Long-Term Effects of Adipose-Derived Stem Cells for the Treatment of Bilateral Limbal Stem Cell Deficiency

PURPOSE

To determine the safety and feasibility of human autologous adipose tissue-derived adult mesenchymal stem cells (ASCs) for ocular surface regeneration in patients with bilateral limbal stem-cell deficiency (LSCD).

METHODS

A phase IIa clinical trial was designed (https://Clinicaltrials.gov, NCT01808378) with 8 patients, 3 of whom had aniridia, 2 meibomian glands diseases, 2 multiple surgeries and 1 chronic chemical injury. The therapeutic protocol was as follows: 6-mm of central corneal epithelium was removed, 400,000 ASCs were injected into each limboconjunctival quadrant, 400,000 ASCs were suspended over the cornea for 20 min, and finally the cornea was covered with an amniotic membrane patch.

RESULTS

No adverse events were detected after a mean of 86,5 months of follow-up. One year after surgery, 6 of the 8 transplants were scored as successful, five patients had improved uncorrected visual acuity (mean of 12 letters), two patients presented epithelial defects (also present at baseline) and the mean percentage of corneal neovascularization was of 28.75% (36.98%, at baseline). Re-examination 24 months after treatment disclosed preserved efficacy in 4 patients. At the last visit (after a mean of 86,5 months of follow up) epithelial defects were absent in all patients although improvement in all of the variables was only maintained in patient 3 (meibomian glands agenesia).

CONCLUSION

ASCs are a feasible and conservative therapy for treating bilateral LSCD. The therapeutic effect differs between etiologies and diminishes over time.

Neovascularization against autologous SLET donor grafts despite successful corneal epithelialization and graft adherence

PURPOSE

To report a case of neovascularization against autologous grafts after simple limbal epithelial transplantation (SLET) despite successful corneal epithelialization, as well as its subsequent regression without intervention.

METHODS

A case report and review of the literature.

RESULTS

A 52-year-old woman underwent uncomplicated autologous SLET for asymmetric limbal stem cell deficiency (LSCD) in the left eye. One month after the surgery, the patient had successful adherence of the graft and corneal epithelialization; however, new neovascularization developed in the left eye towards the graft sites. With only a slow taper of topical prednisolone acetate and polymyxin b/trimethoprim, the neovascularization regressed to ghost vessels over the following three months with improvement of her LSCD symptoms and increased clarity of her cornea.

CONCLUSION

The limbus does not enjoy relative immune privilege like other parts of the eye; therefore, autologous limbal stem cell transplantation (along with the minimal immune response generated) is valuable for restoration of the ocular surface. Here, we describe neovascularization against autologous donor grafts despite an otherwise uncomplicated surgery and expected epithelialization course. Inflammation-mediated angiogenesis likely initiated the neovascularization, suggesting that immune mediators of inflammation may be inadvertently part of the graft tissue in bilateral LSCD.

Quintuple Procedure for Ocular Surface Reconstruction and Visual Rehabilitation

PURPOSE

The aim of this study was to describe a combined surgical approach for ocular surface and visual rehabilitation in patients with limbal stem cell deficiency, corneal scarring, and cataract. We aimed to introduce this combined approach as an alternative to a staged approach and to describe the intraoperative use of a diamond ophthalmic burr (DOB) and optical coherence tomography (OCT) to achieve and confirm a smooth graft-host interface during the anterior lamellar keratoplasty (ALK) portion of the procedure.

METHODS

The quintuple procedure described herein consists of a modified ALK, cataract extraction, intraocular lens implantation, simple limbal epithelial transplantation, and temporal tarsorrhaphy. Intraoperative OCT and DOB were used to guide the creation of the stromal bed during the ALK. The procedure was performed in a patient with limbal stem cell deficiency and corneal scarring after a chemical ocular burn.

RESULTS

The tarsorrhaphy was removed at 3 months postoperatively once complete corneal epithelialization was observed. The best-corrected visual acuity improved from light perception preoperatively to 20/30 at 16 months postoperatively with the use of scleral contact lenses. At this postoperative time point, the cornea was clear and compact, and the ocular surface was stable.

CONCLUSIONS

The quintuple procedure allowed for visual and ocular surface rehabilitation in cases in which follow-up for a staged approach was not possible. Intraoperative OCT allowed for real-time visualization and dissection of the stromal bed, whereas the use of the DOB helped achieve a smooth stromal surface for an optimal graft-host interface.

Matrix-Assisted Cell Transplantation for the Treatment of Limbal Stem Cell Deficiency in a Rabbit Model

With the development of regenerative medicine in ophthalmology, the identification of cells with high proliferative potential in the limbal area has attracted the attention of ophthalmologists and offered a new option for treatment in clinical practice. Limbal stem cell deficiency (LSCD) is an identified eye disease with a difficult and negative outcome, for which the traditional treatment is keratoplasty. This study sought to evaluate the efficacy of matrix-assisted cell transplantation consisting of in vitro-cultured autologous limbal stem cells (LSCs) and type I collagen for the treatment of LSCD in rabbits. LSCD was induced in 10 rabbits by a combination of mechanical limbectomy and alkali burns. Cells were cultured on a plate for 14 days before being transferred to a collagen-based matrix for another 7 days. Rabbits were divided into two groups as follows: the experimental group (five rabbits) received matrix-assisted cell transplantation, while the control group (five rabbits) received only conservative therapy with anti-inflammatory eye drops. During the postoperative period, all rabbits were examined using slit-lamp biomicroscopy with photo-registration and fluorescent staining, impression cytology and anterior segment optical coherence tomography (AS-OCT). Rabbits were euthanized at 30 and 120 days, and their corneas were processed for histology and immunohistochemistry. As a consequence, rabbits in the experimental group demonstrated the restoration of the corneal epithelium and transparency without epithelial defects. Moreover, goblet cells were absent in the central zone of the corneal epithelium. In conclusion, our new method of treatment enhanced the corneal surface and is an effective method of treatment for LSCD in rabbits.

Corneal Epithelial Development and the Role of Induced Pluripotent Stem Cells for Regeneration

Severe corneal disorders due to infective aetiologies, trauma, chemical injuries, and chronic cicatricial inflammations, are among vision-threatening pathologies leading to permanent corneal scarring. The whole cornea or lamellar corneal transplantation is often used as a last resort to restore vision. However, limited autologous tissue sources and potential adverse post-allotransplantation sequalae urge the need for more robust and strategic alternatives. Contemporary management using cultivated corneal epithelial transplantation has paved the way for utilizing stem cells as a regenerative potential. Humaninduced pluripotent stem cells (hiPSCs) can generate ectodermal progenitors and potentially be used for ocular surface regeneration. This review summarizes the process of corneal morphogenesis and the signaling pathways underlying the development of corneal epithelium, which is key to translating the maturation and differentiation process of hiPSCs in vitro. The current state of knowledge and methodology for driving efficient corneal epithelial cell differentiation from pluripotent stem cells are highlighted.

A Review of Contact Lens-Induced Limbal Stem Cell Deficiency

Limbal stem cell deficiency (LSCD) is a pathologic condition caused by the dysfunction and destruction of stem cells, stem cell precursors and limbal cell niche in the corneal epithelium, leading to severe conjunctivalization of the cornea. Etiologies for LSCD span from congenital (aniridia), traumatic (chemical or thermal injuries), autoimmune (Stevens-Johnson syndrome) and iatrogenic disease to contact lens (CL) wear. Of these, CL wear is the least understood and is often a subclinical cause of LSCD. Even with recent advances in LSCD research, limitations persist in establishing the pathogenesis and treatment guidelines for CL-induced LSCD. A literature search was conducted to include original articles containing patients with CL-induced LSCD. This review will critically discuss the complex pathophysiology behind CL-induced LSCD, the underlying risk factors and epidemiology of the disease as well as methods to obtain a diagnosis. Various treatment options will be reviewed based on proposed treatment strategies.

Latent diffusion augmentation enhances deep learning analysis of neuro-morphology in limbal stem cell deficiency

Introduction

Limbal Stem Cell Deficiency (LSCD) is a blinding corneal disease characterized by the loss of function or deficiency in adult stem cells located at the junction between the cornea and the sclera (i.e., the limbus), namely the limbal stem cells (LSCs). Recent advances in in vivo imaging technology have improved disease diagnosis and staging to quantify several biomarkers of in vivo LSC function including epithelial thickness measured by anterior segment optical coherence tomography, and basal epithelial cell density and subbasal nerve plexus by in vivo confocal microscopy. A decrease in central corneal sub-basal nerve density and nerve fiber and branching number has been shown to correlate with the severity of the disease in parallel with increased nerve tortuosity. Yet, image acquisition and manual quantification require a high level of expertise and are time-consuming. Manual quantification presents inevitable interobserver variability.

Methods

The current study employs a novel deep learning approach to classify neuron morphology in various LSCD stages and healthy controls, by integrating images created through latent diffusion augmentation. The proposed model, a residual U-Net, is based in part on the InceptionResNetV2 transfer learning model.

Results

Deep learning was able to determine fiber number, branching, and fiber length with high accuracy (R2 of 0.63, 0.63, and 0.80, respectively). The model trained on images generated through latent diffusion on average outperformed the same model when trained on solely original images. The model was also able to detect LSCD with an AUC of 0.867, which showed slightly higher performance compared to classification using manually assessed metrics.

Discussion

The results suggest that utilizing latent diffusion to supplement training data may be effective in bolstering model performance. The results of the model emphasize the ability as well as the shortcomings of this novel deep learning approach to predict various nerve morphology metrics as well as LSCD disease severity.

Long-Term Comprehensive Management of Bilateral Limbal Stem Cell Deficiency Secondary to Severe Chemical Burn: 10 Years of Follow-Up

PURPOSE

To describe the long-term management of bilateral limbal stem cell deficiency secondary to a severe chemical burn.

METHODS

Descriptive case report.

IMPORTANCE

This case highlights the importance of early intervention in ocular chemical burns for the preservation of tissue integrity and avoidance of perforation. We also review the use of proper ocular surface reconstructive techniques to restore the function of the limbal area, as well as the immunomodulatory strategies and follow-up needed for these interventions.

Gene expression signatures of human senescent corneal and conjunctival epithelial cells

PURPOSE

This study aimed to investigate the senescent phenotypes of human corneal and conjunctival epithelial cells.

METHODS

We examined cell morphology, senescence-associated β-galactosidase (SA-β-gal) activity, cell proliferation, and expression of senescence markers (p16 and p21). RNA sequencing analysis was conducted to compare gene expression profiles between senescent and non-senescent cells. Finally, the potential involvement of senescent cells in the pathogenesis of ocular surface diseases was investigated.

RESULTS

X-irradiated corneal and conjunctival epithelial cells exhibited typical senescence phenotypes, i.e., flattened morphologies, increased SA-β-gal activity, decreased cell proliferation, and increased expression of senescence markers, p16 and p21. RNA-seq analysis revealed substantial differences in gene expression profiles between senescent corneal (SCo) and conjunctival epithelial cells (SCj). Moreover, SCj were detected in pathological conjunctival tissues associated with limbal stem cell deficiency (LSCD) due to Stevens-Johnson syndrome or chemical burns, potentially being involved in abnormal differentiation.

CONCLUSION

This study highlights the cellular and molecular characteristics of senescent ocular surface cells, particularly in SCj that show abnormal keratin expression, and their potential roles in severe ocular surface diseases and pathology.

Conjunctival Limbal Autograft Combined with Amnion-Assisted Conjunctival Epithelial Redirection for Unilateral Total Limbal Stem Cell Deficiency after Severe Chemical Burn

(1) Background: To evaluate the efficacy of conjunctival limbal autograft (CLAU) combined with the amnion-assisted conjunctival epithelial redirection (ACER) procedure for patients with unilateral total limbal stem cell deficiency (LSCD) caused by severe chemical burn. (2) Methods: A retrospective interventional case series of unilateral total LSCD after chemical burn who underwent CLAU combined with ACER surgery between September 2021 and July 2023 was collected. Outcome measures included epithelialization of the cornea with donor limbus-derived epithelium, best corrected visual acuity (BCVA), and complications. (3) Results: Nine males and one female were included in this study. The mean age was 40.9 ± 9.63 (range, 26 to 55) years. The average duration between injury and CLAU combined with the ACER procedure was 7.67 ± 3.97 (range, 4 to 18) months. All patients achieved corneal epithelialization and improved BCVA. Postoperative complications occurred in four cases, including delayed corneal epithelial healing in one case, delayed amniotic membrane dissolution and detachment in two cases, and recurrence of symblepharon in one case. No complications were noted in the healthy donor eyes. (4) Conclusions: CLAU combined with ACER is a safe and effective treatment for unilateral total LSCD caused by severe chemical burn. This combined surgery restores visual function for patients with corneal blindness caused by chemical burn, reducing the burden on the families and society.

Advances in cell transplantation therapy for limbal stem cell deficiency

BACKGROUND

Limbal stem cells (LSCs) are essential for maintaining corneal transparency and ocular surface integrity. Many external factors or genetic diseases can lead to corneal limbal stem cell deficiency (LSCD), resulting in the loss of barrier and corneal epithelial cell renewal functions. Stem cell transplantation is one of the primary treatments for LSCD, including limbal transplantation and cultivated limbal epithelial transplantation. In addition, a variety of non-limbal stem cell lines have been experimented with for LSCD treatment. Biological scaffolds are also used to support in vitro stem cell culture and transplantation. Here, we review the mechanisms of corneal maintenance by LSCs, the clinical stage and surgical treatment of LSCD, the source of stem cells, and the biological scaffolds required for in vitro culture.

METHODS

This study is a narrative retrospective study aimed at collecting available information on various aspects of surgical treatments for LSCD. Relevant literature was searched in a range of online databases, including Web of Science, Scopus, and PubMed from 2005 to March, 2023.

RESULTS

A total of 397 relevant articles were found, and 49 articles with strong relevance to the studies in this paper were obtained and analyzed. Moreover, 11 of these articles were on the concept of LSCD and the mechanism of LESCs maintaining the corneal epithelium, 3 articles on the staging and grading of LSCD, 17 articles on cell transplantation methods and donor cell sources, and 18 articles on scaffolds for delivering stem cells. We also summarized the advantages and disadvantages of different cell transplantation methods and the benefits and limitations of scaffolds based on the above literature.

CONCLUSION

The treatment of LSCD is determined by the clinical stage and whether it involves monocular or binocular eyes. Appropriate surgical techniques should be taken for LSCD patients in order to reconstruct the ocular surface, relieve symptoms, and restore visual function. Meanwhile, biological scaffolds assist in the ex vivo culture and implantation of stem cells.

Opposing Roles of Blood-Borne Monocytes and Tissue-Resident Macrophages in Limbal Stem Cell Damage after Ocular Injury

Limbal stem cell (LSC) deficiency is a frequent and severe complication after chemical injury to the eye. Previous studies have assumed this is mediated directly by the caustic agent. Here we show that LSC damage occurs through immune cell mediators, even without direct injury to LSCs. In particular, pH elevation in the anterior chamber (AC) causes acute uveal stress, the release of inflammatory cytokines at the basal limbal tissue, and subsequent LSC damage and death. Peripheral C-C chemokine receptor type 2 positive/CX3C motif chemokine receptor 1 negative (CCR2+ CX3CR1-) monocytes are the key mediators of LSC damage through the upregulation of tumor necrosis factor-alpha (TNF-α) at the limbus. In contrast to peripherally derived monocytes, CX3CR1+ CCR2- tissue-resident macrophages have a protective role, and their depletion prior to injury exacerbates LSC loss and increases LSC vulnerability to TNF-α-mediated apoptosis independently of CCR2+ cell infiltration into the tissue. Consistently, repopulation of the tissue by new resident macrophages not only restores the protective M2-like phenotype of macrophages but also suppresses LSC loss after exposure to inflammatory signals. These findings may have clinical implications in patients with LSC loss after chemical burns or due to other inflammatory conditions.

Demographic profile and clinical characteristics of patients presenting with acute ocular burns

Purpose

To study and compare the demographic and clinical profile of acute ocular burns (AOB) in children and adults.

Methods

This retrospective case series included 271 children (338 eyes) and 1300 adults (1809 eyes) who presented to two tertiary eye care centers within one month of sustaining AOB. Data regarding demographics, causative agents, severity of injury, visual acuity (VA), and treatment were collected and analyzed.

Results

Males were more commonly affected particularly among adults (81% versus 64%, P < 0.00001). Among children, 79% sustained domestic injuries, whereas 59% of adults had work-place injuries (P < 0.0001). Most cases were due to alkali (38%) and acids (22%). Edible lime (chuna, 32%), superglue (14%), and firecrackers (12%) in children, and chuna (7%), insecticides, lye, superglue (6% each), toilet cleaner (4%) and battery acid (3%) in adults, were the main causative agents. The percentage of cases with Dua grade IV-VI was greater in children (16% versus 9%; P = 0.0001). Amniotic membrane grafting and/or tarsorrhaphy were needed in 36% and 14% of affected eyes in children and adults, respectively (P < 0.00001). The median presenting VA was logMAR 0.5 in children and logMAR 0.3 in adults (P = 0.0001), which improved significantly with treatment in both groups (P < 0.0001), but the final VA in eyes with Dua grade IV-VI burns was poorer in children (logMAR 1.3 versus logMAR 0.8, P = 0.04).

Conclusion

The findings clearly delineate the at-risk groups, causative agents, clinical severity, and treatment outcomes of AOB. Increased awareness and data-driven targeted preventive strategies are needed to reduce the avoidable ocular morbidity in AOB.

The Multifold Etiologies of Limbal Stem Cell Deficiency: A Comprehensive Review on the Etiologies and Additional Treatment Options for Limbal Stem Cell Deficiency

Given the various ocular manifestations of limbal stem cell insufficiency, an awareness of the genetic, acquired, and immunological causes and associated additional treatments of limbal stem cell deficiency (LSCD) is essential for providers. We performed a comprehensive review of the literature on the various etiologies and specific therapies for LSCD. The resources utilized in this review included Medline (PubMed), Embase, and Google Scholar. All English-language articles and case reports published from November 1986 through to October 2022 were reviewed in this study. There were collectively 99 articles on these topics. No other exclusion criteria were applied. Depending on the etiology, ocular manifestations of limbal stem cell deficiency range from dry eye syndrome and redness to more severe outcomes, including corneal ulceration, ocular surface failure, and vision loss. Identifying the source of damage for LSCD is critical in the treatment process, given that therapy may extend beyond the scope of the standard protocol, including artificial tears, refractive surgery, and allogeneic stem cell transplants. This comprehensive review of the literature demonstrates the various genetic, acquired, and immunological causes of LSCD and the spectrum of supplemental therapies available.

Early Clinical Outcomes of the First Commercialized Human Autologous Ex Vivo Cultivated Oral Mucosal Epithelial Cell Transplantation for Limbal Stem Cell Deficiency: Two Case Reports and Literature Review

The first product in the world for ex vivo cultivated oral mucosal epithelial cell transplantation (COMET) to treat limbal stem cell deficiency (LSCD), named Ocural^®, was launched in June 2021 in Japan. COMET was performed on two patients, including the first case in the post-marketing phase of Ocural^®. Pathological and immunohistochemical examinations were also carried out using specimens obtained before and after COMET and the spare cell sheet. In case 1, the ocular surface remained free from epithelial defects for approximately six months. In case 2, although defect of the cornea-like epithelia was observed after COMET for one month, it was resolved after the insertion of lacrimal punctal plugs. In case 1, adjuvant treatment was interrupted due to an accident during the second month after COMET, resulting in conjunctival ingrowth and corneal opacity. Eventually, a lamellar keratoplasty was required at six months after COMET. Immunohistochemistry revealed the presence of markers for stem cells (p63, p75), proliferation (Ki-67), and differentiation (Keratin-3, -4, and -13) in both the cornea-like tissue after COMET and a cultivated oral mucosal epithelial cell sheet. In conclusion, Ocural^® can be accomplished without major complications, and the stem cells derived from oral mucosa might be successfully engrafted.

A novel case of limbal stem cell deficiency in a patient with acrodermatitis enteropathica

An 18-year-old male diagnosed with acrodermatitis enteropathica (AE) since early childhood presented with worsening of dermatitis along with photophobia and watering in both eyes. Systemic evaluation by dermatology and gastroenterology specialists confirmed a diagnosis of acute exacerbation of AE, and oral zinc supplements were initiated. A best-corrected visual acuity of 20/20 was documented in both eyes. Slit-lamp examination revealed bilateral subepithelial corneal opacities in a radial fan-like pattern extending from the superior limbus toward the center. A whorled appearance of fluorescein staining and small epithelial erosions was noted in both eyes. Ocular involvements in AE such as blepharitis, cataracts, and radial corneal opacities have been reported previously. We report a new association of AE with limbal stem cell deficiency with its classical features of linear subepithelial corneal opacities with a whorling uptake of fluorescein stain and corneal erosions.

Pathogenesis of Alkali Injury-Induced Limbal Stem Cell Deficiency: A Literature Survey of Animal Models

Limbal stem cell deficiency (LSCD) is a debilitating ocular surface disease that eventuates from a depleted or dysfunctional limbal epithelial stem cell (LESC) pool, resulting in corneal epithelial failure and blindness. The leading cause of LSCD is a chemical burn, with alkali substances being the most common inciting agents. Characteristic features of alkali-induced LSCD include corneal conjunctivalization, inflammation, neovascularization and fibrosis. Over the past decades, animal models of corneal alkali burn and alkali-induced LSCD have been instrumental in improving our understanding of the pathophysiological mechanisms responsible for disease development. Through these paradigms, important insights have been gained with regards to signaling pathways that drive inflammation, neovascularization and fibrosis, including NF-κB, ERK, p38 MAPK, JNK, STAT3, PI3K/AKT, mTOR and WNT/β-catenin cascades. Nonetheless, the molecular and cellular events that underpin re-epithelialization and those that govern long-term epithelial behavior are poorly understood. This review provides an overview of the current mechanistic insights into the pathophysiology of alkali-induced LSCD. Moreover, we highlight limitations regarding existing animal models and knowledge gaps which, if addressed, would facilitate development of more efficacious therapeutic strategies for patients with alkali-induced LSCD.

Keratoprosthesis in dry eye disease

Bilateral corneal blindness with severe dry eye disease (DED), total limbal stem cell deficiency with underlying corneal stromal scarring and vascularization, combined with adnexal complications secondary to chronic cicatrizing conjunctivitis is a highly complex situation to treat. In such eyes, procedures such as penetrating keratoplasty alone or combined with limbal stem cell transplantation are doomed to fail. In these eyes, keratoprosthesis (Kpro) or an artificial cornea is the most viable option, eliminating corneal blindness even in eyes with autoimmune disorders such as Stevens-Johnson syndrome, ocular mucous membrane pemphigoid, Sjogren's syndrome, and nonautoimmune disorders such as chemical/thermal ocular burns, all of which are complex pathologies. Performing a Kpro in these eyes also eliminates the need for systemic immunosuppression and may provide relatively early visual recovery. In such eyes, the donor cornea around the central cylinder of the Kpro needs to be covered with a second layer of protection to avoid desiccation and progressive stromal melt of the underlying cornea, which is a common complication in eyes with severe DED. In this review, we will focus on Kpro designs that have been developed to survive in eyes with the hostile environment of severe DED. Their outcomes in such eyes will be discussed.

E-PIX: An enhanced grading for acute ocular burns

An enhanced online and manual grading system, based on the I's and E's, for acute ocular chemical injuries is being proposed. E-PIX is designed to be an online/manual grading system that includes all the parameters that adversely affect the outcome of acute chemical injuries. The importance of addressing the I's and E's in chemical burns cannot be underestimated. These include the need for the documentation and management of epithelial defect (E), intraocular pressure (P) (IOP), ischemia (scleral) (I), and exposure (X) (acronym - E-PIX). Epithelial defect includes that involving the limbus (L), along with conjunctival (C), corneal (K), and tarsal (T). These additional parameters are graded and represented as an annotation along with the limbal grade providing a comprehensive grading for the injury. A manual entry sheet and a freely accessible online grade generator are a part of the system. The proposed enhanced grading offers a final annotation that provides a clear understanding of all factors that can lead to vision-threatening complications ensuring their assessment and hence subsequently their addressal to improve outcomes, if abnormal. The prognostication continues to be based on the grade of limbal involvement. The additional annotations impact prognosis and outcome if not addressed. Including the laterality of injury provides, in addition, a futuristic understanding of available options. The grade generator retains the flexibility to be dynamic with changes reflecting upon the healing process in the acute stage. The proposed system aims to provide primary and tertiary caregivers alike with a uniform grading system.

Dry eye disease in head and neck cancer patients undergoing radiotherapy

Purpose

To study the incidence of dry eye disease (DED) in head and neck cancer (HNC) patients undergoing external beam radiotherapy (EBRT), to find a correlation between tumor location and total radiation dose with DED, and to report various radiotherapy (RT) induced acute toxic effects on ocular and adnexal structures.

Methods

A prospective cohort study was conducted at a tertiary eye-care center on 90 patients of HNC undergoing EBRT from March 2021 to May 2022. All underwent a thorough clinical history and complete ophthalmological examination including an ocular surface disease index (OSDI) questionnaire, visual acuity, anterior segment, angle and posterior segment examination, dry eye workup including the Schirmer test, tear meniscus height, tear break-up time, corneal fluorescein staining and grading, and meibography by auto-refractometer and its scoring at each visit. Patients were evaluated before the start of RT and then at 1 week, 4 weeks, and 12 weeks post-RT. Radiation records of all patients were noted. Data were analyzed using percentage and Microsoft Excel.

Results

Of the 90 patients, 66 were male and 24 female (M: F ratio of 2.75) with a median age of 52.5 years (range 24 to 80 years). The most common HNC was the carcinoma oral cavity and lip. Most patients received a total radiation dose between 46 to 55 Gy. DED developed in 48 (53.3%) patients. The incidence of DED increased with the increase in total radiation dose (r = 0.987). DED was also found to be correlated with tumor location (r = 0.983).

Conclusion

The incidence of DED positively correlated with the total radiation dose and tumor location.

Derivation of Limbal Stem Cells from Human Adult Mesenchymal Stem Cells for the Treatment of Limbal Stem Cell Deficiency

Approximately 10 million individuals have blindness due to limbal stem cell (LSCs) deficiency, one of the most challenging problems in ophthalmology. To replenish the LSC pool, an autologous extraocular cell source is appropriate, thereby avoiding the risk of immune rejection, the need for immunosuppression and the risk of damaging the contralateral eye. In recent years, adipose-derived mesenchymal stem cells (ADSCs) have been a key element in ocular regenerative medicine. In this study, we developed a protocol for deriving human LSCs from ADSCs compatible with the standard carrier human amniotic membrane, helping provide a stem cell pool capable of maintaining proper corneal epithelial homeostasis. The best protocol included an ectodermal induction step by culturing ADSCs with media containing fetal bovine serum, transforming growth factor-β inhibitor SB-505124, Wnt inhibitor IWP-2 and FGF2 for 7 days, followed by an LSC induction step of culture in modified supplemental hormonal epithelial medium supplemented with pigment epithelium-derived factor and keratinocyte growth factor for 10 additional days. The optimal differentiation efficiency was achieved when cells were cultured in this manner over vitronectin coating, resulting in up to 50% double-positive αp63/BMI-1 cells. The results of this project will benefit patients with LSC deficiency, aiding the restoration of vision.

Allogeneic Limbal Transplants Integrate into the Corneal Surface and Lead to an Improved Visual Acuity

Limbal stem cell deficiency (LSCD) severely impairs vision and can lead to blindness. LSCD causes include chemical burns, infections, multiple previous operations and congenital malformations. Allogeneic limbal transplantation is a procedure for treating LSCD where prepared limbal tissue is attached using a double running suture during allogeneic penetrating keratoplasty (PKP). A total of 22 patients underwent ALT surgery between February 2019 and June 2022 at the University Hospital Halle (Saale). Regular follow-up was performed postoperatively every three months and included visual acuity testing, pressure measurement, slit lamp microscopic examination, fundoscopy, corneal topography and anterior segment optical coherence tomography (AS-OCT). The mean patient age was 69.5 years, and the mean follow-up was 19 months. All included patients had LSCD and multiple previous surgeries. Patient LSCD etiology was 59% infectious and 41% traumatic. ALTs integrated into corneal surfaces in all patients, demonstrated on AS-OCT. Since most patients initially received allogeneic limbal transplants, none of the operated eyes had surgical complications. Overall, visual acuity improved postoperatively from an initial 2.06 to 1.44 logarithm of the minimum angle of resolution (logMAR). Allogeneic limbal transplantation can be used to treat LSCD and its integration into the surrounding corneal tissue can be observed on AS-OCT.

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.

Diagnostic Algorithm for Surgical Management of Limbal Stem Cell Deficiency

BACKGROUND

Limbal stem cell deficiency (LCSD) presents several challenges. Currently, there is no clearly defined systematic approach to LSCD diagnosis that may guide surgical tactics.

METHODS

The medical records of 34 patients with LSCD were analyzed. Diagnostic modalities included standard (visometry, tonometry, visual field testing, slit-lamp biomicroscopy with corneal fluorescein staining, Schirmer test 1, ultrasonography) and advanced ophthalmic examination methods such as anterior segment optical coherence tomography, in vivo confocal microscopy, impression cytology, and enzyme-linked immunoassay.

RESULTS

Standard ophthalmological examination was sufficient to establish the diagnosis of LSCD in 20 (58.8%) cases, whereas advanced evaluation was needed in 14 (41.2%) cases. Depending on the results, patients with unilateral LSCD were scheduled to undergo glueless simple limbal epithelial transplantation (G-SLET) or simultaneous G-SLET and lamellar keratoplasty. Patients with bilateral LSCD with normal or increased corneal thickness were enrolled in the paralimbal oral mucosa epithelium transplantation (pLOMET) clinical trial.

CONCLUSIONS

Based on the diagnostic and surgical data analyzed, the key points in LSCD diagnosis were identified, helping to guide the surgeon in selecting the appropriate surgical procedure. Finally, we proposed a novel step-by-step diagnostic algorithm and original surgical guidelines for the treatment of patients with LSCD.

Severe chemical eye injuries - clinical outcomes and associated socio-economic factors

Aims

To describe clinical outcomes, management, and socio-economic impact of severe acute chemical eye injuries in a tertiary hospital.

Methods

37 patients required emergency admission to the Royal Victoria Infirmary eye ward between April 2013 and September 2015. Demographics, best corrected distance visual acuity (BCDVA), causative agent, degree of limbal stem cell deficiency (LSCD), management and socio-economic data were evaluated.

Results

Mean age on admission was 34.5 years (SD 16.3; range 16-82); 30 males (81.1%); 22 bilateral (59.5%). Causative agent: alkali in 30 cases (81.1%); acid in three cases (8.1%); and unknown in four cases (10.8%). Fifteen cases (40.5%) were assaults, 12 (32.5%) work-related accidents, nine (24.3%) domestic accidents and one (2.7%) undetermined. Eleven patients (29.7%) were unemployed, 18 (48.6%) were labourers, three (8.1%) were students, three (8.1%) were retired and two (5.4%) were professionals. Mean admission time was five days (SD 3.2; range 1-12). Mean follow-up time was 170.5 days (range 1-946). Mean cost of admission was £2478 (range £274-5785). Five patients (13%; seven eyes) developed total or partial limbal stem cell deficiency, all being assaults.

Conclusions

Main causative agent in our study was alkali, with young men in the working age being most frequently involved. Many patients required prolonged hospital admission and costly follow-up. The majority of cases were assaults, mostly occurring in unemployed patients. All the limbal stem cell deficiency cases were due to assaults. We believe that socio-economic factors play an important role in the cause, severity and cost of chemical eye injuries.

Lay Summary

Acute chemical eye injuries have a significant and extensive impact on patients' visual function outcomes and vision-related quality of life, with consequent enormous burden to affected individuals, their families and society. We believe that by understanding the socio-economic environment, we may not only be able to enforce safety measures to tackle the increasing rate of severe chemical eye injuries in our community, but also to develop collaborative programmes with the community, educating the population on the seriousness of chemical eye injuries, and with the local authorities, trying to understand the clustering of assaults in areas and tackling the associated socio-economic risk factors, such as unemployment. Given the increasing rate of assaults using chemicals in recent times, it is also important to assess availability of adequate victim support programmes and develop good interaction with relevant local, regional and national authorities to ensure all aspects of community security service are in place to be able to address any potential deficiencies in line with police and home office guidelines. Keeping in mind that the best action plan is always prevention. However, when an ocular injury does occur it is evident that significant morbidity and visual sequelae can result and affect the socio-economic status of the victims despite our best current medical and surgical care.

Autologous Serum Eye Drops in the Management of Limbal Stem Cell Deficiency Associated With Glaucoma Surgery

PURPOSE

To evaluate safety and efficacy of autologous serum eye drops (AS) in the treatment of limbal stem cell deficiency (LSCD) associated with glaucoma surgery.

METHODS

Retrospective case series of eyes with glaucoma surgery-induced LSCD treated with AS. Diagnosis of LSCD was confirmed by anterior segment optical coherence tomography, in vivo confocal microscopy, and/or impression cytology. Limbal stem cell deficiency severity was staged using a clinical scoring system (2-10 points). Outcome measures were changes (≥2 points) of the LSCD score and best-corrected visual acuity (BCVA) from the baseline to the last follow-up.

RESULTS

Thirteen eyes of 12 consecutive patients treated with 50% AS for at least 3 months were included. The mean age was 78.9±7.5 years and the mean duration of AS use was 20.9±16.8 months. Indications of AS included LSCD progression in eight eyes (61.5%) and visual axis threatening in five eyes (38.5%). The mean LSCD score at baseline (6.7±1.6) was similar to that at last follow-up (6.5±2.2, P =0.625). Two eyes (15.4%) showed improvement, nine eyes (69.2%) were stable, and two eyes (15.4%) worsened. The mean baseline BCVA (0.89±0.64 logMAR) was similar to the mean final BCVA (1.05±0.63 logMAR, P =0.173). There were no serious adverse complications related to AS.

CONCLUSION

AS appears to be well tolerated and may stabilize the progression of LSCD with limited effects. A larger study is necessary to confirm the findings.

Outcome of keratolimbal allograft transplantation with deep anterior lamellar keratoplasty for bilateral limbal stem cell deficiency

OBJECTIVES

To evaluate and compare the outcome of keratolimbal allograft (KLAL) transplantation with or without deep anterior lamellar keratoplasty (DALK) for bilateral severe limbal stem cell deficiency (LSCD).

METHODS

This retrospective review included 49 eyes of 46 patients who underwent KLAL transplantation at the Department of Ophthalmology of Chinese PLA general hospital, 2009-2020, for bilateral severe LSCD were examined for corneal clarity and corneal scarring to determine whether to combine DALK with KLAL transplantation. Preoperative information, surgical decision tree, surgical procedures, and postoperative data were collected for each eye.

RESULTS

All patients had preoperative severe or total LSCD. Twenty-four eyes underwent KLAL transplantation only, 25 KLAL transplantation plus DALK. The mean follow-up was 46.80 ± 31.22 months (18-158 months). Overall KLAL survival (with or without DALK) was 71.43% at the final follow-up (KLAL-only 66.67%, KLAL-DALK 76%). Kaplan-Meier survival analysis showed that the 3-year survival probability of all grafts was 70.53 ± 10.89% (KLAL-only 64.86 ± 10.11%, KLAL-DALK 75.79 ± 8.62%). The proportion of BCVA ≥ 20/200 eyes among all KLAL transplantations increased from 11 eyes (22.45%) preoperatively to 25 eyes (51.02%) after 1 year and 24 eyes (48.98%) at the last follow-up (P = 0.01). The proportion of BCVA ≥ 20/200 eyes in the KLAL-DALK group increased significantly (P = 0.04), from 16.0% at baseline to 48.0% after 1 year to 44.0% at the last follow-up. Seventeen eyes (34.69%) had postoperative complications.

CONCLUSION

KLAL-DALK is an effective option to restore a stable ocular surface and visual acuity rapidly in patients with bilateral, late-stage, severe LSCD.

Therapeutic Strategies for Restoring Perturbed Corneal Epithelial Homeostasis in Limbal Stem Cell Deficiency: Current Trends and Future Directions

Limbal stem cells constitute an important cell population required for regeneration of the corneal epithelium. If insults to limbal stem cells or their niche are sufficiently severe, a disease known as limbal stem cell deficiency occurs. In the absence of functioning limbal stem cells, vision-compromising conjunctivalization of the corneal epithelium occurs, leading to opacification, inflammation, neovascularization, and chronic scarring. Limbal stem cell transplantation is the standard treatment for unilateral cases of limbal stem cell deficiency, but bilateral cases require allogeneic transplantation. Herein we review the current therapeutic utilization of limbal stem cells. We also describe several limbal stem cell markers that impact their phenotype and function and discuss the possibility of modulating limbal stem cells and other sources of stem cells to facilitate the development of novel therapeutic interventions. We finally consider several hurdles for widespread adoption of these proposed methodologies and discuss how they can be overcome to realize vision-restoring interventions.

Perioperative nuances of cataract surgery in ocular surface disorders

Ocular surface disorders (OSDs) constitute a varied spectrum of conditions that could be associated with dryness, compromised limbal status, varying grades of forniceal obliteration, corneal scars, and a possible underlying immune etiology. These associations adversely impact surgical outcomes in the eye. One of the treatable causes of decreased vision in these eyes is cataracts which could be secondary to the disease, its treatment, or age-related. The compromised ocular surface status can interfere with decision-making regarding the technique of cataract surgery, preoperative biometry for intraocular lens (IOL) power calculation, and intraoperative visibility, increasing the possibility of complications and compromising the final visual outcome. The postoperative course can be affected by complications, including melt and infection. Stabilization of the ocular surface by medical or surgical means, and appropriate management of underlying immune etiology, if any, helps improve and maintain a healthy ocular surface, optimizing cataract outcomes. With the help of pre, intra, and postoperative tools and means, such as punctal occlusion, ocular surface reconstruction, systemic immunosuppression, illuminators, capsule staining dyes, optical iridectomy, prosthetic replacement of the ocular surface ecosystem (PROSE) lenses, and others, the visual outcome post-cataract surgery in these eyes can be maximized. This article highlights the nuances of performing cataract surgery in various OSDs and the need to have a comprehensive stepwise approach is emphasized.

Limbal Autograft Stem Cell Transplantation: More Than 20-Year Follow-up

Limbal stem cell deficiency (LSCD) is a very challenging situation and difficult to manage. A great works and ideas were conducted over the past 50 years. Numerous surgical techniques were proposed. We are reporting more than a 20-year follow-up of a case of limbal autograft stem cell transplantation due to LSCD secondary to chemical injury.

Outcome of Lamellar Graft Patching for the Treatment of Noninfectious Corneal Perforations

PURPOSE

The aims of this study were to evaluate the clinical outcome of lamellar graft patching used for treating noninfectious corneal perforations and to determine the clinical factors affecting tectonic integrity.

METHODS

This retrospective study includes a total of 71 eyes of 67 patients who underwent lamellar graft patching for the treatment of corneal perforations due to persistent epithelial defects secondary to limbal stem cell deficiency (LSCD, 21 eyes; 29.6%), peripheral ulcerative keratitis (17 eyes; 23.9%), neurotrophic keratitis due to herpes simplex keratitis (HSK, 14 eyes; 19.7%), and other causes (19 eyes; 26.8%). We evaluated the tectonic integrity of the globe, visual outcomes, and postoperative complications.

RESULTS

Tectonic integrity was achieved in 53 eyes (74.6%). The survival proportions of eyes that achieved clear grafts were 77.8% and 65.2% at 12 and 24 months, respectively. Graft failure was observed in 19 eyes (26.8%). The survival rate of tectonic integrity and eyes that finally achieved a clear graft was significantly worse in eyes with LSCD compared with those without ( P < 0.001). The logarithm of minimal angle resolution improved significantly from 1.79 ± 0.98 to 1.22 ± 0.87 at 12 months and 1.08 ± 0.81 at 24 months. Postoperative complications included cataract formation (32 eyes, 45.1%), intraocular pressure rise (23 eyes, 32.4%), recurrent perforations (15 eyes, 21.1%), infectious keratitis (14 eyes, 19.7%), recurrence of herpes simplex keratitis (7 eyes, 9.9%), and traumatic graft dehiscence (1 eye, 1.4%).

CONCLUSIONS

Lamellar graft patching is an effective and safe surgical treatment for noninfectious corneal perforations; however, careful attention to severe complications is necessary, especially in eyes with LSCD.

Limbal BCAM expression identifies a proliferative progenitor population capable of holoclone formation and corneal differentiation

The corneal epithelium is renowned for high regenerative potential, which is dependent on the coordinated function of its diverse progenitor subpopulations. However, the molecular pathways governing corneal epithelial progenitor differentiation are incompletely understood. Here, we identify a highly proliferative limbal epithelial progenitor subpopulation characterized by expression of basal cell adhesion molecule (BCAM) that is capable of holocone formation and corneal epithelial sheet generation. BCAM-positive cells can be found among ABCB5-positive limbal stem cells (LSCs) as well as among ABCB5-negative limbal epithelial cell populations. Mechanistically, we show that BCAM is functionally required for cellular migration and differentiation and that its expression is regulated by the transcription factor p63. In aggregate, our study identifies limbal BCAM expression as a marker of highly proliferative corneal epithelial progenitor cells and defines the role of BCAM as a critical molecular mediator of corneal epithelial differentiation.

Using scRNA sequencing of ABCB5-positive human limbal stem cells, Sasamoto et al. identify a BCAM-positive highly proliferative limbal epithelial progenitor subpopulation that is capable of holocone formation and corneal epithelial sheet generation. BCAM regulated by the stem cell transcription factor p63 is functionally required for corneal cell migration and differentiation.

Cytokeratin 13 Is a New Biomarker for the Diagnosis of Limbal Stem Cell Deficiency

PURPOSE

The purpose of this study was to evaluate the expression of cytokeratin (K) 13 on the corneal surface and to validate its application in the diagnosis of limbal stem cell deficiency (LSCD).

METHODS

This prospective comparative study included 26 corneal impression cytology (IC) specimens from patients diagnosed with LSCD. Twenty-three IC specimens from normal donors served as controls. K12 and K13 expression were detected on the IC specimens by immunohistochemistry study. The number of K12 + or K13 + cells in all areas of the IC was quantified using ImageJ software.

RESULTS

The epithelial cells harvested from IC specimens from control corneas were all K12 + . In eyes with LSCD, K13 + and K12 + /K13 + cells accounted for 93.8% and 2.6%, respectively, in the cornea. In eyes with sectoral LSCD, the median number of K13 + cells in the clinically affected area was higher than that in the unaffected area (810.0 vs. 115.0 cells/mm 2 ; P < 0.001). No significant correlation was found between the LSCD severity and the number of K12 + cells (r = -0.284, P = 0.16) or K13 + cells (r = -0.011, P = 0.95). The presence of at least 16 K13 + cells/mm 2 was suggestive of LSCD.

CONCLUSIONS

Identification of K13 + cells on IC specimens provides a simple and reliable method to detect conjunctival epithelial cells on the cornea. K13 is a marker for diagnosing LSCD and localizing the involved area in sectoral LSCD.

Ocular manifestations in Kindler syndrome

We aimed describe the chronic ocular sequelae of Kindler syndrome. All cases of Kindler syndrome with ocular involvement that presented to a tertiary eye care center were included. Three cases of Kindler syndrome with ocular changes were reviewed. Case 1 (10 years, female) had recurrent epithelial breakdown with severe dry eye and corneal opacity secondary to keratitis. Case 2 (28 years, male) had symblepharon , ocular surface keratinization , and severe dry eye. Case 3 (16 years , female ) had partial limbal stem cell deficiency with dry eye. All cases were treated with topical lubricants, short course of low-potency steroids and immuno-modulators. Attention must be paid to the eye in addition to the oro-an-genital mucosa to avoid longterm ocular sequelae.

Outcomes of Human Leukocyte Antigen-Matched Allogeneic Cultivated Limbal Epithelial Transplantation in Aniridia-Associated Keratopathy-A Single-Center Retrospective Analysis

PURPOSE

To assess the efficacy and safety of human leukocyte antigen-matched allogeneic cultivated limbal epithelial stem cell grafts in the treatment of aniridia-associated keratopathy (AAK).

METHODS

Six eyes of 6 patients with severe AAK received an allogeneic stem cell graft between January 2010 and March 2017. Anatomical and functional results were assessed at 6 months, 1 year, 2 years, and the final follow-up visit available. Safety analysis was performed by considering all perioperative and postoperative adverse events and additional surgeries required during the follow-up period.

RESULTS

The mean follow-up was 53.6 months (range 24-104 months). In most patients (80%), there was an early improvement of the keratopathy postoperatively, which slowly regressed during longer follow-up. At the final follow-up, 4 of the eyes were graded as failure and 1 eye was graded as partial success. Grading the sixth eye was not possible because of an adverse event. None of the patients maintained a total anatomical success in the long-term. Only 1 patient maintained a modest improvement in best-corrected visual acuity from hand motion to counting fingers. Four serious adverse events were recorded in 2 patients.

CONCLUSIONS

Severe AAK remains a challenging condition to manage. Transplantation of allogenic ex vivo cultivated limbal stem cells may provide a temporary improvement in ocular surface stability, but anatomical and functional results are poor in the long-term. The eyes are prone to adverse events, and any surgical treatment should take this into consideration.

Genetic Modification of Limbal Stem Cells to Decrease Allogeneic Immune Responses

Limbal stem cell (LSC) transplantation is the only efficient treatment for patients affected by LSC deficiency (LSCD). Allogeneic LSC transplantation is one of the most successful alternative for patients with bilateral LSCD. Nevertheless, the high variability of the human leukocyte antigens (HLA) remains a relevant obstacle to long-term allogeneic graft survival. This study characterized the immunologic properties of LSCs and proposed a genetic engineering strategy to reduce the immunogenicity of LSCs and of their derivatives. Hence, LSC HLA expression was silenced using lentiviral vectors encoding for short hairpin (sh) RNAs targeting β2-microglobulin (β2M) or class II major histocompatibility complex transactivator (CIITA) to silence HLA class I and II respectively. Beside the constitutive expression of HLA class I, LSCs showed the capability to upregulate HLA class II expression under inflammatory conditions. Furthermore, LSCs demonstrated the capability to induce T-cell mediated immune responses. LSCs phenotypical and functional characteristics are not disturbed after genetic modification. However, HLA silenced LSC showed to prevent T cell activation, proliferation and cytotoxicity in comparison to fully HLA-expressing LSCs. Additionally; HLA-silenced LSCs were protected against antibody-mediated cellular-dependent cytotoxicity. Our data is a proof-of-concept of the feasibility to generate low immunogenic human LSCs without affecting their typical features. The use of low immunogenic LSCs may support for long-term survival of LSCs and their derivatives after allogeneic transplantation.

Midterm outcomes of penetrating keratoplasty following allogeneic cultivated limbal epithelial transplantation in patients with bilateral limbal stem cell deficiency

AIM

To evaluate the midterm outcomes of penetrating keratoplasty (PK) following allogeneic cultivated limbal epithelial transplantation (CLET) for bilateral total limbal stem cell deficiency (LSCD).

METHODS

Ten patients (10 eyes) with bilateral LSCD were enrolled in this prospective noncomparative case series study. Each participant underwent PK approximately 6mo after a CLET. Topical tacrolimus, topical and systemic steroids, and oral ciclosporin were administered postoperatively. Best-corrected visual acuity (BCVA), intraocular pressure (IOP), ocular surface grading scores (OSS), corneal graft epithelial rehabilitation, persistent epithelial defect (PED), immunological rejection, and graft survival rate were assessed.

RESULTS

The time interval between PK and allogeneic CLET was 6.90±1.29 (6-10)mo. BCVA improved from 2.46±0.32 logMAR preoperatively to 0.77±0.55 logMAR post-PK (P<0.001). Kaplan-Meier analysis of mean graft survival revealed graft survival rates of 100% at 12 and 24mo and 80.0% at 36mo. PEDs appeared in 5 eyes at different periods post-PK, and graft rejection occurred in 4 eyes. The total OSS decreased from 12.4±4.4 before allogeneic CLET to 1.4±1.51 after PK.

CONCLUSION

A sequential therapy design of PK following allogeneic CLET can maintain a stable ocular surface with improved BCVA despite the relatively high graft rejection rate.

Outcomes of surgical interventions for the treatment of limbal stem cell deficiency

Background & objectives:

In the current scenario, with availability of different surgical procedures for limbal stem cell deficiency (LSCD), there exists no common consensus as to the standardization of the management protocol for the same. In addition, there also exists diversity in the views about the clinical diagnosis, ancillary investigations and clinical parameters. The objective of the present study was to evaluate the reported outcomes of surgical interventions for the management of LSCD.

Methods:

A systematic review of published literature on limbal stem cell transplantation (LSCT) was performed using Ovid Medline, Embase and PubMed for a duration of 2009 to 2019. Original studies including prospective, retrospective case series and randomized controlled trials, articles in English language, articles with access to full text and studies with more than or at least 10 patients were included in this review. Data related to clinical and visual outcomes were evaluated, and pool estimates of different surgeries were calculated using random-effects model and individually using Pearson’s Chi-square test.

Results:

A total of 1133 abstracts were evaluated. Finally, 17 studies were included for the analysis. Among these 17 studies, direct limbal lenticule transplantation was performed in five studies, of which autologous tissue from the fellow eye [conjunctival limbal autograft (CLAU)], allograft from a cadaver/live donor [keratolimbal allograft (KLAL)/conjunctival limbal allograft (CLAL)] and combination of CLAU plus KLAL were done in one, three and one studies, respectively. The ex vivo expanded cultivated limbal epithelial transplantation (CLET) was reported in six studies and simple limbal epithelial transplantation (SLET) in four studies. Two were comparative studies comparing CLET and CLAL (living-related CLAL) with cadaveric KLAL, respectively. Outcome analysis of the included studies showed significant heterogeneity. Calculated pool rate for various types of surgeries was calculated. The pool estimate for CLAL was 67.56 per cent [95% confidence interval (CI), 41.75-93.36; I²=83.5%, P=0.002]. For KLAL, this value was 63.65 per cent (95% CI, 31.38-95.91; I²=92.4%, P=0.000). Pool estimate for CLET was 78.90 per cent (95% CI, 70.51-87.28; I²=73.6%, P=0.001). Corresponding values for SLET were 79.08 per cent (95% CI, 74.10-84.07; I²=0.0%, P=0.619). CLAU and combination of CLAU plus KLAL were done in one study each; hence, statistical analysis could not be done. The functional outcome in terms of gain in visual acuity post-operatively was better in KLAL (P<0.005) and SLET group as compared to CLET group.

Interpretation & conclusions:

The present analysis suggests that though the anatomical success rates were almost identical between SLET, CLET, CLAL, and KLAL procedures, the functional success rates were better following KLAL and SLET procedures as compared to CLET. Decision for LSCT for cases of ocular burns based on either clinical judgement of the surgeon or individual diagnosis remains a suitable option.

Cisd2 plays an essential role in corneal epithelial regeneration

Background

Age-related changes affecting the ocular surface cause vision loss in the elderly. Cisd2 deficiency drives premature aging in mice as well as resulting in various ocular surface abnormalities. Here we investigate the role of CISD2 in corneal health and disease.

Methods

We studied the molecular mechanism underlying the ocular phenotypes brought about by Cisd2 deficiency using both Cisd2 knockout (KO) mice and a human corneal epithelial cell (HCEC) cell line carrying a CRISPR-mediated CISD2KO background. We also develop a potential therapeutic strategy that targets the Ca²⁺ signaling pathway, which has been found to be dysregulated in the corneal epithelium of subjects with ocular surface disease in order to extend the mechanistic findings into a translational application.

Findings

Firstly, in patients with corneal epithelial disease, CISD2 is down-regulated in their corneal epithelial cells. Secondly, using mouse cornea, Cisd2 deficiency causes a cycle of chronic injury and persistent repair resulting in exhaustion of the limbal progenitor cells. Thirdly, in human corneal epithelial cells, CISD2 deficiency disrupts intracellular Ca²⁺ homeostasis, impairing mitochondrial function, thereby retarding corneal repair. Fourthly, cyclosporine A and EDTA facilitate corneal epithelial wound healing in Cisd2 knockout mice. Finally, cyclosporine A treatment restores corneal epithelial erosion in patients with dry eye disease, which affects the ocular surface.

Interpretation

These findings reveal that Cisd2 plays an essential role in the cornea and that Ca²⁺ signaling pathways are potential targets for developing therapeutics of corneal epithelial diseases.

Funding

This study was supported by the Ministry of Science and Technology (MOST) and Chang Gung Medical Research Foundation, Taiwan.

Clinical Aspects of Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis With Severe Ocular Complications in India

Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) is a spectrum of rare, severe immunological blistering skin reactions which are triggered by medication intake or infections. The acute phase is characterized by necrolysis of the skin and desquamation of mucosa, primarily oral and ocular, with significant mortality rates. The chronic phase is characterized by multi-organ sequelae with increased rates of morbidity and reduced quality of life for patients who have survived the acute phase. Since the primary goal in the acute phase is saving the life of the patient, ocular involvement is often missed and a significant proportion of patients present to an ophthalmologist with the chronic ocular sequelae. In India, chronic ocular sequelae and low vision are observed in two-thirds of patients who present in the chronic phase of SJS/TEN. In the chronic phase of ocular involvement, there are definite windows of opportunity which if targeted with specific interventions such as scleral lenses and mucous membrane grafts can help reduce the incidence of corneal blindness and improve the quality of life for patients with SJS/TEN. Over the last decade, several studies from India have advanced the understanding of the natural course of ocular involvement in SJS/TEN and the outcomes of timely interventions in the chronic phase of the disease. We present an overview of the epidemiology of ocular complications of SJS/TEN in India, the specific challenges faced in the management of ocular complications in the acute stage and recent advances in management of the chronic ocular complications of the disease.

Current perspectives of limbal-derived stem cells and its application in ocular surface regeneration and limbal stem cell transplantation

Limbal stem cells are involved in replenishing and maintaining the epithelium of the cornea. Damage to the limbus due to chemical/physical injury, infections, or genetic disorders leads to limbal stem cell deficiency (LSCD) with partial or total vision loss. Presently, LSCD is treated by transplanting limbal stem cells from the healthy eye of the recipient, living-related, or cadaveric donors. This review discusses limbal-derived stem cells, the importance of extracellular matrix in stem cell niche maintenance, the historical perspective of treating LSCD, including related advantages and limitations, and our experience of limbal stem cell transplantation over the decades.

High-Resolution Optical Coherence Tomography Angiography Characteristics of Limbal Stem Cell Deficiency

This study aimed to identify the anterior segment high-resolution optical coherence tomography (HR-OCT) and HR-OCT angiography (HR-OCTA) features suggestive of limbal stem cell deficiency (LSCD) as confirmed by both impression cytology (IC) and in vivo confocal microscopy (IVCM). This was a single-centre prospective cross-sectional study including 24 eyes of 22 patients with clinical suspicion of LSCD based on peripheral superficial corneal vascularisation and scarring. On IC and IVCM, performed and interpreted by blinded observers, 12 eyes each were diagnosed with and without LSCD. Additionally, 10 eyes of 5 healthy volunteers with no ocular pathology were also imaged. The 136 HR-OCT/A images of these 34 eyes were analysed with respect to 12 imaging parameters; the parameters most suggestive of LSCD were identified and the sensitivity and specificity were calculated. In the LSCD group, the most common aetiology was ocular chemical burns (83%), whereas in the non-LSCD group, the most common aetiology was viral keratitis (67%). Multiple logistic regression analysis revealed that mean epithelial reflectivity, mean stromal reflectivity, and mean superficial vascular density were the parameters that were diagnostic of LSCD on HR-OCT/A (p < 0.0001). A ratio of the mean epithelial reflectivity to stromal reflectivity of >1.29 corresponded with a high sensitivity (91.7%) and specificity (98.75%); while a mean superficial vascular density score of >0.38 corresponded with a sensitivity of 97.9% and specificity of 73.8%. In conclusion, HR-OCT/A as a non-invasive imaging modality could prove to be a useful tool for confirming the diagnosis of LSCD, with potential clinical and research applications.

Mini-Review: Regenerating the Corneal Epithelium With Simple Limbal Epithelial Transplantation

Simple limbal epithelial transplantation (SLET) is an ingenious, low cost and effective technique of limbal stem cell transplantation (LSCT) that is increasingly being undertaken in practice across the world. Since it was first described a decade ago, the technique has been performed in a variety of cases of limbal stem cell deficiency (LSCD) and has underwent several innovative modifications. Published literature on SLET has progressively increased over time and successful outcomes in various clinical scenarios have been reported. This concise review attempts to present a crisp account of SLET covering the indications and contraindications of performing the procedure; detailed account of pre-operative work up and preparation; surgical technique and its modifications; post-operative course, care and possible complications as well as published outcomes of surgery from across the world. Comparative analysis of various techniques of LSCT have been discussed and common concerns of surgeons practising or those who are planning to start practising SLET have been addressed. The authors hope that the pragmatic insights and pearls given at the end of the review will aid the surgeons in performing this technique to provide maximum benefit to patients suffering from the potentially blinding condition of LSCD.

Human Umbilical Cord-Derived Mesenchymal Stem Cells Promote Corneal Epithelial Repair In Vitro

Corneal injuries are among the leading causes of blindness and vision impairment. Trauma, infectious keratitis, thermal and chemical (acids and alkali burn) injuries may lead to irreversible corneal scarring, neovascularization, conjunctivalization, and limbal stem cell deficiency. Bilateral blindness constitutes 12% of total global blindness and corneal transplantation remains a stand-alone treatment modality for the majority of end-stage corneal diseases. However, global shortage of donor corneas, the potential risk of graft rejection, and severe side effects arising from long-term use of immunosuppressive medications, demands alternative therapeutic approaches. Umbilical cord-derived mesenchymal stem cells can be isolated in large numbers using a relatively less invasive procedure. However, their role in injury induced corneal repair is largely unexplored. Here, we isolated, cultured and characterized mesenchymal stem cells from human umbilical cord, and studied the expression of mesenchymal (CD73, CD90, CD105, and CD34), ocular surface and epithelial (PAX6, WNT7A, and CK-8/18) lineage markers through immunofluorescence. The cultured human limbal and corneal epithelial cells were used as controls. Scratch assay was used to study the corneal epithelial repair potential of umbilical cord-derived mesenchymal stem cells, in vitro. The in vitro cultured umbilical cord-derived mesenchymal stem cells were plastic adherent, showed trilineage differentiation and expressed: mesenchymal markers CD90, CD105, CD73; epithelial marker CK-8/18, and ocular lineage developmental markers PAX6 and WNT-7A. Our findings suggest that umbilical cord-derived mesenchymal stem cells promote repair of the injured corneal epithelium by stimulating the proliferation of corneal epithelial cells, in vitro. They may serve as a potential non-ocular source of stem cells for treating injury induced bilateral corneal diseases.

Efficacy of Modified Amnion-Assisted Conjunctival Epithelial Redirection (ACER) for Partial Limbal Stem Cell Deficiency

Background and objectives: the aim of this study was to analyze the efficacy of a modified “amnion-assisted conjunctival epithelial redirection (ACER)” technique for the treatment of partial limbal stem cell deficiency (LSCD). Materials and methods: the medical records of three patients with partial LSCD who underwent corneal surface reconstruction with modified ACER following superficial keratectomy were retrospectively studied. Briefly, in this technique, an inner amniotic membrane (AM) layer was applied on the corneal surface to promote corneal re-epithelialization. The outer AM layer was applied as a barrier to prevent the invasion of conjunctival epithelial cells into the cornea before the corneal surface was completely covered by corneal epithelial cells derived from the remaining intact limbal stem cells. Results: in all three cases, the outer AM layer successfully kept the conjunctival epithelium away from the corneal surface and prevented an admixture of conjunctival epithelial cells with corneal epithelial cells. In all three patients, the cornea was completely re-epithelized with epithelial cells derived from the remaining healthy limbal stem cells, and a clear visual axis was maintained without recurrence for a mean follow-up period of 37.3 ± 8.6 months. Conclusions: the preliminary results suggest that modified ACER appears to be a viable option for patients with partial LSCD.

Corneal epithelium and limbal region alterations due to glaucoma medications evaluated by anterior segment optic coherence tomography: a case-control study

AIM

To investigate the corneal epithelial and limbal epithelial alterations in patients under topical glaucoma treatment using anterior segment-OCT (AS-OCT) and to determine the changes of the limbal region due to the preservatives and glaucoma drugs, that can progress to limbal stem cell deficiency (LSCD). Limbal thickness was measured by AS-OCT to evaluate limbal cell deficiency.

METHODS

Forty-seven patients using topical medication for glaucoma, and 48 control subjects were enrolled in this matched case-control study. The patients were divided into four groups according to the treatment regimens. Group 1: One-drug regimen, Group 2: Two-drug regimen, Group 3: Three-drug regimen, Group 4: Four-drug regimen For the ocular surface evaluation; tear break-up time with standard fluorescein sodium sterile strip application, Schirmer test-I, Ocular Surface Disease Index Questionnaire, and AS-OCT were performed.

RESULTS

A total of 95 subjects were included: 47 eyes of 47 patients with glaucoma medication and 48 eyes of 48 healthy subjects. There was a statistically significant difference between patients and controls according to BUT, SCH, and OSDI (p < 0.001). The mean central corneal epithelium thickness was 48.5 ± 5.3 in patients and 54.5 ± 5.9 in controls (p < 0.001). The mean central total corneal thickness was 529.2 ± 41.2 in patients and 536 ± 35.3 in controls (p = 0.335). The mean limbal epithelium thickness was 64.1 ± 9.1 in patients and 76 ± 11.5 in controls (p < 0.001).

CONCLUSION

Using at least one glaucoma drug caused limbal area injury, changed ocular surface measurements, and significantly reduced the limbal epithelial thickness where the stem cells reside. The limbal epithelial thickness measurement by AS-OCT seems to be an innovative, non-invasive, and promising technique for detecting and staging corneal damage in topical glaucoma therapy.

Therapeutic effect of secretome from TNF-α stimulated mesenchymal stem cells in an experimental model of corneal limbal stem cell deficiency

AIM

To explore the secretome efficacy in tumor necrosis factor (TNF)-α stimulated mouse mesenchymal stem cells (MSCs) in a murine model of corneal limbal alkali injury.

METHODS

Corneal limbal stem cell deficiency (LSCD) was created in the eyes of male C57 mice. Concentrated conditioned medium from TNF-α stimulated MSCs (MSC-CMT) was applied topically for 4wk, with basal medium and conditioned medium from MSCs as controls. Corneal opacification, corneal inflammatory response, and corneal neovascularization (NV) were evaluated. Corneal epithelial cell apoptosis, corneal conjunctivation, and inflammatory cell infiltration were assessed with TUNEL staining, CK3 and Muc-5AC immunostaining, and CD11b immunofluorescence staining, respectively. The effect of TSG-6 was further evaluated by knockdown with short hairpin RNA (shRNA).

RESULTS

Compared to the controls, topical administration of MSC-CMT significantly ameliorated the clinical symptoms of alkali-induced LSCD, with restrained corneal NV, reduced corneal epithelial cell apoptosis, and inhibition of corneal conjunctivation. In addition, MSC-CMT treatment significantly reduced CD11b⁺ inflammatory cell infiltration, and inhibited the expression of pro-inflammatory cytokines (IL-1β, TNF-α and IL-6). Furthermore, the promotion of corneal epithelial reconstruction by MSC-CMT was largely abolished by TSG-6 knockdown.

CONCLUSION

Our study provides evidence that MSC-CMT enhances the alleviation of corneal alkali injuries, partially through TSG-6-mediated anti-inflammatory protective mechanisms. MSC-CMT may serve as a potential strategy for treating corneal disorders.

Understanding cornea epithelial stem cells and stem cell deficiency: Lessons learned using vertebrate model systems

Animal models have contributed greatly to our understanding of human diseases. Here, we focus on cornea epithelial stem cell (CESC) deficiency (commonly called limbal stem cell deficiency, LSCD). Corneal development, homeostasis and wound healing are supported by specific stem cells, that include the CESCs. Damage to or loss of these cells results in blindness and other debilitating ocular conditions. Here we describe the contributions from several vertebrate models toward understanding CESCs and LSCD treatments. These include both mammalian models, as well as two aquatic models, Zebrafish and the amphibian, Xenopus. Pioneering developments have been made using stem cell transplants to restore normal vision in patients with LSCD, but questions still remain about the basic biology of CESCs, including their precise cell lineages and behavior in the cornea. We describe various cell lineage tracing studies to follow their patterns of division, and the fates of their progeny during development, homeostasis, and wound healing. In addition, we present some preliminary results using the Xenopus model system. Ultimately, a more thorough understanding of these cornea cells will advance our knowledge of stem cell biology and lead to better cornea disease therapeutics.

Subconjunctival Injection of Transdifferentiated Oral Mucosal Epithelial Cells for Limbal Stem Cell Deficiency in Rats

Rat limbal niche cells (LNCs) have been proven to induce transdifferentiation of oral mucosal epithelial cells (OMECs) into corneal epithelial-like cells termed transdifferentiated oral mucosal epithelial cells (T-OMECs). This investigation aimed to evaluate the effect of subconjunctival T-OMEC injections on alkali-induced limbal stem cell deficiency (LSCD) in rats. LNCs were cocultured with OMECs in the Transwell system to obtain T-OMECs, with NIH-3T3 cells serving as a control. Subconjunctival injection of single T-OMEC or OMEC suspension was performed immediately after corneal alkali injury. T-OMECs were prelabeled with the fluorescent dye CM-DiI in vitro and tracked in vivo. Corneal epithelial defect, opacity, and neovascularization were quantitatively analyzed. The degree of corneal epithelial defect (from day 1 onward), opacity (from day 5 onward), and neovascularization (from day 2 onward) was significantly less in the T-OMEC group than in the OMEC group. Cytokeratin 12 (CK12), pigment epithelium-derived factor, and soluble fms-like tyrosine kinase-1 were expressed at a higher rate following T-OMEC injection. Some CM-DiI-labeled cells were found to be coexpressed with CK12, Pax6, and ΔNp63α in the corneal epithelium after subconjunctival injection. Subconjunctival injection of T-OMECs prevents conjunctival invasion and maintains a normal corneal phenotype, which might be a novel strategy in the treatment of LSCD.

Transplantation of human corneal limbal epithelial cell sheet harvested on synthesized carboxymethyl cellulose and dopamine in a limbal stem cell deficiency

This study aimed to evaluate the efficacy and safety of transplantation with human corneal limbal epithelial (HCLE) cell sheets cultured on carboxymethyl cellulose (CMC)-dopamine (DA)-coated substrates and harvested via enzymatic digestion of CMC with cellulase in a rabbit animal model of limbal stem cell deficiency (LSCD). Synthesized CMC-DA was pretreated onto the surface of culture plates. Then, HCLE cells were cultured on precoated CMC-DA and HCLE cell sheets were harvested using cellulase-containing cell culture medium. HCLE cell sheets were evaluated using a live/dead assay, histological examination, and immunofluorescence staining. For in vivo assessment, HCLE cell sheets were transplanted in a rabbit model of LSCD for 2 weeks to determine the effectiveness of the repair. Primary culture of HCLE cells stained positively for p63, cytokeratin (CK)15, and CK12. HCLE cell sheets were generated with a well-preserved morphology and transparency ranging in size from 15 to 19 mm after cellulase-assisted cell sheet generation. HCLE cell sheets uniformly stained positively for human mitochondria, p63, CK15, CK12, CK3/2p, and zonula occludens (ZO)-1. HCLE cell sheet transplantation in a rabbit model of LSCD improved the corneal opacity and neovascularization scores. Transplanted HCLE cell sheets stained positively for p63 and CK12. Transplantation of HCLE cell sheets harvested on CMC-DA coating combined with cellulase is a safe and efficient procedure for corneal epithelial regeneration in a rabbit model of LSCD. This system could enable a promising strategy to regenerate corneal epithelium by transplantation in ocular surface disorders.