Chlorine-Induced Toxicity on Murine Cornea: Exploring the Potential Therapeutic Role of Antioxidants

Chlorine (Cl2) exposure poses a significant risk to ocular health, with the cornea being particularly susceptible to its corrosive effects. Antioxidants, known for their ability to neutralize reactive oxygen species (ROS) and alleviate oxidative stress, were explored as potential therapeutic agents to counteract chlorine-induced damage. In vitro experiments using human corneal epithelial cells showed decreased cell viability by chlorine-induced ROS production, which was reversed by antioxidant incubation. The mitochondrial membrane potential decreased due to both low and high doses of Cl2 exposure; however, it was recovered through antioxidants. The wound scratch assay showed that antioxidants mitigated impaired wound healing after Cl2 exposure. In vivo and ex vivo, after Cl2 exposure, increased corneal fluorescein staining indicates damaged corneal epithelial and stromal layers of mice cornea. Likewise, Cl2 exposure in human ex vivo corneas led to corneal injury characterized by epithelial fluorescein staining and epithelial erosion. However, antioxidants protected Cl2-induced damage. These results highlight the effects of Cl2 on corneal cells using in vitro, ex vivo, and in vivo models while also underscoring the potential of antioxidants, such as vitamin A, vitamin C, resveratrol, and melatonin, as protective agents against acute chlorine toxicity-induced corneal injury. Further investigation is needed to confirm the antioxidants' capacity to alleviate oxidative stress and enhance the corneal healing process.

Integrating a Fundus Camera with High-Frequency Ultrasound for Precise Ocular Lesion Assessment

Ultrasound A-scan is an important tool for quantitative assessment of ocular lesions. However, its usability is limited by the difficulty of accurately localizing the ultrasound probe to a lesion of interest. In this study, a transparent LiNbO3 single crystal ultrasound transducer was fabricated, and integrated with a widefield fundus camera to guide the ultrasound local position. The electrical impedance, phase spectrum, pulse-echo performance, and optical transmission spectrum of the ultrasound transducer were validated. The novel fundus camera-guided ultrasound probe was tested for in vivo measurement of rat eyes. Anterior and posterior segments of the rat eye could be unambiguously differentiated with the fundus photography-guided ultrasound measurement. A model eye was also used to verify the imaging performance of the prototype device in the human eye. The prototype shows the potential of being used in the clinic to accurately measure the thickness and echogenicity of ocular lesions in vivo.

Cell Type-Specific Extracellular Vesicles and Their Impact on Health and Disease

Extracellular vesicles (EVs), a diverse group of cell-derived exocytosed particles, are pivotal in mediating intercellular communication due to their ability to selectively transfer biomolecules to specific cell types. EVs, composed of proteins, nucleic acids, and lipids, are taken up by cells to affect a variety of signaling cascades. Research in the field has primarily focused on stem cell-derived EVs, with a particular focus on mesenchymal stem cells, for their potential therapeutic benefits. Recently, tissue-specific EVs or cell type-specific extracellular vesicles (CTS-EVs), have garnered attention for their unique biogenesis and molecular composition because they enable highly targeted cell-specific communication. Various studies have outlined the roles that CTS-EVs play in the signaling for physiological function and the maintenance of homeostasis, including immune modulation, tissue regeneration, and organ development. These properties are also exploited for disease propagation, such as in cancer, neurological disorders, infectious diseases, autoimmune conditions, and more. The insights gained from analyzing CTS-EVs in different biological roles not only enhance our understanding of intercellular signaling and disease pathogenesis but also open new avenues for innovative diagnostic biomarkers and therapeutic targets for a wide spectrum of medical conditions. This review comprehensively outlines the current understanding of CTS-EV origins, function within normal physiology, and implications in diseased states.

All about traumatic cataracts; Narrative review

Ocular trauma is an important cause of monocular blindness worldwide. Injury to the lens after blunt or penetrating trauma is common and can result in vision impairment. Selecting the most appropriate therapeutic approaches depend on factors such as the patients' age, mechanism of trauma, and underlying clinical conditions. Early management, especially within childhood, is essential due to the difficulties involved in examination, anatomical variations, as well as accompanying intraocular inflammation, amblyopia, or vitreoretinal adhesions. The objective of this paper is to provide a comprehensive review of the epidemiology and clinical management of traumatic cataract, highlighting the significance of accurate diagnosis and the selection of the optimal therapeutic approach.

Hydrogel-Based Skin Regeneration

The skin is subject to damage from the surrounding environment. The repair of skin wounds can be very challenging due to several factors such as severe injuries, concomitant infections, or comorbidities such as diabetes. Different drugs and wound dressings have been used to treat skin wounds. Tissue engineering, a novel therapeutic approach, revolutionized the treatment and regeneration of challenging tissue damage. This field includes the use of synthetic and natural biomaterials that support the growth of tissues or organs outside the body. Accordingly, the demand for polymer-based therapeutic strategies for skin tissue defects is significantly increasing. Among the various 3D scaffolds used in tissue engineering, hydrogel scaffolds have gained special significance due to their unique properties such as natural mimicry of the extracellular matrix (ECM), moisture retention, porosity, biocompatibility, biodegradability, and biocompatibility properties. First, this article delineates the process of wound healing and conventional methods of treating wounds. It then presents an examination of the structure and manufacturing methods of hydrogels, followed by an analysis of their crucial characteristics in healing skin wounds and the most recent advancements in using hydrogel dressings for this purpose. Finally, it discusses the potential future advancements in hydrogel materials within the realm of wound healing.

From the diagnosis of infectious keratitis to discriminating fungal subtypes; a deep learning-based study

Infectious keratitis (IK) is a major cause of corneal opacity. IK can be caused by a variety of microorganisms. Typically, fungal ulcers carry the worst prognosis. Fungal cases can be subdivided into filamentous and yeasts, which shows fundamental differences. Delays in diagnosis or initiation of treatment increase the risk of ocular complications. Currently, the diagnosis of IK is mainly based on slit-lamp examination and corneal scrapings. Notably, these diagnostic methods have their drawbacks, including experience-dependency, tissue damage, and time consumption. Artificial intelligence (AI) is designed to mimic and enhance human decision-making. An increasing number of studies have utilized AI in the diagnosis of IK. In this paper, we propose to use AI to diagnose IK (model 1), differentiate between bacterial keratitis and fungal keratitis (model 2), and discriminate the filamentous type from the yeast type of fungal cases (model 3). Overall, 9329 slit-lamp photographs gathered from 977 patients were enrolled in the study. The models exhibited remarkable accuracy, with model 1 achieving 99.3%, model 2 at 84%, and model 3 reaching 77.5%. In conclusion, our study offers valuable support in the early identification of potential fungal and bacterial keratitis cases and helps enable timely management.

The Potential of Mesenchymal Stem/Stromal Cell Therapy in Mustard Keratopathy: Discovering New Roads to Combat Cellular Senescence

Mesenchymal stem/stromal cells (MSCs) are considered a valuable option to treat ocular surface disorders such as mustard keratopathy (MK). MK often leads to vision impairment due to corneal opacification and neovascularization and cellular senescence seems to have a role in its pathophysiology. Herein, we utilized intrastromal MSC injections to treat MK. Thirty-two mice were divided into four groups based on the exposure to 20 mM or 40 mM concentrations of mustard and receiving the treatment or not. Mice were clinically and histopathologically examined. Histopathological evaluations were completed after the euthanasia of mice after four months and included hematoxylin and eosin (H&E), CK12, and beta-galactosidase (β-gal) staining. The treatment group demonstrated reduced opacity compared to the control group. While corneal neovascularization did not display significant variations between the groups, the control group did register higher numerical values. Histopathologically, reduced CK12 staining was detected in the control group. Additionally, β-gal staining areas were notably lower in the treatment group. Although the treated groups showed lower severity of fibrosis compared to the control groups, statistical difference was not significant. In conclusion, it seems that delivery of MSCs in MK has exhibited promising therapeutic results, notably in reducing corneal opacity. Furthermore, the significant reduction in the β-galactosidase staining area may point towards the promising anti-senescence potential of MSCs.

In praise of povidone-iodine application in ophthalmology

Polyvinyl pyrrolidone or povidone-iodine (PVP-I) is a water-soluble complex formed by the combination of iodine and a water-soluble polymer, polyvinyl pyrrolidone. This complex exerts bactericidal, fungicidal, and virucidal action by gradually releasing free iodine at the site of application to react with pathogens. In ophthalmology, PVP-I is used as a disinfectant and antiseptic agent for preoperative preparation of the skin and mucous membranes and for treating contaminated wounds. PVP-I has been shown to reduce effectively the risk of endophthalmitis in various ocular procedures, including cataract surgery and intravitreal injections; however, it has also been used in the treatment of conjunctivitis, keratitis, and endophthalmitis, with promising results especially in low-resource situations. PVP-I has been associated with complications such as postoperative eye pain, persistent corneal epithelial defects, ocular inflammation, and an attendant risk of keratitis. In cases of poor PVP-I tolerance, applying PVP-I at lower concentrations or using alternative antiseptics such as chlorhexidine should be considered. We provide an update on the efficacy of PVP-I in the prophylaxis and treatment of conjunctivitis, keratitis, and endophthalmitis and a comprehensive analysis of the current literature regarding the use of PVP-I in the management of these ocular conditions. Also, PVP-I-related adverse effects and toxicities and its alternatives are discussed. The goal is to present a thorough evaluation of the available evidence and to offer practical recommendations for clinicians regarding the therapeutic usage of PVP-I in ophthalmology.

Cellular senescence and ophthalmic diseases: narrative review

PURPOSE

Cellular senescence is a state of permanent growth arrest whereby a cell reaches its replicative limit. However, senescence can also be triggered prematurely in certain stressors including radiation, oxidative stress, and chemotherapy. This stress-induced senescence has been studied in the context of promoting inflammation, tumor development, and several chronic degenerative diseases of aging. Emerging research has elucidated the role of senescence in various ocular diseases.

METHODS

The literature search was performed using PubMed with using the query (senescence OR aging) AND (eye disease OR ocular disease OR ophthalmic disease OR cornea OR glaucoma OR cataract OR retina) on October 20th, 2022. No time restriction was proposed. Articles were excluded if they were not referenced in English.

RESULTS

Overall, 51 articles regarding senescence and ocular diseases were found and summarized in this study. Several signaling pathways have been implicated in the development of senescence. Currently, senescence has been linked to various corneal and retinal pathologies, as well as cataract and glaucoma. Given the number of pathologies, senolytics, which are small molecules with the ability to selective targeting of senescent cells, can be used as therapeutic or prophylactic agents.

CONCLUSIONS

Senescence has been shown to underlie the pathogenesis of numerous ocular diseases. The overall literature on senescence and ocular disease is growing rapidly. There is an ongoing debate whether or not cellular senescence detected in experiments contributes in a significant way to diseases. Research on understanding the mechanism of senescence from ocular cells and tissues is just beginning. Multiple animal models are required to test potential senolytics. Currently, no studies exist to date which have demonstrated the benefits of senolytic therapies in human studies.

Artificial Intelligence and Infectious Keratitis: Where Are We Now?

Infectious keratitis (IK), which is one of the most common and catastrophic ophthalmic emergencies, accounts for the leading cause of corneal blindness worldwide. Different pathogens, including bacteria, viruses, fungi, and parasites, can cause IK. The diagnosis and etiology detection of IK pose specific challenges, and delayed or incorrect diagnosis can significantly worsen the outcome. Currently, this process is mainly performed based on slit-lamp findings, corneal smear and culture, tissue biopsy, PCR, and confocal microscopy. However, these diagnostic methods have their drawbacks, including experience dependency, tissue damage, cost, and time consumption. Diagnosis and etiology detection of IK can be especially challenging in rural areas or in countries with limited resources. In recent years, artificial intelligence (AI) has opened new windows in medical fields such as ophthalmology. An increasing number of studies have utilized AI in the diagnosis of anterior segment diseases such as IK. Several studies have demonstrated that AI algorithms can diagnose and detect the etiology of IK accurately and fast, which can be valuable, especially in remote areas and in countries with limited resources. Herein, we provided a comprehensive update on the utility of AI in IK.

Post-laser refractive surgery keratitis: A concise narrative review

Laser refractive surgery (LRS) is a specialized surgical discipline within ophthalmology that focuses on vision correction via laser techniques. LRS requires a high rate of accuracy and exactitude to improve the visual outcome and minimize complications, which may lead to delayed visual recovery. Keratitis, either infectious or noninfectious, is a post-LRS complication that requires early diagnosis and proper interventional measures. In this narrative review, we summarize different aspects of keratitis following LRS. This literature review aims to provide a thorough understanding of the causes of post-LRS infectious keratitis and its appropriate management for successful outcomes.

Intrastromal versus subconjunctival injection of mesenchymal stem/stromal cells for promoting corneal repair

PURPOSE

Different approaches to delivery of mesenchymal stem/stromal cells (MSCs) for ameliorating corneal injuries have been investigated. This study was aimed to compare the efficacy of intrastromal and subconjunctival injection of human bone marrow-derived MSCs (hBM-MSCs) in a corneal epithelial injury model.

METHODS

Twenty-four C57BL/6J mice underwent total corneal and limbal epithelial debridement. Then, the mice were divided into three different groups: (1) intrastromal hBM-MSCs injection, (2) subconjunctival hBM-MSCs injection, and (3) injection of frozen medium as a control. Mice were monitored by slit lamp and underwent anterior segment optical coherence tomography (ASOCT). Following euthanasia, the corneas were further evaluated by histology and immunostaining.

RESULTS

hBM-MSC injection successfully healed epithelial defects regardless of the delivery route (P < 0.001). However, intrastromal injection was superior to subconjunctival injection in reducing defect area (P = 0.001). Intrastromal injection of hBM-MSCs also significantly reduced corneal opacity and neovascularization and improved ASOCT parameters compared to subconjunctival injection or no treatment (P < 0.001, P = 0.003, and P < 0.001, respectively). Although both of the treatment groups were positive for CK12 and had reduced levels of MUC5AC compared to the control, CK12 staining was stronger in the intrastromal group compared to the subconjunctival group. Also, persistency of MSCs was confirmed by in vivo (up to 2 weeks) and in vitro assessments (up to 4 weeks).

CONCLUSIONS

Although the injection of hBM-MSC using both intrastromal and subconjunctival methods improve wound healing and reduce neovascularization and opacity, the intrastromal approach is superior in terms of corneal healing.

Why Are Corneal Specialists Resistant to Treating Patients Who Have Severe Ocular Surface Disease With Limbal Stem Cell Deficiency?

PURPOSE

To highlight the paucity of surgeons performing ocular surface stem cell transplantation with systemic immunosuppression (OSSTx with SI) for limbal stem cell deficiency (LSCD) patients, suboptimal treatments for LSCD, and obstacles to adoption.

METHODS

A review of the Eye Bank Association of America annual reports and the authors' case volume for OSSTx with SI was performed. Examination of the published literature on corneal surgeries, especially for LSCD, was completed. These findings were combined with our clinical observations to develop this editorial.

RESULTS

Despite techniques and protocols for OSSTx with SI published more than 30 years ago for the treatment of severe bilateral LSCD, only a small number of corneal specialists have adopted these techniques. There is a paucity of attention to this population of patients, with minimal publications to advance this area of our field. We are too often referred patients with LSCD and severe ocular surface disease that have had suboptimal treatments such as penetrating keratoplasties or primary keratoprostheses. Hesitancy for adopting OSSTx with SI is likely due to a lack of exposure to these procedures during training and fear of systemic immunosuppression. Corneal surgeons are likely unaware of the safety of systemic immunosuppression with appropriate monitoring especially when comanaging these patients with an organ transplant specialist.

CONCLUSION

There is a large unmet need for the treatment of corneal blindness secondary to conjunctival and LSCD. For the vast majority of patients, OSSTx should be the first surgical choice to treat these eyes. We hope major ophthalmology centers will meet this need by building programs, and groups of corneal surgeons should collaborate to create regional centers to make this treatment more accessible to help this population.

A Case Series of Infectious Keratitis After Corneal Cross-linking

PURPOSE

To present the 7-year experience of a tertiary eye hospital while exploring possible risk factors and incidence of infectious keratitis in patients undergoing standard corneal cross-linking (CXL).

METHODS

This retrospective cohort study included patients with progressive keratoconus undergoing standard CXL in the Farabi Eye Hospital and all other patients who had undergone CXL in other facilities and were diagnosed as having infectious keratitis in the 7-year period of the study.

RESULTS

Among the total of 4,863 eyes that underwent CXL, 6 eyes developed infectious keratitis, yielding an incidence rate of 0.12%. Additionally, 13 eyes from 10 patients with a CXL history in other facilities who developed infectious keratitis were included. The mean age was 23.75 years, and 75% of patients were men and 25% were women. Gram-positive bacteria and Staphylococcus aureus were the most prevalent pathogens. Meibomian gland dysfunction, dry eye disease, or blepharitis were present in 12 patients. Medical treatment did not arrest the disease progress in 5 patients, which eventually required cases to undergo keratoplasty.

CONCLUSIONS

This study supports the need for proper patient selection by using a comprehensive medical history. It also highlights the imperative role of rigorous patient education and follow-up, particularly in the first postoperative week. Finally, the study emphasizes aggressive early therapy for patients with suspicious findings. [J Refract Surg. 2023;39(8):564-572.].

Enhancement of the SESN2-SHP cascade by melatonin ameliorates hepatic gluconeogenesis by inhibiting the CRBN-BTG2-CREBH signaling pathway

Melatonin is involved in the regulation of various biological functions. Here, we explored a novel molecular mechanism by which the melatonin-induced sestrin2 (SESN2)-small heterodimer partner (SHP) signaling pathway protects against fasting- and diabetes-mediated hepatic glucose metabolism. Various key gene expression analyses were performed and multiple metabolic changes were assessed in liver specimens and primary hepatocytes of mice and human participants. The expression of the hepatic cereblon (CRBN) and b-cell translocation gene 2 (BTG2) genes was significantly increased in fasting mice, diabetic mice, and patients with diabetes. Overexpression of Crbn and Btg2 increased hepatic gluconeogenesis by enhancing cyclic adenosine monophosphate (cAMP)-responsive element-binding protein H (CREBH), whereas this phenomenon was prominently ablated in Crbn null mice and Btg2-silenced mice. Interestingly, melatonin-induced SESN2 and SHP markedly reduced hepatic glucose metabolism in diabetic mice and primary hepatocytes, and this protective effect of melatonin was strikingly reversed by silencing Sesn2 and Shp. Finally, the melatonin-induced SESN2-SHP signaling pathway inhibited CRBN- and BTG2-mediated hepatic gluconeogenic gene transcription via the competition of BTG2 and the interaction of CREBH. Mitigation of the CRBN-BTG2-CREBH axis by the melatonin-SESN2-SHP signaling network may provide a novel therapeutic strategy to treat metabolic dysfunction due to diabetes.

Cellular senescence implication in mustard keratopathy

Mustard agents are vesicants that were used in warfare multiple times. They are potent alkylating agents that activate cellular pathways of apoptosis, increase oxidative stress, and induce inflammation. Eyes are particularly susceptible to mustard exposure with a wide range of ocular surface damage. Three main categories of mustard-related eye injuries are acute, chronic, and delayed-onset manifestations. Mustard keratopathy (MK) is a known complication characterized by corneal opacification, ulceration, thinning, and neovascularization that can lead to severe vision loss and discomfort. Recently, a few reports demonstrated the role of senescence induction as a new pathological mechanism in mustard-related injuries that could affect wound healing. We ran the first murine model of delayed-onset MK and nitrogen mustard-induced senescence, evaluating the pathological signs of senescence in the cornea using beta-galactosidase staining. Our results suggest that nitrogen mustard exposure causes senescence in the corneal cells, which could be the underlying mechanism for chronic and late-onset ocular surface damage. We also found a significant correlation between the percentage of positive beta-galactosidase staining and the degree of fibrosis in the cornea. This provides valuable insight into the possible role of anti-senescence drugs in the near future for accelerating corneal healing and restricting fibrosis in patients with mustard keratopathy.

Application of biomaterials and nanotechnology in corneal tissue engineering

Corneal diseases are among the most common causes of blindness worldwide. Regardless of the etiology, corneal opacity- or globe integrity-threatening conditions may necessitate corneal replacement procedures. Several procedure types are currently available to address these issues, based on the complexity and extent of injury. Corneal allograft or keratoplasty is considered to be first-line treatment in many cases. However, a significant proportion of the world's population are reported to have no access to this option due to limitations in donor preparation. Thus, providing an appropriate, safe, and efficient synthetic implant (e.g., artificial cornea) may revolutionize this field. Nanotechnology, with its potential applications, has garnered a lot of recent attention in this area, however, there is seemingly a long way to go. This narrative review provides a brief overview of the therapeutic interventions for corneal pathologies, followed by a summary of current biomaterials used in corneal regeneration and a discussion of the nanotechnologies that can aid in the production of superior implants.

Mustard Gas-Induced Ocular Surface Disorders: An Update on the Pathogenesis, Clinical Manifestations, and Management

PURPOSE

Mustard gas (MG) is a potent blistering and alkylating agent that has been used for military and terrorism purposes. Ocular surface injuries are common after exposure to MG. This review provides an update on the pathophysiology, ocular surface complications, and treatment options for MG-related ocular injuries.

METHODS

Required information was obtained by reviewing various databases such as Cochrane Library, Google Scholar, and PubMed until March 2022. Data were collected by using keywords: "mustard gas" OR "sulfur mustard" AND "eye" OR "cornea" OR "ocular complication" OR "keratitis" OR "keratopathy" OR "limbal stem cell deficiency" OR "dry eye."

RESULTS

Chronic intracellular toxicity, inflammation, and ischemia have been shown to play an essential role in the pathogenesis of MG injury. Ocular surface injuries can have acute, chronic, and most distinctly a delayed-onset presentation leading to various degrees of limbal stem cell deficiency. To date, no treatment has been agreed on as the standard treatment for chronic/delayed-onset MG keratopathy. Based on the authors' experience, we propose a management algorithm for MG-related ocular surface injuries involving optimization of ocular health, anti-inflammatory therapy, and if needed surgical interventions. The management of chronic and delayed-onset presentation remains challenging.

CONCLUSIONS

MG keratopathy is a unique form of chemical injury which can lead to a range of ocular surface pathologies. Long-term anti-inflammatory therapy even in patients with seemingly mild disease may potentially reduce the likelihood of the development of more severe delayed-onset disease.

The effect of decellularization protocols on characterizations of thermoresponsive and light-curable corneal extracellular matrix hydrogels

To compare the effects of two decellularization protocols on the characteristics of fabricated COrnea Matrix (COMatrix) hydrogels. Porcine corneas were decellularized with Detergent (De) or Freeze-Thaw (FT)-based protocols. DNA remnant, tissue composition and α-Gal epitope content were measured. The effect of α-galactosidase on α-Gal epitope residue was assessed. Thermoresponsive and light-curable (LC) hydrogels were fabricated from decellularized corneas and characterized with turbidimetric, light-transmission and rheological experiments. The cytocompatibility and cell-mediated contraction of the fabricated COMatrices were assessed. Both protocols reduced the DNA content to < 0.1 µg/mg (native, > 0.5 µg/mg), and preserved the collagens and glycosaminoglycans. The α-Gal epitope remnant decreased by > 50% following both decellularization methods. We observed more than 90% attenuation in α-Gal epitope after treatment with α-galactosidase. The thermogelation half-time of thermoresponsive COMatrices derived from De-Based protocol (De-COMatrix) was 18 min, similar to that of FT-COMatrix (21 min). The rheological characterizations revealed significantly higher shear moduli of thermoresponsive FT-COMatrix (300.8 ± 22.5 Pa) versus De-COMatrix 178.7 ± 31.3 Pa, p < 0.01); while, this significant difference in shear moduli was preserved after fabrication of FT-LC-COMatrix and De-LC-COMatrix (18.3 ± 1.7 vs 2.8 ± 2.6 kPa, respectively, p < 0.0001). All thermoresponsive and light-curable hydrogels have similar light-transmission to human corneas. Lastly, the obtained products from both decellularization methods showed excellent in vitro cytocompatibility. We found that FT-LC-COMatrix was the only fabricated hydrogel with no significant cell-mediated contraction while seeded with corneal mesenchymal stem cells (p < 0.0001). The significant effect of decellularization protocols on biomechanical properties of hydrogels derived from porcine corneal ECM should be considered for further applications.

Extracellular-Vesicle-Based Therapeutics in Neuro-Ophthalmic Disorders

Extracellular vesicles (EVs) have been recognized as promising candidates for developing novel therapeutics for a wide range of pathologies, including ocular disorders, due to their ability to deliver a diverse array of bioactive molecules, including proteins, lipids, and nucleic acids, to recipient cells. Recent studies have shown that EVs derived from various cell types, including mesenchymal stromal cells (MSCs), retinal pigment epithelium cells, and endothelial cells, have therapeutic potential in ocular disorders, such as corneal injury and diabetic retinopathy. EVs exert their effects through various mechanisms, including promoting cell survival, reducing inflammation, and inducing tissue regeneration. Furthermore, EVs have shown promise in promoting nerve regeneration in ocular diseases. In particular, EVs derived from MSCs have been demonstrated to promote axonal regeneration and functional recovery in various animal models of optic nerve injury and glaucoma. EVs contain various neurotrophic factors and cytokines that can enhance neuronal survival and regeneration, promote angiogenesis, and modulate inflammation in the retina and optic nerve. Additionally, in experimental models, the application of EVs as a delivery platform for therapeutic molecules has revealed great promise in the treatment of ocular disorders. However, the clinical translation of EV-based therapies faces several challenges, and further preclinical and clinical studies are needed to fully explore the therapeutic potential of EVs in ocular disorders and to address the challenges for their successful clinical translation. In this review, we will provide an overview of different types of EVs and their cargo, as well as the techniques used for their isolation and characterization. We will then review the preclinical and clinical studies that have explored the role of EVs in the treatment of ocular disorders, highlighting their therapeutic potential and the challenges that need to be addressed for their clinical translation. Finally, we will discuss the future directions of EV-based therapeutics in ocular disorders. Overall, this review aims to provide a comprehensive overview of the current state of the art of EV-based therapeutics in ophthalmic disorders, with a focus on their potential for nerve regeneration in ocular diseases.

Wound-Healing Effects of Mesenchymal Stromal Cell Secretome in the Cornea and the Role of Exosomes

Mesenchymal stromal/stem cells (MSCs) and their secreted factors have been shown to have immunomodulatory and regenerative effects. In this study, we investigated human bone-marrow-derived MSC secretome (MSC-S) for the treatment of corneal epithelial wounds. Specifically, we evaluated the role of MSC extracellular vesicles (EV)/exosomes in mediating the wound-healing effects of the MSC-S. In vitro studies using human corneal epithelial cells showed that MSC-CM increased cell proliferation in HCEC and HCLE cells, while EV-depleted MSC-CM showed lower cell proliferation in both cell lines compared to the MSC-CM group. In vitro and in vivo experiments revealed that 1X MSC-S consistently promoted wound healing more effectively than 0.5X MSC-S, and MSC-CM promoted wound healing in a dose-dependent manner, while exosome deprivation delayed wound healing. We further evaluated the incubation period of MSC-CM on corneal wound healing and showed that MSC-S collected for 72 h is more effective than MSC-S collected for 48 h. Finally, we evaluated the stability of MSC-S under different storage conditions and found that after one cycle of freeze-thawing, MSC-S is stable at 4 °C for up to 4 weeks. Collectively, we identified the following: (i) MSC-EV/Exo as the active ingredient in MSC-S that mediates the wound-healing effects in the corneal epithelium, providing a measure to optimize its dosing for a potential clinical product; (ii) Treatment with EV/Exo-containing MSC-S resulted in an improved corneal barrier and decreased corneal haze/edema relative to EV/Exo-depleted MSC-S; (iii) The stability of MSC-CM for up to 4 weeks showed that the regular storage condition did not significantly impact its stability and therapeutic functions.

Superior limbic keratoconjunctivitis: Update on pathophysiology and management

Superior limbic keratoconjunctivitis (SLK) is an under-recognized condition characterized by a final common pathologic presentation of superior conjunctival and limbal inflammation and staining. Existing literature attributes both microtrauma and local inflammation, frequently in the setting of tear film insufficiency, as the underlying mechanisms that lead to a self-perpetuating pathologic process dependent in on inflammatory cells and signaling. Effective treatments act by targeting inflammation and by mitigating mechanical stressors. This critical review discusses the latest in our understanding of the pathophysiology of SLK and how it guides our treatment strategies.

Aqueous-deficient dry eye disease: Preferred practice pattern guidelines on clinical approach, diagnosis, and management

Dry eye disease (DED) is a broad term that includes a diverse group of clinical disorders. Aqueous-deficient dry eye (ADDE), a subtype of DED, is characterized by decreased tear production by the lacrimal gland. It can be seen in up to one-third of individuals with DED and can be comorbid with a systemic autoimmune process or occur secondary to an environmental insult. Since ADDE can be a source of long-term suffering and severe visual impairment, early identification and adequate treatment are imperative. Multiple etiologies can underlie ADDE, and it is critical to identify the underlying cause to not only improve the ocular health but also to improve the overall quality of life and well-being of affected individuals. This review discusses the various etiologies of ADDE, highlights a pathophysiology-based approach for evaluating underlying contributors, outlines various diagnostic tests, and reviews treatment options. We present the current standards and discuss ongoing research in this field. Through this review, we propose a treatment algorithm that would be useful for an ophthalmologist in diagnosing and managing individuals with ADDE.

Concise Review: Bioengineering of Limbal Stem Cell Niche

The corneal epithelium is composed of nonkeratinized stratified squamous cells and has a significant turnover rate. Limbal integrity is vital to maintain the clarity and avascularity of the cornea as well as regeneration of the corneal epithelium. Limbal epithelial stem cells (LESCs) are located in the basal epithelial layer of the limbus and preserve this homeostasis. Proper functioning of LESCs is dependent on a specific microenvironment, known as the limbal stem cell niche (LSCN). This structure is made up of various cells, an extracellular matrix (ECM), and signaling molecules. Different etiologies may damage the LSCN, leading to limbal stem cell deficiency (LSCD), which is characterized by conjunctivalization of the cornea. In this review, we first summarize the basics of the LSCN and then focus on current and emerging bioengineering strategies for LSCN restoration to combat LSCD.

Corneal stem cells niche and homeostasis impacts in regenerative medicine; concise review

The limbal stem cells niche (LSCN) is an optimal microenvironment that provides the limbal epithelial stem cells (LESCs) and strictly regulates their proliferation and differentiation. Disturbing the LSCN homeostasis can lead to limbal stem cell dysfunction (LSCD) and subsequent ocular surface aberrations, such as corneal stromal inflammation, persistent epithelial defects, corneal neovascularisation, lymphangiogenesis, corneal opacification, and conjunctivalization. As ocular surface disorders are considered the second main cause of blindness, it becomes crucial to explore different therapeutic strategies for restoring the functions of the LSCN. A major limitation of corneal transplantation is the current shortage of donor tissue to meet the requirements worldwide. In this context, it becomes mandatory to find an alternative regenerative medicine, such as using cultured limbal epithelial/stromal stem cells, inducing the production of corneal like cells by using other sources of stem cells, and using tissue engineering methods aiming to produce the three-dimensional (3D) printed cornea. Limbal epithelial stem cells have been considered the magic potion for eye treatment. Epithelial and stromal stem cells in the limbal niche hold the responsibility of replenishing the corneal epithelium. These stem cells are being used for transplantation to maintain corneal epithelial integrity and ultimately sustain optimal vision. In this review, we summarised the characteristics of the LSCN and their current and future roles in restoring corneal homeostasis in eyes with LSCD.

Applications of mesenchymal stem cells in ocular surface diseases: sources and routes of delivery

INTRODUCTION

Mesenchymal stem cells (MSCs) are novel, promising agents for treating ocular surface disorders. MSCs can be isolated from several tissues and delivered by local or systemic routes. They produce several trophic factors and cytokines, which affect immunomodulatory, transdifferentiating, angiogenic, and pro-survival pathways in their local microenvironment via paracrine secretion. Moreover, they exert their therapeutic effect through a contact-dependent manner.

AREAS COVERED

In this review, we discuss the characteristics, sources, delivery methods, and applications of MSCs in ocular surface disorders. We also explore the potential application of MSCs to inhibit senescence at the ocular surface.

EXPERT OPINION

Therapeutic application of MSCs in ocular surface disorders are currently under investigation. One major research area is corneal epitheliopathies, including chemical or thermal burns, limbal stem cell deficiency, neurotrophic keratopathy, and infectious keratitis. MSCs can promote corneal epithelial repair and prevent visually devastating sequelae of non-healing wounds. However, the optimal dosages and delivery routes have yet to be determined and further clinical trials are needed to address these fundamental questions.

Effect of Increasing Povidone-Iodine Exposure on Corneal Epithelium and Impact on Donor Rim Cultures

PURPOSE

The purpose of this study was to assess the effect of a second povidone-iodine (PVP-I) application at the time of donor tissue recovery on overall tissue quality and to analyze the rate of positive fungal and bacterial rim cultures before and after implementing increased PVP-I exposure.

METHODS

The left cornea was recovered after a single application of PVP-I, while the right cornea was recovered after double PVP-I application in research-consented donors. The epithelial cell death rate was estimated using viability assay in corneal whole mounts under 10× objective (n = 5). Clinical characteristics of epithelium, stroma, and endothelium; positive rim culture rate; and incidences of infectious postoperative adverse reactions were compared for a period of 14 months before and after implementation of increased PVP-I protocol.

RESULTS

The average epithelial cell death rate was unaltered between single and double PVP-I exposure groups. We observed a modest 10% increase in the number of tissues with mild edema after implementation of increased PVP-I exposure. Nonetheless, the percentage of tissues with moderate or severe edema was unaltered. The average positive rim culture rate decreased from 1.17% to 0.88% (P = 0.075) after implementation of the double PVP-I soak procedure. There has been only one report of infectious postoperative adverse reactions since this procedure change. By contrast, there were 5 reports for a period of 14 months before implementation of this protocol.

CONCLUSIONS

These results indicate that new donor preparation methods with an additional 5 minutes of PVP-I exposure do not affect tissue quality, reduce positive rim cultures, and lead to lower incidence of postoperative infection.

Bone marrow mesenchymal stromal cells in a 3D system produce higher concentration of extracellular vesicles (EVs) with increased complexity and enhanced neuronal growth properties

PURPOSE

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) have been demonstrated to possess great potential in preclinical models. An efficient biomanufacturing platform is necessary for scale up production for clinical therapeutic applications. The aim of this study is to investigate the potential differences in neuro-regenerative properties of MSC-derived EVs generated in 2D versus 3D culture systems.

METHOD

Human bone marrow MSCs (BM-MSCs) were cultured in 2D monolayer and 3D bioreactor systems. EVs were isolated using ultracentrifugation followed by size and concentration measurements utilizing dynamic light scattering (NanoSight) and by fluorescence staining (ExoView). Mouse trigeminal ganglia (TG) neurons were isolated from BALB/c mice and cultured in the presence or absence of EVs derived from 2D or 3D culture systems. Neuronal growth and morphology were monitored over 5 days followed by immunostaining for β3 tubulin. Confocal images were analyzed by Neurolucida software to obtain the density and length of the neurites.

RESULTS

The NanoSight tracking analysis revealed a remarkable increase (24-fold change) in the concentration of EVs obtained from the 3D versus 2D culture condition. ExoView analysis showed a significantly higher concentration of CD63, CD81, and CD9 markers in the EVs derived from 3D versus 2D conditions. Furthermore, a notable shift toward a more heterogeneous phenotype was observed in the 3D-derived EVs compared to those from 2D culture systems. EVs derived from both culture conditions remarkably induced neurite growth and elongation after 5 days in culture compared to untreated control. Neurolucida analysis of the immunostaining images (β3 tubulin) showed a significant increase in neurite length in TG neurons treated with 3D- versus 2D-derived EVs (3301.5 μm vs. 1860.5 μm, P < 0.05). Finally, Sholl analysis demonstrated a significant increase in complexity of the neuronal growth in neurons treated with 3D- versus 2D-derived EVs (P < 0.05).

CONCLUSION

This study highlights considerable differences in EVs obtained from different culture microenvironments, which could have implications for their therapeutic effects and potency. The 3D culture system seems to provide a preferred environment that modulates the paracrine function of the cells and the release of a higher number of EVs with enhanced biophysical properties and functions in the context of neurite elongation and growth.

A Light-Curable and Tunable Extracellular Matrix Hydrogel for In Situ Suture-Free Corneal Repair

Corneal injuries are a major cause of blindness worldwide. To restore corneal integrity and clarity, there is a need for regenerative bio-integrating materials for in-situ repair and replacement of corneal tissue. Here, we introduce Light-curable COrnea Matrix (LC-COMatrix), a tunable material derived from decellularized porcine cornea extracellular matrix containing un-denatured collagen and sulfated glycosaminoglycans. It is a functionalized hydrogel with proper swelling behavior, biodegradation, and viscosity that can be cross-linked in situ with visible light, providing significantly enhanced biomechanical strength, stability, and adhesiveness. Cross-linked LC-COMatrix strongly adheres to human corneas ex vivo and effectively closes full-thickness corneal perforations with tissue loss. Likewise, in vivo, LC-COMatrix seals large corneal perforations, replaces partial-corneal stromal defects and bio-integrates into the tissue in rabbit models. LC-COMatrix is a natural ready-to-apply bio-integrating adhesive that is representative of native corneal matrix with potential applications in corneal and ocular surgeries.

Long-term retinal protection by MEK inhibition in Pax6 haploinsufficiency mice

Aniridia is a panocular condition characterized by impaired eye development and vision, which is mainly due to the haploinsufficiency of the paired-box-6 (PAX6) gene. Like what is seen in aniridia patients, Pax6-deficient mice Pax6Sey-Neu/+ exhibit a varied degree of ocular damage and impaired vision. Our previous studies showed that these phenotypes were partially rescued by PD0325901, a mitogen-activated protein kinase kinase (MEK or MAP2K) inhibitor. In this study, we assessed the long-term efficacy of PD0325901 treatment in retinal health and visual behavior. At about one year after the postnatal treatment with PD0325901, Pax6Sey-Neu/+ mice showed robust improvements in retina size and visual acuity, and the elevated intraocular pressure (IOP) was also alleviated, compared to age-matched mice treated with vehicles only. Moreover, the Pax6Sey-Neu/+ eyes showed disorganized retinal ganglion cell (RGC) axon bundles and retinal layers, which we termed as hotspots. We found that the PD treatment reduced the number and size of hotspots in the Pax6Sey-Neu/+ retinas. Taken together, our results suggest that PD0325901 may serve as an efficacious intervention in protecting retina and visual function in aniridia-afflicted subjects.

Peripheral Ulcerative Keratitis: A Review

Peripheral ulcerative keratitis (PUK) is a rare but serious ocular condition that is an important clinical entity due to its ophthalmological and systemic implications. It is characterized by progressive peripheral corneal stromal thinning with an associated epithelial defect and can be associated with an underlying local or systemic pro-inflammatory condition, or present in an idiopathic form (Mooren ulcer). Associated conditions include autoimmune diseases, systemic and ocular infections, dermatologic diseases, and ocular surgery. Cell-mediated and autoantibody- mediated immune responses have been implicated in the pathogenesis of PUK, destroying peripheral corneal tissue via matrix metalloproteinases. Clinically, patients with PUK present with painful vision loss, a peripheral corneal ulcer, and often adjacent scleritis, episcleritis, iritis, or conjunctivitis. Diagnostic evaluation should be focused on identifying the underlying etiology and ruling out conditions that may mimic PUK, including marginal keratitis and Terrien marginal degeneration. Treatment should be focused on reducing local disease burden with topical lubrication, while simultaneously addressing the underlying cause with antimicrobials or anti-inflammatory when appropriate. Existing and emerging biologic immunomodulatory therapies have proven useful in PUK due to autoimmune conditions. Surgical treatment is generally reserved for cases of severe thinning or corneal perforation.

OUP accepted manuscript

The corneal epithelium serves to protect the underlying cornea from the external environment and is essential for corneal transparency and optimal visual function. Regeneration of this epithelium is dependent on a population of stem cells residing in the basal layer of the limbus, the junction between the cornea and the sclera. The limbus provides the limbal epithelial stem cells (LESCs) with an optimal microenvironment, the limbal niche, which strictly regulates their proliferation and differentiation. Disturbances to the LESCs and/or their niche can lead to the pathologic condition known as limbal stem cell deficiency (LSCD) whereby the corneal epithelium is not generated effectively. This has deleterious effects on the corneal and visual function, due to impaired healing and secondary corneal opacification. In this concise review, we summarize the characteristics of LESCs and their niche, and present the current and future perspectives in the management of LSCD with an emphasis on restoring the function of the limbal niche.

Recombinant Interferon Alpha-2b as Primary Treatment for Ocular Surface Squamous Neoplasia

Purpose

To investigate the effects of topical and perilesional interferon alpha-2b as primary treatment for ocular surface squamous neoplasia (OSSN).

Methods

In this prospective interventional case series, topical interferon alpha-2b (3 MIU/mL) was used as the initial treatment of OSSN, with perilesional interferon alpha-2b (3 MIU/mL) added based on clinical response. The primary outcome was complete tumor resolution. Spearman's rank correlation test was used to investigate the association of complete tumor resolution and time to resolution with baseline tumor characteristics and the American Joint Committee on Cancer (AJCC) classification for OSSN.

Results

Ninety-two patients (92 OSSN tumors) were included in the study. The total follow-up duration was 13.57 ± 2.14 months (median: 12, range: 3-23). The median basal tumor diameter was 4 mm (mean: 4.13 ± 1.37). Complete tumor resolution was achieved in 89 cases (96.73%), with a median time to complete tumor resolution of 5 months (mean: 4.64 ± 1.92). Complete tumor resolution was 57 of 57 in T1 (100%), 8 of 9 in T2 (88.88%), and 21 of 23 in T3 (91.30%). There were statistically significant correlations between AJCC classification and complete tumor resolution (Spearman's r = -0.22, P = 0.03) and maximal basal tumor diameter and the time to complete resolution (Spearman's r = 0.35, P = 0.001). There were no recurrences during the study follow-up period.

Conclusion

Topical interferon alpha-2b is effective and well tolerated as a primary treatment for OSSN, with a high rate of tumors responding completely to therapy.

The Limbal Niche and Regenerative Strategies

The protective function and transparency provided by the corneal epithelium are dependent on and maintained by the regenerative capacity of limbal epithelial stem cells (LESCs). These LESCs are supported by the limbal niche, a specialized microenvironment consisting of cellular and non-cellular components. Disruption of the limbal niche, primarily from injuries or inflammatory processes, can negatively impact the regenerative ability of LESCs. Limbal stem cell deficiency (LSCD) directly hampers the regenerative ability of the corneal epithelium and allows the conjunctival epithelium to invade the cornea, which results in severe visual impairment. Treatment involves restoring the LESC population and functionality; however, few clinically practiced therapies currently exist. This review outlines the current understanding of the limbal niche, its pathology and the emerging approaches targeted at restoring the limbal niche. Most emerging approaches are in developmental phases but show promise for treating LSCD and accelerating corneal regeneration. Specifically, we examine cell-based therapies, bio-active extracellular matrices and soluble factor therapies in considerable depth.

Preclinical Evaluation of the Safety and Efficacy of Cryopreserved Bone Marrow Mesenchymal Stromal Cells for Corneal Repair

Purpose

Mesenchymal stromal cells (MSCs) have been shown to enhance tissue repair as a cell-based therapy. In preparation for a phase I clinical study, we evaluated the safety, dosing, and efficacy of bone marrow–derived MSCs after subconjunctival injection in preclinical animal models of mice, rats, and rabbits.

Methods

Human bone marrow–derived MSCs were expanded to passage 4 and cryopreserved. Viability of MSCs after thawing and injection through small-gauge needles was evaluated by vital dye staining. The in vivo safety of human and rabbit MSCs was studied by subconjunctivally injecting MSCs in rabbits with follow-up to 90 days. The potency of MSCs on accelerating wound healing was evaluated in vitro using a scratch assay and in vivo using 2-mm corneal epithelial debridement wounds in mice. Human MSCs were tracked after subconjunctival injection in rat and rabbit eyes.

Results

The viability of MSCs after thawing and immediate injection through 27- and 30-gauge needles was 93.1% ± 2.1% and 94.9% ± 1.3%, respectively. Rabbit eyes demonstrated mild self-limiting conjunctival inflammation at the site of injection with human but not rabbit MSCs. In scratch assay, the mean wound healing area was 93.5% ± 12.1% in epithelial cells co-cultured with MSCs compared with 40.8% ± 23.1% in controls. At 24 hours after wounding, all MSC-injected murine eyes had 100% corneal wound closure compared with 79.9% ± 5.5% in controls. Human MSCs were detectable in the subconjunctival area and peripheral cornea at 14 days after injection.

Conclusions

Subconjunctival administration of MSCs is safe and effective in promoting corneal epithelial wound healing in animal models.

Translational Relevance

These results provide preclinical data to support a phase I clinical study.

Dose-dependent therapeutic effects of topical 1,25 OH-vitamin D3 on corneal wound healing

Conflicting results have been reported regarding the effects of 1,25 OH-vitamin D₃ on corneal wound healing. Therefore, we undertook this study to determine whether the observed differences are dose related. The dose-dependent effects of 1,25 OH-vitamin D₃ on corneal wound healing were evaluated using scratch assays on human corneal limbal-epithelial cells (HCLEs) and in vivo mouse corneal epithelial debridement. To evaluate the anti-inflammatory effects of 1,25 OH-vitamin D₃, macrophages were stimulated by a Toll-Like Receptor (TLR) ligand followed by treatment with the 10^-6 M, 10^-7 M and 10^-8 M 1,25 OH-vitamin D₃. 10^-7 M 1,25 OH-vitamin D₃ induced faster scratch wound closure compared with the other concentrations of 1,25 OH-vitamin D₃ tested (10^-6 M and 10^-8 M), and 0.02% ethanol as a control (85.8 ± 2.6%, 33.9 ± 6.74%, 32.6 ± 3.35%, and 31.6 ± 3.99%, respectively, P < 0.0001). Single-time treatment with 10^-7 M 1,25 OH-vitamin D₃ also significantly improved the healing of mouse corneal epithelial wound compared to multiple treatments and control (74.1 ± 17.3% vs. 52.4 ± 11.6% and 45.8 ± 13.4%, respectively). Polyinosinic: polycytidylic acid (poly [I:C])-stimulated macrophage cells and 10^-7 M 1,25 OH-vitamin D₃ significantly decreased gene expression of ICAM1, TLR3, IL6, IL8, and TNFα (P < 0.0001). Our results suggest the dose-dependent therapeutic effect of 1,25 OH-vitamin D₃ in corneal wound healing which can be potentially used as a non-invasive option in the treatment of corneal wounds.

Fabrication, Rheological, and Compositional Characterization of Thermoresponsive Hydrogel from Cornea

Fabricating thermoresponsive hydrogels from decellularized tissues is a trending and promising approach to develop novel biomaterials for tissue engineering and therapeutic purposes. There are differences in the characteristics of the produced hydrogels related to the source tissue as well as the decellularization and solubilization protocols used. Detailed characterization of the hydrogels will support the efforts to optimize their application as biomaterials for tissue engineering and therapeutics. Here, we describe an optimized method for fabricating an in situ thermoresponsive hydrogel from decellularized porcine cornea extracellular matrix (COMatrix), and provide a detailed characterization of its structure, thermoresponsive rheological behavior (heat-induced sol-gel transition), as well as exploring its protein composition using proteomics. COMatrix forms a transparent gel (10-min time to gelation) after in situ curing with heat, characterized by alteration in light absorbance and rheological indexes. The rheological characterization of heat-formed COMatrix gel shows similar behavior to common biomaterials utilized in tissue engineering. The fibrillar structure of COMatrix gel was observed by scanning electron microscopy showing that the density of fibers attenuates in lower concentrations. Mass spectrometry-based proteomic analysis revealed that COMatrix hydrogel is rich in proteins with known regenerative properties such as lumican, keratocan, and laminins in addition to structural collagen proteins (Data is available via ProteomeXchange with identifier PXD020606). COMatrix hydrogel is a naturally driven biomaterial with favorable biomechanical properties and protein content with potential application as a therapeutic biomaterial in ocular regeneration and tissue engineering. Impact statement Fabrication and application of decellularized porcine corneal extracellular matrix is an emerging approach for corneal tissue engineering and regeneration. There are several protocols for decellularization of porcine cornea with various efficiencies. Here, we are presenting an optimized protocol for decellularization of porcine cornea followed by fabrication of a thermoresponsive hydrogel from the decellularized cornea matrix. Moreover, the fabricated hydrogel was rheologically and compositionally characterized as crucial features to be employed for further application of this hydrogel in corneal tissue engineering and regeneration.

In-situ porcine corneal matrix hydrogel as ocular surface bandage

PURPOSE

Bioactive substrates can be used therapeutically to enhance wound healing. Here, we evaluated the effect of an in-situ thermoresponsive hydrogel from decellularized porcine cornea ECM, COMatrix (COrnea Matrix), for application as an ocular surface bandage for corneal epithelial defects.

METHODS

COMatrix hydrogel was fabricated from decellularized porcine corneas. The effects of COMatrix hydrogel on attachment and proliferation of human corneal epithelial cells (HCECs) were evaluated in vitro. The effect of COMatrix on the expressions of the inflammatory genes, IL-1β, TNF-α, and IL-6 was assessed by RT-PCR. The in-situ application and also repairing effects of COMatrix hydrogel as an ocular bandage was studied in a murine model of corneal epithelial wound. The eyes were examined by optical coherence tomography (OCT) and slit-lamp microscopy in vivo and by histology and immunofluorescence post-mortem.

RESULTS

In vitro, COMatrix hydrogel significantly enhanced the attachment and proliferation of HCECs relative to control. HCECs exposed to COMatrix had less induced expression of TNF-α (P < 0.05). In vivo, COMatrix formed a uniform hydrogel that adhered to the murine ocular surface after in-situ curing. Corneal epithelial wound closure was significantly accelerated by COMatrix hydrogel compared to control (P < 0.01). There was significant increase in the expression of proliferation marker Ki-67 in wounded corneal epithelium by COMatrix hydrogel compared to control (P < 0.05).

CONCLUSIONS

COMatrix hydrogel is a naturally derived bioactive material with potential application as an ocular surface bandage to enhance epithelial wound healing.

Lid margin keratinization in Stevens-Johnson syndrome: Review of pathophysiology and histopathology

Lid margin keratinization (LMK) is a chronic ocular sequela of Stevens-Johnson syndrome (SJS), which causes lid wiper epitheliopathy and progressive ocular surface damage. The exact etiopathogenesis of LMK, however, remains elusive. This review summarizes the potential pathophysiological mechanisms of LMK and describes its histopathological features. A literature search of articles discussing the pathophysiology of LMK in SJS was performed. The possible pathophysiologic mechanisms contributing to LMK, as identified on the literature review, included loss of the muco-cutaneous junction barrier leading to epidermalization, dyskeratosis involving the meibomian gland orifices, altered lid margin microbiome, and de novo squamous metaplasia of the marginal conjunctival epithelium. Based on these mechanisms, the possible sources of keratinized epithelium at the posterior lid margin in SJS could be the adjacent anterior eyelid skin, hyperkeratinized epithelium from the meibomian gland ductal orifices, or the inflamed marginal conjunctiva. The epithelial, sub-epithelial, and stromal changes seen in keratinized posterior lid margins in SJS patients undergoing mucous membrane grafting were also investigated. The findings revealed keratinizing squamous metaplasia of the posterior lid margin accompanied by subepithelial infiltration of helper T cells predominantly on the conjunctival side. The visible meibomian gland orifices had ductal hyperkeratinization and plugging. These findings support a role for inflammation in the pathogenesis of LMK in SJS. Future research can be directed at delineating the pathways that lead to LMK by studying the changes in the lid margin microbiome, and the molecular mechanisms regulating keratinization in the conjunctiva and the meibomian gland orifices in eyes affected by SJS.

Gene dosage manipulation alleviates manifestations of hereditary PAX6 haploinsufficiency in mice

In autosomal dominant conditions with haploinsufficiency, a single functional allele cannot maintain sufficient dosage for normal function. We hypothesized that pharmacologic induction of the wild-type allele could lead to gene dosage compensation and mitigation of the disease manifestations. The paired box 6 (PAX6) gene is crucial in tissue development and maintenance particularly in eye, brain, and pancreas. Aniridia is a panocular condition with impaired eye development and limited vision due to PAX6 haploinsufficiency. To test our hypothesis, we performed a chemical screen and found mitogen-activated protein kinase kinase (MEK) inhibitors to induce PAX6 expression in normal and mutant corneal cells. Treatment of newborn Pax6-deficient mice (Pax6Sey-Neu/+ ) with topical or systemic MEK inhibitor PD0325901 led to increased corneal PAX6 expression, improved corneal morphology, reduced corneal opacity, and enhanced ocular function. These results suggest that induction of the wild-type allele by drug repurposing is a potential therapeutic strategy for haploinsufficiencies, which is not limited to specific mutations.

Bioengineering Approaches for Corneal Regenerative Medicine

BACKGROUND

Since the cornea is responsible for transmitting and focusing light into the eye, injury or pathology affecting any layer of the cornea can cause a detrimental effect on visual acuity. Aging is also a reason for corneal degeneration. Depending on the level of the injury, conservative therapies and donor tissue transplantation are the most common treatments for corneal diseases. Not only is there a lack of donor tissue and risk of infection/rejection, but the inherent ability of corneal cells and layers to regenerate has led to research in regenerative approaches and treatments.

METHODS

In this review, we first discussed the anatomy of the cornea and the required properties for reconstructing layers of the cornea. Regenerative approaches are divided into two main categories; using direct cell/growth factor delivery or using scaffold-based cell delivery. It is expected delivered cells migrate and integrate into the host tissue and restore its structure and function to restore vision. Growth factor delivery also has shown promising results for corneal surface regeneration. Scaffold-based approaches are categorized based on the type of scaffold, since it has a significant impact on the efficiency of regeneration, into the hydrogel and non-hydrogel based scaffolds. Various types of cells, biomaterials, and techniques are well covered.

RESULTS

The most important characteristics to be considered for biomaterials in corneal regeneration are suitable mechanical properties, biocompatibility, biodegradability, and transparency. Moreover, a curved shape structure and spatial arrangement of the fibrils have been shown to mimic the corneal extracellular matrix for cells and enhance cell differentiation.

CONCLUSION

Tissue engineering and regenerative medicine approaches showed to have promising outcomes for corneal regeneration. However, besides proper mechanical and optical properties, other factors such as appropriate sterilization method, storage, shelf life and etc. should be taken into account in order to develop an engineered cornea for clinical trials.

Update on the pathogenesis and management of ocular rosacea: an interdisciplinary review

PURPOSE

Rosacea is one of the most common conditions affecting the ocular surface. The purpose of this review is to provide an update on the pathogenesis and treatment of rosacea based on the dermatology and ophthalmology literatures.

METHODS

Literature searches were conducted for rosacea and ocular rosacea. Preference was given to systematic reviews, meta-analysis, case-controlled studies, and documented case reports while excluding poorly documented case studies and commentaries. The data were examined and independently analyzed by more than two of the authors.

RESULTS

Rosacea is a complex inflammatory condition involving the pilosebaceous unit. Its underlying mechanism involves an interplay of the microbiome, innate immunity, adaptive immunity, environmental triggers, and neurovascular sensitivity. The latest classification of rosacea includes three dermatologic subgroups and a fourth subgroup, ocular rosacea. Ocular rosacea clinically displays many features that are analogous to the cutaneous disease, such as lid margin telangiectasia and phlyctenulosis. The role of environmental triggers in the exacerbation of ocular rosacea appears to be understudied. While lid hygiene and systemic treatment with tetracycline drugs remain the mainstay of treatment for ocular rosacea, newer dermatologic targets and therapies may have potential application for the eye disease.

CONCLUSIONS

Ocular rosacea appears to embody many of the manifestation of the dermatologic disease. Hence, the basic pathophysiologic mechanisms of the ocular and cutaneous disease are likely to be shared. Better understanding of the ocular surface microbiome and the immunologic mechanisms, may lead to novel approaches in the management of ocular rosacea.

Therapeutic Effects of Lyophilized Conditioned-Medium Derived from Corneal Mesenchymal Stromal Cells on Corneal Epithelial Wound Healing

Objectives: The conditioned-medium derived from corneal mesenchymal stromal cells (cMSCs) has been shown to have wound healing and immunomodulatory effects in corneal injury models. Here, the therapeutic effects of lyophilized cMSC conditioned-medium were compared with fresh conditioned-medium. Methods: The epithelial wound healing effects of fresh and lyophilized cMSC conditioned-medium were compared with conditioned-medium from non-MSC cells (corneal epithelial cells) using scratch assay. To evaluate the anti-inflammatory effects of fresh and lyophilized cMSC conditioned-media, macrophages were stimulated by a Toll-Like Receptor (TLR) ligand followed by treatment with the conditioned-media and measuring the expression of inflammatory genes. In vivo wound healing effects of fresh and lyophilized cMSC conditioned-media were assessed in a murine model of cornea epithelial injury. Results: Both fresh and lyophilized cMSCs-derived conditioned-medium induced significantly faster closure of in vitro epithelial wounds compared to conditioned-medium from non-MSC cells (P < .0001). Treating stimulated macrophages with fresh or lyophilized cMSCs-derived conditioned-media significantly decreased the expression of inflammatory genes compared to control (P < .0001). Murine corneal epithelial wounds were healed by 87.6 ± 2.7% and 86.2 ± 4.6% following treatment with fresh and lyophilized cMSC conditioned-media, respectively, while the control was healed by 64.7 ± 16.8% (P < .05). Conclusion: Lyophilized cMSC-derived conditioned-medium is as effective as fresh conditioned-medium in promoting wound healing and modulating inflammation. The results of this study support the application of lyophilized cMSCs-derived conditioned-medium, which allows for more extended storage, as a promising non-invasive option in the treatment of corneal wounds.

A surgical skills assessment rubric for pterygium surgery

PURPOSE

To introduce an assessment tool (rubric) for evaluating ophthalmology residents' competency in pterygium surgery.

METHODS

A panel of experienced international surgeons collaborated and developed the rubric. After describing various stages of the procedure, the Dreyfus scale of skill acquisition was used for scoring each stage. After finalizing the rubric, two surgeons independently evaluated 20 masked pterygium surgery videos of 10 residents and scored the videos according to the rubric. The agreement between the scores of them was examined with the intra-class correlation coefficient test.

RESULTS

This rubric divides pterygium surgery into 13 different stages and covers the two most common techniques of pterygium surgery; conjunctival autograft and amniotic membrane transplant. The rubric showed face and content validity. Overall, an intraclass correlation coefficient of 0.90 (95% confidence interval 0.76-0.96, P < 0.001) was achieved between the two surgeons. The residents scored significantly higher on surgeries performed later in their rotation compared to the earlier surgeries (4.32 ± 0.35 vs 3.96 ± 0.31, P = 0.006). Certain stages of pterygium surgery were more strongly correlated with the residents' past pterygium surgical experience.

CONCLUSION

This study introduces an international rubric for assessing competency in pterygium surgery. In addition to face and content validity, this rubric shows high inter-rater reliability. This may be a useful tool for teaching and measuring competency in pterygium surgery.

Reproducible Derivation and Expansion of Corneal Mesenchymal Stromal Cells for Therapeutic Applications

Purpose

A reproducible protocol for the production of corneal mesenchymal stem/stromal cells (cMSCs) is necessary for potential clinical applications. We aimed to describe successful generation and expansion of cMSCs using an explant method.

Methods

Corneoscleral rims of human cadaveric eyes were divided into four pieces and used as explants to allow outgrowth of cMSCs (passage 0, or P0). The cells were subcultured at a 1:10 ratio until passage 5 (P5). The characteristics as well as therapeutic effects of expanded cMSCs were evaluated both in vitro, using a scratch assay, and in vivo using epithelial debridement and chemical injury mouse models.

Results

All explants demonstrated outgrowth of cells by 7 days. Although the initial outgrowth included mixed mesenchymal and epithelial cells, by P1 only cMSCs remained. By subculturing each flask at a ratio of 1:10, the potential yield from each cornea was approximately 12 to 16 × 10¹⁰ P5 cells. P5 cMSCs demonstrated the cell surface markers of MSCs. The secretome of P5 cMSCs induced faster closure of wounds in an in vitro scratch assay. Subconjunctival injection of P5 cMSCs in mouse models of mechanical corneal epithelial debridement or ethanol injury led to significantly faster wound healing and decreased inflammation, relative to control.

Conclusions

cMSCs can be reproducibly derived from human cadaveric corneas using an explant method and expanded with preservation of characteristics and corneal wound healing effects.

Translational Relevance

The results of our study showed that cMSCs produced using this scheme can be potentially used for clinical applications.

Management of Congenital Aniridia-Associated Keratopathy: Long-Term Outcomes from a Tertiary Referral Center

PURPOSE

To report the outcomes of medical and surgical management for congenital aniridia-associated keratopathy (AAK) over a long-term follow-up period.

DESIGN

Retrospective, comparative case series.

METHODS

Medical records of patients diagnosed with congenital aniridia were retrospectively reviewed. Age, sex, ethnicity, follow-up time, AAK stage, noncorneal abnormalities, ocular surgeries, and complications were recorded. The visual acuity equivalent (VAE), approximate Early Treatment Diabetic Retinopathy Study (appETDRS) letter score, was calculated using recorded Snellen visual acuities.

RESULTS

A total of 92 eyes of 47 patients (31 females) with mean age of 48.0 ± 18.0 years and mean follow-up of 78.6 ± 42.2 months were included. At the initial visit, 12 eyes (13%) were classified as Stage I AAK, 33 eyes (35.9%) were Stage II, 25 eyes (27.2%) were Stage III, 17 eyes (18.5%) were Stage IV, and 5 eyes (5.4%) were Stage V. Limbal stem cell transplantation (LSCT) and Boston keratoprosthesis (KPro) were frequently performed in eyes with Stages III-V. These advanced corneal surgeries significantly improved the median (95% confidence interval [CI]) of calculated appETDRS scores from 2 (0-20) to 26 (15-41) (Snellen values, 20/20,000 to 20/300; P = 0.0004). Patients with earlier Stages (I-II) of AAK were managed medically and had stable visual acuity through their final visits (appETDRS score of 26 [20-35] to 35 [26-35]; Snellen, 20/300 to 20/200; P > 0.05). The appETDRS VAE was significantly improved from 20 (0-35) to 30 (20-55), Snellen, 20/400 to 20/250, following LSCT (P = 0.021) and from 2 (0-20) to 2 (0-41) after KPro; Snellen, 20/20,000 VAE but with improved 95% CI after follow-up (P = 0.019).

CONCLUSIONS

With proper characterization and staging of AAK, individualized medical and advanced surgical interventions preserves and improves visual acuity.