Tear fluid plasmin activity of dry eye patients with Sjögren's syndrome

Sex Hormones and Calcitonin Gene-Related Peptide in Women With Migraine: A Cross-sectional, Matched Cohort Study

BACKGROUND AND OBJECTIVES

Sex hormones may modulate calcitonin gene-related peptide (CGRP) release in the trigeminovascular system. We studied CGRP concentrations in plasma and tear fluid in female participants with episodic migraine (EM) and a regular menstrual cycle (RMC), female participants with EM and combined oral contraception (COC), and female participants with EM in the postmenopause. For control, we analyzed 3 corresponding groups of age-matched female participants without EM.

METHODS

Participants with an RMC had 2 visits: during menstruation on menstrual cycle day 2 ± 2 and in the periovulatory period on day 13 ± 2. Participants with COC were examined at day 4 ± 2 of the hormone-free interval (HFI) and between days 7 and 14 of hormone intake (HI). Postmenopausal participants were assessed once at a random time point. Plasma and tear fluid samples were collected at each visit for determination of CGRP levels with an ELISA.

RESULTS

A total of 180 female participants (n = 30 per group) completed the study. Participants with migraine and an RMC showed statistically significantly higher CGRP concentrations in plasma and tear fluid during menstruation compared with female participants without migraine (plasma: 5.95 pg/mL [IQR 4.37-10.44] vs 4.61 pg/mL [IQR 2.83-6.92], p = 0.020 [Mann-Whitney U test]; tear fluid: 1.20 ng/mL [IQR 0.36-2.52] vs 0.4 ng/mL [IQR 0.14-1.22], p = 0.005 [Mann-Whitney U test]). In contrast, female participants with COC and in the postmenopause had similar CGRP levels in the migraine and the control groups. In migraine participants with an RMC, tear fluid but not plasma CGRP concentrations during menstruation were statistically significantly higher compared with migraine participants under COC (p = 0.015 vs HFI and p = 0.029 vs HI, Mann-Whitney U test).

DISCUSSION

Different sex hormone profiles may influence CGRP concentrations in people, with current or past capacity to menstruate, with migraine. Measurement of CGRP in tear fluid was feasible and warrants further investigation.

Recent advances in superlubricity of liposomes for biomedical applications

Achieving superlubricity, a state of lubrication where friction nearly vanishes, has become one of the most promising approaches to combat friction-induced energy dissipation and medical device failure. Phospholipids are amphiphilic molecules comprising highly hydrophilic phosphatidylcholine head groups as well as hydrophobic hydrocarbon chains, When solubilized, phospholipids can readily self-assemble to form different structures such as bilayers and vesicles (liposomes). Recently, liposomes have been identified as excellent lubricants, especially in the boundary lubrication regime the most common lubrication status in the field of biotribology. In this review, we summarize recent progress in employing liposomes as key players for employing superlubricity in biomedical applications. The relationship between lipids and liposomes, manufacturing approaches, lubrication regimes, and regulation mechanisms of liposomes are discussed. Finally, we indicate possible future directions for the use of liposome-mediated superlubricity in biomedical applications.

New Insights on Plasmin Long Term Stability and the Mechanism of Its Activity Inhibition Analyzed by Quartz Crystal Microbalance

We used the research quartz crystal microbalance (RQCM) to monitor regulatory effects of plasmin and trypsin in the presence of their inhibitor α₂-antiplasmin. The gold surface of quartz crystals was modified with a β-casein layer that served as a substrate for protease digestion. The addition of plasmin or trypsin as well as their mixtures with α₂-antiplasmin resulted in an increase of resonant frequency, f, and in a decrease of motional resistance, R_m, depending on the molar ratio of protease: antiplasmin. At equimolar concentrations of protease and α₂-antiplasmin (5 nM:5 nM) full inhibition of protease activity took place. Monitoring of plasmin activity on an hourly and daily basis revealed a prominent effect of autolysis and decrease of plasmin activity in freshly activated samples. The degree of inhibition as well as plasmin half-life (t_1/2 = 2.48 ± 0.28 days) connected with its degradation was determined.

TFOS DEWS II Tear Film Report

The members of the Tear Film Subcommittee reviewed the role of the tear film in dry eye disease (DED). The Subcommittee reviewed biophysical and biochemical aspects of tears and how these change in DED. Clinically, DED is characterized by loss of tear volume, more rapid breakup of the tear film and increased evaporation of tears from the ocular surface. The tear film is composed of many substances including lipids, proteins, mucins and electrolytes. All of these contribute to the integrity of the tear film but exactly how they interact is still an area of active research. Tear film osmolarity increases in DED. Changes to other components such as proteins and mucins can be used as biomarkers for DED. The Subcommittee recommended areas for future research to advance our understanding of the tear film and how this changes with DED. The final report was written after review by all Subcommittee members and the entire TFOS DEWS II membership.

Laminin isoform profiles in salivary glands in Sjögren's syndrome

Five different laminin (LM) alpha, four LM-beta, and three LM-gamma chains form the 15-16 currently known approximately 400-900 kDa heterodimeric LM-monomers, which self-assemble in the lamina lucida of the basement membrane (BM) to a network, connected with nidogens and perlecans with the underlying type IV collagen network. In labial salivary glands (LSG), the structurally organizing/polarizing BM separates the tubuloacinar epithelium from the connective tissue stroma but plays regulatory roles as well. Tissue distribution of LM-alpha, -beta, and -gamma chains is described, and application of the known combinatorial rules allows some conclusions also on the corresponding distribution of the LM-trimers. Currently, known integrin (Int) and non integrin (e.g., dystroglycans and Lutheran blood group antigens) LM-receptors are described. LMs are regulated at transcriptional, translational, and posttranslational levels, together with the regulation of alternative splicing, binding partners (assembly), secretion, and degradation. In LSGs, LM-alpha1, -alpha2, and -alpha4 are only found in the acinar (not ductal) BM, LM-alpha4 also in the periductal/ interstitial stroma. Pattern recognition disclosed irregular expression in the acinar BM, suggesting some dynamic and/or regulatory role. It seems that in a female-dominant autoimmune exocrinopathy, Sjögren's syndrome (SS), LM-alpha1 and -alpha2 are decreased, together with their Int alpha1beta1 and alpha2beta1 receptors. Because LM-111/211-to-Int-alpha1beta1/alpha2beta1 interactions play a crucial role in the transdifferentiation of the intercalated duct progenitors to secretory acinar cells, acinar remodeling is impaired in SS. Disturbed hemidesmosomal Int alpha6beta4/LM-332 interactions in SS may lead to acinar cell anoikis. Interestingly, dehydroepiandrosterone (DHEA) prohormone and its intracrine androgenic dihydrotestosterone (DHT) end product upregulate at least Int alpha1beta1/alpha2beta1, whereas LM-alpha1 is upregulated by outside-in LM-111/211-to-Int-alpha1beta1/alpha2beta1 signaling. It seems that LM alterations precede the lymphocyte infiltration, suggesting that acinar BM-Int pathology, perhaps related to endo- and intracrine sex steroid metabolism, represents an early pathogenic phases in SS.

A Protein Dye-Binding Assay on Cellulose Membranes for Tear Protein Quantification

PURPOSE

To develop a method to quantify tear protein concentration with the sensitivity to measure this variable in the restricted volumes of single human tear samples.

METHODS

Aliquots of tear fluid from healthy subjects and a solution of standard bovine serum albumin (BSA) were spotted on cellulose membranes. Membranes were fixed, stained for protein with Coomassie blue, and washed until they displayed clear backgrounds. Stained spots were excised and eluted in a defined volume of methanol-ammonia, and the absorbance was determined spectrophotometrically at 610 nm. Membranes were calibrated by calculating their apparent thickness from the areas of stained spots and the corresponding aliquot volumes of either tear fluid or BSA solution.

RESULTS

In our dye-binding assay, absorbance (0-1.00 OD) was found to have a linear relation with tear fluid volume (1-7 microL). In a study involving samples from 33 healthy subjects, aliquots (3 microL) of tear fluid were found to yield absorbances in the linear range. Protein concentrations in tear fluid were found to be distributed over the range of 2.20-6.37 mg/mL (mean, 4.11 +/- 1.00 mg/mL) with no apparent sex differences. The assay can be applied successfully to quantify protein concentrations in tear fluid by using calibrated Schirmer strips after a tear test. Electrophoretic profiles of proteins present in tear fluid sampled from different healthy individuals were nearly identical when normalized for protein load by using this method.

CONCLUSIONS

The protein dye-binding assay we developed by using cellulose membranes or Schirmer strips is an efficient and convenient method for measuring tear protein concentration.

Inflammation in dry eye

Dry eye is a condition of altered tear composition that results from a diseased or dysfunctional lacrimal functional unit. Evidence suggests that inflammation causes structural alterations and/or functional paralysis of the tear-secreting glands. Changes in tear composition resulting from lacrimal dysfunction, increased evaporation and/or poor clearance have pro-inflammatory effects on the ocular surface. This inflammation is responsible in part for the irritation symptoms, ocular surface epithelial disease, and altered corneal epithelial barrier function in dry eye. Anti-inflammatory therapies for dry eye target one or more of the inflammatory mediators/pathways that have been identified in dry eye.

Research in Dry Eye: Report of the Research Subcommittee of the International Dry Eye WorkShop (2007)

Members of the DEWS Research Subcommittee reviewed research into the basic mechanisms underlying dry eye disease. Evidence was evaluated concerning the tear film, lacrimal gland and accessory lacrimal glands, ocular surface epithelia (including cornea and conjunctiva), meibomian glands, lacrimal duct system and the immune system. Consideration was given to both animal and human research data. Results are presented as a series of information matrices, identifying what is known and providing supporting references. An attempt is made to identify areas for further investigation.

[Ocular surface investigations in dry eye]

Dry eye is a complex clinicopathological entity involving tear film, lacrimal glands, eyelids, and a wide spectrum of ocular surface cells, including epithelial, inflammatory, immune, and goblet cells. From the tightly regulated lacrimal film functions and structure, a large variety of investigations have been developed, including tear meniscus measurements, fluorophotometry, meibometry, interference pattern analysis, evaporation rate, tear osmolarity, and thermography. Dry eye conditions also interfere with the ocular surface, causing corneal irregularities that may be explored using the techniques of videokeratography and in vivo confocal microscopy, or optical impairment, as confirmed by aberrometry. At the level of ocular surface cells, impression cytology remains a standard for assessing cell alterations. It has greatly benefited from new confocal microscopy, molecular biology, and flow cytometry techniques. Biological assessment of tear proteins or other mediators is also useful. Major limits should be acknowledged, however, such as technical issues in tear film collection, especially in dry eyes, and the lack of standardization of most measurements. Tear osmolarity, electrophoresis, and dosage of normal tear proteins, such as lysozyme or lactoferrin, remain the most useful tests. Finally, some extraocular explorations such as accessory gland biopsy or serum antinuclear antibody dosage may be useful for assessing the diagnosis of Sjögren's syndrome.

Use of Polyurethane Minisponges to Collect Human Tear Fluid

PURPOSE

To characterize a method of tear collection based on the use of amphiphilic polyurethane absorbing minisponges.

METHODS

Tear fluid was collected from 17 healthy volunteers. A preweighed polyurethane dry minisponge was laid on the margin of the lower eyelid. Once wet (5-10 minutes), the fluid was transferred to a preweighed Eppendorf tube after squeezing the sponge by centrifugation. The amount of fluid absorbed and fluid recovered were determined by reweighing the sponge and the tube after absorption and centrifugation steps, respectively. The fluid was qualitatively characterized by electrophoretic polypeptide profiling in Coomassie blue-stained SDS-polyacrylamide gels.

RESULTS

Per eye, 14.6 +/- 5.3 microL tear fluid was collected. That volume was about 90% of the fluid absorbed by polyurethane minisponges, almost doubling the fraction recovered from other more hydrophilic absorbing polymers. Major bands characterizing the electrophoretic profile of this fluid were those of 79, 66, 27, 18, and 14 kd. This profile was indistinguishable from that of tear fluid aspirated into glass microcapillaries. Tear fluid collected simultaneously from both eyes displayed the same profiles. Successive tear samples from a single eye showed the same profile except for the 66-kd band, which increased steadily as collection proceeded. Tear donors rarely complained of discomfort.

CONCLUSIONS

Tear collection by absorbing polyurethane minisponges is highly advantageous in efficiency (recovery) and reproducibility (invariant electrophoretic polypeptide profiles). Tear donor comfort, simultaneous bilateral collection, and collections from several donors at once are additional major advantages of this collection method in studies involving single subjects and populations in health and disease.

The tear (lacrimal) meniscus height in human eyes: a useful clinical measure or an unusable variable sign?

PURPOSE

To review notes and reports in the literature on assessments of human tear meniscus height (TMH) with the view to defining what the current state of knowledge is, and allow comparisons with data obtained on elderly individuals.

METHODS

TMH data was obtained from 97 elderly individuals without significant eye disease. Photo-slit-lamp views, perpendicular to the lower marginal tear strip, were used to obtain close-up images by videography over approximately 30s. Repeated measures at the same location separated by a few seconds (time-dependent TMH measures, tTMH), or repeated measures along the length of the middle portion of the lower eyelid (position-dependent TMH measures, pTMH) were made. The results were compared to those from published reports of TMH.

RESULTS

For elderly individuals, tTMH averaged 0.185+/-0.088 mm, while pTMH averaged 0.189+/-0.093 mm. The distribution of TMH measures however included a number of data sets with a much higher average, and which could be separated from the main group of data using cluster analyses approach (> 0.23 mm, P < 0.001). Literature-reported values for TMH, assessed by a perpendicular view, average 0.215 mm (range of average values from 0.163 to 0.350 mm), whereas those made from a tangential view average 0.343 mm (range 0.215-0.460 mm).

CONCLUSIONS

The average TMH value of close to 0.2mm in the elderly, as compared to the small number of individuals with rather greater TMH values of up to 0.7 mm, might therefore be considered as indicative of their having normal tear volume, with a few individuals having reflex tearing. Based on the data and literature values, a lower cut-off limit for normal would be </=0.1 mm, while >/=0.25 mm would indicate reflex tearing and/or sub-optimal tear drainage. An alternative interpretation is that elderly individuals have a subnormal tear film volume, with just a few individuals having adequate tear volume. Further work is clearly needed to resolve this issue.

Ocular Rosacea

Rosacea is a common skin disease that frequently involves the eye. Although the pathogenesis of the disease remains undefined, recent findings suggest that an altered inflammatory response plays an important role in both cutaneous and ocular rosacea. Ocular manifestations include lid and ocular surface alterations. Chronic inflammation can lead to corneal vascularization, which may compromise vision. Treatment of ocular rosacea is aimed at preventing irritation of the ocular surface (e.g., lubricants, lid hygiene) and controlling inflammation with topical and systemic anti-inflammatory drugs. Systemic tetracyclines are the mainstay of treatment. These drugs act multifactorially by decreasing bacterial flora and the expression of matrix metalloproteinases, altering meibum secretion, inhibiting the production of bacterial lipases, and providing an immunomodulatory effect.

Viability of porcine corneal epithelium ex vivo and effect of exposure to air: a pilot study for a dry eye model

PURPOSE

To explore the use of an ex vivo, in situ porcine cornea as a model for dry eye (exposure keratitis).

METHODS

Twenty-seven porcine eyes were obtained from freshly killed animals at the local abattoir. The viability of 9 corneas (control-baseline group) was assessed within 5 minutes after enucleation on site. A further 18 eyes were transported to the laboratory, where they were exposed to ambient conditions for 4 hours (experimental group A, 6 eyes), for 6 hours (experimental group B, 6 eyes), and for 4 hours with wetting with Dulbecco Phosphate-Buffered Saline every 5 minutes (exposure control group, 6 eyes). All corneas were assessed by trypan blue exclusion for cell viability.

RESULTS

The number of dead cells in the central region was significantly greater than those in the peripheral region (P < 0.05) in all groups. The number of dead cells in both corneal areas increased significantly (P < 0.05) in the experimental groups with time of exposure, but there was no significant increase in the exposure control group.

CONCLUSION

Preliminary data on the number of dead cells in porcine corneal epithelium after enucleation and the effect of exposure were obtained. It was found that after exposure to air, the corneal cells were maintained well by regular wetting, but there was progressively greater cell damage with exposure without wetting. These baseline data will be useful for the further development of the porcine dry eye model to investigate exposure keratitis.

TGF-beta1 stimulates production of gelatinase (MMP-9), collagenases (MMP-1, -13) and stromelysins (MMP-3, -10, -11) by human corneal epithelial cells

Matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of ocular surface diseases. This study investigated the regulated expression of gelatinases (MMP-2 and -9), collagenases (MMP-1 and -13) and stromelysins (MMP-3, -10, and -11) by TGF-beta1 in cultured human corneal epithelial cells. Primary human corneal epithelial cell cultures were grown to confluence and treated with different concentrations (0.1, 1.0, 10 ng ml(-1)) of TGF-beta1 in serum-free medium for 6-24 hr. Total RNA was isolated from cultured cells with or without TGF-beta1 treatment for 6 hr and subjected to semi-quantitative RT-PCR and Northern hybridization. Conditioned media were collected from cultures with or without TGF-beta1 treatment for 24 hr to evaluate the MMP production by ELISA and activity assays. Semi-quantitative RT-PCR revealed that the expressions of MMP-9, -1, -13, -3, -10 and -11 mRNA were up-regulated by TGF-beta1 in a concentration-dependent fashion, while MMP-2 and MMP-14 production did not change. Northern hybridization confirmed these findings. Gelatin zymography, MMP ELISA and activity assays showed concentration-dependent stimulated production and activity of MMP-9, -1, -13, -3 and -10 protein in the conditioned media of cultures treated for 24 hr with TGF-beta1. In conclusion, our results demonstrate that TGF-beta1 stimulates the expression and production of gelatinase (MMP-9), collagenases (MMP-1, -13) and stromelysins (MMP-3, -10, -11) in human corneal epithelial cells. These findings suggest that TGF-beta1 may play a role in the pathogenesis of MMP mediated ocular surface diseases, such as sterile corneal ulceration.

Surface activity of tear fluid in patients with primary Sjögren's syndrome

Rupture of the preocular tear film leads to formation of a dry spot on the cornea with ocular irritation and symptoms of dry eye. One of the factors determining the stability of the tear film is its surface activity. The purpose of this study was to examine the surface activity of tear fluid from patients with Sjögren's syndrome. Tear fluid was sampled from the eyes of 16 patients with primary Sjogren's syndrome. The surface activity of the sample was measured on a Wilhelmy balance. Maximum and minimum surface tension was 72.2+/-1.7 and 52.9+/-7.4 mN m(-1), respectively. Corresponding values in a previously studied group of normal subjects were 71.5+/-1.3 and 46.6+/-3.8 mN m(-1), respectively. The difference in minimal surface tension was statistically significant (P<0.001). Reduced surface activity may be caused by dysfunction of the Meibomian glands and suggests a mechanism for causing the symptoms of dry eyes.

The diagnosis and management of dry eye: a twenty-five-year review

PURPOSE

To review the advances in the diagnosis, pathogenesis, and management of dry eye disease in the past 25 years.

METHODS

Literature review.

RESULTS

The preocular tear film is a hydrated mucus gel that contains soluble antimicrobial proteins and growth factors that protect and support the ocular surface. The final common pathway in dry eye is a perturbation of the integrated ocular surface/lacrimal gland reflex unit. Diagnostic tests evaluating tear composition and clearance appear to show stronger correlation with the severity of ocular irritation symptoms and keratoconjunctivitis sicca (KCS) than the conventional Schirmer tests. KCS is a condition of abnormal differentiation and mucus production by the ocular surface epithelium that results in a poorly lubricated, abnormally permeable ocular surface that has increased susceptibility to environmental insults. Chronic subclinical ocular surface inflammation appears to play a key role in the pathogenesis of KCS. New therapeutic strategies are aimed at reducing the ocular surface inflammation of dry eye disease.

CONCLUSIONS

There has been a tremendous increase in knowledge regarding dry eye disease in the past 25 years that has resulted in improved diagnostic classification and new targeted therapies.

Elevated tear interleukin-6 levels in patients with Sjögren syndrome

OBJECTIVE

The purpose of the study was to investigate interleukin-6 (IL-6) levels in the tear fluid and sera of patients with Sjögren syndrome (SS).

PARTICIPANTS

Twelve patients with primary SS and 12 normal control subjects participated.

INTERVENTION

Tear fluid and sera were obtained from the study and the control groups. Evaluation of tear fluid and sera IL-6 levels was done by using a quantitative enzyme-linked immunosorbent assay kit. All assays were carried out blindly with respect to diagnosis.

MAIN OUTCOME MEASURES

Tear fluid IL-6 levels were measured.

RESULTS

The mean concentration (+/- standard error) of IL-6 in the tears of patients with SS was elevated significantly compared to that of normal control subjects (88.6+/-16.2 vs. 42.1+/-10.6 pg/ml; P < 0.05). No significant differences were noted in the serum IL-6 levels between the two groups. A significant correlation (r = 0.742, P = 0.006) was found between tear fluid IL-6 levels and the focus score of lip biopsy specimens in patients with SS.

CONCLUSION

Tear fluid IL-6 levels may serve as an important marker for tear gland involvement in SS.