Corneal Endothelial Cells Over the Past Decade: Are We Missing the Mark(er)?

Case Report: Intraocular foreign body coexisting for 30 years

Background

The majority of IOFBs remain in the posterior segment and those in the anterior chamber are uncommon. We report a case of IOFBs in the anterior chamber for 30 years without any symptoms.

Case presentation

The case involves a 30-year-old male individual who was told to have an abnormality in the anterior chamber of his left eye during a physical examination. However, the patient has had no any ocular discomfort symptom within the past 30 years. At the patient's initial visit, the uncorrected visual acuity of the left eye was 40/50, the corneal endothelial surface exhibited multiple linear and curved scratches, and a transparent foreign body approximately 11 mm in length inhabited in the anterior chamber, touching the endothelium with fan-shaped ends, and the anterior chamber without any signs of inflammation. The endothelial cell count was 1,110 cells/mm2. Considered the persistent damage to the corneal endothelium caused by the foreign body, as well as the uncertainty regarding the path of entry and the characteristics of the foreign body, we surgically extracted the intraocular foreign body. No sight-threatening postoperative complications were noted.

Conclusion

A detailed history collection, a thorough physical examination and modern imaging techniques are beneficial for finding IOFBs. Asymptomatic anterior chamber foreign bodies may also cause potential corneal endothelium injury, which should be carefully examined and extracted using appropriate surgical methods to avoid iatrogenic injury.

Escalón: A Prospective Randomized Trial of Corneal Endothelial Cell Therapy in Subjects With Corneal Edema

PURPOSE

Escalón is a prospective, randomized, double-masked, parallel-group trial designed to evaluate the safety and efficacy of cultured human corneal endothelial cells (CECs) and the Rho-associated protein kinase (ROCK) inhibitor Y-27632 for treating corneal edema secondary to endothelial dysfunction.

METHODS

Eligible eyes with bullous keratopathy (N = 18) or Fuchs dystrophy (N = 4) were randomized to receive endothelial polishing and a single intracameral injection containing 1 x 106 CECs and 10, 20, or 100 μM Y-27632. The primary outcome was safety based on incidence and severity of ocular and nonocular treatment-emergent adverse events (TEAEs). Efficacy outcomes included changes from baseline in central corneal thickness (CCT) and best-corrected visual acuity (BCVA) at all time points up to month 12.

RESULTS

Twenty-two eyes received treatment. Data from all study groups were pooled, as no clinically meaningful differences existed between groups. Study eyes experienced no serious TEAEs. Common study eye TEAEs included posterior capsule opacification (72.7%), pupillary disorders/dyscoria (27.3%), and transient intraocular pressure elevations (22.7%). Mean CCT improved from 697.0 μm at baseline to 571.2 μm at month 12. Mean BCVA improved from 0.995 logMAR at baseline to 0.330 logMAR at month 12. The proportion of all subjects with a ≥ 0.3 LogMAR improvement in BCVA was 88.9% at month 12.

CONCLUSIONS

The study demonstrated that transplantation of cultured CECs with Y-27632 was safe and efficacious across all evaluated doses of Y-27632. No clinically meaningful dose response was seen for Y-27632. This innovative therapeutic approach represents a promising option for treating corneal edema arising from corneal endothelial dysfunction.

Towards Clinical Application: Calcium Waves for In Vitro Qualitative Assessment of Propagated Primary Human Corneal Endothelial Cells

Corneal endothelium cells (CECs) regulate corneal hydration between the leaky barrier of the corneal endothelium and the ionic pumps on the surface of CECs. As CECs do not regenerate, loss of CECs leads to poor vision and corneal blindness. Corneal transplant is the only treatment option; however, there is a severe shortage of donor corneas globally. Cell therapy using propagated primary human CECs is an alternative approach to corneal transplantations, and proof of functionality is crucial for validating such CECs. Expression markers like Na-K-ATPase and ZO-1 are typical but not specific to CECs. Assessing the barrier function of the expanded CECs via electrical resistance (i.e., TEER and Ussing's chamber) involves difficult techniques and is thus impractical for clinical application. Calcium has been demonstrated to affect the paracellular permeability of the corneal endothelium. Its absence alters morphology and disrupts apical junctions in bovine CECs, underscoring its importance. Calcium signaling patterns such as calcium waves affect the rate of wound healing in bovine CECs. Therefore, observing calcium waves in expanded CECs could provide valuable insights into their health and functional integrity. Mechanical or chemical stimulations, combined with Ca2+-sensitive fluorescent dyes and time-lapse imaging, can be used to visualize these waves, which could potentially be used to qualify expanded CECs.

Differentiation of Human Mesenchymal Stem Cells into Corneal Epithelial Cells: Current Progress

The limited availability of corneal tissue grafts poses significant challenges in the treatment of corneal blindness. Novel treatment utilizes stem cell grafts transplanted from the healthy side of the cornea to the damaged side. However, this procedure is only possible for those who have one-sided corneal blindness. Human stem cells offer promising potential for corneal tissue engineering, providing an alternative solution. Among the different types of stem cells, mesenchymal stem cells (MSCs) stand out due to their abundance and ease of isolation. Human MSCs can be derived from bone marrow, adipose, and umbilical cord tissues. Differentiating MSC toward corneal tissue can be achieved through several methods including chemical induction and co-culture with adult corneal cells such as human limbal epithelial stem cells (LESCs) and human corneal epithelial cells (hTCEpi). Adipose-derived stem cells (ADSCs) are the most common type of MSC that has been studied for corneal differentiation. Corneal epithelial cells are the most common corneal cell type targeted by researchers for corneal differentiation. Chemical induction with small molecules, especially bone morphogenetic protein 4 (BMP4), all-trans retinoic acid (ATRA), and epidermal growth factor (EGF), has gained more popularity in corneal epithelial cell differentiation. This review highlights the current progress in utilizing MSCs for corneal differentiation studies, showcasing their potential to revolutionize treatments for corneal blindness.

Factors Affecting the Density of Corneal Endothelial Cells Cultured from Donor Corneas

We investigated which specific correlation exists between the endothelial cell density (ECD) of corneal endothelial cell (CEC) cultures and the features of the donor corneas from which they originate. CEC cultures were prepared from one donor cornea or by pooling together cells of more corneas from elderly donors with ECDs lower or higher than 2000 cells/mm2. The ECDs of such primary cultures were evaluated and showed that that ECDs > 2000 cells/mm2 can be obtained only when CECs are isolated from (1) corneas of young donors; (2) at least two elderly donor corneas (if ECD > 2000 cells/mm2), or three elderly donor corneas (if ECD < 2000 cells/mm2). Secondary cultures are all characterized by ECDs < 2000 cells/mm2. Our study highlights the difficulties in obtaining cultures with ECDs > 2000 cells/mm2. Even if achievable with corneas from young donors, this becomes a challenging task when corneas from elderly donors are used (i.e., the overall majority of those collected by eye banks) and particularly when corneas from elderly donors with ECD < 2000 cells/mm2 are used. Pooling more of two corneas to obtain suitable CECs could technically overcome the problem. The above issues should be tackled appropriately before moving into clinical studies.

Advancements in Polymer Biomaterials as Scaffolds for Corneal Endothelium Tissue Engineering

Corneal endothelial dysfunction is a leading cause of vision loss globally, frequently requiring corneal transplantation. However, the limited availability of donor tissues, particularly in developing countries, has spurred on the exploration of tissue engineering strategies, with a focus on polymer biomaterials as scaffolds for corneal endotlhelium regeneration. This review provides a comprehensive overview of the advancements in polymer biomaterials, focusing on their role in supporting the growth, differentiation, and functional maintenance of human corneal endothelial cells (CECs). Key properties of scaffold materials, including optical clarity, biocompatibility, biodegradability, mechanical stability, permeability, and surface wettability, are discussed in detail. The review also explores the latest innovations in micro- and nano-topological morphologies, fabrication techniques such as electrospinning and 3D/4D bioprinting, and the integration of drug delivery systems into scaffolds. Despite significant progress, challenges remain in translating these technologies to clinical applications. Future directions for research are highlighted, including the need for improved biomaterial combinations, a deeper understanding of CEC biology, and the development of scalable manufacturing processes. This review aims to serve as a resource for researchers and clinician-scientists seeking to advance the field of corneal endothelium tissue engineering.

Cell therapy in the cornea: The emerging role of microenvironment

The cornea is an ideal testing field for cell therapies. Its highly ordered structure, where specific cell populations are sequestered in different layers, together with its accessibility, has allowed the development of the first stem cell-based therapy approved by the European Medicine Agency. Today, different techniques have been proposed for autologous and allogeneic limbal and non-limbal cell transplantation. Cell replacement has also been attempted in cases of endothelial cell decompensation as it occurs in Fuchs dystrophy: injection of cultivated allogeneic endothelial cells is now in advanced phases of clinical development. Recently, stromal substitutes have been developed with excellent integration capability and transparency. Finally, cell-derived products, such as exosomes obtained from different sources, have been investigated for the treatment of severe corneal diseases with encouraging results. Optimization of the success rate of cell therapies obviously requires high-quality cultured cells/products, but the role of the surrounding microenvironment is equally important to allow engraftment of transplanted cells, to preserve their functions and, ultimately, lead to restoration of tissue integrity and transparency of the cornea.

Protective effects of curcumin on corneal endothelial cell PANoptosis and monocyte adhesion induced by tumor necrosis factor-alpha and interferon-gamma in rats

Decrease of human corneal endothelial cell (CEC) density leads to corneal edema, progressive corneal opacity, and reduced visual acuity. A reduction in CEC density may be related to elevated levels of inflammatory cytokines, such as tumor necrosis factor (TNF)-α and interferon (INF)-γ. PANoptosis, characterized by the activation of apoptosis, necroptosis, and pyroptosis, could be a factor in the loss of CECs driven by TNF-α and INF-γ. Cytokines also stimulate monocytes adhesion to endothelium. It has been shown in previous research that curcumin plays protective roles against numerous corneal inflammatory diseases. However, it is not determined whether curcumin acts as an anti-PANoptotic agent or if it mitigates monocyte adhesion to CECs. Therefore, this research aimed to explor the potential therapeutic effects of curcumin and its underlying mechanisms in the loss of CECs. CEC injury models were established, and curcumin was injected subconjunctivally. Clinical evaluation of the corneas was conducted using a scoring system and anterior segment photography. Corneal observation was performed with hematoxylin and eosin staining and immunostaining of zona occludens-1(ZO-1). Apoptotic cells within the corneal endothelium were observed using TUNEL staining. The detection of primary proteins expression was accomplished through Western blot analysis. Interleukin (IL)-1β and macrophage chemotactic protein 1 (MCP-1) levels were determined via ELISA, while the expression of cleaved caspase-3, gasdermin-D (GSDMD), phosphor-mixed lineage kinase domain-like protein (p-MLKL) and intercellular cell adhesion molecule-1 were confirmed by immunofluorescence. Myeloperoxidase (MPO) activity was measured in aqueous humors. Curcumin treatment attenuated the loss of CECs and corneal edema caused by TNF-α and IFN-γ. Besides, it decreased the count of TUNEL-positive cells, and inhibited the upregulation of cleaved caspase-3, cleaved caspase-6, cleaved caspase-7, and cleaved poly (ADP-ribose) polymerase. Moreover, both the expression and phosphorylation of MLKL and receptor-interacting protein 3 were decreased in curcumin-treated rats. Furthermore, curcumin also lowered the expression of cleaved caspase-1, diminished the levels of IL1β and MCP-1, and inhibited the activity of MPO. Besides, the expression of intercellular cell adhesion molecule-1, vascular cell adhesion molecule-1, as well as the number of CD11b-positive cells adhered to the CECs decreased for the administration of curcumin.

Comparison of automated corneal endothelial cell analysis in healthy and postoperative eyes with phakic intraocular lens: a cross-sectional study and literature review

PURPOSE

Measurement of corneal endothelial cells is critical for postoperative evaluation of phakic intraocular lens (pIOL) surgery. However, inter-instrument differences in corneal endothelial cell density (ECD) after pIOL implantation have not yet been reported. This study aimed to compare automated corneal endothelial cell analysis between CellChek-20 (Konan Medical, Hyogo, Japan) and EM-4000 (Tomey, Nagoya, Japan) in healthy and postoperative eyes with pIOL.

METHODS

We retrospectively analyzed 154 healthy and 236 postoperative eyes after pIOL surgery. Endothelial cell measurements were performed using CellChek-20 and EM-4000 with autofocusing and automated image analysis. ECD, percentage of hexagonal cells (HEX), coefficient of variation in cell size (CoV), and central corneal thickness (CCT) were compared between the two devices.

RESULTS

The ECDs of the two devices were highly correlated in both healthy (Spearman's correlation coefficient [r] = 0.805; p < 0.001) and postoperative (r = 0.901; p < 0.001) groups. ECD from CellChek-20 was higher than EM-4000 in both healthy (mean difference = 228.9 cells/mm2; p < 0.001) and postoperative (mean difference = 115.6 cells/mm2; p < 0.001) groups. The CCT values also showed a strong correlation in healthy eyes (r = 0.974; p < 0.001) and in postoperative eyes (r = 0.936; p < 0.001); however, significant inter-instrument differences were observed. HEX and CV showed significant differences and relatively weak correlations (r < 0.7) between the two devices in both healthy and postoperative groups.

CONCLUSION

The ECD values between the two instruments were correlated, but that of the CellChek-20 was significantly higher than that of the EM-4000 in both healthy and postoperative eyes after pIOL surgery. Most previous studies have also shown that the Konan software overestimated the ECD compared to other products in automatic measurement mode. The possibility of measurement bias should be considered when replacing equipment used for corneal endothelial cell measurements.

Prediction of the active compounds and mechanism of Biochanin A in the treatment of Legg-Calvé-Perthes disease based on network pharmacology and molecular docking

BACKGROUND

Legg-Calvé-Perthes disease is a special self-limited disease in pediatric orthopedics with a high disability rate and a long-term course, and there is still no clear and effective therapeutic drug in clinic. This study aimed to investigate the potential efficacy of biochanin A, a kind of oxygen-methylated isoflavone compound, in treating Perthes disease based on network pharmacology, molecular docking and in vitro experiments.

METHODS

IL-6 was used to stimulate human umbilical vein endothelial cells to construct endothelial cell dysfunction model. We demonstrated whether biochanin A could alleviate endothelial dysfunction through CCK8 assay, immunofluorescence. Targets of biochanin A from pharmMappeer, SWISS, and TargetNet databases were screened. Targets of endothelial dysfunction were obtained from Genecards and OMIM databases. Protein-protein interaction, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomics analyses were used to analyze the potential target and the key pathway of the anti-endothelial dysfunction activity of biochanin A. To validate the potential target-drug interactions, molecular docking and molecular dynamics simulations were performed and the result was proved by western blot.

RESULTS

It was found that biochanin A can promote the expression of ZO-1, reduce the expression of ICAM-1, which means improving endothelial dysfunction. A total of 585 targets of biochanin A from pharmMappeer, SWISS, and TargetNet databases were screened. A total of 10,832 targets of endothelial dysfunction were obtained from Genecards and OMIM databases. A total of 527 overlapping targets of endothelial dysfunction and biochanin A were obtained. AKT1, TNF-α, VCAM1, ICAM1, and NOS3 might be the key targets of the anti-endothelial dysfunction activity of biochanin A, and the key pathways might be PI3K-Akt and TNF signaling pathways. Molecular docking results indicated that the AKT1 and TNF-α had the highest affinity binding with biochanin A.

CONCLUSION

This study indicates that biochanin A can target AKT1 and TNF-α to alleviate endothelial dysfunction induced by IL-6 in Perthes disease, which provides a theoretical basis for the treatment of Perthes disease by using biochanin A.

Therapeutic future of Fuchs endothelial corneal dystrophy: An ongoing way to explore

Fuchs endothelial corneal dystrophy (FECD) is one of the most common corneal diseases that causes loss of visual acuity in the world. FECD is a genetically and pathogenetically heterogeneous disease that results in the failure of corneal endothelial cells to maintain fluid balance and functional homeostasis of the cornea. Corneal edema, central guttae formation, and bullae development are common corneal pathologies. Currently, the mainstay of FECD treatment is surgery. However, limited sources of corneal graft and postsurgical complications remain problematic. In recent years, with advances in medical science and technology, there have been a few promising trials of new treatment modalities for FECD. In addition to new surgical methods, novel modalities can be classified into pharmacological-associated treatment, cell therapy-associated treatment, and gene therapy-associated treatment. In this article, our primary focus is on the most recent clinical trials related to FECD, and we present a stepwise approach to enhance FECD management and ultimately improve patient outcomes. We thoroughly searched for FECD clinical trials and reviewed the study designs, methodologies, and outcomes of each trial conducted within the past decade. It is imperative for physicians to stay up-to-date with these cutting-edge treatment approaches.

Effect of Intravitreal Aflibercept on Corneal Endothelial Cells

AIM

To determine the effect of repeated intravitreal injections of aflibercept on the corneal endothelium in patients with diabetic macular edema (DME) and macular edema due to retinal vein occlusion (RVO).

METHODS

In a prospective study conducted between January 2021 and November 2023, a total of 87 treatment-naive eyes with DME and RVO were evaluated. The exclusion criteria were surgery or laser intervention during the follow-up period, contact lens wear, cataract surgery in the last 6 months, dystrophy, or other corneal condition that may cause endothelial damage. In addition to routine examinations on the day of application, we also measured the corneal endothelium using specular microscopy on the 1st, 4th and 8th day of injection. We evaluated 4 parameters: endothelial cell density (CD), hexagonality (HEX), coefficient of variability (CV) and central corneal thickness (CCT). First of all, we evaluated the entire cohort of eyes, and then divided it according to 2 criteria; the diagnosis into DME/RVO and according to the lens status into phakic/pseudophakic eyes.

RESULTS

A total of 87 eyes of 68 patients were evaluated. The average age of the patients at the time of diagnosis was 66.8 ±9.3 years. Within the cohort 51 (59%) eyes were phakic and 36 (41%) pseudophakic. A total of 61 (70%) eyes with a diagnosis of DME were treated, and 26 (30%) with RVO. During the follow-up, there were no significant changes in the average values of CD, HEX, CV, CCT due to aflibercept treatment, either in the whole group or in subgroups according to diagnosis or lens condition.

CONCLUSIONS

The results of this study suggest that intravitreal administration of aflibercept in patients with DME and RVO did not have an impact on corneal endothelial parameters, including CCT, HEX, CD and CV. These parameters were measured using endothelial microscopy during an 8-injection observation period.

Comparison of corneal endothelial cell density and morphology with Optisol GS and Life4C storage media in the eye bank: a 5-year retrospective analysis

Purpose

Optisol GS and Life4C are corneal storage media used by eye banks worldwide. We sought to determine if either solution was associated with superior corneal endothelial cell density (ECD) or morphology in a large cohort of donor corneas.

Methods

From January 2016 through December 2020, 10,316 corneas from 5,624 unique donors were acquired and analyzed at Rocky Mountain Lions Eye Bank. In April 2019, Life4C replaced Optisol GS as the sole storage medium. We compared ECD and morphology before and after April 2019, and excluded corneas processed within the transition period. Univariable and multivariable regression analyses accounted for age, sex, tobacco use, heavy alcohol use, and diabetes. Only right corneas were analyzed to account for the correlation between eyes.

Results

Of 5042 right corneas analyzed, 3486 were stored in Optisol GS and 1556 in Life4C. There was no significant difference in ECD across groups (2794 vs. 2793 cells/mm2 in Optisol GS and Life4C, p=0.88). In multivariate analyses, there was no significant difference in corneal ECD (0.6 cells/mm2 higher with Life4C, p=0.96) or hexagonality (0.22% higher with Life4C, p=0.31). However, the coefficient of variation was significantly lower in the Life4C group (-0.0039, p=0.03). After adjustment for above factors, corneas in Life4C demonstrated a 3.1% decreased likelihood of exhibiting CV values greater than 0.40 (p=0.009).

Conclusions

This study demonstrates comparable and favorable outcomes using both storage media and confirms their overall efficacy. The decreased CV in Life4C is not of clinically significant magnitude, but merits further research in clinical and long-term settings.

The Innovative Biomaterials and Technologies for Developing Corneal Endothelium Tissue Engineering Scaffolds: A Review and Prospect

Corneal transplantation is the only treatment for corneal endothelial blindness. However, there is an urgent need to find substitutes for corneal endothelium grafts due to the global shortage of donor corneas. An emerging research field focuses on the construction of scaffold-based corneal endothelium tissue engineering (CETE). Long-term success in CETE transplantation may be achieved by selecting the appropriate biomaterials as scaffolds of corneal endothelial cells and adding bioactive materials to promote cell activity. This article reviews the research progress of CETE biomaterials in the past 20 years, describes the key characteristics required for corneal endothelial scaffolds, and summarizes the types of materials that have been reported. Based on these, we list feasible improvement strategies for biomaterials innovation. In addition, we describe the improved techniques for the scaffolds' surface topography and drug delivery system. Some promising technologies for constructing CETE are proposed. However, some questions have not been answered yet, and clinical trials and industrialization should be carried out with caution.

Corneal Endothelial-like Cells Derived from Induced Pluripotent Stem Cells for Cell Therapy

Corneal endothelial dysfunction is one of the leading causes of corneal blindness, and the current conventional treatment option is corneal transplantation using a cadaveric donor cornea. However, there is a global shortage of suitable donor graft material, necessitating the exploration of novel therapeutic approaches. A stem cell-based regenerative medicine approach using induced pluripotent stem cells (iPSCs) offers a promising solution, as they possess self-renewal capabilities, can be derived from adult somatic cells, and can be differentiated into all cell types including corneal endothelial cells (CECs). This review discusses the progress and challenges in developing protocols to induce iPSCs into CECs, focusing on the different media formulations used to differentiate iPSCs to neural crest cells (NCCs) and subsequently to CECs, as well as the characterization methods and markers that define iPSC-derived CECs. The hurdles and solutions for the clinical application of iPSC-derived cell therapy are also addressed, including the establishment of protocols that adhere to good manufacturing practice (GMP) guidelines. The potential risks of genetic mutations in iPSC-derived CECs associated with long-term in vitro culture and the danger of potential tumorigenicity following transplantation are evaluated. In all, this review provides insights into the advancement and obstacles of using iPSC in the treatment of corneal endothelial dysfunction.

Transformers in medical imaging: A survey

Following unprecedented success on the natural language tasks, Transformers have been successfully applied to several computer vision problems, achieving state-of-the-art results and prompting researchers to reconsider the supremacy of convolutional neural networks (CNNs) as de facto operators. Capitalizing on these advances in computer vision, the medical imaging field has also witnessed growing interest for Transformers that can capture global context compared to CNNs with local receptive fields. Inspired from this transition, in this survey, we attempt to provide a comprehensive review of the applications of Transformers in medical imaging covering various aspects, ranging from recently proposed architectural designs to unsolved issues. Specifically, we survey the use of Transformers in medical image segmentation, detection, classification, restoration, synthesis, registration, clinical report generation, and other tasks. In particular, for each of these applications, we develop taxonomy, identify application-specific challenges as well as provide insights to solve them, and highlight recent trends. Further, we provide a critical discussion of the field's current state as a whole, including the identification of key challenges, open problems, and outlining promising future directions. We hope this survey will ignite further interest in the community and provide researchers with an up-to-date reference regarding applications of Transformer models in medical imaging. Finally, to cope with the rapid development in this field, we intend to regularly update the relevant latest papers and their open-source implementations at https://github.com/fahadshamshad/awesome-transformers-in-medical-imaging.

Advances in the applications of mesenchymal stem cell-conditioned medium in ocular diseases

Mesenchymal stem cell-conditioned medium (MSC-CM), also known as secretome, is secreted by MSC and contains a variety of bioactive factors with anti-inflammatory, anti-apoptotic, neuroprotection, and proliferation effects. Increasing evidence proved that MSC-CM plays an important role in various diseases, including skin, bone, muscle, and dental diseases. However, the role of MSC-CM in ocular diseases is not quite clear, Therefore, this article reviewed the composition, biological functions, preparation, and characterization of MSC-CM and summarized current research advances in different sources of MSC-CM in corneal and retinal diseases, including dry eye, corneal epithelial damage, chemical corneal injury, retinitis pigmentosa (RP), anterior ischemic optic neuropathy (AION), diabetic retinopathy (DR), and other retinal degenerative changes. For these diseases, MSC-CM can promote cell proliferation, reduce inflammation and vascular leakage, inhibit retinal cell degeneration and apoptosis, protect corneal and retinal structures, and further improves visual function. Hence, we summarize the production, composition and biological functions of MSC-CM and focus on describing its mechanisms in the treatment of ocular diseases. Furthermore, we look at the unexplored mechanisms and further research directions for MSC-CM based therapy in ocular diseases.

A single-cell RNA-seq analysis unravels the heterogeneity of primary cultured human corneal endothelial cells

The cornea is a transparent and avascular tissue located in front of the eye. Its inner surface is lined by a monolayer of corneal endothelial cells (CECs), which maintain the cornea transparency. CECs remain arrested in a non-proliferative state and damage to these cells can compromise their function leading to corneal opacity. The primary culture of donor-derived CECs is a promising cell therapy. It confers the potential to treat multiple patients from a single donor, alleviating the global donor shortage. Nevertheless, this approach has limitations preventing its adoption, particularly culture protocols allow limited expansion of CECs and there is a lack of clear parameters to identify therapy-grade CECs. To address this limitation, a better understanding of the molecular changes arising from the primary culture of CECs is required. Using single-cell RNA sequencing on primary cultured CECs, we identify their variable transcriptomic fingerprint at the single cell level, provide a pseudo-temporal reconstruction of the changes arising from primary culture, and suggest markers to assess the quality of primary CEC cultures. This research depicts a deep transcriptomic understanding of the cellular heterogeneity arising from the primary expansion of CECs and sets the basis for further improvement of culture protocols and therapies.

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.

RNA-Seq-based transcriptome analysis of corneal endothelial cells derived from patients with Fuchs endothelial corneal dystrophy

Fuchs endothelial corneal dystrophy (FECD) is the most common inherited corneal disease. Fibrillar focal excrescences called guttae and corneal edema due to corneal endothelial cell death result in progressive vision loss. Multiple genetic variants have been reported, but the pathogenesis of FECD is not fully understood. In this study, we used RNA-Seq to analyze differential gene expression in the corneal endothelium obtained from patients with FECD. Differential expression analysis of transcriptomic profiles revealed that expression of 2366 genes (1092 upregulated and 1274 downregulated genes) was significantly altered in the corneal endothelium of patients with FECD compared to healthy subjects. Gene ontology analysis demonstrated an enrichment of genes involved in extracellular matrix (ECM) organization, response to oxidative stress, and apoptotic signaling. Several pathway analyses consistently indicated the dysregulation of ECM-associated pathways. Our differential gene expression findings support the previously proposed underlying mechanisms, including oxidative stress and apoptosis of endothelial cells, as well as the phenotypic clinical FECD hallmark of ECM deposits. Further investigation focusing on differentially expressed genes related to these pathways might be beneficial for elucidating mechanisms and developing novel therapies.

Unintentional Descemet Cleft Introduces Novel Mechanism of Maintenance of Corneal Clarity

PURPOSE

The purpose of this study was to report a case of corneal transparency for 7 months after the formation and persistence of a Descemet fluid cleft.

METHODS

We report the case of a 64-year-old woman undergoing anterior chamber reformation 2 months after Baerveldt implantation of the right eye. During the procedure, the ophthalmic viscoelastic was inadvertently injected into the posterior stroma, nearly isolating the corneal endothelial cell layer, and creating a Descemet fluid cleft filled with viscoelastic. The patient was managed conservatively and monitored near monthly for corneal decompensation.

RESULTS

The cornea remained centrally clear for 207 days after the initial anterior chamber reformation until the collapse of the viscoelastic cleft. When the cleft completely collapsed, the cornea became diffusely edematous, and the patient underwent cataract removal and intraocular lens placement without need for Descemet stripping endothelial keratoplasty to maintain vision. During these 7 months, the patient's best-corrected visual acuity remained stable at 20/25 +2 or better. Intraocular pressure was also stable, averaging 18.2 mm Hg.

CONCLUSIONS

We hypothesize that corneal transparency can be maintained in the absence of endothelial cell function provided that aqueous humor cannot reach the cornea and disrupt the arrangement of the interfibrillar space.

iPSC-Derived Corneal Endothelial Cells

The corneal endothelium is the innermost monolayer of the cornea that maintains corneal transparency and thickness. However, adult human corneal endothelial cells (CECs) possess limited proliferative capacity, and injuries can only be repaired by migration and enlargement of resident cells. When corneal endothelial cell density is lower than the critical level (400-500 cells/mm2) due to disease or trauma, corneal endothelial dysfunction will occur and lead to corneal edema. Corneal transplantation remains the most effective clinical treatment therapy but is limited by the global shortage of healthy corneal donors. Recently, researchers have developed several alternative strategies for the treatment of corneal endothelial disease, including the transplantation of cultured human CECs and artificial corneal endothelial replacement. Early-stage results show that these strategies can effectively resolve corneal edema and restore corneal clarity and thickness, but the long-term efficacy and safety remain to be further validated. Induced pluripotent stem cells (iPSCs) represent an ideal cell source for the treatment and drug discovery of corneal endothelial diseases, which can avoid the ethical-related and immune-related problems of human embryonic stem cells (hESCs). At present, many approaches have been developed to induce the differentiation of corneal endothelial-like cells from human induced pluripotent stem cells (hiPSCs). Their safety and efficacy for the treatment of corneal endothelial dysfunction have been confirmed in rabbit and nonhuman primate animal models. Therefore, the iPSC-derived corneal endothelial cell model may provide a novel effective platform for basic and clinical research of disease modeling, drug screening, mechanistic investigation, and toxicology testing.

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.

Nanoneedles Induce Targeted siRNA Silencing of p16 in the Human Corneal Endothelium

Nanoneedles can target nucleic acid transfection to primary cells at tissue interfaces with high efficiency and minimal perturbation. The corneal endothelium is an ideal target for nanoneedle-mediated RNA interference therapy aimed at enhancing its proliferative capacity, necessary for tissue regeneration. This work develops a strategy for siRNA nanoninjection to the human corneal endothelium. Nanoneedles can deliver p16-targeting siRNA to primary human corneal endothelial cells in vitro without toxicity. The nanoinjection of siRNA induces p16 silencing and increases cell proliferation, as monitored by ki67 expression. Furthermore, siRNA nanoinjection targeting the human corneal endothelium is nontoxic ex vivo, and silences p16 in transfected cells. These data indicate that nanoinjection can support targeted RNA interference therapy for the treatment of endothelial corneal dysfunction.

In Vitro Expansion of Corneal Endothelial Cells for Clinical Application: Current Update

ABSTRACT

Endothelial dysfunction is one of the leading causes of corneal blindness and one of the common indications for keratoplasty. At present, the standard of treatment involves the replacement of the dysfunctional endothelium with healthy tissue taken from a donor. Because there is a paucity of healthy donor tissues, research on the corneal endothelium has focused primarily on expanding these cells in the laboratory for transplantation in an attempt to reduce the gap between the demand and supply of donor tissues for transplantation. To expand these cells, which are nonmitotic in vivo, various mitogens, substrates, culture systems, and alternate strategies have been tested with varying success. The biggest challenge has been the limited proliferative capacity of these cells compounded with endothelial to mesenchymal transition that alters the functioning of these cells and renders them unsuitable for human transplantation. This review aims to give a comprehensive overview of the most common and successful techniques used in the culture of the cells, the current available evidence in support of epithelial to mesenchymal transition (EMT), alternate sources for deriving the corneal endothelial cells, and advances made in transplantation of these cells.

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.

Fluctuations in Corneal Endothelial LAP2 Expression Levels Correlate with Passage Dependent Declines in Their Cell Proliferative Activity

The corneal endothelium is the inner corneal mono-layered epithelium, fundamental for preserving corneal hydration and transparency. However, molecular mechanisms that regulate corneal endothelial cells (CEnCs), in particular regarding their proliferative capacity, have been only partially elucidated. CEnCs are quiescent in vivo and they easily undergo endothelial to mesenchymal transition (EnMT) in vitro. This study aims to analyze CEnCs behavior and expression in vitro, either in sub-confluent growing (S) or confluent (C) CEnCs cultures. Primary rabbit and human CEnCs were cultured and used for RT-PCR, immunofluorescence or western blot analysis. These methods allowed identifying a novel molecular marker, LAP2, that is upregulated in S while downregulated in C human or rabbit CEnCs. Those results were observed for several subsequent passages in culture and this, together with the correlation between ki67 and LAP2 expression, suggested LAP2 as a novel possible indicator for culture ageing. Finally, treatment with FGF and TGFβ in rCEnCs highlighted how LAP2 can vary as the cells regulate their proliferative state. In conclusion, we have identified a novel marker for CEnCs, LAP2, that regulates its expression depending on the cells sub/confluent state and that correlates with CEnCs proliferation.

Alternatives to endokeratoplasty: an attempt towards reducing global demand of human donor corneas

The cornea is an anterior transparent tissue of the eye that enables the transmission of surrounding light to the back of the eye, which is essential for maintaining clear vision. Corneal endothelial diseases can lead to partial or total blindness; hence, surgical replacement of the diseased corneal tissue with a healthy cadaveric donor graft becomes necessary when the endothelium is damaged. Keratoplasties face a huge challenge due to a worldwide shortage in the supply of human donor corneas. Hence, alternative solutions such as cell or tissue engineering-based therapies have been investigated for reducing the global demand of donor corneas. This review aims at highlighting studies that have been successful at replacing partial or total endothelial keratoplasty.

Tissue engineered scaffolds for corneal endothelial regeneration: a material's perspective

Currently, the treatment of corneal diseases caused by damage to the corneal endothelium requires a donor cornea. Because of their limited availability (1 donor cornea for 70 patients in need), researchers are investigating alternative approaches that are independent of donor tissue. One of them includes the development of a tissue engineered scaffold onto which corneal endothelial cells are seeded. In order to function as a suitable substrate, some of its essential properties including thickness, permeability, transparency and mechanical strength should meet certain demands. Additionally, the membrane should be biocompatible and allow the formation of a functional endothelium on the surface. Many materials have already been investigated in this regard including natural, semi-synthetic and synthetic polymers. In the current review, we present an overview of their characteristics and provide a critical view on the methods exploited for material characterization. Next, also the suitability of scaffolds to serve their purpose is discussed along with an overview of natural tissues (e.g. amniotic membrane and lens capsule) previously investigated for this application. Eventually, we propose a consistent approach to be exploited ideally for membrane characterization in future research. This will allow a scientifically sound comparison of materials and membranes investigated by different research groups, hence benefitting research towards the creation of a suitable/optimal tissue engineered endothelial graft.

Endothelial cell loss associated with minimally invasive glaucoma surgery

PURPOSE OF REVIEW

Minimally invasive glaucoma surgery (MIGS) represents a safer, albeit moderately effective surgical option for intraocular pressure control. However, the CyPass Micro-Stent (Alcon Laboratories) was withdrawn from the market in 2018 as the COMPASS-XT study demonstrated greater cornea endothelial cell (CEC) loss in patients who received the CyPass Micro-Stent with phacoemulsification compared with phacoemulsification alone. This led to the increased attention on MIGS-associated CEC loss and thus, this review will summarise the recent, available evidence on MIGS-associated CEC loss.

RECENT FINDINGS

Prospective clinical trials and retrospective observational studies published between 2011 and 2021 reported a wide range of 12 month CEC loss from 'insignificant', and up to 14.6%, for phacoemulsification combined with various MIGS procedures. Recent clinical trials over the same time period reported CEC loss of 12.8-15.2% associated with phacoemulsification alone.

SUMMARY

Apart from the CyPass Micro-Stent clinical trial, no other studies on combined phacoemulsification with MIGS that is 'phaco-plus' procedures have reported a higher short-term CEC loss compared with phacoemulsification alone. However, studies that specifically examine postprocedural CEC loss following phacoemulsification compared to 'phaco-plus' procedures over a longer follow-up period are required.

Single cell transcriptomics reveals the heterogeneity of the human cornea to identify novel markers of the limbus and stroma

The cornea is the clear window that lets light into the eye. It is composed of five layers: epithelium, Bowman's layer, stroma, Descemet's membrane and endothelium. The maintenance of its structure and transparency are determined by the functions of the different cell types populating each layer. Attempts to regenerate corneal tissue and understand disease conditions requires knowledge of how cell profiles vary across this heterogeneous tissue. We performed a single cell transcriptomic profiling of 19,472 cells isolated from eight healthy donor corneas. Our analysis delineates the heterogeneity of the corneal layers by identifying cell populations and revealing cell states that contribute in preserving corneal homeostasis. We identified expression of CAV1, HOMER3 and CPVL in the corneal epithelial limbal stem cell niche, CKS2, STMN1 and UBE2C were exclusively expressed in highly proliferative transit amplifying cells, CXCL14 was expressed exclusively in the suprabasal/superficial limbus, and NNMT was exclusively expressed by stromal keratocytes. Overall, this research provides a basis to improve current primary cell expansion protocols, for future profiling of corneal disease states, to help guide pluripotent stem cells into different corneal lineages, and to understand how engineered substrates affect corneal cells to improve regenerative therapies.

Mechanotransductive Differentiation of Hair Follicle Stem Cells Derived from Aged Eyelid Skin into Corneal Endothelial-Like Cells

Corneal endothelial insufficiency is one of the leading causes of blindness. The main contemporary treatment for corneal blindness is endothelial keratoplasty, which, however, is unsatisfactory as a medical therapy due to the lack of donor corneas and graft rejection. Therefore, autologous stem cell-based corneal endothelial tissue substitutes may be a promising alternative to conventional grafts in the future. To address the age of most patients suffering from corneal endothelial deficiencies, we investigated the presence and potential of hair-derived stem cells from older tissue donors. Our studies revealed the presence of pluripotency- and neural crest-associated markers in tissue sections from blepharoplasty patients aged 50 to 80 years. In vitro outgrowths from eyelid hair follicles on collagen-coated tissue culture plates revealed a weak decrease in stem-cell potency. In contrast, cells within the spheres that spontaneously formed from the adherent cell layer retained full stem-cell potency and could be differentiated into cells of the ecto- meso and endodermal lineages. Although these highly potent hair follicle derived stem cells (HFSC) were only very slightly expandable, they were able to recognize the biomimicry of the Descemet’s-like topography and differentiate into corneal endothelial-like cells. In conclusion, HFSCs derived from epidermal skin of eyelid biopsies are a promising cell source to provide autologous corneal endothelial replacement for any age group of patients.

Culture of corneal endothelial cells obtained by descemetorhexis of corneas with Fuchs endothelial corneal dystrophy

Currently, endothelial keratoplasty is the gold standard for the surgical treatment of Fuchs endothelial corneal dystrophy (FECD). Despite the remarkable success in terms of surgical outcomes, a shortage of corneal donor tissue poses a limitation to performing endothelial keratoplasty in many parts of the world. Cell therapy is a potential alternative strategy to keratoplasty and is currently under investigation. Considering that corneas with FECD may contain relatively healthy endothelial cells, samples obtained by descemetorhexis of eyes undergoing EK for FECD can be used for ex vivo expansion of endothelial cells as an autologous cell culture. In this study, we established corneal endothelial cell cultures derived from 40 patients that underwent endothelial keratoplasty for advanced FECD. Several parameters were evaluated including patient characteristics such as age, gender, and endothelial cell density as well as various processing and cell culture protocols based on different combinations of shipping temperatures, stabilization periods and treatment methods for corneal endothelial cell dissociation. FECD cultures were classified into three groups as: (i) no cells, (ii) cell cultures with endothelial-like morphology or (iii) cell cultures with fibroblast-like features. Our data seem to suggest that some factors can influence FECD cell culture characteristics including young age, high paracentral endothelial cell density, low shipping temperature and short stabilization period prior to cell isolation. Treatment with type 1 collagenase for cell isolation can delay endothelial-to-mesenchymal transition, but does not increase proliferative capacity. Although heterologous corneal endothelial cultures from healthy donors have shown encouraging outcomes, the feasibility of autologous cell therapy as a potential treatment for FECD remains challenging. Low initial cell concentration as well as endothelial to mesenchymal transition are the main obstacles to the application of FECD cultures in the clinical setting.

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.

Approaches for corneal endothelium regenerative medicine

The state of the art therapy for treating corneal endothelial disease is transplantation. Advances in the reproducibility and accessibility of surgical techniques are increasing the number of corneal transplants, thereby causing a global deficit of donor corneas and leaving 12.7 million patients with addressable visual impairment. Approaches to regenerate the corneal endothelium offer a solution to the current tissue scarcity and a treatment to those in need. Methods for generating corneal endothelial cells into numbers that could address the current tissue shortage and the possible strategies used to deliver them have now become a therapeutic reality with clinical trials taking place in Japan, Singapore and Mexico. Nevertheless, there is still a long way before such therapies are approved by regulatory bodies and become clinical practice. Moreover, acellular corneal endothelial graft equivalents and certain drugs could provide a treatment option for specific disease conditions without the need of donor tissue or cells. Finally, with the emergence of gene modulation therapies to treat corneal endothelial disease, it would be possible to treat presymptomatic patients or those presenting early symptoms, drastically reducing the need for donor tissue. It is necessary to understand the most recent developments in this rapidly evolving field to know which conditions could be treated with which approach. This article provides an overview of the current and developing regenerative medicine therapies to treat corneal endothelial disease and provides the necessary guidance and understanding towards the treatment of corneal endothelial disease.

Molecular Hydrogen Attenuated N-methyl-N-Nitrosourea Induced Corneal Endothelial Injury by Upregulating Anti-Apoptotic Pathway

Purpose

Previous work by our group has demonstrated the value of N-methyl-N-nitrosourea (MNU)-induced corneal endothelial decompensation in animal models. The aim of this study was to investigate the effect of molecular hydrogen (H2) on MNU-induced corneal endothelial cell (CEC) injury and the underlying mechanism.

Methods

MNU-induced animal models of CEC injury were washed with hydrogen-rich saline (HRS) for 14 days. Immunofluorescence staining, immunohistochemical staining, and corneal endothelial assessment were applied to determine architectural and cellular changes on the corneal endothelium following HRS treatment. MNU-induced cell models of CEC injury were co-cultured with H2. The effect of H2 was examined using morphological and functional assays.

Results

It was shown that MNU could inhibit the proliferation and specific physiological functions of CECs by increasing apoptosis and decreasing the expression of ZO-1 and Na+/K+-ATPase, whereas H2 improved the proliferation and physiological function of CECs by anti-apoptosis. Cell experiments further confirmed that H2 could reverse MNU damage to CECs by decreasing oxidative stress injury, interfering with the NF-κB/NLRP3 pathway and the FOXO3a/p53/p21 pathway.

Conclusions

This study suggests that topical application of H2 could protect CECs against corneal damage factors through anti-apoptotic effect, reduce the incidence and severity of corneal endothelial decompensation, and maintain corneal transparency.

Proliferation Increasing Genetic Engineering in Human Corneal Endothelial Cells: A Literature Review

The corneal endothelium is the inner layer of the cornea. Despite comprising only a monolayer of cells, dysfunction of this layer renders millions of people visually impaired worldwide. Currently, corneal endothelial transplantation is the only viable means of restoring vision for these patients. However, because the supply of corneal endothelial grafts does not meet the demand, many patients remain on waiting lists, or are not treated at all. Possible alternative treatment strategies include intracameral injection of human corneal endothelial cells (HCEnCs), biomedical engineering of endothelial grafts and increasing the HCEnC density on grafts that would otherwise have been unsuitable for transplantation. Unfortunately, the limited proliferative capacity of HCEnCs proves to be a major bottleneck to make these alternatives beneficial. To tackle this constraint, proliferation enhancing genetic engineering is being investigated. This review presents the diverse array of genes that have been targeted by different genetic engineering strategies to increase the proliferative capacity of HCEnCs and their relevance for clinical and research applications. Together these proliferation-related genes form the basis to obtain a stable and safe supply of HCEnCs that can tackle the corneal endothelial donor shortage.

Transplantation of human induced pluripotent stem cell-derived neural crest cells for corneal endothelial regeneration

BACKGROUND

The corneal endothelium maintains corneal hydration through the barrier and pump function, while its dysfunction may cause corneal edema and vision reduction. Considering its development from neural crest cells (NCCs), here we investigated the efficacy of the human induced pluripotent stem cell (hiPSC)-derived NCCs for corneal endothelial regeneration in rabbits.

METHODS

Directed differentiation of hiPSC-derived NCCs was achieved using the chemically defined medium containing GSK-3 inhibitor and TGF-β inhibitor. The differentiated cells were characterized by immunofluorescence staining, FACS analysis, and in vitro multi-lineage differentiation capacity. For in vivo functional evaluation, 1.0 × 106 hiPSC-derived NCCs or NIH-3 T3 fibroblasts (as control) combined with 100 μM Y-27632 were intracamerally injected into the anterior chamber of rabbits following removal of corneal endothelium. Rabbit corneal thickness and phenotype changes of the transplanted cells were examined at 7 and 14 days with handy pachymeter, dual-immunofluorescence staining, and quantitative RT-PCR.

RESULTS

The hiPSC-derived NCCs were differentiated homogenously through 7 days of induction and exhibited multi-lineage differentiation capacity into peripheral neurons, mesenchymal stem cells, and corneal keratocytes. After 7 days of intracameral injection in rabbit, the hiPSC-derived NCCs led to a gradual recovery of normal corneal thickness and clarity, when comparing to control rabbit with fibroblasts injection. However, the recovery efficacy after 14 days deteriorated and caused the reappearance of corneal edema. Mechanistically, the transplanted cells exhibited the impaired maturation, cellular senescence, and endothelial-mesenchymal transition (EnMT) after the early stage of the in vivo directional differentiation.

CONCLUSIONS

Transplantation of the hiPSC-derived NCCs rapidly restored rabbit corneal thickness and clarity. However, the long-term recovery efficacy was impaired by the improper maturation, senescence, and EnMT of the transplanted cells.

In vitro reconstructed 3D corneal tissue models for ocular toxicology and ophthalmic drug development

Testing of all manufactured products and their ingredients for eye irritation is a regulatory requirement. In the last two decades, the development of alternatives to the in vivo Draize eye irritation test method has substantially advanced due to the improvements in primary cell isolation, cell culture techniques, and media, which have led to improved in vitro corneal tissue models and test methods. Most in vitro models for ocular toxicology attempt to reproduce the corneal epithelial tissue which consists of 4-5 layers of non-keratinized corneal epithelial cells that form tight junctions, thereby limiting the penetration of chemicals, xenobiotics, and pharmaceuticals. Also, significant efforts have been directed toward the development of more complex three-dimensional (3D) equivalents to study wound healing, drug permeation, and bioavailability. This review focuses on in vitro reconstructed 3D corneal tissue models and their utilization in ocular toxicology as well as their application to pharmacology and ophthalmic research. Current human 3D corneal epithelial cell culture models have replaced in vivo animal eye irritation tests for many applications, and substantial validation efforts are in progress to verify and approve alternative eye irritation tests for widespread use. The validation of drug absorption models and further development of models and test methods for many ophthalmic and ocular disease applications is required.

Transcriptome dataset of human corneal endothelium based on ribosomal RNA-depleted RNA-Seq data

The corneal endothelium maintains corneal transparency; consequently, damage to this endothelium by a number of pathological conditions results in severe vision loss. Publicly available expression databases of human tissues are useful for investigating the pathogenesis of diseases and for developing new therapeutic modalities; however, databases for ocular tissues, and especially the corneal endothelium, are poor. Here, we have generated a transcriptome dataset from the ribosomal RNA-depleted total RNA from the corneal endothelium of eyes from seven Caucasians without ocular diseases. The results of principal component analysis and correlation coefficients (ranged from 0.87 to 0.96) suggested high homogeneity of our RNA-Seq dataset among the samples, as well as sufficient amount and quality. The expression profile of tissue-specific marker genes indicated only limited, if any, contamination by other layers of the cornea, while the Smirnov-Grubbs test confirmed the absence of outlier samples. The dataset presented here should be useful for investigating the function/dysfunction of the cornea, as well as for extended transcriptome analyses integrated with expression data for non-coding RNAs.

Measurement(s)	RNA
Technology Type(s)	RNA sequencing
Factor Type(s)	sex
Sample Characteristic - Organism	Homo sapiens

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.13186868

Designer Descemet Membranes Containing PDLLA and Functionalized Gelatins as Corneal Endothelial Scaffold

Corneal blindness is the fourth leading cause of visual impairment. Of specific interest is blindness due to a dysfunctional corneal endothelium which can only be treated by transplanting healthy tissue from a deceased donor. Unfortunately, corneal supply does not meet the demand with only one donor for every 70 patients. Therefore, there is a huge interest in tissue engineering of grafts consisting of an ultra-thin scaffold seeded with cultured endothelial cells. The present research describes the fabrication of such artificial Descemet membranes based on the combination of a biodegradable amorphous polyester (poly (d,l-lactic acid)) and crosslinkable gelatins. Four different crosslinkable gelatin derivatives are compared in terms of processing, membrane quality, and function, as well as biological performance in the presence of corneal endothelial cells. The membranes are fabricated through multi-step spincoating, including a sacrificial layer to allow for straightforward membrane detachment after production. As a consequence, ultrathin (<1 µm), highly transparent (>90%), semi-permeable membranes could be obtained with high biological potential. The membranes supported the characteristic morphology and correct phenotype of corneal endothelial cells while exhibiting similar proliferation rates as the positive control. As a consequence, the proposed membranes prove to be a promising synthetic alternative to donor tissue.