Hormonal modulation of tear volume in the rat

The miR-183/96/182 cluster regulates sensory innervation, resident myeloid cells and functions of the cornea through cell type-specific target genes

The conserved miR-183/96/182 cluster (miR-183C) is expressed in both corneal resident myeloid cells (CRMCs) and sensory nerves (CSN) and modulates corneal immune/inflammatory responses. To uncover cell type-specific roles of miR-183C in CRMC and CSN and their contributions to corneal physiology, myeloid-specific miR-183C conditional knockout (MS-CKO), and sensory nerve-specific CKO (SNS-CKO) mice were produced and characterized in comparison to the conventional miR-183C KO. Immunofluorescence and confocal microscopy of flatmount corneas, corneal sensitivity, and tear volume assays were performed in young adult naïve mice; 3' RNA sequencing (Seq) and proteomics in the trigeminal ganglion (TG), cornea and CRMCs. Our results showed that, similar to conventional KO mice, the numbers of CRMCs were increased in both MS-CKO and SNS-CKO vs age- and sex-matched WT control littermates, suggesting intrinsic and extrinsic regulations of miR-183C on CRMCs. The number of CRMCs was increased in male vs female MS-CKO mice, suggesting sex-dependent regulation of miR-183C on CRMCs. In the miR-183C KO and SNS-CKO, but not the MS-CKO mice, CSN density was decreased in the epithelial layer of the cornea, but not the stromal layer. Functionally, corneal sensitivity and basal tear volume were reduced in the KO and SNS-CKO, but not the MS-CKO mice. Tear volume in males is consistently higher than female WT mice. Bioinformatic analyses of the transcriptomes revealed a series of cell-type specific target genes of miR-183C in TG sensory neurons and CRMCs. Our data elucidate that miR-183C imposes intrinsic and extrinsic regulation on the establishment and function of CSN and CRMCs by cell-specific target genes. miR-183C modulates corneal sensitivity and tear production through its regulation of corneal sensory innervation.

Histochemical Comparison of Human and Rat Lacrimal Glands: Implications for Bio-Engineering Studies

Purpose

The purpose of this study was to determine whether rodent lacrimal glands (LGs) represent a suitable surrogate for human tissue in bio-engineering research, we undertook a meticulous histological and histochemical comparison of these two tissues.

Methods

Histological techniques and immunohistochemistry were used to compare the structure of adult human and rat LG tissues and the expression of key functional tissue elements.

Results

Compared with humans, the rat LG is comprised of much more densely packed acini which are devoid of an obvious central lumen. Myoepithelial, fibroblasts, dendritic cells, T cells, and putative progenitor cells are present in both tissues. However, human LG is replete with epithelium expressing cytokeratins 8 and 18, whereas rat LG epithelium does not express cytokeratin 8. Furthermore, human LG expresses aquaporins (AQPs) 1, 3, and 5, whereas rat LG expresses AQPs 1, 4, and 5. Additionally, mast cells were identified in the rat but not the human LGs and large numbers of plasma cells were detected in the human LGs but only limited numbers were present in the rat LGs.

Conclusions

The cellular composition of the human and rat LGs is similar, although there is a marked difference in the actual histo-architectural arrangement of the tissue. Further variances in the epithelial cytokeratin profile, in tissue expression of AQPs and in mast cell and plasma cell infiltration, may prove significant.

Translational Relevance

The rat LG can serve as a useful surrogate for the human equivalent, but there exist specific tissue differences meaning that caution must be observed when translating results to patients.

Effects of hormonal contraceptives on dry eye disease: a population-based study

BACKGROUND

Hormonal contraceptives (HCs) are a known risk factor for dry eye disease (DED), yet the relationship between HCs use and DED in women of child-bearing age remains debatable. The aim of this study was to determine the association between HCs and DED in females of reproductive age.

METHODS

This was a retrospective cohort study using data from IQVIA's electronic medical record (IQVIA, USA). 4,871,504 women (age 15-45) between 2008 and 2018 were followed to the first diagnosis of DED as defined by an ICD-9/10 code. DED cases also required at least two prescriptions of cyclosporine or lifitegrast topical drops within 60 days of the first code. The date of the first code was designated as the index date. Regular HCs users needed to have at least two prescriptions in both the first year and second year prior to the index date. For each case, five controls were selected and matched to cases by age and follow-up time. A conditional logistic regression model was used to adjust for confounders of DED and to calculate odds ratios (ORs).

RESULTS

HCs users were at a higher risk for DED than non-users. Regular users of HCs were more likely to develop DED (ORs = 2.73, 95% CI [2.21-3.73]) than irregular users. Those who used a greater number of HCs were at a higher risk for DED.

CONCLUSIONS

This study indicates an increased risk of DED with HCs use in women of child-bearing age.

Evaluation of dry eye and Meibomian gland dysfunction in female androgenetic alopecia patients

PURPOSE

To evaluate dry eye tests and Meibomian gland functions in female androgenetic alopecia patients.

MATERIALS AND METHODS

Twenty left eyes of 20 female androgenetic alopecia patients (Group 1) and 20 left eyes of 20 healthy female volunteers (Group 2) were enrolled in the study. The presence of dry eye was evaluated with Schirmer 1 test, invasive tear film break-up time (T-BUT), Oxford scale scoring and Ocular Surface Disease Index (OSDI) score assessments. Evaluation of upper and lower eyelid Meibomian glands was performed using infrared filter of a slit-lamp biomicroscope, and the drop out ratio was scored for each eyelid.

RESULTS

The mean ages of Group 1 and Group 2 were 48.3 ± 6.6 (range, 38-58) and 49.8 ± 5.4 (range, 38-59) years, respectively (P = 0.437). Mean T-BUT was statistically significantly lower in Group 1 (P = 0.013); mean OSDI score was significantly higher in Group 1 (P = 0.049). Mean Schirmer 1 score was lower and mean Oxford score was higher in Group 1, but the differences were not statistically significant (P = 0.291, P = 0.088, respectively). In addition, upper, lower and total meiboscores were significantly higher in Group 1 (P = 0.007, P = 0.003, P = 0.002, respectively).

CONCLUSION

Alterations in sex hormones play a role in the pathogenesis of both female androgenetic alopecia and Meibomian gland dysfunction. Significant differences were detected in the results of dry eye tests and Meibomian gland dropout ratios between subjects with female androgenetic alopecia and healthy control subjects. For this reason, female androgenetic alopecia patients should be examined for dry eye and Meibomian gland dysfunction and should be treated to prevent serious consequences.

The Emerging Role of Topical Ocular Drugs to Target the Posterior Eye

The prevalence of chronic fundus diseases is increasing with the aging of the general population. The treatment of these intraocular diseases relies on invasive drug delivery because of the globular structure and multiple barriers of the eye. Frequent intraocular injections bring heavy burdens to the medical care system and patients. The use of topical drugs to treat retinal diseases has always been an attractive solution. The fast development of new materials and technologies brings the possibility to develop innovative topical formulations. This article reviews anatomical and physiological barriers of the eye which affect the bioavailability of topical drugs. In addition, we summarize innovative topical formulations which enhance the permeability of drugs through the ocular surface and/or extend the drug retention time in the eye. This article also reviews the differences of eyes between different laboratory animals to address the translational challenges of preclinical models. The fast development of in vitro eye models may provide more tools to increase the clinical translationality of topical formulations for intraocular diseases. Clinical successes of topical formulations rely on continuous and collaborative efforts between different disciplines.

Lacrimal gland excision in male and female mice causes ocular pain and anxiety-like behaviors

Lacrimal gland excision (LGE) induced dry eye produces more severe corneal damage in female mice, yet signs of LGE-induced ocular pain and anxiety in male and female mice have not been characterized. Excision of either the extraorbital gland (single LGE), or both the extraorbital and intraorbital glands (double LGE) was performed in male and female C57BL/6J mice to induce moderate and severe dry eye. Ongoing pain was assessed by quantifying palpebral opening and evoked nociceptive responses after corneal application of capsaicin and menthol. The open-field and plus maze were used to assess anxiety. Single LGE caused a reduction in palpebral opening and an increase in capsaicin and menthol-evoked responses only in female mice. Furthermore, single LGE produced signs of increased anxiety in female but not male mice. Overall, female mice appear more susceptible to signs of ocular pain, irritation, and anxiety in response to aqueous tear deficiency.

An eye on the dog as the scientist's best friend for translational research in ophthalmology: Focus on the ocular surface

Preclinical animal studies provide valuable opportunities to better understand human diseases and contribute to major advances in medicine. This review provides a comprehensive overview of ocular parameters in humans and selected animals, with a focus on the ocular surface, detailing species differences in ocular surface anatomy, physiology, tear film dynamics and tear film composition. We describe major pitfalls that tremendously limit the translational potential of traditional laboratory animals (i.e., rabbits, mice, and rats) in ophthalmic research, and highlight the benefits of integrating companion dogs with clinical analogues to human diseases into preclinical pharmacology studies. This One Health approach can help accelerate and improve the framework in which ophthalmic research is translated to the human clinic. Studies can be conducted in canine subjects with naturally occurring or noninvasively induced ocular surface disorders (e.g., dry eye disease, conjunctivitis), reviewed herein, and tear fluid can be easily retrieved from canine eyes for various bioanalytical purposes. In this review, we discuss common tear collection methods, including capillary tubes and Schirmer tear strips, and provide guidelines for tear sampling and extraction to improve the reliability of analyte quantification (drugs, proteins, others).

Health Risks Associated with Long-Term Finasteride and Dutasteride Use: It's Time to Sound the Alarm

5α-dihydrotestosterone (5α-DHT) is the most potent natural androgen. 5α-DHT elicits a multitude of physiological actions, in a host of tissues, including prostate, seminal vesicles, hair follicles, skin, kidney, and lacrimal and meibomian glands. However, the physiological role of 5α-DHT in human physiology, remains questionable and, at best, poorly appreciated. Recent emerging literature supports a role for 5α-DHT in the physiological function of liver, pancreatic β-cell function and survival, ocular function and prevention of dry eye disease and kidney physiological function. Thus, inhibition of 5α-reductases with finasteride or dutasteride to reduce 5α-DHT biosynthesis in the course of treatment of benign prostatic hyperplasia (BPH) or male pattern hair loss, known as androgenetic alopecia (AGA) my induces a novel form of tissue specific androgen deficiency and contributes to a host of pathophysiological conditions, that are yet to be fully recognized. Here, we advance the concept that blockade of 5α-reductases by finasteride or dutasteride in a mechanism-based, irreversible, inhabitation of 5α-DHT biosynthesis results in a novel state of androgen deficiency, independent of circulating testosterone levels. Finasteride and dutasteride are frequently prescribed for long-term treatment of lower urinary tract symptoms in men with BPH and in men with AGA. This treatment may result in development of non-alcoholic fatty liver diseases (NAFLD), insulin resistance (IR), type 2 diabetes (T2DM), dry eye disease, potential kidney dysfunction, among other metabolic dysfunctions. We suggest that long-term use of finasteride and dutasteride may be associated with health risks including NAFLD, IR, T2DM, dry eye disease and potential kidney disease.

Management of meibomian gland dysfunction: a review

Meibomian gland dysfunction is the leading cause of evaporative dry eye disease and is one of the most common conditions encountered by eye care providers. The disorder is characterized by obstruction of the meibomian gland terminal ducts and/or changes in their glandular secretion, resulting in changes in tear film stability, inflammation, and symptoms of irritation. There is no gold standard treatment for meibomian gland dysfunction, but rather a diversity of options. Conservative measures include warm compresses and lid hygiene, but there is growing interest and need for medical treatments and procedures. Potential medical treatments include antibiotics, nonsteroidal and steroidal anti-inflammatory agents, essential fatty acid supplementation, hormone therapy, and control of Demodex infestation. Procedures include intraductal meibomian gland probing, the use of electronic heating devices, intense pulsed light therapy, and intranasal neurostimulation. We provide an update on meibomian gland dysfunction treatments based on recent studies.

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.

A comparison of the effects of estrogen and Cimicifuga racemosa on the lacrimal gland and submandibular gland in ovariectomized rats

This study aims to observe the effects of estradiol and Cimicifuga racemosa on the lacrimal gland and submandibular gland of ovariectomized rats. We randomly divided 20 adult female SD rats into four groups-a sham-operated group (SHAM), ovariectomized (OVX) group, ovariectomized group treated with estradiol (OVX+ E), and ovariectomized group treated with the isopropanolic extract of Cimicifuga racemosa (OVX+ iCR). The SHAM group and OVX group used distilled water to instead the drugs. Two weeks after ovariectomy, the estradiol and iCR were administered for 4 weeks. Next, we used H&E staining and electron microscopy to observe any histological changes in the lacrimal and submandibular glands and immunohistochemical staining to observe the expressions of cleaved caspase-3 (Casp-3) and Cu-Zn SOD (superoxide dismutase). The H&E staining find that both drugs can prevent the cells of area from shrinkage in the two kinds of gland. But under the electron microscopy, estradiol and iCR have different efficacy. Estradiol is more effective at protecting mitochondria in lacrimal gland acinar cells than iCR, and iCR is more effective at suppressing endoplasmic reticulum expansion than estradiol. Both estradiol and iCR have a similar protective function on mitochondria in the submandibular gland. The protective function of the two glands may inhibit apoptosis by suppressing the expression of Casp-3. In addition, iCR increases the expression of Cu-Zn SOD in duct system of submandibular gland. The results suggest that both estradiol and iCR confer a protective effect on the lacrimal and submandibular glands of ovariectomized rats via different mechanisms.

Sex-steroid imbalance in females and dry eye

Dry eye (DE) is a multifactorial disorder of the ocular surface unit that results in eye discomfort, visual disturbance and ocular surface damage. It is one of the most common complaints in daily ophthalmic practice. The risk of DE increases with age in both sexes, while its incidence is higher among females. In addition, the condition of menopause in aging women may also contribute to DE onset or worsening as a consequence of an overall hormonal imbalance. Sex hormones play a key role in ocular surface physiology and they impact differently on ocular surface tissues. Reduced estrogen levels were historically thought to be responsible in age-related DE onset but more recent investigations have reconsidered the role of androgens that are present and exert a protective function on the ocular surface. Hormone levels themselves, withdrawal changes in hormone levels, and the changes in hormone-receptor responsiveness are all important factors but it remains to be fully elucidated how estrogen or androgen insufficiency act alone or together in a combined imbalance or interplay to raise the risk of disease. The purpose of this review is to briefly outline current scientific evidence on the influence of androgens and estrogens, on the Lachrymal and Meibomian glands and on ocular surface epithelia including conjunctival goblet cells during reproductive and menopausal periods. The role of sex steroids is also discussed in relation to the pathogenesis of different forms of DE and Sjogren's syndrome (SS). The impact of systemic hormone therapy (HT) in DE post-menopausal women still appears as a controversial issue, despite the many clinical studies. Finally, the outcomes of topical applications of steroid-based products are summarized, underlying the need for potential (tear) biomarker(s) in the rationale of DE-targeted therapy.

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.

Research on the stability of a rabbit dry eye model induced by topical application of the preservative benzalkonium chloride

Background

Dry eye is a common disease worldwide, and animal models are critical for the study of it. At present, there is no research about the stability of the extant animal models, which may have negative implications for previous dry eye studies. In this study, we observed the stability of a rabbit dry eye model induced by the topical benzalkonium chloride (BAC) and determined the valid time of this model.

Methods and Findings

Eighty white rabbits were randomly divided into four groups. One eye from each rabbit was randomly chosen to receive topical 0.1% BAC twice daily for 2 weeks (Group BAC-W2), 3 weeks (Group BAC-W3), 4 weeks (Group BAC-W4), or 5 weeks (Group BAC-W5). Fluorescein staining, Schirmer's tests, and conjunctival impression cytology were performed before BAC treatment (normal) and on days 0, 7, 14 and 21 after BAC removal. The eyeballs were collected at these time points for immunofluorescence staining, hematoxylin and eosin (HE) staining, and electron microscopy. After removing BAC, the signs of dry eye in Group BAC-W2 lasted one week. Compared with normal, there were still significant differences in the results of Schirmer's tests and fluorescein staining in Groups BAC-W3 and BAC-W4 on day 7 (P<0.05) and in Group BAC-W5 on day 14 (P<0.05). Decreases in goblet cell density remained stable in the three experimental groups at all time points (P<0.001). Decreased levels of mucin-5 subtype AC (MUC5AC), along with histopathological and ultrastructural disorders of the cornea and conjunctiva could be observed in Group BAC-W4 and particularly in Group BAC-W5 until day 21.

Conclusions

A stable rabbit dry eye model was induced by topical 0.1% BAC for 5 weeks, and after BAC removal, the signs of dry eye were sustained for 2 weeks (for the mixed type of dry eye) or for at least 3 weeks (for mucin-deficient dry eye).

Sex hormone regulation of tear lipocalin in the rabbit lacrimal gland

Tear lipocalin (TL) (approximately 18 kDa), a member of the lipocalin superfamily, has been identified as one of the major proteins present in rabbit lacrimal fluid. The concentration of TL has been found to be decreased in the tears of patients with dry eye disease. Lacrimal gland insufficiency, one of the major causes of dry eye disease, is known to affect mainly postmenopausal women, where there is a significant decrease in the production of androgen and estrogen. These observations suggest that sex hormones might influence dry eye indirectly by regulating the expression of TL. The purpose of this study was to determine: (1) the effect of sexual maturation on the expression of TL; and (2) if the expression of TL is regulated by the estrogen, 17beta-estradiol, and/or the androgen, dihydrotestosterone, in sexually mature female rabbits. Lacrimal fluid (LF) and lacrimal gland soluble fraction (Si) was collected from juvenile (2 kg) and sexually mature (4 kg) male and female New Zealand white (NZW) rabbits. In addition, LF and Si were collected from 4 kg rabbits, 7 days after being either sham operated (control), ovariectomized (OVX), ovariectomized treated with estrogen (OVX+E) or ovariectomized treated with dihydrotestosterone (OVX+DHT). Samples were analyzed for protein levels of TL by SDS-PAGE and Western blotting using a polyclonal rat anti-rabbit TL antibody. Densitometry analysis showed that TL protein levels in both LF and Si increased with age in male and female rabbits. In addition, TL protein levels were significantly higher in the sexually mature 4 kg male compared with the 4 kg female, while no significant difference in TL protein levels were seen among the juvenile male and female rabbits. Furthermore, ovariectomy decreased the protein levels of TL in LF and Si fraction by 50% and 20% respectively, compared with control values. Estrogen treatment increased TL protein levels by 30% and 50% in the LF and Si fraction respectively, compared with the sham operated group. DHT treatment also increased TL protein levels by approximately 150% in both LF and Si fraction compared with control values. These results support the hypothesis that sex hormones influence TL protein levels in rabbit lacrimal glands. The possibility of a role of TL in dry eye needs to be further investigated.

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.

Menopause and dry eye. A possible relationship

The hormonal status and in particular sex steroids play a role in the ocular surface homeostasis and function, during the whole life and in both sexes, accomplished by estrogenic and androgenic receptors located on corneal and conjunctival epithelia and Meibomian gland. The ocular surface is an integrated unit and any dysfunction results in a scarce or unstable preocular tear film which produces dry eye, a chronic inflammatory condition with increasing incidence as people get older but always more frequent among females. In post-menopausal women endocrine changes join the aging effects in the pathogenesis of dry eye, but still it remains controversial whether estrogen or androgen deficiency or their imbalance impair ocular surface function. Another questionable issue concerns the efficacy of hormonal replacement therapy in the amelioration of dry eye symptoms and recovery of tear function, since the scientific literature stands in between a therapeutic or a promoting effect of eye dryness. Therapy of dry eye is usually based upon topical administration of tear substitutes; estrogen or androgen-based eye drops represents a promising innovative treatment based upon important scientific rationale.

Analysis of human tear fluid by Fourier transform infrared spectroscopy

The purpose of this research is to find some useful spectroscopic factors in human tear fluid contents to monitor diurnal changes of the physicochemical ocular conditions noninvasively. All tear fluid samples were collected with glass microcapillary tubes from both eyes of three donors and analyzed by Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). We measured the peak intensities at 2852, 1735, 1546, and 1242 cm(-1), and the peak intensity ratios among those peaks in the second derivative spectra. We found significant diurnal and individual variations in those peak intensities for tear fluid obtained from right and left eyes. Among these variations, we observed significant changes in tear samples between right and left eyes. In this case the peak intensity ratio between 1242 (phosphate ester) and 2852 cm(-1) (fatty acid methylene) of right eye tear fluid was increased in the afternoon (1600 to 1900 h), while that of left eye tear fluid did not change significantly. In the ratio between 1242 (phosphate ester) and 1546 cm(-1) (amide II), the difference was not observed between both eyes. We conclude that the difference in diurnal variations of biochemical constituents between right and left eye tear fluids could be monitored noninvasively and nondestructively by FTIR technique and this method could be useful in the future for tear diagnoses.

Influence des hormones sur le film lacrymal

Tear film quality depends on fine regulatory mechanisms affected by neuronal and hormonal influences. Indeed, receptors for androgens, estrogens, progesterone and prolactin have been identified in several ocular tissues in the rat, rabbit and in humans. The eye is thus a target organ for sex hormones, particularly the androgens. These hormones regulate the immune system, the morphology and secretory functions of lacrimal glands and the functioning of Meibomian glands. The influence of hormone replacement therapy in menopausal women remains unclear, as some authors support the idea that they improve the quality and the volume of tear film, whereas others have shown that they increase the risk of dry eye. Finally, knowledge of the interactions between the hormones that influence the lacrimal glands is essential for the understanding of the regulation of lacrimal gland function. However, the data presently available strongly suggest that optimal bioavailable androgen levels are essential for normal lacrimal gland function and that prolactin and estrogens also play important roles in providing a hormonal milieu that contributes to normal lacrimal gland function.

Estrogen prevention of lacrimal gland cell death and lymphocytic infiltration

Previous studies have shown that ovariectomy causes necrosis of lacrimal acinar cells, apoptosis of plasma cells and gland lymphocytic infiltration. Both, lacrimal gland cell death and lymphocytic infiltration were prevented by androgen treatment. Since estrogens are removed by ovariectomy, and the synthetic estrogen diethylstilbestrol has been shown to affect some biochemical correlates of lacrimal secretion, the purpose of this study was to determine the effect of 17-beta-estradiol treatment on ovariectomy-induced cell death and lymphocytic infiltration. Sexually mature female New Zealand white rabbits (4-4.5 kg) were ovariectomized and divided into two groups. One group was treated with 0.5 mg kg(-1) per day 17-beta-estradiol, and the other group with vehicle alone. A third group of sham operated rabbits was used as controls and they also were treated with vehicle alone. Six days after surgery, the animals were euthanized, the lacrimal glands removed and processed for analysis of apoptosis as assessed by DNA fragmentation, and for morphological examination. DNA fragmentation was determined using the TUNEL assay and agarose gel electrophoresis. Sections were also stained for rabbit thymic lymphocyte antigen (RTLA), and rabbit CD18. Labelled nuclei and stained areas were quantified by automated densitometry. Ovariectomized rabbits showed a significant increase in the values for degraded DNA as a percent of total nuclear area (2.90+/-0.40%) compared to sham operated rabbits (0.73+/-0.22%). 17-beta-estradiol treatment in ovariectomized rabbits prevented the increase in DNA degradation. Examination of TUNEL assay at higher magnification (40x) confirmed previous studies showing that ovariectomy caused apoptosis of interstitial cells. Significant numbers of bulging cells of very pale appearance under light microscopy, also confirm previously identified necrotic cells in acinar regions. Treatment with 17-beta-estradiol prevented this necrosis. Increased numbers of RTLA(+) and CD18(+) interstitial cells were also evident after ovariectomy. 17-beta-estradiol treatment prevented the increase in the number of lymphoid cells. We confirmed previous observations that suggest that glandular atrophy observed after ovariectomy is likely to proceed by necrosis of acinar cells rather than apoptosis, and that ovariectomy triggers an inflammatory response in the gland. These results suggest that in addition to androgens, estrogens also seem to play a role to maintain lacrimal gland structure and function. A decrease in available estrogen levels could trigger both lacrimal gland apoptosis and necrosis, as well as lymphocytic infiltration. Although, the effect of estrogens in these experiments seems to be direct and not through androgens, the possibility of the role of an autocrine and/or paracrine factors, promoted by estrogen on lacrimal gland cells still needs to be investigated.

Morphological and morphometric analysis on the rabbit conjunctival goblet cells in different hormonal conditions

An altered conjunctival mucous secretion was reported in pregnancy or oral contraceptive use. Four groups of rabbits (males, dioestrous females, oestrous females, pregnant) were studied to determine whether sex and/or different physiological conditions could influence conjunctival goblet cells structure and ultrastructure. Light microscopy, transmission electron microscopy, and morphometry were performed. In males and in oestrous females the intracytoplasmic secretory granules were filled with granular material, whilst in pregnant and dioestrous females the granules were formed by a more homogenous and dense secretory material. The number of goblet cells was not statistically different in the groups studied, whilst pregnant animals showed the largest mean diameter. As to the secretory granules, their mean area was larger in dioestrous females, whilst their optical density was highest in pregnant animals. These observations indicate that the morphology of conjunctival goblet cell may vary according to sex and to different physiological conditions: this may account for the peculiar mucous secretion demonstrated during pregnancy.

Androgen support of lacrimal gland function

The effects of dihydrotestosterone (DHT) (1 mg/kg) on biochemical parameters related to lacrimal secretion, basal tear flow rate, and pilocarpine-stimulated lacrimal gland fluid secretion, in mature ovariectomized rabbits were studied. The effects of the synthetic estrogen diethylstilbestrol (DES) (100 micrograms/kg), on lacrimal gland biochemical parameters in normal mature female rabbits was also studied. Ovariectomy decreased the total serum levels of testosterone (T) by 88.5% and androstenedione by 35.9%, without changing the levels of dehydroepiandrosterone (DHEA) of its sulfate. Ovariectomy caused a significant regression of the lacrimal glands, decreasing total DNA by 35%, and total protein by 22%. DHT treatment of ovariectomized animals prevented lacrimal gland regression, increasing total gland DNA (31%) and total protein (18%). DHT treatment also increases Na+, K(+)-ATPase activity (29%) and beta-adrenergic receptor binding sites (23%) compared to the ovariectomized group. DHT increased pilocarpine stimulated lacrimal gland fluid secretion (13.26 +/- 1.47 microL/min) compared to the ovariectomized group (7.72 +/- 0.41 microL/min), but DHT treatment paradoxically decreased basal tear flow rate (1.02 +/- 0.04 microL/min) as compared to the ovariectomized rabbits (1.96 +/- 0.12 microL/min). DES decreased the total serum T from 59.33 +/- 10.54 pg/mL to 21.5 +/- 6.06 pg/mL. DES decreased total Na+,K(+)-ATPase by 12% and increased beta-adrenergic receptor binding sites by 83.3%. These results suggest that androgens play a major role in supporting lacrimal gland secretory function. Additionally, they suggest that estrogens may influence certain aspects of lacrimal functions, although it is not clear to what extent those actions are elicited directly or indirectly.

Androgen stimulation of lacrimal gland function in mouse models of Sjögren's syndrome

Sjögren's syndrome, an autoimmune disease that occurs primarily in women, causes extensive inflammation and significant dysfunction in the lacrimal gland, and is one of the leading causes of dry eye syndromes throughout the world. Recently, our research has shown that androgen treatment causes a significant suppression of the immunopathological lesions in lacrimal tissues of female mouse models (MRL/Mp-lpr/lpr [MRL/lpr] and NZB/NZW F1 [F1]) of Sjögren's syndrome. To extend these findings, the objective of the present study was to determine whether this androgen-induced anti-inflammatory action may be paralleled by an increase in the functional activity of lacrimal glands in these autoimmune mice. Towards this end, we measured the tear levels of immunoglobulin A (IgA), which originates from lacrimal tissue and whose concentration is known to be diminished in mucosal sites in Sjögren's syndrome. For comparative purposes, we also evaluated whether the administration of other steroid hormones or immunosuppressive agents might duplicate possible androgen effects on the secretory function of lacrimal tissue. Female MRL/lpr and F1, as well as non-autoimmune BALB/c, mice were treated with vehicle, steroids or immunosuppressive compounds for 17 to 54 days after the onset of disease. Lacrimal glands, tears and sera were collected immediately before (pretreatment), or after, therapy and processed for the analysis of either tear IgA (enzyme-linked immunosorbent assay; ELISA) and protein content or the magnitude of lymphocyte infiltration (computer-assisted image analysis). Our findings demonstrated that testosterone treatment stimulated a significant increase in the concentration and total amount of tear IgA, as well as tear protein, compared to levels in pretreatment or placebo controls. This hormone action was reproduced by exposure to a diverse array of "anabolic" and "androgenic" androgen analogues, but not by treatment with estradiol, danazol, cyclosporine A, dexamethasone or cyclophosphamide. In contrast, only dexamethasone increased serum IgA concentrations. Of particular interest is the fact that the androgen control of IgA output by the lacrimal gland appeared to be independent of this steroid's suppression of lymphocyte infiltration in lacrimal tissue. Overall, these results show that androgen therapy enhances the functional activity of the lacrimal gland in mouse models of Sjögren's syndrome.

Influence of androgens and pituitary hormones on the structural profile and secretory activity of the lacrimal gland

The present study was designed to examine the influence of androgens on the size, morphological appearance, and fluid and protein secretory capacity of the lacrimal gland in a variety of species. For comparison, we also sought to determine whether other hormones might stimulate the growth and secretory ability of this tissue. Lacrimal glands and tears were obtained from intact, surgically-operated and/or hormone-treated rats, mice, guinea pigs and rabbits and the processed for histological and/or image analysis techniques. Our results demonstrated that: 1) androgens modulate the ultrastructural features of rat lacrimal tissue; 2) androgens may influence the weight, morphological aspects, and secretion of the lacrimal gland, however, these effects are not uniform in mice, rats, guinea pigs and rabbits, but instead are dependent upon the species and/or the animal's endocrine status; and 3) treatment with testosterone, prolactin, growth hormone, alpha-melanocyte stimulating hormone, insulin, or thyroxine plus dexamethasone had no impact on the absolute or relative size of the lacrimal gland, or the tear volume, of hypophysectomized male rats. Overall, these findings indicate that androgens may regulate the structure and secretion of the lacrimal gland. However, the nature and extent of this hormone action is species-dependent and may be modified by alterations in the endocrine environment.

Identification and endocrine control of sex steroid binding sites in the lacrimal gland

Previous research has indicated that the lacrimal gland may be a target organ for sex steroids and that androgen effects on this tissue may be inhibited by pituitary deficiency or diabetes. To extend these findings, the objectives of the current investigation were 3-fold: [a] to determine whether specific and high-affinity binding sites for androgens and estrogens exist in rat lacrimal tissue; [b] to assess whether the number and affinity of androgen binding sites in the lacrimal gland may be influenced by hypophysectomy or acute diabetes; and [c] to examine whether androgen receptor mRNA may be detected in lacrimal tissues of a variety of species. Following the collection of lacrimal gland samples, tissues were processed for the conduct of equilibrium binding methods or molecular biological techniques. Our results demonstrated that a single class of saturable, high-affinity and stereochemically selective binding sites for androgens exist in lacrimal tissues of male and female rats. These sites possessed a dissociation constant of approximately 1 nM and were also present in isolated acinar epithelial cells. In contrast, we were unable to find any evidence for the presence of specific or high-affinity receptors for estrogens in the rat lacrimal gland. With regard to changes in the endocrine environment, hypophysectomy led to an increase in the number and affinity of androgen binding sites in rat lacrimal tissue cytosol, whereas diabetes reduced the total quantity of these sites. Of interest, androgen receptor mRNA was detected in lacrimal glands of mice, rats, hamsters, guinea pigs, rabbits and humans. Overall, our findings show that the lacrimal gland is a target organ for androgens and that androgen action in this tissue may be mediated through an interaction with specific and high-affinity binding sites.

Androgen control of secretory component mRNA levels in the rat lacrimal gland

The purpose of this investigation was to determine whether the known gender-related differences in, and the endocrine control of, the production of secretory component (SC) by the rat lacrimal gland are associated with alterations in SC mRNA content. Levels of SC mRNA were measured in lacrimal tissues of intact, sham-operated, castrated, hypophysectomized, and testosterone-treated male and female adult rats by Northern blot procedures, which utilized a specific, [alpha-32P]-labelled rat SC cDNA probe. For control purposes, SC mRNA amounts were standardized to the beta-actin content in experimental blots. The location of SC mRNA in lacrimal glands was evaluated by in situ hybridization techniques, which involved exposure of tissue sections to sense or anti-sense [35S]-labelled SC RNA probes. Our results demonstrate that: (1) lacrimal glands of male rats contain a significantly greater amount of SC mRNA than those of female rats, and that this difference co-exists with distinct, gender-associated variations in the distribution of SC mRNA in lacrimal tissue; (2) orchiectomy or hypophysectomy, but not ovariectomy or sham surgery, leads to a marked decline in the lacrimal SC mRNA content; and (3) testosterone, but not placebo, administration to castrated male and female rats induces a significant increase in the SC mRNA levels in lacrimal tissue. Overall, these findings show that gender, androgens and the hypothalamic-pituitary axis exert a considerable influence on the SC mRNA content in the rat lacrimal gland.

Sex-dependent parameters related to electrolyte, water and glycoprotein secretion in rabbit lacrimal glands

The lacrimal glands of males and females of various species differ with respect to several morphological, biochemical and functional characteristics. The purpose of this study was to determine the effect of sexual maturation on Na+,K(+)-ATPase, muscarinic cholinergic receptors and beta-adrenergic receptors, which are closely related to the secretion of electrolytes and fluid by the gland, and on other membrane-associated enzymes, specifically galactosyltransferase and alkaline and acid phosphatase. Soluble and total membrane fractions were obtained from lacrimal glands of prepubertal (1.0 kg), pubertal (2 kg), and mature (4 kg) of New Zealand white rabbits of both sexes. Prepubertal and pubertal rabbits exhibited no sex differences in the total amount of lacrimal gland protein or in any of the enzymes or receptors, with the exception of galactosyltransferase and alkaline phosphatase. Galactosyltransferase had higher total and specific activities in prepubertal and pubertal males, and alkaline phosphatase had higher specific activity in prepubertal males. As animals matured, total protein and activities of the enzymes increased, and several quantitative differences between males and females became apparent. Samples from mature females contained significantly less DNA and membrane and total protein. Specific activities of Na+,K(+)-ATPase, cholinergic receptors, galactosyltransferase, and acid and alkaline phosphatase were 40% to 80% greater (p < 0.05) in mature females. Total and specific activity for beta-adrenergic receptors, on the other hand, were higher in the male rabbits. These findings suggest that sex hormones play a role in regulating the levels of expression of a number of enzymes and receptors, including several which are clearly involved in lacrimal secretory functions.

Hormonal influence on the secretory immune system of the eye: endocrine impact on the lacrimal gland accumulation and secretion of IgA and IgG

The objective of the current investigation was to explore the processes underlying the androgen control of tear IgA and to determine whether hormone exposure also modifies tear IgG content. In addition, studies evaluated the impact of diabetes on the androgen regulation of secretory immunity in the eye. Tears and lacrimal glands were collected from age-matched, adult male rats, which had undergone hypophysectomy, selective ablation of the anterior pituitary, streptozotocin-induced diabetes, sham-surgery and/or orchiectomy and had been exposed to vehicle or physiological amounts of testosterone for varying periods of time. Our findings demonstrated that testosterone administration selectively increased the accumulation of IgA, but not IgG, in tears and lacrimal glands of orchiectomized rats. This hormone effect was associated with a 2-fold enhancement of the IgA transfer from lacrimal tissue to tears; IgA movement was against a gradient. In contrast, androgen exposure had no significant influence on the lacrimal gland/tear transfer of IgG, which was down a 90-fold gradient. Testosterone action on the lacrimal gland appeared to involve an increase in IgA production, but not a consistent alteration in the total number of IgA-containing cells. Similarly, androgen exposure had no impact on the population of IgG-containing lymphocytes in lacrimal tissue. Of interest, ablation of the anterior or entire pituitary in orchiectomized rats, which procedure inhibits testosterone-induced stimulation of tear IgA levels, significantly reduced the total number of IgA-containing cells in the lacrimal gland. Induction of diabetes by streptozotocin injection to orchiectomized rats resulted in diminished tear IgA content and decreased numbers of lacrimal IgA-positive lymphocytes, but did not prevent the testosterone-associated rise in IgA antibody content. In summary, our findings demonstrate that androgens increase the lacrimal gland production and secretion of IgA, but not IgG.

Selectivity, specificity and kinetics of the androgen regulation of the ocular secretory immune system

The purpose of the present investigation was to determine the selectivity, specificity and kinetics of the androgen regulation of the ocular secretory immune system. To examine the mucosal selectivity of hormone action, tears, saliva, respiratory and intestinal secretions, urine and serum were collected from orchiectomized rats following four days of treatment with saline or testosterone. Androgen administration significantly increased the tear levels of IgA and free SC. In contrast, this combined hormone response was not duplicated in other mucosal secretions or serum. Consequently, it appears that the androgen control of the ocular secretory immune system is unique to the eye. To evaluate androgenic specificity, orchiectomized rats were treated for four days with saline, testosterone, 5 alpha-androstan-17 beta-o1 ('5 alpha'), 4-estren-7 alpha-methyl-17 beta-o1-3-one ('4-E') or the synthetic analogue, danazol. Results demonstrated that testosterone and '4-E', a potent androgen, both stimulated the accumulation of tear IgA and free SC, compared to amounts in tears of saline-treated controls. The weak androgen '5 alpha' induced a slight rise in tear free SC, but not IgA, levels, whereas danazol had no effect on the ocular secretory immune system. These findings indicate that androgen structure is of critical importance in modulation of mucosal immunity in the eye. Lastly, to assess the kinetics of hormone action on tear IgA and free SC, orchiectomized rats were acutely (0, 1.5, 4, 7, 12, or 24 hours) or chronically (0, 4, 7, 11, 14, or 17 days) exposed to testosterone. Acute androgen exposure for less than 12 hours did not elicit any change in the tear content of IgA or free SC. In comparison, chronic androgen treatment induced a progressive and dramatic rise in the levels of both tear proteins. By 17 days of hormone exposure, the IgA and free SC concentrations in tears had increased by 14- and 18-fold amounts, respectively, relative to amounts in placebo-treated controls. Of interest, the temporal pattern of accumulation of tear IgA and free SC were different. Overall, these results show prolonged, but not abbreviated, exposure to androgens has a profound impact on the IgA and free SC profile in tears.

Influence of the hypothalamic-pituitary axis on the androgen regulation of the ocular secretory immune system

The purpose of the present investigation was to examine the influence of the hypothalamic-pituitary axis on the androgen regulation of the ocular secretory immune system. Studies included the following experiments: (1) Testosterone administration significantly increased the immunoglobulin A (IgA) and free secretory component (SC) levels in tears of adult, orchiectomized and sham-hypophysectomized rats, as compared with those in tears of saline-treated controls. (2) Hypophysectomy completely inhibited this androgen effect. (3) Transfer of the pituitary to under the kidney capsule in orchiectomized and hypophysectomized rats did not restore the physiological conditions required for testosterone's stimulation of tear IgA and SC. (4) Selective ablation of the anterior pituitary gland also interfered with the testosterone-induced elevation of tear IgA and SC content. (5) Treatment of orchiectomized and/or hypophysectomized rats with rat prolactin, growth hormone, alpha-melanocyte-stimulating hormone or vehicle for 4 days had no effect on tear SC and/or IgA levels. Overall, these findings demonstrate that an intact hypothalamic-pituitary axis either supports or mediates the androgen control of the secretory immune system in the eye.

Recent developments in dry eye management

A concise review of current knowledge in the stimulation and regulation of tear production and its relationship to the ocular surface is presented. A discussion of treatment modalities, their benefits and drawbacks, follows. An approach to developing a rational treatment plan in the management of dry eyes is suggested with specific strategies. The application of these principles and the use of specific treatment modalities to manage the discreet manifestations of dry eye syndrome can lead to successful management in the majority of cases, with the preservation of useful vision and the relief of symptoms.

The immune response of the lacrimal gland to antigenic exposure

This study probed the influence of antigenic exposure on the immunological response of the lacrimal gland. We utilized the germfree rat as a model system to monitor tissue and tear immunoglobulin changes following transfer of these animals into an antigen-laden, conventional environment. The number of IgA- and IgM-containing cells in the lacrimal glands of germfree rats was 5 to 8 fold less than that of conventional controls. This reduced immunological expression in germfree animals also extended to tear IgA levels, which were significantly decreased. No effect of germfree conditions was found on the tear content of secretory component (SC). Transfer of rats from a germfree to a conventional environment resulted in a significant increase in the number of IgA- and IgM-containing cells in the lacrimal gland. By four weeks after 'conventionalization', the number of Ig-containing cells in lacrimal tissue was similar in both ex-germfree and conventional rats. In addition, 'conventionalization' led to a significant increase in the tear content of IgA: within four weeks following exposure to a conventional environment, tear IgA levels in ex-germfree rats were equivalent to those of age-matched, conventional controls. Overall, our results demonstrate that the secretory immune system of the lacrimal gland reacts to antigenic challenge with an increased immunological response.