Androgen influence on gene expression in the meibomian gland

Dry eye and dry skin - is there a connection?

AIM

To enquire whether patients with dry eye symptoms also report dry skin, whether their perception could be corroborated with objective measurement, and whether dry eye disease might be suspected based on patients' complaints.

METHODS

This cross-sectional study included 50 subjects, 25 with and 25 without dry eye symptoms. Schein questionnaire was used to determine the severity of dry eye symptoms. Ocular signs were assessed by monitoring conjunctival hyperemia, ocular surface staining, meibomian gland expression, tear film lipid layer thickness, tear break-up time, lid parallel conjunctival folds, Schirmer test, and meibometry. Skin dryness was assessed by noting patients' self-perception of their facial skin dryness and measured by sebumeter.

RESULTS

Subjects without dry eye symptoms had self-reported oilier facial skin than those with dry eye symptoms (p < .001). Sebumetry scores measured on the forehead and cheek were significantly higher in subjects without dry eye symptoms than dry eye subjects (p = .003). After adjustment for age and gender in a logistic regression analysis, dry eye was independently and significantly associated with dry skin (AOR 0.69, p = .040), higher LIPCOF score of both eyes (AOR 2.28, p = .028), lower sebumetry score of the forehead (AOR 0.98, p = .041) and cheek (AOR 0.98, p = .041), and shorter TBUT score after gland expression (AOR 0.90, p = .018).

CONCLUSION

This study showed that ocular dryness was subjectively and objectively positively correlated to facial skin dryness. Patients reliably described their skin condition. People with dry facial skin also had drier eyes.

Meibomian Gland Assessment in Routine Ophthalmology Practice

This cross-sectional study aimed to investigate the connection between meibomian gland (MG) excreta quantity and quality after MG expression (MGX), dry eye disease (DED) symptoms, and objective DED signs and to clarify the relationship between dry eye and MG function in DED pathophysiology. The study included 200 subjects, 100 with and 100 without dry eye symptoms. Schein questionnaire was used to determine the severity of dry eye symptoms and self-reported skin type for facial skin dryness self-evaluation. Objective dry eye signs were assessed by monitoring conjunctival hyperemia, lid parallel conjunctival folds (LIPCOF), tear break-up time (TBUT), fluorescein surface staining and digital MGX. Subjects with DED symptoms had significantly lower MG quantity scores than healthy controls (p < 0.001). Meibum quality and quantity scores significantly correlated with female gender (p = 0.002), Schein questionnaire score (p < 0.001), fluorescein corneal staining score (p = 0.019), self-reported skin type (p < 0.001), TBUT (p < 0.001) and LIPCOF (p = 0.041). After adjustment for age and gender in a logistic regression analysis, dry eye was independently and significantly associated with self-reported skin type (OR 0.73, p < 0.001), LIPCOF (OR 1.04, p < 0.001), fluorescein corneal staining (OR 1.05, p = 0.019), TBUT (OR 0.77, p < 0.001) and meibum quantity score (OR 0.59, p < 0.001). Dry eye symptoms and objective signs correlated well in this study. MGX discriminated between the subjects with and without DED symptoms and was associated with other objective DED signs. Results showed a significant association between meibum quality and quantity, MG function, DED and facial skin dryness self-perception. This paper established a correlation between dry eye symptoms caused by MG dysfunction and dry skin, which can help general health practitioners consider dry eye as a cause of chronic eye complaints with patients who report dry skin.

Meibomian Gland Dysfunction: What Have Animal Models Taught Us?

Studies have estimated that currently 344 million people worldwide and 16.4 million adults in the US have some form of dry eye disease (DED). It is believed that approximately 70% of DED cases are due to some form of evaporative dry eye, for which Meibomian gland dysfunction (MGD) is the major cause. Unfortunately, currently there is no effective treatment for MGD, and solely palliative care is available. Given the importance of MGD in DED, there has been a growing interest in studying Meibomian gland development, homeostasis and pathology, and, also, in developing therapies for treating and/or preventing MGD. For such, animal models have shown to be a vital tool. Much of what is known today about the Meibomian gland and MGD was learnt from these important animal models. In particular, canine and rabbit models have been essential for studying the physiopathology and progression of DED, and the mouse model, which includes different knockout strains, has enabled the identification of specific pathways potentially involved in MGD. Herein, we provide a bibliographic review on the various animal models that have been used to study Meibomian gland development, Meibomian gland homeostasis and MGD, primarily focusing on publications between 2000 and 2020.

Dihydrotestosterone suppression of proinflammatory gene expression in human meibomian gland epithelial cells

PURPOSE

We discovered that dihydrotestosterone (DHT) decreases the ability of lipopolysaccharide, a bacterial toxin, to stimulate the secretion of leukotriene B4, a potent proinflammatory mediator, by immortalized human meibomian gland epithelial cells (IHMGECs). We hypothesize that this hormone action reflects an androgen suppression of proinflammatory gene activity in these cells. Our goal was to test this hypothesis. For comparison, we also examined whether DHT treatment elicits the same effect in immortalized human corneal (IHC) and conjunctival (IHConj) ECs.

METHODS

Differentiated cells were cultured in media containing vehicle or 10 nM DHT. Cells (n = 3 wells/treatment group) were then processed for RNA isolation and the analysis of gene expression by using Illumina BeadChips, background subtraction, cubic spline normalization and Geospiza software.

RESULTS

Our results demonstrate that DHT significantly suppressed the expression of numerous immune-related genes in HMGECs, such as those associated with antigen processing and presentation, innate and adaptive immune responses, chemotaxis, and cytokine production. DHT also enhanced the expression of genes for defensin β1, IL-1 receptor antagonist, and the anti-inflammatory serine peptidase inhibitor, Kazal type 5. In contrast, DHT had no effect on proinflammatory gene expression in HCECs, and significantly increased 33 gene ontologies linked to the immune system in HConjECs.

CONCLUSIONS

Our findings support our hypothesis that androgens suppress proinflammatory gene expression in IHMGECs. This hormone effect may contribute to the typical absence of inflammation within the human meibomian gland.

Cyclic Change of Fatty Acid Composition in Meibum During the Menstrual Cycle

Purpose

To evaluate the fatty acid (FA) composition in the meibum of pre- and postmenopausal women and age-matched men.

Methods

This prospective study involved 24 healthy subjects; six premenopausal women in their 30s with a regular menstrual cycle (young-female [yF] group), six postmenopausal women in their 60s (elderly-female [eF] group), and 12 age-matched men (i.e., young-male [yM] and elderly-male [eM] groups, respectively). The menstrual cycle was divided into six phases (phase I–VI). Meibum was obtained from the meibomian gland orifices via a Daviel spoon, and its FA composition was then analyzed via gas chromatography mass spectrometry (GC-MS). Principal component analysis (PCA) was performed on the GC-MS results.

Results

The mean FA composition of all subjects was 40% saturated FAs (SFA) and 60% unsaturated FAs (UFAs). The PCA results of all groups indicated two categories (PC1 [77.5%] and PC2 [12.4%]); one consisting of yF-group samples of mainly phase II and III and the other consisting of the yF-group samples of the rest of the cycle, as well as from eF-group, yM-group, and eM-group samples. Each group had a distinctive nature. The FAs that most contributed to PC1 were C_14:0, C_16:0, and C_18:0 in a positive correlation, and C_18:1n9 in a negative correlation.

Conclusions

FA composition noticeably changes during the menstrual cycle and is somewhat affected by sex and age. The ratio of SFAs (C_16:0, C_18:0) to mono-UFAs (C_18:1n9) in the FA composition might have an impact on the lipid quality of meibum, thus suggesting alteration of its melting temperature and viscosity.

Morphology and Function of Meibomian Glands and Other Tear Film Parameters in Junior High School Students

Purpose:

We measured tear film parameters, including the morphology and function of meibomian glands, in junior high school students at 15 years of age.

Methods:

A total of 111 eyes of 111 students (56 males and 55 females) were enrolled in the study. The ocular symptom score (0–14), after-school study time, lipid layer thickness (LLT) of the tear film, partial blink rate, lid margin abnormalities (0–4), tear film breakup time, corneal and conjunctival epithelial damage (fluorescein staining score, 0–9), meiboscore as determined by noncontact meibography (0–6), Schirmer test value, and meibum grade (0–3) were determined. The relationships between parameters were evaluated with the Spearman correlation coefficient (ρ).

Results:

The meiboscore was 2.8 ± 1.2, and the meibum grade was 1.8 ± 1.2. The meiboscore significantly correlated with the meibum grade (ρ = 0.272, P = 0.004), Schirmer test value (ρ = −0.220, P = 0.021), and LLT (ρ = −0.264, P = 0.005). The breakup time significantly correlated with LLT (ρ = 0.261, P = 0.006), meibum grade (ρ = −0.338, P < 0.001), and fluorescein staining score (ρ = −0.214, P = 0.025). The partial blink rate significantly correlated with the Schirmer test value (ρ = −0.240, P = 0.011). The meiboscore (P < 0.001) and meibum grade (P = 0.032) were significantly greater in males than in females.

Conclusions:

The morphology and function of meibomian glands are altered even at 15 years of age, with the changes being more prominent in males than in females.

Local synthesis of sex hormones: are there consequences for the ocular surface and dry eye?

Sex hormones are associated with the physiology and pathophysiology of almost all organs in the body, as well as most diseases. Interest in the associations between sex hormones and ocular tissues has increased in recent years. Androgens may have a positive effect on dry eye, whereas the effects of oestrogen on ocular conditions remain unclear. Intracrinology, the local synthesis and metabolism of hormones that is unique to humans, is of relevance to the eye and may help to explain why studies of the relationship between oestrogens and dry eye signs and symptoms are inconclusive. Knowledge of the pathways of hormone formation and metabolism is crucial to understanding the pathogenesis of ocular disease including dry eye. This review examines the mechanisms of steroidal sex hormone biosynthesis and reviews the significance of locally produced sex hormones, with a focus on ocular surface tissues. Much of the current literature is based on animal studies, which may not be transferable to humans due to the absence of intracrine production in animals. A large proportion of the human studies investigate systemic hormone levels rather than local levels. There is subsequently a need for additional studies to provide a better understanding of the local production of sex hormones within the human eye and ocular surface and to clarify the relationships between ocular levels of sex hormones and conditions including dry eye.

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.

Sex hormones and the dry eye

The greater prevalence of dry eye in women compared to men suggests that sex hormones may have a role in this condition. This review aims to present evidence for how sex hormones may affect the ocular structures involved in the production, regulation and maintenance of the normal tear film. It is hypothesised that hormone changes alter the homeostasis of the ocular surface and contribute to dry eye. Androgens impact on the structure and function of the meibomian and lacrimal glands and therefore androgen deficiency is, at least in part, associated with the aetiology of dry eye. In contrast, reports of the effects of oestrogen and progesterone on these ocular structures and on the conjunctiva are contradictory and the mechanisms of action of these female-specific sex hormones in the eye are not well understood. The uncertainty of the effects of oestrogen and progesterone on dry eye symptoms is reflected in the controversial relationship between hormone replacement therapy and the signs and symptoms of dry eye. Current understanding of sex hormone influences on the immune system suggests that oestrogen may modulate a cascade of inflammatory events, which underlie dry eye.

Meibography: A review of techniques and technologies

Meibomian glands play a significant role in tear production by contributing lipids to the superficial tear film.(1) Dysfunction of the meibomian glands destabilizes tears resulting in evaporative dry eye.(2,3) Historically, the meibomian glands were assessed in an ex vivo fashion through histologic studies. However, innovations in ocular imaging have advanced significantly in recent decades to include meibography. Meibography is an imaging study developed 35 years ago exclusively for the purpose of observing the morphology of meibomian glands in vivo.(4,5) In this review of meibography, we briefly describe the etiology of meibomian gland dysfunction and then discuss various meibography techniques, technologies, and methods of image analysis. We close with a review of the literature, crediting various studies for the significant contributions made toward our current understanding of the meibomian glands.

Dry eye syndrome in aromatase inhibitor users

BACKGROUND

Aromatase inhibitors are frequently used as an adjuvant therapy in the treatment of breast cancer. We observed that several patients taking aromatase inhibitors presented with severe dry eye symptoms, and we investigated whether there is a relationship between aromatase inhibitors and dry eyes in these patients.

DESIGN

Retrospective chart review.

PARTICIPANTS

Forty-one women.

METHODS

A computerized search of health records was performed to identify patients using anastrazole, letrozole and exemestane seen by the Cornea Service from August 2008 to March 2011. The results were compared with age-matched controls.

MAIN OUTCOME MEASURES

Ocular surface changes among aromatase inhibitors users.

RESULTS

Of the 41 women, 39 were Caucasians. Thirty-nine patients had breast cancer (95%), one patient had ovarian cancer (2.5%) and one had an unknown primary cancer. Mean age was 68 ± 11.3 years (range 47-95). Most common presenting symptoms were blurred vision in 28 (68%) patients, irritation/foreign body sensation in 12 (29%) patients, redness in 9 (22%) patients, tearing in 6 (22%) patients and photosensitivity in 2 (5%) patients. Mean Schirmer's test measurement was 11 ± 5.8 mm (range 0.5-20 mm). Blepharitis was noted in 68 of 82 eyes (73%), decreased or poor tear function in 24 eyes (29%), conjunctival injection in 18 eyes (22%) and superficial punctate keratitis in 12 eyes (29%). Among an age-matched population (45-95 years), dry eye syndrome was found in only 9.5% of patients.

CONCLUSIONS

Because the prevalence of ocular surface disease signs and symptoms appears to be higher in study group than control patients, aromatase inhibitors might be a contributing factor to the dry eye symptoms.

[Meibomian glands. Part I: anatomy, embryology and histology of the Meibomian glands]

The Meibomian glands are large sebaceous glands that are located as separate gland strands in parallel arrangement within the tarsal plates of the eyelids. Their oily product (meibum) is secreted by a holocrine mechanism during which the secretory cells (meibocytes) are completely transformed into the meibum after synthesis and accumulation of lipids. After production in the gland acini, meibum is transported through the ductal system via the connecting duct (ductule) and the central duct towards the orifice at the free lid margin close to the inner lid border. The embryological development of the Meibomian glands takes place during the differentiation of the eyelids in the sealing phase of the eyelids. They are not directly associated with hair follicles but share important similarities in embryology, structure and keratinization potency with the cilia. Similar to the sebaceous glands Meibomian glands are regulated via sex hormones and androgens have a supporting function whereas estrogens act antagonistically. However, in contrast to other sebaceous glands they also have a distinct innervation, apart from sympathetic and sensory primarily by parasympathetic fibers that share the innervation pattern of the lacrimal glands. The anatomy, embryology and histology of the Meibomian glands are explained here, mainly with respect to humans, in an extensive review.

Age-related changes in the meibomian gland

The purpose of this study was to characterize the age-related changes of the mouse meibomian gland. Eyelids from adult C57Bl/6 mice at 2, 6, 12 and 24 months of age were stained with specific antibodies against peroxisome proliferator activated receptor gamma (PPARgamma) to identify differentiating meibocytes, Oil Red O (ORO) to identify lipid, Ki67 nuclear antigen to identify cycling cells, B-lymphocyte-induced maturation protein-1 (Blimp1) to identify potential stem cells and CD45 to identify immune cells. Meibomian glands from younger mice (2 and 6 months) showed cytoplasmic and perinuclear staining with anti-PPARgamma antibodies with abundant ORO staining of small, intracellular lipid droplets. Meibomian glands from older mice (12 and 24 months) showed only nuclear PPARgamma localization with less ORO staining and significantly reduced acinar tissue (p < 0.04). Acini of older mice also showed significantly reduced (p < 0.004) numbers of Ki67 stained nuclei. While Blimp1 appeared to diffusely stain the superficial ductal epithelium, isolated cells were occasionally stained within the meibomian gland duct and acini of older mice that also stained with CD45 antibodies, suggesting the presence of infiltrating plasmacytoid cells. These findings suggest that there is altered PPARgamma receptor signaling in older mice that may underlie changes in cell cycle entry/proliferation, lipid synthesis and gland atrophy during aging. These results are consistent with the hypothesis that mouse meibomian glands undergo age-related changes similar to those identified in humans and may be used as a model for age-related meibomian gland dysfunction.

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.

Association between meibomian gland changes and aging, sex, or tear function

PURPOSE

To study changes in the lid margin and meibomian glands and their association with aging, sex, and tear function.

METHODS

We examined 354 eyes in 177 subjects (76 men and 101 women; 21-93 years; mean age, 63.0 +/- 14.3 years) with no ocular symptoms or ocular surface disorders. Anatomic changes in the lid margin were studied using slit-lamp biomicroscopy. Meibomian gland function and morphology were evaluated on the basis of meibum expression and meibography, respectively. Tear function and ocular surface epithelium were assessed with the Schirmer test, by tear film break-up time, and with a fluorescein staining test.

RESULTS

Eyes with abnormal lid margin anatomy, hyposecretion of meibum, and meibomian gland dropout were seen in 26 (7.3%), 46 (12.4%), and 68 eyes (18.6%), respectively, with a significant association between each finding and aging (P = <0.0001, 0.0498, and <0.0001, respectively). In patients < or =69 years of age, no significant association was found between meibomian gland-related findings and sex. However, a high incidence of abnormal lid margin and gland dropout was noted in men > or =70 years of age compared with women. No significant association was found between changes in the lid margin and meibomian glands and tear function in patients > or =40 years of age.

CONCLUSION

Among symptom-free subjects, we found that changes in the lid margin and meibomian glands were closely related to aging. Among elderly subjects, changes in the anatomic lid margin and meibomian gland morphology were observed more frequently in men than in women. Tear function showed no association with either changes in the lid margin or function of the meibomian glands.

Sex-related effect on gene expression in the mouse meibomian gland

PURPOSE

Sex-related differences have been identified in the anatomy and physiology of the meibomian gland. We hypothesize that these differences are due, at least in part, to variations in gene expression. This study's objective was to determine whether sex-related differences do exist in meibomian gland gene expression. We also sought to elucidate whether such differences, if any, might be (a) analogous to those known to occur in the lacrimal gland and (b) due to the effect of sex steroids.

METHODS

Meibomian glands were obtained from young adult male and female BALB/c mice (n=7 to 15 mice per sex per experiment), pooled according to sex and processed for the isolation of RNA. Samples were evaluated for differentially expressed mRNAs by using CodeLink Bioarrays and GEM 1 and 2 gene chips. Bioarray data were analyzed with GeneSifter. Net software and also compared with microarray data in GEO and GeneSifter databases.

RESULTS

Our results demonstrate that sex has a significant influence on the expression of 164 genes in the mouse meibomian gland. These genes are involved in a broad spectrum of biological processes, molecular functions, and cellular components, including such activities as metabolism, catalysis, cell growth and maintenance, membrane architecture, nucleic acid binding, transcription, and signal transduction. In addition, the nature of the sex-related variations in meibomian gland gene expression is quite different from those in the lacrimal gland and appear to be mediated in part by the action of androgens, but not estrogens or progestins.

CONCLUSIONS

These findings support our hypothesis that sex-related differences exist in gene expression of the meibomian gland.

Androgen deficiency, Meibomian gland dysfunction, and evaporative dry eye

OBJECTIVE

We have recently discovered that women with primary and secondary Sjögren's syndrome are androgen-deficient. We hypothesize that this hormone insufficiency contributes to the meibomian gland dysfunction, tear film instability, and evaporative dry eye that are characteristic of this autoimmune disorder. If our hypothesis is correct, we predict: (1) that androgens regulate meibomian gland function, control the quality and/or quantity of lipids produced by this tissue, and promote the formation of the tear film's lipid layer; and (2) that androgen deficiency, due to an attenuation in androgen synthesis (e.g., during Sjögren's syndrome, menopause, aging, complete androgen-insensitivity syndrome [CAIS] and anti-androgen use), will lead to meibomian gland dysfunction and evaporative dry eye. The following studies were designed to test these predictions.

METHODS

Experimental procedures included clinical studies, animal models, and histological, biochemical, molecular biological, and biomedical engineering techniques.

RESULTS

Our results demonstrate that: (1) androgens regulate the meibomian gland. This tissue contains androgen receptor mRNA, androgen receptor protein within acinar epithelial cell nuclei, and Types 1 and 2 5alpha-reductase mRNAs. Moreover, androgens appear to modulate lipid production and gene expression in mouse and/or rabbit meibomian glands; and (2) androgen deficiency may lead to meibomian gland dysfunction, altered lipid profiles in meibomian gland secretions, tear film instability, and evaporative dry eye. Thus, we have found that anti-androgen therapy in men is associated with meibomian gland disease, a decreased tear film breakup time, and functional dry eye. Furthermore, we have discovered that androgen receptor dysfunction in women with CAIS is associated with meibomian gland changes and a significant increase in the signs and symptoms of dry eye. Of interest, we have also found that androgen deficiency is associated with significant and striking alterations in the neutral and polar lipid patterns of human meibomian gland secretions.

CONCLUSIONS

Our findings show that the meibomian gland is an androgen target organ and that androgen deficiency may promote meibomian gland dysfunction and evaporative dry eye. Overall, these results support our hypothesis that androgen deficiency may be an important etiologic factor in the pathogenesis of evaporative dry eye in women with Sjögren's syndrome.