Corneal insult affects the production and distribution of FGF-2 within the lacrimal gland

Transcriptome from opaque cornea of Fanconi anemia patient uncovers fibrosis and two connected players

Congenital corneal opacities (CCO) are a group of blinding corneal disorders, where the underlying molecular mechanisms are poorly understood. Phenotyping through specialized imaging and histopathology analysis, together with assessment of key transcriptomic changes (including glycosaminoglycan metabolic enzymes) in cornea(s) with CCO from a case of Fanconi anemia is the approach taken in this study to identify causal mechanisms. Based on our findings, we propose a novel mechanism and two key players contributing to CCO.

Human Serum Eye Drops in Eye Alterations: An Insight and a Critical Analysis

Human serum contains a physiological plethora of bioactive elements naturally released by activated platelets which might have a significant effect on the regeneration of corneal layers by stimulating the cell growth. This mechanism supported the use of human serum eye drops in some ocular diseases associated with dystrophic changes and alterations of the tear film, such as persistent corneal epithelial defects and dry eye syndrome. We focused our effort on potential benefits and limitations of the use of human serum eye drops when conventional therapies failed. We reviewed the recent literature by reporting published studies from 2010 to 2014. Despite the limited evaluated study populations, most of the clinical studies have confirmed that serum eye drop therapy is effective in corneal healing by reducing ocular symptom, particularly during the short-term follow-up. In addition, three recent published studies have shown the efficacy of the serum eye drop therapy in comparison to traditional ones in intractable patients. Besides, reported ongoing clinical studies confirmed the open debate regarding the use of biologic tools for cornea regeneration. Results from these studies might open novel challenges and perspectives in the therapy of such refractory patients.

Myoepithelial Cells: Their Origin and Function in Lacrimal Gland Morphogenesis, Homeostasis, and Repair

Lacrimal gland (LG) is an exocrine tubuloacinar gland that secretes the aqueous layer of the tear film. LG epithelium is composed of ductal, acinar, and myoepithelial cells (MECs) bordering the basal lamina and separating the epithelial layer from the extracellular matrix. Mature MECs have contractile ability and morphologically resemble smooth muscle cells; however, they exhibit features typical for epithelial cells, such as the presence of specific cytokeratin filaments. Increasing evidence supports the assertion that myoepithelial cells (MECs) play key roles in the lacrimal gland development, homeostasis, and stabilizing the normal structure and polarity of LG secretory acini. MECs take part in the formation of extracellular matrix gland and participate in signal exchange between epithelium and stroma. MECs have a high level of plasticity and are able to differentiate into several cell lineages. Here, we provide a review on some of the MEC characteristics and their role in LG morphogenesis, maintenance, and repair.

Glycoprotein C of herpes simplex virus type 1 is required to cause keratitis at low infectious doses in intact rabbit corneas

PURPOSE

To determine whether the herpes simplex virus type 1 (HSV-1) viral glycoprotein C (gC) plays a role in induction of keratitis in unscarified and scarified rabbit eyes.

MATERIALS AND METHODS

A gC deletion mutant (DeltagC) was constructed and then rescued back to wild type (wt) for use as a control. Following ocular infection with each virus in rabbit eyes, with or without prior corneal scarification, keratitis was compared.

RESULTS

At low infection doses of 2 x 10(3) and 2 x 10(4) plaque-forming units (PFU)/eye, in unscarified cornea, DeltagC produced significantly less keratitis than did wt virus (p = 0.007 and 0.03, respectively). In contrast, the keratitis induced by DeltagC was similar to that induced by the wt virus (p > 0.60) in scarified cornea. At high infection dose (2 x 10(5) PFU/eye), keratitis induced by DeltagC was similar in scarified and unscarified cornea, and the severity of disease was similar to that seen in scarified eyes at the low-dose DeltagC infections. Interestingly, although DeltagC induced keratitis with or without corneal scarification at high infection doses, the severity of disease was significantly less than that induced by wt infection. At all infection doses, keratitis induced by wt infection was similar in scarified and unscarified eyes.

CONCLUSIONS

These results suggest that (1) at low infection doses, in unscarified corneas, gC is required for HSV-1 induced keratitis; (2) corneal scarification prior to infection can circumvent the need for gC at low doses, but (3) at higher doses, gC is required for wild-type levels of keratitis even in scarified cornea.

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.

Growth Factors in the Tear Film: Role in Tissue Maintenance, Wound Healing, and Ocular Pathology

Numerous biologically active growth factors are secreted by the lacrimal gland and distributed via the tears over the ocular surface, where they affect cellular proliferation, migration, differentiation, and survival. The role of growth factors and their receptors in maintenance of tissue homeostasis and wound healing continues to be elucidated, and the effect of growth factor imbalances in ocular surface diseases is just beginning to be understood. For instance, in eyes with ocular surface diseases, including conjunctivitis, corneal erosion, keratitis, and corneal ulcers, epidermal growth factor release rates have been shown to be significantly lower than in normal eyes during reflex tearing. Future research into the mechanisms of dry eye disease will focus on reasons for decreased tear and growth factor production in the neuronal reflex loop or the acinar lacrimal gland cells. Animal models to test therapeutic approaches must be developed.

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.

Binding inhibition of angiogenic factors by heparan sulfate proteoglycans in aqueous humor: potential mechanism for maintenance of an avascular environment

Aqueous humor is a clear fluid, primarily a blood filtrate, which circulates through the anterior chamber of the eye and bathes the cornea. We explored the possibility that components in the aqueous humor play a direct part in maintaining the avascular environment of the cornea. We report here that heparan sulfate proteoglycan (HSPG) was found in bovine aqueous humor and that it directly inhibits binding of basic fibroblast growth factor and vascular endothelial growth factor to cell-surface heparan sulfate. We demonstrate that this holds true for all heparin binding proteins tested but not for epidermal growth factor, which does not bind heparin. Furthermore, we show, with mathematical modeling, that the concentration of HSPG in aqueous humor (approximately 4 microg/ml), when combined with the clearance of aqueous humor from the eye due to circulation, is sufficient to block the binding of heparin binding growth factors to corneal endothelium. This mechanism suggests a physiological process to control bioavailability of angiogenic growth factors in the cornea.

Regulatory pathways in lacrimal gland epithelium

Tears are a complex fluid that continuously cover the exposed surface of the eye, namely the cornea and conjunctiva. Tears are secreted in response to the multitude of environmental stresses that can harm the ocular surface such as cold, mechanical stimulation, physical injury, noxious chemicals, as well as infections from various organisms. Tears also provide nutrients and remove waste from cells of the ocular surface. Because of the varied function of tears, tears are complex and are secreted by several different tissues. Tear secretion is under tight neural control allowing tears to respond rapidly to changing environmental conditions. The lacrimal gland is the main contributor to the aqueous portion of the tear film and the regulation of secretion from this gland has been well studied. Despite multiple redundencies in pathways to stimulate secretion from the lacrimal gland, defects can occur resulting in dry eye syndromes. These diseases can have deleterious effects on vision. In this review, we summarize the latest information regarding the regulatory pathways, which control secretion from the lacrimal gland, and their roles in the pathogenesis of dry eye syndromes.

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.