Diseases of the corneal endothelium

Artificial Endothelial Layer Implantation After Multiple Failed Keratoplasties

PURPOSE

Presenting the first case of noncellular corneal endothelial substitute after multiple failed penetrating keratoplasty (PK) and lamellar endothelial keratoplasty.

METHODS

Our case presented with pseudophakic bullous keratopathy after a history of 2 rejected PKs and 1 rejected Descemet stripping automated endothelial keratoplasty. We implanted an artificial endothelial layer.

RESULTS

The implant remained fully attached for a follow-up period of 12 months, and central corneal thickness decreased significantly. The patient reported improvement in her subjective vision, although ocular comorbidities limited the visual potential.

CONCLUSIONS

This new device could serve as an alternative to lamellar endothelial corneal transplantation in cases where tissue rejection has occurred and is highly likely to recur. The technique is simple, and the deswelling effect on the cornea persisted, although the visual results require further validation in patients with a higher visual potential.

Methylation in cornea and corneal diseases: a systematic review

Corneal diseases are among the primary causes of blindness and vision loss worldwide. However, the pathogenesis of corneal diseases remains elusive, and diagnostic and therapeutic tools are limited. Thus, identifying new targets for the diagnosis and treatment of corneal diseases has gained great interest. Methylation, a type of epigenetic modification, modulates various cellular processes at both nucleic acid and protein levels. Growing evidence shows that methylation is a key regulator in the pathogenesis of corneal diseases, including inflammation, fibrosis, and neovascularization, making it an attractive potential therapeutic target. In this review, we discuss the major alterations of methylation and demethylation at the DNA, RNA, and protein levels in corneal diseases and how these dynamics contribute to the pathogenesis of corneal diseases. Also, we provide insights into identifying potential biomarkers of methylation that may improve the diagnosis and treatment of corneal diseases.

Nanoparticle-Mediated Cell Delivery: Advancements in Corneal Endothelial Regeneration

Corneal endothelial dysfunction poses significant challenges in ophthalmology, leading to corneal edema and vision loss. Traditional treatments, including corneal transplantation, are limited by donor scarcity and potential complications. Nanoparticle-mediated cell delivery emerges as a promising approach for corneal endothelial regeneration, offering targeted and minimally invasive solutions. This comprehensive review provides insights into the role of nanoparticles in enhancing cell survival, integration, and therapeutic efficacy. We discuss the current understanding of corneal endothelial dysfunction, emphasizing the importance of regeneration. Furthermore, we explore the potential implications of nanoparticle-mediated approaches in clinical practice, highlighting opportunities for personalized treatment strategies. Future directions are also discussed, including optimization of nanoparticle design and exploration of combination therapies. Overall, this review elucidates the promising advancements in nanoparticle-mediated cell delivery for corneal endothelial regeneration and underscores the importance of continued research efforts in this evolving field.

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.

EZH2 Promotes Corneal Endothelial Cell Apoptosis by Mediating H3K27me3 and Inhibiting HO-1 Transcription

PURPOSE

This paper aims to explore the molecular mechanism of Enhancer of Zeste Homolog 2 (EZH2)-mediated H3K27me3 in human corneal endothelial cells (HCEC) apoptosis by inhibiting Heme oxygenase-1 (HO-1) transcription to provide a potential target for the treatment of corneal apoptosis.

METHODS

HCECs were cultured in vitro and transfected with si-EZH2, pcDNA3.1-EZH2, pcDNA3.1-HO-1, GSK-J4 (an effective H3K27me3 demethylase inhibitor), and corresponding controls. Western Blot assay was used to detect the levels of EZH2, HO-1, H3K27me3, and apoptosis-related proteins (Bcl-2, Bax, and Cleaved-caspase-3) in HCECs; CCK-8 assay was conducted to detect cell viability and flow cytometry to analyze the apoptosis. HO-1 mRNA levels were detected by RT-qPCR and changes in H3K27me3 levels on the HO-1 promoter were detected by chromatin immunoprecipitation.

RESULTS

HCECs transfected with si-EZH2 showed significantly lower EZH2 mRNA and protein levels, higher HCEC viability, lower apoptosis rates, higher antiapoptotic protein Bcl-2 expression, lower proapoptotic protein (Bax and Cleaved-caspase-3) levels, and significantly higher HO-1 expression. HCECs transfected with pcDNA3.1-EZH2 showed the opposite results. EZH2 repressed HO-1 transcription by mediating H3K27me3. H3K27me27 was enriched in the HO-1 promoter and overexpression of EZH2 increased H3K27me27 levels. Promotion of H3K27me3 partially reversed the mitigating effect of si-EZH2 on HCEC apoptosis. Overexpression of HO-1 partially reversed the apoptosis-promoting effects of EZH2 and H3K27me3 on HCECs.

CONCLUSIONS

EZH2 promotes HCE cell apoptosis by mediating H3K27me3 to inhibit HO-1 transcription.

Corneal Edema after Cataract Surgery

This systematic review investigates the prevalence and underlying causes of corneal edema following cataract surgery employing manual phacoemulsification. A comprehensive search encompassing databases such as PubMed, Embase, ProQuest, Cochrane Library, and Scopus was conducted, focusing on variables encompassing cataract surgery and corneal edema. Two independent reviewers systematically extracted pertinent data from 103 articles, consisting of 62 theoretical studies and 41 clinical trials. These studies delved into various aspects related to corneal edema after cataract surgery, including endothelial cell loss, pachymetry measurements, visual performance, surgical techniques, supplies, medications, and assessments of endothelial and epithelial barriers. This review, encompassing an extensive analysis of 3060 records, revealed significant correlations between corneal edema and endothelial cell loss during phacoemulsification surgery. Factors such as patient age, cataract grade, and mechanical stress were identified as contributors to endothelial cell loss. Furthermore, pachymetry and optical coherence tomography emerged as valuable diagnostic tools for assessing corneal edema. In conclusion, this systematic review underscores the link between corneal edema and endothelial cell loss in manual phacoemulsification cataract surgery. It highlights the relevance of factors like patient demographics and diagnostic modalities. However, further research is essential to unravel the complexities of refractive changes and the underlying mechanisms.

TFOS Lifestyle: Impact of contact lenses on the ocular surface

Several lifestyle choices made by contact lens wearers can have adverse consequences on ocular health. These include being non-adherent to contact lens care, sleeping in lenses, ill-advised purchasing options, not seeing an eyecare professional for regular aftercare visits, wearing lenses when feeling unwell, wearing lenses too soon after various forms of ophthalmic surgery, and wearing lenses when engaged in risky behaviors (e.g., when using tobacco, alcohol or recreational drugs). Those with a pre-existing compromised ocular surface may find that contact lens wear exacerbates ocular disease morbidity. Conversely, contact lenses may have various therapeutic benefits. The coronavirus disease-2019 (COVID-19) pandemic impinged upon the lifestyle of contact lens wearers, introducing challenges such as mask-associated dry eye, contact lens discomfort with increased use of digital devices, inadvertent exposure to hand sanitizers, and reduced use of lenses. Wearing contact lenses in challenging environments, such as in the presence of dust and noxious chemicals, or where there is the possibility of ocular trauma (e.g., sport or working with tools) can be problematic, although in some instances lenses can be protective. Contact lenses can be worn for sport, theatre, at high altitude, driving at night, in the military and in space, and special considerations are required when prescribing in such situations to ensure successful outcomes. A systematic review and meta-analysis, incorporated within the review, identified that the influence of lifestyle factors on soft contact lens dropout remains poorly understood, and is an area in need of further research. Overall, this report investigated lifestyle-related choices made by clinicians and contact lens wearers and discovered that when appropriate lifestyle choices are made, contact lens wear can enhance the quality of life of wearers.

Systematic review of SLC4A11, ZEB1, LOXHD1, and AGBL1 variants in the development of Fuchs' endothelial corneal dystrophy

Introduction

The pathogenic role of variants in TCF4 and COL8A2 in causing Fuchs' endothelial corneal dystrophy (FECD) is not controversial and has been confirmed by numerous studies. The causal role of other genes, SLC4A11, ZEB1, LOXHD1, and AGBL1, which have been reported to be associated with FECD, is more complicated and less obvious. We performed a systematic review of the variants in the above-mentioned genes in FECD cases, taking into account the currently available population frequency information, transcriptomic data, and the results of functional studies to assess their pathogenicity.

Methods

Search for articles published in 2005-2022 was performed manually between July 2022 and February 2023. We searched for original research articles in peer-reviewed journals, written in English. Variants in the genes of interest identified in patients with FECD were extracted for the analysis. We classified each presented variant by pathogenicity status according to the ACMG criteria implemented in the Varsome tool. Diagnosis, segregation data, presence of affected relatives, functional analysis results, and gene expression in the corneal endothelium were taken into account. Data on the expression of genes of interest in the corneal endothelium were extracted from articles in which transcriptome analysis was performed. The identification of at least one variant in a gene classified as pathogenic or significantly associated with FECD was required to confirm the causal role of the gene in FECD.

Results

The analysis included 34 articles with 102 unique ZEB1 variants, 20 articles with 64 SLC4A11 variants, six articles with 26 LOXHD1 variants, and five articles with four AGBL1 variants. Pathogenic status was confirmed for seven SLC4A11 variants found in FECD. No variants in ZEB1, LOXHD1, and AGBL1 genes were classified as pathogenic for FECD. According to the transcriptome data, AGBL1 and LOXHD1 were not expressed in the corneal endothelium. Functional evidence for the association of LOXHD1, and AGBL1 with FECD was conflicting.

Conclusion

Our analysis confirmed the causal role of SLC4A11 variants in the development of FECD. The causal role of ZEB1, LOXHD1, and AGBL1 variants in FECD has not been confirmed. Further evidence from familial cases and functional analysis is needed to confirm their causal roles in FECD.

From bench to clinic: Emerging therapies for corneal scarring

Corneal diseases are one of the leading causes of moderate-to-severe visual impairment and blindness worldwide, after glaucoma, cataract, and retinal disease in overall importance. Given its tendency to affect people at a younger age than other blinding conditions such as cataract and glaucoma, corneal scarring poses a huge burden both on the individuals and society. Furthermore, corneal scarring and fibrosis disproportionately affects people in poorer and remote areas, making it a significant ophthalmic public health problem. Traditional medical strategies, such as topical corticosteroids, are not effective in preventing fibrosis or scars. Corneal transplantation, the only effective sight-restoring treatment for corneal scars, is curbed by challenges including a severe shortage of tissue, graft rejection, secondary conditions, cultural barriers, the lack of well-trained surgeons, operating rooms, and well-equipped infrastructures. Thanks to tremendous research efforts, emerging therapeutic options including gene therapy, protein therapy, cell therapy and novel molecules are in development to prevent the progression of corneal scarring and compliment the surgical options currently available for treating established corneal scars in clinics. In this article, we summarise the most relevant preclinical and clinical studies on emerging therapies for corneal scarring in recent years, showing how these approaches may prevent scarring in its early development.

Identification and in silico analysis of a spectrum of SLC4A11 variations in Indian familial and sporadic cases of congenital hereditary endothelial dystrophy

Background

Congenital hereditary endothelial dystrophy (CHED) is a rare form of corneal dystrophy caused by SLC4A11 gene variations. This study aims to find the genetic alterations in SLC4A11, in two Indian familial CHED cases with affected members n = 3 and n = 2 respectively and five sporadic CHED cases using direct sequencing, followed by in silico analysis and characterization of the identified variants.

Results

All three affected members of the first CHED family were identified with a novel homozygous c.1514C > G (p.Ser489Trp) variation while second family showed presence of a compound heterozygous variation c.529A > C (p.Arg161Arg) + c.2461insT (p.Val805fs). Among five sporadic cases, two showed novel changes, homozygous c.1487G > T (p.Ser480Ile) and c.620-2A > G, while the other one had previously reported homozygous c.2653C > T (p.Arg869Cys) variation. The remaining two cases did not reveal the presence of SLC4A11-related pathogenic variations. The identified variations were excluded from the Indian control (n = 80). In silico analysis using homology-based protein modeling and pathogenicity prediction tools, which revealed these alterations as pathogenic, changing their protein stability, local flexibility, residue contact clashes, and the hydrogen bond interactions.

Conclusions

This study contributed to the CHED mutational spectrum, adding four novel variations and confirming a previously reported one. It demonstrates different type of variations in CHED cases, including coding, non-coding, homozygous, synonymous, and compound heterozygous variations. The identified variations revealed different degrees of pathogenic effects in silico. Moreover, two sporadic cases could not be identified with pathogenic variation emphasizing the involvement of other genes or genetic mechanisms.

The impact of sensory neuropathy and inflammation on epithelial wound healing in diabetic corneas

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes, with several underlying pathophysiological mechanisms, some of which are still uncertain. The cornea is an avascular tissue and sensitive to hyperglycemia, resulting in several diabetic corneal complications including delayed epithelial wound healing, recurrent erosions, neuropathy, loss of sensitivity, and tear film changes. The manifestation of DPN in the cornea is referred to as diabetic neurotrophic keratopathy (DNK). Recent studies have revealed that disturbed epithelial-neural-immune cell interactions are a major cause of DNK. The epithelium is supplied by a dense network of sensory nerve endings and dendritic cell processes, and it secretes growth/neurotrophic factors and cytokines to nourish these neighboring cells. In turn, sensory nerve endings release neuropeptides to suppress inflammation and promote epithelial wound healing, while resident immune cells provide neurotrophic and growth factors to support neuronal and epithelial cells, respectively. Diabetes greatly perturbs these interdependencies, resulting in suppressed epithelial proliferation, sensory neuropathy, and a decreased density of dendritic cells. Clinically, this results in a markedly delayed wound healing and impaired sensory nerve regeneration in response to insult and injury. Current treatments for DPN and DNK largely focus on managing the severe complications of the disease. Cell-based therapies hold promise for providing more effective treatment for diabetic keratopathy and corneal ulcers.

Corneal Endothelial Characteristics in Normal Chinese Han Children and Youngsters: A Study from the Specular Microscopy Descriptions

Objective

To observe the morphological changes of corneal endothelial cells in healthy Chinese children and youngsters and analyze the sensitive and specificity of the endothelial assessments.

Methods

14,670 Chinese healthy volunteers enrolled were examined by specular microscopy, and the endothelial descriptive indexes: the central corneal thickness (CCT), endothelial cell density (ECD), coefficient of variation in average cell size (CV), the percentage of regular hexagonal cells (hexagonality, HEX), cell size of minimal cell (S_min), cell size of maximal cell (S_max), average cell size (S_avg), and size of standard deviation of cell area (S_sd) as well as sex and age were analyzed.

Results

The average age of this study is 17.36 ± 7.58 (4–30) years. There is no sex predominance: 7,260 male (49.5%) and 7,410 female (50.5%). The mean CCT, ECD, CV, HEX, S_min/max, S_avg, and S_sd are 529.94 ± 31.53 (437–644) μm, 3,051.28 ± 375.49 (2,031–4,074) cells/mm², 28.34 ± 4.36 (18–40) %, 61.21 ± 10.29 (17–89) %, (147.79 ± 21.94 to 678.29 ± 120.96) μm², 332.74 ± 44.62 μm², and 95.02 ± 23.17 μm², respectively. The CCTs keep consistency. The ECD decreased rate is 1.02%/year. The curve of ECD and hexagonality expresses the same linear tender. The CCT and endothelial evaluation indexes have no sex predominant (p > 0.05); the quantitative indicators: CCT, ECD, and HEX are significant negative associated with age (p = 0.001 or p < 0.001); the variability indexes: the CV, S_min, S_max, S_avg, and S_sd are positive correlation (p < 0.001). The coefficients of CCT, HE, and S_min are -0.35, -0.59, and 1.17, respectively.

Conclusions

The ECD decrease rate is 1.02%/year of the normal Chinese Han childhood to the earlier adulthood. The ages 4 to 12, 13 to 20, and 21 to 30 can be named as the childhood, puberty and adulthood from endothelial biologic identity. The HEX is the sensitivity marks for the polymorphisms while the S _min is the specificity indicator CVs upon the Topcon Noncon Specular microscopy results.

Corneal Response to Scleral Contact Lens Wear in Keratoconus

OBJECTIVE

To verify corneal alterations in patients with keratoconus who wear scleral contact lenses (ScCLs), focusing on corneal endothelial assessment.

METHODS

Scleral contact lenses were fitted in 22 patients with keratoconus. During a 90-day follow-up, patients were assessed in three visits: at baseline, after 30 days, and after 90 days. Patients underwent visual acuity measurement, slitlamp biomicroscopy of the anterior segment, specular microscopy of the corneal endothelium, corneal pachymetry, measurement of the clearance between the cornea and the lens, and follow-up of ectasia.

RESULTS

Variables related to endothelial morphology and pachymetry values did not change significantly over time. Central clearance measurements decreased in the 90-day period. No progression of corneal ectasia was observed, neither were infectious or inflammatory processes in the same period.

CONCLUSION

Daily wear of ScCLs in patients with keratoconus was not associated with adverse effects on the cornea or endothelium over a period of 90 days nor was there evidence of disease progression. Central clearance values diminished over that period, but the significance of this observation remains unclear.

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.

CHIR99021 balance TGFβ1 induced human corneal endothelial-to-mesenchymal transition to favor corneal endothelial cell proliferation

Corneal endothelial cells (CECs) play a major role in the maintenance of stromal hydration via the barrier and pump function for clear vision. Adult CEC cannot regenerate after injury. CECs cultured in vitro can undergo mitosis but may undergo corneal endothelial-to-mesenchymal transition (EnMT) and lose their endothelial characteristics. In this study, we examined the effects of CHIR99201 on transforming growth factor beta-1(TGFβ1)-induced EnMT in human CEC (hCECs) lines. CHIR99021 kept hCECs in the hexagonal shape and could downregulate the EnMT markers alpha-smooth muscle actin (α-SMA) and fibronectin (FN1), meanwhile maintained the hCECs function markers Na⁺/K⁺-ATPase and zonula occludens-1 (ZO-1) at levels comparable to those in the normal control. Interestingly, we found that the combination of CHIR99021 and TGFβ1 at appropriate concentrations would significantly promote the proliferation and migration of hCECs. These effects may be related to the inhibition of RhoA or Rac1, as well as the activation of Wnt and Erk pathway, with a calcium homeostasis. Our findings indicate that CHIR99021 inhibit EnMT and that the combination of CHIR99021 and TGFβ1 may provide new ideas for corneal endothelial regeneration and wound healing.

The effects of acute angle closure crisis on corneal endothelial cells in patients with type 2 diabetes mellitus

OBJECTIVE

This study investigated the effects of acute angle closure crisis (AACC) on the corneal endothelial cells in patients with type 2 diabetes mellitus (DM) to identify the factors that cause corneal endothelial cell injury.

METHODS

We examined 154 patients who visited Qingdao Eye Hospital for AACC in one eye (154 eyes; 28 men and 126 women; mean age of 68 ± 8 years). We divided the participants into non-DM, DM well-control, and DM poor-control groups, with the unaffected eyes used as controls. Each participant was evaluated at the hospital while under AACC. We measured the relevant index and corneal parameters of the participants for statistical analysis.

RESULTS

There were significant statistical differences in corneal parameters among the three groups. The decreased levels of central endothelial cell density (CD) and the percentage of hexagonal cells (6A) were statistically relevant among the groups (P<0.05). The AACC duration was correlated with CD loss rate among the groups (P<0.05). The DM duration was correlated with CD loss rate in the DM well-control group. Compared with the non-DM group, the level of 6A decreased more significantly in the DM group after AACC (P<0.05). The AACC duration in the DM well-control group was significantly shorter than in the non-DM and DM poor-control groups (P<0.001). The DM poor-control group showed significantly worse visual acuity when compared with the other groups (P<0.05).

CONCLUSIONS

DM may impact the functional status of corneal endothelial cells. AACC can worsen the corneal endothelium damage in patients with DM. Blood glucose levels and the duration of intraocular hypertension are closely related to the severity of corneal endothelial injury.

Therapeutic contact lens for Fuchs endothelial corneal dystrophy: Monitoring with Scheimpflug tomopraphy

Purpose

This case report demonstrates the effectiveness of a combined unique soft contact lens design and hypertonic saline at reducing corneal edema symptoms. In addition, this case shows that using tomographic data is invaluable for detecting and monitoring of these presentations.

Observations

A 61 year old patient diagnosed with Fuchs endothelial corneal dystrophy (FECD) presented with complaints over the past year of intermittent blurry, foggy vision upon awakening and glare while driving. Slit lamp examination showed no signs of corneal edema. Data acquired from the Scheimpflug tomographer revealed subclinical signs, including increased corneal thickness, displacement of the thinnest point of the cornea, focal posterior depression, elevated densinometry, "camel's back" sign, irregular isopachs, and a plane slope of pachymetry progression in both eyes. The patient was fit with Therapeutic Hyper-CL™ soft contact lenses for eight days extended wear and instilled 5% sodium chloride six times a day. Visual acuity improved in the right and left eye from 0.5(-2) and 0.5(+1) to 0.4(+2) and 0.3(-1), respectively. Corneal thickness at the thinnest point decreased from 650μm to 632μm-632μm and 604μm in the right and left eye respectively and a significant decrease in total densinometry was noted from 34.7 to 33.8 standardized grayscale units (GSU) to 23.1 and 24 GSU, in the right and left eye respectively. The patient reported a decrease in symptoms and his 8-item Contact Lens Dry Eye Questionnaire (CLDEQ-8) score was 19 after treatment.

Conclusions and importance

Treatment for one week with Therapeutic Hyper-CL™ soft contact lenses combined with 5% sodium chloride decreased corneal edema signs and symptoms. Tomographic data facilitated diagnosis and monitoring of improvement.