Proliferation of lacrimal gland acinar cells in primary culture. Stimulation by extracellular matrix, EGF, and DHT

[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.

Current approaches for the regeneration and reconstruction of ocular surface in dry eye

Significant research revealed the preocular tear film composition and regulations that remain vital for maintaining Ocular surface functional integrity. Inflammation triggered by many factors is the hallmark of Ocular surface disorders or dry eyes syndrome (DES). The tear deficiencies may lead to ocular surface desiccation, corneal ulceration and/or perforation, higher rates of infectious disease, and the risk of severe visual impairment and blindness. Clinical management remains largely supportive, palliative, and frequent, lifelong use of different lubricating agents. However, few advancements such as punctal plugs, non-steroidal anti-inflammatory drugs, and salivary gland autografts are of limited use. Cell-based therapies, tissue engineering, and regenerative medicine, have recently evolved as long-term cures for many diseases, including ophthalmic diseases. The present article focuses on the different regenerative medicine and reconstruction/bioengineered lacrimal gland formation strategies reported so far, along with their limiting factors and feasibility as an effective cure in future.

Morphological Changes in the Lacrimal Gland of Anophthalmic Socket in Relation to the Contralateral Normal Eye in Male Wistar Albino Rats: A Histopathology Study

Purpose: The purpose of the study is to analyze the structural and functional alterations of the lacrimal gland and its tear secretion post-enucleation in Wistar rats.Method: Adult male Wistar rats (n = 15) of 8-week-old were randomly assigned into three groups viz. control, sham, and experimental group (n = 5). Rats of the experimental group were subjected to enucleation of the right eye. Under aseptic surgical conditions, with sterilized forceps, right eyeball of the rats of experimental group was exposed completely out of the socket by applying pressure on the lateral canthus of the eye. Enucleation was then achieved after holding the optic nerve tightly. The surgical procedure was similar in sham group without enucleation. Quantity of tears (Basal and reflex) secreted in both eyes in rats of all groups were measured by using Schirmer's strip, pre- and post-three weeks of enucleation. The lacrimal gland was harvested to analyze histopathological (structural) alterations.Results: Pr- and post-enucleation there was no significant difference observed in the tear volume across the groups. Histopathology of the lacrimal glands from all groups showed preserved lobular architecture with serous acini arranged in lobules, intralobular and interlobular ducts, interstitial fibro collagenous tissue. There was no glandular distortion and atrophy in experimental group.Conclusion: Enucleation do not co-relate or affect the tear volume and lacrimal gland acinar microstructural changes in an anophthalmic socket co-relating to the contralateral normal functional eye.

Three-Dimensional Culture of Ameloblast-Originated HAT-7 Cells for Functional Modeling of Defective Tooth Enamel Formation

Background: Amelogenesis, the formation of dental enamel, is well understood at the histomorphological level but the underlying molecular mechanisms are poorly characterized. Ameloblasts secrete enamel matrix proteins and Ca²⁺, and also regulate extracellular pH as the formation of hydroxyapatite crystals generates large quantities of protons. Genetic or environmental impairment of transport and regulatory processes (e.g. dental fluorosis) leads to the development of enamel defects such as hypomineralization.

Aims: Our aims were to optimize the culture conditions for the three-dimensional growth of ameloblast-derived HAT-7 cells and to test the effects of fluoride exposure on HAT-7 spheroid formation.

Methods: To generate 3D HAT-7 structures, cells were dispersed and plated within a Matrigel extracellular matrix scaffold and incubated in three different culture media. Spheroid formation was then monitored over a two-week period. Ion transporter and tight-junction protein expression was investigated by RT-qPCR. Intracellular Ca²⁺ and pH changes were measured by microfluorometry using the fluorescent dyes fura-2 and BCECF.

Results: A combination of Hepato-STIM epithelial cell differentiation medium and Matrigel induced the expansion and formation of 3D HAT-7 spheroids. The cells retained their epithelial cell morphology and continued to express both ameloblast-specific and ion transport-specific marker genes. Furthermore, like two-dimensional HAT-7 monolayers, the HAT-7 spheroids were able to regulate their intracellular pH and to show intracellular calcium responses to extracellular stimulation. Finally, we demonstrated that HAT-7 spheroids may serve as a disease model for studying the effects of fluoride exposure during amelogenesis.

Conclusion: In conclusion, HAT-7 cells cultivated within a Matrigel extracellular matrix form three-dimensional, multi-cellular, spheroidal structures that retain their functional capacity for pH regulation and intracellular Ca²⁺ signaling. This new 3D model will allow us to gain a better understanding of the molecular mechanisms involved in amelogenesis, not only in health but also in disorders of enamel formation, such as those resulting from fluoride exposure.

Hyperglycemia-induced severe mitochondrial bioenergetic deficit of lacrimal gland contributes to the early onset of dry eye in diabetic mice

Dry eye and diabetic keratopathy represent the major diabetic complications in ocular surface. Here we found that diabetic mice exhibited the early onset of reduced tear secretion and lacrimal gland weight compared to the symptoms of diabetic keratopathy. Considering to the high bioenergetic needs in lacrimal gland and cornea, we hypothesized that hyperglycemia may cause different severity of mitochondrial bioenergetic deficit between them. Through the measurement of oxygen consumption rate (OCR) and basal extracellular acidification rate (ECAR), we found the apparent alterations of mitochondrial bioenergetic profiles in diabetic lacrimal gland and cornea, accompanied with the mtDNA damage and copy number reduction, as well as the reduced glutathione content. Comparative analysis revealed that mouse lacrimal gland cells exhibited 2-3 folds higher of basal, ATP production, maximal OCR and basal ECAR than corneal epithelial cells in normoglycemia. However, the differences were slightly significant or even not detected in hyperglycemia. Accordingly, the mitochondrial bioenergetic metabolism of lacrimal gland was more compromised than that of corneal epithelium in diabetic mice. Through the administration of mitochondrial-targeted antioxidant SkQ1, the severity of dry eye and diabetic keratopathy was significantly attenuated with the improved mitochondrial function. These results indicate that the susceptibility of mitochondrial bioenergetic deficit in diabetic lacrimal gland may contribute to the early onset of dry eye, while mitochondria-targeted antioxidant possesses therapeutic potential for diabetic dry eye and keratopathy.

Lacrimal gland development: From signaling interactions to regenerative medicine

The lacrimal gland plays a pivotal role in keeping the ocular surface lubricated, and protecting it from environmental exposure and insult. Dysfunction of the lacrimal gland results in deficiency of the aqueous component of the tear film, which can cause dryness of the ocular surface, also known as the aqueous-deficient dry eye disease. Left untreated, this disease can lead to significant morbidity, including frequent eye infections, corneal ulcerations, and vision loss. Current therapies do not treat the underlying deficiency of the lacrimal gland, but merely provide symptomatic relief. To develop more sustainable and physiological therapies, such as in vivo lacrimal gland regeneration or bioengineered lacrimal gland implants, a thorough understanding of lacrimal gland development at the molecular level is of paramount importance. Based on the structural and functional similarities between rodent and human eye development, extensive studies have been undertaken to investigate the signaling and transcriptional mechanisms of lacrimal gland development using mouse as a model system. In this review, we describe the current understanding of the extrinsic signaling interactions and the intrinsic transcriptional network governing lacrimal gland morphogenesis, as well as recent advances in the field of regenerative medicine aimed at treating dry eye disease. Developmental Dynamics 246:970-980, 2017. © 2017 Wiley Periodicals, Inc.

TFOS DEWS II Sex, Gender, and Hormones Report

One of the most compelling features of dry eye disease (DED) is that it occurs more frequently in women than men. In fact, the female sex is a significant risk factor for the development of DED. This sex-related difference in DED prevalence is attributed in large part to the effects of sex steroids (e.g. androgens, estrogens), hypothalamic-pituitary hormones, glucocorticoids, insulin, insulin-like growth factor 1 and thyroid hormones, as well as to the sex chromosome complement, sex-specific autosomal factors and epigenetics (e.g. microRNAs). In addition to sex, gender also appears to be a risk factor for DED. "Gender" and "sex" are words that are often used interchangeably, but they have distinct meanings. "Gender" refers to a person's self-representation as a man or woman, whereas "sex" distinguishes males and females based on their biological characteristics. Both gender and sex affect DED risk, presentation of the disease, immune responses, pain, care-seeking behaviors, service utilization, and myriad other facets of eye health. Overall, sex, gender and hormones play a major role in the regulation of ocular surface and adnexal tissues, and in the difference in DED prevalence between women and men. The purpose of this Subcommittee report is to review and critique the nature of this role, as well as to recommend areas for future research to advance our understanding of the interrelationships between sex, gender, hormones and DED.

Age-related Defects in Ocular and Nasal Mucosal Immune System and the Immunopathology of Dry Eye Disease

Dry eye disease (DED) is a prevalent public health concern that affects up to 30% of adults and is particularly chronic and severe in the elderly. Two interconnected mechanisms cause DED: (1) an age-related dysfunction of lacrimal and meibomian glands, which leads to decreased tear production and/or an increase in tear evaporation; and (2) an age-related uncontrolled inflammation of the surface of the eye triggered by yet-to-be-determined internal immunopathological mechanisms, independent of tear deficiency and evaporation. In this review we summarize current knowledge on animal models that mimic both the severity and chronicity of inflammatory DED and that have been reliably used to provide insights into the immunopathological mechanisms of DED, and we provide an overview of the opportunities and limitations of the rabbit model in investigating the role of both ocular and nasal mucosal immune systems in the immunopathology of inflammatory DED and in testing novel immunotherapies aimed at delaying or reversing the uncontrolled age-related inflammatory DED.

Challenges and Strategies for Regenerating the Lacrimal Gland

The lacrimal gland produces the aqueous component of tears, including electrolytes, peptides, and glycoproteins necessary to maintain homeostasis and optical properties of the ocular surface. Stem cells that contribute to the homeostasis of the lacrimal gland are under extensive study. It is still unclear whether such stem cells are of mesenchymal or epithelial origin. It is also possible that a unique epithelial stem cell undergoes epithelial-mesenchymal transition and contributes to the mesenchyme. Developmental studies in mice have shown that a network of growth factors contributes to epithelial-mesenchymal interaction during morphogenesis of the lacrimal gland. Recently, the developmental process was successfully recapitulated in vitro, providing a valuable tool for study of lacrimal gland development and possibly opening doors to regenerative therapy. While further studies are required to identify and appreciate the potential of lacrimal gland stem cells, advances in stem cell biology in general should become a catalyst towards developing regenerative therapy of the lacrimal gland.

Three-Dimensional Culture of Functional Adult Rabbit Lacrimal Gland Epithelial Cells on Decellularized Scaffold

Aqueous tear-deficient dry eye disease is a multifactorial chronic disorder, in which the lacrimal gland fails to produce enough tears to maintain a healthy ocular surface. Some severe cases may develop corneal damage and significant vision loss. Treatment primarily involves palliation using ocular surface lubricants, but can only provide temporary relief. Construction of a bioengineered lacrimal gland having functional secretory epithelial cells is a potentially promising option for providing long-term relief to severe dry eye patients. Using sphere-forming culture techniques, we cultured adult rabbit lacrimal gland progenitor cells and prepared a lacrimal gland scaffold by decellularization. When progenitor cells were seeded onto the decellularized scaffold, they formed duct- and acinar-like structures in the three-dimensional culture system. Lacrimal gland epithelial cells showed good cell viability, cell differentiation, and secretory function in decellularized lacrimal gland matrix, as indicated by morphology, immunostaining, and β-hexosaminidase secretion assay. This study demonstrated the potential suitability of utilizing tissue-specific progenitor cells and a tissue-derived bioscaffold for lacrimal gland restoration.

Evidence for Active Electrolyte Transport by Two-Dimensional Monolayers of Human Salivary Epithelial Cells

Functional reconstruction of lost tissue by regenerative therapy of salivary glands would be of immense benefit following radiotherapy or in the treatment of Sjogren's syndrome. The purpose of this study was to develop primary cultures of human salivary gland cells as potential regenerative resources and to characterize their acinar/ductal phenotype using electrophysiological measurements of ion transport. Human salivary gland cultures were prepared either from adherent submandibular gland cells (huSMG) or from mixed adherent and nonadherent cells (PTHSG) and were cultivated in Hepato-STIM or minimum essential medium (MEM). Expression of key epithelial marker proteins was determined by quantitative reverse transcription polymerase chain reaction (RT-PCR). Transepithelial electrical resistance (TER) was monitored following seeding the cells on Transwell membranes. Transepithelial ion transport was estimated by short-circuit current (Isc) measurements in an Ussing chamber. Both huSMG and PTHSG cells showed epithelial characteristics when cultivated in Hepato-STIM, while fibroblast-like elements dominated in MEM. Compared to intact tissue, cultivation of the cells resulted in substantial decreases in AQP5 and NKCC1 expression and moderate increases in claudin-1 and ENaC expression. Both cultures achieved high TER and transepithelial electrolyte movement in Hepato-STIM, but not in MEM. The Isc was substantially reduced by basolateral Cl(-) and bicarbonate withdrawal, indicating the involvement of basolateral-to-apical anion transport, and by the blockade of apical ENaC by amiloride, indicating the involvement of apical-to-basolateral Na(+) transport. An almost complete inhibition was observed following simultaneous ENaC block and withdrawal of the two anions. Isc was enhanced by either apical adenosine triphosphate (ATP) or basolateral carbachol application, but not by forskolin, confirming the expected role of Ca(2+)-activated regulatory pathways in electrolyte secretion. Inhibition of basolateral NKCC1 by bumetanide reduced the response to ATP, indicating the active involvement of this transporter in Cl(-) secretion. In conclusion, we have demonstrated that both PTHSG and huSMG primary cultures cultivated in Hepato-STIM form two-dimensional monolayers in vitro on permeable supports and achieve active vectorial transepithelial electrolyte transport. The presence of both basolateral-to-apical anion fluxes and an apical-to-basolateral Na(+) flux indicates both acinar and ductal characteristics. With further refinement, this model should provide a firm basis for new interventions to correct salivary gland dysfunction.

Engineering of a Secretory Active Three-Dimensional Lacrimal Gland Construct on the Basis of Decellularized Lacrimal Gland Tissue

Lacrimal gland (LG) insufficiency is a main cause for severe dry eye leading to pain, visual impairment, and eventually loss of sight. Engineering of transplantable LG tissue with secretory capacity is a desirable goal. In this study, a three-dimensional decellularized LG (DC-LG) scaffold with preserved LG morphology was generated by treatment with 1% sodium deoxycholate and DNase solution using porcine LG tissue. To address clinical applicability, the primary in vitro culture of secretory active LG cells from a small tissue biopsy of 1.5 mm diameter was introduced and compared with an established isolation method by enzymatic digestion. Cells from both isolation methods depicted an epithelial phenotype, maintained their secretory capacity for up to 30 days, and exhibited progenitor cell capacity as measured by aldehyde dehydrogenase-1 activity, side population assay, and colony-forming units. Cells from passage 0 were reseeded into the DC-LG and secretory active cells migrated into the tissue. The cells resembled an LG-like morphology and the constructs showed secretory activity. These results demonstrate the possibility of engineering a secretory competent, three-dimensional LG construct using LG cells expanded from a small tissue biopsy and DC-LG as a matrix that provides the native structure and physiological niche for these cells.

Human lacrimal gland regeneration: Perspectives and review of literature

The human lacrimal gland is an essential component of the lacrimal functional unit (LFU). Any perturbation of this unit can lead to the debilitating morbid condition called the dry eye syndrome (DES). The current line of therapy available for dry eye remains supportive and palliative with the patient being dependent on life long and frequent administration of lubricating eye drops. Even advanced therapies like punctual plugs, cyclosporine B administration, and salivary gland auto-transplantation have led to a limited success. Under these scenarios, the option of cell based therapy needs to be explored to provide better and long term relief to these patients. This review gives an overview of the efforts in lacrimal gland regeneration and examines the past and ongoing research in cell based therapies in animals as well as human lacrimal gland cultures. The authors discuss their first of its kind functionally viable human lacrimal gland in vitro culture system from fresh exenteration specimens. A brief overview of research in near future and the potential implications of lacrimal gland regenerative therapies have been discussed.

Establishing human lacrimal gland cultures with secretory function

Purpose

Dry eye syndrome is a multifactorial chronic disabling disease mainly caused by the functional disruptions in the lacrimal gland. The treatment involves palliation like ocular surface lubrication and rehydration. Cell therapy involving replacement of the gland is a promising alternative for providing long-term relief to patients. This study aimed to establish functionally competent lacrimal gland cultures in–vitro and explore the presence of stem cells in the native gland and the established in-vitro cultures.

Methods

Fresh human lacrimal gland from patients undergoing exenteration was harvested for cultures after IRB approval. The freshly isolated cells were evaluated by flow cytometry for expression of stem cell markers ABCG2, high ALDH1 levels and c-kit. Cultures were established on Matrigel, collagen and HAM and the cultured cells evaluated for the presence of stem cell markers and differentiating markers of epithelial (E-cadherin, EpCAM), mesenchymal (Vimentin, CD90) and myofibroblastic (α-SMA, S-100) origin by flow cytometry and immunocytochemistry. The conditioned media was tested for secretory proteins (scIgA, lactoferrin, lysozyme) post carbachol (100 µM) stimulation by ELISA.

Results

Native human lacrimal gland expressed ABCG2 (mean±SEM: 3.1±0.61%), high ALDH1 (3.8±1.26%) and c-kit (6.7±2.0%). Lacrimal gland cultures formed a monolayer, in order of preference on Matrigel, collagen and HAM within 15–20 days, containing a heterogeneous population of stem-like and differentiated cells. The epithelial cells formed ‘spherules’ with duct like connections, suggestive of ductal origin. The levels of scIgA (47.43 to 61.56 ng/ml), lysozyme (24.36 to 144.74 ng/ml) and lactoferrin (32.45 to 40.31 ng/ml) in the conditioned media were significantly higher than the negative controls (p<0.05 for all comparisons).

Conclusion

The study reports the novel finding of establishing functionally competent human lacrimal gland cultures in-vitro. It also provides preliminary data on the presence of stem cells and duct-like cells in the fresh and in-vitro cultured human lacrimal gland. These significant findings could pave way for cell therapy in future.

Tearful relationships? Sex, hormones, the lacrimal gland, and aqueous-deficient dry eye

Sex and the endocrine system exert a significant influence on the physiology and pathophysiology of the lacrimal gland. The purpose of this article is to briefly review the nature and magnitude of these interactions between sex, hormones and lacrimal tissue, and to address how they may relate to the pathogenesis of aqueous-deficient dry eye. Towards this end, this article has a 3-fold approach: first, to summarize the influence of androgens, estrogens, glucocorticoids, mineralocorticoids, retinoic acid, prolactin, alpha-melanocyte stimulating hormone, adrenocorticotropic hormone, luteinizing hormone, follicle-stimulating hormone, growth hormone, thyroid-stimulating hormone, arginine vasopressin, oxytocin, thyroxine, parathyroid hormone, insulin, glucagon, melatonin, human chorionic gonadotropin and cholecystokinin on the structure and function of the lacrimal gland; second, to discuss the mechanism of action of each hormone on lacrimal tissue; and third, to discuss the clinical relevance of the endocrine-lacrimal gland interrelationship, with a particular focus on each hormone's role (i.e. if relevant) in the development of aqueous-tear deficiency.

Sjogrens syndrome as failed local immunohomeostasis: prospects for cell-based therapy

Sjogrens syndrome has been estimated to affect between 0.2% and 2% or more of the population. It is an autoimmune disease with the hallmark histopathology of focal, periductal, and perivascular CD4(+) cell infiltration of the lacrimal and salivary glands. The immunohistopathology is typically associated with severe lacrimal and salivary dysfunctions, which contribute to debilitating ocular surface and oral symptoms. The quality of life of patients with Sjogrens syndrome often is degraded further by serious, multisystemic manifestations, and they are subject to a forty-fold increased risk of developing B cell lymphomas. In normal lacrimal glands, secretory epithelial cells, autoimmune effector lymphocytes, and regulatory lymphocytes can be seen as collaborating to maintain a local immunohomeostasis. The epithelium contributes by secreting immunomodulatory paracrine factors and also by continuously exposing autoantigens, which thereby become available for uptake by professional antigen presenting cells (APCs). Local or systemic perturbations may initiate autoimmune pathophysiology by impairing the replacement of normally-turning-over regulatory cells, by altering epithelial production of immunomodulatory paracrine factors, by inducing intact epithelial cells to begin secreting previously cryptic epitopes (epitopes that previously were not available to bind to major histocompatibility complex (MHC) molecules and so could not be recognized by T cell antigen receptors), and by inducing epithelial cells to begin expressing MHC Class II molecules and presenting formerly cryptic epitopes directly to CD4(+) cells. This process has been modeled ex vivo with mixed cell reactions comprised of isolated epithelial cells and autologous lymphocytes. This development has occurred as studies of anterior chamber-associated immune deviation (ACAID) and other immunoregulatory phenomena have elucidated the origins and functions of several different kinds of regulatory lymphocytes and shown that regulatory lymphocytes can be generated ex vivo. It now is possible to envision strategies for exploiting each possible mode of epithelial autoantigen exposure to produce therapeutic regulatory cells that might be capable of re-establishing normal immunohomeostasis. Consideration of the hypothetical therapies identifies a number of basic questions that warrant investigation.

Traffic of endogenous, transduced, and endocytosed prolactin in rabbit lacrimal acinar cells

The rabbit lacrimal gland undergoes an immunophysiological transformation during pregnancy, reminiscent of that of the mammary gland as it prepares to deliver secretory IgA into the nascent fluid product. The contents of TGF-beta and prolactin (PRL) within ductal epithelial cells increase, and their primary localizations shift from the apical to the basal cytoplasm, suggesting a transformation from exocrine to paracrine secretion. Studies with ex vivo acinar cell models demonstrated that elevated PRL suppresses traffic of secretory proteins into the regulated exocrine apparatus and directs them into a novel, induced, regulated paracrine apparatus [Wang, Y., Chiu, C.T., Nakamura, T., Walker, A.M., Petridou, B., Trousdale M.D., Hamm-Alvarez S.F., Schechter J.E., Mircheff A.K., 2007. Elevated prolactin redirects secretory vesicle traffic in rabbit lacrimal acinar cells. Am. J. Physiol. Endocrinol. Metab. 292, E1122-E1134]. However, it was not clear whether PRL itself entered the induced paracrine apparatus. In the present study, confocal immunofluorescence microscopy revealed that natively expressed PRL and over-expressed PRL co-localized with PRL receptors (PRLR); rab11, a marker for the recycling endosome; gamma-adaptin, a marker for the Golgi complex and trans-Golgi network; and rab7, a marker for the autophagic lysosomal apparatus. Natively expressed, over-expressed, and endocytosed PRL also co-localized with rab4 and rab5A, markers for the early endosome, and with rab3D, a marker for regulated exocrine secretory vesicles. Endocytosed PRL was stored in intact form and released in response to stimulation with carbachol. Subcellular fractionation analysis detected relative excesses of PRL over PRLR in fractions that contained fragments of the recycling endosome and fractions that contained both secretory vesicle fragments and prelysosomal and autolysosomal fragments. EM-gold microscopy demonstrated PRL within small vesicles, consistent with endosomes or secondary lysosomes, and in large vesicles, consistent with regulated secretory vesicles. The secretory vesicles were preponderantly localized in the apical cytoplasm of control cells, and in the basal cytoplasm of PRL over-expressing cells. These results indicate that when lacrimal epithelial cells synthesize PRL, and when they endocytose it from their ambient medium, they traffic it both into the endosomes that constitute the constitutive transcytotic paracrine apparatus and also into regulated secretory vesicles, which are associated with the exocrine apparatus at low PRL levels and with the induced paracrine apparatus at high PRL levels.

Transepithelial bioelectrical properties of rabbit acinar cell monolayers on polyester membrane scaffolds

In our quest to develop a tissue-engineered tear secretory system, we have tried to demonstrate active transepithelial ion fluxes across rabbit lacrimal acinar cell monolayers on polyester membrane scaffolds to evaluate the bioelectrical properties of the cultured cells. Purified lacrimal gland acinar cells were seeded onto polyester membrane inserts and cultured to confluency. Morphological properties of the cell monolayers were evaluated by transmission electron microscopy and immunofluorescence staining for Na(+),K(+)-ATPase and the tight junction-associated protein occludin. Sections revealed cell monolayers with well-maintained epithelial cell polarity, i.e., presence of apical (AP) secretory granules, microvilli, and junctional complexes. Na(+),K(+)-ATPase was localized on both the basal-lateral and apical plasma membranes. The presence of tight cell junctions was demonstrated by a positive circumferential stain for occludin. Bioelectrical properties of the cell monolayers were studied in Ussing chambers under short-circuit conditions. Active ion fluxes were evaluated by inhibiting the short-circuit current (I(sc)) with a Na(+),K(+)-ATPase inhibitor, ouabain (100 microM; basal-lateral, BL), and under Cl(-)-free buffer conditions after carbachol stimulation (CCh; 100 microM). The directional apical secretion of Cl(-) was demonstrated through pharmacological analysis, using amiloride (1 mM; BL) and bumetanide (0.1 mM; BL), respectively. Regulated protein secretion was evaluated by measuring the beta-hexosaminidase catalytic activity in the AP culture medium in response to 100 microM basal CCh. In summary, rabbit lacrimal acinar cell monolayers generate a Cl(-)-dependent, ouabain-sensitive AP --> BL I(sc) in response to CCh, consistent with current models for Na(+)-dependent Cl(-) secretion.

Amniotic membrane as a carrier for lacrimal gland acinar cells

BACKGROUND

The secretion of the lacrimal gland provides 95% of the aqueous tears, which are essential for lubrication, nutrition and protection of the ocular surface. Long-term studies of acinar lacrimal gland cells in vitro are complicated by low proliferation rate and fast loss of cell function on plastic. Aim of this study was to evaluate the growth pattern and the secretory function of lacrimal gland acinar cells on amniotic membrane (AM) in a rabbit model.

METHODS

Lacrimal gland acinar cells from Chinchilla Bastard and New Zealand White rabbits of both sexes were isolated and cultured on denuded amniotic membrane. Cells were analysed by light and electron microscopy. Secretory function was tested by measuring the beta-hexosaminidase activity.

RESULTS

Three days after seeding to the amniotic membrane, the acinar cells had attached to each other and formed small cluster. Cell clusters consisted of 2-5 cell layers, and the cells showed fine granulation in their cytoplasm, typical for secreting cells. Between days 7 and 14 cell clusters increased in size, and acini-like structures with a central lumen were found. Cells showed polarity, with a basal nucleus and apical secretory granules. Between days 21 and 28 acini-like structures were still found inside the cell clusters. Accumulation of secretory material in the central lumen and desmosome formation connecting the apical cell structures was frequently evident. However, the number of cytoplasmatic granules decreased, and on parts of the AM, cell morphology changed to flat, spindle-shaped cells with a small nucleus. Stimulation with carbachol showed a strong beta-hexosaminidase release until day 7, with a decreasing secretory function detectable until day 21.

CONCLUSION

Acinar lacrimal gland cells can be successfully cultured on amniotic membrane up to 28 days, with a secretory response to carbachol up to 21 days. This model may be used for further experimental work, to elucidate cellular mechanisms in normal and diseased lacrimal tissue.

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.

Androgen regulation of gene expression in the mouse lacrimal gland

The objective of this study was to determine the nature and extent of androgen influence on gene expression in the lacrimal gland. Lacrimal glands were obtained from orchiectomized mice that had been treated with testosterone or vehicle for 2 weeks, as well as from testicular feminized mice and their Tabby controls. Samples were pooled according to experiment, processed for the isolation of RNA, and analyzed for differentially expressed mRNAs by using primarily CodeLink Bioarrays, GEM 1 and 2 gene chips and quantitative real-time PCR (qPCR) procedures. Gene chip data were analyzed with GeneSifter.Net software. Our results demonstrate that testosterone regulates the expression of over 2000 genes in the lacrimal gland. Gene ontologies most affected by androgen treatment included those related to cell growth, proliferation and metabolism, cell communication and transport, nucleic acid binding, signal transduction and receptor activities. Our findings also indicate that androgen action may be mediated, at least in part, through classical androgen receptors, and may contribute to the sex-related differences in gene expression of lacrimal tissue. Overall, these results support our working hypothesis that androgen action on the lacrimal gland is mediated primarily through a receptor-associated regulation of gene transcription.

Primary culture of polarized human salivary epithelial cells for use in developing an artificial salivary gland

Therapeutic irradiation for head and neck cancer, and the autoimmune disease Sjogren's syndrome, lead to loss of salivary parenchyma. They are the two main causes of irreversible salivary gland hypofunction. Such patients cannot produce adequate levels of saliva, leading to considerable morbidity. We are working to develop an artificial salivary gland for such patients. A major problem in this endeavor has been the difficulty in obtaining a suitable autologous cellular component. This article describes a method of culturing and expanding primary salivary cells obtained from human submandibular glands (huSMGs) that is serum free and yields cells that are epithelial in nature. These include morphological (light and transmission electron microscopy [TEM]), protein expression (immunologically positive for ZO-1, claudin-1, and E-cadherin), and functional evidence. Under confocal microscopy, huSMG cells show polarization and appropriately localize tight junction proteins. TEM micrographs show an absence of dense core granules, but confirm the presence of tight and intermediate junctions and desmosomes between the cells. Functional assays showed that huSMG cells have high transepithelial electrical resistance and low rates of paracellular fluid movement. Additionally, huSMG cells show a normal karyotype without any morphological or numerical abnormalities, and most closely resemble striated and excretory duct cells in appearance. We conclude that this culture method for obtaining autologous human salivary cells should be useful in developing an artificial salivary gland.

Interaction of EGF family growth factors and neurotransmitters in regulating lacrimal gland secretion

The lacrimal gland is the primary source for the aqueous portion of the tear film. This portion contains water, electrolytes and proteins, which are necessary for the health and maintenance of the cells of the ocular surface. Afferent sensory nerves in the cornea and conjunctiva stimulate efferent parasympathetic and sympathetic nerves in the lacrimal gland. Cholinergic agonists, released from parasympathetic nevres, and norepinephrine, released from sympathetic nerves, are major stimuli of lacrimal gland secretion. These neurotransmitters activate distinct, but overlapping signal transduction pathways leading to lacrimal gland secretion. Other stimuli of lacrimal gland secretion are the EGF family of growth factors. In addition to stimulation of secretion, these growth factors can interact with the cells of the lacrimal gland themselves or with the cells of the ocular surface depending upon the location from which these growth factors are released. This review will focus on the effects of the EGF family of growth factors on the lacrimal gland and their interactions with the pathways stimulated by the neurotransmitters released from nerves.

Novel biphasic traffic of endocytosed EGF to recycling and degradative compartments in lacrimal gland acinar cells

The purpose of this study was to delineate the traffic patterns of EGF and EGF receptors (EGFR) in primary cultured acinar epithelial cells from rabbit lacrimal glands. Uptake of [(125)I]-EGF exhibited saturable and non-saturable, temperature-dependent components, suggesting both receptor-mediated and fluid phase endocytosis. Accumulation of [(125)I] was time-dependent over a 120-min period, but the content of intact [(125)I]-EGF decreased after reaching a maximum at 20 min. Analytical fractionation by sorbitol density gradient centrifugation and phase partitioning indicated that within 20 min at 37 degrees C [(125)I] reached an early endosome, basal-lateral recycling endosome, pre-lysosome, and lysosome. Small components of the label also appeared to reach the Golgi complex and trans-Golgi network. Intact [(125)I]-EGF initially accumulated in the recycling endosome; the content in the recycling endosome subsequently decreased, and by 120 min increased amounts of [(125)I]-labeled degradation products appeared in the pre-lysosomes and lysosomes. Confocal microscopy imaging of FITC-EGF and LysoTrackerRed revealed FITC enriched in a dispersed system of non-acidic compartments at 20 min and in acidic compartments at 120 min. Both confocal immunofluorescence microscopy and analytical fractionation indicated that the intracellular EGFR pool was much larger than the plasma membrane-expressed pool at all times. Cells loaded with [(125)I]-EGF released a mixture of intact EGF and [(125)I]-labeled degradation products. The observations indicate that in lacrimal acinar cells, EGFR and EGF-EGFR complexes continually traffic between the plasma membranes and a system of endomembrane compartments; EGF-stimulation generates time-dependent signals that initially decrease, then increase, EGF-EGFR traffic to degradative compartments.

Interactions of testosterone and all-trans retinoic acid in regulation of androgen receptor expression in rat lacrimal gland

All-trans retinoic acid down-regulates androgen receptor (AR) expression in lacrimal gland acinar cells in culture. The goal of this study was to determine if retinoic acid inhibits androgen-stimulated up-regulation of AR protein and AR mRNA expression in lacrimal glands of orchiectomized rats in vivo. Delivery of androgens to orchiectomized rats was accomplished by subcutaneous implantation of a 25 or 50 mg 21-day slow-release testosterone pellet. Rats were treated with retinoic acid by gastric gavage at 20 mg kg(-1) day(-1). After 7 days of treatment lacrimal glands were removed, AR protein expression in frozen sections was determined by immunohistochemistry and total RNA was probed for AR mRNA expression. Serum testosterone was measured by ELISA and serum retinoic acid was detected by HPLC. Orchiectomy decreases serum testosterone to 17 +/- 8 ng dl(-1), compared to 143 +/- 27 ng dl(-1) in normal rats, and reduces the number of lacrimal acinar cell nuclei expressing ARs to less than 30% of normal. Implantation of testosterone pellets restored lacrimal AR expression, but increased serum testosterone to more than 10 times the normal levels. Retinoic acid failed to inhibit AR expression in rats with high serum testosterone. Therefore a dose-response study was conducted in which testosterone was delivered by injection of a single dose of Depotestosterone at 2.5-200 mg kg(-1). Treatment of orchiectomized rats with a dose of testosterone as low as 2.5 mg kg(-1) resulted in serum testosterone levels of 62 +/- 17 ng dl(-1) and significantly increased lacrimal gland AR expression. Delivery of retinoic acid at 20 or 50 mg kg(-1) day(-1) simultaneously with a 2.5 mg kg(-1) testosterone injection prevented restoration of lacrimal gland AR expression and significantly reduced AR mRNA expression. A pharmacologic dose of retinoic acid inhibits AR expression in lacrimal gland acinar cells in vivo, as well as in vitro. This indicates that effects of retinoic acid and testosterone are antagonistic and suggests that retinoic acid may modulate effects of testosterone on the lacrimal gland.

Down-regulation of androgen receptor expression and inhibition of lacrimal gland cell proliferation by retinoic acid

Androgens and retinoids are known to be involved in control of lacrimal gland function. Because retinoids generally antagonize androgen function it was the purpose of this study to investigate interactions of retinoic acid and androgens in rabbit lacrimal acinar cells in culture by determining effects of retinoic acid on androgen receptor (AR) mRNA expression, AR protein levels and androgen-stimulated cell proliferation. Experiments were conducted using primary rabbit lacrimal acinar cells and a transformed rabbit lacrimal acinar cell line. Exposure of primary lacrimal acinar cells in culture to 10(-10)-10(-6)M all-trans retinoic acid for 4-24hr causes an approximately 50% decrease in AR mRNA expression. Expression of AR protein in primary and transformed rabbit lacrimal acinar cells was confirmed by immunohistochemistry. Exposure of the primary cells to 10(-6)M retinoic acid for 24hr caused a 40% decrease in AR protein levels as determined by measurement of binding of(3) [H]-dihydrotestosterone (DHT) to cells in culture and Scatchard analysis. Exposure to 10(-9)-10(-6)M DHT stimulates proliferation of transformed rabbit lacrimal acinar cells. This effect is receptor mediated since it is blocked by the AR antagonist, flutamide. Proliferation of the lacrimal acinar cells is inhibited by retinoic acid, as compared to control, and retinoic acid also completely inhibits androgen stimulation of cell proliferation. This study supports the hypothesis that androgens play a supportive role in lacrimal gland function. The antagonistic influences of androgens and retinoic acid suggests that, under physiologic conditions there is a balance between the effects of androgens and retinoids in the lacrimal gland. A decrease in androgen levels in a dry eye patient may alter the balance between the effects of these important controllers of gene expression. The antagonistic effect of retinoids on androgens in the lacrimal gland must also be considered when devising pharmaceutical treatments for dye eye.

Expression of IL-10 and TNF-inhibitor genes in lacrimal gland epithelial cells suppresses their ability to activate lymphocytes

PURPOSE

To determine whether the expression of either interleukin-10 (IL-10) or tumor necrosis factor (TNF) inhibitor genes in transduced rabbit lacrimal gland epithelial cells suppresses lymphocyte proliferation in an autologous mixed cell reaction, an apparent in vitro model of autoimmune dacryoadenitis.

METHODS

Purified lacrimal gland epithelial cells, transduced with an adenovirus vector carrying either viral IL-10 or TNF-inhibitor genes, were used to study their effects on the proliferation of autologous lymphocytes as monitored by 3H-thymidine incorporation in a mixed cell reaction. After transduction, both epithelial cells and lymphocytes were cultured separately for 2 days and then epithelial cells were irradiated. Equal numbers of both cell types were then cocultured together for 5 days. Cocultures were pulsed with 3H-thymidine and isotope incorporation was determined. Gene expression was detected by enzyme-linked immunosorbent assay and Western blots.

RESULTS

Lymphocyte proliferation was stimulated by epithelial cells and 3H-thymidine incorporation was significantly greater in these cocultures than in controls. The proliferation was significantly diminished in the presence of transduced cells producing either IL-10 or TNF inhibitor.

CONCLUSIONS

Transduction of lacrimal gland epithelial cells with adenovirus vectors encoding for either IL-10 or TNF-inhibitor proteins leads to expression of functional proteins capable of suppressing lymphocyte proliferation. Thus, lacrimal gland epithelial cells are a plausible target for gene therapy methods meant to produce immunoregulatory proteins.

Growth of purified lacrimal acinar cells in Matrigel raft cultures

The objective of this study was to develop a tissue culture system which closely mimics the in situ lacrimal gland for improved study of lacrimal acinar cell physiology. Highly purified preparations of lacrimal acinar cells from adult female New Zealand White rabbits were isolated and grown in suspension culture in the form of Matrigel 'rafts', i.e., aggregates of acinar cells enclosed within a Matrigel coating. The rafts were seeded onto Matrigel-coated culture plates and their growth was followed for up to 28 days. Immunohistochemistry was used to demonstrate the cellular sites of prolactin (PRL), epidermal growth factor (EGF), basic fibroblast growth factor (FGF-2), secretory component (SC) and major histocompatibility complex class-II molecules (MHC-II) within the acinar cells. By 3 days the cultures contained numerous, well-formed acini enclosed within the Matrigel. The acinar epithelial cells demonstrated histotypic polarity, with large, pale-staining, secretory granules aggregated adjacent to the lumen, and exocytotic release of secretory material into the lumen. From 5-10 days the pale-staining secretory granules decreased in number, while the lumenal contents of the acini increased in staining density. Throughout the culturing period as the pale-staining, secretory granules decreased in number, smaller more densely stained, secretory granules increased in number. The number of cells and size of acinar clusters increased steadily throughout the culturing period, and acini frequently achieved dimensions in excess of 0.5 mm. Increases in the size of acinar clusters were often accompanied by an increase in the size of the lumen. Frequently the lumen and its contents bulged asymmetrically towards one edge of the acinus. Immunhistochemistry demonstrated PRL and EGF within the lumens and within the apical cytoplasm of the acinar cells. Acini were strongly immunopositive for SC throughout the 28 day culture period, whereas immunopositivity for MHC-II molecules was strong initially, but diminished dramatically by 21 days. Immunostaining for FGF-2 was most intense on days 1 and 3, with staining throughout the cytoplasm, but became progressively more localized to the periphery of the acini as the culture period lengthened. In cultures of 1-28 days duration, Western blots of cell lysates demonstrated a major band (approximately 40 kDa) for PRL in 3-28 day preparations; a major band (approximately 80 kDa) for SC in 3 day and 7 day preparations that decreased in intensity in 14-28 day preparations; and a major band (approximately 23 kDa) for MHC-II protein in 1-21 day preparations that decreased in intensity in 28 day preparations. Lysosomes increased in number with time in culture, becoming a dominant cytoplasmic feature in 21 and 28 day cultures. Carbachol stimulation of 4 day rafts resulted in increased release of beta-hexosaminidase and SC from the rafts. The authors conclude that Matrigel rafts containing purified lacrimal gland acinar cells offer a highly advantageous system for study of lacrimal acinar cell function and one that correlates well with the in situ gland.

cDNA and genomic cloning of lacritin, a novel secretion enhancing factor from the human lacrimal gland

Multiple extracellular factors are hypothesized to promote the differentiation of unstimulated and/or stimulated secretory pathways in exocrine secretory cells, but the identity of differentiation factors, particularly those organ-specific, remain largely unknown. Here, we report on the identification of a novel secreted glycoprotein, lacritin, that enhances exocrine secretion in overnight cultures of lacrimal acinar cells which otherwise display loss of secretory function. Lacritin mRNA and protein are highly expressed in human lacrimal gland, moderately in major and minor salivary glands and slightly in thyroid. No lacritin message or protein is detected elsewhere among more than 50 human tissues examined. Lacritin displays partial similarity to the glycosaminoglycan-binding region of brain-specific neuroglycan C (32 % identity over 102 amino acid residues) and to the possibly mucin-like amino globular region of fibulin-2 (30 % identity over 81 amino acid residues), and localizes primarily to secretory granules and secretory fluid. The lacritin gene consists of five exons, displays no alternative splicing and maps to 12q13. Recombinant lacritin augments unstimulated but not stimulated acinar cell secretion, promotes ductal cell proliferation, and stimulates signaling through tyrosine phosphorylation and release of calcium. It binds collagen IV, laminin-1, entactin/nidogen-1, fibronectin and vitronectin, but not collagen I, heparin or EGF. As an autocrine/paracrine enhancer of the lacrimal constitutive secretory pathway, ductal cell mitogen and stimulator of corneal epithelial cells, lacritin may play a key role in the function of the lacrimal gland-corneal axis.