Matrix metalloproteinase-9 knockout confers resistance to corneal epithelial barrier disruption in experimental dry eye.
ABSTRACT: Altered corneal epithelial barrier function is the cause for ocular irritation and visual morbidity in dry eye disease. Increased matrix metalloproteinase (MMP)-9 activity has been observed in the tear fluid of dry eye patients. To determine the pathogenic role of MMP-9 in the corneal epithelial disease of dry eye, the effects of experimentally induced dry eye on corneal epithelial morphology and barrier function were compared in MMP-9 knockout mice and their wild-type littermates. Dry eye was created through cholinergic blockade and exposure to a desiccating environment. The tear fluid MMP-9 concentration increased in response to dryness in wild-type mice. Corneal epithelial permeability to three different-sized molecules increased in dry eye wild-type mice, but not in MMP-9 knockout mice. Topical administration of active MMP-9 to dry eye MMP-9 knockout mice significantly increased corneal epithelial permeability. Compared to MMP-9 knockout mice, wild-type mice showed greater desquamation of differentiated apical corneal epithelial cells that expressed the tight junction protein occludin in response to dryness. This was accompanied by an increase in lower sized (50 kd) occludin in the corneal epithelia of wild-type mice. These findings could be replicated in cultured human corneal epithelial cells that were treated with active MMP-9. These studies indicate that increased MMP-9 activity on the ocular surface in response to dryness disrupts corneal epithelial barrier function. This appears to be because of accelerated loss of tight junction bearing superficial corneal epithelial cells, perhaps by proteolytic cleavage of occludin.
Project description:Dry eye disease (DED) is a multifactorial disease associated with ocular surface inflammation. Toll-like receptors (TLRs) are integral in the initiation of inflammatory signaling. Therefore, we evaluated the effect of TLR-deficiency on dry eye-related ocular surface damage and inflammation using a mouse model of experimental dry eye (EDE).C57BL/6 wild-type (WT), MyD88-/-, and IL-1R-/- mice were exposed to EDE conditions for 5 days. Tear production was measured by phenol red thread test and ocular surface damage assessed with fluorescein staining. Corneal homogenates were obtained for matrix metalloproteinase (MMP) and cytokine expression analysis by Luminex assay and quantitative PCR. In addition, whole eyes and eyelids were dissected and goblet cells and Meibomian glands were imaged, respectively.Following 5 days of EDE, WT mice had extensive ocular surface staining, while MyD88-/- mice had no increased staining above non-EDE conditions. Similarly, MyD88-/- mice did not have increased corneal MMP-2, 3, or 8 concentrations, as seen with WT mice. MyD88-deficiency also resulted in decreased corneal cytokine levels. In addition, MyD88-/- mice had significantly lower conjunctival goblet cell counts compared with both WT (EDE) and IL-1R-/- (non-EDE) mice. However, there was no difference in Meibomian gland morphology between WT, IL-1R-/-, and MyD88-/- mice.These studies demonstrate the importance of TLR signaling in dry eye development. Mice lacking TLR signaling, MyD88-/-, were protected from EDE-induced ocular surface damage and inflammatory mediator expression, warranting further investigation into TLR inhibition as a potential therapeutic for DED.
Project description:Sjögren's syndrome (SS) is a chronic, autoimmune exocrinopathy that leads to severe dryness of the mouth and eyes. Exocrine function is highly regulated by neuronal mechanisms but little is known about the link between chronic inflammation, innervation and altered exocrine function in the diseased eyes and exocrine glands of SS patients. To gain a better understanding of neuronal regulation in the immunopathogenesis of autoimmune exocrinopathy, we profiled a mouse model of spontaneous, autoimmune exocrinopathy that possess key characteristics of peripheral neuropathy experienced by SS patients. Mice deficient in the autoimmune regulator (Aire) gene developed spontaneous, CD4+ T cell-mediated exocrinopathy and aqueous-deficient dry eye that were associated with loss of nerves innervating the cornea and lacrimal gland. Changes in innervation and tear secretion were accompanied by increased proliferation of corneal epithelial basal cells, limbal expansion of KRT19-positive progenitor cells, increased vascularization of the peripheral cornea and reduced nerve function in the lacrimal gland. In addition, we found extensive loss of MIST1+ secretory acinar cells in the Aire -/- lacrimal gland suggesting that acinar cells are a primary target of the disease, Finally, topical application of ophthalmic steroid effectively restored corneal innervation in Aire -/- mice thereby functionally linking nerve loss with local inflammation in the aqueous-deficient dry eye. These data provide important insight regarding the relationship between chronic inflammation and neuropathic changes in autoimmune-mediated dry eye. Peripheral neuropathies characteristic of SS appear to be tightly linked with the underlying immunopathological mechanism and Aire -/- mice provide an excellent tool to explore the interplay between SS-associated immunopathology and peripheral neuropathy.
Project description:Dry Eye disease causes discomfort and pain in millions of patients. Using a mouse acute desiccating stress (DS) model we show that DS induces a reduction in intraepithelial corneal nerve (ICN) density, corneal sensitivity, and apical extension of the intraepithelial nerve terminals (INTs) that branch from the subbasal nerves (SBNs). Topical application of 0.02% Mitomycin C (MMC) or vehicle alone has no impact on the overall loss of axon density due to acute DS. Chronic dry eye, which develops progressively as C57BL/6 mice age, is accompanied by significant loss of the ICNs and corneal sensitivity between 2 and 24 months of age. QPCR studies show that mRNAs for several proteins that regulate axon growth and extension are reduced in corneal epithelial cells by 24 months of age but those that regulate phagocytosis and autophagy are not altered. Taken together, these data demonstrate that dry eye disease is accompanied by alterations in intraepithelial sensory nerve morphology and function and by reduced expression in corneal epithelial cells of mRNAs encoding genes mediating axon extension. Précis: Acute and chronic mouse models of dry eye disease are used to evaluate the pathologic effects of dry eye on the intraepithelial corneal nerves (ICNs) and corneal epithelial cells. Data show reduced numbers of sensory nerves and alterations in nerve morphology, sensitivity, corneal epithelial cell proliferation, and expression of mRNAs for proteins mediating axon extension accompany the pathology induced by dry eye.
Project description:Lubricin may be an important barrier to the development of corneal and conjunctival epitheliopathies that may occur in dry eye disease and contact lens wear.To test the hypotheses that lubricin (ie, proteoglycan 4 [PRG4 ]), a boundary lubricant, is produced by ocular surface epithelia and acts to protect the cornea and conjunctiva against significant shear forces generated during an eyelid blink and that lubricin deficiency increases shear stress on the ocular surface and promotes corneal damage.Human, porcine, and mouse tissues and cells were processed for molecular biological, immunohistochemical, and tribological studies, and wild-type and PRG4 knockout mice were evaluated for corneal damage.Our findings demonstrate that lubricin is transcribed and translated by corneal and conjunctival epithelial cells. Lubricin messenger RNA is also present in lacrimal and meibomian glands, as well as in a number of other tissues. Absence of lubricin in PRG4 knockout mice is associated with a significant increase in corneal fluorescein staining. Our studies also show that lubricin functions as an effective friction-lowering boundary lubricant at the human cornea-eyelid interface. This effect is specific and cannot be duplicated by the use of hyaluronate or bovine serum albumin solutions.Our results show that lubricin is transcribed, translated, and expressed by ocular surface epithelia. Moreover, our findings demonstrate that lubricin presence significantly reduces friction between the cornea and conjunctiva and that lubricin deficiency may play a role in promoting corneal damage.
Project description:This Phase 2 clinical trial assessed the efficacy and safety of the novel antioxidative, renewable compound SkQ1 for topical treatment of dry eye signs and symptoms.In a single-center, randomized, double-masked, placebo-controlled, 29-day study, 91 subjects with mild to moderate dry eye instilled the study drug twice daily and recorded dry eye symptoms daily. Subjects were randomized 1:1:1 into one of three ophthalmic solution treatment groups: SkQ1 1.55 µg/mL, SkQ1 0.155 µg/mL, or 0.0 µg/mL (placebo). Subjects were exposed to a controlled adverse environment chamber at 3 of the 4 study visits (Day -7, Day 1, and Day 29). Investigator assessments occurred at all study visits.SkQ1 was safe and efficacious in treating dry eye signs and symptoms. Statistically significant improvements with SkQ1 compared to placebo occurred for the dry eye signs of corneal fluorescein staining and lissamine green staining in the central region and lid margin redness, and for the dry eye symptoms of ocular discomfort, dryness, and grittiness. In addition, SkQ1 demonstrated greater efficacy compared to placebo, although the differences were not statistically significant, for corneal fluorescein staining in other regions and/or time points (total staining score, central region, corneal sum score, and temporal region), lissamine green staining for the central and nasal regions, and blink rate scores.This Phase 2 study indicated that SkQ1 is safe and efficacious for the treatment of dry eye signs and symptoms and supported previous study results.Clinicaltrials.gov identifier: NCT02121301.Miotech S.A.
Project description:Dry eye disease (DED) is a multifactorial ocular surface disorder affecting millions of individuals worldwide. Inflammation has been associated with dry eye and anti-inflammatory drugs are now being targeted as the alternate therapeutic approach for dry eye condition. In this study, we have explored the anti-inflammatory and autophagy modulating effect of chloroquine (CQ) in human corneal epithelial and human corneal fibroblasts cells exposed to desiccation stress, (an in-vitro model for DED). Gene and protein expression profiling of inflammatory and autophagy related molecular factors were analyzed in HCE-T and primary HCF cells exposed to desiccation stress with and without CQ treatment. HCE-T and HCF cells exposed to desiccation stress exhibited increased levels of activated p65, TNF-?, MCP-1, MMP-9, and IL-6. Further, treatment with CQ decreased the levels of active p65, TNF-?, MCP-1, and MMP-9 in cells underdesiccation stress. Increased levels of LC3B and LAMP1 markers in HCE-T cells exposed to desiccation stress suggest activation of autophagy and the addition of CQ did not alter these levels. Changes in the phosphorylation levels of MAPKinase and mTOR pathway proteins were found in HCE-T cells under desiccation stress with or without CQ treatment. Taken together, the data suggests that HCE-T cells under desiccation stress showed NF?B mediated inflammation, which was rescued through the anti-inflammatory effect of CQ without altering the autophagy flux. Therefore, CQ may be used as an alternate therapeutic management for dry eye condition.
Project description:In this study, we explored the effects of particulate matter 2.5 (PM2.5) eye drops on the ocular surface structure and tear function in mice and established a novel animal model for dry eye research. We found that, following treatment with PM2.5, the tear volume and, the tear film break-up time showed statistical differences at each time point (P?<?0.05). The FL score of the PM2.5-treated group was higher than that of others (P?<?0.05). The average number of corneal epithelial layer cells in groups A and B was significantly lower than that in group C (P?<?0.05). Scanning electron microscopy and transmission electron microscopy revealed that the number of corneal epithelial microvilli and corneal desmosomes was drastically reduced in group C. PM2.5 induced apoptosis in the corneal superficial and basal epithelium and led to abnormal differentiation and proliferation of the ocular surface with higher expression levels of Ki67 and a reduced number of goblet cells in the conjunctival fornix in group C. PM2.5 significantly increased the levels of TNF-?, NF-?B p65 (phospho S536), and NF-?B in the cornea. Thus, the topical administration of PM2.5 in mice induces ocular surface changes that are similar to those of dry eye in humans, representing a novel model of dry eye.
Project description:Purpose: This work aimed to identify differentially expressed circular RNAs (circRNAs) and elucidate their potential function in aquaporin 5 (AQP5) knockout (AQP5-/-) mice with the primary dry eye phenotype. Methods: A slit lamp examination was performed on AQP5-/- mice to assess corneal epithelial defects using fluorescein sodium staining. Hematoxylin-eosin staining and transmission electron microscopy analysis were performed to identify structural changes in lacrimal gland epithelial cells due to AQP5 deficiency. The expression profiles of circRNA and messenger RNA (mRNA) were determined by a microarray analysis. The selected circRNA was verified by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to predict the biological functions and the potential pathways of parental genes involved in lacrimal gland epithelial cell changes. According to the bioinformatics analysis of identified circRNAs, we predicted a circRNA-miRNA-mRNA network of phagosomes. Results: The AQP5-/- mice spontaneously exhibit dry eye symptoms, wherein the AQP5 deficiency changes the structure of lacrimal gland epithelial cells. The analysis revealed that, compared to AQP5+/+ mice, 30 circRNAs in the lacrimal glands of AQP5-/- mice were differentially expressed (fold change ? 2.0, p < 0.05). Nine upregulated circRNAs were identified using qRT-PCR, and nine upregulated validated circRNAs, 40 altered microRNAs (miRNAs), and nine upregulated mRNAs were identified through a network analysis. The KEGG analysis showed that these nine target genes were expressed in phagosomes. Conclusion: The AQP5-/- mice have primary and stable dry eye phenotypes from birth. We identified differently expressed circRNAs in the lacrimal glands of AQP5-/- and AQP5+/+ mice, predicting a circRNA-miRNA-mRNA network of phagosomes. CircRNA likely plays an important role in lacrimal gland epithelial cell pathogenesis. Therefore, it is reasonable to use circRNA as a potential therapeutic agent for the treatment of dry eyes.
Project description:Background:This study measured longitudinal changes in dry eye disease (DED) symptoms and signs following lifitegrast therapy and assessed their relationship to tear osmolarity to test the hypothesis that a decline in tear osmolarity is a reliable leading indicator of subsequent improvement in DED symptoms and signs after initiating lifitegrast treatment. Methods:This phase IV, prospective, single-arm, open-label, 12-week study enrolled subjects aged ≥18 years with eye dryness score ≥40 (0-100 VAS) and tear osmolarity ≥308 mOsm/L. Subjects were prescribed lifitegrast ophthalmic solution 5%, twice daily in each eye. DED symptoms were assessed via VAS at baseline and 2, 6, and 12 weeks. Signs included tear osmolarity, meibomian gland dysfunction, tear breakup time, and fluorescein corneal staining. In post-hoc analysis, subjects with ≥5 mOsm/L decrease in osmolarity over 12 weeks were Responders. Results:Of 26 subjects in the intent-to-treat population, 23 were female; mean age was 67.4 years. Baseline mean±SD eye dryness was 68.7±16.5 and tear osmolarity was 317.8±8.5 mOsm/L. All seven symptoms (dryness, burning, foreign body sensation, pain, photophobia, itching, blurred vision) declined significantly (P<0.01) from baseline to 6 and 12 weeks. Signs did not change significantly. For 13 Responders, tear osmolarity decreased from baseline to 12 weeks (319.2±8.5 to 300.6±12.3 mOsm/L, P<0.001) and corneal staining trended toward improvement (1.1±0.9 to 0.6±0.7, P=0.136). Among Nonresponders, osmolarity increased from 316.4+8.7 to 329.6+13.9 (P<0.01) and corneal staining showed no change (1.3±0.8 to 1.0±0.7 at 12 weeks, P=0.293). Conclusions:Lifitegrast reduced DED symptoms among subjects with moderate-to-severe disease (severity defined by VAS for eye dryness). Potential reasons that may underlie the dichotomous effect of drug treatment on tear osmolarity are discussed.
Project description:To determine high-mobility group box 1 (HMGB1) expression during experimental dry eye (EDE) and dry eye-like culture conditions and elucidate its role in corneal dry eye-related inflammation.EDE was induced in 8- to 12-week-old C57BL/6 mice. Corneal tissue sections and lysates from EDE and untreated mice were evaluated for HMGB1 expression by immunostaining and quantitative real-time PCR (qPCR). For in vitro studies, human corneal epithelial cells (HCEC) were treated with hyperosmolar media, toll-like receptor (TLR) agonists, or proinflammatory cytokines to determine HMGB1 expression. HCEC were also treated with human recombinant HMGB1 (hrHMGB1) alone or in combination with inflammatory stimuli, and TNF?, IL-6, and IL-8 expression evaluated by qPCR and ELISA. Nuclear factor-?B (NF-?B) p65 nuclear translocation was determined by immunostaining.EDE mice had higher corneal HMGB1 RNA and protein expression compared to untreated animals. In HCEC, hyperosmolar stress and TNF? treatment stimulated HMGB1 production and secretion into culture supernatants. However, in vitro stimulation with hrHMGB1 did not induce secretion of TNF?, IL-6, or IL-8 or NF-?B p65 nuclear translocation. In addition, the inflammatory response elicited by TLR agonists fibroblast-stimulating lipopeptide-1 and lipopolysaccharide was not enhanced by hrHMGB1 treatment.HMGB1 expression was enhanced by dry eye conditions in vivo as well as in vitro, during hyperosmolar stress and cytokine exposure, suggesting an important role for HMGB1 in dry eye disease. However, no direct inflammatory effect was observed with HMGB1 treatment. Therefore, under these conditions, HMGB1 does not contribute directly to dry eye-induced inflammation and its function at the ocular surface needs to be explored further.