Cornea

Brockhausen I, Elimova E, Woodward AM, Argüeso P. Glycosylation pathways of human corneal and conjunctival epithelial cell mucins. Carbohydr Res 2018;470:50-56.Abstract
Mucin glycoproteins on the ocular surface are rich in O-glycans and have important roles in the protection from physical, chemical and microbial impact. In this work, we have cultured human corneal and conjunctival epithelial cells to examine the glycosyltransferase activities that synthesize the O-glycans of mucins. The results indicate that ocular surface epithelial cells have active enzymes that synthesize O-glycans with sialylated core 1, Galβ1-3GalNAcα, and core 2, GlcNAcβ1-6(Galβ1-3)GalNAcα structures which corresponds to previous structural studies. Eye cells also have enzymes that synthesize complex N-glycans that are found on mucins. Results from treatment of eye cells with TNFα suggest that epithelial O-glycosylation changes in a dynamic fashion during inflammatory stimuli of the eye surface.
Tellefsen S, Morthen MK, Richards SM, Lieberman SM, Rahimi Darabad R, Kam WR, Sullivan DA. Sex Effects on Gene Expression in Lacrimal Glands of Mouse Models of Sjögren Syndrome. Invest Ophthalmol Vis Sci 2018;59(13):5599-5614.Abstract
Purpose: Sjögren syndrome is an autoimmune disease that occurs primarily in women, and is associated with lacrimal gland inflammation and aqueous-deficient dry eye. We hypothesize that sex-associated differences in lacrimal gland gene expression are very important in promoting lymphocyte accumulation in this tissue and contribute to the onset, progression, and/or severity of the inflammatory disease process. To test our hypothesis, we explored the nature and extent of sex-related differences in gene expression in autoimmune lacrimal glands. Methods: Lacrimal glands were collected from age-matched, adult, male and female MRL/MpJ-Tnfrsf6lpr (MRL/lpr) and nonobese diabetic/LtJ (NOD) mice. Glands were processed for the analysis of differentially expressed mRNAs by using CodeLink Bioarrays and Affymetrix GeneChips. Data were evaluated with bioinformatics and statistical software. Results: Our results show that sex significantly influences the expression of thousands of genes in lacrimal glands of MRL/lpr and NOD mice. The immune nature of this glandular response is very dependent on the Sjögren syndrome model. Lacrimal glands of female, as compared with male, MRL/lpr mice contain a significant increase in the expression of genes related to inflammatory responses, antigen processing, and chemokine pathways. In contrast, it is the lacrimal tissue of NOD males, and not females, that presents with a significantly greater expression of immune-related genes. Conclusions: These data support our hypothesis that sex-related differences in gene expression contribute to lacrimal gland disease in Sjögren syndrome. Our findings also suggest that factors in the lacrimal gland microenvironment are critically important in mediating these sex-associated immune effects.
Lopez MJ, Seyed-Razavi Y, Jamali A, Harris DL, Hamrah P. The Chemokine Receptor CXCR4 Mediates Recruitment of CD11c+ Conventional Dendritic Cells Into the Inflamed Murine Cornea. Invest Ophthalmol Vis Sci 2018;59(13):5671-5681.Abstract
Purpose: The cornea contains distinct populations of antigen-presenting cells (APCs), including conventional dendritic cells (cDCs). Little is known about the molecular mechanisms involved in cDCs homing and recruitment into the naïve and inflamed cornea. The purpose of this study was to investigate the presence of CXCR4 and its ligand CXCL12 in the murine cornea and its role in cDC migration during corneal inflammation. Methods: The expression of CXCR4 and CXCL12 in naïve and suture-inflamed murine corneas was assessed by whole-mount staining, flow cytometry, and quantitative PCR. The role of CXCR4 in recruitment into inflamed corneas was investigated using adoptive transfer of cDCs blocked with neutralizing antibody against CXCR4. Results: We show the chemokine receptor CXCR4 to be expressed on 51.7% and 64.8% of total corneal CD11c+ cDCs, equating to 98.6 ± 12.5 cells/mm2 in the peripheral and 64.7 ± 10.6 cells/mm2 in the central naïve cornea, respectively. Along with a 4.5-fold increase in CXCL12 expression during inflammation (P < 0.05), infiltrating cDCs also expressed CXCR4 in both the peripheral (222.6 ± 33.3 cells/mm2; P < 0.001) and central cornea (161.9 ± 23.8 cells/mm2; P = 0.001), representing a decrease to 31.0% and 37.3% in the cornea, respectively. Further, ex vivo blockade (390.1 ± 40.1 vs. 612.1 ± 78.3; P = 0.008) and local blockade (263.5 ± 27.1 vs. 807.5 ± 179.5, P < 0.001) with anti-CXCR4 neutralizing antibody resulted in a decrease in cDCs homing into the cornea compared with cells pretreated with isotype controls. Conclusions: Our results demonstrate that corneal CXCL12 plays a direct role in CXCR4+ cDC recruitment into the cornea. The CXCR4/CXCL12 axis is therefore a potential target to modulate corneal inflammatory responses.
Jurkunas UV. Fuchs Endothelial Corneal Dystrophy Through the Prism of Oxidative Stress. Cornea 2018;37 Suppl 1:S50-S54.Abstract
The corneal endothelium (CE) is vital for maintaining the water balance and clarity of the cornea. The CE is a cell layer that is particularly susceptible to aging because of its postmitotic arrest, high metabolic activity involving pumping of ions, and lifelong exposure to ultraviolet light. Despite gradual age-related cell loss, a sufficient number of CE cells are preserved during the lifespan of an individual. However, in conditions such as Fuchs endothelial corneal dystrophy (FECD), permanent loss of CE cells leads to corneal edema and loss of vision requiring corneal transplantation. FECD is a genetic and oxidative stress disorder manifested by abnormal cell-matrix interactions and expedited cellular aging culminating in cellular death. Because the endothelium has minimal replicative capacity in vivo and an inability to replace its genome, it is particularly prone to cumulative DNA damage acquired throughout life. In FECD, the underlying genetic defects make the CE genome even more vulnerable to this damage, to the point of causing mitochondrial dysfunction, mitochondrial membrane potential loss, and excessive mitophagy activation. Endogenous and exogenous intracellular stressors alter the synthetic footprint of CE cells, leading to endothelial-mesenchymal transition and secretion of aberrant extracellular matrix (in the form of guttae), resembling scar formation in other organs. In turn, the guttae or endothelial scars contribute to a vicious cycle of FECD pathogenesis and, by further inducing endothelial-mesenchymal transition and oxidant-antioxidant imbalance, perpetuate the molecular changes of the degenerating endothelium.
Kobashi H, Rong SS, Ciolino JB. Transepithelial versus epithelium-off corneal crosslinking for corneal ectasia. J Cataract Refract Surg 2018;44(12):1507-1516.Abstract
This review compared the clinical results of transepithelial corneal crosslinking (CXL) to epithelium-off (epi-off) CXL in progressive corneal ectasia using a metaanalysis. The Cochrane databases and Medline were searched for randomized controlled trials (RCTs). Seven RCTs involving 505 eyes that met the eligibility criteria were identified. The epi-off CXL group showed significantly better outcomes in postoperative changes in maximum keratometry (K) during 1-year observation periods. Transepithelial CXL resulted in significantly greater post-treatment central corneal thickness and best spectacle-corrected visual acuity (BSCVA). The presence of a postoperative demarcation line was significantly more frequent after epi-off CXL than that after transepithelial CXL. No statistically significant difference was found between other parameters. Although patients in the transepithelial CXL group demonstrated a greater improvement in BSCVA compared with patients in the epi-off CXL group at the 1 year follow-up, transepithelial CXL had less impact on halting progressive corneal ectasia in terms of maximum K than epi-off CXL.
Tatematsu Y, Khan Q, Blanco T, Bair JA, Hodges RR, Masli S, Dartt DA. Thrombospondin-1 Is Necessary for the Development and Repair of Corneal Nerves. Int J Mol Sci 2018;19(10)Abstract
Thrombospondin-1-deficient (TSP-1) mice are used as an animal model of Sjögren's Syndrome because they exhibit many of the symptoms associated with the autoimmune type of dry eye found in primary Sjögren's Syndrome. This type of dry eye is linked to the inflammation of the lacrimal gland, conjunctiva, and cornea, and is thought to involve dysfunction of the complex neuronal reflex arc that mediates tear production in response to noxious stimuli on the ocular surface. This study characterizes the structural and functional changes to the corneal nerves that are the afferent arm of this arc in young and older TSP-1 and wild type (WT) mice. The structure and subtype of nerves were characterized by immunohistochemistry, in vivo confocal microscopy, and confocal microscopy. Cytokine expression analysis was determined by Q-PCR and the number of monocytes was measured by immunohistochemistry. We found that only the pro-inflammatory cytokine MIP-2 increased in young corneas of TSP-1 compared to WT mice, but tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-2 (MIP-2) all increased in older TSP-1 mouse corneas. In contrast, CD11b+ pro-inflammatory monocytes did not increase even in older mouse corneas. Calcitonin gene-related peptide (CGRP)-, but not Substance P (SubP)-containing corneal nerves decreased in older, but not younger TSP-1 compared to WT mouse corneas. We conclude that CGRP-containing corneal sensory nerves exhibit distinct structural deficiencies as disease progresses in TSP-1 mice, suggesting that: (1) TSP-1 is needed for the development or repair of these nerves and (2) impaired afferent corneal nerve structure and hence function may contribute to ocular surface dysfunction that develops as TSP-1 mice age.
Webster A, Chintala SK, Kim J, Ngan M, Itakura T, Panjwani N, Argüeso P, Barr JT, Jeong S, Elizabeth Fini M. Dynasore protects the ocular surface against damaging stress. PLoS One 2018;13(10):e0204288.Abstract
Water soluble "vital" dyes are commonly used clinically to evaluate health of the ocular surface; however, staining mechanisms remain poorly understood. Recent evidence suggests that sublethal damage stimulates vital dye uptake by individual living cells. Since cell damage can also stimulate reparative plasma membrane remodeling, we hypothesized that dye uptake occurs via endocytic vesicles. In support of this idea, we show here that application of oxidative stress to relatively undifferentiated monolayer cultures of human corneal epithelial cells stimulates both dye uptake and endocytosis, and that dye uptake is blocked by co-treatment with three different endocytosis inhibitors. Stress application to stratified and differentiated corneal epithelial cell cultures, which are a better model of the ocular surface, also stimulated dye uptake; however, endocytosis was not stimulated, and two of the endocytosis inhibitors did not block dye uptake. The exception was Dynasore and its more potent analogue Dyngo-4a, both small molecules developed to target dynamin family GTPases, but also having off-target effects on the plasma membrane. Significantly, while Dynasore blocked stress-stimulated dye uptake at the ocular surface of ex vivo mouse eyes when treatment was performed at the same time as eyes were stressed, it had no effect when used after stress was applied and the ocular surface was already damaged. Thus, Dynasore could not be working by inhibiting endocytosis. Employing cytotoxicity and western blotting assays, we went on to demonstrate an alternative mechanism. We show that Dynasore is remarkably protective of cells and their surface glycocalyx, preventing damage due to stress, and thus precluding dye entry. These unexpected and novel findings provide greater insight into the mechanisms of vital dye uptake and point the direction for future study. Significantly, they also suggest that Dynasore and its analogues might be used therapeutically to protect the ocular surface and to treat ocular surface disease.
AbuSamra DB, Argüeso P. Lectin-Glycan Interactions in Corneal Infection and Inflammation. Front Immunol 2018;9:2338.Abstract
The cornea is an extraordinary component of vision that functions as the principal barrier to pathogens in the eye while allowing light transmission into the retina. Understanding the cellular and molecular mechanisms that maintain homeostasis in this tissue is the subject of intense scientific study given the high prevalence of corneal disease. Over the past decade, the interactions between lectins and glycans on plasma membranes have emerged as important regulatory factors in corneal biology. In particular, members of the galectin family have been shown to bind multiple β-galactoside-containing receptors to regulate immunopathological processes associated with viral and bacterial infection, transplantation, wound healing, dry eye, angiogenesis, and lymphangiogenesis. In this review, we describe the current understanding of how these surface interactions intersect with different pathways to activate unique cellular responses in cornea as well as their potential therapeutic implications.
Wittmann J, Dieckow J, Schröder H, Hampel U, Garreis F, Jacobi C, Milczarek A, Hsieh KL, Pulli B, Chen JW, Hoogeboom S, Bräuer L, Paulsen FP, Schob S, Schicht M. Plasma gelsolin promotes re-epithelialization. Sci Rep 2018;8(1):13140.Abstract
Woundhealing disorders characterized by impaired or delayed re-epithelialization are a serious medical problem that is painful and difficult to treat. Gelsolin (GSN), a known actin modulator, supports epithelial cell regeneration and apoptosis. The aim of this study was to estimate the potential of recombinant gelsolin (rhu-pGSN) for ocular surface regeneration to establish a novel therapy for delayed or complicated wound healing. We analyzed the influence of gelsolin on cell proliferation and wound healing in vitro, in vivo/ex vivo and by gene knockdown. Gelsolin is expressed in all tested tissues of the ocular system as shown by molecular analysis. The concentration of GSN is significantly increased in tear fluid samples of patients with dry eye disease. rhu-pGSN induces cell proliferation and faster wound healing in vitro as well as in vivo/ex vivo. TGF-β dependent transcription of SMA is significantly decreased after GSN gene knockdown. Gelsolin is an inherent protein of the ocular system and is secreted into the tear fluid. Our results show a positive effect on corneal cell proliferation and wound healing. Furthermore, GSN regulates the synthesis of SMA in myofibroblasts, which establishes GSN as a key protein of TGF-β dependent cell differentiation.
Momtazi L, Dartt DA, Nilsen O, Eidet JR. Molecular layer deposition builds biocompatible substrates for epithelial cells. J Biomed Mater Res A 2018;106(12):3090-3098.Abstract
The demand for novel biocompatible materials as surface coating in the field of regenerative medicine is high. We explored molecular layer deposition (MLD) technique for building surface coatings and introduced a new group of substrates consisting of amino acids, or nucleobases, and the biocompatible metal titanium. The substrates were built from titanium tetraisopropoxide (TTIP) with l-lysine, glycine, l-aspartic acid, l-arginine, thymine, uracil, and adenine. Substrates based on zirconium chloride and terephthalic acid were also included. Titanium oxide (TiO ) substrates made by atomic layer deposition and uncoated cover slips served as controls. Rat conjunctival epithelial goblet cells were grown in RPMI 1640 and RT-PCR, immunofluorescence, cell attachment, proliferation, and viability were analyzed. Cells cultured on MLD and uncoated substrates were proliferating (positive for Ki67). Cell attachment after 3 h of culture on MLD substrates was similar to uncoated coverslips (p > 0.05). Compared to uncoated coverslips, cell proliferation assayed with alamarBlue® after 4 days was significantly higher on all MLD substrates (p < 0.05), whereas terephthalic acid-containing MLD substrates reduced proliferation (p < 0.01). Viability assessed by LIVE/DEAD® was high (>85%) for all substrates after 5 days. The novel MLD technique is promising for building biocompatible substrates that direct epithelial cell growth. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3090-3098, 2018.
Yazdani M, Chen X, Tashbayev B, Utheim ØA, Ræder S, Lagli N, Stojanovic A, Dartt DA, Utheim TP. Tear Production Levels and Dry Eye Disease Severity in a Large Norwegian Cohort. Curr Eye Res 2018;43(12):1465-1470.Abstract
PURPOSE: To determine if the Schirmer I test (without anesthesia) cut-off value is a predictor of dry eye severity in a large Norwegian cohort of dry eye disease (DED) patients, which are grouped into six levels of tear production. METHODS: Patients (n = 1090) with DED of different etiologies received an extensive dry eye work-up: osmolarity (Osm), tear meniscus height (TMH), tear film break-up time (TFBUT), ocular protection index (OPI), ocular surface staining (OSS), Schirmer I test (ST), meibum expressibility (ME), and meibum quality (MQ). Classification of dry eye severity level (DESL) and diagnosis of meibomian gland dysfunction (MGD) were also included. The cohort was divided into six groups: below and above cut-off values of 5 (groups 1 and 2), 10 (groups 3 and 4), and 15 mm (groups 5 and 6) of ST. Mann-Whitney test and Chi-Square test were used for group comparison of parameters (p ≤ 0.05). RESULTS: The groups 1, 3, and 5 had values indicating more severe DED than the groups 2, 4, 6 with significant difference in DESL, Osm, TFBUT, OPI, OSS, and TMH. Regardless of the choice of cut-off values, there was no statistically significant difference in ME, MQ, and MGD between groups below and above selected cut-off value. When gender difference was considered in each group, significant difference was only observed for DESL (groups 2, 4, and 5), TFBUT (groups 2, 4, and 5), OPI (groups 2 and 6), and ME (group1). CONCLUSIONS: Schirmer I is a robust discriminator for DESL, Osm, TFBUT, OPI, OSS, and TMH, but not for ME, MQ, and MGD. Patients with lower tear production levels presented with more severe DED at all three defined cut-off values. Interestingly, the differences in the mean values of DESL were minimal although statistically significant. Thus, the clinical value of different Schirmer levels appears to be limited.
Xie H-T, Sullivan DA, Chen D, Hatton MP, Kam WR, Liu Y. Biomarkers for Progenitor and Differentiated Epithelial Cells in the Human Meibomian Gland. Stem Cells Transl Med 2018;7(12):887-892.Abstract
The meibomian gland (MG) is a sebaceous gland that secretes through a holocrine process. Because such secretion requires the destruction of MG acinar epithelial cells, they need constant renewal and differentiation. The processes that promote these regenerative events in the human MG are unknown, nor is it known how to distinguish MG progenitor and differentiated cells. We discovered that Lrig1 and DNase2 serve as biomarkers for human MG progenitor and differentiated cells, respectively. Lrig1 is expressed in MG basal epithelial cells in the acinar periphery, a location where progenitor cells originate in sebaceous glands. DNase2 is expressed in the differentiated epithelial cells of the MG central acinus. Furthermore, proliferation stimulates, and differentiation suppresses, Lrig1 expression in human MG epithelial cells. The opposite is true for DNase2 expression. Our biomarker identification may have significant value in clinical efforts to restore MG function and to regenerate MGs after disease-induced dropout. Stem Cells Translational Medicine 2018;7:887-892.
Singh RB, Batta P. Herpes simplex virus keratitis mimicking Acanthamoeba keratitis: a clinicopathological correlation. BMJ Case Rep 2018;2018Abstract
A 36-year-old male, soft contact lens wearer was referred by his primary ophthalmologist for corneal ulcer of the right eye (OD), which was persistent despite topical fluoroquinolone therapy for 1 month. A ring-shaped infiltrate typically seen in Acanthamoeba infection was noted, and topical therapy with chlorhexidine and polyhexamethylene biguanide was initiated. However, the patient's condition deteriorated over the next several weeks; thus, diagnostic and therapeutic penetrating keratoplasty was performed. The postoperative immunohistochemical analysis suggested a diagnosis of herpes simplex virus (HSV) keratitis. The patient ultimately improved after initiation of oral valacyclovir following penetrating keratoplasty. We report a case of a commonly encountered clinical entity, HSV keratitis, with an atypical clinical presentation, masquerading as Acanthamoeba keratitis.
Kobashi H, Ciolino JB. Innovative Development of Contact Lenses. Cornea 2018;37 Suppl 1:S94-S98.Abstract
Contact lenses have been a common means of vision correction for more than half a century. Recent developments have raised the possibility that the next few decades will see a considerable broadening of the range of applications for contact lenses, with associated expansions in the number and type of individuals who consider them a valuable option. The novel applications of contact lenses include treatment platforms for myopic progression, biosensors, and ocular drug delivery. Orthokeratology has shown the most consistent treatment for myopia control with the least side effects. Recent work has resulted in commercialization of a device to monitor intraocular pressure for up to 24 hours, and extensive efforts are underway to develop a contact lens sensor capable of continuous glucose tear film monitoring for the management of diabetes. Other studies on drug-eluting contact lenses have focused on increasing the release duration through molecular imprinting, use of vitamin E, and increased drug binding to polymers by sandwiching a poly (lactic-co-glycolic acid) layer in the lens. This review demonstrates the potential for contact lenses to provide novel opportunities for refractive management, diagnosis, and management of diseases.
Aggarwal S, Cavalcanti BM, Regali L, Cruzat A, Trinidad M, Williams C, Jurkunas UV, Hamrah P. In Vivo Confocal Microscopy Shows Alterations in Nerve Density and Dendritiform Cell Density in Fuchs' Endothelial Corneal Dystrophy. Am J Ophthalmol 2018;196:136-144.Abstract
PURPOSE: To evaluate corneal nerve and immune cell alterations in Fuchs' endothelial corneal dystrophy (FECD) and pseudophakic bullous keratopathy (PBK) by laser in vivo confocal microscopy (IVCM) as correlated to corneal sensation and endothelial cell loss. DESIGN: Prospective, cross-sectional, controlled study. METHODS: Thirty-three eyes with FECD were compared to 13 eyes with PBK and 17 normal age-matched control eyes at a tertiary referral center. FECD was classified into early (without edema) and late stage (with edema). Corneal IVCM and esthesiometry were performed. Corneal nerve and immune dendritiform cell (DC) alterations were evaluated and correlated to clinical parameters. RESULTS: FECD and PBK eyes showed significantly (P = .001) diminished total nerve length (11.5 ± 1.3 and 2.9 ± 0.7 mm/mm) and number (8.8 ± 1.1 and 2.2 ± 0.4 n/frame), compared to controls (23.3 ± 8.1 mm/mm and 25.9 ± 1.3 n/frame). Decreased nerves corresponded to diminished sensation in FECD (4.9 ± 0.2 cm; R = 0.32; P = .045), compared to controls (5.9 ± 0.04 cm). Early- and late-stage FECD showed significantly reduced total nerve length (13.1 ± 1.4 and 9.9 ± 1.2 mm/mm, respectively) and number (8.2 ± 2.5 and 6.5 ± 2.1 n/frame), compared to controls (P < .001). DC density was significantly increased in FECD (57.8 ± 10.4 cells/mm; P = .01), but not in PBK (47.7 ± 11.6 cells/mm; P = .60) compared to controls (22.5 ± 4.5 cells/mm). A subset of early FECD patients (7/22) demonstrated very high DC density (>100/mm). CONCLUSION: IVCM demonstrates profound diminishment of subbasal corneal nerves in early- and late-stage FECD and in PBK, correlating to decreased sensation. Increased DC density in early FECD demonstrates potential subclinical inflammation. The data suggest that reduction in subbasal nerves and increased immune activation may play a role in the pathophysiology of FECD.

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