CXCR4 and CXCR7 Mediate TFF3-Induced Cell Migration Independently From the ERK1/2 Signaling Pathway

PURPOSE

Trefoil factor family (TFF) peptides, and in particular TFF3, are characteristic secretory products of mucous epithelia that promote antiapoptosis, epithelial migration, restitution, and wound healing. For a long time, a receptor for TFF3 had not yet been identified. However, the chemokine receptor CXCR4 has been described as a low affinity receptor for TFF2. Additionally, CXCR7, which is able to heterodimerize with CXCR4, has also been discussed as a potential TFF2 receptor. Since there are distinct structural similarities between the three known TFF peptides, this study evaluated whether CXCR4 and CXCR7 may also act as putative TFF3 receptors.

METHODS

We evaluated the expression of both CXCR4 and CXCR7 in samples of human ocular surface tissues and cell lines, using RT-PCR, immunohistochemistry, and Western blot analysis. Furthermore, we studied possible binding interactions between TFF3 and the receptor proteins in an x-ray structure-based modeling system. Functional studies of TFF3-CXCR4/CXCR7 interaction were accomplished by cell culture-based migration assays, flow cytometry, and evaluation of activation of the mitogen-activated protein (MAP) kinase signaling cascade.

RESULTS

We detected both receptors at mRNA and protein level in all analyzed ocular surface tissues, and in lesser amount in ocular surface cell lines. X-ray structure-based modeling revealed CXCR4 and CXCR7 dimers as possible binding partners to TFF3. Cell culture-based assays revealed enhanced cell migration under TFF3 stimulation in a conjunctival epithelial cell line, which was completely suppressed by blocking CXCR4 and/or CXCR7. Flow cytometry showed increased proliferation rates after TFF3 treatment, while blocking both receptors had no effect on this increase. Trefoil factor family 3 also activated the MAP kinase signaling cascade independently from receptor activity.

CONCLUSIONS

Dimers CXCR4 and CXCR7 are involved in TFF3-dependent activation of cell migration, but not cell proliferation. The ERK1/2 pathway is activated in the process, but not influenced by CXCR4 or CXCR7. These results implicate a dependence of TFF3 activity as to cell migration on the chemokine receptors CXCR4 and CXCR7 at the ocular surface.

Isolation and Investigation of Presumptive Murine Lacrimal Gland Stem Cells

PURPOSE

Aqueous tear deficiency due to lacrimal gland insufficiency is one of the major causes of dry eye disease. In severe cases, such as Sjogren's syndrome, Stevens-Johnson syndrome, or ocular cicatricial pemphigoid, therapy with artificial tears is often insufficient to relieve severe discomfort, prevent progressive ocular surface disease, or enable visual rehabilitation by corneal transplantation. Cell or organ generation from stem cells, resulting in tear-like secretion, presents an option as a suitable alternative treatment. To obtain deeper insights into lacrimal gland stem cells we analyzed murine lacrimal glands for markers of pluripotency, self-renewal, and differentiation.

METHODS

A special, patented technique with mechanical and enzymatic digestion was used to generate high numbers of cells in vitro from murine lacrimal glands. These presumptive "murine lacrimal gland stem cells" ("mLGSCs") can be propagated as monolayer cultures over multiple passages. By means of RT-PCR, Western blot, and immunohistochemistry, markers of pluripotency and differentiation were demonstrated. Hanging drop culture was used to build organoid bodies from mLGSCs to investigate their spontaneous differentiation in three-dimensional culture with histology, immunohistochemistry, and transmission electron microscopy methods.

RESULTS

Isolated mLGSCs were cultured over more than 65 passages. Murine lacrimal gland stem cells expressed markers of pluripotency such as Nanog, Sox2, Kruppel-like factor 4 (Klf4), as well as early-lineage markers of all three germ layers. Three-dimensional culture of these cells revealed their ability to differentiate into various cell types.

CONCLUSIONS

Our results suggest that mLGSCs were isolated and cultured successfully. These cells have the ability to differentiate into all three germ layers. The results provide further insights into lacrimal gland stem cell physiology for engineering of a lacrimal gland construct to treat severe cases of tear deficiency in the future.

Morphological alterations within the peripheral fixation of the iris dilator muscle in eyes with pigmentary glaucoma

PURPOSE

To analyze the peripheral fixation of the iris dilator muscle in normal eyes and in eyes with pigmentary glaucoma (PG).

METHODS

Using 63 control eyes (age 18 months-99 years), the peripheral iris dilator was investigated by light microscopy, immunohistochemistry, and electron microscopy. Development was studied using 18 differently aged fetal eyes stained immunohistochemically against α-smooth muscle (SM) actin. The peripheral iris dilator muscle in PG was analyzed using semithin and ultrathin sections of six glutaraldehyde-fixed eyes from three donors aged 38, 62, and 74 years.

RESULTS

In normal eyes, the peripheral end of the iris dilator muscle is arranged in a sphincter-like manner. Arcade-shaped tendinous connections associated with myofibroblasts (iridial strands) anchor the iris dilator within the elastic-fibromuscular ciliary meshwork that also serves as fixation area for the elastic tendons of the inner ciliary muscle portions. The iridial strands are innervated and can adapt their length during accommodation. The PG eyes show incomplete circular bundles and iridial strands that are mainly anchored to the iris stroma and the flexible uveal parts of the trabecular meshwork.

CONCLUSIONS

The normal anchorage of the peripheral iris dilator and its presumably neuronally regulated length adaptation stabilize the peripheral iris during accommodation. Insufficient fixation in PG could promote posterior bowing of the iris with rubbing against the zonular fibers and pigment liberation from the iris pigmented epithelium.

Insulin-like factor 3 promotes wound healing at the ocular surface

Tear fluid is known to contain many different hormones with relevance for ocular surface homeostasis. We studied the presence and functional role of insulin-like factor 3 (INSL3) and its cognate receptor RXFP2 (relaxin/insulin-like family peptide receptor 2) at the ocular surface and in tears. Expression of human INSL3 and RXFP2 was determined in tissues of the ocular surface and lacrimal apparatus; in human corneal (HCE), conjunctival (HCjE), and sebaceous (SC) epithelial cell lines; and in human tears by RT-PCR and ELISA. We investigated effects of human recombinant INSL3 (hrINSL3) on cell proliferation and cell migration and the influence of hrINSL3 on the expression of MMP2, -9, and -13 and TIMP1 and -2 was quantified by real-time PCR and ELISA in HCE, HCjE, and SC cells. We used a C57BL/6 mouse corneal defect model to elucidate the effect of topical application of hrINSL3 on corneal wound healing. INSL3 and RXFP2 transcripts and INSL3 protein were detected in all tissues and cell lines investigated. Significantly higher concentrations of INSL3 were detected in tears from male vs. female volunteers. Stimulation of HCE, HCjE, and SC with hrINSL3 significantly increased cell proliferation in HCjE and SC and migration of HCjE. Treatment with hrINSL3 for 24 hours regulated MMP2, TIMP1, and TIMP2 expression. The local application of hrINSL3 onto denuded corneal surface resulted in significantly accelerated corneal wound healing in mice. These findings suggest a novel and gender-specific role for INSL3 and cognate receptor RXFP2 signaling in ocular surface homeostasis and determined a novel role for hrINSL3 in corneal wound healing.

Relaxin 2 is functional at the ocular surface and promotes corneal wound healing

PURPOSE

We aimed to determine if the insulin-like peptide hormone relaxin 2 (RLN2) is expressed at the ocular surface and in tears and if RLN2 influences wound healing at the ocular surface, which is associated with extracellular matrix (ECM) remodeling.

METHODS

We analyzed transcript levels of human RLN2 and its cognate relaxin-like receptors RXFP1 and RXFP2 in tissues of the ocular surface, lacrimal apparatus, and human corneal (HCE), conjunctival (HCjE) and sebaceous (SC) cell lines. We analyzed effects of human RLN2 on cell proliferation and migration and quantified mRNA expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in HCE, HCjE, and SC. Using an alkali-induced corneal wounding model, we analyzed the wound healing rate in C57BL/6 mice eyes after topically applied RLN2.

RESULTS

The presence of RLN2, RXFP1, and RXFP2 transcripts was detected in lacrimal gland, eyelid, conjunctiva, cornea, primary corneal fibroblasts, nasolacrimal ducts, and all three cell lines. ELISA revealed RLN2 protein in all ocular surface tissues analyzed and in human tears. Stimulation of HCE, HCjE, and SC with RLN2 significantly increased cell proliferation and migration. Relative mRNA expression levels of MMP2, MMP9, TIMP1, and TIMP2 were significantly influenced by RLN2 in all three cell lines at different time points studied. The local application of RLN2 onto denuded corneal surface resulted in significantly elevated corneal wound healing.

CONCLUSIONS

Our data support a novel role for the RLN2 ligand-receptor system at the ocular surface and in the lacrimal apparatus as a potential future therapeutic during wound healing at the ocular surface.

Antimicrobial peptides as a major part of the innate immune defense at the ocular surface

The ocular surface is in constant contact with the environment (e.g. when using one's fingers to insert a contact lens) and thus also with diverse bacteria, bacterial components and their pathogen associated molecules. Dysfunctions of the tear film structure or decreased moistening of the ocular surface, as in dry eye (keratoconjunctivitis sicca) for example, often lead to inflammatory and infectious complications resulting in severe functional disorders, particularly concerning the cornea. Besides different protective antimicrobial substances in the tear fluid (mucins, lysozyme, lactoferrin), the epithelia of cornea and conjunctiva can also protect themselves from microbial invasion by producing an arsenal of antimicrobial peptides (AMPs). A number of different studies have revealed that small cationic AMPs, which display antimicrobial activity against a broad spectrum of microorganisms, are a major component of the innate immune system at the human ocular surface. Furthermore, several AMPs modulate cellular activation processes like migration, proliferation, chemotaxis and cytokine production, and in this way also affect the adaptive immune system. In this article, we have summarized current knowledge of the mechanisms of activity and functional roles of AMPs, with a focus on potential multifunctional roles of human beta-defensins and S100 peptide psoriasin (S100A7) at the ocular surface.

Cationic amino acid transporters and beta-defensins in dry eye syndrome

Several diseases concomitant with L-arginine deficiency (diabetes, chronic kidney failure, psoriasis) are significantly associated with dry eye syndrome. One important factor that has so far been neglected is the y(+) transporter. In humans, y(+) accounts for nearly 80% of arginine transport, exclusively carrying the cationic amino acids L-arginine, L-lysine and L-ornithine. y(+) is represented by CAT(cationic amino acid transporter) proteins. L-arginine is a precursor of the moisturizer urea, which has been used in the treatment of dry skin diseases. Although urea has also been shown to be part of the tear film, little attention has been paid to it in this role. Moreover, L-arginine and L-lysine are major components contributing to synthesis of the antimicrobially active beta-defensins induced under dry eye conditions. The first results have demonstrated that transport of L-arginine and L-lysine into epithelial cells is limited by the y(+) transporter at the ocular surface.

Trefoil factor 3 is induced during degenerative and inflammatory joint disease, activates matrix metalloproteinases, and enhances apoptosis of articular cartilage chondrocytes

OBJECTIVE

Trefoil factor 3 (TFF3, also known as intestinal trefoil factor) is a member of a family of protease-resistant peptides containing a highly conserved motif with 6 cysteine residues. Recent studies have shown that TFF3 is expressed in injured cornea, where it plays a role in corneal wound healing, but not in healthy cornea. Since cartilage and cornea have similar matrix properties, we undertook the present study to investigate whether TFF3 could induce anabolic functions in diseased articular cartilage.

METHODS

We used reverse transcriptase-polymerase chain reaction, Western blot analysis, and immunohistochemistry to measure the expression of TFF3 in healthy articular cartilage, osteoarthritis (OA)-affected articular cartilage, and septic arthritis-affected articular cartilage and to assess the effects of cytokines, bacterial products, and bacterial supernatants on TFF3 production. The effects of TFF3 on matrix metalloproteinase (MMP) production were measured by enzyme-linked immunosorbent assay, and effects on chondrocyte apoptosis were studied by caspase assay and annexin V assay.

RESULTS

Trefoil factors were not expressed in healthy human articular cartilage, but expression of TFF3 was highly up-regulated in the cartilage of patients with OA. These findings were confirmed in animal models of OA and septic arthritis, as well as in tumor necrosis factor alpha- and interleukin-1beta-treated primary human articular chondrocytes, revealing induction of Tff3/TFF3 under inflammatory conditions. Application of the recombinant TFF3 protein to cultured chondrocytes resulted in increased production of cartilage-degrading MMPs and increased chondrocyte apoptosis.

CONCLUSION

In this study using articular cartilage as a model, we demonstrated that TFF3 supports catabolic functions in diseased articular cartilage. These findings widen our knowledge of the functional spectrum of TFF peptides and demonstrate that TFF3 is a multifunctional trefoil factor with the ability to link inflammation with tissue remodeling processes in articular cartilage. Moreover, our data suggest that TFF3 is a factor in the pathogenesis of OA and septic arthritis.

Functional relationship between cationic amino acid transporters and beta-defensins: implications for dry skin diseases and the dry eye

The ocular surface, constantly exposed to environmental pathogens, is particularly vulnerable to infection. Hence an advanced immune defence system is essential to protect the eye from microbial attack. Antimicrobial peptides, such as beta-defensins, are essential components of the innate immune system and are the first line of defence against invaders of the eye. High concentrations of L-arginine and L-lysine are necessary for the expression of beta-defensins. These are supplied by epithelial cells in inflammatory processes. The limiting factor for initiation of beta-defensin production is the transport of L-arginine and L-lysine into the cell. This transport is performed to 80% by only one transporter system in the human, the y(+)-transporter. This group of proteins exclusively transports the cationic amino acids L-arginine, L-lysine and L-ornithine and is also known under the term cationic amino acid transporter proteins (CAT-proteins). Various infections associated with L-arginine deficiency (for example psoriasis, keratoconjuctivitis sicca) are also associated with an increase in beta-defensin production. For the first time, preliminary work has shown the expression of human CATs in ocular surface epithelia and tissues of the lacrimal apparatus indicating their relevance for diseases of the ocular surface. In this review, we summarize current knowledge on the human CATs that appear to be integrated in causal regulation cascades of beta-defensins, thereby offering novel concepts for therapeutic perspectives.

Somatostatin actions via somatostatin receptors on the ocular surface are modulated by inflammatory processes

Recent investigations support the presence of human somatostatin (SS) in the excretory system of the human lacrimal gland. To get deeper insights into a possible role of SS at the ocular surface and in the lacrimal apparatus, we investigated the distribution pattern of SS and its receptors 1-5 (SSTR1-5) by means of RT-PCR, real-time RT-PCR, Western blot and immunodot blot analysis as well as immunohistochemistry in lacrimal gland, tear fluid, conjunctiva, cornea, nasolacrimal duct epithelium, and conjunctival (HCjE) and corneal (HCE) epithelial cell lines. Cell culture experiments with HCjE and HCE were performed to analyze a possible impact of SS and inflammatory mediators on the regulation of SSTR. The results confirmed the presence of SS in lacrimal gland and tear fluid, whereas it was absent at the protein level in all other tissues and cell lines investigated. Expression of SSTR1, -2, and -5 was detectable in lacrimal gland, conjunctiva, cornea, and nasolacrimal ducts. HCjE expressed only hSSTR1 and -2, and HCE revealed only SSTR2. SSTR3 and -4 were not detected in any of the analyzed samples or cell lines. In vitro on cultured immortalized HCjE cells SS leads to a concentration-dependent down-regulation of SSTR1 mRNA but does not affect SSTR2 mRNA expression. Relative expression of SSTR1 and -2 is differentially modulated by proinflammatory cytokines and bacterial components, suggesting that the expression of both receptors is immunomodulated. Our data support an autocrine and paracrine role of SS in the lacrimal system and at the ocular surface and implicate a role of SS in corneal immunology.

Intestinal trefoil factor/TFF3 promotes re-epithelialization of corneal wounds

Disorders of wound healing characterized by impaired or delayed re-epithelialization are a serious medical problem. These conditions affect many tissues, are painful, and are difficult to treat. In this study using cornea as a model, we demonstrate the importance of trefoil factor 3 (TFF3, also known as intestinal trefoil factor) in re-epithelialization of wounds. In two different models of corneal wound healing, alkali- and laser-induced corneal wounding, we analyzed the wound healing process in in vivo as well as in combined in vivo/in vitro model in wild type (Tff3(+)(/)(+)) and Tff3-deficient (Tff3(-)(/)(-)) mice. Furthermore, we topically applied different concentrations of recombinant human TFF3 (rTFF3) peptide on the wounded cornea to determine the efficacy of rTFF3 on corneal wound healing. We found that Tff3 peptide is not expressed in intact corneal epithelium, but its expression is extensively up-regulated after epithelial injury. Re-epithelialization of corneal wounds in Tff3(-/-) mice is significantly prolonged in comparison to Tff3(+/+) mice. In addition, exogenous application of rTFF3 to the alkali-induced corneal wounds accelerates significantly in in vivo and in combined in vivo/in vitro model wound healing in Tff3(+/+) and Tff3(-/-) mice. These findings reveal a pivotal role for Tff3 in corneal wound healing mechanism and have broad implications for developing novel therapeutic strategies for treating nonhealing wounds.

Detection and localization of the hydrophobic surfactant proteins B and C in human tear fluid and the human lacrimal system

PURPOSE

To evaluate the expression and presence of the surfactant proteins (SP) B and C in the lacrimal apparatus at the ocular surface and in tear fluid.

METHODS

Expression of SP-B and SP-C was analyzed by RT-PCR in healthy lacrimal gland, conjunctiva, meibomian gland, accessory lacrimal glands, cornea, and nasolacrimal ducts. The deposition of the hydrophobic proteins SP-B and SP-C was determined by Western blot and immunohistochemistry in healthy tissues, tear fluid, and aqueous humor.

RESULTS

The presence of both SP-B and SP-C on mRNA and protein level was evidenced in healthy human lacrimal gland, conjunctiva, cornea, and nasolacrimal ducts. Moreover, both proteins were present in tear fluid but were absent in aqueous humor. Immunohistochemical investigations revealed production of both peptides by acinar epithelial cells of the lacrimal gland and additionally by accessory lacrimal glands of the eyelid as well as epithelial cells of the conjunctiva and nasolacrimal ducts. Immunohistochemically, healthy cornea and goblet cells revealed no reactivity.

CONCLUSIONS

Besides the recently detected surfactant-associated proteins SP-A and SP-D, our results show that SP-B and SP-C are also peptides of the tear film, the ocular surface, and the lacrimal apparatus. Based on the current knowledge of lowering surface tension in alveolar lung cells, a similar effect of SP-B and SP-C may be assumed concerning the tear film.

Detection of surfactant proteins A and D in human tear fluid and the human lacrimal system

PURPOSE

To evaluate the expression and presence of surfactant protein (SP) A and SP-D in the lacrimal apparatus, at the ocular surface, and in tears in healthy and pathologic states.

METHODS

Expression of mRNA for SP-A and SP-D was analyzed by RT-PCR in healthy lacrimal gland, conjunctiva, cornea, and nasolacrimal ducts as well as in a spontaneously immortalized conjunctival epithelial cell line (HCjE; IOBA-NHC) and a SV40-transfected cornea epithelial cell line (HCE). Deposition of SP-A and SP-D was determined by Western blot, dot blot, and immunohistochemistry in healthy tissues, in tears, aqueous humor, and in sections of different corneal abnormalities (keratoconus, herpetic keratitis, and Staphylococcus aureus-based ulceration). Cell lines were stimulated with different cytokines and bacterial components and were analyzed for the production of SP-A and SP-D by immunohistochemistry.

RESULTS

The presence of SP-A and SP-D on mRNA and protein levels was evidenced in healthy lacrimal gland, conjunctiva, cornea, and nasolacrimal duct samples. Moreover, both proteins were present in tears but were absent in aqueous humor. Immunohistochemistry revealed the production of both peptides by acinar epithelial cells of the lacrimal gland and epithelial cells of the conjunctiva and nasolacrimal ducts, whereas goblet cells revealed no reactivity. Healthy cornea revealed weak reactivity on epithelial surface cells only. In contrast, SP-A and SP-D revealed strong reactivity in patients with herpetic keratitis and corneal ulceration surrounding lesions and in several immigrated defense cells. Reactivity in corneal epithelium and endothelium was also seen in patients with keratoconus. Cell culture experiments revealed that SP-A and SP-D are produced by both epithelial cell lines without and after stimulation with cytokines and bacterial components.

CONCLUSIONS

These results show that SP-A, in addition to SP-D, is a peptide of the tear film. Based on the known direct and indirect antimicrobial effects of collectins, the surfactant-associated proteins A and D seem to be involved in several ocular surface diseases.

Drainage of tears: impact on the ocular surface and lacrimal system

The human efferent tear ducts are part of the lacrimal system. Because little knowledge exists concerning the physiology of the nasolacrimal system, and hence its patho- physiology, the nasolacrimal system has received almost no consideration as a possible factor in dry eye. The human nasolacrimal ducts consist of the upper and the lower lacrimal canaliculus, the lacrimal sac, and the nasolacrimal duct. As a draining and secretory system, the efferent tear ducts play a role in tear transport and nonspecific immune defense. Moreover, components of tear fluid are absorbed in the nasolacrimal passage and are transported into a surrounding vascular system. This system is similar to a cavernous body that is subject to autonomic control and regulates tear outflow. Tear duct-associated lymphoid tissue (TALT) is present in the efferent tear ducts, displaying the cytomorphological and immunophenotypic features of mucosa-associated lymphoid tissue (MALT). Under normal conditions, tear fluid components are constantly absorbed into the blood vessels of the surrounding cavernous body. These vessels are connected to the blood vessels of the outer eye and could act as a feedback signal for tear fluid production, which ceases if these tear components are not absorbed. In this way, dry eye could be initiated. Defective stimulation of TALT could result in abnormal immune deviation at the ocular surface, leading to an autoimmunological response that causes dry eye pathology.

MUC16 in the lacrimal apparatus

The aim of the present study was to determine the possible expression of the mucin MUC16 in the lacrimal apparatus. Expression and distribution of MUC16 in lacrimal gland, accessory lacrimal glands, and nasolacrimal ducts was monitored by RT-PCR and immunohistochemistry. MUC16 was expressed and detected in all tissues investigated. Comparable to conjunctiva and cornea it was membrane-anchored in accessory lacrimal glands whereas in lacrimal gland acinar cells and columnar cells of the nasolacrimal ducts it was stored in intracytoplasmic vesicles without membrane-association. Subepithelial serous glands of the nasolacrimal ducts revealed staining of the secretion product. Intracelluar production of MUC16 is present in lacrimal gland and epithelial cells of the nasolacrimal ducts but it is not clear whether this MUC16 is secreted. MUC16 seems to be shedded or secreted from the epithelial surface of subepithelial serous glands of the nasolacrimal ducts. Our results show that MUC16 is present in the whole lacrimal apparatus. Its distribution pattern suggests different physiological functions with regard to tear film physiology and tear outflow. Moreover, the results demonstrate the existence of so far not recognized qualitative differences in the secretion product of main lacrimal gland and accessory lacrimal glands (glands of Krause).

Antimicrobial defence mechanisms of the human parotid duct

The parotid duct transports saliva from the gland into the oral cavity. However, its immune response properties, along with the secretion and moistening principles of the duct, have not yet been fully investigated. These properties may play an important role in protecting the parotid gland from infection and also prevent development of sialodocholithiasis, as the parotid duct -- in contrast to the submandibular salivary duct -- is often free of duct concrements. Up to now, only the parotid gland has been investigated, without regard to its duct. The present study analyses the structures of the parotid duct in their relations to antimicrobial defence mechanisms and rheological properties. Investigations were performed on 23 parotid ducts using histological, histochemical and immunohistochemical methods. Epithelial and goblet cells of the parotid duct synthesize a complex mucous layer that covers the epithelium. The viscosity is influenced by secreted mucins and TFF peptides. This layer contains carbohydrates including N-acetyl-glucosamine, N-acetyl-galactosamine, galactose, mannose, fucose and sialic acids. The lamina propria contains granulocytes, T lymphocytes and macrophages. IgA, produced by plasma cells in the subepithelial layer, is frequently integrated in the secretory product. Synthesized mucins, TFF peptides, carbohydrates and immunoglobulins form a complex layer that can be expected to prohibit infection and enables salivary flow. Our study demonstrates that the steady secretion of the parotid gland, together with the ductal cellular and biochemical immune protection system, is likely to thwart ascending infections in the parotid duct and gland.

Mucins and TFF peptides of the tear film and lacrimal apparatus

The three-dimensional organization of the tear film, which is produced and drained by the different structures of the ocular adnexa, is essential for maintainance and protection of the ocular surface. This is facilitated by a class of large, highly glycosylated, hydrophilic glycoproteins, the mucins, which are usually expressed in association with a class of peptides having a well-defined, structurally conserved trefoil domain, the mammalian trefoil factor family (TFF) peptides. In this review, the latest information regarding mucin and TFF peptide function and regulation in the human lacrimal system, the tear film and the ocular surface is summarized with regard to mucous epithelia integrity, rheological and antimicrobial properties of the tear film and tear outflow, age-related changes and certain disease states such as dry eye, dacryostenosis and dacryolith formation.

[Ultrastructural analysis of secretion-transport through the parotid duct]

BACKGROUND

Mechanisms of secretion transport through the parotid duct (stenon's duct) and their influence on diseases of the parotid gland have not been investigated sufficiently until today.

METHODS

According to this background we performed histologic and scanning electron microscopical investigations of 23 parotid ducts in order to investigate the arrangement of fibrillar structures of the duct as well as get deeper insights into the physiology of secretion transport mechanisms.

RESULTS

The subepithelial soft tissue of the parotid duct could be divided into two layers. The inner layer measured about 100-200 microm and consisted of collagen and elastic fibres running in a spiral arrangement. The outer layer varied in its thickness and was composed of collageous fibres, which were mostly arranged longitudinally.

CONCLUSIONS

The arrangement of collagen fibrils in the wall of the parotid duct seems to influence secretion transport. Due to the spiral organization of collagen fibrils, distension of the duct is likely to be associated with a "wring-out" mechanism leading to unidirectional transport of saliva into the oral cavity. A muscular sphincter at the outlet of the parotid duct did not exist. The duct pierced the buccinatory muscle. Here, it was surrounded by sceletal muscle fibres that lead to a functional closure during contraction. Our results indicate that an active transport of saliva through the parotid duct--as so far assumed--is unlikely.

TFF peptides and mucins are major components of dacryoliths

PURPOSE

The study was performed to determine whether trefoil factor peptides (TFF) and/or mucins are components of dacryoliths and to gain further insight into dacryolith composition and formation.

METHODS

Twenty dacryoliths found in lacrimal surgery in patients suffering from primary acquired nasolacrimal duct obstruction were analyzed for the presence of TFF peptides (TFF1, 2, 3), mucins (MUC1, 2, 3, 4, 5AC, 5B, 6, 7, 8), defense cells (T- and B lymphocytes, macrophages, neutrophils), and antimicrobial substances (alpha defensins 1-3, secretory phospholipase A(2)) by means of light microscopy, histochemistry, immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR.

RESULTS

All dacryoliths except one revealed clear immunoreactivity for all three TFF peptides. The immunohistochemical distribution of mucins was inhomogeneous throughout the different dacryoliths. However, in some dacryoliths all mucins investigated were detected. MUC8 showed reactivity in 14 out of 15 dacryoliths analyzed by immunohistochemistry. Most dacryoliths contained alpha defensins 1-3 as the secretory product of neutrophils. T and B lymphocytes, macrophages and secretory phospholipase A(2) were only present in single dacryoliths. Quantification of TFF peptide expression supported the immunohistochemical finding that all three TFF peptides are augmented in dacryoliths.

CONCLUSIONS

Dacryoliths consist partly of secreted mucins comparable with the mucin spectrum of the epithelium of healthy nasolacrimal ducts. Beside TFF1 and TFF3, both of which are produced under healthy circumstances, TFF2 is additionally induced and secreted in cases of dacryolithiasis. All three TFF peptides appear to be augmented in dacryoliths. With regard to their rheologic properties, TFF peptides may play a functional role in dacryolith formation. However, our results raise the question of whether TFF peptides per se influence dacryolith formation or whether their secretion, as in secretion of mucins and alpha defensins 1-3, is merely a secondary phenomenon.

Prognostic value of mucins in the classification of ampullary carcinomas

The ampulla of Vater is of high clinical relevance with regard to influx of chyme, ascending inflammation, intubation during diagnostic and therapeutic endoscopic investigation, therapeutic papillotomy, and especially to malignant transformation. Little is known about the distribution of mucins in the ampulla. In this study, we have investigated the mucin distribution in the normal ampulla of Vater and compared it to duodenal mucosa and Brunner glands. Expression of mucins in the ampulla of Vater and duodenum was monitored by reverse transcription-polymerase chain reaction and localization of the products by immunohistochemistry. The samples investigated originated from 30 autopsy cases. Mucins MUC1, MUC3, MUC4, MUC5AC, MUC5B, MUC6, MUC7, and MUC8 were expressed in the ampulla of Vater. Immunohistochemistry revealed production of MUC4, MUC5AC, MUC5B, and MUC6. The mucin composition varied in comparison with the duodenum referring to MUC2, MUC7, and MUC8. Detected mucins contribute to innate immunity, epithelial restitution, and protection against the aggressive secretions of the liver, gall bladder, and pancreas. By cross-linking, they influence the rheological properties of the secretions in the ampulla and facilitate unidirectional flow into the duodenum. Knowledge of their pattern of expression has prognostic value with regard to the detection of malignancy. The observed differences in the mucin distribution between the duodenum and the ampulla of Vater support the use of MUC2, MUC7, and MUC8 as useful tool in the classification of ampullary carcinomas.

Expression and regulation of human β-defensin-2 in osteoarthritic cartilage

Defensins are antibiotic peptides that are involved in host defence at epithelial and mesenchymal surfaces. Previous studies have shown the induction of human beta-defensin-3 (HBD-3) in osteoarthritic joints, suggesting that these molecules have functions in addition to their ability to kill microbes. The aim of this study was to investigate the production of a further human beta-defensin, named HBD-2, in osteoarthritis (OA) and to determine its regulation by inflammatory cytokines. Healthy and osteoarthritic cartilage was assessed for HBD-2 expression by RT-PCR, immunohistochemistry, and ELISA. C28/I2 chondrocytes, primary chondrocytes, and cartilage explants were cultured for in vitro studies. After 24 h of stimulation with tumour necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) or IL-6, real-time RT-PCR and ELISA experiments were performed to evaluate the effect of these cytokines on the production of HBD-2. In contrast to healthy cartilage, HBD-2 expression was identified in most of the OA samples examined (eight of ten). Cytokines that are potentially involved in the pathogenesis of OA, namely TNF-alpha, IL-1, and IL-6, were transcriptional inducers of HBD-2 in cultured chondrocytes and cartilage explants in vitro, as measured by real-time RT-PCR and ELISA. These results illustrate the induction of HBD-2 in osteoarthritic cartilage and suggest that it is a further factor in the pathogenesis of OA. However, further studies are required to elucidate the role played by HBD-2 in osteoarthritic cartilage.

Differential Expression of Vascular Endothelial Growth Factor Implies the Limbal Origin of Pterygia

OBJECTIVE

To study the distribution of isoforms of vascular endothelial growth factor (VEGF) and its receptors VEGFR1 and VEGFR2 in pterygia and to compare it with that in healthy conjunctivas.

DESIGN

Nonrandomized comparative (cadaver controlled) study with histopathologic correlations.

METHODS

Tissue specimens from 75 patients treated for primary pterygia were analyzed using immunohistochemical studies as well as different molecular biological examinations. Healthy conjunctivas from 33 patients treated for cataracts as well as specimens from the conjunctiva, limbus, and lens of both eyes of 12 body donors served as controls.

TESTING

Surgical specimens of pterygia and normal conjunctiva specimens were processed with paraffin, sectioned, stained using specific antibodies against VEGF and its receptors, and examined by light microscopy. The other part of both groups of specimens as well as specimens from body donors were prepared and analyzed by means of reverse-transcription polymerase chain reaction (RT-PCR), real-time RT-PCR, enzyme-linked immunosorbent assay, and Western blots.

MAIN OUTCOME PARAMETERS

Vascular endothelial growth factor and VEGFR1 and VEGFR2 were analyzed to indentify the splice variants of VEGF as well as the distribution and amount of VEGF and both receptors in pterygia and the control tissues.

RESULTS

In analysis of specimens from pterygium patients as well as normal conjunctivas, VEGF121 and VEGF165 were identified as the only VEGF splice forms expressed. In addition to VEGF, VEGFR1 and VEGFR2 were detected in pterygia and conjunctivas and immunostained within the epithelium of pterygia and conjunctivas and on intrapterygial and intraconjunctival endothelial cells. Levels of VEGFR1 and VEGFR2 mRNA were lower in pterygia than in conjunctivas but similar in limbal and pterygium samples. Vascular endothelial growth factor levels were higher in pterygia than in conjunctivas, but were similar in the limbus and pterygia.

CONCLUSIONS

The results reveal similar behaviors in limbal and pterygium epithelial cells in terms of VEGF and VEGFR expression, with the presumption that pterygia arise from limbal epithelial cells and that human conjunctivas are not a suitable control for the analysis of pterygia. Moreover, the results suggest that VEGF might play an active role in the physiology of conjunctival epithelial cells.

Production of endogenous antibiotics in articular cartilage

OBJECTIVE

Defensins are broad-spectrum antimicrobial peptides that are components of innate immunity. To date, only epithelial surfaces and blood cells have been shown to produce these cationic peptides in bactericidal concentrations when challenged with microorganisms or inflammatory cytokines. Infections caused by gram-negative pathogens occur only infrequently in association with joint surgery. The present study was undertaken to investigate whether this may be explained by intraarticular production of gram-negative-specialized antimicrobial peptides.

METHODS

Healthy articular cartilage and cultured T/C-28a2 chondrocytes were assessed, by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry, for expression of various antimicrobial peptides. The expression of human beta-defensin 2 (HBD-2) was studied in cultured chondrocytes after exposure to bacterial supernatants and proinflammatory cytokines and was assayed by real-time RT-PCR and immunoblot analysis. A septic arthritis mouse model was used to investigate the regulation of the murine homolog of HBD-2 in articular cartilage after bacterial inoculation.

RESULTS

Healthy articular cartilage and T/C-28a2 chondrocytes were able to produce different antimicrobial peptides. After exposure to gram-negative bacteria and proinflammatory cytokines, expression of cartilage-derived HBD-2 strongly increased. Immunoblot analysis revealed up-regulation of the gram-negative-specialized HBD-2 in microbicidal doses. Immunohistochemistry analysis revealed induction of the murine homolog of HBD-2 in vivo after intraarticular injection of bacteria.

CONCLUSION

This study demonstrated a previously unrecognized function of human chondrocytes. In addition to its biomechanical properties, articular cartilage has the ability to produce antimicrobial substances when challenged with microorganisms. The expression of HBD-2 in microbicidal doses suggests that antimicrobial peptides may contribute to host defense mechanisms in articular joints.

VEGF expression in adult permanent thyroid cartilage: implications for lack of cartilage ossification

Vascular endothelial growth factor (VEGF) has been shown to play an important role during endochondral bone formation in hypertrophic cartilage remodeling, ossification, and angiogenesis, but it is not expressed in normal adult articular cartilage. Thyroid cartilage undergoes only partial ossification beginning at the age of about 20. Because it never completely ossifies, we investigated a possible role of VEGF and its receptors (VEGFRs) as well as the angiogenetic inhibitor endostatin in this permanent cartilage. In analysis of cartilage samples from all specimens evaluated, VEGF121 and VEGF165 were identified as the only VEGF splice forms expressed. In addition to VEGF, VEGFR-2 (kinase domain region/fetal liver kinase 1), but not VEGFR-1 (fms-like tyrosine kinase 1), was detectable by RT-PCR in cartilage. However, VEGFR-2 expression was only detectable up to the age of 19 years. Deposition of VEGF and VEGFR was confirmed by immunohistochemistry. VEGF concentrations measured by ELISA in thyroid cartilage increased with age in males but decreased in females. Endostatin concentrations measured by ELISA in thyroid cartilage were three times lower than in articular cartilage and showed no change with age, either in females or males. VEGF was immunostained within the intra- and pericellular matrices of some but not all chondrocytes. Thus, apart from its production in hypertrophic chondrocytes of growth plates, VEGF is also produced in single chondrocytes of thyroid cartilage. The data allow us to speculate that thyroid cartilage persists in an embryological state until it has reached its final size. After reaching its final size at the end of the second decade, VEGFR-2 is downregulated and ossification starts in the posterior part of the thyroid cartilage, proceeding ventrally. Both proteins, VEGF121 and VEGF165, should contribute to this process. VEGF concentration is high and changes in an age-related and sex-specific manner. Therefore, we postulate that VEGF is at least one of the key factors that is important for the lifelong ossification in thyroid cartilage.

TFF peptides in the human false vocal folds of the larynx

TFF peptides (formerly P domain peptides, trefoil factors) are typical secretory products of mucin-producing cells and are thought to influence the rheological properties of mucous gels. We investigated the localization of these peptides in the human false vocal folds of the larynx, also known as the ventricular folds or vestibular folds. An analysis of TFF peptide mRNA by RT-PCR and TFF protein by Western blot detected TFF1 and TFF3, but not TFF2. Immunohistochemistry revealed TFF1 to be associated with the secretory product of goblet cells and mucous parts of subepithelial seromucous glands. TFF3 occurred in columnar epithelial cells of the mucosa and in serous cells and excretory duct cells of seromucous glands. These peptides may play a role in the rheological function of mucus secreted onto the true vocal folds and are thus important constituents of vocal production.

The cavernous body of the human efferent tear ducts contributes to regulation of tear outflow

PURPOSE

To test the hypothesis that the surrounding vascular plexus of the lacrimal sac and the nasolacrimal duct contributes to the regulation of tear outflow.

METHODS

Experiments in 30 probands aged between 15 and 37 years were performed in both nasolacrimal systems of each subject by observing with an endoscope the transit time of an applied tear drop containing fluorescein dye until its entry into the inferior meatus of the nose. Four different experiments were performed to determine the median transit time under normal conditions and the influence on transit time of a decongestant drug, a foreign body on the ocular surface, and a decongestant drug applied together with a foreign body on the ocular surface. Comparisons were made between the right and left nasolacrimal system, in males and females, eyeglass wearers and non-eyeglass wearers, and the different experiments and the results statistically analyzed.

RESULTS

The tear transit time was independent of side (right or left), gender, or eyeglass wear. It showed great individual variability. Application of a decongestant drug or placement of a foreign body on the ocular surface both prolonged the dye transit time significantly. Application of a decongestant drug simultaneously with placement of a foreign body shortened the dye transit time significantly compared with the effect of the decongestant drug alone but revealed no significant difference compared with application of a foreign body alone.

CONCLUSIONS

The cavernous body of the lacrimal sac and nasolacrimal duct plays an important role in the physiology of tear outflow regulation. It is subject to autonomic control and is integrated into a complex neuronal reflex feedback mechanism starting with the dense innervation of the cornea. Moreover, its function can be pharmacologically influenced.

Characterization of mucins in human lacrimal sac and nasolacrimal duct

PURPOSE

Mucins are polymers that may reduce drag and enhance tear outflow. Mucin expression and distribution in human efferent tear ducts were tested in the physiological state, and potential differences in the expression pattern were investigated in the presence of primary acquired dacryostenosis (PANDO).

METHODS

Expression of mucins in human lacrimal sac and nasolacrimal ducts was monitored by reverse transcription-polymerase chain reaction analysis. The presence and distribution of MUC1, -2, -4, -5AC, -5B, -6, and -7 in epithelia of the efferent tear duct passage are assessed with antisera to mucin peptide cores. Twenty normal tissues from cadavers and surgical specimens from 20 patients with PANDO were tested.

RESULTS

mRNAs for all mucins investigated were detected in healthy human lacrimal sacs and nasolacrimal ducts. MUC6 mRNA was detected in only about half of the investigated samples. A reduced level of MUC2, -5AC, and -5B mRNAs was observed in PANDO. Immunohistochemistry revealed MUC2 in goblet cells and single epithelial cells. Both MUC5AC and -5B were detected in goblet cells forming intraepithelial mucous glands. MUC7 was present only in columnar epithelial cells of the efferent tear duct system. No immunoreactivity was observed with antibodies against MUC1, -4, and -6 peptide cores.

CONCLUSIONS

Human efferent tear ducts express and produce a broad spectrum of mucins that is partly comparable with that in the conjunctiva and the salivary glands. The mucin diversity of the efferent tear ducts could enhance tear transport and antimicrobial defense. Reduced levels of mucin mRNA in a nonfunctioning though patent segment of the lacrimal passage, which is associated with epiphora, suggests that mucins ease tear flow through the efferent tear ducts.

Region-specific immunological response of the different laryngeal compartments: significance of larynx-associated lymphoid tissue

The occurrence of primary extranodal marginal-zone B-cell lymphoma [of the mucosa-associated lymphoid tissue (MALT) type] has only been described in the supraglottic region, implying that preexistent organized lymphoid tissue is present at that site only. To date, studies have not established clearly whether organized MALT shows a site-related distribution in the larynx. The supraglottic region of the false vocal folds and the subglottis from 87 unselected cadavers with no known history of nasal, oral, pharyngeal, laryngeal, tracheal, or esophageal disease were examined for the presence of organized MALT. Organized lymphoid tissue was found with the cytomorphological and immunophenotypic features of MALT in 100% of false vocal folds of children and in more than 90% of adolescents, decreasing to 7.1% in persons in their sixth decade, whereas MALT was completely absent in the subglottis in all age groups. The results explain why primary extranodal marginal-zone B-cell lymphoma has only been described in the supraglottic region but is absent in the subglottis. Moreover, the results suggest a region-specific immunological response of the different laryngeal areas as reflected in clinical observations and animal studies. However, the impact on presence or absence of laryngeal MALT awaits clarification.

Loss of tear duct-associated lymphoid tissue in association with the scarring of symptomatic dacryostenosis

OBJECTIVE

To determine whether organized mucosa-associated lymphoid tissue (MALT) is a normal component of the human efferent tear ducts or is acquired in reaction to chronic inflammation.

DESIGN

Nonrandomized comparative (cadaver controlled) study with histopathologic correlations.

MATERIALS

Tissue specimens from nasolacrimal ducts of 38 patients undergoing endonasal dacryocystorhinostomy in postinflammatory dacryostenosis with signs of chronic inflammation were analyzed using histologic examination and immunohistochemical studies. Only tissue specimens revealing proliferative sclerotic forms of chronic fibrosis were chosen for the study. Eighty specimens from the lacrimal systems of body donors served as controls.

TESTING

Tissue specimens from each lacrimal system were prepared and processed with paraffin, sectioned, stained using different histologic methods with an array of specific antibodies, and examined by light microscopy.

MAIN OUTCOME PARAMETERS

The distribution of intraepithelial and subepithelial defense cells was analyzed to identify plasma cells, secretory immunoglobulins, lymphocytes, dendritic cells, and organized mucosa-associated lymphoid tissue.

RESULTS

The presence of secretory immunoglobulin A was demonstrated in subepithelial plasma cells and in the cytoplasm of apical epithelial cells in both chronically inflamed and healthy lacrimal systems. In more than one third of cases from body donors, but in only a few biopsy specimens from patients, organized lymphoid tissue was found with the cytomorphologic and immunophenotypical features of MALT. All other cases showed a diffuse infiltrate of defense cells within the lamina propria.

CONCLUSIONS

The development of tear duct-associated lymphoid tissue (TALT) is a common feature that is often found in symptomatically normal nasolacrimal ducts. Because TALT seems to be lost associated with the scarring of symptomatic dacryostenosis, it is unlikely that the presence per se of TALT leads to scarring. Future studies are needed to explain the development of TALT.

TFF peptides in the human efferent tear ducts

PURPOSE

To determine whether the lining epithelium of the human lacrimal sac and nasolacrimal duct synthesizes TFF peptides (formerly P-domain peptides, trefoil factors), a family of mucin-associated secretory peptides.

METHODS

Expression of TFF peptides in human lacrimal sac and nasolacrimal ducts was monitored by reverse transcription-polymerase chain reaction and Western blot analysis. Antisera specific for TFF peptides were used in immunohistochemical analysis to determine the presence and distribution of all three TFF peptides in epithelia of the lacrimal passage. The samples investigated originated from tissue obtained during surgery (18 patients) and postmortem tissue (10 specimens).

RESULTS

mRNA expression of TFF1 and TFF3, but not TFF2, was detected in human lacrimal sac and nasolacrimal duct. TFF1 was detected in only approximately 50% of the investigated probes, whereas TFF3 was present in all samples. Immunohistochemistry revealed TFF1 (if present) to be associated with goblet cells forming intraepithelial mucous glands. TFF3 occurred in epithelial cells of the lacrimal sac and the nasolacrimal duct as well as in the acinar cells of subepithelial serous glands, but appeared to be absent in goblet cells.

CONCLUSIONS

The epithelium of the nasolacrimal ducts synthesizes TFF3 and in some cases also TFF1. In contrast to the human conjunctiva, in which TFF3 is detectable only in goblet cells, TFF3 of the lacrimal sac and nasolacrimal duct is produced in large amounts by epithelial cells as well as by serous glands, but not-or in small amounts only-by goblet cells. This is comparable with localization of TFF3 in the major salivary glands. Thus, TFF3 may have a special function in tear transport through the lacrimal passage comparable to its function on the ocular surface, because the peptide, together with TFF1, may contribute to the rheologic properties of the tear film. Moreover, the TFF peptides may also influence epithelial healing with their motogenic properties.

Animal model for the absorption of lipophilic substances from tear fluid by the epithelium of the nasolacrimal ducts

PURPOSE

To compare the nasolacrimal tissues of several species to see how closely they resemble the human and to measure nasolacrimal absorption of a substance, to show that an absorption pathway exists for substances placed in the external eye, other than directly through the cornea or conjunctiva.

METHODS

The nasolacrimal systems of six different vertebrates were investigated by light microscopy to find a species with a nasolacrimal system comparable to that of humans, for use in absorption experiments. In addition to primates, rabbits were revealed by histology to have a lacrimal system closely comparable to that of humans. The rabbit lacrimal system had a stratified epithelium consisting of two layers. Subepithelially, the lamina propria was composed of two strata: loose connective tissue containing elastic fibers and lymphatic cells and a rich venous plexus comparable to a cavernous body. Rabbits were therefore chosen for the absorption experiments. (3)H-cortisol was dropped into the eyes of female rabbits. After 21, 43, or 146 minutes, the rabbits were killed, the blood collected, and the nasolacrimal systems prepared and embedded for histologic examination. Serum was obtained from the clotted blood, and radioactivity was counted. Autoradiographs of sections of rabbit nasolacrimal duct were also prepared.

RESULTS

Uptake of radioactivity into the serum was high and increased with time. After 21 minutes, maximum incorporation of the applied radioactivity into the blood the level was 7.1%; after 43 minutes, 12.4%; and after 146 minutes, 15.5%. Transport of radioactivity was visualized in autoradiographs of rabbit nasolacrimal systems.

CONCLUSIONS

(3)H-cortisol is incorporated from the nasolacrimal ducts into the blood of rabbits. The comparable morphology of rabbits and humans suggests that absorption of cortisol would also take place in humans. Future investigations of the nasolacrimal passage are needed to understand whether absorption of normal tear fluid components in the nasolacrimal ducts is a physiological function that also plays a role in pathologic conditions such as dry eye. The similarities between rabbit and human nasolacrimal ducts support the use of the rabbit for such studies.

Impact of vocal cord paralysis on cricoarytenoid joint

To demonstrate structural changes in the cricoarytenoid joint after recurrent laryngeal nerve paralysis, we performed a laboratory investigation of fixed arytenoid cartilages from adult humans obtained during laser surgical arytenoidectomy in cases of bilateral vocal fold paralysis, analyzing the articular cartilage, the joint capsule, and the attached laryngeal musculature. Ten arytenoid cartilages from adult humans were studied by means of histology, as well as scanning and transmission electron microscopy. After long-standing denervation (>6 months), all arytenoid cartilages showed degenerative changes in their joint surface structure at various levels of intensity. The articular surface revealed fibrillation in some places, demasking of collagen fibrils next to the joint surface, and formation of chondrocyte clusters near the joint surface. All specimens also showed muscle atrophy. We conclude that long-standing recurrent laryngeal nerve paralysis does not result in ankylosis of the cricoarytenoid joint, as assumed, but the articular cartilage undergoes structural changes comparable to those in osteoarthritis. Structural changes in the articular cartilage and in the surrounding musculature hamper efforts at joint function recovery, as do procedures aiming solely at either medialization or lateralization of the vocal fold.

Upper airway epithelial structural changes in obstructive sleep-disordered breathing

The etiology of upper airway collapsibility in patients with snoring and obstructive sleep apnea (OSA) remains unclear. Structural mucosal changes could be contributory factors. The objective of this study was to determine whether pathologic changes in the epithelium or the epithelial-connective tissue interface are present in patients with snoring and/or OSA by means of scanning electron microscopy and immunohistochemistry. Uvulae were obtained by uvulopalatopharyngoplasty from three patients with habitual snoring and nine patients with mild to severe OSA, as well as by dissection from 43 nonsnoring body donors. Scanning electron microscopy revealed structural changes in the epithelial-connective tissue boundary that significantly differed from age-related changes in the control subjects. The immunohistochemical staining with antibodies against epithelial cytokeratins showed differences in the expression pattern of cytokeratin 13 between patients and control subjects. No differences were found in the distribution pattern of laminin. Analysis of defense cells revealed a significant diffuse infiltration of leukocytes, mainly T cells, inside the lamina propria of the patient group, which was not observed in the control group. In conclusion, these results support the hypothesis that progressive structural changes in the mucosa caused by the trauma of snoring are a possible contributory factor to upper airway collapsibility.

Functional anatomy of the papilla Vateri: biomechanical aspects and impact of difficult endoscopic intubation

BACKGROUND

Problems with intubation of the ampulla Vateri during diagnostic and therapeutic endoscopic maneuvers are a well-known feature. The ampulla Vateri was analyzed three-dimensionally to determine whether these difficulties have a structural background.

METHODS

Thirty-five human greater duodenal papillae were examined by light and scanning electron microscopy as well as immunohistochemically.

RESULTS

Histologically, highly vascularized finger-like mucosal folds project far into the lumen of the ampulla Vateri. The excretory ducts of seromucous glands containing many lysozyme-secreting Paneth cells open close to the base of the mucosal folds. Scanning electron microscopy revealed large mucosal folds inside the ampulla that continued into the pancreatic and bile duct, comparable to valves arranged in a row.

CONCLUSIONS

Mucosal folds form pocket-like valves in the lumen of the ampulla Vateri. They allow a unidirectional flow of secretions into the duodenum and prevent reflux from the duodenum into the ampulla Vateri. Subepithelial mucous gland secretions functionally clean the valvular crypts and protect the epithelium. The arrangement of pocket-like mucosal folds may explain endoscopic difficulties experienced when attempting to penetrate the papilla of Vater during endoscopic retrograde cholangiopancreaticographic procedures.

New insights into the pathophysiology of primary acquired dacryostenosis

OBJECTIVE

To obtain new insights into the pathophysiology of primary acquired dacryostenosis.

DESIGN

Comparative autopsy tissue study with histopathologic correlations.

MATERIALS

Tissue specimens from the human nasolacrimal ducts of 36 patients undergoing endonasal dacryocystorhinostomy within a framework of primary acquired dacryostenosis were analyzed by histologic studies and electron microscopic examination. Six lacrimal systems of body donors served as controls.

TESTING

One group of tissue specimens from each lacrimal system was prepared and processed with paraffin, sectioned, stained by different methods, and finally examined by light microscopy. The other group was processed with araldite after preparation, sectioned semithin and ultrathin, and examined by transmission electron microscopy.

MAIN OUTCOME MEASURES

The degree of dacryostenosis was scored in each tissue specimen by grading the histologic sections as mild (active chronic inflammation), moderate (proliferative sclerotic forms of chronic fibrosis), or severe (total subepithelial fibrosis).

RESULTS

Of 36 patients with epiphora, 13 had functional obstruction with a patent lacrimal system on syringing; in 23 cases, the lacrimal passage was completely obstructed. Different pathologic stages correlating to duration of symptoms were found ranging from active chronic inflammation to proliferative sclerotic forms and total subepithelial fibrosis.

CONCLUSIONS

Descending inflammation from the eye or ascending inflammation from the nose initiates swelling of the mucous membrane, remodeling of the helical arrangement of connective tissue fibers, malfunctions in the subepithelial cavernous body with reactive hyperemia, and temporary occlusion of the lacrimal passage. In the follow-up, repeated isolated occurrence of dacryocystitis leads to structural epithelial and subepithelial changes, which may lead either to a total fibrous closure of the lumen of the efferent tear duct or to a nonfunctional segment in the lacrimal passage that is manifest on syringing.

Detection of natural peptide antibiotics in human nasolacrimal ducts

PURPOSE

To determine the expression and production of antimicrobial peptides by mucosal cells of the lacrimal passage in healthy and pathologic states.

METHODS

Detection of bactericidal-permeability-increasing protein (BPI), heparin-binding protein (CAP37), human cationic antimicrobial protein (LL-37), human alpha-defensin 5 (HD5), human alpha-defensin 6 (HD6), human beta-defensin 1 (HBD-1), and human beta-defensin 2 (HBD-2) was performed by reverse transcription-polymerase chain reaction (RT-PCR). Intracellular deposition of lysozyme, lactoferrin, secretory phospholipase A(2), human neutrophil defensins (HNP-1, -2, and -3), human beta-defensin 1 (HBD-1), and human beta-defensin 2 (HBD-2) was analyzed immunohistochemically. Samples were obtained from 15 patients by surgery and from 10 cadavers.

RESULTS

RT-PCR revealed BPI, CAP37, and HBD-1 mRNA in samples of healthy nasolacrimal duct epithelium. Additionally, HBD-2 mRNA was detected in epithelial samples from patients with dacryocystitis. Messenger RNAs for LL-37 and alpha-defensin 5 and 6 were absent in all samples investigated. Immunohistochemistry revealed lysozyme, lactoferrin, secretory phospholipase A(2), and HNP-1, -2, and -3 to be present in all samples, whereas HBD-1 was present only in some of the healthy and inflamed samples. Immunoreactive HBD-2 peptide was visible only in some of the inflamed samples.

CONCLUSIONS

The data suggest that the human efferent tear ducts produce a broad spectrum of antimicrobial peptides. Under inflammatory conditions, changes in the expression pattern occurred, revealing induction of the human inducible defensin HBD-2 and in some cases downregulation of HBD-1 and CAP37. Antimicrobial peptides have a therapeutic potential in dacryocystitis, in that they have a broad spectrum of antimicrobial activity and accelerate epithelial healing. However, caution is appropriate, because defensins also promote fibrin formation and cell proliferation, which are key elements in scarring processes, such as dacryostenosis.

Similarities and differences in lectin cytochemistry of laryngeal and tracheal epithelium and subepithelial seromucous glands in cases of sudden infant death and controls

BACKGROUND

It has been speculated that non-specific defence mechanisms of the epithelium and subepithelial seromucous glands play a role in the larynx and lungs in cases of sudden infant death.

METHODS

The larynx and trachea from five children who had died of sudden infant death (SID) syndrome and five control cases of comparable age were compared for the presence of lectin binding sites (12 different lectins tested).

RESULTS

The secretory product of mucin producing cells contained carbohydrates including galactose and sialic acids. Binding sites for fucose and N-acetyl-galactosamine were only present in some of the specimens and distribution revealed no correlation between cases of SID and controls. Epithelial cells and serous cells of seromucous glands contained binding sites for sialic acid in cases of SID and controls. Moreover, binding sites for mannose were detected in these cells but were only present in SID cases. The difference between the SID and control groups as to the presence/expression of concanavalin A was highly significant.

CONCLUSIONS

It is suggested that mucus hypersecretion in SID occurs in response to bacterial toxins or viral infection and is not specific. The different binding sites for mannose in cases of SID and controls could indicate differences in the production of antimicrobial peptides. A disturbed expression pattern of antimicrobial peptides in children who later succumb to SID could be responsible for an imbalance of the local microflora with a higher density of microorganisms on the mucosa. Further studies are required to elucidate the pattern of expression of antimicrobial peptides in subsequent SID victims.

Mucosa-associated lymphoid tissue in human efferent tear ducts

The recent description of primary marginal zone lymphomas in human efferent tear ducts with typical features of lymphomas arising in mucosa-associated lymphoid tissue (MALT) infers the presence of MALT in the human efferent tear ducts. To date, studies have not established clearly whether organised MALT occurs in normal human efferent tear ducts. To elucidate this problem, efferent lacrimal pathways from unselected body donors with unknown prior history of efferent tear duct, ocular, or nasal disease were examined for the presence of organised MALT. Organised lymphoid tissue was found with the cytomorphological and immunophenotypic features of MALT in 41% of the cases examined. These findings suggest that MALT is a feature that, although it need not be present in normal efferent tear ducts, is acquired during life in a proportion of apparently asymptomatic individuals.

The cavernous body of the human efferent tear ducts: function in tear outflow mechanism

PURPOSE

To determine the structure and function of a system of large blood vessels integrated in the bony canal between the orbit and the inferior nasal duct.

METHODS

Thirty-one dissected lacrimal systems of adults were analyzed by using gross anatomy, histology, and electron microscopy as well as corrosion vascular casts.

RESULTS

More than two thirds of the bony canal between orbit and inferior nasal duct is filled by a plexus of wide-lumened veins and arteries. The vascular system is embedded in the wall of the lacrimal sac and nasolacrimal duct and is connected to the cavernous tissue of the inferior turbinate. Three types of blood vessels can be distinguished inside the vascular tissue that surrounds the lumen of the lacrimal passage: barrier arteries, capacitance veins, and throttle veins.

CONCLUSIONS

The surrounding vascular plexus of the lacrimal sac and nasolacrimal duct is comparable to a cavernous body. While regulating the blood flow, the specialized blood vessels permit opening and closing of the lumen of the lacrimal passage, effected by the bulging and subsiding of the cavernous body, and at the same time regulate tear outflow. Other functions such as drainage of absorbed tear fluid components and a role in immunologic response are under discussion as well. Malfunctions in the cavernous body may lead to disturbances in the tear outflow cycle, ocular congestion, or total occlusion of the lacrimal passages. Variations in the conditions for swelling of the cavernous tissue may have led to the (mistaken) description of valves in the lacrimal passage.

The cricoarytenoid joint capsule and its relevance to endotracheal intubation

Impaired movement of the cricoarytenoid joint with hoarseness and immobility of the vocal ligament may occur as a consequence of endotracheal intubation. Little is known about the cricoarytenoid joint capsule and its role in intubation. We investigated the joint capsules of 48 cricoarytenoid joints by means of gross anatomy microscopy, histology, and scanning electron microscopy; 30 unfixed cadaver larynges were also subjected to attempts to simulate traumata such as those that may occur during intubation trials. The larynges were intubated with the arytenoid tip entering the lumen of the tracheal tube or extubated with the cuff of the tube only partially deflated. Subsequently, i.e., after dissecting the left and right cricoarytenoid joint from each larynx, the morphologic changes induced experimentally were analyzed by using histologic methods. The cricoarytenoid joint was found to be lined by a wide joint capsule. Unexpectedly large and intensively vascularized synovial folds projected into the joint cavity. After simulation of intubation and extubation, histologic analysis revealed injuries to the synovial folds and joint surface impressions, but no trauma or rupture of the outer joint capsule. We conclude that laxity of the joint capsule and the large synovial folds are predisposing factors for intubation trauma of the cricoarytenoid joint, potentially leading to hemarthros and finally to cricoarytenoid joint dysfunction.

IMPLICATIONS

The present study illustrates by morphological investigations and intubation experiments that laxity of the joint capsule and large synovial folds are predisposing factors for intubation trauma of the cricoarytenoid joint, potentially leading to hemarthrosis and finally to cricoarytenoid joint dysfunction.

Osteoarthritis in cricoarytenoid joint

OBJECTIVE

Occurrence of osteoarthritis is a frequent event of limb joints in people over 40 years of age. The human cricoarytenoid joint is comparable with the joints of the limbs despite its structure and extracellular matrix composition. To date, little is known about the occurrence of osteoarthritis in the human cricoarytenoid joint.

METHODS

Sixty-eight cricoarytenoid joints (42 male and 26 female, age 25-98 years) were analysed by means of histology, lectin histochemistry, immunohistochemistry as well as scanning and transmission electron microscopy.

RESULTS

About 50% of the investigated cricoarytenoid joints aged over 40 years show degenerative changes in their joint surface structure at varying levels of intensity. The articular cartilage surface is fibrillated in some places and sometimes shows fissures. A demascing of collagen fibrils next to the joint surface and a loss of proteoglycans in the upper cartilage layers can be observed. Chondrocytes near the joint surface appear as voluminous chondrocyte clusters. The clusters and the superficial cartilage layer show a positive reaction to type VI collagen antibodies. The distribution patterns of lectins are completely changed in fibrillated cartilage areas.

CONCLUSION

Degenerative alterations in diarthrodial joints resembling osteoarthritis can occur in the joints of the larynx. These structural changes of the articular cartilage are comparable to osteoarthritis of the limb joints. Osteoarthritis in the cricoarytenoid joint may lead to impaired movements of the arytenoid cartilages. Functionally the structural changes may lead to negative consequences during vocal production, such as impaired vocal quality and reduced vocal intensity.

New insights into the pathomechanism of postintubation arytenoid subluxation

BACKGROUND

Impaired movement of the cricoarytenoid joint with hoarseness and immobility of the vocal ligament can occur as a consequence of endotracheal intubation. The biomechanics and pathomechanism of cricoarytenoid subluxation have not been demonstrated to date.

METHODS

The present study attempts to simulate the trauma that has been associated with arytenoid cartilage subluxation in intubation trials on 37 unfixed larynges in cadavers from persons aged 25 to 89 years. Larynges were intubated or extubated according to former conceptions of arytenoid subluxation, which assume that the arytenoid tip enters the lumen of the tracheal tube, or that a deflection of the arytenoid occurs during withdrawal of the endotracheal tube with the cuff of the tube only partially deflated. Also, manual attempts were carried out to subluxate the arytenoid cartilage. Subsequently after dissecting the left and right cricoarytenoid joint from each larynx, the morphologic changes induced experimentally were analyzed using gross microscopic and histologic methods.

RESULTS

Within the scope of the experiment, it proved impossible to produce any subluxation of a cricoarytenoid joint. Histologic analysis revealed injuries of synovial folds, joint-surface impressions of the articular cartilage, and fractures in the area of the subchondral bone in some joints.

CONCLUSIONS

Based on the morphologic results, it was concluded that intubation trauma of the cricoarytenoid joint does not cause subluxation per se, but rather that formation of a hemarthros or fractures of the joint bodies lead to fixation of the joint surfaces in an abnormal position. Subsequent ankylosis may occur.