Pax6 downregulation mediates abnormal lineage commitment of the ocular surface epithelium in aqueous-deficient dry eye disease

Keratinizing squamous metaplasia (SQM) of the ocular surface is a blinding consequence of systemic autoimmune disease and there is no cure. Ocular SQM is traditionally viewed as an adaptive tissue response during chronic keratoconjunctivitis sicca (KCS) that provokes pathological keratinization of the corneal epithelium and fibrosis of the corneal stroma. Recently, we established the autoimmune regulator-knockout (Aire KO) mouse as a model of autoimmune KCS and identified an essential role for autoreactive CD4+ T cells in SQM pathogenesis. In subsequent studies, we noted the down-regulation of paired box gene 6 (Pax6) in both human patients with chronic KCS associated with Sjögren’s syndrome and Aire KO mice. Pax6 encodes a pleiotropic transcription factor guiding eye morphogenesis during development. While the postnatal function of Pax6 is largely unknown, we hypothesized that its role in maintaining ocular surface homeostasis was disrupted in the inflamed eye and that loss of Pax6 played a functional role in the initiation and progression of SQM. Adoptive transfer of autoreactive T cells from Aire KO mice to immunodeficient recipients confirmed CD4+ T cells as the principal downstream effectors promoting Pax6 downregulation in Aire KO mice. CD4+ T cells required local signaling via Interleukin-1 receptor (IL-1R1) to provoke Pax6 loss, which prompted a switch from corneal-specific cytokeratin, CK12, to epidermal-specific CK10. The functional role of Pax6 loss in SQM pathogenesis was indicated by the reversal of SQM and restoration of ocular surface homeostasis following forced expression of Pax6 in corneal epithelial cells using adenovirus. Thus, tissue-restricted restoration of Pax6 prevented aberrant epidermal-lineage commitment suggesting adjuvant Pax6 gene therapy may represent a novel therapeutic approach to prevent SQM in patients with chronic inflammatory diseases of the ocular surface.

Epilepsy characteristics and psychosocial factors associated with ketogenic diet success

The ketogenic diet is an effective therapy for childhood epilepsy, but its important impacts on families could affect successful treatment. We assessed medical and psychosocial factors associated with successful ketogenic diet treatment. A total of 23 families of patients treated with ketogenic diet completed questionnaires (30% response), including inquiries about challenges to successful dietary treatments and validated family functioning scales. Of these, 14 were considered successful (diet discontinued once the child was seizure-free or continued as clinically indicated). Family-identified challenges were food preparation time (n = 11) and that the diet was too restrictive (n = 9). Neither Medicaid insurance nor family functioning scale scores were significantly associated with successful treatment. Lower seizure frequency prior to ketogenic diet initiation (P = .02) and postdiet seizure improvement (P = .01) were associated with increased odds of success. Effective ketogenic diet treatment is dictated both by psychosocial and epilepsy-related influences. A focus on understanding the psychosocial issues may help to improve families' experiences and success with the ketogenic diet.

Rac1 and Cdc42 differentially modulate cigarette smoke-induced airway cell migration through p120-catenin-dependent and -independent pathways

The adherens junction protein p120-catenin (p120ctn) shuttles between E-cadherin-bound and cytoplasmic pools to regulate E-cadherin/catenin complex stability and cell migration, respectively. When released from the adherens junction, p120ctn promotes cell migration through modulation of the Rho GTPases Rac1, Cdc42, and RhoA. Accordingly, the down-regulation and cytoplasmic mislocalization of p120ctn has been reported in all subtypes of lung cancers and is associated with grave prognosis. Previously, we reported that cigarette smoke induced cytoplasmic translocation of p120ctn and cell migration, but the underlying mechanism was unclear. Using primary human bronchial epithelial cells exposed to smoke-concentrated medium (Smk), we observed the translocation of Rac1 and Cdc42, but not RhoA, to the leading edge of polarized and migrating human bronchial epithelial cells. Rac1 and Cdc42 were robustly activated by smoke, whereas RhoA was inhibited. Accordingly, siRNA knockdown of Rac1 or Cdc42 completely abolished Smk-induced cell migration, whereas knockdown of RhoA had no effect. p120ctn/Rac1 double knockdown completely abolished Smk-induced cell migration, whereas p120ctn/Cdc42 double knockdown did not. These data suggested that Rac1 and Cdc42 coactivation was essential to smoke-promoted cell migration in the presence of p120ctn, whereas migration proceeded via Rac1 alone in the absence of p120ctn. Thus, Rac1 may provide an omnipotent therapeutic target in reversing cell migration during the early (intact p120ctn) and late (loss of p120ctn) stages of lung carcinogenesis.

Cigarette smoke disrupts the integrity of airway adherens junctions through the aberrant interaction of p120-catenin with the cytoplasmic tail of MUC1

Adherens junctions (AJs) containing epithelial cadherin (E-cad) bound to p120-catenin (p120ctn) and β-catenin (β-ctn) play a crucial role in regulating cell-cell adhesion. Cigarette smoke abrogates cell-cell adhesion between epithelial cells by disrupting E-cad, a hallmark of epithelial-mesenchymal transition (EMT), yet the underlying mechanism remains unknown. We used an organotypic culture of primary human bronchial epithelial (HBE) cells treated with smoke-concentrated medium (Smk) to establish an essential role for the interaction between p120ctn and the cytoplasmic tail of MUC1 (MUC1-CT) in regulating E-cad disruption. Within the first 4 h of smoke exposure, apical MUC1-CT repositioned to the basolateral membrane of pseudo-stratified HBE cells, where it interacted with p120ctn. A time-dependent increase in MUC1-CT/p120ctn complexes occurred in conjunction with a time-dependent dissociation of p120ctn/E-cad/β-ctn complexes, as well as the coordinated degradation of p120ctn and E-cad. Interestingly, Smk induced a similar interaction between MUC1-CT and β-ctn, but this occurred 44 h after MUC1-CT's initial interaction with p120ctn, and well after the AJs were destroyed. Blocking MUC1-CT's interaction with p120ctn using a MUC1-CT dominant-negative peptide, PMIP, successfully abolished Smk's disruptive effects on AJs and recovered apical-basolateral polarity of HBE cells. The MUC1-CT/p120ctn interaction was highly dependent on EGFR/Src/Jnk-mediated tyrosine phosphorylation (TyrP) of MUC1-CT. Accordingly, EGFR, Src or Jnk inhibitors (AG1478, PP2, SP600125, respectively) abrogated Smk-induced MUC1-CT-TyrP, MUC1-CT/p120ctn interaction, AJ disruption, and loss of cellular polarity. Our work identified MUC1-CT and p120ctn as important regulators of epithelial polarity and cell-cell adhesion during a smoke-induced EMT-like process. Novel therapeutics designed to inhibit MUC1-CT/p120ctn complex formation may prevent EMT in the smoker's airway.

Critical involvement of macrophage infiltration in the development of Sjögren's syndrome-associated dry eye

Lymphocytic infiltration of the lacrimal gland and ocular surface in autoimmune diseases such as Sjögren's syndrome (SS) causes an aqueous-deficient dry eye that is associated with significant morbidity. Previous studies from our laboratory and others have established autoimmune regulator (Aire)-deficient mice as a useful model to examine exocrinopathy and ocular surface disease associated with SS. Consistent with human SS, autoreactive CD4(+) T cells play an indispensible role in the development of exocrine and ocular surface disease in Aire knockout mice. We report that in addition to CD4(+) T cells, a large number of macrophages infiltrate the corneal stroma, limbus, and lacrimal glands of diseased mice. Adoptive transfer of autoreactive CD4(+) T cells from Aire knockout mice led to local infiltration of macrophages and ocular surface damage in immunodeficient recipients. Depletion of local macrophages, through subconjunctival injection of clodronate liposome, attenuated lissamine green staining and improved ocular phenotype. Alternatively, systemic depletion of macrophages had no effect on ocular phenotype but led to significant improvements in lacrimal gland exocrinopathy and tear secretion. Our results suggested that autoreactive CD4(+) T cells provoked macrophage infiltration to the eye and lacrimal gland, where they played a functional role in directing the development of autoimmune dry eye.

Interleukin-1 receptor mediates the interplay between CD4+ T cells and ocular resident cells to promote keratinizing squamous metaplasia in Sjögren's syndrome

Keratinizing squamous metaplasia (SQM) of the ocular mucosal epithelium is a blinding corneal disease characterized by the loss of conjunctival goblet cells (GCs), pathological ocular surface keratinization and tissue recruitment of immune cells. Using the autoimmune regulator (Aire)-deficient mouse as a model for Sjögren's syndrome (SS)-associated SQM, we identified CD4(+) T lymphocytes as the main immune effectors driving SQM and uncovered a pathogenic role for interleukin-1 (IL-1). IL-1, a pleiotropic cytokine family enriched in ocular epithelia, governs tissue homeostasis and mucosal immunity. Here, we used adoptive transfer of autoreactive CD4(+) T cells to dissect the mechanism whereby IL-1 promotes SQM. CD4(+) T cells adoptively transferred from both Aire knockout (KO) and Aire/IL-1 receptor type 1 (IL-1R1) double KO donors conferred SQM to severe-combined immunodeficiency (scid) recipients with functional IL-1R1, but not scid recipients lacking IL-1R1. In the lacrimal gland, IL-1R1 was primarily immunolocalized to ductal epithelium surrounded by CD4(+) T cells. In the eye, IL-1R1 was expressed on local mucosal epithelial and stromal cells, but not on resident antigen-presenting cells or infiltrating immune cells. In both tissues, autoreactive CD4(+) T-cell infiltration was only observed in the presence of IL-1R1-postive resident cells. Moreover, persistent activation of IL-1R1 signaling led to chronic immune-mediated inflammation by retaining CD4(+) T cells in the local microenvironment. Following IL-1R1-dependent infiltration of CD4(+) T cells, we observed SQM hallmarks in local tissues-corneal keratinization, conjunctival GC mucin acidification and epithelial cell hyperplasia throughout the ocular surface mucosa. Proinflammatory IL-1 expression in ocular epithelial cells significantly correlated with reduced tear secretion, while CD4(+) T-cell infiltration of the lacrimal gland predicted the development of ocular SQM. Collectively, data in this study indicated a central role for IL-1 in orchestrating a functional interplay between immune cells and resident cells of SS-targeted tissues in the pathogenesis of SQM.

p120-catenin modulates airway epithelial cell migration induced by cigarette smoke

Cigarette smoking has been linked to almost all major types of cancer. Emerging evidence suggests that smoking initiates transformed cell growth and migration by disrupting cell-cell interactions in the polarized mucosal epithelium. Together with other adherens junction proteins, p120-catenin (p120ctn) maintains cell-cell adhesion through its direct interaction with E-cadherin (E-cad). Mislocalization and/or loss of p120ctn have been reported in all lung cancer subtypes and are related to poor prognosis. Here, we showed that p120ctn modulates smoke-induced cell migration via the EGFR/Src-P pathway. Chemical blockade of EGFR/Src signaling inhibited smoke-induced activation of cofilin (an actin severing protein) and promoted cell migration in the presence of p120ctn but had little effect on blocking migration in the absence of p120ctn. These data suggested that smoke-induced cell migration was mediated via an EGFR/Src-dependent signaling pathway in cells that expressed p120ctn, but upon loss of p120ctn, migration continued to occur via an alternative, EGFR/Src-independent pathway. Thus, gradual loss of membrane p120ctn with lung cancer progression may contribute to reduced effectiveness of conventional chemotherapies, such as those directed against EGFR.

Abstract B19: Cigarette smoke promotes human airway epithelial migration through temporal coordination of p120-catenin-dependent and -independent pathways

Background: Cigarette smoking has been linked to almost all major types of cancer. Emerging evidence suggests that smoking initiates transformed cell growth and migration by disrupting cell-cell interactions in the polarized mucosal epithelium. Together with other adherens junction proteins, p120-catenin (p120ctn) maintains cell-cell adhesion through its direct interaction with E-cadherin. Mislocalization and/or loss of p120ctn have been reported in all lung cancer subtypes and are related to poor prognosis. Our purpose was to investigate the initiating (intact p120ctn) and late (loss of 120ctn) events of smoke-promoted lung carcinogenesis using primary human bronchial epithelial (HBE) cells.

Methods: Wide-type and p120ctn-knockdown HBE cells exposed to cigarette smoke-conditioned medium were used to mimic the early and late progressive stages of lung cancer. Signaling cascades and cell migration under the two conditions were investigated.

Results: Src and Jnk activation by smoke were delayed in p120ctn-knockdown cells and inhibition of migration through the chemical blockade of EGFR, Src, and/or Jnk was dependent on p120ctn. In contrast, chemical inhibition of signaling via Akt (cell survival) or Erk (cell proliferation) was sufficient to block smoke-induced migration independent of p120ctn. Also independent of p120ctn was smoke's effect on the RhoGTPase, Rac1. Rac1 knockdown abolished dephosphorylation of actin binding protein, cofilin, in the presence and absence of p120ctn, indicating its essential role in smoke-induced cell migration.

Conclusions: These studies provide unprecedented insight regarding the multiple and interdependent molecular strategies employed by smoke to escape tightly regulated cellular processes such as cell migration, proliferation, and survival.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr B19.

Interleukin-1 as a phenotypic immunomodulator in keratinizing squamous metaplasia of the ocular surface in Sjögren's syndrome

Chronic inflammation of the ocular surface in Sjögren's syndrome (SS) is associated with a vision-threatening, phenotypic change of the ocular surface, which converts from a nonkeratinized, stratified squamous epithelium to a nonsecretory, keratinized epithelium. This pathological process is known as squamous metaplasia. Based on a significant correlation between ocular surface interleukin (IL)-1beta expression and squamous metaplasia in patients with SS, we investigated the role of IL-1 in the pathogenesis of squamous metaplasia in an animal model that mimics the clinical characteristics of SS. Using autoimmune-regulator (aire)-deficient mice, we assessed lacrimal gland and ocular surface immunopathology by quantifying the infiltration of major histocompatibility complex class II(+) (I-A(d+)) dendritic cells and CD4(+) T cells. We examined squamous metaplasia using a biomarker of keratinization, small proline-rich protein 1B. We used lissamine green staining as a readout for ocular surface epitheliopathy and Alcian blue/periodic acid-Schiff histochemical analysis to characterize goblet cell muco-glycoconjugates. Within 8 weeks, the eyes of aire-deficient mice were pathologically keratinized with significant epithelial damage and altered mucin glycosylation. Although knockdown of IL-1 receptor 1 did not attenuate lymphocytic infiltration of the lacrimal gland or eye, it significantly reduced ocular surface keratinization, epitheliopathy, and muco-glycoconjugate acidification. These data demonstrate a phenotypic modulation role for IL-1 in the pathogenesis of squamous metaplasia and suggest that IL-1 receptor 1-targeted therapies may be beneficial for treating ocular surface disease associated with SS.

A simplified quantitative method for assessing keratoconjunctivitis sicca from the Sjögren's Syndrome International Registry

PURPOSE

To describe, apply, and test a new ocular grading system for assessing keratoconjunctivitis sicca (KCS) using lissamine green and fluorescein.

DESIGN

Prospective, observational, multicenter cohort study.

METHODS

The National Institutes of Health-funded Sjögren's Syndrome International Registry (called Sjögren's International Collaborative Clinical Alliance [SICCA]) is developing standardized classification criteria for Sjögren syndrome (SS) and is creating a biospecimen bank for future research. Eight SICCA ophthalmologists developed a new quantitative ocular grading system (SICCA ocular staining score [OSS]), and we analyzed OSS distribution among the SICCA cohort and its association with other phenotypic characteristics of SS. The SICCA cohort includes participants ranging from possibly early SS to advanced disease. Procedures include sequenced unanesthetized Schirmer test, tear break-up time, ocular surface staining, and external eye examination at the slit lamp. Using statistical analyses and proportional Venn diagrams, we examined interrelationships between abnormal OSS (>or=3) and other characteristics of SS (labial salivary gland [LSG] biopsy with focal lymphocytic sialadenitis and focus score >1 positive anti-SS A antibodies, anti-SS B antibodies, or both).

RESULTS

Among 1208 participants, we found strong associations between abnormal OSS, positive serologic results, and positive LSG focus scores (P < .0001). Analysis of the overlapping relationships of these 3 measures defined a large group of participants who had KCS without other components of SS, representing a clinical entity distinct from the KCS associated with SS.

CONCLUSIONS

This new method for assessing KCS will become the means for diagnosing the ocular component of SS in future classification criteria. We find 2 forms of KCS whose causes may differ.

Molecular mechanism of proinflammatory cytokine-mediated squamous metaplasia in human corneal epithelial cells

PURPOSE

The cornified envelope protein small proline-rich protein 1B (SPRR1B) is a biomarker for squamous metaplasia. Proinflammatory cytokines IL-1beta and IFN-gamma are potent inducers of ocular surface keratinization and SPRR1B expression. Here the molecular mechanisms controlling SPRR1B gene expression in response to IL-1beta and IFN-gamma are elucidated.

METHODS

A 3-kb fragment of the SPRR1B gene 5'-flanking region was amplified from human chromosome 1, sequentially deleted, and cloned into a luciferase vector. Constructs were transiently transfected into human corneal epithelial cells, and activity was assessed in response to IL-1beta, IFN-gamma, or basal medium. Functional cis-elements responding to IL-1beta and IFN-gamma were characterized by site-directed mutagenesis and gel mobility shift assay. Effects of mitogen-activated protein kinases p38, ERK, and JNK were assessed using inhibitors and dominant-negative mutants. Results were validated by real-time RT-PCR.

RESULTS

The first 620 bp of the SPRR1B 5'-flanking region regulated constitutive expression and increased promoter activity in response to IL-1beta and IFN-gamma. Corresponding cis-elements for IL-1beta and IFN-gamma were bound by cAMP response element binding protein (CREB) and zinc-finger E-box binding homeobox 1 (ZEB1), respectively. Inhibition of p38 abolished the stimulatory effects of IL-1beta and IFN-gamma on SPRR1B, whereas inhibition of JNK and ERK had no effect. Dominant-negative mutants targeting p38alpha and p38beta2 blocked cytokine-induced SPRR1B promoter activity and mRNA expression.

CONCLUSIONS

SPRR1B is upregulated by the proinflammatory cytokines IL-1beta and IFN-gamma via p38 MAPK-mediated signaling pathways that lead to the activation of transcription factors CREB and ZEB1, respectively. These results identify key intracellular signaling intermediates involved in the pathogenesis of immune-mediated ocular surface squamous metaplasia.

Small proline-rich protein 1B (SPRR1B) is a biomarker for squamous metaplasia in dry eye disease

PURPOSE

Squamous metaplasia occurs in ocular surface diseases like Sjögren's syndrome (SS). It is a phenotypic change whereby epithelial cells initiate synthesis of squamous cell-specific proteins such as small proline-rich protein 1B (SPRR1B) that result in pathologic keratin formation on the ocular surface. The authors hypothesized that inflammation is a key inducer of pathologic keratinization and that SPRR1B represents an analytical biomarker for the study of the molecular mechanisms.

METHODS

Real-time quantitative RT-PCR and immunohistochemistry were used to examine SPRR1B mRNA and protein in two different mouse models of dry eye and patients with SS. Adoptive transfer of mature lymphocytes from mice lacking the autoimmune regulator (aire) gene was performed to examine the role of inflammation as an inducer of squamous metaplasia. SPRR1B expression in response to several cytokines was examined in vitro, whereas the expression of cytokines IL1beta and IFNgamma was quantified in ocular tissues of aire-deficient mice and patients with SS.

RESULTS

SPRR1B was increased across the ocular surface of mice with both desiccating stress and autoimmune-mediated, aqueous-deficient dry eye and in patients with SS. Adoptive transfer of CD4(+) T cells from aire-deficient mice to immunodeficient recipients caused advanced ocular surface keratinization. IL1alpha, IL1beta, IL6, IFNgamma, and TNFalpha induced SPRR1B expression in vitro and the local expression of IL1beta and IFNgamma was elevated in ocular tissues of patients with SS and aire-deficient mice.

CONCLUSIONS

SPRR1B is a valid biomarker for the study of the molecular mechanisms of squamous metaplasia. There is a definitive link between inflammation and squamous metaplasia in autoimmune-mediated dry eye disease, with IL1beta and IFNgamma likely acting as key participants.

Life at the front: dissecting bacterial-host interactions at the ocular surface

The ocular surface usually looks quiet, presenting a general impression of biological inactivity. Yet, the ability of the cornea to maintain health while continually exposed to environmental insults, and in the relative absence of immune strategies afforded by other body sites, reflects its complexity. Because it is critical for transparency and, therefore, our survival, the fine structure of the cornea has likely provided the driving force for the evolution of what appears to be a truly remarkable system. While several molecules are now known to participate, we are only beginning to obtain the knowledge to fully explain the mechanisms involved in corneal resistance to infection. Full explanation will require a better understanding of the interplay between microbes and various components of the ocular surface, and of the critical factors determining health as the usual outcome. To understand infectious disease, we need to consider how the scenario changes in conditions associated with susceptibility. What we learn in the process could yield a wealth of potential therapies for a wide variety of diseases of the eye and of other sites.

Exposure of human corneal epithelial cells to contact lenses in vitro suppresses the upregulation of human β-defensin-2 in response to antigens of Pseudomonas aeruginosa

Bacterial keratitis is a sight-threatening complication of contact lens wear, and Pseudomonas aeruginosa is a commonly isolated pathogen. The mechanisms by which lenses predispose the cornea to P. aeruginosa infection are unknown. Corneal epithelial cells express numerous innate defenses, some of which have bactericidal effects against P. aeruginosa. One of these is human beta-defensin-2 (hBD-2), which is upregulated in response to lipopolysaccharide or flagellin antigens. We hypothesized that prior exposure of corneal epithelia to a contact lens would interfere with upregulation of hBD-2 in response to P. aeruginosa. A novel in vitro model was used in which cultured human corneal epithelial cells were exposed to a hydrophilic contact lens for up to 3.5 days prior to challenge with a culture supernatant of P. aeruginosa antigens for 6h. Without prior lens exposure, the supernatant caused >2-fold upregulation of hBD-2 mRNA message and expression of hBD-2 peptide. Prior contact lens exposure blocked this upregulation without obvious effects on cell health. Western immunoblot and luciferase reporter studies showed that Pseudomonas-induced hBD-2 upregulation involved MyD88, c-Jun N-terminal kinase and both AP-1 and NF-kappaB transcription factors. Contact lenses did not affect surface expression of Toll-like receptor-2, -4 or -5, but did block antigen activation of AP-1, but not NF-kappaB, transcription factors. These data show that contact lenses can interfere with epithelial defense responses to bacterial antigens in vitro, and if translated in vivo, could help predispose the cornea to infection.

Interaction of Pseudomonas aeruginosa with human tear fluid components

PURPOSE

Reflex human tears bind Pseudomonas aeruginosa bacteria and prevent them from invading corneal epithelial cells. In this study, we assessed the effect of eye closure and the role of sialoglycoprotein (SG) in tears on bacterial binding and invasion.

METHODS

Human tears (reflex and closed-eye) were collected using a microcapillary tube. Reflex tears were separated into 13 fractions by high-performance liquid chromatography while high-molecular-weight components from closed-eye tears were separated into an SG/mucin fraction and a nonmucin fraction. Bacterial binding was quantified by viable counts and bacterial invasion was tested using the gentamicin survival technique.

RESULTS

Closed-eye tears bound significantly more bacteria than open-eye tears. Fractionation of reflex tears showed that 11 out of the 13 fractions bound bacteria, while all 13 fractions significantly reduced bacterial invasion of corneal epithelial cells. Surprisingly, the SG/mucin component of closed-eye tears resisted bacterial binding and had no significant effect on bacterial invasion.

CONCLUSIONS

P. aeruginosa bacteria bind more efficiently to closed-eye tears than to open-eye tears. The mechanism by which tears bind bacteria and protect against invasion does not require SG/mucin, as this fraction of closed-eye tears does not contain either activity.

Innate defense of the ocular surface

PURPOSE

The mucosal surface of the eye interfaces with the environment and can detect the presence of pathogens and irritants. The mucosal cells respond by up-regulating genes whose products either directly attack the contaminant or recruit leukocytes through the release of cytokines. Mucin, an epithelial glycoprotein, traps contaminants and aids in their removal through normal tear clearance mechanisms.

METHODS AND RESULTS

Using Northern analysis and reverse transcription-polymerase chain reaction, we have found that MUC1, a membrane-bound ocular surface mucin, is up-regulated following exposure to the products of both bacteria and activated lymphocytes. Consistent with this, MUC1 gene expression is also up-regulated in corneal epithelial cells exposed to precorneal tear film collected from two rigid contact lens wearers.

CONCLUSION

The changes in MUC1 gene expression during exposure to potential ocular irritants suggest that analysis of the molecular mechanisms mediating these changes may reveal control points amenable to drug therapy.

The Berkeley Contact Lens Extended Wear Study. Part I : Study design and conduct

OBJECTIVE

The primary aim of the Berkeley Contact Lens Extended Wear Study (CLEWS) was to test the hypotheses that extended wear of rigid gas-permeable (RGP) contact lenses with greater oxygen permeability (Dk) reduces the incidence of contact lens-associated keratopathy (CLAK) and increases the survival rate in RGP extended wear (EW). In this article we describe the clinical trial design in detail, present the results of subject recruitment and retention, and provide the baseline demographic and ocular characteristics of the CLEWS subjects, whose data will be analyzed to address the study aims in a companion article.

DESIGN

A randomized, concurrently controlled clinical trial.

INTERVENTION

Subjects were fitted with day wear (DW) high-Dk RGP lenses and then adapted to EW. Subjects who adapted to EW were then randomly assigned to either high- or medium-Dk RGP lenses for 12 months of 6-nights/week EW.

MAIN OUTCOME MEASURES

Slit-lamp assessment and grading of 17 possible keratopathies, measurement of refractive error and corneal curvature, and symptoms. Follow-up data were collected every 3 months.

RESULTS

From 545 subjects entering the DW adaptation phase, 201 adapted to EW and were randomly assigned to medium- or high-Dk lenses for 12 months of EW. The baseline characteristics of the two study groups were similar and did not differ from the 344 DW subjects who failed to adapt to EW. The distributions of oxygen transmissibility for the two study groups were disjoint, indicating that each group received distinctly different levels of hypoxia.

CONCLUSIONS

We show that CLEWS was appropriately designed to address the study hypotheses, was conducted with regard for the safety of the subjects, and adhered to rigorous protocols designed to control for bias and ensure the integrity of study data. We establish the internal validity of between-group statistical comparisons and characterize our study population to permit informed evaluation of the applicability of our results to the contact lens-wearing population in general.

The Berkeley Contact Lens Extended Wear Study. Part II : Clinical results

OBJECTIVE

To describe the principal clinical outcomes associated with 12 months use of rigid gas-permeable (RGP) extended wear contact lenses and address two primary study questions: (1) does extended wear (EW) of high oxygen transmissibility (Dk/t) RGP lenses reduce the incidence of ocular complications, and (2) does the wearing of high-Dk/t lenses reduce the rate of failure to maintain 6-night RGPEW over 12 months?

DESIGN

A randomized, concurrently controlled clinical trial.

INTERVENTION

Subjects who adapted to EW with high Dk (oxygen permeability) RGP lenses were randomized to either high Dk or medium-Dk RGP lenses for 12 months of 6-night EW.

MAIN OUTCOME MEASURES

Contact lens-associated keratopathies (CLAK), changes in refractive error and corneal curvature, and survival in EW.

RESULTS

Two hundred one subjects were randomized to medium or high-Dk lenses for 12 months of EW. Sixty-two percent of the subjects in each group completed 12 months of EW; however, the probability of failure was significantly greater for the medium-Dk group. Although the risk of complications was similar for the two groups, the number of CLAK events that led to termination were 16 versus 5 for the medium-Dk and high-Dk groups, respectively. This suggests that the type of adverse response or the inability to reverse an adverse event was different for the group being exposed to the lower oxygen dose.

CONCLUSIONS

The level of oxygen available to the cornea has a significant impact on maintaining successful RGP extended contact lens wear, but not on the initial onset of CLAK. The number of clinical events leading to termination was substantially higher for the medium Dk group, which suggests that corneal hypoxia is an important factor in the development of CLAK. Although overnight contact lens wear should be recommended with caution and carefully monitored for early detection of ocular complications, it appears that high-Dk RGP lenses can be a safe and effective treatment for correction of refractive error for most individuals who can adapt to EW.

The effects of one-hour wear of high-Dk soft contact lenses on corneal pH and epithelial permeability

PURPOSE

Previous studies have shown that 1-hour closed-eye contact lens wear with a low-Dk lens causes a significant reduction in corneal pH and an increase in epithelial permeability. In the present study, we evaluated the effects of super-high-Dk/t soft lenses on corneal epithelial barrier function and stromal pH.

METHODS

Corneal thickness was measured by optical pachometry, while epithelial permeability and stromal pH were measured by fluorophotometry. A paired-eye design was used in which one eye was randomly allocated to wear a high-oxygen-permeable soft lens (CIBAVision Focus/NIGHT & DAY (Dk/t= 175) while the other eye did not wear a lens.

RESULTS

After 1-hour closed-eye lens wear, neither the difference in corneal swelling (P = 0.206) nor the permeability (P = 0.055) between both eyes was significantly different. The mean pH values under open-eye conditions were 7.66 vs. 7.57 for the treatment and control eyes, respectively (P = 0.082), dropping to 7.27 vs. 7.25 after 1-hour eye closure (P = 0.283).

CONCLUSIONS

Although our results are limited to a 1-hour observation period, they do provide evidence that high-Dk materials may eliminate corneal acidosis and reduced epithelial barrier function that accompany closed-eye contact lens wear with lower-Dk soft lens materials.

Measurement of post-lens tear thickness

PURPOSE

A method to measure the tear film beneath a soft contact lens, referred to as post-lens tear thickness (PLTT), would have many applications to contact lens research. In this study a noninvasive technique for measuring the PLTT is presented.

METHODS

The feasibility of measuring the tear layer by optical pachometry was first assessed using a model eye. The baseline corneal thickness (B) of both eyes of 21 subjects was measured, etafilcon-A ionic disposable soft contact lenses (58% water) were inserted, and the total thickness (T) of the cornea, contact lens, and PLTT were measured. After the pachometry readings the lenses were removed and their center thickness (C) determined. The PLTT was calculated using the equation: PLTT = T-(B+C). Two sets of measurements of T were performed at 15 and 25 minutes after lens insertion. The entire procedure was repeated at a second visit.

RESULTS

The pachometry measurements of the small aqueous reservoir between the model eye and the lens closely matched those obtained by direct microscopic measurement. For human PLTT, the mean values (and 95% confidence intervals) for right eyes on visits 1 and 2 were 11 (8, 13) and 12 (10, 15) microm, respectively, and for left eyes were 12 (10, 15) and 11 microm (8, 14) microm, respectively.

CONCLUSIONS

It is possible to measure the post-lens tear thickness using optical pachometry. The variability between repeated measurements suggests that with careful sample size planning, the technique is sufficiently precise to be useful in group assessments of PLTT.

Predicting RGP daily wear success

PURPOSE

While most clinicians agree that fitting of rigid gas permeable (RGP) lenses is the preferred treatment strategy for some types of patients, many patients have difficulty adapting to full-time daily wear of these lenses. The Contact Lens Extended Wear Study (CLEWS) is a randomized, controlled clinical trial in which subjects are first adapted to full-time RGP daily wear prior to randomization to either high or medium oxygen transmissibility (Dk/L) RGP lenses for 12 months of extended wear. The CLEWS pre-randomization data provide an opportunity to examine the reasons some patients fail to adapt to RGP daily wear and to determine whether a patient's demographic, historical, and ocular characteristics can be used to predict RGP daily wear success.

METHODS

From 1,809 individuals who expressed interest in RGP lenses, 411 subjects passed the CLEWS screening criteria and were fit with high Dk lenses (mean Dk = 92 x 10(-11) [cm2/sec][mL 02/mL x mmHg]). The fitting strategy included minimum apical alignment, lid attachment, centration, and average lens diameters of 9.2 mm. Success was defined as a minimum of 14 hours per day without adverse ocular responses that would contraindicate either full-day daily wear or extended wear.

RESULTS

Of the 411 subjects, 286 (69.6%) were successful with RGP extended wear. Among the 125 failures, 50 were based on clinician findings (e.g., cornea, vision, compliance), while 75 subjects chose to discontinue wear because of unacceptable comfort or poor vision. Multivariate linear logistic regression modeling shows that younger patients with greater corneal curvature (K) and less predicted residual astigmatism have a higher probability of RGP daily wear success.

CONCLUSIONS

Our study showed that RGP lenses can be fit with a relatively high rate of success and that many of those patients who elect to discontinue RGP daily wear report unacceptable comfort as the primary reason. We propose a Bayesian statistical method that will assist clinicians in selecting those candidates for RGP daily wear who are most likely to adapt successfully.