Sex hormone regulation of tear lipocalin in the rabbit lacrimal gland

Critical role of mass spectrometry proteomics in tear biomarker discovery for multifactorial ocular diseases (Review)

The tear film is a layer of body fluid that maintains the homeostasis of the ocular surface. The superior accessibility of tears and the presence of a high concentration of functional proteins make tears a potential medium for the discovery of non-invasive biomarkers in ocular diseases. Recent advances in mass spectrometry (MS) have enabled determination of an in-depth proteome profile, improved sensitivity, faster acquisition speed, proven variety of acquisition methods, and identification of disease biomarkers previously lacking in the field of ophthalmology. The use of MS allows efficient discovery of tear proteins, generation of reproducible results, and, more importantly, determines changes of protein quantity and post-translation modifications in microliter samples. The present review compared techniques for tear collection, sample preparation, and acquisition applied for the discovery of tear protein markers in normal subjects and multifactorial conditions, including dry eye syndrome, diabetic retinopathy, thyroid eye disease and primary open-angle glaucoma, which require an early diagnosis for treatment. It also summarized the contribution of MS to early discovery by means of disease-related protein markers in tear fluid and the potential for transformation of the tear MS-based proteome to antibody-based assay for future clinical application.

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).

Development and Long-Term Evaluation of Ocular Surface Conditions Using Ovariectomized Cynomolgus Monkey

OBJECTIVES

We aim to use the ovariectomized cynomolgus monkey to observe the effect of long-term changes of sex hormone levels on ocular surface.

METHODS

Six healthy adolescent cynomolgus monkeys were randomly assigned to control and experimental groups (n=3/group). Bilateral ovariectomy was performed in experimental group, and sham operation was performed on control animals with their ovaries reserved. The concentrations of serum estradiol and testosterone in cynomolgus monkeys' lower-limb venous were detected by radioimmunoassay before surgery, and at 6, 12, 18, and 24 months after the surgery. Phenol red cotton thread test, tear osmolarity, corneal fluorescein staining, and conjunctival impression cytology were performed to evaluate the ocular surface conditions before surgery, and at 6, 12, 18, and 24 months after the surgery. The histological examinations of the bulbar conjunctiva and labial glands tissues were performed at 12 and 24 months after the surgery.

RESULTS

There were no significant differences in the serum level of estradiol and testosterone between the experimental and control groups before surgery, at 6, and 12 months after surgery (P>0.05). Serum level of estradiol and testosterone were significantly less in experimental versus control group at 18 and 24 months after surgery (P<0.05). There was no significant differences in phenol red cotton between the experimental and control groups before surgery, at 6, 12, 18, and 24 months after surgery (P>0.05). Tear osmolarity had no significant differences between experimental and control group before surgery (P>0.05), and it was significantly higher in experimental versus control group at all four time-points after surgery (P<0.05). The number of conjunctival goblet cells had no significant differences between experimental and control group before surgery, at 6 months after surgery (P>0.05), and it was significantly lower in experimental versus control group at 12, 18, and 24 months after surgery (P<0.05). There were no significant differences in the corneal fluorescein staining score between the experimental and control groups before surgery, at 6, 12, and 18 months after surgery (P>0.05), and it was higher in experimental than control group at 24 months after surgery (P<0.05). In addition, inflammatory cell infiltration in bulbar conjunctiva and labial glands tissues was observed in experimental group and was unobserved in control group at 24 months after surgery.

CONCLUSIONS

Ovariectomy led to decreased sex hormone levels in cynomolgus monkey. In turn, tear osmolarity was increased, the number of conjunctival goblet cells were decreased, the corneal fluorescence staining was increased, and the pathological examination of the bulbar conjunctiva and labial glands tissues were abnormal, phenol red cotton thread test did not change significantly.

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.

Effect of estrogen receptor β agonists on proliferation and gene expression of ovarian cancer cells

Background

Estrogen receptor (ER) β has been suggested to affect ovarian carcinogenesis. We examined the effects of four ERβ agonists on proliferation and gene expression of two ovarian cancer cell lines.

Methods

OVCAR-3 and OAW-42 ovarian cancer cells were treated with the ERβ agonists ERB-041, WAY200070, Liquiritigenin and 3β-Adiol and cell growth was measured by means of the Cell Titer Blue Assay (Promega). ERβ expression was knocked down by transfection with specific siRNA. Additionally, transcriptome analyses were performed by means of Affymetrix GeneChip arrays. To confirm the results of DNA microarray analysis, Western blot experiments were performed.

Results

All ERβ agonists tested significantly decreased proliferation of OVCAR-3 and OAW-42 cells at a concentration of 10 nM. Maximum antiproliferative effects were induced by flavonoid Liquiritigenin, which inhibited growth of OVCAR-3 cells by 31.2% after 5 days of treatment, and ERB-041 suppressing proliferation of the same cell line by 29.1%. In OAW-42 cells, maximum effects were observed after treatment with the ERβ agonist WAY200070, inhibiting cell growth by 26.8%, whereas ERB-041 decreased proliferation by 24.4%. In turn, knockdown of ERβ with specific siRNA increased cell growth of OAW-42 cells about 1.9-fold. Transcriptome analyses revealed a set of genes regulated by ERβ agonists including ND6, LCN1 and PTCH2, providing possible molecular mechanisms underlying the observed antiproliferative effects.

Conclusion

In conclusion, the observed growth-inhibitory effects of all ERβ agonists on ovarian cancer cell lines in vitro encourage further studies to test their possible use in the clinical setting.

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.

Practical issues concerning tear protein assays in dry eye

Dry eye is a common clinical condition diagnosed by cumulative evidence of symptoms and signs. Many new treatments in dry eye are either expensive, invasive, have potential for side effects, or are not easily accessible. In severe dry eye, the ideal modality of treatment to begin with is often not clear as specific molecular disturbances are not evident from just examination of clinical manifestations. Assessing the effects of ongoing treatment is not straight forward since there is lack of agreement between clinical signs and symptoms. There is a need to have more objective methods of selecting treatment for dry eye and monitoring the effect of treatment. Recently, there are many new technologies applied to the discovery of tear biomarkers, for e.g., mass spectrometry based proteomics techniques and multiplex assays such as the bead-based sandwich indirect immunofluorescent assays. Tear proteins assays have even been made available as point-of-care devices. This review focuses on the evidence for the involvements of tear proteins in dry eye, possible changes in tear concentrations with therapy and the strength of evidence regarding dry eye pathology. Much remains to be done in terms of developing office-based assays and ascertaining their reliability, but current evidence suggests that tear proteins have a role in the clinical practice of dry eye.

Does estrogen deficiency cause lacrimal gland inflammation and aqueous-deficient dry eye in mice?

Researchers have proposed that estrogen deficiency will lead to a Sjögren's syndrome (SjS)-like lacrimal gland inflammation, aqueous tear deficiency and dry eye. The purpose of this study was to determine whether this proposal is correct. Lacrimal glands were obtained from adult, age-matched wild type (WT) and aromatase knockout (ArKO) mice, in which estrogen synthesis is completely eliminated. Tissues were also obtained from autoimmune MRL/Mp-lpr/lpr (MRL/lpr) mice as inflammation controls. Tear volumes in WT and ArKO mice were measured and glands were processed for molecular biological and histological evaluation. Our results demonstrate that estrogen absence does not lead to a SjS-like inflammation in lacrimal tissue or to an aqueous-deficient dry eye. There was no upregulation of genes associated with inflammatory pathways in lacrimal glands of male or female ArKO mice. Such inflammatory activity was prominent in autoimmune MRL/lpr tissues. We also found no evidence of inflammation in lacrimal gland tissue sections of estrogen-deficient mice, and tear volumes of ArKO males were actually increased as compared to those WT controls. Interestingly, our study did show that estrogen absence influences the expression of thousands of lacrimal gland genes, and that this impact is sex- and genotype-specific. Our findings demonstrate that estrogen absence is not a risk factor for the development of SjS-like lacrimal gland inflammation or for aqueous-deficient dry eye in mice.

Effects of estrogen replacement therapy on apoptosis and vascular endothelial growth factor expression in ocular surface epithelial cells: An experimental study

AIM

To investigate the effects of estrogen replacement therapy (ERT) on apoptosis and vascular endothelial growth factor (VEGF) expression in ocular surface in an experimental rat model.

METHODS

Forty female, Wistar rats were randomized in 4 groups in the study. Subcutaneous ERT (17β-estradiol, 10µg/kg/day) was administered to the first group without ovariectomy and to the second group with ovariectomy for three months. Third group had only ovariectomy and fourth group had sham operation. All rats were sacrificed in estrous cycles determined by vaginal smear test and their right eyes were enucleated at the end of the third month. Enucleated eyes were analyzed by immunohistochemical method for expressions of caspase-3, bcl-2, VEGF and TUNEL assay.

RESULTS

Caspase-3 expression of conjunctival epithelium was significantly higher in group 3 than group 1 (P=0.005), and group 2 (P=0.007). TUNEL score of conjunctival epithelium was significantly higher in group 3 than group1 (P=0.006). TUNEL score of corneal epithelium was significantly higher in group 3 than group 2 (P=0.012), and group 4 (P=0.002). There was no significant difference between groups in that bcl-2 and VEGF expressions.

CONCLUSION

We determined increased apoptosis in ocular surface epithelial cells in ovariectomized rats. ERT and endogen estrogen decreased the apoptosis, and did not result in difference in VEGF expression between the groups. Estrogen may be beneficial for the treatment of apoptosis-mediated ocular surface disorders such as dry eye. Further studies are needed on this subject for a better understanding of the role of estrogen and to provide a new insight for treatment and prevention of apoptosis-mediated ocular surface disorders.