Detection of ocular mucus in normal human conjunctiva and conjunctiva from patients with cicatricial pemphigoid using lectin probes and histochemical techniques

Chronic in vivo exposure to Helicobacter pylori VacA: Assessing the efficacy of automated and long-term intragastric toxin infusion

Helicobacter pylori (Hp) secrete VacA, a diffusible pore-forming exotoxin that is epidemiologically linked to gastric disease in humans. In vitro studies indicate that VacA modulates gastric epithelial and immune cells, but the in vivo contributions of VacA as an important determinant of Hp colonization and chronic infection remain poorly understood. To identify perturbations in the stomachs of C57BL/6 or BALB/C mice that result specifically from extended VacA exposure, we evaluated the efficacy of administering purified toxin using automated infusion via surgically-implanted, intragastric catheters. At 3 and 30 days of interrupted infusion, VacA was detected in association with gastric glands. In contrast to previously-reported tissue damage resulting from short term exposure to Hp extracts administered by oral gavage, extended infusion of VacA did not damage stomach, esophageal, intestinal, or liver tissue. However, several alterations previously reported during Hp infection were detected in animals infused with VacA, including reduction of the gastric mucus layer, and increased vacuolation of parietal cells. VacA infusion invoked an immune response, as indicated by the detection of circulating VacA antibodies. These foundational studies support the use of VacA infusion for identifying gastric alterations that are unambiguously attributable to long-term exposure to toxin.

Three-step monitoring of glycan and galectin profiles in the anterior segment of the adult chicken eye

A histochemical three-step approach is applied for processing a panel of sections that covers the different regions of fixed anterior segment of the adult chicken eye. This analysis gains insight into the presence of binding partners for functional pairing by galectin/lectin recognition in situ. Glycophenotyping with 11 fungal and plant lectins (step 1) revealed a complex pattern of reactivity with regional as well as glycan- and cell-type-dependent differences. When characterizing expression of the complete set of the seven adhesion/growth-regulatory chicken galectins immunohistochemically (step 2), the same holds true, clearly demonstrating profiles with individual properties, even for the CG-1A/B paralogue pair. Testing this set of labeled tissue lectins as probes (step 3) detected binding sites in a galectin-type-dependent manner. The results of steps 2 and 3 reflect the divergence of sequences and argue against functional redundancy among the galectins. These data shape the concept of an in situ network of galectins. As consequence, experimental in vitro studies will need to be performed from the level of testing a single protein to work with mixtures that mimic the (patho)physiological situation, a key message of this report.

Evaluation of ocular surface glycocalyx using lectin-conjugated fluorescein

Purpose:

A glycocalyx plays important roles in the ocular surface epithelium, but there is no direct simple method to evaluate ocular surface glycocalyx. We tested a wheat germ agglutinin conjugate of fluorescein (F-WGA) as a marker to demonstrate ocular surface glycocalyx in vivo.

Methods:

After a 5% F-WGA solution was applied to the eyes of eight healthy volunteers, fluorescent intensities of the central cornea and bulbar conjunctiva were measured by fluorophotometry. A 10% fluorescein-conjugated dextran solution served as the control. Changes in fluorescent intensities of the ocular surface following a challenge with 5% N-acetyl cysteine, a conventional mucolytic agent, were tested in the second experiment. Saline instillation served as a control.

Results:

The ocular surface was diffusely stained by F-WGA. Breakup of the precorneal tear film was not apparent, possibly because F-WGA was bound to the glycocalyx of the ocular surface epithelium. F-WGA fluorescent intensities were high in the superior, nasal, and inferior regions of the bulbar conjunctiva and low in the temporal conjunctiva and cornea. No such regional differences were observed with fluorescein-conjugated dextran. F-WGA fluorescent intensities decreased significantly with N-acetyl cysteine instillation, whereas they were not affected by saline instillation.

Conclusion:

The fluorophotometric method may be used to evaluate the glycocalyx quantitatively in the ocular surface in vivo.

Blood group related antigens in ocular cicatricial pemphigoid

AIM

To study the MUC5AC and the blood group related antigen expression in ocular cicatricial pemphigoid (OCP) according to the distribution of Lewis and secretor phenotypes in OCP patients compared to normal subjects.

METHODS

Immunostaining was performed on conjunctival biopsy specimens from 22 consecutive patients suffering from OCP, using monoclonal antibodies (Mabs) directed against the peptidic core MUC5AC mucin (anti-M1/MUC5AC Mabs) and against the saccharide moieties (anti-blood group related antigens). These latter included anti-Le(a), anti-Le(b), anti-sialyl Le(a), and H type 2 Mabs, which immunoreact with Lewis positive and non-secretor (Le(a)), Lewis positive and secretor (Le(b)), Lewis positive (sialyl Le(a)), and secretor (H type 2) phenotypes respectively. Serological tests were also performed to confirm the phenotype of each patient. The immunohistopathological patterns and the distribution of Lewis and secretor phenotypes were compared with the results of a previous study in normal individuals.

RESULTS

(1) In OCP patients compared to the normal population, anti-M1 immunoreactivity of goblet cells was unchanged, whereas anti-Le(a), anti-Le(b), and anti-sialyl Le(a) immunoreactivities of epithelial and/or goblet cells were markedly decreased. (2) 41% of OCP patients had a non-secretor phenotype, which is statistically significantly more than the estimated incidence of the same phenotype in the French population (20%) (p approximately 0.04).

CONCLUSIONS

Mucins in OCP patients showed a decreased expression of blood group related antigens whereas the MUC5AC peptidic core detected by anti-M1 Mab remained unchanged. These results also seem to indicate that OCP may be associated with a non-secretor phenotype.

Correlation of goblet cell density and mucosal epithelial membrane mucin expression with rose bengal staining in patients with ocular irritation

PURPOSE

This study was designed to compare goblet cell densities and mucosal epithelial membrane mucin (MEM) expression in impression cytology specimens obtained from control subjects and patients with one of the following clinically defined diseases: aqueous tear deficiency (ATD) associated with Sjögren syndrome, ATD not associated with Sjögren syndrome, inflammatory Meibomian gland disease associated with rosacea, and Meibomian gland atrophy. These data were correlated with ocular surface rose Bengal staining scores, Schirmer scores, and HLA-DR antigen staining of conjunctival epithelial cells.

METHODS

Goblet cell density and MEM expression were studied by impression imprints with immunohistochemical staining using an anti-mucosal epithelial membrane mucin antibody in the temporal and inferior bulbar and inferior tarsal conjunctiva of study subjects.

RESULTS

Goblet cell density adjacent to the temporal limbus was significantly reduced at 3 mm posterior to the temporal limbus in both aqueous tear deficiency groups compared with the other groups and in patients with Sjögren syndrome compared with all other groups. In the inferior tarsus, goblet cell density was significantly reduced in patients with non-Sjögren syndrome ATD as compared with all other groups, except those with inflammatory Meibomian gland disease. Mucosal epithelial membrane mucin expression in the bulbar and tarsal conjunctiva was absent in a greater percentage of patients with Sjögren syndrome compared with all other groups. Total ocular surface rose Bengal staining scores were significantly higher in patients with Sjögren syndrome as compared with all other groups and in patients with non-Sjögren syndrome ATD as compared with control groups. Rose Bengal staining scores and Schirmer I test results (without anesthesia) were inversely correlated with bulbar, but not tarsal, conjunctival goblet cell densities, and with the absence of bulbar conjunctival MEM expression.

CONCLUSIONS

These results suggest that reduced goblet cell density and mucosal epithelial cell mucin expression could explain increased rose Bengal staining in patients with aqueous tear deficiency. In addition, MEM may be regarded as a marker for normal differentiation of ocular surface epithelia, with its absence signifying the development of squamous metaplasia.

Collagen gel-embedding culture of conjunctival epithelial cells

BACKGROUND

Collagen has effects on cell morphology, differentiation characteristics and function. Using collagen gel culture, several studies about cell differentiation were reported. In this study, the differentiation of rabbit conjunctival epithelial cells in a collagen gel-embedding culture system was investigated by electron microscope and lectin labeling.

METHODS

Rabbit bulbar conjunctival epithelial cells were cultured in type I collagen gel. After 1 and 2 weeks of culture, some of these cells were stained with PAS and seven kinds of lectins, and others were examined by transmission electron microscopy.

RESULTS

The conjunctival epithelial cells cultured within collagen gel formed stratified cell layers and globules with cavities. The inner layer cells facing the cavities showed PAS and lectin staining patterns similar to those of conjunctival goblet cells in vivo, whereas the staining patterns of the outer layer cells on the collagen matrices resembled the patterns of non-goblet epithelial cells. Microvilli on the surface of the innermost cells, basement membranes beneath the outermost cells, tight junctions, adherent junctions, interdigitating folds and desmosomes between cells were identified on electron microscopic examination.

CONCLUSION

These results indicate that cell junction structures of the conjunctival epithelial cells are well developed in collagen gel-embedding culture systems, and that the inner layer cells have carbohydrates similar to those of conjunctival goblet cells. Culture of conjunctival epithelial cells within collagen gel is a useful model for examining differentiation of these cells.

Corneal and ocular surface histochemistry

In summary, this review has provided information concerning the application of histochemical and cytochemical procedures used to detail the normal versus pathological cornea and ocular surface. Specifically, histochemical analysis has been used to study protein and peptide degradation in cornea, to analyze stromal non-collagenous and collagenous fibers and associated extracellular matrix. Cytochemistry of the ocular surface has been used to detail the morphology of corneal and conjunctival mucin. Use of small cationic probes as well as lectin-gold binding was advantageous to quantitatively demonstrate that ocular mucin contains sialylated residues and that the number of these residues significantly changes (increases) with age. These data are important in that the degree of sialylation has been shown to correlate with the ability of bacterial organisms to adhere to and infect the immature in contrast to the mature corneal surface. The use of lectin analysis of diseased ocular tissue also has shown that there are specific alterations in glycoconjugates which occur in the diseased versus normal human cornea. Wound healing in cornea is an important problem which has been studied at length using combined histochemical and biochemical approaches. Results support the hypothesis that apical cell surfaces of the leading edge of a migrating sheet differ from those of the normal epithelium. During wound healing, alpha 6 integrin expression by corneal epithelial cells has been demonstrated, but another protein, syndecan was only seen in non-migrating epithelium which had restratified. The association of immunoglobulins with the ocular surface epithelium of the cornea, their change with age and kinetics of appearance also has been demonstrated using a cytochemical approach. Histochemical procedures have been used to localize Class I and Class II molecules in cornea and conjunctiva. Class II antigen expression has been shown to be absent on corneal endothelium, but it can be induced by treatment with IFN-gamma. These data are of importance in corneal pathology such as that resulting in rejection of corneal transplants. Langerhans cells (Class II, Ia positive) also are not found in normal central cornea. They are localized in the peripheral cornea and are stained histochemically by ADPase, ATPase and by specific anti-Ia and other antisera. Increased numbers of LC have been demonstrated in cornea following various stimuli and in diseases of the cornea including both bacterial and viral induced keratitis.

The normal human tear glycoprotein profile detected with lectin probes

Tear samples were collected from 46 healthy volunteers evenly distributed according to sex and age (mean age 43.5 years). Samples were denatured in a Tris-HCl sample buffer containing 2-mercaptoethanol and SDS, and applied to a gradient SDS-polyacrylamide gel for electrophoresis. The proteinaceous material was transferred to nitrocellulose by a semi-dry blotting technique, and the glycoprotein content subsequently visualized by incubation with four lectins (WGA, PHA, PSA and SBA) and staining with avidin horseradish-peroxidase. Glycoprotein bands were generally found to be significantly less frequent in persons under the age of 30 years. Apart from this the technique gave a uniform picture of the glycoprotein profile, with only modest differences according to age and/or sex. The technique may therefore be suitable for the detection of differences in the glycoprotein composition indicative of disease.

Ultrastructural localization of lectin-binding sites on the surface of the guinea pig conjunctival epithelium

The cell-surface binding sites of two lectins, concanavalin A (Con A) and wheat-germ agglutinin (WGA) in the guinea pig conjunctiva were investigated at the ultrastructural level by means of pre-embedding staining of the tissue with lectin-colloidal gold complexes. Wheat-germ agglutinin, which recognizes N-acetylglucosamine and sialic acid residues, showed prominent and fairly uniform binding to the microvilli. The binding was markedly increased in the vicinity of the goblet cells, indicating that the same carbohydrate ligands were also present in the mucus. In contrast, no binding of concanavalin A, which recognizes mannose and N-glucose, was observed. The results suggest the presence of sialic acid and galactose as the constituent carbohydrates of glycoconjugates in the surface membrane of conjunctival epithelial cells as well as in the mucus produced by the goblet cells.

Lectin-binding sites in the anterior segment of the human eye

The anterior segment of the human eye was screened for differences in the lectin-binding patterns of Con A, PNA, GS-I, WGA, SBA, DBA, and UEA-I to enable cell typing for cell-culture purposes. An immunohistochemical technique combining an indirect antibody-lectin method with the avidin-biotin system was used. Con A and WGA were bound by all cells except the conjunctival goblet cells. UEA-I was exclusively bound by both vascular endothelial cells and some corneal and conjunctival epithelial cells. The binding of GS-I, PNA, SBA, and DBA showed an uneven pattern and differed among the cases investigated. The reasons for these differences are not clear. Our results indicate that the usefulness of lectins for cell-typing purposes is restricted and must be determined for every case.