was confirmed by slitlamp biomicroscopy and by histology. Central corneal thickness peaked at day 1 postinjury and then declined over the course of 2 weeks to a stable level of persistent edema. Seven weeks postinjury, immunohistochemical staining for ZO-1 showed the area of Descemet stripping was fully covered by enlarged and dysmorphic corneal endothelial cell. No significant ocular complications were appreciated through the end of the follow-up.

CONCLUSIONS

We demonstrate the feasibility of and provide detailed instructions for a murine model of Descemet stripping only. This model provides a potential in vivo platform to investigate the mechanisms and biology of this emerging surgical procedure.

A systematic review on the effects of ROCK inhibitors on proliferation and/or differentiation in human somatic stem cells: A hypothesis that ROCK inhibitors support corneal endothelial healing via acting on the limbal stem cell niche

Rho kinase inhibitors (ROCKi) have attracted growing multidisciplinary interest, particularly in Ophthalmology where the question as to how they promote corneal endothelial healing remains unresolved. Concurrently, stem cell biology has rapidly progressed in unravelling drivers of stem cell (SC) proliferation and differentiation, where mechanical niche factors and the actin cytoskeleton are increasingly recognized as key players. There is mounting evidence from the study of the peripheral corneal endothelium that supports the likelihood of an internal limbal stem cell niche. The possibility that ROCKi stimulate the endothelial SC niche has not been addressed. Furthermore, there is currently a paucity of data that directly evaluates whether ROCKi promotes corneal endothelial healing by acting on this limbal SC niche located near the transition zone. Therefore, we performed a systematic review examining the effects ROCKi on the proliferation and differentiation of human somatic SC, to provide insight into its effects on various human SC populations. An appraisal of electronic searches of four databases identified 1 in vivo and 58 in vitro studies (36 evaluated proliferation while 53 examined differentiation). Types of SC studied included mesenchymal (n = 32), epithelial (n = 11), epidermal (n = 8), hematopoietic and other (n = 8). The ROCK 1/2 selective inhibitor Y-27632 was used in almost all studies (n = 58), while several studies evaluated ≥2 ROCKi (n = 4) including fasudil, H-1152, and KD025. ROCKi significantly influenced human somatic SC proliferation in 81% of studies (29/36) and SC differentiation in 94% of studies (50/53). The present systemic review highlights that ROCKi are influential in regulating human SC proliferation and differentiation, and provides evidence to support the hypothesis that ROCKi promotes corneal endothelial division and maintenance via acting on the inner limbal SC niche.

Induction of Corneal Endothelial-like Cells from Mesenchymal Stem Cells of the Umbilical Cord

Because of the limited differentiation capacity of human corneal endothelial cells (CECs), stem cells have emerged as a potential remedy for corneal endothelial dysfunction (CED). This study aimed to demonstrate the differentiation of human umbilical cord-derived mesenchymal stem cells (UC-MSCs) into CECs and to investigate the efficacy of MSC-induced CEC injection into the anterior chamber in a rabbit model of CED. Human UC-MSCs were differentiated into CECs using medium containing glycogen synthase kinase 3β inhibitor and two types of Rho-associated protein kinase inhibitors. In the MSC-induced CECs, CEC-specific proteins were identified through immunohistochemistry and changes in CEC-specific gene expressions over time were confirmed through quantitative RT-PCR. When MSC-induced CECs were injected into a rabbit model of CED, corneal opacity and neovascularization were improved compared with the non-transplanted control or MSC injection group. We also confirmed that MSC-induced CECs were well engrafted as evidenced by human mitochondrial DNA in the central cornea of an animal model. Therefore, we demonstrated the differentiation of UC-MSCs into CECs in vitro and demonstrated the clinical efficacy of MSC-induced CEC injection, providing in vivo evidence that MSC-induced CECs have potential as a treatment option for CED.

Corneal endothelial wound healing: understanding the regenerative capacity of the innermost layer of the cornea

Currently, there are very few well-established treatments to stimulate corneal endothelial cell regeneration in vivo as a cure for corneal endothelial dysfunctions. The most frequently performed intervention for a damaged or dysfunctional corneal endothelium nowadays is corneal endothelial keratoplasty, also known as lamellar corneal transplantation surgery. Newer medical therapies are emerging and are targeting the regeneration of the corneal endothelium, helping the patients regain their vision without the need for donor tissue. Alternatives to donor tissues are needed as the aging population requiring transplants, has further exacerbated the pressure on the corneal eye banking system. Significant ongoing research efforts in the field of corneal regenerative medicine have been made to elucidate the underlying pathways and effector proteins involved in corneal endothelial regeneration. However, the literature offers little guidance and selective attention to the question of how to fully exploit these pathways. The purpose of this paper is to provide an overview of wound healing characteristics from a biochemical level in the lab to the regenerative features seen in the clinic. Studying the pathways involved in corneal wound healing together with their key effector proteins, can help explain the effect on the proliferation and migration capacity of the corneal endothelial cells.

Magic Bullets: The Coming Age of Meaningful Pharmacological Control of the Corneal Responses to Injury and Disease

Corneal injuries from chemical burns, mechanical trauma, infections, immunological rejections, surgical complications, and some diseases are commonly associated with persistent epithelial defects (PED), neurotrophic epitheliopathy, scarring fibrosis, corneal neovascularization (CNV), and/or corneal endothelial damage that lead to vision loss. Several Food and Drug Administration (FDA) approved medications have recently become available, are currently in clinical trials, or are likely to enter clinical trials in the near future. For example, a 2-week course of topical human recombinant nerve growth factor is frequently an effective treatment for corneal neurotrophic epitheliopathy associated with PEDs. Topical losartan, an angiotensin converting enzyme II receptor antagonist that also inhibits TGF beta signaling, has been shown to effectively decrease myofibroblast generation and scarring fibrosis in alkali burn injury and Descemetorhexis rabbit models. Small molecule topical tyrosine kinase inhibitors, such as sunitinib and axitinib, FDA approved as chemotherapeutic agents to treat specific cancers, have also been found to be effective topical inhibitors of CNV in animal and human trials. Rho-kinase inhibitors, such as ripasudil and netarsudil, that are currently approved agents for the treatment of glaucoma in some countries, have been shown to stimulate corneal endothelial proliferation in animal studies and human trials, and may accelerate the regeneration of Descemet's membrane. These agents, as well as other drugs in development, will be used in targeted combinations to treat corneal pathophysiology associated with epithelial healing disorders, stromal scarring fibrosis, CNV, and corneal endothelial injury during the next decade.

In vitro evaluation of platelet extracellular vesicles (PEVs) for corneal endothelial regeneration

Corneal endothelial cells (CECs) slowly decrease in number with increasing age, which is a clinical issue as these cells have very limited regenerative ability. Therapeutic platelet biomaterials are increasingly used in regenerative medicine and cell therapy because of their safety, cost-effective manufacture, and global availability from collected platelet concentrates (PCs). Platelet extracellular vesicles (PEVs) are a complex mixture of potent bioactive vesicles rich in molecules believed to be instrumental in tissue repair and regeneration. In this study we investigated the feasibility of using a PEVs preparation as an innovative regenerative biotherapy for corneal endothelial dysfunction. The PEVs were isolated from clinical-grade human PC supernatants by 20,000 × g ultracentrifugation and resuspension. PEVs exhibited a regular, fairly rounded shape, with an average size of <200 nm and were present at a concentration of approximately 10¹¹ /mL. PEVs expressed cluster of differentiation 41 (CD41) and CD61, characteristic platelets membrane markers, and CD9 and CD63. ELISA and LC-MS/MS proteomic analyses revealed that the PEVs contained mixtures of growth factors and multiple other trophic factors, as well as proteins related to extracellular exosomes with functional activities associated with cell cadherin and adherens pathways. CECs treated with PEVs showed increased viability, an enhanced wound-healing rate, stronger proliferation markers, and an improved adhesion rate. PEVs did not exert cellular toxicity as evidenced by the maintenance of cellular morphology and preservation of corneal endothelial proteins. These findings clearly support further investigations of PEV biomaterials in animal models for translation as a new CEC regeneration biotherapy.

Near infra-red labelling and tracking of corneal endothelial cells in-vivo

Following corneal transplantation, there is an initial, rapid decline in corneal endothelial cells (CECs) following surgery. Direct imaging of post-transplantation endothelial cells is only possible weeks after surgery and with a limited field of view. We have developed a labelling approach using 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine iodide (DIR) dye solution, that enables tracking of labelled CECs in vivo for at least 1 month. Initial in vitro optimization, with assessments of dye concentration on fluorescence, cellular toxicity and cell migration, performed in propagated primary CECs. Subsequently, in vivo evaluation of cellular labelling was assessed within a rabbit wound healing model. Finally, real-time visualization of human cadaver donor tissue incubated in DIR transplanted into rabbits was achieved using a clinical confocal microscope. Results revealed detectable fluorescence increased with concentration to a plateau of 100 µg/ml, with no toxicity of CECs at any concentration evaluated. DIR-labelled CECs were detectable in vivo up to 1 month, and transplanted labelled donor graft could be visualized and were trackable in vivo. Acute endothelial rejection in 1 rabbit was evidenced by detectable DIR positive cells within the anterior chamber. DIR imaging allowed for detailed imaging of the transplanted human corneal endothelium, and enabled non-invasive observation of the corneal endothelial morphology following transplantation.

Crosslinking-Induced Corneal Endothelium Dysfunction and Its Protection by Topical Ripasudil Treatment

Purpose

To investigate the changes of corneal endothelium under different crosslinking conditions and the protective effect of ripasudil.

Methods

Corneal crosslinking groups were infiltrated with riboflavin and subsequently irradiated with 0.54 J/cm² or 1.08 J/cm² UVA, while noncrosslinking groups included neither UVA nor riboflavin treatment, only 1.08 J/cm² UVA and only riboflavin treatment. Corneal opacity, variations in corneal endothelial cells, and corneal thickness of all groups were observed by slit lamp, in vivo confocal microscopy, and optical coherence tomography. Immunofluorescence staining and scanning electron microscopy were performed to evaluate changes in the structure and function of the corneal endothelium. The mice that received a corneal crosslinking dose of 1.08 J/cm² were instilled with ripasudil to explore its protective effect on the corneal endothelium.

Results

Treatment with UVA and riboflavin caused an increase in corneal opacity and corneal thickness and decreased endothelial cell density. Furthermore, treatment with UVA and riboflavin caused endothelial cell DNA damage and destroyed the tight junction and pump function of the endothelium, while riboflavin or the same dose of UVA alone did not affect the endothelium. Ripasudil reduced DNA damage in endothelial cells, increased the density of cells, and protected the endothelium's integrity and function.

Conclusion

Riboflavin combined with UVA can damage the corneal endothelium's normal functioning. The corneal endothelium's wound healing is dose-dependent, and the ROCK inhibitor ripasudil maintains the endothelium's pump and barrier functions.

Canine endotheliitis: Clinical characteristics, advanced imaging features, and treatment

OBJECTIVE

To describe the clinical findings, multimodal corneal imaging features and treatment in canine patients diagnosed with endotheliitis.

ANIMALS STUDIED

Four canine patients met inclusion criteria for bilateral corneal disease with endothelial inflammation and secondary corneal edema that responded to topical anti-inflammatory treatment.

METHODS

The patients selected underwent a complete ophthalmic examination with emphasis on the cornea including ultrasound pachymetry (USP), Fourier-domain optical coherence tomography (FD-OCT), in vivo confocal microscopy (IVCM), and digital slit lamp photography.

RESULTS

All patients in this study demonstrated thickened corneas due to edema with USP and FD-OCT. With IVCM, mild to severe polymegathism and pleomorphism of corneal endothelial cells, reduced endothelial cell density, hyperreflective keratic precipitates (KPs), and extracellular debris as well as hyporeflective pseudoguttata were observed. With FD-OCT, hyperreflective KPs were commonly observed on the inferior cornea. Clinical examination and advanced imaging results were consistent with a diagnosis of endotheliitis. All patients initially responded to topical anti-inflammatory treatment and required continued therapy; two patients also received topical netarsudil, a rho-associated coiled-coil kinase inhibitor.

CONCLUSION

Endotheliitis should be considered for canine patients with bilateral edema that is most severe in the inferior cornea. Careful inspection of Descemet's membrane-endothelial complex should be performed for KPs or inflammatory debris. Chronic administration of topical anti-inflammatories may be necessary to prevent flare-ups of endotheliitis.

Descemet's membrane injury and regeneration, and posterior corneal fibrosis, in rabbits

The purpose of this investigation was to study Descemet's membrane and corneal endothelial regeneration, myofibroblast generation and disappearance, and TGF beta-1 localization after Descemet's membrane-endothelial excision (Descemetorhexis) in rabbits. Thirty-six rabbits had 8 mm Descemetorhexis and standardized slit lamp photos at 1, 2 and 4 days, 1, 2 and 4 weeks, and 2, 4 and 6 months, as well as multiplex IHC for stromal cell markers keratocan, vimentin, and alpha-smooth muscle actin (SMA); basement membrane (BM) components perlecan, nidogen-1, laminin alpha-5, and collagen type IV; and corneal endothelial marker Na,K-ATPase β1, and TGF beta-1, with ImageJ quantitation. Stromal transparency increased from the periphery beginning at two months after injury and progressed into the central cornea by six months. At six months, central transparency was primarily limited by persistent mid-stromal neovascularization. Stromal myofibroblast zone thickness in the posterior stroma peaked at one month after injury, and then progressively decreased until to six months when few myofibroblasts remained. The regeneration of a laminin alpha-5 and nidogen-1 Descemet's membrane "railroad track" structure was accompanied by corneal endothelial closure and stromal cell production of BM components in corneas from four to six months after injury. TGF beta-1 deposition at the posterior corneal surface from the aqueous humor peaked at one day after Descemetorhexis and diminished even before regeneration of the endothelium and Descemet's membrane. This decrease was associated with collagen type IV protein production by corneal fibroblasts, and possibly myofibroblasts, in the posterior stroma. Descemet's membrane and the corneal endothelium regenerated in the rabbit cornea by six months after eight mm Descemetorhexis. Real-time quantitative RT-PCR experiments in vitro with marker-verified rabbit corneal cells found that 5 ng/ml or 10 ng/ml TGF beta-1 upregulated col4a1 or col4a2 mRNA expression after 6 h or 12 h of exposure in corneal fibroblasts, but not in myofibroblasts. Stromal cells produced large amounts of collagen type IV that likely decreased TGF beta-1 penetration into the stroma and facilitated the resolution of myofibroblast-generated fibrosis.

Endothelial Cell Migration Regulated by Surface Topography of Poly(ε-caprolactone) Nanofibers

The study of cell migration on biomaterials is of great significance in tissue engineering and regenerative medicine. In recent years, there has been increasing evidence that the physical properties of the extracellular matrix (ECM), such as surface topography, affect various cellular behaviors such as proliferation, adhesion, and migration. However, the biological mechanism of surface topography influencing cellular behavior is still unclear. In this study, we prepared polycaprolactone (PCL) fibrous materials with different surface microstructures by solvent casting, electrospinning, and self-induced crystallization. The corresponding topographical structure obtained is a two-dimensional (2D) flat surface, 2.5-dimensional (2.5D) fibers, and three-dimensional (3D) fibers with a multilevel microstructure. We then investigated the effects of the complex topographical structure on endothelial cell migration. Our study demonstrates that cells can sense the changes of micro- and nanomorphology on the surface of materials, adapt to the physical environment through biochemical reactions, and regulate actin polymerization and directional migration through Rac1 and Cdc42. The cells on the nanofibers are elongated spindles, and the positive feedback of cell adhesion and actin polymerization along the fiber direction makes the plasma membrane continue to protrude, promoting cell polarization and directional migration. This study might provide new insights into the biomaterial design, especially those used for artificial vascular grafts.

A purified human platelet pellet lysate rich in neurotrophic factors and antioxidants repairs and protects corneal endothelial cells from oxidative stress

Human platelet lysate (HPL) is a complex mixture of potent bioactive molecules instrumental in tissue repair and regeneration. Due to their remarkable safety, cost-effective production, and availability at global level from collected platelet concentrates, HPLs can become a powerful biotherapy for various therapeutic applications, if standardized and carefully validated through pre-clinical and clinical studies. In this work, the possibility to use a tailor-made HPL as a corneal transplant alternative to treat the gradual decrease in the number of corneal endothelial cells (CECs) associated with aging, was evaluated. The HPL preparation was thoroughly characterized using various proteomics tools that revealed a remarkable richness in multiple growth factors and antioxidants. Treatment of B4G12 and BCE C/D-1b CECs with the HPL increased their viability, enhanced the wound closure rate, and maintained cell growth and typical hexagonal morphology. Besides, this HPL significantly protected against tert-butyl hydroperoxide (TBHP)-induced oxidative stress as evidenced by increasing CEC viability, decreased cell death and reactive oxygen species formation, and enhanced antioxidant capacity. Proteomics analysis of treated CECs confirmed that HPL treatment triggered the corneal healing pathway and enhanced oxidative stress. These data strongly support further pre-clinical evaluation of this tailor-made HPL as a novel CEC regeneration biotherapy. HPL treatment may eventually represent a pragmatic and cost-effective alternative to corneal transplant to treat damages of the corneal endothelium which is a major cause of blindness worldwide.

Primary cell culture of canine corneal endothelial cells

OBJECTIVE

To establish a primary cell culture and clarify the characteristics of canine corneal endothelial cells in vitro.

PROCEDURES

The eyes were enucleated from dogs that were euthanized for reasons unrelated to this study. Enucleated canine eyes were dissected, and the intact corneas were isolated from the globes. Using enzymes, the corneal endothelial cells were dispersed from the cornea. The obtained canine corneal endothelial cells were cultured in a cell culture dish. Cultured corneal endothelial cells were morphologically evaluated using phase-contrast microscopy. Immunohistochemical analysis of the cultured cells, particularly of the corneal endothelial cell marker, zonula occludens-1 (ZO-1), Na⁺ /K⁺ -ATPase, and vimentin, was performed to clarify whether the cultured cells were actually corneal endothelial cells. Furthermore, the post-passage morphology of cultured cells was evaluated.

RESULTS

Canine primary cultured corneal endothelial cells showed morphologically small, cobblestone-like structures. The isolated cells had proliferative ability in vitro and demonstrated positive expression of the corneal endothelial cell markers, ZO-1, Na⁺ /K⁺ -ATPase, and vimentin. However, repeated passages resulted in larger cell sizes as assessed by phase-contrast microscopy. Repeated passages also resulted in lower cell density.

CONCLUSIONS

This study demonstrated the successful culture of canine corneal endothelial cells. This might enhance the understanding of corneal endothelial cell characteristics in dogs.

Case Series: Novel Utilization of Rho-Kinase Inhibitor for the Treatment of Corneal Edema

PURPOSE

To describe 3 cases of corneal clearance after the use of topical rho-kinase inhibitor, netarsudil, in the setting of endothelial cell dysfunction in comparison to one case without corneal clearance after the use of netarsudil.

METHODS

Four patients presenting to a busy academic clinical corneal practice with visual complaints from corneal edema secondary to endothelial cell dysfunction were treated with topical netarsudil one drop daily in the affected eye.

RESULTS

Corneal clearance was observed in 1) a case of peripheral corneal edema in the setting of iridocorneal endothelial syndrome after 4 weeks on netarsudil, 2) a case of corneal edema in the setting of early penetrating keratoplasty graft failure after 2-week use of netarsudil, and 3) a case of corneal edema in the setting of chronic penetrating keratoplasty graft failure after 4-week use of netarsudil. Corneal clearance was not observed in a case of corneal edema in the setting of pseudophakic bullous keratopathy from previous complicated intraocular lens exchange surgery with placement of an anterior chamber intraocular lens after the use of netarsudil for 12 weeks.

CONCLUSIONS

Addition of topical rho-kinase inhibitor in the form of netarsudil can result in corneal clearance in a variety of certain cases of endothelial cell dysfunction, not previously documented in the literature.

Animal models of corneal endothelial dysfunction to facilitate development of novel therapies

Progressive corneal endothelial disease eventually leads to corneal edema and vision loss due to the limited regenerative capacity of the corneal endothelium in vivo and is a major indication for corneal transplantation. Despite the relatively high success rate of corneal transplantation, there remains a pressing global clinical need to identify improved therapeutic strategies to address this debilitating condition. To evaluate the safety and efficacy of novel therapeutics, there is a growing demand for pre-clinical animal models of corneal endothelial dysfunction. In this review, experimentally induced, spontaneously occurring and genetically modified animal models of corneal endothelial dysfunction are described to assist researchers in making informed decisions regarding the selection of the most appropriate animal models to meet their research goals.

Corneal supply and the use of technology to reduce its demand: A review

Recovery and access to end-of-life corneal tissue for corneal transplantation, training and research is globally maldistributed. The reasons for the maldistribution are complex and multifaceted, and not well defined or understood. Currently there are few solutions available to effectively address these issues. This review provides an overview of the system, key issues impacting recovery and allocation and emphasises how end-user ophthalmologists and researchers, with support from administrators and the wider sector, can assist in increasing access long-term through sustaining eye banks nationally and globally. We posit that prevention measures and improved surgical techniques, together with the development of novel therapies will play a significant role in reducing demand and enhance the equitable allocation of corneas.

Potential Functional Restoration of Corneal Endothelial Cells in Fuchs Endothelial Corneal Dystrophy by ROCK Inhibitor (Ripasudil)

PURPOSE

Rho-associated kinase (ROCK) inhibitors have been successfully used as a rescue strategy in eyes that failed to clear after descemetorhexis without endothelial graft for treatment of Fuchs endothelial corneal dystrophy (FECD). The functional mechanisms by which ROCK inhibitors modulate corneal endothelial cell regeneration in FECD patients have, however, not been clarified. Here, we analyzed the effect of the ROCK inhibitor ripasudil on corneal endothelial cells of FECD patients and normal donors using ex vivo tissue and in vitro cellular models.

DESIGN

Experimental study: laboratory investigation.

METHODS

This institutional study used endothelial cell-Descemet membrane lamellae from FECD patients (n = 450) undergoing Descemet membrane endothelial keratoplasty (FECD ex vivo model), normal research-grade donor corneas (n = 30) after scraping off central endothelial cells (ex vivo wound healing model), normal donor corneas (n = 20) without endothelial injury, and immortalized cell lines (n = 3) generated from FECD patients (FECD in vitro model). Descemet membrane lamellae were dissected into halves and incubated for 24-72 hours in storage medium with or without a single dose of 30 μM ripasudil. The effects of ripasudil on expression of genes and proteins related to endothelial cell proliferation, migration, functionality, and endothelial-to-mesenchymal transition were analyzed and complemented by functional assays on FECD cell lines.

RESULTS

A single dose of ripasudil induced significant upregulation of genes and proteins related to cell cycle progression, cell-matrix adhesion and migration, as well as endothelial barrier and pump function up to 72 hours, whereas classical markers of endothelial-to-mesenchymal transition were downregulated in both FECD and normal specimens compared to unstimulated controls ex vivo. In addition to stimulation of proliferation and migration, ripasudil-induced changes in expression of functional signature genes could be also verified in FECD cell lines in vitro.

CONCLUSIONS

These data support the concept that inhibition of ROCK signaling represents a potent tool in regenerative therapies in FECD patients through reactivation of cell proliferation and migration as well as restoration of endothelial pump and barrier function without inducing adverse phenotypic changes.

Biofabrication of chitosan/chitosan nanoparticles/polycaprolactone transparent membrane for corneal endothelial tissue engineering

We aimed to construct a biodegradable transparent scaffold for culturing corneal endothelial cells by incorporating chitosan nanoparticles (CSNPs) into chitosan/polycaprolactone (PCL) membranes. Various ratios of CSNP/PCL were prepared in the presence of constant concentration of chitosan and the films were constructed by solvent casting method. Scaffold properties including transparency, surface wettability, FTIR, and biocompatibility were examined. SEM imaging, H&E staining, and cell count were performed to investigate the HCECs adhesion. The phenotypic maintenance of the cells during culture was investigated by flow cytometry. Transparency and surface wettability improved by increasing the CSNP/PCL ratio. The CSNP/PCL 50/25, which has the lowest WCA, showed comparable transparency with human acellular corneal stroma. The scaffold was not cytotoxic and promoted the HCECs proliferation as evaluated by MTT assay. Cell counting, flow cytometry, SEM, and H&E results showed appropriate attachment of HCECs to the scaffold which formed a compact monolayer. The developed scaffold seems to be suitable for use in corneal endothelial regeneration in terms of transparency and biocompatibility.

Increased Corneal Endothelial Cell Migration in Fuchs Endothelial Corneal Dystrophy: A Live Cell Imaging Study

Purpose

To investigate if corneal endothelial cells (CECs) in Fuchs endothelial corneal dystrophy (FECD) have altered cellular migration compared with normal controls.

Design

Comparative analysis.

Materials

Descemet's membrane and CECs derived from patients with FECD undergoing endothelial keratoplasty or normal cadaveric donors.

Methods

Ex vivo specimens were used for live cell imaging and generation of immortalized cell lines. Live imaging was performed on FECD and normal CECs and on ex vivo specimens transfected with green fluorescent protein. Migration speeds were determined as a function of cellular density using automated cell tracking. Ex vivo specimens were classified as either FECD or normal low cell density (nonconfluent) or high cell density (confluent). Scratch assay was performed on CECs seeded at high confluence to determine migration speed. Genetic analysis from blood samples or CECs was performed to detect a CTG repeat expansion in the TCF4 gene.

Main Outcome Measures

Mean cell migration speed.

Results

Fuchs endothelial corneal dystrophy CECs in low cell density areas displayed increased mean speed (0.391 ± 0.005 μm/minute vs. 0.364 ± 0.005 μm/minute; P < 0.001) and mean maximum speed (0.961 ± 0.010 μm/minute vs. 0.787 ± 0.011 μm/minute; P < 0.001) compared with normal CECs, and increased mean maximum speed (0.778 ± 0.014 μm/minute vs. 0.680 ± 0.011 μm/minute; P < 0.001) in high cell density areas ex vivo. Similarly, FECD CECs displayed increased mean speed compared with normal CECs (1.958 ± 0.020 μm/minute vs. 2.227 ± 0.021 μm/minute vs. 1.567 ± 0.019 μm/minute; P < 0.001) under nonconfluent conditions in vitro. Moreover, FECD CECs also displayed increased mean speed compared with normal CECs under high confluent conditions as detected by scratch assay (37.2 ± 1.1% vs. 44.3 ± 4.1% vs. 70.7 ± 5.2%; P < 0.001). Morphologic analysis showed that FECD CECs displayed an increased fibroblastic phenotype as detected by filamentous-actin labeling.

Conclusions

Fuchs endothelial corneal dystrophy CECs demonstrated increased migration speed compared with normal CECs. Further investigation into the mechanisms of heightened cell migration in FECD is needed and may provide insight into its pathogenesis, as well as having implications on descemetorhexis without endothelial keratoplasty.

Multiple roles of FGF10 in the regulation of corneal endothelial wound healing

Corneal endothelial dysfunction usually induces corneal haze and oedema, which seriously affect visual function. The main therapeutic strategy for this condition is corneal transplantation, but the use of this strategy is limited by the shortage of healthy donor corneas. Compared with corneal transplantation, drug intervention is less invasive and more accessible; thus, finding an effective pharmaceutical alternative for cornea transplantation is critical for the treatment of corneal endothelial dysfunction. In this study, we established a rabbit scratch model to investigate the effect of fibroblast growth factor 10 (FGF10) on corneal endothelial wound healing. Results showed that FGF10 injection accelerated the recovery of corneal transparency and increased the protein expression levels of ZO1, Na⁺/K⁺-ATPase and AQP-1. Moreover, FGF10 significantly inhibited the expression levels of endothelial-to-mesenchymal transition proteins and reduced the expression levels of the proinflammatory factors IL-1β and TNF-α in the anterior chamber aqueous humour. FGF10 also enhanced the Na⁺/K⁺-ATPase activity by enhancing mitochondrial function as a result of its direct interaction with its conjugate receptor. Thus, FGF10 could be a new pharmaceutical preparation as treatment for corneal endothelial dysfunction.

Regenerative responses of rabbit corneal endothelial cells to stimulation by fibroblast growth factor 1 (FGF1) derivatives, TTHX1001 and TTHX1114

Utilising rabbit corneal endothelial cells (CEC) in three different paradigms, two human FGF1 derivatives (TTHX1001 and TTHX1114), engineered to exhibit greater stability, were tested as proliferative agents. Primary CECs and mouse NIH 3T3 cells treated with the two FGF1 derivatives showed equivalent EC₅₀ ranges (3.3-24 vs.1.9-16. ng/mL) and, in organ culture, chemically lesioned corneas regained half of the lost endothelial layer in three days after treatment with the FGF1 derivatives as compared to controls. In vivo, following cryolesioning, the CEC monolayer, as judged by specular microscopy, regenerated 10-11 days faster when treated with TTHX1001. Over two weeks, all treated eyes showed clearing of opacity about twice that of untreated controls. In all three rabbit models, both FGF1 derivatives were effective in inducing CEC proliferation over control conditions, supporting the prediction that these stabilised FGF1 derivatives can potentially regenerate corneal endothelial deficits in humans.

Focus on cell therapy to treat corneal endothelial diseases

The cornea is a multi-layered structure which allows fine refraction and provides both resistance to external insults and adequate transparency. The corneal endothelium ensures stromal hydration, failure of which, such as in Fuchs endothelial corneal dystrophy, after trauma or in aging, may lead to loss of corneal transparency and induce blindness. Currently, no efficient therapeutic alternatives exist except for corneal grafting. Thus corneal tissue engineering represents a valuable alternative approach, which may overcome cornea donor shortage. Several studies describe protocols to isolate, differentiate, and cultivate corneal endothelial cells (CEnCs) in vitro. Two main in vitro strategies can be described: expansion of eye-native cell populations, such as CEnCs, or the production and expansion of CEnCs from non-eye native cell populations, such as induced Pluripotent Stem Cells (iPSCs). The challenge with these cells is to obtain a monolayer of CEnCs on a biocompatible carrier, with a specific morphology (flat hexagonal cells), and with specific functions such as programmed cell cycle arrest. Another issue for this cell culture methodology is to define the adapted protocol (media, trophic factors, timeframe) that can mimic physiological development. Additionally, contamination by other cell types still represents a huge problem. Thus, purification methods, such as Fluorescence Activated Cell Sorting (FACS), Magnetic Ativated Cell Sorting (MACS) or Sedimentation Field Flow Fractionation (SdFFF) are useful. Animal models are also crucial to provide a translational approach for these therapies, integrating macro- and microenvironment influences, systemic hormonal or immune responses, and exogenous interactions. Non-eye native cell graft protocols are constantly improving both in efficacy and safety, with the aim of being the most suitable candidate for corneal therapies in future routine practice. The aim of this work is to review these different aspects with a special focus on issues facing CEnC culture in vitro, and to highlight animal graft models adapted to screen the efficacy of these different protocols.

Fuchs endothelial corneal dystrophy: The vicious cycle of Fuchs pathogenesis

Fuchs endothelial corneal dystrophy (FECD) is the most common primary corneal endothelial dystrophy and the leading indication for corneal transplantation worldwide. FECD is characterized by the progressive decline of corneal endothelial cells (CECs) and the formation of extracellular matrix (ECM) excrescences in Descemet's membrane (DM), called guttae, that lead to corneal edema and loss of vision. FECD typically manifests in the fifth decades of life and has a greater incidence in women. FECD is a complex and heterogeneous genetic disease where interaction between genetic and environmental factors results in cellular apoptosis and aberrant ECM deposition. In this review, we will discuss a complex interplay of genetic, epigenetic, and exogenous factors in inciting oxidative stress, auto(mito)phagy, unfolded protein response, and mitochondrial dysfunction during CEC degeneration. Specifically, we explore the factors that influence cellular fate to undergo apoptosis, senescence, and endothelial-to-mesenchymal transition. These findings will highlight the importance of abnormal CEC-DM interactions in triggering the vicious cycle of FECD pathogenesis. We will also review clinical characteristics, diagnostic tools, and current medical and surgical management options for FECD patients. These new paradigms in FECD pathogenesis present an opportunity to develop novel therapeutics for the treatment of FECD.

Transient Reticular Cystic Corneal Epithelial Edema With Topical Netarsudil: A Case Series and Review

PURPOSE

To describe cases in which netarsudil ophthalmic solution 0.02% precipitated reversible, reticular cystic epithelial edema.

METHODS

A retrospective case review at the Brooklyn Veteran's Association Hospital of patients with corneal stromal edema that were treated with netarsudil and subsequently developed cystic epithelial edema.

RESULTS

Four male patients with a mean age of 72 ± 8.0 years developed a reticular, honeycomb-like pattern of epithelial edema located in the interpalpebral and inferior cornea. In 3 of 4 patients, epithelial edema arose within 1 month compared with 2 months in 1 patient. New epithelial cysts did not correlate with worsening central corneal thickness and best spectacle-corrected visual acuity in every patient, which was likely due to the location of the cysts. Two of 4 patients developed increased central corneal thickness with worsening best spectacle-corrected visual acuity. In comparison, 1 patient had improvement in both parameters, whereas 1 patient had no significant change. In all cases, there was resolution of the epithelial cysts after discontinuation of netarsudil.

CONCLUSIONS

Although rho-kinase inhibitors have been suggested to improve endothelial function, we have documented worsening epithelial cysts in a subset of patients with pre-existing corneal edema. These effects of netarsudil were transient and resolved after discontinuing treatment within 2 weeks in most patients. We hypothesize that the incidence of this adverse finding is more common than previously believed. Nevertheless, large-scale studies are needed to accurately report on the incidence and clinical significance of this novel finding.

Corneal endothelium tissue engineering: An evolution of signaling molecules, cells, and scaffolds toward 3D bioprinting and cell sheets

Cornea is an avascular and transparent tissue that focuses light on retina. Cornea is supported by the corneal-endothelial layer through regulation of hydration homeostasis. Restoring vision in patients afflicted with corneal endothelium dysfunction-mediated blindness most often requires corneal transplantation (CT), which faces considerable constrictions due to donor limitations. An emerging alternative to CT is corneal endothelium tissue engineering (CETE), which involves utilizing scaffold-based methods and scaffold-free strategies. The innovative scaffold-free method is cell sheet engineering, which typically generates cell layers surrounded by an intact extracellular matrix, exhibiting tunable release from the stimuli-responsive surface. In some studies, scaffold-based or scaffold-free technologies have been reported to achieve promising outcomes. However, yet some issues exist in translating CETE from bench to clinical practice. In this review, we compare different corneal endothelium regeneration methods and elaborate on the application of multiple cell types (stem cells, corneal endothelial cells, and endothelial precursors), signaling molecules (growth factors, cytokines, chemical compounds, and small RNAs), and natural and synthetic scaffolds for CETE. Furthermore, we discuss the importance of three-dimensional bioprinting strategies and simulation of Descemet's membrane by biomimetic topography. Finally, we dissected the recent advances, applications, and prospects of cell sheet engineering for CETE.