Effects of hypoxia in the diabetic corneal stroma microenvironment.

Corneal dysfunctions associated with Diabetes Mellitus (DM), termed diabetic keratopathy (DK), can cause impaired vision and/or blindness. Hypoxia affects both Type 1 (T1DM) and Type 2 (T2DM) surprisingly, the role of hypoxia in DK is unexplored. The aim of this study was to examine the impact of hypoxia in vitro on primary human corneal stromal cells derived from Healthy (HCFs), and diabetic (T1DMs and T2DMs) subjects, by exposing them to normoxic (21% O2) or hypoxic (2% O2) conditions through 2D and 3D in vitro models. Our data revealed that hypoxia affected T2DMs by slowing their wound healing capacity, leading to significant alterations in oxidative stress-related markers, mitochondrial health, cellular homeostasis, and endoplasmic reticulum health (ER) along with fibrotic development. In T1DMs, hypoxia significantly modulated markers related to membrane permeabilization, oxidative stress via apoptotic marker (BAX), and protein degradation. Hypoxic environment induced oxidative stress (NOQ1 mediated reduction of superoxide in T1DMs and Nrf2 mediated oxidative stress in T2DMs), modulation in mitochondrial health (Heat shock protein 27 (HSP27), and dysregulation of cellular homeostasis (HSP90) in both T1DMs and T2DMs. This data underscores the significant impact of hypoxia on the diabetic cornea. Further studies are warranted to delineate the complex interactions.

The role of the JAK/STAT3 signaling pathway in acquired corneal diseases.

Acquired corneal diseases such as dry eye disease (DED), keratitis and corneal alkali burns are significant contributors to vision impairment worldwide, and more effective and innovative therapies are urgently needed. The Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling pathway plays an indispensable role in cell metabolism, inflammation and the immune response. Studies have shown that regulators of this pathway are extensively expressed in the cornea, inducing significant activation of JAK/STAT3 signaling in specific acquired corneal diseases. The activation of JAK/STAT3 signaling contributes to various pathophysiological processes in the cornea, including inflammation, neovascularization, fibrosis, and wound healing. In the context of DED, the hypertonic environment activates JAK/STAT3 signaling to stimulate corneal inflammation. Inflammation and injury progression in infectious keratitis can also be modulated by JAK/STAT3 signaling. Furthermore, JAK/STAT3 signaling is involved in every stage of corneal repair after alkali burns, including acute inflammation, angiogenesis and fibrosis. Treatments modulating JAK/STAT3 signaling have shown promising results in attenuating corneal damage, indicating its potential as a novel therapeutic target. Thus, this review emphasizes the multiple roles of the JAK/STAT3 signaling pathway in common acquired corneal disorders and summarizes the current achievements of JAK/STAT3-targeting therapy to provide new insights into future applications.

Anonic Silicon Hydrogels Affect the Concentration of Proteins in Tears during Wear.

PURPOSE: The objective of this study was to quantitatively assess the concentration of human tear proteins in patients wearing contact lenses of various ionicities and determine whether differences were related to the incidence of corneal infiltrative events (CIE). METHODS: 24 subjects (samples) were randomly selected for spectral count analysis to obtain protein concentrations using LCMS analysis. The subjects were neophyte and ametropic with ages between 18 and 40; 6 wore control lenses, 8 wore TestLens1, and 10 wore TestLens2. 16 subjects experienced CIEs during the study. RESULTS: A pairwise multiple hypothesis test identified 7 proteins that significantly differed in concentration between TestLens1 and control, and 11 proteins that differed between TestLens2 and control. Of the 12 unique proteins, 9 were at increased concentration and 3 were at lower concentration in the tears of test lens wearers compared to the control lens group. Bootstrap clustering confirmed these findings, showing 3 similar clusters to the original sample groups which separated people wearing control lenses from those wearing TestLens1 or TestLens2 with 83% accuracy and between TestLens1 and TestLens2 with 45% accuracy. Permutation testing identified 5 proteins that had significantly changed in concentration between people wearing TestLens2 and Control lenses. There was no difference in protein concentrations between those subjects who experienced a CIE and those who did not. CONCLUSION: Wearing contact lenses of different ionicities can affect the concentration of proteins in the tear film. The current study did not find any associations of the concentration of proteins with CIEs. Future tests with increased sample size are needed to establish any relations between these changes and clinical performance.

NBL1 Reduces Corneal Fibrosis and Scar Formation after Wounding.

Corneal scarring is a leading cause of blindness. Currently, there is no treatment to prevent and/or reduce corneal scar formation under pathological conditions. Our previous data showed that the NBL1 protein, also termed the DAN Family BMP (Bone morphogenetic protein) Antagonist, was highly expressed in corneal stromal cells upon wounding. Here, we examined the function of NBL1 in corneal wound healing. Mouse corneas were mechanically wounded, followed by a 2-week treatment using NBL1. Wounded corneas treated with vehicle or an Fc tag served as controls. Compared with the controls, NBL1 treatment facilitated wound re-epithelialization, partially restored the stromal thickness, and significantly reduced corneal scar formation. NBL1 treatment did not decrease immune cell infiltration, indicating that the anti-scarring effect was not dependent on immune suppression. We further examined the anti-fibrotic effect of NBL1 on human corneas. Pairs of human corneas were induced to form myofibroblasts (a key player in fibrosis and scarring) upon wounding and incubation in a medium containing TGF-ß1. The OS corneas were treated with Fc as a control, and the OD corneas were treated with NBL1. Compared with the control, human corneas treated with NBL1 had significantly fewer myofibroblasts, which was consistent with these mouse data. A further study revealed that NBL1 treatment inhibited BMP canonical (phospho-Smad1/5) and no-canonical (phospho-p38) pathways in human corneas. Data show that NBL1 reduced corneal fibrosis and scar formation in mice and cultured human corneas. The underlying molecular mechanism is not certain because both anti-fibrotic Smad1/5 and pro-fibrotic p38 pathways were inhibited upon NBL1 treatment. Whether the p38 pathway dominates the Smad1/5 pathway during corneal fibrosis, leading to the anti-fibrotic effect of NBL1, needs further investigation.

Limbal Epithelial Stem Cells in the Diabetic Cornea.

Continuous replenishment of the corneal epithelium is pivotal for maintaining optical transparency and achieving optimal visual perception. This dynamic process is driven by limbal epithelial stem cells (LESCs) located at the junction between the cornea and conjunctiva, which is otherwise known as the limbus. In patients afflicted with diabetes, hyperglycemia-induced impairments in corneal epithelial regeneration results in persistent epithelial and other defects on the ocular surface, termed diabetic keratopathy (DK), which progressively diminish vision and quality of life. Reports of delayed corneal wound healing and the reduced expression of putative stem cell markers in diabetic relative to healthy eyes suggest that the pathogenesis of DK may be associated with the abnormal activity of LESCs. However, the precise role of these cells in diabetic corneal disease is poorly understood and yet to be comprehensively explored. Herein, we review existing literature highlighting aberrant LESC activity in diabetes, focusing on factors that influence their form and function, and emerging therapies to correct these defects. The consequences of malfunctioning or depleted LESC stocks in DK and limbal stem cell deficiency (LSCD) are also discussed. These insights could be exploited to identify novel targets for improving the management of ocular surface complications that manifest in patients with diabetes.

rhFGF-21 accelerates corneal epithelial wound healing through the attenuation of oxidative stress and inflammatory mediators in diabetic mice.

Diabetic keratopathy, commonly associated with a hyperactive inflammatory response, is one of the most common eye complications of diabetes. The peptide hormone fibroblast growth factor-21 (FGF-21) has been demonstrated to have anti-inflammatory and antioxidant properties. However, whether administration of recombinant human (rh) FGF-21 can potentially regulate diabetic keratopathy is still unknown. Therefore, in this work, we investigated the role of rhFGF-21 in the modulation of corneal epithelial wound healing, the inflammation response, and oxidative stress using type 1 diabetic mice and high glucose-treated human corneal epithelial cells. Our experimental results indicated that the application of rhFGF-21 contributed to the enhancement of epithelial wound healing. This treatment also led to advancements in tear production and reduction in corneal edema. Moreover, there was a notable reduction in the levels of proinflammatory cytokines such as TNF-α, IL-6, IL-1ß, MCP-1, IFN-γ, MMP-2, and MMP-9 in both diabetic mouse corneal epithelium and human corneal epithelial cells treated with high glucose. Furthermore, we found rhFGF-21 treatment inhibited reactive oxygen species production and increased levels of anti-inflammatory molecules IL-10 and SOD-1, which suggests that FGF-21 has a protective role in diabetic corneal epithelial healing by increasing the antioxidant capacity and reducing the release of inflammatory mediators and matrix metalloproteinases. Therefore, we propose that administration of FGF-21 may represent a potential treatment for diabetic keratopathy.

Mesenchymal Stem Cells and Exosomes: A Novel Therapeutic Approach for Corneal Diseases.

The cornea, with its delicate structure, is vulnerable to damage from physical, chemical, and genetic factors. Corneal transplantation, including penetrating and lamellar keratoplasties, can restore the functions of the cornea in cases of severe damage. However, the process of corneal transplantation presents considerable obstacles, including a shortage of available donors, the risk of severe graft rejection, and potentially life-threatening complications. Over the past few decades, mesenchymal stem cell (MSC) therapy has become a novel alternative approach to corneal regeneration. Numerous studies have demonstrated the potential of MSCs to differentiate into different corneal cell types, such as keratocytes, epithelial cells, and endothelial cells. MSCs are considered a suitable candidate for corneal regeneration because of their promising therapeutic perspective and beneficial properties. MSCs compromise unique immunomodulation, anti-angiogenesis, and anti-inflammatory properties and secrete various growth factors, thus promoting corneal reconstruction. These effects in corneal engineering are mediated by MSCs differentiating into different lineages and paracrine action via exosomes. Early studies have proven the roles of MSC-derived exosomes in corneal regeneration by reducing inflammation, inhibiting neovascularization, and angiogenesis, and by promoting cell proliferation. This review highlights the contribution of MSCs and MSC-derived exosomes, their current usage status to overcome corneal disease, and their potential to restore different corneal layers as novel therapeutic agents. It also discusses feasible future possibilities, applications, challenges, and opportunities for future research in this field.

FoxC1 activates limbal epithelial stem cells following corneal epithelial debridement.

Limbal epithelial stem cells are not only critical for corneal epithelial homeostasis but also have the capacity to change from a relatively quiescent mitotic phenotype to a rapidly proliferating cell in response to population depletion following corneal epithelial wounding. Pax6+/- mice display many abnormalities including corneal vascularization and these aberrations are consistent with a limbal stem cell deficiency (LSCD) phenotype. FoxC1 has an inhibitory effect on corneal avascularity and a positive role in stem cell maintenance in many tissues. However, the role of FoxC1 in limbal epithelial stem cells remains unknown. To unravel FoxC1's role(s) in limbal epithelial stem cell homeostasis, we utilized an adeno-associated virus (AAV) vector to topically deliver human FOXC1 proteins into Pax6 +/- mouse limbal epithelium. Under unperturbed conditions, overexpression of FOXC1 in the limbal epithelium had little significant change in differentiation (PAI-2, Krt12) and proliferation (BrdU, Ki67). Conversely, such overexpression resulted in a marked increase in the expression of putative limbal epithelial stem cell markers, N-cadherin and Lrig1. After corneal injuries in Pax6 +/- mice, FOXC1 overexpression enhanced the behavior of limbal epithelial stem cells from quiescence to a highly proliferative status. Overall, the treatment of AAV8-FOXC1 may be beneficial to the function of limbal epithelial stem cells in the context of a deficiency of Pax6 function.

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.

Proteomic characterization of aqueous humor in corneal endothelial decompensation after penetrating keratoplasty.

Corneal endothelial decompensation (CED) is the major cause of the long-term graft failure, but the underlying mechanisms remain unclear. The purpose of this study was to characterize the proteomic profile in CED aqueous humor (AH) after penetrating keratoplasty (PKP). We collected AH samples (n = 6/group) from CED patients underwent PKP and cataract patients, respectively. The label-free quantitative proteomic analysis was performed to identify the differentially-expressed proteins (DEPs). The biological functions of DEPs were evaluated using Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genome (KEGG) analysis. The protein-protein interaction (PPI) network construction was employed to distinguish the hub proteins of DEPs, and the selected proteins were validated by parallel reaction monitoring (PRM). The human peripheral blood mononuclear cells (PBMCs) were adopted to investigate the effect of biglycan (BGN) on inflammatory response, and the subsequent outcomes of inflammation on human corneal endothelial cells (HCECs). A total of 174 DEPs were identified in CED AH of patients underwent PKP, including 102 up-regulated proteins and 72 down-regulated proteins. Bioinformatics analysis revealed the significant enrichment of cytokine-mediated signaling pathway and extracellular matrix (ECM) organization in the up-regulated proteins, as well as the alterations of cellular components, including the increase of collagen and complement component C1 complex, and reduction in extracellular exosomes. A hub protein cluster of 15 proteins was determined by Molecular Complex Detection (MCODE), including FN1, BGN, COMP, COL11A1, COLA3A1, and COL1A1. Moreover, BGN promoted pro-inflammatory cytokine (such as TNF-α, IL-1ß and IL-6) production in PBMCs through NF-κB signaling pathway, which subsequently resulted in HCECs death. These findings provided a systemic protein profile of AH in CED patients after corneal transplantation, with the alterations implicated in cytokine-mediated signaling, ECM, complement system, and exsomes. The identified proteins and signaling pathways probably paved the novel insight into understanding the pathogenesis of the disease.

Evaluation of the Algerbrush II rotating burr as a tool for inducing ocular surface failure in a mouse model.

Purpose: The Algerbrush II has been widely used to induce corneal and limbal injuries in animal models. The extent of injury varies with the duration of exposure, pressure from the placement of the burr, and the size of the burr. However, no study has explored the correlation between the duration of exposure and the severity of injury in mouse model with corneal and limbal stem cell deficiency (LSCD) induced using the Algerbrush II. Therefore, this study aimed to evaluate the variations in the severity of corneal and limbal injury with different durations of the Algerbrush II application. Methods: The entire cornea and limbus of C57BL/6 mice were injured for 30-45 s, 60-75 s, 90-120 s, and 3-4 min. Photography and slit-lamp examination was performed on days 0, 2, 4, and 7, followed by hematoxylin & eosin, periodic acid-Schiff, and immunohistochemical staining. Statistical analysis was performed using one way ANOVA analysis. Results: A duration of 30-45 s of injury was found to be sufficient to induce superficial corneal and limbal epithelial debridement and re-epithelialization was completed in all eyes by day 7; however, clinical signs of LSCD were not observed in all mice. Increasing the exposure time to 90-120 s resulted in central 2+ corneal opacity with limbal and paracentral corneal neovascularization. All eyes injured for 3-4 min displayed clinical signs of LSCD, such as persistent epithelial defects on day 7 after the injury, central corneal neovascularization, and 2.2+ diffuse corneal opacity. Histological signs of LSCD, including goblet cell metaplasia and K13 expression on the corneal surface, were observed in all injured eyes. Conclusions: Our findings suggest that the duration of injury is an important factor influencing the severity of LSCD in a murine model of injury. A 1-mm rotating burr was found to be more effective for keratectomy and pigment release, whereas a 0.5-mm burr was more suitable for corneal epithelial debridement.

The Role of Ectodysplasin A on the Ocular Surface Homeostasis.

Ectodysplasin A (EDA), a ligand of the TNF family, plays an important role in maintaining the homeostasis of the ocular surface. EDA is necessary for the development of the meibomian gland, the lacrimal gland, as well as the proliferation and barrier function of the corneal epithelium. The mutation of EDA can induce the destruction of the ocular surface resulting in keratopathy, abnormality of the meibomian gland and maturation of the lacrimal gland. Experimental animal studies showed that a prenatal ultrasound-guided intra-amniotic injection or postnatal intravenous administration of soluble recombinant EDA protein can efficiently prevent the development of ocular surface abnormalities in EDA mutant animals. Furthermore, local application of EDA could restore the damaged ocular surface to some extent. Hence, a recombinant EDA-based therapy may serve as a novel paradigm to treat ocular surface disorders, such as meibomian gland dysfunction and corneal epithelium abnormalities.

Trends in using mesenchymal stromal/stem cells (MSCs) in treating corneal diseases.

Since their inception in the 1960s-70s, mesenchymal stem/stromal cells (MSCs) have gained interest because of their differentiation potential, anti-inflammatory effects, and immune-modulating properties. Both cell-based and cell-free MSC treatments show healing capacity in injured tissues. Cell-based treatment comprises MSCs and all secreted products, whereas cell-free treatments include only the secreted products. MSCs are therapeutically administered to many damaged organs owing to their efficacy. Specifically, the eye is a unique organ system to study the effects of MSCs, as treatment is easily applied and measured owing to its external location. The eye holds an immune-privileged status, wherein inflammation and immune responses are innately down-regulated. As excessive inflammation in the cornea often leads to fibrosis and irreversible corneal hazing, many studies have investigated the anti-inflammatory and immune-modulating capacities of MSCs. Decades of research suggest that MSCs modulate the immune response by secreting cytokines, growth factors, and extracellular matrix proteins that inhibit the infiltration of inflammatory cells following injury and promote a healing phenotype via M2 macrophage polarization. MSCs have also shown trans-differentiation potential into cornea-specific cell types during the wound healing process, such as corneal epithelial, stromal, or endothelial cells. This review discusses recent investigations of MSC treatment in the cornea, focusing on therapeutic efficacy, mechanisms, and future directions.

Autosomal recessive LRP1-related syndrome featuring cardiopulmonary dysfunction, bone dysmorphology, and corneal clouding.

We provide the first study of two siblings with a novel autosomal recessive LRP1-related syndrome identified by rapid genome sequencing and overlapping multiple genetic models. The patients presented with respiratory distress, congenital heart defects, hypotonia, dysmorphology, and unique findings, including corneal clouding and ascites. Both siblings had compound heterozygous damaging variants, c.11420G > C (p.Cys3807Ser) and c.12407T > G (p.Val4136Gly) in LRP1, in which segregation analysis helped dismiss additional variants of interest. LRP1 analysis using multiple human/mouse data sets reveals a correlation to patient phenotypes of Peters plus syndrome with additional severe cardiomyopathy and blood vessel development complications linked to neural crest cells.

Therapeutic Ultrasound for Topical Corneal Delivery of Macromolecules.

Purpose: The objective of this study was to utilize therapeutic ultrasound in enhancing delivery of topical macromolecules into the cornea. Methods: Rabbit corneas were dissected and placed in a diffusion cell with a small ultra-red fluorescent protein (smURFP; molecular weight of 32,000 Da) as a macromolecule solution. The corneas were treated with continuous ultrasound application at frequencies of 400 or 600 kHz and intensities of 0.8 to 1.0 W/cm2 for 5 minutes, or sham-treated. Fluorescence imaging of the cornea sections was used to observe the delivery of macromolecules into individual epithelial cells. Spectrophotometric analysis at smURFP maximal absorbance of 640 nm was done to determine the presence of macromolecules in the receiver compartment. Safety of ultrasound application was studied through histology analysis. Results: Ultrasound-treated corneas showed smURFP delivery into epithelial cells by fluorescence in the cytoplasm, whereas sham-treated corneas lacked any appreciable fluorescence in the individual cells. The sham group showed 0% of subcellular penetration, whereas the 400 kHz ultrasound-treated group and 600 kHz ultrasound-treated group showed 31% and 57% of subcellular penetration, respectively. Spectrophotometry measurements indicated negligible presence of smURFP macromolecules in the receiver compartment solution in both the sham and ultrasound treatment groups, and these macromolecules did not cross the entire depth of the cornea. Histological studies showed no significant corneal damage due to ultrasound application. Conclusions: Therapeutic ultrasound application was shown to increase the delivery of smURFP macromolecules into the cornea. Translational Relevance: Our study offers a clinical potential for a minimally invasive macromolecular treatment of corneal diseases.

Properties of the acellular porcine cornea crosslinked with UVA/riboflavin as scaffolds for Boston Keratoprosthesis.

The Boston Keratoprosthesis type I (B-KPro) is widely used in the world, but the lack of donor corneas limits its application. This study aims to prepare the acellular porcine cornea (APC) crosslinked with ultraviolet A (UVA)/riboflavin instead of donor corneas as the scaffold for B-KPro. Decellularization of freeze-thaw combined with biological enzymes resulted in approximately 5 ng/mg DNA residue, the a-Gal removal rate of 99%, and glycosaminoglycans retention at a high level of 46.66 ± 2.59 mg/mg. UVA/ riboflavin cross-linking was adopted to induce the formation of new chemical bonds between adjacent collagen chains in the corneal stroma to improve the mechanical properties and resistance to enzymatic hydrolysis. Through comprehensive analysis of the biomechanics, enzyme degradation, immunogenicity and histological structure of the APC crosslinked at different times, CL3 (irradiation conditions, 365 nm, 3 mW/cm, 80 min, both sides) was selected and transplanted into the rabbit cornea model through interlamellar keratoplasty and penetrating keratoplasty as the scaffold of the B-KPro. Compared with the native porcine cornea (NPC) and APC, the experiment of interlamellar pocket indicated that the structure of CL3 was homogeneous without degradation and vascularization in vivo at 12 weeks after surgery. Simultaneously, the results of transplantation of B-KPro showed complete epithelialization of CL3 within 1 week, and neovascularization of the cornea indicated rejection but could be controlled with immunosuppressants. At 3 months postoperatively, the lens of B-KPro remained transparent, and the structure of CL3 was compact and uniform, accompanied by the migration and proliferation of a large number of stromal cells without degradation, suggesting the CL3 could be a promising corneal substitute.

Labial Mucosa Stem Cells: Isolation, Characterization, and Their Potential for Corneal Epithelial Reconstruction.

Purpose: The purpose of this study was to characterize labial mucosa stem cells (LMSCs) and to investigate their potential for corneal epithelial reconstruction in a rabbit model of total limbal stem cell deficiency (LSCD). Methods: Rabbit LMSCs (rLMSCs) and human (hLMSCs) LMSCs were derived from labial mucosa and characterized in terms of their proliferation activity by the evaluation of proliferation index (PI) and colony forming efficiency (CFE), cell senescence, and differentiation abilities. The expression of various limbus-specific, stem cell-specific, and epithelial markers was assessed via immunocytochemistry. Flow cytometry was used to evaluate mesenchymal and hematopoietic cell surface markers expression. Chromosomal stability of the derived cells was examined using the conventional GTG-banding technique. To assess the impact of LMSCs on corneal epithelial reconstruction, rLMSCs were seeded onto a decellularized human amniotic membrane (dHAM), thereafter their regeneration potential was examined in the rabbit model of total LSCD. Results: Both rLMSCs and hLMSCs showed high proliferation and differentiation abilities, entered senescence at later passages, and expressed different stem cell-specific (ABCB5, ALDH3A1, ABCG2, and p63α), mesenchymal (vimentin), and epithelial (CK3/12, CK15) markers. Cell surface antigen expression was similar to other described mesenchymal stem cells. No clonal structural chromosome abnormalities (CSCAs) and the low percentage of non-clonal structural chromosome abnormalities (NSCAs) were observed. Transplantation of rLMSCs promoted corneal epithelial reconstruction and enhanced corneal transparency. Conclusions: LMSCs have significant proliferation and differentiation abilities, display no detrimental chromosome aberrations, and demonstrate considerable potential for corneal repair.

Corneal Collagen Crosslinking (CXL) for Corneal Ectasia after Small Incision Lenticule Extraction (SMILE). / Korneales Kollagen-Crosslinking (CXL) bei Hornhautektasie nach SMILE (Small Incision Lenticule Extraction).

With an estimated incidence of 0.011%, the SMILE procedure seems to have the lowest risk of postoperative keratectasia among contemporary keratorefractive procedures. Nevertheless, due to the novelty of the procedure as well as the lack of data, no clear superiority over femto-LASIK or PRK can be stated at this time. In this respect, application of the identical tomographic screening criteria previously developed for excimer-based procedures is of paramount importance to minimize the risk of corneal ectasia. As an adjunct to conventional corneal tomography, newer imaging modalities such as OCT-based epithelial mapping should be used for preoperative screening before keratorefractive surgery. Corneal crosslinking is an established treatment modality for post-SMILE keratectasia, which promises high success rates especially in early stages. The present case report illustrates these diagnostic and therapeutic considerations.

Topical Losartan and Corticosteroid Additively Inhibit Corneal Stromal Myofibroblast Generation and Scarring Fibrosis After Alkali Burn Injury.

Purpose: To evaluate the efficacy of losartan and prednisolone acetate in inhibiting corneal scarring fibrosis after alkali burn injury in rabbits. Methods: Sixteen New Zealand White rabbits were included. Alkali injuries were produced using 1N sodium hydroxide on a 5-mm diameter Whatman #1 filter paper for 1 minute. Four corneas in each group were treated six times per day for 1 month with 50 µL of (1) 0.8 mg/mL losartan in balanced salt solution (BSS), (2) 1% prednisolone acetate, (3) combined 0.8 mg/mL losartan and 1% prednisolone acetate, or (4) BSS. Area of opacity and total opacity were analyzed in standardized slit-lamp photos with ImageJ. Corneas in both groups were cryofixed in Optimal cutting temperature (OCT) compound at 1 month after surgery, and immunohistochemistry was performed for alpha-smooth muscle actin (α-SMA) and keratocan or transforming growth factor ß1 and collagen type IV with ImageJ quantitation. Results: Combined topical losartan and prednisolone acetate significantly decreased slit-lamp opacity area and intensity, as well as decreased stromal myofibroblast α-SMA area and intensity of staining per section and confined myofibroblasts to only the posterior stroma with repopulation of the anterior and mid-stroma with keratocan-positive keratocytes after 1 month of treatment. Corneal fibroblasts produced collagen type IV not associated with basement membranes, and this production was decreased by topical losartan. Conclusions: Combined topical losartan and prednisolone acetate decreased myofibroblast-associated fibrosis after corneal alkali burns that produced full-thickness injury, including corneal endothelial damage. Increased dosages and duration of treatment may further decrease scarring fibrosis. Translational Relevance: Topical losartan and prednisolone acetate decrease myofibroblast-mediated scarring fibrosis after corneal injury.

Long-term survival in non-human primates of stem cell-derived, MHC-unmatched corneal epithelial cell sheets.

When corneal epithelial stem cells residing in the corneal limbus become dysfunctional, called a limbal stem cell deficiency (LSCD), corneal transparency is decreased, causing severe vision loss. Transplantation of corneal epithelial cell sheets (CEPS) derived from stem cells, including induced pluripotent stem cells, is a promising treatment for LSCD. However, the potential effect of human leukocyte antigen (HLA) concordance on CEPS transplantation has not been addressed. Here, we show that there is no difference in the immune response to CEPS between HLA-matched and -unmatched peripheral blood mononuclear cells in mixed lymphocyte reactions. CEPS transplantation in cynomolgus monkeys revealed that the immune response to major histocompatibility-unmatched CEPS was not strong and could be controlled by local steroid administration. Furthermore, programmed death ligand 1 was identified as an immunosuppressive molecule in CEPS under inflammatory conditions in vitro. Our results indicate that corneal epithelium has low immunogenicity and allogeneic CEPS transplantation requires mild immunosuppression.