A new model system for studying lacrimal physiology using cultured lacrimal gland acinar cells on Matrigel rafts

[Cell technologies as a basis for the development of regenerative principles for the treatment of lacrimal gland diseases]

The lacrimal gland (LG) is a tubuloacinar exocrine gland composed of acinar, ductal, and myoepithelial cells. Three-dimensional distribution of acinar lobules, ducts, and myoepithelial cells is necessary for the effective functioning of the organ. LG is the main organ of immune surveillance of the ocular surface system. The embryogenesis of the gland is regulated by the interaction of genetic mechanisms, internal epigenetic (enzyme systems, hormones) and exogenous factors. There is no doubt that there is a clear genetic program for the implementation of the complex process of embryonic development. The mechanisms regulating LG organogenesis initiate the work of a huge number of structural oncogenes, transcription and growth factors, etc. Studying the expression and selective activity of regulatory genes during organ development, their participation in the differentiation of different cell types is a current trend at the nexus of clinical genetics, molecular biology, embryology and immunocytochemistry. Due to its relatively simple structure and accessibility, human LG is a suitable object for potential application in regenerative medicine. Development of a universal protocol for obtaining functional differentiated secretory epithelium of LG capable of expressing tissue-specific markers is an urgent task. Determining the nature and origin of stem cells and progenitor cells will allow the isolation and multiplication of these cells in culture. After obtaining a functionally active culture of LG cells, it is possible to create a model of autoimmune diseases.

Establishing human lacrimal gland cultures from biopsy-sized tissue specimens

OBJECTIVES

To establish cultures of human lacrimal gland from patient-derived, biopsy-sized, tissue specimens.

METHODS

Tissue was obtained after surgical removal from patients without dry eye disease undergoing routine procedures. Samples were subjected to mechanical and enzymatic digestion and resulting cell suspensions were plated onto collagen-coated glass coverslips and grown for up to 21 days. Cultures were analysed by immunocytochemistry and light microscopy, and resultant cellular distributions were compared to those in sections of fixed human lacrimal gland tissue.

RESULTS

Dissociation of biopsy-sized pieces of human lacrimal gland and seeding onto coated surfaces allowed development of a mixed population of cells in vitro. Within 7-14 days, cellular aggregation was observed and by 21 days many cells had organised themselves into distinct three-dimensional complexes. Immunohistochemistry revealed a heterogeneous population of cells, including epithelial, myoepithelial, mesenchymal and progenitor cells. Some of the epithelia labelled positively for lysozyme and lactoferrin.

CONCLUSIONS

Collection and dissociation of biopsy-sized pieces of human lacrimal gland leads to a cellular preparation that can proliferate in vitro and organise into three-dimensional structures. This is the first report detailing that biopsy-collected specimens of human lacrimal gland can be used to establish cell cultures.

Tissue Engineering in Ophthalmology: Implications for Eyelid Reconstruction

PURPOSE

Bioengineering aims to produce functional tissue replacements to repair defects and has been widely investigated over the past few decades. We aimed to review the available literature on the application of tissue engineering in ophthalmology, with a particular focus on ophthalmic plastic surgery and potential applications for eyelid reconstruction.

METHODS

A literature search was performed on the MEDLINE database using the keywords "bioengineering," "tissue engineering," and "ophthalmology." Articles written in English were included.

RESULTS

There is a substantial body of work on tissue engineering of the cornea. Other structures in ophthalmology investigated include the conjunctiva, lacrimal gland, and orbital bone. We also discuss the potential application of tissue engineering in eyelid reconstruction.

CONCLUSION

Tissue engineering represents the future of regenerative and reconstructive medicine, with significant potential applications in ophthalmic plastic surgery.

Characterization of membranous (M) cells in normal feline conjunctiva-associated lymphoid tissue (CALT)

OBJECTIVE

To characterize conjunctival lymphoid nodules obtained from the nictitans of healthy cats to determine if the follicle-associated epithelium (FAE) of conjunctiva-associated lymphoid tissue (CALT) in this species contains membranous (M)-cells analogous to those described in other regions of mucosa-associated lymphoid tissue (MALT).

METHODS

Lymphoid follicles from nictitan bulbar surfaces of 10 healthy cats (20 eyes total) were examined. Nictitans from five cats were harvested immediately post-mortem and a minimum of 12 lymphoid nodules from each third eyelid were isolated using a Zeiss operating microscope. At least three lymphoid follicles from each eye were examined using light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) using standard fixation and embedding protocols. Nictitan-lymphoid follicles from another five healthy cats were processed for immunohistochemistry to characterize the distribution of T- and B-lymphocytes present beneath the FAE.

RESULTS

The FAE overlying CALT from 10 healthy cats demonstrated morphology characteristic of M-cells including attenuated apical cell surface with blunted microvilli and microfolds, invaginated basolateral membrane forming a cytoplasmic pocket, and diminished distance between the apical and pocket membrane. Immunohistochemistry of lymphoid tissue subtending the FAE demonstrated B-cell dependent regions in the germinal centers surrounded by T-cell dependent interfollicular zones.

CONCLUSIONS

Healthy feline CALT contains morphologic features analogous to those described in other regions of MALT. Documentation of feline conjunctival M-cells is of clinical relevance in the study of primary infectious, allergic, and autoimmune ocular diseases, as well as a potential means of vaccination or drug delivery.

Allergic conjunctivitis and nasal allergy

Allergic conjunctivitis (AC) can be divided into the primary form (caused by an allergic reaction occurring primarily in the conjunctivae) and the secondary form (induced by allergic reaction originating primarily in the nasal mucosa, where the released mediators can reach conjunctiva through the lacrimal system, the blood, the lymphatic network, or the neurogenic network). Patients with primary AC develop an immediate, late, or delayed conjunctival response (CR) during conjunctival provocation tests. Patients with secondary AC develop an immediate, late, or delayed type of secondary CR, induced by the nasal allergic reaction, due to the nasal allergen challenge. Various hypersensitivity mechanisms may be involved in the particular CR types. The secondarily induced AC and CRs can only be confirmed by nasal provocations tests, performed by rhinomanometry combined with recording of conjunctival signs. The existence of the primary and secondarily induced AC has an impact on treatment of this disorder.

Seasonal and perennial allergic conjunctivitis: the possible role of nasal allergy

BACKGROUND

There is a link between conjunctiva and nose. Nasal allergy is suspected to be involved in some cases of conjunctivitis. This work aims to investigate the possible role of nasal allergy in seasonal (SAC) and perennial (PAC) allergic conjunctivitis and the value of nasal challenges with allergens (nasal provocation tests [NPTs]) for the diagnostic procedures of the conjunctivitis.

METHODS

In 61 adults suffering from SAC or PAC with a positive history and skin tests, but responding insufficiently to the local treatment, 122 NPTs and 61 control nasal challenges with phosphate-buffered saline (PBS) were performed using rhinomanometry combined with recording of ocular response. In 16 control subjects suffering only from allergic rhinitis without a history of conjunctivitis, 16 positive NPTs were repeated and supplemented with registration of ocular features.

RESULTS

Of the 61 patients, 55 developed 103 positive nasal responses of various types (P < 0.01), 82 of which were accompanied by significant conjunctival response (P < 0.01) without any corneal involvement. No significant ocular responses were recorded during 61 control PBS challenges (P > 0.05) as well as during 16 challenges in control subjects (P > 0.1).

CONCLUSIONS

These results illustrate a possible involvement of nasal allergy in some patients with allergic conjunctivitis (SAC and PAC) and the value of the nasal challenges with allergen combined with registration of the ocular features in the diagnostic approach to these disorders.

Ophthalmic lymphoma: epidemiology and pathogenesis

With a lifetime risk of 1% and 700 new cases per year, Non-Hodgkin lymphoma (NHL) is the seventh most frequent type of cancer in Denmark. The incidence of NHL has increased considerably in Western countries over the last decades; consequently, NHL is an increasing clinical problem. Ophthalmic lymphoma, (lymphoma localized in the ocular region, i.e. eyelid, conjunctiva, lacrimal sac, lacrimal gland, orbit, or intraocularly) is relatively uncommon, accounting for 5%-10% of all extranodal lymphomas. It is, however, the most common orbital malignancy. The purpose of this thesis was to review specimens from all Danish patients with a diagnosis of ophthalmic lymphoma during the period 1980-2005, in order to determine the distribution of lymphoma subtypes, and the incidence- and time trends in incidence for ophthalmic lymphoma. Furthermore, an extended analysis of the most frequent subtype, extranodal marginal zone lymphoma (MALT lymphoma), was done to analyse clinical factors and cytogenetic changes with influence on prognosis. A total of 228 Danish patients with a biopsy-reviewed verified diagnosis of ocular adnexal-, orbital-, or intraocular lymphoma were identified. We found that more than 50% of orbital- and ocular adnexal lymphomas were of the MALT lymphoma subtype, whereas diffuse large B-cell lymphoma (DLBCL) predominated intraocularly (Sjo et al. 2008a). Furthermore, lymphoma arising in the lacrimal sac was surprisingly predominantly DLBCL (Sjo et al. 2006). Incidence rates were highly dependent on patient age. There was an increase in incidence rates for the whole population from 1980 to 2005, corresponding to an annual average increase of 3.4% (Sjo et al. 2008a). MALT lymphoma arising in the ocular region was found in 116 patients (Sjo et al. 2008b). One third of patients had a relapse or progression of disease after initial therapy and relapses were frequently found at extra-ocular sites. Overall survival, however, was not significantly poorer for patients with relapse. Furthermore, we found that the frequency of translocations involving the MALT1- and IGH-gene loci is low in ocular region MALT lymphoma (2 of 42, 5%), but may predict increased risk of relapse (Sjo et al. 2008b). In conclusion the incidence of ophthalmic lymphoma is increasing at a high rate in Denmark. Ophthalmic lymphoma consists primarily of MALT lymphoma. The molecular pathogenesis of MALT lymphoma arising in the ocular region rarely involves translocations in the MALT1- and IGH-gene loci.

Influence of the eye-associated lymphoid tissue (EALT) on inflammatory ocular surface disease

Certain similarities exist in the pathophysiological processes and clinical features of advanced stages of various inflammatory ocular surface diseases, suggesting that common pathways contribute to these diseases. In this article, common pathways are analyzed with a focus on the role of the physiological resident mucosal immune system of the ocular surface, termed eye-associated lymphoid tissue (EALT). This is physiologically protective but if it is deregulated it can mediate an inflammatory immune answer. Common events in inflammatory ocular surface disease lead to a vicious circle of immune-modulated inflammation, with degenerative remodeling and loss of function.

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.

Tissue-engineered tear secretory system: functional lacrimal gland acinar cells cultured on matrix protein-coated substrata

Dry eye is a general term that refers to a myriad of ophthalmic disorders resulting in the inadequate wetting of the corneal surface by the tear film. Dry eyes are typically treated by the application of artificial tears. However, patients with lacrimal insufficiencies such as Stevens-Johnson syndrome, chemical and thermal injuries, or ocular cicatricial pemphigoid have very limited options because of the short duration and action of lubricating agents. As a therapeutic strategy, we are working to develop a bioengineered tear secretory system for such patients. This article describes the growth and physiological properties of purified rabbit lacrimal gland acinar cells (pLGACs) on several matrix protein-coated polymers such as silicone, collagen I, copolymers of poly-D,L-lactide-co-glycolide (PLGA; 85:15 and 50:50), poly-L-lactic acid (PLLA), and Thermanox plastic cell culture coverslips. Monolayers of acinar cells were established on all of the polymeric substrata. An assay of beta-hexosaminidase activity in the supernatant medium showed significant increases in protein secretion, following stimulation with 100 microM carbachol on matrix protein-coated and uncoated polymers such as silicone, PLGA 85:15, and PLLA. Our study demonstrates that PLLA supported the morphological and physiological properties of purified rabbit lacrimal gland epithelial cells more successfully than the others.

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.

Cell and molecular biology of human lacrimal gland and nasolacrimal duct mucins

The old concept that the lacrimal gland is only a serous gland has been superseded by the finding that lacrimal acinar cells are able to produce mucins--high-molecular-weight proteins--the major mass being carbohydrates with the common feature of tandem repeats of amino acids rich in serine, threonine, and proline in the central domain of the mucin core peptide. At the ocular surface, maintenance of the tear film, lubrication, and provision of a pathogen barrier on the epithelia, conjunctiva, and cornea have been shown to be facilitated by mucins that are present in membrane-anchored (lining epithelial cells) or secreted (goblet cells) form. Also in the lacrimal gland, both membrane-anchored (MUCs 1, 4, and 16) and secreted (MUCs 5B and 7) mucins have been identified. The lacrimal gland is the main contributor to the aqueous portion of the tear film. It is part of the lacrimal apparatus that comprises, together with the lacrimal gland, the paired lacrimal canaliculi, the lacrimal sac, and the nasolacrimal duct, which collects the tear fluid and conveys it into the nasal cavity. In this review, the latest information regarding mucin function in the human lacrimal gland and the human efferent tear ducts 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 the pathogenesis of dry eye, dacryostenosis, and dacryolith formation.

Ultrastructural anatomy of CALT follicles in the rabbit reveals characteristics of M-cells, germinal centres and high endothelial venules

Conjunctiva-associated lymphoid tissue (CALT) is a part of the eye-associated lymphoid tissue (EALT) at the ocular surface. Its lymphoid follicles are usually characterized by using light microscopy, but its ultrastructure remains largely unknown. In this study, flat whole-mount conjunctival tissues (n = 42) from 21 young adult rabbits were investigated native in reflected light, and further stained and cleared (n = 6), in paraffin histology sections (n = 6), scanning electron microscopy (SEM, n = 4) and transmission electron microscopy (TEM, n = 4). Secondary lymphoid follicles accumulated into a dense group nasally towards the lacrimal punctum of the lower lid. High endothelial venules (HEV) with typical ultrastructure occurred in the parafollicular zone. The bright germinal centre (GC) contained lymphoblasts, follicular dendritic cells, apoptotic cells and tingible body macrophages. The follicle-associated epithelium (FAE) was devoid of goblet cells and contained groups of lymphoid cells. TEM showed these cells to be located in cytoplasmic pockets of superficial electron-lucent cells with a thin cytoplasmic luminal lining that contained a fine filament meshwork and numerous endocytotic vesicles. These M-cells were sitting between and on top of the ordinary dense epithelial cells that were located basally and formed pillar-like structures. In stereoscopic SEM, the surface cells were very large, had a polygonal outline and covered cavernous spaces. The rabbit has a CALT with typical follicular morphology, including HEV for regulated lymphocyte migration and epithelial cells with ultrastructural characteristics of M-cells that allow antigen transport as indicated by the GC-reaction. The arrangement of these M-cells on top of and between epithelial pillar cells may reflect a special structural requirement of the multilayered CALT FAE.

The role of eye-associated lymphoid tissue in corneal immune protection

Because the cornea is optimized for refraction, it relies on supporting tissues for moistening and nutrition and in particular for immune protection. Its main support tissue is the conjunctiva, in addition to the lacrimal gland, the latter which provides soluble mediators via the tear film. The cornea and conjunctiva constitute a moist mucosal surface and there is increasing evidence that apart from innate defence mechanisms, also lymphoid cells contribute to the normal homeostasis of the corneal surface. A Medline-based literature search was performed in order to review the existing literature on the existence, composition and functions of mucosa-associated lymphoid tissue (MALT) at the ocular surface for corneal protection. The existence of lymphoid cells at the ocular surface and appendage has been known for many years, but for a long time they were believed erroneously to be inflammatory cells. More recent research has shown that in addition to the known presence of lymphoid cells in the lacrimal gland, they also form MALT in the conjunctiva as conjunctiva-associated lymphoid tissue (CALT) and in the lacrimal drainage system as lacrimal drainage-associated lymphoid tissue (LDALT). Together this constitutes an eye-associated lymphoid tissue (EALT), which is a new component of the mucosal immune system of the body. When the topographical distribution of CALT is projected onto the ocular surface, it overlies the cornea during eye closure and is hence in a suitable position to assist the corneal immune protection during blinking and overnight. It can detect corneal antigens and prime respective effector cells, or distribute protective factors as secretory IgA.