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.

ElSheikh R, Arabi A, R. Frank C, M. Elhusseiny A, K. Eleiwa T, Arami S, R. Djalilian A, Kheirkhah A. 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.