Characteristics of the human ocular surface epithelium

KLF4 Plays an Essential Role in Corneal Epithelial Homeostasis by Promoting Epithelial Cell Fate and Suppressing Epithelial-Mesenchymal Transition

Purpose

The purpose of this study was to test the hypothesis that KLF4 promotes corneal epithelial (CE) cell fate by suppressing the epithelial–mesenchymal transition (EMT), using spatiotemporally regulated CE-specific ablation of Klf4 in Klf4^Δ/ΔCE (Klf4^LoxP/LoxP/Krt12^rtTA/rtTA/Tet-O-Cre) mice.

Methods

CE-specific ablation of Klf4 was achieved by feeding Klf4^Δ/ΔCE mice with doxycycline chow. The wild-type (WT; normal chow-fed littermates) and the Klf4^Δ/ΔCE histology was compared by hematoxylin and eosin–stained sections; EMT marker expression was quantified by quantitative PCR, immunoblots, and immunofluorescent staining; and wound healing rate was measured by CE debridement using Algerbrush. KLF4 and EMT markers were quantified in human corneal limbal epithelial (HCLE) cells undergoing TGF-β1–induced EMT by quantitative PCR, immunoblots, and immunofluorescent staining.

Results

The epithelial markers E-cadherin, Krt12, claudin-3, and claudin-4 were down-regulated, whereas the mesenchymal markers vimentin, β-catenin, survivin, and cyclin-D1 and the EMT transcription factors Snail, Slug, Twist1, Twist2, Zeb1, and Zeb2 were up-regulated in the Klf4^Δ/ΔCE corneas. The Klf4^Δ/ΔCE cells migrated faster, filling 93% of the debrided area within 16 hours compared with 61% in the WT. After 7 days of wounding, the Klf4^Δ/ΔCE cells that filled the gap failed to regain epithelial characteristics, as they displayed abnormal stratification; down-regulation of E-cadherin and Krt12; up-regulation of β-catenin, survivin, and cyclin-D1; and a 2.5-fold increase in the number of proliferative Ki67⁺ cells. WT CE cells at the migrating edge and the HCLE cells undergoing TGF-β1–induced EMT displayed significant down-regulation of KLF4.

Conclusions

Collectively, these results reveal that KLF4 plays an essential role in CE homeostasis by promoting epithelial cell fate and suppressing EMT.

Clinical and morphological manifestations of aniridia-associated keratopathy on anterior segment optical coherence tomography and in vivo confocal microscopy

PURPOSE

The study aimed to evaluate clinical and morphological changes in the limbal palisades of Vogt (POV) at different stages of aniridia-associated keratopathy (AAK) and to assess possible utility of anterior segment optical coherence tomography (AS-OCT) for the visualization of limbal progenitor structures as it correlates to laser scanning confocal microscopy (LSCM) data.

METHODS

The study involved 32 patients (59 eyes) with congenital aniridia. AAK stage was defined based on biomicroscopy. Assessment of limbal zone and detection of POVs in identical areas was performed by LSCM (HRT3) and AS-OCT (RTVue XR Avanti) using 3D Cornea (En Face mode) and Cornea Cross Line protocols.

RESULTS

Intact and changed POVs were found in 8/8 stage 0 eyes, in 1/21 stage I and 2/13 stage II eyes. Spearman's correlation coefficient in assessing the consistency of the POV diagnostic results by LSCM and AS-OCT for the inferior limbus was r_S = 0.85 (P < 0.05), for the superior limbus - r_S = 0.53 (P < 0.05). AS-OCT was less sensitive for detection of partially present POVs in superior limbus. The negative correlation between AAK stage and POV preservation was determined (r_S = -0.5, P < 0.05). There was no correlation between AAK stage and patient age (r_S = 0.235, P = 0.209). Three patients with PAX6 3' deletion showed stage 0 AAK with intact or slightly disturbed POVs morphology and transparent cornea.

CONCLUSION

AS-OCT may be an additional diagnostic tool for POV visualization in vivo in aniridic patients. Its diagnostic accuracy is subject to selection of anatomic region, nystagmus and the degree of POV degradation.

Construction of Anterior Hemi-Corneal Equivalents Using Nontransfected Human Corneal Cells and Transplantation in Dog Models

Tissue-engineered human anterior hemi-cornea (TE-aHC) is a promising equivalent for treating anterior lamellar keratopathy to surmount the severe shortage of donated corneas. This study was intended to construct a functional TE-aHC with nontransfected human corneal stromal (ntHCS) and epithelial (ntHCEP) cells using acellular porcine corneal stromata (aPCS) as a carrier scaffold, and evaluate its biological functions in a dog model. To construct a TE-aHC, ntHCS cells were injected into an aPCS scaffold and cultured for 3 days; then, ntHCEP cells were inoculated onto the Bowman's membrane of the scaffold and cultured for 5 days under air-liquid interface condition. After its morphology and histological structure were characterized, the constructed TE-aHC was transplanted into dog eyes via lamellar keratoplasty. The corneal transparency, thickness, intraocular pressure, epithelial integrity, and corneal regeneration were monitored in vivo, and the histological structure and histochemical property were examined ex vivo 360 days after surgery, respectively. The results showed that the constructed TE-aHC was highly transparent and composed of a corneal epithelium of 7-8 layer ntHCEP cells and a corneal stroma of regularly aligned collagen fibers and well-preserved glycosaminoglycans with sparsely distributed ntHCS cells, mimicking a normal anterior hemi-cornea (aHC). Moreover, both ntHCEP and ntHCS cells maintained positive expression of their marker and functional proteins. After transplantation into dog eyes, the constructed TE-aHC acted naturally in terms of morphology, structure and inherent property, and functioned well in maintaining corneal clarity, thickness, normal histological structure, and composition in dog models by reconstructing a normal aHC, which could be used as a promising aHC equivalent in corneal regenerative medicine and aHC disorder therapy.

Radiosurgery Alters the Endothelial Surface Proteome: Externalized Intracellular Molecules as Potential Vascular Targets in Irradiated Brain Arteriovenous Malformations

Stereotactic radiosurgery (SRS) is an established treatment for brain arteriovenous malformations (AVMs) that drives blood vessel closure through cellular proliferation, thrombosis and fibrosis, but is limited by a delay to occlusion of 2-3 years and a maximum treatable size of 3 cm. In this current study we used SRS as a priming tool to elicit novel protein expression on the endothelium of irradiated AVM vessels, and these proteins were then targeted with prothrombotic conjugates to induce rapid thrombosis and vessel closure. SRS-induced protein changes on the endothelium in an animal model of AVM were examined using in vivo biotin labeling of surface-accessible proteins and comparative proteomics. LC-MS/MS using SWATH acquisition label-free mass spectrometry identified 280 proteins in biotin-enriched fractions. The abundance of 56 proteins increased after irradiation of the rat arteriovenous fistula (20 Gy, ≥1.5-fold). A large proportion of intracellular proteins were present in this subset: 29 mitochondrial and 9 cytoskeletal. Three of these proteins were chosen for further validation based on previously published evidence for surface localization and a role in autoimmune stimulation: cardiac troponin I (TNNI3); manganese superoxide dismutase (SOD2); and the E2 subunit of the pyruvate dehydrogenase complex (PDCE2). Immunostaining of AVM vessels confirmed an increase in abundance of PDCE2 across the vessel wall, but not a measurable increase in TNNI3 or SOD2. All three proteins co-localized with the endothelium after irradiation, however, more detailed subcellular distribution could not be accurately established. In vitro, radiation-stimulated surface translocation of all three proteins was confirmed in nonpermeabilized brain endothelial cells using immunocytochemistry. Total protein abundance increased modestly after irradiation for PDCE2 and SOD2 but decreased for TNNI3, suggesting that radiation primarily affects subcellular distribution rather than protein levels. The novel identification of these proteins as surface exposed in response to radiation raises important questions about their potential role in radiation-induced inflammation, fibrosis and autoimmunity, but may also provide unique candidates for vascular targeting in brain AVMs and other vascular tissues.

[Diagnostic capabilities of optical coherence tomography and confocal laser scanning microscopy in studying manifestations of aniridia-associated keratopathy]

AIM

to investigate the possible use of anterior segment optical coherence tomography (AS-OCT) and laser scanning confocal microscopy (LSCM) for visualization of limbal progenitor structures and epithelial changes at different stages of aniridia-associated keratopathy (AAK) and to analyze genotype-phenotype correlations of corneal damage.

MATERIAL AND METHODS

Thirty-four patients (63 eyes) with congenital aniridia (CA) were subjected to epithelial cell density measurement in the central cornea as well as epithelial surface assessment with limbal palisades of Vogt (POV) detection in the corresponding sites of the two corneas. For that, LSCM (HRT3) and AS-OCT (RTVue XR Avanti) were performed. Central corneal and epithelial thicknesses were measured using the Pachymetry protocol.

RESULTS

There has been found an increase in the central corneal thickness (CCT) of CA patients, which correlated with the stage of AAK, and a decrease in the central epithelial thickness as compared with healthy subjects (p<0.05). The difference between the basal and wing epithelial cells density in eyes with stages I and II AAK and normal cells density at stage 0 AAK was statistically significant (p<0.05). Intact or disturbed POV were detected in all patients with PAX6 3' deletion. At that, AS-OCT findings highly agreed with LSCM images for both the inferii (r_S=0.85, p<0.05) and superior limbi (r_S=0.53, p<0.05). A negative correlation was established between the stage of AAK and in vivo morphology of POV (r_S=-0.5, p<0.05). However, no correlation was found between the stage of AAK and patient's age (r_S=0.169, p=0.174).

CONCLUSION

AS-OCT and LSCM are both important diagnostic tools for corneal surface monitoring in patients with limbal stem cells deficiency.

Using optical coherence tomography to assess the role of age and region in corneal epithelium and palisades of vogt

Using spectral-domain optical coherence tomography (OCT) to observe the morphology and epithelial thickness (ET) of the palisades of Vogt (POV), and to evaluate the role of age and region on these structures.One hundred twelve eyes of 112 healthy subjects were enrolled and divided into 4 groups: A (0-19), B (20-39), C (40-59), and D (≥60 years old). RTvue-100 OCT was applied on the cornea and the limbus. The morphology of the subepithelial stroma underneath the epithelium of POV was classified into typical and atypical types. Maximum ET of POV was measured manually from OCT images.The positive rate of typical POV in superior, nasal, temporal, and inferior limbus was: Group A: 100%, 69.2%, 65.4%, 100%; Group B: 100%, 73.5%, 61.8%, 94.1%; Group C: 95.8%, 41.7%, 37.5%, 83.3%; Group D: 67.9%, 0%, 3.6%, 25%, showing a significant decreasing tendency with age. The maximum ET of POV in superior, nasal, temporal, and inferior limbus was: Group A: 103.5 ± 10.1 um, 89.2 ± 9.7 um, 87.9 ± 13.6 um, 104.7 ± 14.1 um; Group B: 111.4 ± 15.8 um, 85.3 ± 9.9 um, 88.2 ± 8.6 um, 112.6 ± 19.7 um; Group C: 116.4 ± 16.4 um, 82.8 ± 11.6 um, 87.0 ± 11.6 um, 120.0 ± 25.6 um; Group D: 96.3 ± 17.9 um, 73.8 ± 15.9 um, 79.2 ± 16.7 um, 87.4 ± 18.5 um. Age-dependent change was observed. In general, the maximum ET of POV in superior/inferior quadrants was thicker than the other 2 quadrants.Spectral-domain OCT is a useful tool to observe the limbal microstructure and provide invaluable information. Aging and anatomic regions had significant effects on the microstructure of these areas.

Corneal permeability changes in dry eye disease: an observational study

Background

Diagnostic tests for dry eye disease (DED), including ocular surface disease index (OSDI), tear breakup time (TBUT), corneal fluorescein staining, and lissamine staining, have great deal of variability. We investigated whether fluorophotometry correlated with previously established DED diagnostic tests and whether it could serve as a novel objective metric to evaluate DED.

Methods

Dry eye patients who have had established signs or symptoms for at least 6 months were included in this observational study. Normal subjects with no symptoms of dry eyes served as controls. Each eye had a baseline fluorescein scan prior to any fluorescein dye. Fluorescein dye was then placed into both eyes, rinsed with saline solution, and scanned at 5, 10, 15, and 30 min. Patients were administered the following diagnostic tests to correlate with fluorophotometry: OSDI, TBUT, fluorescein, and lissamine. Standard protocols were used. P < 0.05 was considered significant.

Results

Fifty eyes from 25 patients (DED = 22 eyes, 11 patients; Normal = 28 eyes, 14 patients) were included. Baseline scans of the dry eye and control groups did not show any statistical difference (p = 0.84). Fluorescein concentration of DED and normal patients showed statistical significance at all time intervals (p < 10⁻⁵, 0.001, 0.002, 0.049 for 5, 10, 15, & 30 min respectively). Fluorophotometry values converged towards baseline as time elapsed, but both groups were still statistically different at 30 min (p < 0.01). We used four fluorophotometry scoring methods and correlated them with OSDI, TBUT, fluorescein, and lissamine along with adjusted and aggregate scores. The four scoring schemes did not show any significant correlations with the other tests, except for correlations seen with lissamine and 10 (p = 0.045, 0.034) and 15 min (p = 0.013, 0.012), and with aggregate scores and 15 min (p = 0.042, 0.017).

Conclusions

Fluorophotometry generally did not correlate with any other DED tests, even though it showed capability of differentiating between DED and normal eyes up to 30 min after fluorescein dye instillation. There may be an aspect of DED that is missed in the current regimen of DED tests and only captured with fluorophotometry. Adding fluorophotometry may be useful in screening, diagnosing, and monitoring patients with DED.

Clusterin in the eye: An old dog with new tricks at the ocular surface

The multifunctional protein clusterin (CLU) was first described in 1983 as a secreted glycoprotein present in ram rete testis fluid that enhanced aggregation ('clustering') of a variety of cells in vitro. It was also independently discovered in a number of other systems. By the early 1990s, CLU was known under many names and its expression had been demonstrated throughout the body, including in the eye. Its homeostatic activities in proteostasis, cytoprotection, and anti-inflammation have been well documented, however its roles in health and disease are still not well understood. CLU is prominent at fluid-tissue interfaces, and in 1996 it was demonstrated to be the most highly expressed transcript in the human cornea, the protein product being localized to the apical layers of the mucosal epithelia of the cornea and conjunctiva. CLU protein is also present in human tears. Using a preclinical mouse model for desiccating stress that mimics human dry eye disease, the authors recently demonstrated that CLU prevents and ameliorates ocular surface barrier disruption by a remarkable sealing mechanism dependent on attainment of a critical all-or-none concentration in the tears. When the CLU level drops below the critical all-or-none threshold, the barrier becomes vulnerable to desiccating stress. CLU binds selectively to the ocular surface subjected to desiccating stress in vivo, and in vitro to LGALS3 (galectin-3), a key barrier component. Positioned in this way, CLU not only physically seals the ocular surface barrier, but it also protects the barrier cells and prevents further damage to barrier structure. CLU depletion from the ocular surface epithelia is seen in a variety of inflammatory conditions in humans and mice that lead to squamous metaplasia and a keratinized epithelium. This suggests that CLU might have a specific role in maintaining mucosal epithelial differentiation, an idea that can now be tested using the mouse model for desiccating stress. Most excitingly, the new findings suggest that CLU could serve as a novel biotherapeutic for dry eye disease.

Cytotoxic effect and possible mechanisms of Tetracaine on human corneal epithelial cells in vitro

AIM

To demonstrate the cytotoxic effect and possible mechanisms of Tetracaine on human corneal epithelial (HCEP) cells in vitro.

METHODS

In vitro cultured HCEP cell were treated with Tetracaine hydrochloride at different doses for different times, and their morphology, viability, and plasma membrane permeability were detected by light microscopy, methyl thiazolyl tetrazolium (MTT) assay, and acridine orange (AO)/ethidium bromide (EB) staining, respectively. Their cell cycle progression, phosphatidylserine orientation in plasma membrane, and mitochondrial membrane potential (MTP) were assessed by flow cytometry. DNA fragmentation, ultrastructure, caspase activation, and the cytoplasmic apoptosis inducing factor (AIF) and cytochrome c (Cyt. c) along with the expression of B-cell lymphoma-2 (Bcl-2) family proteins were examined by gel electrophoresis, transmission electron microscope, enzyme linked immunosorbent assay (ELISA), and Western blot, respectively.

RESULTS

After exposed to Tetracaine at doses from 10.0 to 0.3125 g/L, the HCEP cells showed dose- and time-dependent morphological abnormality and typical cytopathic effect, viability decline, and plasma membrane permeability elevation. Tetracaine induced phosphatidylserine externalization, DNA fragmentation, G1 phase arrest, and ultrastructural abnormality and apoptotic body formation. Furthermore, Tetracaine at a dose of 0.3125 g/L also induced caspase-3, -9 and -8 activation, MTP disruption, up-regulation of the cytoplasmic amount of Cyt. c and AIF, the expressions of Bax and Bad, and down-regulation of the expressions of Bcl-2 and Bcl-xL.

CONCLUSION

Tetracaine above 0.3125 g/L (1/32 of its clinical applied dosage) has a dose- and time-dependent cytotoxicity to HCEP cells in vitro, with inducing cell apoptosis via a death receptor-mediated mitochondrion-dependent pathway.

Infectious Keratitis in Limbal Stem Cell Deficiency: Stevens-Johnson Syndrome Versus Chemical Burn

PURPOSE

To investigate the incidence, clinical and microbiological characteristics, risk factors, and therapeutic outcome of infectious keratitis in patients with limbal stem cell deficiency (LSCD) related to Stevens-Johnson syndrome (SJS) and corneal chemical burn.

METHODS

Medical records of 90 eyes of 59 patients who were diagnosed with LSCD resulting from SJS (52 eyes of 29 patients) or corneal chemical burn (38 eyes of 30 patients) were reviewed.

RESULTS

Infectious keratitis developed in 35% of LSCD patients with SJS (18 eyes, 14 patients) and in 18% of those with chemical burn (7 eyes, 7 patients). The development of infectious keratitis in SJS was significantly associated with the severity of chronic ocular surface complications in the cornea, conjunctiva, and eyelids and with the use of topical corticosteroids during the disease course. All cases of infectious keratitis following chemical burn occurred in patients with grade III or IV burn by Roper-Hall classification. Approximately 83% of culture-proven cases of infectious keratitis were bacterial infection, most of which (80%) were caused by Gram-positive bacteria. For resolution of infection, 17 eyes (68%) received surgery in addition to medical treatment, whereas 8 eyes (32%) received medical treatment alone. After infection resolution, the final visual acuity was decreased in 10 eyes (40%) compared with before infection.

CONCLUSIONS

Infectious keratitis is a common complication of LSCD associated with SJS or severe chemical burn to the cornea. Despite medical and surgical treatments, the visual outcome is poor.

PAX6 Isoforms, along with Reprogramming Factors, Differentially Regulate the Induction of Cornea-specific Genes

PAX6 is the key transcription factor involved in eye development in humans, but the differential functions of the two PAX6 isoforms, isoform-a and isoform-b, are largely unknown. To reveal their function in the corneal epithelium, PAX6 isoforms, along with reprogramming factors, were transduced into human non-ocular epithelial cells. Herein, we show that the two PAX6 isoforms differentially and cooperatively regulate the expression of genes specific to the structure and functions of the corneal epithelium, particularly keratin 3 (KRT3) and keratin 12 (KRT12). PAX6 isoform-a induced KRT3 expression by targeting its upstream region. KLF4 enhanced this induction. A combination of PAX6 isoform-b, KLF4, and OCT4 induced KRT12 expression. These new findings will contribute to furthering the understanding of the molecular basis of the corneal epithelium specific phenotype.

Niche Regulation of Limbal Epithelial Stem Cells: Relationship between Inflammation and Regeneration

Human limbal palisades of Vogt are the ideal site for studying and practicing regenerative medicine due to their accessibility. Nonresolving inflammation in limbal stroma is common manifestation of limbal stem cell (SC) deficiency and presents as a threat to the success of transplanted limbal epithelial SCs. This pathologic process can be overcome by transplantation of cryopreserved human amniotic membrane (AM), which exerts anti-inflammatory, antiscarring and anti-angiogenic action to promote wound healing. To determine how AM might exert anti-inflammation and promote regeneration, we have purified a novel matrix, HC-HA/PTX3, responsible for the efficacy of AM efficacy. HC-HA complex is covalently formed by hyaluronan (HA) and heavy chain 1 (HC1) of inter-α-trypsin inhibitor by the catalytic action of tumor necrosis factor-stimulated gene-6 (TSG-6) and are tightly associated with pentraxin 3 (PTX3) to form HC-HA/PTX3. In vitro reconstitution of the limbal niche can be established by reunion between limbal epithelial progenitors and limbal niche cells on different substrates. In 3-dimensional Matrigel, clonal expansion indicative of SC renewal is correlated with activation of canonical Wnt signaling and suppression of canonical bone morphogenetic protein (BMP) signaling. In contrast, SC quiescence can be achieved in HC-HA/PTX3 by activation of canonical BMP signaling and non-canonical planar cell polarity (PCP) Wnt signaling, but suppression of canonical Wnt signaling. HC-HA/PTX3 is a novel matrix mitigating nonresolving inflammation and restoring SC quiescence in the niche for various applications in regenerative medicine.

Novel TACSTD2 mutation in gelatinous drop-like corneal dystrophy

We identified a novel mutation in the tumor-associated calcium signal transducer 2 (TACSTD2) gene in a consanguineous Thai family with gelatinous drop-like corneal dystrophy (GDLD). All affected family members presented with an intense amyloid substance deposited on the cornea, which required surgical management. Genetic analysis of these individuals revealed a homozygous mutation c.79delC, in the TACSTD2 gene. Both parents of these individuals were unaffected and showed heterozygous mutations in the TACSTD2 gene. The mutation produced a truncated protein sequence that might be the cause of GDLD.

TNNI1, TNNI2 and TNNI3: Evolution, regulation, and protein structure-function relationships

Troponin I (TnI) is the inhibitory subunit of the troponin complex in the sarcomeric thin filament of striated muscle and plays a central role in the calcium regulation of contraction and relaxation. Vertebrate TnI has evolved into three isoforms encoded by three homologous genes: TNNI1 for slow skeletal muscle TnI, TNNI2 for fast skeletal muscle TnI and TNNI3 for cardiac TnI, which are expressed under muscle type-specific and developmental regulations. To summarize the current knowledge on the TnI isoform genes and products, this review focuses on the evolution, gene regulation, posttranslational modifications, and structure-function relationship of TnI isoform proteins. Their physiological and medical significances are also discussed.

A Simple and Reliable Technique to Orient Donor Corneal Tissue Using the Radial Width of the Surgical Limbus

PURPOSE

To develop a method based on identification of the widest region of the surgical limbus that can yield quick and accurate orientation of excised human donor corneas.

METHODS

Corneoscleral tissue from donors 49 to 75 years old was marked at the temporal sclera at the time of recovery. Digital images obtained from 20 corneas stored in viewing chambers, retroilluminated and viewed from the endothelial side, were used to quantify the per-degree radial width of the surgical limbus, defined as the distance from the scleral spur to clear cornea. To evaluate differences in radial width among regions, measurements were compared with the intracorneal mean limbal width, and a per-degree z-score was calculated by averaging among corneas. Using images of corneas with the temporal mark masked and the sidedness known, 6 observers were subjected to a blinded trial of 10 corneas to determine the central point of the widest limbal region of each cornea.

RESULTS

Compared with the intracorneal mean, the mean radial width of the surgical limbus was greatest in the superior quadrant, and the difference compared with the inferior, nasal, and temporal quadrants was significant (P < 0.0001). The superior region was identified with 100% accuracy in blinded trials. The average absolute difference between the predicted and actual central point of the superior limbus was 9.75 ± 0.30 degrees.

CONCLUSIONS

The radial width of the surgical limbus is greatest in the superior region of the cornea and can be used as a diagnostic feature to orient donor corneal tissue.

In vivo confocal microscopy of early corneal epithelial recovery in patients with chemical injury

PURPOSE

To investigate the early recovery of corneal epithelium in patients with chemical injuries by the application of in vivo laser scanning confocal microscopy (LSCM).

METHODS

LSCM was performed on 26 eyes of 18 consecutive patients at 1, 2, and 3 months post injury. The morphology of central corneal epithelium and limbus was evaluated. Analysis was performed to compare the densities of corneal apical surface cells (ASCs) and basal epithelial cells (BECs) among different injury severity and time points after injury. The comparisons were also made on inflammatory cells (ICs) and dendritic cells (DCs) infiltrating at the limbus. Moreover, the presence rate of palisades of Vogt (POV) was analyzed at 3 months post injury.

RESULTS

Corneal re-epithelialization was found within 3 months post injury in all eyes, except that persistent epithelium defect was identified in grade IV injured eyes even at 3 months after injury. The injury severity had a significantly negative correlation with the densities of ASCs. However, it had no relationship with the densities of BECs. The density of ICs at the limbus decreased significantly with the prolongation of follow-up, except in the grade I injured eyes. The presence rate of POV also had a significantly negative correlation with injury severity.

CONCLUSION

Epithelial recovery after chemical injury varied in cellular morphology and the densities of ASCs among eyes with different injury severity. The presence rates of POV decreased with the aggravation of injury. LSCM is a feasible method for observing the early recovery of corneal epithelium in patients with chemical injuries.

Spatiotemporally Regulated Ablation of Klf4 in Adult Mouse Corneal Epithelial Cells Results in Altered Epithelial Cell Identity and Disrupted Homeostasis

PURPOSE

In previous studies, conditional disruption of Klf4 in the developing mouse ocular surface from embryonic day 10 resulted in corneal epithelial fragility, stromal edema, and loss of conjunctival goblet cells, revealing the importance of Klf4 in ocular surface maturation. Here, we use spatiotemporally regulated ablation of Klf4 to investigate its functions in maintenance of adult corneal epithelial homeostasis.

METHODS

Expression of Cre was induced in ternary transgenic (Klf4(LoxP/LoxP)/Krt12(rtTA/rtTA)/Tet-O-Cre) mouse corneal epithelium by doxycycline administered through intraperitoneal injections and drinking water, to generate corneal epithelium-specific deletion of Klf4 (Klf4(Δ/ΔCE)). Corneal epithelial barrier function was tested by fluorescein staining. Expression of selected Klf4-target genes was determined by quantitative PCR (QPCR), immunoblotting, and immunofluorescent staining.

RESULTS

Klf4 was efficiently ablated within 5 days of doxycycline administration in adult Klf4(Δ/ΔCE) corneal epithelium. The Klf4(Δ/ΔCE) corneal epithelial barrier function was disrupted, and the basal cells were swollen and rounded after 15 days of doxycycline treatment. Increased numbers of cell layers and Ki67-positive proliferating cells suggested deregulated Klf4(Δ/ΔCE) corneal epithelial homeostasis. Expression of tight junction proteins ZO-1 and occludin, desmosomal Dsg and Dsp, basement membrane laminin-332, and corneal epithelial-specific keratin-12 was decreased, while that of matrix metalloproteinase Mmp9 and noncorneal keratin-17 increased, suggesting altered Klf4(Δ/ΔCE) corneal epithelial cell identity.

CONCLUSIONS

Ablation of Klf4 in the adult mouse corneas resulted in the absence of characteristic corneal epithelial cell differentiation, disrupted barrier function, and squamous metaplasia, revealing that Klf4 is essential for maintenance of the adult corneal epithelial cell identity and homeostasis.

A novel in vivo corneal trans-epithelial electrical resistance measurement device

PURPOSE

To develop a device that is capable of easily measuring corneal transepithelial electrical resistance (TER) and changes in the corneal barrier function.

METHODS

We had previously developed an in vivo method for measuring corneal TER using intraocular electrode. This method can be used to precisely measure the decline of the corneal barrier function after instillation of benzalkonium chloride (BAC). In order to lessen the invasiveness of that procedure, we further refined the method for measuring the corneal TER by developing electrodes that could be placed on the cornea and in the conjunctival sac instead of inserting them into the anterior chamber. TER was then calculated by subtracting the electrical resistance, which lacked the corneal epithelial input, from the whole electrical resistance that was measured between the electrodes. Slit lamp examination and scanning electron microscopy (SEM) were used to determine safety of the new device. Corneal TER changes after exposure to 0.02% BAC were determined using the new device as well as SEM and transmission electron microscopy (TEM).

RESULTS

Slit lamp examination before and after exposure of rabbits' corneas to the sensor confirmed safety of the device. SEM examination revealed no difference of the corneal epithelium which exposed to the new device with normal corneas. SEM and TEM pictures revealed damaged microvilli and tight junctions after instillation of 0.02% BAC. TER change after treatment with 0.02%BAC was similar to those determined by the established anterior chamber method.

CONCLUSION

We succeeded to develop a less invasive device for corneal TER measurement in vivo in animals. This new device may be applicable in the future for clinical use in humans.

Ocular surface reconstruction using stem cell and tissue engineering

Most human sensory information is gained through eyesight, and integrity of the ocular surface, including cornea and conjunctiva, is known to be indispensable for good vision. It is believed that severe damage to corneal epithelial stem cells results in devastating ocular surface disease, and many researchers and scientists have tried to reconstruct the ocular surface using medical and surgical approaches. Ocular surface reconstruction via regenerative therapy is a newly developed medical field that promises to be the next generation of therapeutic modalities, based on the use of tissue-specific stem cells to generate biological substitutes and improve tissue functions. The accomplishment of these objectives depends on three key factors: stem cells, which have highly proliferative capacities and longevities; the substrates determining the environmental niche; and growth factors that support them appropriately. This manuscript describes the diligent development of ocular surface reconstruction using tissue engineering techniques, both past and present, and discusses and validates their future use for regenerative therapy in this field.

Ocular Surface as Barrier of Innate Immunity

Sight is one of the most important senses that human beings possess. The ocular system is a complex structure equipped with mechanisms that prevent or limit damage caused by physical, chemical, infectious and environmental factors. These mechanisms include a series of anatomical, cellular and humoral factors that have been a matter of study. The cornea is not only the most powerful and important lens of the optical system, but also, it has been involved in many other physiological and pathological processes apart from its refractive nature; the morphological and histological properties of the cornea have been thoroughly studied for the last fifty years; drawing attention in its molecular characteristics of immune response. This paper will review the anatomical and physiological aspects of the cornea, conjunctiva and lacrimal apparatus, as well as the innate immunity at the ocular surface.

TLR3/TRIF signalling pathway regulates IL-32 and IFN-β secretion through activation of RIP-1 and TRAF in the human cornea

Toll-like receptor-3 (TLR3) and RNA helicase retinoic-acid-inducible protein-1 (RIG-I) serve as cytoplasmic sensors for viral RNA components. In this study, we investigated how the TLR3 and RIG-I signalling pathway was stimulated by viral infection to produce interleukin (IL)-32-mediated pro-inflammatory cytokines and type I interferon in the corneal epithelium using Epstein-Barr virus (EBV)-infected human cornea epithelial cells (HCECs/EBV) as a model of viral keratitis. Increased TLR3 and RIG-I that are responded to EBV-encoded RNA 1 and 2 (EBER1 and EBER2) induced the secretion of IL-32-mediated pro-inflammatory cytokines and IFN-β through up-regulation of TRIF/TRAF family proteins or RIP-1. TRIF silencing or TLR3 inhibitors more efficiently inhibited sequential phosphorylation of TAK1, TBK1, NF-κB and IRFs to produce pro-inflammatory cytokines and IFN-β than RIG-I-siRNA transfection in HCECs/EBV. Blockade of RIP-1, which connects the TLR3 and RIG-I pathways, significantly blocked the TLR3/TRIF-mediated and RIG-I-mediated pro-inflammatory cytokines and IFN-β production in HCECs/EBV. These findings demonstrate that TLR3/TRIF-dependent signalling pathway against viral RNA might be a main target to control inflammation and anti-viral responses in the ocular surface.

Nanomedicine approaches for corneal diseases

Corneal diseases are the third leading cause of blindness globally. Topical nonsteroidal anti-inflammatory drugs (NSAIDs), steroids, antibiotics and tissue transplantation are currently used to treat corneal pathological conditions. However, barrier properties of the ocular surface necessitate high concentration of the drugs applied in the eye repeatedly. This often results in poor efficacy and several side-effects. Nanoparticle-based molecular medicine seeks to overcome these limitations by enhancing the permeability and pharmacological properties of the drugs. The promise of nanomedicine approaches for treating corneal defects and restoring vision without side effects in preclinical animal studies has been demonstrated. Numerous polymeric, metallic and hybrid nanoparticles capable of transporting genes into desired corneal cells to intercept pathologic pathways and processes leading to blindness have been identified. This review provides an overview of corneal diseases, nanovector properties and their applications in drug-delivery and corneal disease management.

Ex vivo human corneal epithelial cell expansion from a xeno-feeder-free system

PURPOSE

The purpose of this study was to establish a simple, xeno-feeder-free method for cultivating human corneal epithelial cells.

METHODS

Limbal tissue explants from a cadaver were cultured in Iscove's modified Dulbecco's medium and low-calcium Panserin 801 medium in a 1:1 ratio. The outgrowing cells were characterized by flow cytometry, immunohistochemistry and real-time PCR (rtPCR). Limbal epithelial cells were expanded in a xeno-feeder-free, low-calcium medium and airlifted for 2 weeks each.

RESULTS

Migration of fibroblast-like stromal cells initially occurred from the limbal explants, and then epithelial cells migrated and grew on the stromal cells as an autofeeder layer. After airlifting, the cultured epithelium consisted of two to three layers. The cultured cells expressed stem cell-associated markers (ABCG2 and ΔNp63), differentiation markers (CK3 and CK12) and extracellular matrix-associated markers (lumican and decorin). rtPCR showed increased expression of markers for epithelial progenitor cells compared to fresh limbal tissue. Side population cells comprised 0.43 ± 0.04% of the cells (n = 5) in the primary culture. Flow cytometry showed that 49.12, 40.44 and 44.55% of the cells from the explants expressed E-cadherin, ΔNp63 and ABCG2, respectively.

CONCLUSION

This explant culture system using stromal cells as an autofeeder layer was useful in expanding human corneal epithelial cells. This system may offer clinical insight for the expansion of limbal progenitor cells for the reconstruction of the ocular surface.

Rocking media over ex vivo corneas improves this model and allows the study of the effect of proinflammatory cytokines on wound healing

PURPOSE

The aim of this work was to develop an in vitro cornea model to study the effect of proinflammatory cytokines on wound healing.

METHODS

Initial studies investigated how to maintain the ex vivo models for up to 4 weeks without loss of epithelium. To study the effect of cytokines, corneas were cultured with the interleukins IL-17A, IL-22, or a combination of IL-17A and IL-22, or lipopolysaccharide (LPS). The effect of IL-17A on wound healing was then examined.

RESULTS

With static culture conditions, organ cultures deteriorated within 2 weeks. With gentle rocking of media over the corneas and carbon dioxide perfusion, the ex vivo models survived for up to 4 weeks without loss of epithelium. The cytokine that caused the most damage to the cornea was IL-17A. Under static conditions, wound healing of the central corneal epithelium occurred within 9 days, but only a single-layered epithelium formed whether the cornea was exposed to IL-17A or not. With rocking of media gently over the corneas, a multilayered epithelium was achieved 9 days after wounding. In the presence of IL-17A, however, there was no wound healing evident. Characterization of the cells showed that wherever epithelium was present, both differentiated cells and highly proliferative cells were present.

CONCLUSIONS

We propose that introducing rocking to extend the effective working life of this model and the introduction of IL-17A to this model to induce aspects of inflammation extend its usefulness to study the effects of agents that influence corneal regeneration under normal and inflamed conditions.

Peptide therapies for ocular surface disturbances based on fibronectin-integrin interactions

The condition of the corneal epithelium is a critical determinant of corneal transparency and clear vision. The corneal epithelium serves as a barrier to protect the eye from external insults, with its smooth surface being essential for its optical properties. Disorders of the corneal epithelium include superficial punctate keratopathy, corneal erosion, and persistent epithelial defects (PEDs). The prompt resolution of these disorders is important for minimization of further damage to the cornea. Currently available treatment modalities for corneal epithelial disorders are based on protection of the ocular surface in order to allow natural healing to proceed. PEDs remain among the most difficult corneal conditions to treat, however. On the basis of characterization of the pathobiology of PEDs at the cell and molecular biological levels, we have strived to develop new modes of treatment for these defects. These treatments rely on two key concepts: provision of a substrate, such as the adhesive glycoprotein fibronectin, for the attachment and migration of corneal epithelial cells, and activation of these cells by biological agents such as the combination of substance P and insulin-like growth factor-1 (IGF-1). Central to both approaches is the role of the fibronectin-integrin system in corneal epithelial wound healing. Determination of the minimum amino acid sequences required for the promotion of corneal epithelial wound closure by fibronectin (PHSRN) and by substance P (FGLM-amide) plus IGF-1 (SSSR) has led to the development of peptide eyedrops for the treatment of PEDs that are free of adverse effects of the parent molecules.

Ocular surface reconstruction with a tissue-engineered nasal mucosal epithelial cell sheet for the treatment of severe ocular surface diseases

Severe ocular surface diseases (OSDs) with severe dry eye can be devastating and are currently some of the most challenging eye disorders to treat. To investigate the feasibility of using an autologous tissue-engineered cultivated nasal mucosal epithelial cell sheet (CNMES) for ocular surface reconstruction, we developed a novel technique for the culture of nasal mucosal epithelial cells expanded ex vivo from biopsy-derived human nasal mucosal tissues. After the protocol, the CNMESs had 4-5 layers of stratified, well-differentiated cells, and we successfully generated cultured epithelial sheets, including numerous goblet cells. Immunohistochemistry confirmed the presence of keratins 3, 4, and 13; mucins 1, 16, and 5AC; cell junction and basement membrane assembly proteins; and stem/progenitor cell marker p75 in the CNMESs. We then transplanted the CNMESs onto the ocular surfaces of rabbits and confirmed the survival of this tissue, including the goblet cells, up to 2 weeks. The present report describes an attempt to overcome the problems of treating severe OSDs with the most severe dry eye by treating them using tissue-engineered CNMESs to supply functional goblet cells and to stabilize and reconstruct the ocular surface. The present study is a first step toward assessing the use of tissue-engineered goblet-cell transplantation of nonocular surface origin for ocular surface reconstruction.

Vocal fold epithelial barrier in health and injury: a research review

PURPOSE

Vocal fold epithelium is composed of layers of individual epithelial cells joined by junctional complexes constituting a unique interface with the external environment. This barrier provides structural stability to the vocal folds and protects underlying connective tissue from injury while being nearly continuously exposed to potentially hazardous insults, including environmental or systemic-based irritants such as pollutants and reflux, surgical procedures, and vibratory trauma. Small disruptions in the epithelial barrier may have a large impact on susceptibility to injury and overall vocal health. The purpose of this article is to provide a broad-based review of current knowledge of the vocal fold epithelial barrier.

METHOD

A comprehensive review of the literature was conducted. Details of the structure of the vocal fold epithelial barrier are presented and evaluated in the context of function in injury and pathology. The importance of the epithelial-associated vocal fold mucus barrier is also introduced.

RESULTS/CONCLUSIONS

Information presented in this review is valuable for clinicians and researchers as it highlights the importance of this understudied portion of the vocal folds to overall vocal health and disease. Prevention and treatment of injury to the epithelial barrier is a significant area awaiting further investigation.

Combination of microstereolithography and electrospinning to produce membranes equipped with niches for corneal regeneration

Corneal problems affect millions of people worldwide reducing their quality of life significantly. Corneal disease can be caused by illnesses such as Aniridia or Steven Johnson Syndrome as well as by external factors such as chemical burns or radiation. Current treatments are (i) the use of corneal grafts and (ii) the use of stem cell expanded in the laboratory and delivered on carriers (e.g., amniotic membrane); these treatments are relatively successful but unfortunately they can fail after 3-5 years. There is a need to design and manufacture new corneal biomaterial devices able to mimic in detail the physiological environment where stem cells reside in the cornea. Limbal stem cells are located in the limbus (circular area between cornea and sclera) in specific niches known as the Palisades of Vogt. In this work we have developed a new platform technology which combines two cutting-edge manufacturing techniques (microstereolithography and electrospinning) for the fabrication of corneal membranes that mimic to a certain extent the limbus. Our membranes contain artificial micropockets which aim to provide cells with protection as the Palisades of Vogt do in the eye.

Cultivated oral mucosal epithelial transplantation for persistent epithelial defect in severe ocular surface diseases with acute inflammatory activity

Purpose

To assess the clinical efficacy of cultivated oral mucosal epithelial transplantation (COMET) for the treatment of persistent epithelial defect (PED).

Methods

We treated 10 eyes of nine patients with PED (Stevens–Johnson syndrome: three eyes; thermal/chemical injury: five eyes; ocular cicatricial pemphigoid: two eyes) with COMET at Kyoto Prefectural University of Medicine, Kyoto, Japan from 2002 to 2008.

Results

Preoperatively, PED existed on over more than 50% of the corneal surface in seven eyes. Severe ocular surface inflammation with fibrovascular tissue surrounded the PED in all 10 eyes. At 24-weeks postoperative, PED had improved in all cases except 1 in which the patient was unable to return to the hospital (95% CI, 55.5–99.7; Wilcoxon signed-rank test, p = 0.0078). The preoperative median of logarithmic minimum angle of resolution was 1.85 (range 0.15–2.70), and 1.85, 1.85, and 1.52 at the 4th, 12th, and 24th postoperative week, respectively. The mean total preoperative ocular surface grading score was 7.0 (range 4–17). At 4 and 12 weeks postoperative, the total ocular surface grading score had improved significantly (p = 0.0020, p = 0.0078), and at 24 weeks postoperative, it was 3.0 (range 2–12, p = 0.0234). During the follow-up period (median 23.3 months, range 5.6–39.7 months), no recurrence of PED was observed in any eye, and long-term ocular surface stability was obtained.

Conclusion

COMET enabled complete epithelialization of PED and stabilization of the ocular surface in patients with severe ocular surface disease, thus preventing end-stage cicatrization and vision loss at a later stage.

New trends in quantitative assessment of the corneal barrier function

The cornea is a very particular tissue due to its transparency and its barrier function as it has to resist against the daily insults of the external environment. In addition, maintenance of this barrier function is of crucial importance to ensure a correct corneal homeostasis. Here, the corneal epithelial permeability has been assessed in vivo by means of non-invasive tetrapolar impedance measurements, taking advantage of the huge impact of the ion fluxes in the passive electrical properties of living tissues. This has been possible by using a flexible sensor based in SU-8 photoresist. In this work, a further analysis focused on the validation of the presented sensor is performed by monitoring the healing process of corneas that were previously wounded. The obtained impedance measurements have been compared with the damaged area observed in corneal fluorescein staining images. The successful results confirm the feasibility of this novel method, as it represents a more sensitive in vivo and non-invasive test to assess low alterations of the epithelial permeability. Then, it could be used as an excellent complement to the fluorescein staining image evaluation.

Corneal alterations induced by topical application of commercial latanoprost, travoprost and bimatoprost in rabbit

Prostaglandin (PG) analogs, including latanoprost, travoprost, and bimatoprost, are currently the most commonly used topical ocular hypotensive medications. The purpose of this study was to investigate the corneal alterations in rabbits following exposure to commercial solution of latanoprost, travoprost and bimatoprost. A total of 64 New Zealand albino rabbits were used and four groups of treatments were constituted. Commercial latanoprost, travoprost, bimatoprost or 0.02% benzalkonium chloride (BAK) was applied once daily to one eye each of rabbits for 30 days. The contralateral untreated eyes used as controls. Schirmer test, tear break-up time (BUT), rose Bengal and fluorescein staining were performed on days 5, 10, 20, and 30. Central corneal changes were analyzed by in vivo confocal microscopy, and the corneal barrier function was evaluated by measurement of corneal transepithelial electrical resistance on day 5. Whole mount corneas were analyzed by using fluorescence confocal microscopy for the presence of tight-junction (ZO-1, occludin) and adherens-junction (E-cadherin, β-catenin) proteins, actin cytoskeleton, proliferative marker Ki67 and cell apoptosis in the epithelium. Topical application of commercial PG analogs resulted in significant corneal epithelial and stromal defects while no significant changes in aqueous tear production, BUT, rose bengal and fluorescein staining scores on day 5. Commercial PG analogs induced dislocation of ZO-1 and occludin from their normal locus, disorganization of cortical actin cytoskeleton at the superficial layer, and disruption of epithelial barrier function. The eyes treated with 0.02% BAK and latanoprost exhibited significantly reduced Schirmer scores, BUT, and increased fluorescein staining scores on days 10 and 30, respectively. Topical application of commercial PG analogs can quickly impair the corneal epithelium and stroma without tear deficiency. Commercial PG analogs break down the barrier integrity of corneal epithelium, concomitant with the disruption of cell junction and actin cytoskeleton between superficial cells in the corneal epithelium in vivo.

Three-year outcomes of cultured limbal epithelial allografts in aniridia and Stevens-Johnson syndrome evaluated using the Clinical Outcome Assessment in Surgical Trials assessment tool

Limbal stem cell deficiency (LSCD) is an eye disorder in which the stem cells responsible for forming the surface skin of the cornea are destroyed by disease. This results in pain, loss of vision, and a cosmetically unpleasant appearance. Many new treatments, including stem cell therapies, are emerging for the treatment of this condition, but assessment of these new technologies is severely hampered by the lack of biomarkers for this disease or validated tools for assessing its severity. The aims of this study were to design and test the reliability of a tool for grading LSCD, to define a set of core outcome measures for use in evaluating treatments for this condition, and to demonstrate their utility. This was achieved by using our defined outcome set (which included the Clinical Outcome Assessment in Surgical Trials of Limbal stem cell deficiency [COASTL] tool) to evaluate the 3-year outcomes for allogeneic ex vivo cultivated limbal epithelial transplantation (allo-CLET) in patients who had bilateral total LSCD secondary to aniridia or Stevens-Johnson syndrome. The results demonstrate that our new grading tool for LSCD, the COASTL tool, is reliable and repeatable, and that improvements in the biomarkers used in this tool correlate positively with improvements in visual acuity. The COASTL tool showed that following allo-CLET there was a decrease in LSCD severity and an increase in visual acuity up to 12 months post-treatment, but thereafter LSCD severity and visual acuity progressively deteriorated.

Chitosan nanoparticles for daptomycin delivery in ocular treatment of bacterial endophthalmitis

CONTEXT

Chitosan nanoparticles were prepared to encapsulate daptomycin and proposed as a delivery system of this antibiotic to the eye for the treatment of bacterial endophthalmitis.

OBJECTIVE

The aim of this study was to develop daptomycin-loaded nanoparticles to apply directly to the eye, as a possible non-invasive and less painful alternative for the treatment of endophthalmitis, increasing the effectiveness of treatment and reducing toxicity associated with systemic administration.

MATERIALS AND METHODS

Nanoparticles were obtained by ionotropic gelation between chitosan and sodium tripolyphosphate (TPP). Physicochemical and morphological characteristics of nanoparticles were evaluated, as well as determination of antimicrobial efficiency of encapsulated daptomycin and stability of the nanoparticles in the presence of lysozyme and mucin.

RESULTS

Loaded nanoparticles presented mean particle sizes around 200 nm, low polydispersity index, and positive zeta potential. Morphological examination by scanning electron microscopy (SEM) confirmed their small size and round-shaped structure. Encapsulation efficiency ranged from 80 to 97%. Total in vitro release of daptomycin was obtained within 4 h. Determination of minimum inhibitory concentrations (MICs) showed that bacteria were still susceptible to daptomycin encapsulated into the nanoparticles. Incubation with lysozyme did not significantly affect the integrity of the nanoparticles, although mucin positively affected their mucoadhesive properties.

DISCUSSION AND CONCLUSION

The obtained nanoparticles have suitable characteristics for ocular applications, arising as a promising solution for the topical administration of daptomycin to the eye.

Tear cytokine response to multipurpose solutions for contact lenses

PURPOSE

An increased risk of corneal infiltrative events has been noted with the use of certain contact lenses and multipurpose solutions (MPS). This study was designed to evaluate tear cytokine assay as a sensitive, objective, and quantitative measure of the ocular surface response to contact lens/MPS and to consider the assay's clinical relevance in the context of other measures of ocular surface response.

METHODS

Two MPS, ReNu® Fresh™ (RNF) and Opti-Free® RepleniSH (OFR), were used with daily wear silicone hydrogel contact lenses in a randomized, prospective crossover study involving 26 subjects. Clinical data collection (conjunctival hyperemia, ocular surface sensitivity, solution induced corneal staining (SICS) test score, and subjective responses) and tear cytokine assays were conducted masked. Responses were tracked as change from baseline throughout the experimental schedule.

RESULTS

SIMILAR RESPONSE PATTERNS FOR SEVERAL INFLAMMATORY CYTOKINES WERE SEEN THROUGHOUT BOTH PHASES: subjects who received OFR in Phase I had mean tear concentrations that were generally higher than those of the RNF Phase I group. OFR Phase I subjects had significant (P < 0.01) increases over baseline at day 1 and/or following washout for 13 cytokines (cc chemokine ligands [CCL] 3, CCL5, CCL11, granulocyte-macrophage colony-stimulating factor [GM-CSF], interferon [INF]-γ, interleukin [IL]-2, IL-4, IL-5, IL-6, IL-13, IL-15, IL-17, tumor necrosis factor [TNF]-α). These changes were not observed in RNF Phase I subjects, even though SICS test scores increased. Phase I OFR subjects also had increased dryness, while RNF Phase I subjects had decreased bulbar hyperemia. No changes were detected with respect to limbal hyperemia or surface sensitivity thresholds.

CONCLUSION

The tear cytokine assay can detect and differentiate contact lens/MPS induced increases in inflammatory cytokines. Changes in cytokine levels were consistent with measurement of hyperemia and dryness but not with SICS scores, thereby suggesting a proinflammatory response to OFR compared to RNF that is not related to SICS test score. Tear cytokine profiles may be useful for reconciling clinical relevance of test results and in revealing signaling involved in the development of corneal infiltrative events.

Corneal endothelial regeneration and tissue engineering

Human corneal endothelial cells (HCECs) have a limited proliferative capacity. Descemet stripping with automated endothelial keratoplasty (DSAEK) has become the preferred method for the treatment of corneal endothelial deficiency, but it requires a donor cornea. To overcome the shortage of donor corneas, transplantation of cultured HCEC sheets has been attempted in experimental studies. This review summarizes current knowledge about the mechanisms of corneal endothelial wound healing and about tissue engineering for the corneal endothelium. We also discuss recent work on tissue engineering for DSAEK grafts using cultured HCECs and HCEC precursor cell isolation method (the sphere-forming assay). DSAEK grafts (HCEC sheets) were constructed by seeding cultured HCECs on human amniotic membrane, thin human corneal stroma, and collagen sheets. The pump function of the HCEC sheets thus obtained was approximately 75%-95% of that for human donor corneas. HCEC sheets were transplanted onto rabbit corneas after DSAEK. While the untransplanted control group displayed severe stromal edema, the transplanted group had clear corneas throughout the observation period. The sphere-forming assay using donor human corneal endothelium or cultured HCECs can achieved mass production of human corneal endothelial precursors. These findings indicate that cultured HCECs transplanted after DSAEK can perform effective corneal dehydration in vivo and suggest the feasibility of employing the transplantation of cultured HCECs to treat endothelial dysfunction. Additionally, corneal endothelial precursors may be an effective strategy for corneal endothelial regeneration.

Visual improvement after cultivated oral mucosal epithelial transplantation

PURPOSE

To report the effectiveness, disease-specific outcomes, and safety of cultivated oral mucosal epithelial sheet transplantation (COMET), with the primary objective of visual improvement.

DESIGN

Noncomparative, retrospective, interventional case series.

PARTICIPANTS

This study involved 46 eyes in 40 patients with complete limbal stem cell deficiency (LSCD) who underwent COMET for visual improvement. These LSCD disorders fell into the following 4 categories: Stevens-Johnson syndrome (SJS; 21 eyes), ocular cicatricial pemphigoid (OCP; 10 eyes), thermal or chemical injury (7 eyes), or other diseases (8 eyes).

METHODS

Best-corrected visual acuity (BCVA) and ocular surface grading score were examined before surgery; at the 4th, 12th, and 24th postoperative week; and at the last follow-up. Data on COMET-related adverse events and postoperative management were collected. The outcomes in each disease category were evaluated separately.

MAIN OUTCOME MEASURES

The primary outcome was the change in median logarithm of the minimum angle of resolution (logMAR) BCVA at the 24th postoperative week. The secondary outcome was the ocular surface grading score.

RESULTS

Median logMAR BCVA at baseline was 2.40 (range, 1.10 to 3.00). In SJS, logMAR BCVA improved significantly during the 24 weeks after surgery. In contrast, the BCVA in OCP was improved significantly only at the 4th postoperative week. In 6 of the 7 thermal or chemical injury cases, logMAR BCVA improved after planned penetrating keratoplasty or deep lamellar keratoplasty. Grading scores of ocular surface abnormalities improved in all categories. Of 31 patients with vision loss (logMAR BCVA, >2) at baseline, COMET produced improvement (logMAR BCVA, ≤2) in 15 patients (48%). Visual improvement was maintained with long-term follow-up (median, 28.7 months). Multivariate stepwise logistic regression analysis showed that corneal neovascularization and symblepharon were correlated significantly with logMAR BCVA improvement at the 24th postoperative week (P=0.0023 and P=0.0173, respectively). Although postoperative persistent epithelial defects and slight to moderate corneal infection occurred in the eyes of 16 and 2 patients, respectively, all were treated successfully with no eye perforation.

CONCLUSIONS

Long-term visual improvement was achievable in cases of complete LSCD. Cultivated oral mucosal epithelial sheet transplantation offered substantial visual improvement even for patients with end-stage severe ocular surface disorders accompanying severe tear deficiency. Patients with corneal blindness such as SJS benefited from critical improvement of visual acuity.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in anymaterials discussed in this article.

Generation of corneal epithelial cells from induced pluripotent stem cells derived from human dermal fibroblast and corneal limbal epithelium

Induced pluripotent stem (iPS) cells can be established from somatic cells. However, there is currently no established strategy to generate corneal epithelial cells from iPS cells. In this study, we investigated whether corneal epithelial cells could be differentiated from iPS cells. We tested 2 distinct sources: human adult dermal fibroblast (HDF)-derived iPS cells (253G1) and human adult corneal limbal epithelial cells (HLEC)-derived iPS cells (L1B41). We first established iPS cells from HLEC by introducing the Yamanaka 4 factors. Corneal epithelial cells were successfully induced from the iPS cells by the stromal cell-derived inducing activity (SDIA) differentiation method, as Pax6(+)/K12(+) corneal epithelial colonies were observed after prolonged differentiation culture (12 weeks or later) in both the L1B41 and 253G1 iPS cells following retinal pigment epithelial and lens cell induction. Interestingly, the corneal epithelial differentiation efficiency was higher in L1B41 than in 253G1. DNA methylation analysis revealed that a small proportion of differentially methylated regions still existed between L1B41 and 253G1 iPS cells even though no significant difference in methylation status was detected in the specific corneal epithelium-related genes such as K12, K3, and Pax6. The present study is the first to demonstrate a strategy for corneal epithelial cell differentiation from human iPS cells, and further suggests that the epigenomic status is associated with the propensity of iPS cells to differentiate into corneal epithelial cells.