Explorative study of interleukin levels in the human cornea

Meta-Analysis of Keratoconus Transcriptomic Data Revealed Altered RNA Editing Levels Impacting Keratin Genomic Clusters

Introduction

Keratoconus (KC) is an ocular disorder with a multifactorial origin. Transcriptomic analyses (RNA-seq) revealed deregulations of coding (mRNA) and non-coding RNAs (ncRNAs) in KC, suggesting that mRNA-ncRNA co-regulations can promote the onset of KC. The present study investigates the modulation of RNA editing mediated by the adenosine deaminase acting on dsRNA (ADAR) enzyme in KC.

Materials

The level of ADAR-mediated RNA editing in KC and healthy corneas were determined by two indexes in two different sequencing datasets. REDIportal was used to localize known editing sites, whereas new putative sites were de novo identified in the most extended dataset only and their possible impact was evaluated. Western Blot analysis was used to measure the level of ADAR1 in the cornea from independent samples.

Results

KC was characterized by a statistically significant lower RNA-editing level compared to controls, resulting in a lower editing frequency, and less edited bases. The distribution of the editing sites along the human genome showed considerable differences between groups, particularly relevant in the chromosome 12 regions encoding for Keratin type II cluster. A total of 32 recoding sites were characterized, 17 representing novel sites. JUP, KRT17, KRT76, and KRT79 were edited with higher frequencies in KC than in controls, whereas BLCAP, COG3, KRT1, KRT75, and RRNAD1 were less edited. Both gene expression and protein levels of ADAR1 appeared not regulated between diseased and controls.

Conclusions

Our findings demonstrated an altered RNA-editing in KC possibly linked to the peculiar cellular conditions. The functional implications should be further investigated.

Keratoconus patients exhibit a distinct ocular surface immune cell and inflammatory profile

Inflammatory factors have been considered to contribute to keratoconus (KC) pathogenesis. This study aims to determine the immune cells subsets and soluble inflammatory factor profile on the ocular surface of KC patients. 32 KC subjects (51 eyes) across different grades of severity and 15 healthy controls (23 eyes) were included in the study. Keratometry and pachymetry measurements were recorded. Ocular surface immune cells (collected by ocular surface wash) immunophenotyped using flow cytometry include leukocytes, neutrophils, macrophages, natural killer (NK) cells, pan-T cells, gamma delta T (γδT) cells and NKT cells. Tear fluid collected using Schirmer's strip was used to measure 50 soluble factors by multiplex ELISA. Proportions of activated neutrophils, NK cells and γδT cells were significantly increased in KC patients. Significantly higher levels of tear fluid IL-1β, IL-6, LIF, IL-17A, TNFα, IFNα/β/γ, EPO, TGFβ1, PDGF-BB, sVCAM, sL-selectin, granzyme-B, perforin, MMP2, sFasL and IgE, along with significantly lower levels of IL-1α and IL-9 were observed in KC patients. Alterations observed in few of the immuno-inflammatory parameters correlated with grades of disease, allergy, eye rubbing and keratometry or pachymetry measurements. The observation implies a distinct immuno-inflammatory component in KC pathogenesis and its potential as an additional therapeutic target in KC management.

The anti-scarring role of Lycium barbarum polysaccharide on cornea epithelial-stromal injury

PURPOSE

Cornea epithelial-stromal scarring is related to the differentiation of fibroblasts into opaque myofibroblasts. Our study aims to assess the effectiveness of Lycium barbarum polysaccharide (LBP) solution as a pre-treatment in minimizing corneal scarring.

METHODS

Human corneal fibroblasts were cultured in a three-dimensional collagen type I-based hydrogel in an eye-on-a-chip model. Fibroblasts were pre-treated with 2 mg/mL LBP for 24 h, followed by another 24-h incubation with 10 ng/mL transforming growth factor-beta 1 (TGF-β1) to induce relevant physiological events after stromal injury. Intracellular pro-fibrotic proteins, extracellular matrix proteins, and pro-inflammatory cytokines that involved in fibrosis, were assessed using immunocytochemistry and enzyme-linked immunosorbent assays.

RESULTS

Compared to the positive control TGF-β1 group, LBP pre-treated cells had a significantly lower expression of alpha-smooth muscle actin, marker of myofibroblasts, vimentin (p < 0.05), and also extracellular matrix proteins both collagen type II and type III (p < 0.05) that can be found in scar tissues. Moreover, LBP pre-treated cells had a significantly lower secretion of pro-inflammatory cytokines interleukin-6 and interleukin-8 (p < 0.05). The cell-laden hydrogel contraction and stiffness showed no significant difference between LBP pre-treatment and control groups. Fibroblasts pretreated with LBP as well had reduced angiogenic factors expression and suppression of undesired proliferation (p < 0.05).

CONCLUSION

Our results showed that LBP reduced both pro-fibrotic proteins and pro-inflammatory cytokines on corneal injury in vitro. We suggest that LBP, as a natural Traditional Chinese Medicine, may potentially be a novel topical pre-treatment option prior to corneal refractive surgeries with an improved prognosis.

Biochemical Markers and Alterations in Keratoconus

Keratoconus (KC) is a corneal ectatic condition characterized by focal structural changes, resulting in progressive thinning, biomechanical weakening, and steeping of the cornea that can lead to worsening visual acuity due to irregular astigmatism and corneal scarring in more advanced cases. It is a relatively common ectatic disease of the cornea predominantly affecting the younger population. Despite its worldwide prevalence, its incidence is rather varied with a higher incidence among the Middle Eastern and South Asian population. Dysregulated corneal extracellular matrix remodeling underlies KC pathogenesis. However, a lack of absolute clarity regarding the factors that initiate and drive progression poses a significant challenge in its prevention and management. KC is a complex multifactorial disease as it is associated with a wide variety of etiological factors such as environmental stimuli/insults, oxidative stress, genetic predisposition, comorbidities, and eye rubbing. A series of studies using corneal tissues (epithelium, stroma), cultured corneal fibroblasts/keratocytes, tear fluid, aqueous humor, and blood from KC subjects has reported significant alterations in various biochemical factors such as extracellular matrix components, cellular homeostasis regulators, inflammatory factors, hormones, metabolic products, and chemical elements. It has become apparent that alterations in the biochemical mediators (related to various etiologies) could contribute to KC pathogenesis by altering the dynamics of extracellular matrix remodeling events such as collagen deposition, degradation, and cross-linking in the cornea. Determining key disease contributing biochemical mediators would aid in disease monitoring, prediction or abatement of disease progression, and development of targeted therapeutics to improve disease prognosis.

A Systematic Review on Cornea Epithelial-Stromal Homeostasis

INTRODUCTION

This review aims to summarise the role of different cells, genes, proteins and lipid in regulating cornea epithelial-stromal homeostasis.

METHODS

We performed an Entrez PubMed literature search using keywords "human," "cornea," "epithelial," "stromal," "homeostasis," "fibrosis response," and "pathogenesis" on 24th of September 2019, resulting in 35 papers, of which 18 were chosen after filtering for "English language" and "published within 10 years" as well as curation for relevance by the authors.

RESULTS

The 18 selected papers showed that corneal epithelial cells, fibroblasts and telocytes, together with genes such as Klf4, Pax6 and Id found in the cells, play important roles in achieving homeostasis to maintain corneal integrity and transparency. Proteins classified as pro-fibrotic ligands and anti-fibrotic ligands are responsible for regulating cornea stromal fibrosis and extracellular matrix deposition, thus regulators of scar formation during wound healing. Anti-inflammatory ligands and wound repairing ligands are critical in eliciting protective inflammation and promoting epithelial healing, respectively. Protein receptors located on cellular membrane play a role in maintaining intercellular connections as well as corneal hydration.

DISCUSSION/CONCLUSION

These studies prompt development of novel therapeutic strategies such as tear drops or ointments that target certain proteins to maintain corneal homeostasis. However, more in vitro and in vivo studies are required to prove the effectiveness of exogenous administration of molecules in improving healing outcome. Hence, future investigations of the molecular pathways highlighted in this review will reveal novel therapeutic tools such as gene or cell therapy to treat corneal diseases.

Expression of cytokines in aqueous humor from fungal keratitis patients

BACKGROUND

Although a series of reports on corneal fungal infection have been published, studies on pathogenic mechanisms and inflammation-associated cytokines remain limited. In this study, aqueous humor samples from fungal keratitis patients were collected to examine cytokine patterns and cellular profile for the pathogenesis of fungal keratitis.

METHODS

The aqueous humor samples were collected from ten patients with advanced stage fungal keratitis. Eight aqueous humor samples from patients with keratoconus or corneal dystrophy were taken as control. Approximately 100 μl to 300 μl of aqueous humor in each case were obtained for examination. The aqueous humor samples were centrifuged and the cells were stained and examined under optical microscope. Bacterial and fungal cultures were performed on the aqueous humor and corneal buttons of all patients. Cytokines related to inflammation including IL-1β, IL-6, IL-8, IL-10, TNF-α, and IFN-γ were examined using multiplex bead-based Luminex liquid protein array systems.

RESULTS

Fungus infection was confirmed in these ten patients by smear stains and/or fungal cultures. Bacterial and fungal cultures revealed negative results in all aqueous humor specimens. Polymorphonuclear leukocytes were the predominant infiltrating cells in the aqueous humor of fungal keratitis. At the advanced stages of fungal keratitis, the levels of IL-1β, IL-6, IL-8, and IFN-γ in the aqueous humor were significantly increased when compared with control (p<0.01). The levels of IL-10 and TNF-α also showed an ascending trend but with no statistical significance.

CONCLUSIONS

High concentration of IL-1β, IL-6, IL-8, and IFN-γ in the aqueous humor was associated with fungal keratitis.

Mitochondrial dysfunction and oxidative stress in corneal disease

The cornea is the anterior transparent surface and the main refracting structure of the eye. Mitochondrial dysfunction and oxidative stress are implicated in the pathogenesis of inherited (e.g. Kearns Sayre Syndrome) and acquired corneal diseases (e.g. keratoconus and Fuchs endothelial corneal dystrophy). Both antioxidants and reactive oxygen species are found in the healthy cornea. There is increasing evidence of imbalance in the oxidative balance and mitochondrial function in the cornea in disease states. The cornea is vulnerable to mitochondrial dysfunction and oxidative stress due to its highly exposed position to ultraviolet radiation and high oxygen tension. The corneal endothelium is vulnerable to accumulating mitochondrial DNA (mtDNA) damage due to the post- mitotic nature of endothelial cells, yet their mitochondrial genome is continually replicating and mtDNA mutations can develop and accumulate with age. The unique physiology of the cornea predisposes this structure to oxidative damage, and there is interplay between inherited and acquired mitochondrial dysfunction, oxidative damage and a number of corneal diseases. By targeting mitochondrial dysfunction in corneal disease, emerging treatments may prevent or reduce visual loss.

Deficient repair regulatory response to injury in keratoconic stromal cells

BACKGROUND

Keratoconus manifests as a conical protrusion of the cornea and is characterised by stromal thinning. This causes debilitating visual impairment, which may necessitate corneal transplantation. Hypothetically, many of the pathological features in keratoconus may be manifestations of defects in wound healing; however, as the pathobiology remains unclear, therapeutic targets related to disease mechanisms are currently lacking. This study investigated the protein expression of cytokines which may control stromal wound healing and the effect of an induced secondary injury (SI) on stromal cells from ex vivo human keratoconus and control corneas.

METHODS

Total protein was extracted from stromal cells from human keratoconic and non-keratoconic central corneas (n = 12) with (+SI) and without (-SI) an ex vivo corneal incision wound. The levels of interleukin 1 alpha (IL-1α), fibroblast growth factor 2 (FGF-2), nerve growth factor beta (β-NGF), insulin-like growth factor 1 (IGF-1), tumour necrosis factor alpha (TNF-α), epidermal growth factor (EGF), transforming growth factor beta 1 (TGF-β1), platelet-derived growth factor (PDGF) and hepatocyte growth factor (HGF) were quantified using chemiluminescence-based immunoarrays.

RESULTS

In stromal cells from -SI keratoconic corneas (compared with -SI normal corneas), the levels of IL-1α, IGF-1, TNF-α and TGF-β1 were increased and the levels of HGF and β-NGF were reduced. These alterations were also observed in +SI non-keratoconic corneas (compared with -SI non-keratoconic corneas). In stromal cells from +SI keratoconic corneas (compared with -SI keratoconic corneas), the quantities of IL-1α, FGF-2, TNF-a, EGF, TGF-a1 and PDGF were decreased.

CONCLUSION

The repair-modulating milieu in keratoconic corneas appears comparable to that in wounded normal corneas. Moreover, wounded keratoconic corneas may be less capable of orchestrating a normal reparative response. These novel findings may improve our understanding of the pathobiology and may facilitate the identification of potential biological targets and therapeutic agents to advance the clinical management of this disorder.

Effects of eye rubbing on the levels of protease, protease activity and cytokines in tears: relevance in keratoconus

BACKGROUND

Proteases, protease activity and inflammatory molecules in tears have been found to be relevant in the pathogenesis of keratoconus. We sought to determine the influence of eye rubbing on protease expression, protease activity and concentration of inflammatory molecules in tears.

METHODS

Basal tears were collected from normal volunteers before and after 60 seconds of experimental eye rubbing. The total amount of matrix metalloproteinase (MMP)-13 and inflammatory molecules interleukin (IL)-6 and tumour necrosis factor (TNF)-α in the tear samples were measured using specific enzyme-linked immunosorbent assays (ELISA). Tear collagenase activity was investigated using a specific activity assay.

RESULTS

The concentrations of MMP-13 (51.9 ± 34.3 versus 63 ± 36.8 pg/ml, p = 0.006), IL-6 (1.24 ± 0.98 versus 2.02 ± 1.52 pg/ml, p = 0.004) and TNF-α (1.16 ± 0.74 versus 1.44 ± 0.66 pg/ml, p = 0.003) were significantly increased in normal subjects after eye rubbing. The experimental eye rub did not alter significantly the collagenase activity (5.02 ± 3 versus 7.50 ± 3.90 fluorescent intensity units, p = 0.14) of tears.

CONCLUSION

Eye rubbing for 60 seconds increased the level of tear MMP-13, IL-6 and TNF-α in normal study subjects. This increase in protease, protease activity and inflammatory mediators in tears after eye rubbing may be exacerbated even further during persistent and forceful eye rubbing seen in people with keratoconus and this in turn may contribute to the progression of the disease.

Use of topical human amniotic fluid in the treatment of acute ocular alkali injuries in mice

PURPOSE

To evaluate the efficacy of topical human amniotic fluid (HAF) in the treatment of ocular acute alkali burns in mice.

DESIGN

Experimental study.

METHODS

A chemical burn with 2 microl of sodium hydroxide 0.15 mol/l was created in one eye of 30 mice. The animals were divided into gender- and age-matched groups according to the topical treatment that was administered: group 1 was treated with preterm HAF (n = 10 mice); group 2 was treated with term HAF (n = 10 mice), and group 3 was treated with saline solution (n = 10 mice). Treatment consisted of one drop that was applied to the burned eye five times per day (week one), and three times per day (week two). The epithelial defect was photographed and measured on days two and four. Ocular burn damage was assessed at days two, seven, and 14 after a pre-established classification. On day 14, both eyes of each mouse were enucleated and assessed histopathologically.

RESULTS

Median epithelial defect (interquartile range [IQR], 25th, 75th percentile) at day four was 9.93% (IQR, 8.57, 11.27) for group 1, 7.30% (IQR, 5.96, 8.97) for group 2, and 18.92% (IQR, 11.71, 27.64) for group 3 (P < .0076). The overall change (difference in slope) in ocular burn score between days 2 and 14 was -0.127 (P = .009) in group 1 vs 3, -0.134 (P = .012) in group 2 vs 3, and 0.007 (P = .88) in group 1 vs 2. On histologic examination saline solution-treated corneas had more inflammatory cells and blood vessels than HAF-treated corneas.

CONCLUSION

Topical preterm/term HAF was an effective topical therapy for limiting the damage after acute alkali burns of the eye in this animal model.

Enhanced release of IL-6 and IL-8 into tears in various anterior segment eye diseases

OBJECTIVE

To determine the levels of interleukin 6 (IL-6) and interleukin 8 (IL-8/CXCL-8) in tears collected from the eyes of normal individuals and of patients with different irritative eye diseases, in order to acquire information on the immunological changes occurring during the early postoperative period following various forms of eye surgery, including penetrating keratoplasty (PKP).

METHODS

IL-6 and IL-8 levels were measured with the aid of human ultrasensitive ELISA kits in the non-stimulated tears of patients in the early postoperative period following PKP or cataract operation, and of patients with acute bacterial conjunctivitis or with a corneal foreign body. The IL-6 and IL-8 concentrations, the total amounts released in a given time and the rates of their release were calculated.

RESULTS

A significant increase in IL-6 release was observed in all patient groups compared with the normal controls (p < or = 0.003). The IL-8 release levels were significantly higher in the tears of all patient groups (p < or = 0.03), except for the cataract operation group, where the IL-8 release was not significantly higher (p = 0.053) than in the control samples. No significant differences in IL-6 or IL-8 release were observed when the various patient groups were compared with each other.

CONCLUSION

The release of IL-6 and IL-8 into the tears is enhanced in various anterior segment eye diseases, and this may be used as an indicator of various inflammatory reactions in the early postoperative period.

The effect of interleukin-1 on cytokine gene expression by human corneal epithelial cells

The purpose of this study was to characterize the pattern of cytokine gene expression by human corneal epithelial cells (HCEC) in response to interleukin-1 (IL-1). Primary cultured HCEC (P-HCEC) or SV40 transformed HCEC (SV40-HCEC) were treated for 6 hr with serum-free growth-media alone or with recombinant human IL-1beta or IL-1alpha (10 ng ml(-1)). 33P labeled cDNA was generated from total RNA, then hybridized to a human cytokine expression array. An autoradiograph was generated for each experimental condition and results analysed semi-quantitatively. Reverse transcription polymerase chain reaction (RT-PCR) was performed to detect mRNA for IL-8, growth related oncogene-beta (GRO-beta), intercellular adhesion molecule (ICAM)-1 and Ephrin A5. P-HCEC and SV40-HCEC demonstrated comparable cytokine profiles. For P-HCEC (n=2) the expression of 35 genes was upregulated or only detectable following IL-1beta treatment whereas the expression of nine genes was downregulated or undetectable after IL-1beta treatment. In SV40-HCEC (n=3), the expression of 48 genes was upregulated or only detectable following IL-1beta treatment and the expression of 10 genes was downregulated or undetectable after IL-1beta treatment. Some genes that demonstrated increased expression included cadherin-5, ICAM-1, GRO-alpha, GRO-beta, GRO-gamma, Activin A (bA subunit), tumor necrosis factor-alpha, IL-6, and IL-8. Genes that showed decreased expression included the chemokine receptor-CXCR-4, ciliary neurotrophic factor (CNTF), c-kit ligand, Ephrin A5, G-protein coupled receptor RDC-1 and FGF family FGFR2. Bayesian analysis of the SV40-HCEC data (n=3) revealed the expression of 15 genes that were significantly (p<0.05) differentially regulated. Within these 15 genes, the expression of chemokines (GRO-alpha, GRO-beta, IL-8), fibroblast growth factor 13 and the cytokine IL-6 were the most upregulated, while ephrin A5 and chemokine receptor-4 were the most downregulated. IL-1alpha treatment (n=1 P-HCEC; n=1 SV40-HCEC) produced results very similar to IL-1beta treatment. RT-PCR revealed differential regulation of IL-8, GRO-beta, ICAM-1 and ephrin A5 in accordance with gene array data. In conclusion, the data demonstrate that IL-1 treatment of HCEC differentially regulates the expression of other cytokine and related genes, thus adding to the body of evidence that IL-1 is a major mediator of ocular surface inflammatory reactions. Since the expression of a large number of genes can be studied simultaneously, gene array studies such as these offers the advantage of understanding global changes in response to a specific stimulus. Thus our study provides insight in to the ocular surface response in conditions of inflammation and corneal wound healing where the levels of IL-1 are known to be increased.

Interleukin-1beta tear concentration in glaucomatous and ocular hypertensive patients treated with preservative-free nonselective beta-blockers

PURPOSE

To evaluate the ocular surface inflammatory response to the presence of preservatives in nonselective beta-blocker eyedrops.

DESIGN

Prospective, crossover, single-masked, randomized clinical study.

METHODS

study population: Twenty primary open-angle glaucoma or ocular hypertensive patients were divided in two groups, one treated with preservative-free timolol 0.5% (group 1) and the other with preserved timolol 0.5% (group 2) eyedrops. After 60 days of therapy and 3 more weeks of washout, the two groups switched to the other therapy. procedure: At each visit, basal tear samples were collected from the inferior conjunctival fornix for the determination of interleukin (IL)-1beta tear concentrations by an enzyme-linked immunosorbent assay. Intraocular pressure measurement, conjunctival hyperemia, superficial punctate keratitis, and tear film breakup time were evaluated. main outcome measure: IL-1beta concentration in tears following the use of preserved eyedrops.

RESULTS

IL-1beta tear concentrations increased significantly in both groups, compared with baseline values, during preserved timolol therapy. There were no statistically significant changes in hyperemia and superficial punctate keratitis throughout the study in either group. A statistically significant breakup time reduction was observed in both groups after 30 days and after 60 days of preserved therapy.

CONCLUSION

The use of preservatives in timolol 0.5% eyedrops leads to tear film instability and ocular surface inflammatory changes documented by a reduction of breakup time and an increase of IL-1beta tear concentrations. Preservative-free beta-blockers are preferable for long-term hypotensive therapy to prevent ocular surface inflammation.

Pathogenesis of pterygia: role of cytokines, growth factors, and matrix metalloproteinases

Pterygium is a common ocular surface disease apparently only observed in humans. Chronic UV exposure is a widely accepted aetiological factor in the pathogenesis of this disease and this concept is supported by epidemiological data, ray tracing models and histopathological changes that share common features with UV damaged skin. The mechanism(s) of pterygium formation is incompletely understood. Recent data have provided evidence implicating a genetic component, anti-apoptotic mechanisms, cytokines, growth factors, extracellular matrix remodelling (through the actions of matrix metalloproteinases), immunological mechanisms and viral infections in the pathogenesis of this disease. In this review, the current knowledge on pterygium pathogenesis is summarised, highlighting recent developments. In addition, we provide novel data further demonstrating the complexity of this intriguing disease.

Characteristics of the human ocular surface epithelium

An appreciation of the biological characteristics of the human ocular surface epithelium affords us a great insight into the physiology of the human ocular surface in health and disease. Here, we review five important aspects of the human ocular surface epithelium. First, we recognize the discovery of corneal epithelial stem cells, and note how the palisades of Vogt have been suggested as a clinical marker of their presence. Second, we introduce the concept of the gene expression profile of the ocular surface epithelium as arrived at using a new strategy for the systematic analysis of active genes. We also provide a summary of several genes abundantly or uniquely expressed in the human corneal epithelium, namely clusterin, keratin 3, keratin 12, aldehyde dehydrogenase 3 (ALDH3), troponin-I fast-twitch isoform, ssig-h3, cathepsin L2 (cathepsin V), uroplakin Ib, and Ca(2+)-activated chloride channel. Genes related to limbal and conjunctival epithelia are also described. Third, we touch upon the genetic abnormalities thought to be involved with epithelial dysfunction in Meesmann's dystrophy, gelatinous drop-like corneal dystrophy, and the ssig-h3-mutated corneal dystrophies. Fourth, we provide an update regarding the current state of knowledge of the role of cytokines, growth factors and apoptosis in relation to ocular surface homeostasis and tissue reconstruction; the main factors being epidermal growth factor (EGF), keratinocyte growth factor (KGF), hepatocyte growth factor (HGF), transforming growth factor-ss (TGF-ss), and some inflammatory cytokines. Fifth, corneal epithelial barrier function and dysfunction as measured by fluorophotometry is remarked upon, with an explanation of the FL-500 fluorophotometer and its ability to detect corneal epithelial dysfunction at a subclinical level. The research described in this review has undoubtedly generated a complete understanding of corneal epithelial pathophysiology-an understanding that, directly or indirectly, has helped advance the development of new therapeutic modalities for ocular surface reconstruction.

Amniotic membrane transplantation after the primary surgical management of band keratopathy

PURPOSE

To determine the safety and efficacy of amniotic membrane transplantation to restore and maintain a stable corneal epithelium and reduce ocular surface pain after surgical removal of band keratopathy arising from ocular causes.

METHODS

Fifteen patients (16 eyes) from two centers with band keratopathy secondary to ocular causes underwent amniotic membrane transplantation as a graft after surgical removal of calcific deposits with or without the use of ethylenediaminetetraacetic acid. In a prospective, consecutive, uncontrolled case series, the rate of corneal epithelialization and resultant surface stability were recorded over a mean follow-up period of 14.6 months.

RESULTS

Pain from ocular surface instability was the presenting complaint in 14 of 15 (93.3%) patients and resolved in all cases after the procedure even for those who experienced a recurrence of the calcific deposit. Fifteen of 16 eyes (93.7%) achieved epithelialization with a mean time to epithelial healing of 15.2 days. The only eye that failed to heal was subsequently diagnosed with total limbal stem cell deficiency. Visual acuity improved in five of nine (44%) sighted eyes and remained unchanged in four of nine (56%). No patient experienced any major surgical or medical complication after the procedure.

CONCLUSION

Amniotic membrane transplantation represents a safe and effective method to restore a stable corneal epithelium in eyes after primary surgical removal of band keratopathy arising from ocular causes.

Interactions between ocular surface fluid and cornea related to contact lenses

PURPOSE

To improve the quantification of damage to the ocular surface, metabolite levels, electrolyte concentrations, and enzyme activities were assayed in corneal epithelium, stroma and tears.

METHODS

In rabbits, rinsing or contact lenses were used to induce microtrauma. For more severe trauma, experimental injuries were induced with 1 N NaOH. Human accidents included epithelial lesions and mild chemical burns. Enzymatic test systems and electron dispersive X-ray analyses (EDXA) were employed. Corneal hydration was assessed by wet and dry weights. Interleukins were analysed with ELISA.

RESULTS

In contrast to normal eyes, in ocular surface trauma the interaction between tear fluid and cornea played an important part. After wearing contact lenses or rinsing, glucose and lactate levels in the cornea and in tears increased, and ATP and glycogen in the cornea decreased. After epithelial lesions, N-acetylglucose aminidase (NAcGA, E.C.3.2.1.50) was released into the tears. Epithelial defects alone and--much more--rinsing the denuded stromal surface produced an increase of lactate and glucose in tears and a dramatic fall in Na, Cl, and S levels in the stroma. Rinsing with phosphate induced corneal calcification. IL-1 and IL-6 were increased in human corneal buttons from patients with trauma and inflammation.

CONCLUSIONS

Biochemical analyses may be useful to quantify trauma to the ocular surface.

The role of cytokines in corneal immunopathology

Cytokines play an important role in the pathogenesis of various corneal diseases and during corneal graft rejection. Furthermore, cytokines may also play a role in the maintenance of the integrity of the normal cornea. This review focuses on the effects of several cytokines in corneal immunopathology, including the type of the corneal immune response, angiogenesis, chemotaxis, apoptosis, wound healing, corneal disease, and transplantation. It may provide clues for the future treatment of corneal disease and corneal transplantation rejection.

Human beta-defensin 2 is up-regulated during re-epithelialization of the cornea

PURPOSE

Human beta-defensins 1 and 2 (hBD-1, -2) are antimicrobial peptides found in several epithelia including corneal epithelium. Breach of the epithelium leaves the cornea vulnerable to infection so we sought to determine if there is an increase in defensin expression after injury.

METHODS

The epithelium from human cadaver corneas was collected by scraping (original samples). The corneas were then placed into organ culture to permit regeneration of the epithelium. Samples of re-grown epithelium were collected when healing was partially and 100% complete as determined by fluorescein staining. Total RNA was extracted from original and re-grown samples and used in RT-PCR reactions using primers specific for hBD-1 and hBD-2 and the constitutively expressed gene glyceraldehyde-3-phosphate dehydrogenase. Immunoblotting was performed to detect defensin peptide in original and re-grown samples.

RESULTS

hBD-1 mRNA was detected in all original epithelial tissue samples (n = 10) examined suggesting that it is constitutively expressed. hBD-2 mRNA was detectable in only two of the ten samples. Of six corneas placed in to organ culture, hBD-1 mRNA expression was unchanged in the re-grown epithelial samples compared to the original epithelium samples, however the expression of hBD-2 mRNA was markedly increased. hBD-1 and hBD-2 peptides showed the same pattern of expression as their respective transcripts.

CONCLUSIONS

These data show that hBD-2 mRNA and peptide is up-regulated in the corneal epithelium during re-epithelialization which is in keeping with the role of this defensin as an antimicrobial peptide.

Interleukin-6 levels in tears of contact lens wearers

The purpose of this study was to evaluate the presence of interleukin-6 (IL-6) in basal tears of contact lens wearers (n = 18) and nonlens wearers (n = 25). Samples (5 microl) were collected with a microcapillary pipette and evaluated using PAGE electrophoresis and immunoblot analysis. Contact lens-wearing patients had a mean IL-6 level of 43.8 +/- 5.3 pg/5 microl compared with nondetectable IL-6 levels throughout the noncontact lens-wearing population. IL-6 in several patients removed from contact lens wear for 6 days became nondetectable. When these patients were returned to wearing lenses, IL-6 levels increased to their original levels within 24 h. The data presented indicate that an ocular medical device may stimulate IL-6 production.

Local control of alpha1-proteinase inhibitor levels: regulation of alpha1-proteinase inhibitor in the human cornea by growth factors and cytokines

Alpha 1-proteinase inhibitor is a major serine proteinase inhibitor in the human cornea involved in the protection of the avascular corneal tissue against proteolytic damage. This inhibitor is upregulated systemically during infection, inflammation and injury. Cytokines that mediate the acute phase response such as IL-1beta and IL-2 increased alpha1-proteinase inhibitor present in corneal organ culture media. This released inhibitor represented mainly newly synthesized protein. However, IL-6, a general inducer of the acute phase response that upregulates alpha1-proteinase inhibitor in all other tissues and cells tested, failed to alter corneal alpha1-proteinase inhibitor levels over the tested period of 24 h. In addition to IL-1beta and IL-2, alpha1-proteinase inhibitor levels in the corneal organ culture medium increased following the addition of FGF-2 and IGF-I. The effect of the above growth factors and cytokines was relatively fast with maximal induction observed within the first 5 h. Among the tested growth factors and cytokines, IL-1beta was the most potent and increased total corneal alpha1-proteinase inhibitor levels approximately 2.4-fold in the cornea organ culture medium. Newly, synthesized alpha1-proteinase secreted into the medium increased 3.9-fold. In addition to the effect on corneal alpha1-proteinase inhibitor, IL-1beta also increased the amount of alpha1-proteinase inhibitor released by monocytes and macrophages but not by HepG2, CaCo2, and MCF-7 cells within 24 h. These results suggest that the cornea can locally control levels of alpha1-proteinase inhibitor in response to an inflammatory insult.