The international workshop on meibomian gland dysfunction: report of the subcommittee on anatomy, physiology, and pathophysiology of the meibomian gland

Sjogren's syndrome from the perspective of ophthalmology

Sjogren's syndrome (SS) is an autoimmune disease affecting the lacrimal glands resulting in dry eye disease (DED). Ophthalmologists may be the first line of detection of Sjogren's syndrome given the frequency of DED in SS and that dry eye is often the presenting symptom. Numerous symptom questionnaires and tests have been developed to help diagnose DED, but as of yet, there is no "gold standard." Minimally invasive objective metrics are needed for a reliable diagnosis of DED. Currently there is no single test to diagnose SS-associated DED. Although there are several approaches to treatment, none are specific for DED in SS, and, generally, several methods need to be tried to find what works best for a specific patient. Treatment for DED continues to be an unmet medical need, especially given that DED in SS is typically on the severe end of the spectrum.

The Growing Need for Validated Biomarkers and Endpoints for Dry Eye Clinical Research

Purpose

Biomarkers with minimally invasive and reproducible objective metrics provide the key to future paradigm shifts in understanding of the underlying causes of dry eye disease (DED) and approaches to treatment of DED. We review biomarkers and their validity in providing objective metrics for DED clinical research and patient care.

Methods

The English-language literature in PubMed primarily over the last decade was surveyed for studies related to identification of biomarkers of DED: (1) inflammation, (2) point-of-care, (3) ocular imaging, and (4) genetics. Relevant studies in each group were individually evaluated for (1) methodological and analytical details, (2) data and concordance with other similar studies, and (3) potential to serve as validated biomarkers with objective metrics.

Results

Significant work has been done to identify biomarkers for DED clinical trials and for patient care. Interstudy variation among studies dealing with the same biomarker type was high. This could be attributed to biologic variations and/or differences in processing, and data analysis. Correlation with other signs and symptoms of DED was not always clear or present.

Conclusions

Many of the biomarkers reviewed show the potential to serve as validated and objective metrics for clinical research and patient care in DED. Interstudy variation for a given biomarker emphasizes the need for detailed reporting of study methodology, including information on subject characteristics, quality control, processing, and analysis methods to optimize development of nonsubjective metrics. Biomarker development offers a rich opportunity to significantly move forward clinical research and patient care in DED.

Overview

DED is an unmet medical need - a chronic pain syndrome associated with variable vision that affects quality of life, is common with advancing age, interferes with the comfortable use of contact lenses, and can diminish results of eye surgeries, such as cataract extraction, LASIK, and glaucoma procedures. It is a worldwide medical challenge with a prevalence rate ranging from 8% to 50%. Many clinicians and researchers across the globe are searching for better answers to understand the mechanisms related to the development and chronicity of DED. Though there have been many clinical trials for DED, few new treatments have emerged over the last decade. Biomarkers may provide the needed breakthrough to propel our understanding of DED to the next level and the potential to realize our goal of truly personalized medicine based on scientific evidence. Clinical trials and research on DED have suffered from the lack of validated biomarkers and less than objective and reproducible endpoints. Current work on biomarkers has provided the groundwork to move forward. This review highlights primarily ocular biomarkers that have been investigated for use in DED, discusses the methodologic outcomes in providing objective metrics for clinical research, and suggests recommendations for further work.

Enhanced Tearing by Electrical Stimulation of the Anterior Ethmoid Nerve

Purpose

Electrical neurostimulation enhances tear secretion, and can be applied to treatment of dry eye disease. Using a chronic implant, we evaluate the effects of stimulating the anterior ethmoid nerve on the aqueous, lipid, and protein content of secreted tears.

Methods

Neurostimulators were implanted beneath the nasal mucosa in 13 New Zealand white rabbits. Stimulations (2.3-2.8 mA pulses of 75-875 μs in duration repeated at 30-100 Hz for 3 minutes) were performed daily, for 3 weeks to measure changes in tear volume (Schirmer test), osmolarity (TearLab osmometer), lipid (Oil-Red-O staining), and protein (BCA assay, mass spectrometry).

Results

Stimulation of the anterior ethmoid nerve in the frequency range of 30 to 90 Hz increased tear volume by 92% to 133% (P ≤ 0.01). Modulating the treatment with 50% duty cycle (3 seconds of stimulation repeated every 6 seconds) increased tear secretion an additional 23% above continuous stimulation (P ≤ 0.01). Tear secretion returned to baseline levels within 7 minutes after stimulation ended. Tear film osmolarity decreased by 7 mOsmol/L, tear lipid increased by 24% to 36% and protein concentration increased by 48% (P ≤ 0.05). Relative abundance of the lacrimal gland proteins remained the same, while several serum and corneal proteins decreased with stimulation (P ≤ 0.05).

Conclusions

Electrical stimulation of the anterior ethmoid nerve increased aqueous tear volume, reduced tear osmolarity, added lipid, and increased the concentration of normal tear proteins. Human studies with an intranasal stimulator should verify these effects in patients with aqueous- and lipid-deficient forms of dry eye disease.

Increase in tear film lipid layer thickness after instillation of 3% diquafosol ophthalmic solution in healthy human eyes

PURPOSE

To evaluate the effect of 3% diquafosol ophthalmic solution on tear film lipid layer thickness (LLT) in normal human eyes by tear interferometry.

METHODS

Forty-seven healthy men (mean age of 42.4 years) randomly received one drop of artificial tears in one eye and one drop of 3% diquafosol ophthalmic solution in the other. LLT of each eye was quantified by tear interferometry before and 15, 30, and 60 min after instillation. Ocular symptoms were assessed before and 30 min after instillation. Baseline LLT, tear film breakup time (TBUT), meibomian gland area (meiboscore) of the upper and lower eyelids, and Schirmer test value were evaluated on a different day before treatment.

RESULTS

LLT before and 15, 30, and 60 min after diquafosol instillation was 62.3 ± 31.1, 77.0 ± 39.5, 79.3 ± 40.5, and 77.7 ± 43.6 nm, respectively, with the diquafosol-induced increase in LLT being significant at each time point. Artificial tears did not result in a significant increase in LLT. TBUT (ρ = 0.32, P = 0.026), meiboscore of the lower eyelid (ρ = -0.33, P = 0.022), and the maximum difference in LLT between before and after diquafosol instillation (ΔLLT_max) (ρ = 0.35, P = 0.016) were significantly correlated with baseline LLT in the diquafosol group. Age was not significantly related to baseline LLT or ΔLLT_max. Symptoms did not differ significantly between the two groups.

CONCLUSIONS

Topical instillation of 3% diquafosol ophthalmic solution increased LLT for up to 60 min in normal human eyes regardless of age.

Meibomian Gland Dysfunction Correlates to the Tear Film Instability and Ocular Discomfort in Patients with Pterygium

Pterygium is a very common disease in an eye clinic characterized by a benign proliferation of local conjunctiva that often crosses the limber of cornea and extends into corneal surface. Variety of studies has showed that pterygium is able to result in ocular discomfort and the change of ocular surface environment, such as dry eye. However, the link between abnormal tear film function and pterygium is controversial. Meibomian gland dysfunction (MGD) is a common cause of dry eye and ocular discomfort but is often neglected, which may be the missing link between dry eye and pterygium. In this study, our data firstly revealed increased abnormality of meibomian gland structure and function in pterygium patients, representing with increased abnormality of MGD parameters such as meibum expression (P < 0.001) and meibomian gland loss (P < 0.001). Besides, the scores of MGD severity in patients with progressive pterygium were higher than those in patients with resting pterygium. The correlation between MGD parameters and ocular discomfort as well as dry eye indexes is also established. These findings suggest that MGD correlates to the tear film instability and ocular discomfort in patients with pterygium.

Meibomian Gland Dysfunction in Patients Receiving Long-Term Glaucoma Medications

PURPOSE

The purpose of this study was to evaluate the impact of meibomian gland dysfunction (MGD) on the ocular surface of patients with medically treated glaucoma.

MATERIALS AND METHODS

This was a cross-sectional study in which 70 subjects with glaucoma on long-term (>1 year) topical hypotensive medications were recruited. MGD was defined as the presence of signs consistent with meibomian gland terminal duct obstruction. MGD was categorized between grades 1 and 4 and plus disease according to clinical severity. The ocular surface disease index (OSDI) questionnaire was completed at the time of enrollment. Ocular surface tests consisted of tear break-up time (BUT), ocular surface staining with lissamine green (LG), and Schirmer test with anesthesia. A Student t test, χ test, and Mann-Whitney U test were used in statistical comparisons. Forty-five healthy control subjects with no evidence of intraocular or ocular surface disease were also included.

RESULTS

MGD was detected in 56 (80.0%) subjects with glaucoma. Forty-seven patients (67.1%) had obstructive and 9 (12.9%) had atrophic type of MGD. Of these 56 cases, 47 (83.9%) had signs consistent with mild to moderate MGD. The ocular surface test results of patients with glaucoma with MGD and without MGD were significantly worse (P < 0.001) for all parameters compared with those of healthy controls. However, there were no significant differences between ocular surface disease index scores (P = 0.912), tear break-up time (P = 0.635), lissamine green scores (P = 0.248), and Schirmer results (P = 0.991) between patients with glaucoma with MGD and without MGD.

CONCLUSIONS

Mild to moderate MGD is frequently encountered in patients with medically treated glaucoma. However, the presence of MGD does not appear to have an additional detrimental effect on the ocular surface to that already induced by chronic topical medication use.

Influence of Omega 3 and 6 Fatty Acids on Human Meibomian Gland Epithelial Cells

PURPOSE

Oral supplementation with omega 3 (ω-3) and/or 6 (ω-6) fatty acids (FAs) has been reported to alleviate the signs and symptoms of dry eye disease and to improve the expressibility and quality of meibum, in patients with meibomian gland dysfunction. We tested our hypothesis that these FA effects may reflect a direct FA action on human meibomian gland epithelial cells.

METHODS

Immortalized human meibomian gland epithelial cells (IHMGECs) were cultured with ω-3, ω-6, or both FAs together for up to 7 days in the presence or absence of serum. After FA exposure, cells were analyzed for lipid expression, lysosome content, and proliferative ability.

RESULTS

Our research shows that ω-3 and ω-6 stimulate the accumulation of small neutral lipid-containing vesicles, but not lysosomes, in IHMGECs. This vesicular effect was associated with a 2.4- to 3.7-fold increase in the cellular content of triglycerides after ω-3 and ω-6 treatment, respectively. The combination of both FAs together also enhanced triglyceride levels. Of interest, culture of IHMGECs with ω-3 and azithromycin, a known inducer of IHMGEC differentiation, led to a significantly greater amount of total neutral lipids, relative to that found with azithromycin alone. Cellular exposure to the FAs did not alter the expression of free or esterified cholesterol, or phospholipids. Further, these FAs, alone or together, prevented the proliferation of IHMGECs in serum-free, but not serum-containing, media.

CONCLUSIONS

Our findings support our hypothesis and demonstrate that ω-3 and ω-6 can act directly on IHMGECs to influence the quality and quantity of intracellular lipids.

Meibomian gland morphogenesis requires developmental eyelid closure and lid fusion

BACKGROUND AND PURPOSE

Meibomian glands (MGs) play an important role in the maintenance of ocular surface health, but the mechanisms of their development are still poorly understood. The MGs arise from the epithelium at the junction of eyelid fusion, raising the possibility that defective eyelid fusion disturbs the formation of MGs.

METHODS

We examined, histologically and functionally, the development of MGs in mice with either normal or defective eyelid fusion, displaying eye-closed at birth (ECB) or eye-open at birth (EOB) phenotypes, respectively.

RESULTS

The Meibomian anlage was detected in the epithelium at the eyelid fusion junction immediately after birth at postnatal day 0 (PD0), and it extended into the eyelid stroma at PD1 and started to branch and produce meibum at PD7 in the ECB mice. In contrast, few if any MG structures were detectable in the EOB mice in the early postnatal periods. The Meibomian gland ductile system was seen aligned along the eyelid margin in the adult ECB mice, but was absent or scarce in that of the EOB mice. While MG abnormalities were found in all EOB mice, the severity varied and corresponded to the position and the size of eye opening but not the genetic defects of the mice.

CONCLUSION

Proper Meibomian gland formation and development require eyelid closure and fusion.

Proteolytic activity in the meibomian gland: Implications to health and disease

The function of the meibomian gland in the upper and lower eyelids is critical to maintaining homeostasis at the ocular surface. Highly specialized meibocytes within the gland must differentiate and accumulate intracellular lipid droplets that are released into the tear film following rupture of the cell membrane. Proteases and their inhibitors have been recognized as key players in remodeling extracellular matrices and promoting the normal integrity of glandular tissue. They modulate a wide range of biological processes, such as cell proliferation and differentiation, and can contribute to disease when aberrantly expressed. Deciphering the role of proteolytic activity in the meibomian gland offers an opportunity to gain a more comprehensive and fundamental understanding of the developmental, physiological, and pathological processes associated with this gland.

Role of TGFBIp in Wound Healing and Mucin Expression in Corneal Epithelial Cells

PURPOSE

Transforming growth factor-β-induced protein (TGFBIp) is highly expressed in the cornea, and mutant TGFBIp induces corneal diseases. However, the function of TGFBIp in cornea epithelium is not fully investigated. Here, we tested the importance of TGFBIp in regulation of gene expression and corneal epithelial cell (CEC) activity.

MATERIALS AND METHODS

The effect of TGFBIp on CEC activity was analyzed by cell migration, adhesion, proliferation and wound healing assay. Analysis of gene expression was examined by western blot and quantitative reverse transcription PCR.

RESULTS

The results demonstrated that TGFBIp increased adhesion, migration, proliferation, and wound healing of CECs. Analysis of gene expression presented that TGFBIp-stimulated CECs exhibited increased expression of mucin family genes, such as MUC1, -4, -5AC, and -16. Furthermore, TGFBIp treatment increased the expression of MUC1, -4, -5AC, -7, and -16 in conjunctival epithelial cells. TGFBIp also increased the activity of intracellular signaling molecules ERK and AKT in CECs. Using pharmacologic inhibitors of ERK and AKT, we showed that the expression of mucin genes by TGFBIp is mediated by the activation of ERK and AKT signaling.

CONCLUSION

Our findings demonstrate that the locally generated TGFBIp in the cornea may contribute to wound healing of CECs by enhancing the migration, adhesion, and proliferation of CECs. In addition, our results suggest that TGFBIp has a protective effect on ocular surfaces by inducing the expression of mucin genes in corneal and conjunctival epithelial cells. These data suggest that TGFBIp is a useful therapeutic target for patients with corneal wounds.

Embryologic and Fetal Development of the Human Eyelid

Purpose:

To review the recent data about eyelid morphogenesis, and outline a timeline for eyelid development from the very early stages during embryonic life till final maturation of the eyelid late in fetal life.

Methods:

The authors extensively review major studies detailing human embryologic and fetal eyelid morphogenesis. These studies span almost a century and include some more recent cadaver studies. Numerous studies in the murine model have helped to better understand the molecular signals that govern eyelid embryogenesis. The authors summarize the current findings in molecular biology, and highlight the most significant studies in mice regarding the multiple and interacting signaling pathways involved in regulating normal eyelid morphogenesis.

Results:

Eyelid morphogenesis involves a succession of subtle yet strictly regulated morphogenetic episodes of tissue folding, proliferation, contraction, and even migration, which may occur simultaneously or in succession.

Conclusions:

Understanding the extraordinary process of building eyelid tissue in embryonic life, and deciphering its underlying signaling machinery has far reaching clinical implications beyond understanding the developmental abnormalities involving the eyelids, and may pave the way for achieving scar-reducing therapies in adult mammalian wounds, or control the spread of malignancies.

The authors describe in detail the recent advances in the knowledge of embryological and fetal development of the eyelids, and briefly outline the molecular basis of eyelid morphogenesis.

Meibocyte differentiation and renewal: Insights into novel mechanisms of meibomian gland dysfunction (MGD)

This paper reviews our current understanding of age-related meibomian gland dysfunction (MGD) and the role of the nuclear receptor, peroxisome proliferator-activated receptor gamma (PPARγ), in the regulation of meibomian gland function, meibocyte differentiation and lipid synthesis. The studies suggest that PPARγ is a master regulator of meibocyte differentiation and function, whose expression and nuclear signaling coupled with meibocyte renewal is altered during aging, potentially leading to atrophy of the meibomian gland as seen in clinical MGD. Study of meibomian gland stem cells also suggest that there is a limited number of precursor meibocytes that provide progeny to the acini, that may be susceptible to exhaustion as occurs during aging and other environmental factors. Further study of pathways regulating PPARγ expression and function as well as meibocyte stem cell maintenance may provide clues to establishing cellular and molecular mechanisms underlying MGD and the development of novel therapeutic strategies to treating this disease.

A Novel Model of Meibomian Gland Dysfunction Induced with Complete Freund's Adjuvant in Rabbits

A novel meibomian gland dysfunction (MGD) model induced by the injection of complete Freund’s adjuvant (CFA) in rabbits was developed to facilitate the understanding of the pathophysiology of MGD with meibomitis. In addition, we sought to evaluate treatment with steroid eye drops in this model. Male Japanese white rabbits were subcutaneously injected with CFA into the upper eyelid margin. The eyelid margins of the rabbits were chronologically observed through slit lamp examination. The development of meibomitis was assessed through histopathology. We evaluated the effects of topically applied tobramycin/dexamethasone (Tob/Dex) eye drops on the plugged orifices and telangiectasia. After the injection of CFA, slit lamp examination revealed markedly plugged orifices, telangiectasia around the orifices and a toothpaste-like meibum, as compared with the normal eyelids. Histopathology revealed granulation tissue with infiltration of inflammatory cells, hyperkeratinization of the ductal epithelium, and cystic dilatation of ducts in the meibomian gland. The orifices were plugged with a proteinaceous substance. Tob/Dex eye drops significantly suppressed the plugging and telangiectasia around the orifices. Through the injection of CFA, we successfully established a novel rabbit MGD that mimics the symptoms observed in humans meibomitis. This model should be useful in the evaluation of the efficacy of drug candidates.

A Metabolome-Wide Study of Dry Eye Disease Reveals Serum Androgens as Biomarkers

PURPOSE

To test the association between serum metabolites and dry eye disease (DED) using a hypothesis-free metabolomics approach.

DESIGN

Cross-sectional association study.

PARTICIPANTS

A total of 2819 subjects from the population-representative TwinsUK cohort in the United Kingdom, with a mean age of 57 years (range, 17-82 years).

METHODS

We tested associations between 222 known serum metabolites and DED. All subjects underwent nontargeted metabolomic analysis of plasma samples using gas and liquid chromatography in combination with mass spectrometry (Metabolon Inc., Durham, NC). Dry eye disease was defined from the validated Short Questionnaire for Dry Eye Syndrome (SQDES) as a previous diagnosis of DED by a clinician or "often" or "constant" symptoms of dryness and irritation. Analyses were performed with linear mixed effect models that included age, BMI, and sex as covariates, corrected for multiple testing.

MAIN OUTCOME MEASURES

Primary outcome was DED as defined by the SQDES, and secondary outcomes were symptom score of DED and a clinical diagnosis of DED.

RESULTS

Prevalence of DED as defined by the SQDES was 15.5% (n = 436). A strong and metabolome-wide significant association with DED was found with decreased levels of the metabolites androsterone sulfate (P = 0.00030) and epiandrosterone sulfate (P = 0.00036). Three other metabolites involved in androgen metabolism, 4-androsten-3beta,17beta-diol disulfate 1 and 2, and dehydroepiandrosterone sulfate, were the next most strongly associated of the 222 metabolites, but did not reach metabolome-wide significance. Dryness and irritation symptoms, as opposed to a clinical diagnosis, were particularly strongly associated with decreased androgen steroid metabolites, with all reaching metabolome-wide significance (androsterone sulfate, P = 0.000000029; epiandrosterone sulfate, P = 0.0000040; 4-androsten-3beta,17beta-diol disulfate 1, P = 0.000016; 4-androsten-3beta,17beta-diol disulfate 2, P = 0.000064; and dehydroepiandrosterone sulfate, P = 0.00011). Of these 5 androgens, epiandrosterone sulfate (P = 0.0076) was most associated with 2-year incidence of clinician-diagnosed DED. In addition, we found decreased glycerophosphocholines to be associated with DED, although not at metabolome-wide significance.

CONCLUSIONS

This hypothesis-free metabolomic approach found decreased serum androgens to be highly associated with DED and adds important evidence to the growing body of research that links androgens to ocular surface disease and DED.

Emerging strategies for the diagnosis and treatment of meibomian gland dysfunction: Proceedings of the OCEAN group meeting

Meibomian gland dysfunction (MGD) is a common and chronic disorder that has a significant adverse impact on patients' quality of life. It is a leading cause of evaporative dry eye disease (DED), as meibomian glands play an important role in providing lipids to the tear film, which helps to retard the evaporation of tears from the ocular surface. MGD is also often present in conjunction with primary aqueous-deficient DED. Obstructive MGD, the most commonly observed type of MGD, is the main focus of this article. MGD is probably caused by a combination of separate conditions: primary obstructive hyperkeratinization of the meibomian gland, abnormal meibomian gland secretion, eyelid inflammation, corneal inflammation and damage, microbiological changes, and DED. Furthermore, skin diseases such as rosacea may play a part in its pathology. Accurate diagnosis is challenging, as it is difficult to differentiate between ocular surface diseases, but is crucial when choosing treatment options. Ocular imaging has advanced in recent years, providing ophthalmologists with a better understanding of ocular diseases. This review presents a literature update on the 2011 MGD workshop and an optimized approach to accurate diagnosis of MGD using currently available methods and tests. It also outlines the emerging technologies of interferometry, non-contact meibography, keratography and in vivo confocal laser microscopy, which offer exciting possibilities for the future. Selected treatment options for MGD are also discussed.

The Limitation of Applying Heat to the External Lid Surface: A Case of Recalcitrant Meibomian Gland Dysfunction

The effects on the inner surface temperatures of the upper and lower eyelids of four commercial heat therapies were compared for an individual with recalcitrant meibomian gland dysfunction. Three therapies (Bruder mask, Blephasteam, and MiBoFlo) involved the application of heat to the external lid surface, and the fourth (LipiFlow) applied heat to the internal lid surface. Only LipiFlow was effective in elevating the inner surface temperatures to the reported 40°C therapeutic threshold for melting obstructed meibum.

Zone I of Tear Microdesiccates Is a Lipid-Containing Structure

PURPOSE

Morphological features of tear microdesiccates on glass surfaces have been associated with tear fluid status. Tear-film lipids play a critical role in the pathophysiology of some ocular surface disorders. Tear microdesiccates display 4 distinctive morphological domains (zones I, II, III, and transition band). In this study, we investigated the lipid location in tear microdesiccates.

METHODS

Tear from individual healthy eyes (assessed by symptoms, signs, and slit-lamp examination) was collected using absorbing minisponges. One-µL aliquots were allowed to dry under ambient conditions on microscope slides. Tear microdesiccates were examined by various transmitted light microscopy methods. Tear lipids were located both by partition experiments using 2 lipophilic dyes (Oil red O and Nile blue A) mixed with tear fluid under conditions preserving morphological features of microdesiccates and by assessing the effect of 2 solvents markedly differing in polarity (water and ethanol) on the morphology of particular domains of preformed microdesiccates.

RESULTS

During desiccation, both Nile blue A and Oil red O became preferentially located in the outermost domain of tear microdesiccates (zone I) without affecting the formation of major fern-like crystalloids (zones II and III). Low volumes of water drastically affected fern-like crystalloids, whereas the gross morphology of zone I was maintained. Contrarily, ethanol, a less polar solvent, was a fixative for fern-like crystalloids, although it markedly affected the bulk of zone I by extracting liquid droplets out of microdesiccates and visibilizing some filamentous subcomponents.

CONCLUSIONS

Zone I is a hydrophobic domain, whereas zones II and III are highly hydrophilic domains of tear microdesiccates. Zone I represents a lipid-rich structure.

Impact of Chronic Smoking on Meibomian Gland Dysfunction

Purpose

The aim of this study was to explore the relationship between chronic cigarette smoking and meibomian gland dysfunction (MGD).

Methods

This study enrolled 322 smokers with MGD and 2067 non-smokers with MGD. All enrolled subjects were tested in the following sequence: Ocular Surface Disease Index (OSDI), tear film breakup time (TBUT), corneal fluorescein staining (CFS), Schirmer I test (SIT)and finally slit-lamp microscope examination of lid margin abnormalities, meibomian gland expression as well as meibum.

Results

Compared with the MGD patients without smoking, the MGD patients with smoking had significantly increased scores of lid margin abnormality and meibum (P<0.01 for each comparison). No significant difference was noted in OSDI, TBUT, CFS, SIT or the score of Meibomian gland expressibility between the smokers and non-smokers (P>0.05 for each comparison). In the smokers, the smoking index was significantly correlated with the scores of lid margin abnormality (Both sexes, R = 0.19, P<0.01; Male, R = 0.18, P<0.01) and meibum (Both sexes, R = 0.29, P<0.01; Male, R = 0.20, P<0.01), whereas it was not significantly correlated with OSDI, TBUT, CFS, SIT or score of Meibomian gland expressibility (P>0.05 for each comparison).

Conclusion

The findings of this study suggest chronic smoking might be associated with MGD.

Changes of meibomian glands in patients with type 2 diabetes mellitus

AIM

To investigate the morphological changes of meibomian glands in patients with type 2 diabetes mellitus (DM).

METHODS

Of 118 eyes (118 patients) with type 2 DM (DM group) and 100 eyes of 100 control subjects (control group) were enrolled. After completing an ocular surface disease index (OSDI) questionnaire, the non-invasive tear film break-up time (NI-BUT) and the structure of the meibomian glands (MGs, meibography) were assessed by the Keratograph 5M system. Partial or complete loss of MG was scored for each eyelid from grade 0 (no loss) to grade 3 (lost area was >2/3 of the total MG area), which were also examined by laser scanning confocal microscopy (LSCM). The primary outcomes were meibomian gland acinar unit density (MGAUD), meibomian gland acinar longest diameter (MGALD) and meibomian gland acinar shortest diameter (MGASD).

RESULTS

Compared with control group, the OSDI was significantly higher in DM group (Z=-5.916; P<0.001), while the NI-BUT was significantly lower (Z=-7.765; P<0.001). Keratograph showed that there were more MGs dropout in DM group than that in control group. The meiboscore was significantly higher in DM group compared with control group (Z=-3.937; P<0.001). LSCM revealed that there were cytological alterations of MGs in DM group compared with control group, which included enlargement of MG acinar units and decreased in density of MG acinar units. Specifically, there were lower MGAUD, larger MGALD and MGASD in DM group than control group (Z=-10.120, -9.4442, -7.771; P<0.001).

CONCLUSION

Compared with the normal control participants, the patients with type 2 DM had more unstable tear films and severe symptoms of dry eye. Using Keratograph 5M system and LSCM, we found that the patients with type 2 DM had more significant morphological and cytological changes and dysfunction in MGs.

Genetically modified laboratory mice with sebaceous glands abnormalities

Sebaceous glands (SG) are exocrine glands that release their product by holocrine secretion, meaning that the whole cell becomes a secretion following disruption of the membrane. SG may be found in association with a hair follicle, forming the pilosebaceous unit, or as modified SG at different body sites such as the eyelids (Meibomian glands) or the preputial glands. Depending on their location, SG fulfill a number of functions, including protection of the skin and fur, thermoregulation, formation of the tear lipid film, and pheromone-based communication. Accordingly, SG abnormalities are associated with several diseases such as acne, cicatricial alopecia, and dry eye disease. An increasing number of genetically modified laboratory mouse lines develop SG abnormalities, and their study may provide important clues regarding the molecular pathways regulating SG development, physiology, and pathology. Here, we summarize in tabulated form the available mouse lines with SG abnormalities and, focusing on selected examples, discuss the insights they provide into SG biology and pathology. We hope this survey will become a helpful information source for researchers with a primary interest in SG but also as for researchers from unrelated fields that are unexpectedly confronted with a SG phenotype in newly generated mouse lines.

Risk Factors and Symptoms of Meibomian Gland Loss in a Healthy Population

Purpose. The aim of this study was to investigate the relationships between MGL and ocular symptoms, several systemic conditions, and key markers of ocular surface health. Methods. We included into the study 91 healthy volunteers between the ages of 20 and 77 years. We analyzed meibomian gland morphology, function, and lid margin alterations. We correlated our findings with self-reported ocular symptoms, systemic medical history, lifestyle factors, and tear film abnormalities. Results. We observed that a high ocular surface disease index, a history of either chalazion or hordeolum, experience of puffy eyelids upon waking, and foreign body sensation all appeared to be predictors of an abnormal meiboscore after adjusting for age and sex (p = 0.0007; p = 0.001; p = 0.02; p = 0.001, resp.). Multivariate logistic regression model including age and sex showed that there were three independent predictors of abnormal meiboscore: older age (OR = 1.03, 95% CI = 1.01–1.04 per year, p = 0.006), postmenopausal hormone therapy (OR = 4.98, 95% CI = 1.52–16.30, p = 0.007), and the use of antiallergy drugs (OR = 5.85, 95% CI = 2.18–15.72, p = 0.0004). Conclusion. Our findings extend current knowledge on the pathophysiology of MGL.

Assessment of the Tear Film Lipid Layer Thickness after Cataract Surgery

PURPOSE

To evaluate changes in the tear film lipid layer thickness (LLT) after cataract surgery and the effects of cataract surgery on dry eye syndrome (DES) and meibomian gland dysfunction (MGD).

METHODS

LLT measurements obtained using the LipiView interferometer, tear break-up time (TBUT) measurements, Schirmer's tests, Oxford staining scores, lid margin and meibomian gland findings, and the Ocular Surface Disease Index (OSDI) questionnaire scores were evaluated before and one and three months after cataract surgery.

RESULTS

Forty-three eyes (43 patients) were included. LLT was significantly thinner one month after surgery than at baseline (P = 0.004). TBUT was significantly shorter at both one (P < 0.001) and three (P < 0.001) months after surgery than at baseline. OSDI scores were significantly higher (P < 0.001) and the meibum quality was significantly poorer (P = 0.001) at one month after surgery than at baseline. TBUT was significantly and positively correlated with LLT (r = 0.29, P < 0.001), while the OSDI (r = -0.38, P < 0.001) and Oxford staining (r = -0.30, P = 0.001) scores and the meibum quality (r = -0.21, P = 0.01) were significantly and negatively correlated with LLT.

CONCLUSIONS

The tear film LLT was significantly thinner and DES and MGD parameters showed deterioration after cataract surgery. In addition, LLT was significantly correlated with DES and MGD parameters. These results suggest that clinicians should consider the tear film lipid layer while managing the exacerbation of DES after cataract surgery.

Characterization of Rat Meibomian Gland Ion and Fluid Transport

Purpose

We establish novel primary rat meibomian gland (MG) cell culture systems and explore the ion transport activities of the rat MG.

Methods

Freshly excised rat MG tissues were characterized as follows: (1) mRNA expression of selected epithelial ion channels/transporters were measured by RT-PCR, (2) localization of epithelial sodium channel (ENaC) mRNAs was performed by in situ hybridization, and (3) protein expression and localization of βENaC, the Na⁺/K⁺/Cl⁻ cotransporter (NKCC), and the Na⁺/K⁺ ATPase were evaluated by immunofluorescence. Primary isolated rat MG cells were cocultured with 3T3 feeder cells and a Rho-associated kinase (ROCK) inhibitor (Y-27632) for expansion. Passaged rat MG cells were cultured as planar sheets under air-liquid interface (ALI) conditions for gene expression and electrophysiologic studies. Passaged rat MG cells also were cultured in matrigel matrices to form spheroids, which were examined ultrastructurally by transmission electron microscopy (TEM) and functionally using swelling assays.

Results

Expression of multiple ion channel/transporter genes was detected in rat MG tissues. β-ENaC mRNA and protein were localized more to MG peripheral acinar cells than central acinar cells or ductular epithelial cells. Electrophysiologic studies of rat MG cell planar cultures demonstrated functional sodium, chloride, and potassium channels, and cotransporters activities. Transmission electron microscopic analyses of rat MG spheroids revealed highly differentiated MG cells with abundant lysosomal lamellar bodies. Rat MG spheroids culture-based measurements demonstrated active volume regulation by ion channels.

Conclusions

This study demonstrates the presence and function of ion channels and volume transport by rat MG. Two novel primary MG cell culture models that may be useful for MG research were established.

Compositional Analysis of Wax Esters in Human Meibomian Gland Secretions by Direct Infusion Electrospray Ionization Mass Spectrometry

Wax esters (WE) are one of the predominant lipid types in human meibomian gland secretions (meibum) and account for 40-50 % of total meibum lipids. Recently, we managed to quantify 51 isomeric groups of intact WE in normal human meibum samples by direct infusion electrospray ionization mass spectrometry (ESI-MS), with each WE peak in the MS spectrum corresponding to one isomeric group (Chen et al, Invest Ophthalmol Vis Sci 54(8):5730-53, 2013). However, the information of the isomeric composition in each group was not obtained. In this study, tandem mass spectrometry (MS/MS) was applied to quantify relative amounts of these isomers using the intensities of the corresponding diagnostic ions after appropriate correction and normalization. This data was combined with the previous obtained mole fraction of each isomeric group to total WE in human meibum to determine the corresponding percentage of each isomer. A total of 23 of the most abundant WE peaks of different molecular weights (corresponding to 85.3 % of the total amount of WE) in human meibum were studied and resulted in quantification of 92 WE species. The quantitative information of composition of WE in human meibum will help better understand their role in the tear film.

PPARγ Regulates Mouse Meibocyte Differentiation and Lipid Synthesis

PURPOSE

Previous reports suggest that age-related meibomian gland atrophy is associated with decreased expression of the lipid-sensitive nuclear receptor, PPARγ. The purpose of this study was to identify the role of PPARγ in modulating meibocyte lipid synthesis.

METHODS

Cytoplasmic and nuclear fractions from meibomian glands of young (2M) and old (2Y) C57Bl6 mice were probed using antibodies specific for PPARγ. Mouse meibocytes were cultured, immortalized using a SV40 lentiviral vector, and evaluated for lipid synthesis using LipidTox staining and CARS/Raman microspectroscopy. Lipid synthesizing clones were tested for effects of PPARγ agonist, rosiglitazone, on lipid synthesis and PPARγ localization, post-translational modification and induction of PPARγ response genes.

RESULTS

The cytoplasmic fraction in young mice contained both 50 and 72 kDa PPARγ bands that were absent or reduced by 75% in older mice, respectively. Cultured meibocytes produced neutral lipid containing equal amounts of wax and cholesterol esters, similar to mouse meibum. Addition of rosiglitazone (10-50 μM) significantly increased lipid production (P<.05) in meibocytes, associated with SUMO1 sumoylation and cytoplasmic accumulation of the 72 kDa PPARγ. Rosiglitazone also increased the localization of PPARγ to the cytoplasm and up-regulated of PPARγ, ADP and ADFP mRNA.

CONCLUSIONS

This study confirms the loss of cytoplasmic/vesicular PPARγ localization in older, atrophic mouse meibomian glands. Furthermore, PPARγ stimulates lipid synthesis in mouse meibocytes, associated with PPARγ sumoylation and translocation to the cytoplasm. Taken together these data suggest that lipid synthesis in older mice is down regulated by a PPARγ mediated pathway.

Renewal of the Holocrine Meibomian Glands by Label-Retaining, Unipotent Epithelial Progenitors

The meibomian and sebaceous glands secrete lipids to prevent desiccation of the ocular surface and skin, respectively. Precisely how these holocrine tissues regenerate is not well understood. To address this, we characterized keratin 5(+) (K5) label-retaining cells (LRCs) and the lineage tracing of keratin 14 (K14) progenitors in mouse meibomian glands. Using the tet-off H2B-GFP/K5tTA mouse, H2B-GFP fluorescence dilutes 2-fold with every division in K5(+) cell nuclei after doxycycline administration. In 3D reconstructions generated over a >28-day doxycycline chase, we observed LRCs at the acinus entrance where K6(+) ductal epithelium terminates. For lineage tracing, K14CreER(T2)-Confetti mice were injected intraperitoneally with tamoxifen and euthanized at 23 and 59 weeks later. Meibomian gland acini in these mice were either monochromatic or dual-colored, whereas the duct exhibited multiple colors. In conclusion, LRCs are likely to direct meibomian gland turnover and may exist as two distinct unipotent progenitors that renew ductal and acinar tissue separately.

Notch Signaling in Meibomian Gland Epithelial Cell Differentiation

Purpose

Notch1 was previously shown to play a critical role in murine meibomian gland function and maintenance. In this study, we have examined the expression and activation of Notch pathway in human meibomian gland epithelial cells in vitro.

Methods

An immortalized human meibomian gland epithelial cell (HMGEC) line was cultured under proliferative and differentiative conditions. Expression of Notch receptors and ligands were evaluated by quantitative PCR and Western blot. The effect of Notch inhibition and induction on oil production was also assessed.

Results

Human meibomian gland epithelial cell expressed Notch1, Notch2, Notch3, Jagged1, Jagged2, Delta-like 1, and Delta-like 3. The level of cleaved (activated) Notch1 strongly increased with differentiation. The expression of Notch3 was inversely correlated with proliferation. Induction and inhibition of Notch1 led to an increase and decrease in the amount of oil production, respectively.

Conclusions

Notch signaling appears to play an important role in human meibomian gland epithelial differentiation and oil production. This may provide a potential therapeutic pathway for treating meibomian gland dysfunction.

Association Between Serum Levels of Testosterone and Estradiol With Meibomian Gland Assessments in Postmenopausal Women

Purpose

The aims of this analysis were to determine if there is an association between serum levels of testosterone and estradiol with meibomian gland (MG) morphology and lipid layer thickness.

Methods

The data used for this analysis were collected from postmenopausal women with and without dry eye disease. Meibography was used to assess MG dropout on the central two-thirds of the eyelid and biomicroscopy was used for assessing MG expressibility and meibum quality. Venous blood samples were drawn for serum hormone level analysis. The Kruskal-Wallis test and Spearman correlations were used for statistical analysis.

Results

One hundred ninety-eight postmenopausal women with an average age of 61.2 (±9.1) years were included in this analysis. Testosterone levels showed significant differences between MG dropout grades 1 and 4 (P = 0.002) and grades 2 and 4 (P = 0.01), whereas estradiol levels were different based on MG dropout (P = 0.53). No significant correlations were found between testosterone (r = 0.10, P = 0.17) or estradiol (r = 0.05, P = 0.45) and lipid layer thickness.

Conclusions

Testosterone levels were increased with MG dropout, which was significant between the mild and severe dropout groups, whereas no significant differences were found with estradiol and any MG assessment. Although the literature suggests an association of serum hormone levels and pathogenesis of dry eye disease in postmenopausal women, analysis of active sex steroid precursors and local tissue hormone levels may prove more useful.

Ocular Surface Disease in Breast Cancer Patients Using Aromatase Inhibitors

Aromatase inhibitors (AIs) are widely used as adjuvant hormonal therapy in postmenopausal women with hormone receptor-positive breast cancer. The purpose of this study was to investigate the potential impact of AIs on the anterior segment of the eye and especially the ocular surface. Participants in our study were 41 hormone receptor-positive early stage breast cancer patients (80 eyes), treated with AIs, while 80 eyes of 40 age- and gender-matched healthy controls, not previously used AIs for any purpose, were also evaluated. All participants underwent a complete ophthalmological examination, including best corrected visual acuity (BCVA) assessment, slit-lamp biomicroscopy, and dilated fundus examination. Ocular surface disease-related symptoms and signs were also recorded. The most common symptom was found to be blurred vision, while other symptoms included foreign body sensation, tearing, redness, and photophobia. Slit-lamp examination revealed blepharitis and meibomian gland dysfunction in 75% and 42.5% of patients, respectively. Superficial punctate keratitis and conjunctival injection were also present. Our results demonstrated a high prevalence of ocular surface disease-related symptoms and signs in patients receiving AIs compared to healthy controls. This study may raise a flag regarding the use of AIs. However, further and larger prospective longitudinal studies are needed to examine the possible effect of AIs alone or in combination with chemotherapy in the eyes of breast cancer patients.

A quantitative method for assessing the quality of meibomian glands

INTRODUCTION

Meibomian gland dysfunction is a common cause of dry eye syndrome which can also lead to eyelid inflammation. Today, diagnostics of meibomian glands is not fully automatic yet and is based on a qualitative assessment made by an ophthalmologist. Therefore, this article proposes a new automatic analysis method which provides a quantitative assessment of meibomian gland dysfunction.

METHOD

The new algorithm involves a sequence of operations: image acquisition (acquisition of data from OCULUS Keratograph® 5M); image pre-processing (image conversion to gray levels, median filtering, removal of uneven lighting, normalization); main image processing (binarization, morphological opening, labeling, Gaussian filtering, skeletonization, distance transform, watersheds). The algorithm was implemented in Matlab with Image Processing Toolbox (Matlab: Version 7.11.0.584, R2010b) on a PC running Windows 7 Professional, 64-bit with the Intel Core i7-4960X CPU @ 3.60GHz.

RESULTS AND CONCLUSIONS

The algorithm described in this article has the following features: it is fully automatic, provides fully reproducible results - sensitivity of 99.3% and specificity of 97.5% in the diagnosis of meibomian glands, and is insensitive to parameter changes. The time of image analysis for a single subject does not exceed 0.5s. Currently, the presented algorithm is tested in the Railway Hospital in Katowice, Poland.

In vivo confocal microscopy of meibomian glands in primary blepharospasm: A prospective case-control study in a Chinese population

The aim of the study was to evaluate the morphological changes of meibomian glands (MGs) in primary blepharospasm (PBS) by in vivo laser scanning confocal microscopy (LSCM) and to investigate the correlations between clinical data of PBS and LSCM parameters of MGs. This prospective and case-control study recruited 30 consecutive PBS patients and 30 age- and gender-matched healthy controls. After questionnaire assessments of ocular surface disease index (OSDI), Jankovic rating scale, and blepharospasm disability index, all subjects underwent blink rate evaluation, tear film break-up time (TBUT), corneal fluorescein staining (CFS), Schirmer test, MG expressibility, meibum quality, MG dropout, and LSCM examination of the MGs. The main LSCM outcomes included the mean MG acinar area and density, orifice diameter, meibum secretion reflectivity, acinar irregularity, and inhomogeneity of interstice and acinar wall. The PBS patients had significantly higher blink rate, higher OSDI and CFS scores, lower TBUT and Schirmer test value, and worse MG expressibility than the controls (All P < 0.05), whereas meibum quality showed no difference (P > 0.05). The PBS patients showed lower values of MG acinar area, orifice diameter and meibum secretion reflectivity, and higher scores of acinar irregularity and inhomogeneity of interstices than the controls (All P < 0.05). For the PBS patients, the severity of blepharospasm evaluated by JCR scale was strong correlated with MG acinar area (P < 0.001), orifice diameter (P = 0.002), meibum secretion reflectivity (P = 0.002), and MG acinar irregularity (P = 0.013). The MG expressibility was significantly correlated to MG acinar area (P = 0.039), orifice diameter (P < 0.001), and MG acinar irregularity (P = 0.014). The OSDI score was moderate correlated with MG acinar irregularity (P = 0.016), whereas the TBUT value was positively correlated with MG acinar area (P = 0.045) and negatively correlated to MG acinar irregularity (P = 0.016). The CFS score was negatively correlated to MG orifice diameter (P = 0.008). The LSCM provided a noninvasive tool for in vivo histopathologic studies of MGs in PBS patients. The excessive constriction of lid muscles closely related to MG morphological alterations of PBS, which offered a new research approach to interpret the interactional mechanism between dry eye and PBS.

Reduced ocular surface disease index (OSDI) scores in patients with isotretinoin treatment

To evaluate the changes in ocular surface and functions of tear-film in patients treated with systemic isotretinoin, to assess diagnostic performance of ocular surface disease index (OSDI) test in the dry eye conditions in association with the use of isotretinoin, and to determine the correlation between all tear-film function tests, OSDI and the dose and duration of isotretinoin administration. One hundred and twenty eyes of 60 subjects treated with oral isotretinoin were enrolled. All patients underwent ophthalmic examination at the baseline and another examination during the course of treatment. Biomicroscopic ophthalmic examination of the meibomian glands, non-anesthetized Schirmer test, and tear film break-up time (BUT) were performed. Subjective ocular complaints were scored with an OSDI questionnaire. Average Schirmer scores were not significantly changed by isotretinoin treatment. There were significant differences in the average OSDI score, the average meibomian gland disease (MGD) grade and average BUT value of both eyes during the treatment compared with baseline values (p < 0.01). There was a statistically significant inverse correlation between MGD grade and BUT value. There was no significant correlation between BUT value, OSDI score, Schirmer score, MGD grade, the total and divided dose of isotretinoin and the duration of treatment. The follow-up time was 4.01 ± 1.3 months (range 1.5-6 months). Systemic isotretinoin treatment can cause alterations in the tear film and dry eye symptoms. The OSDI test can be used as a diagnostic test for patients receiving systemic isotretinoin treatment.

Effects of Insulin and High Glucose on Human Meibomian Gland Epithelial Cells

PURPOSE

Type 2 diabetes is a risk factor for meibomian gland dysfunction (MGD). We hypothesize that this diabetic impact is due, at least in part, to the effects of insulin resistance/deficiency and hyperglycemia on human meibomian gland epithelial cells (HMGECs). To begin to test this hypothesis, we examined whether insulin and high glucose influence immortalized (I) HMGECs.

METHODS

Immortalized HMGECs were cultured in serum-containing or -free media and treated with insulin, insulin-like growth factor-1 (IGF-1), IGF-1 receptor (R) blocking antibody, and glucose or mannitol for varying time periods. Specific proteins were detected by Western blots, cell proliferation was evaluated by manual cell counting and lipids were assessed with LipidTOX and high performance thin layer chromatography.

RESULTS

We found that insulin induces a dose-dependent increase in phosphatidylinositide 3-kinase/Akt (AKT) signaling in IHMGECs. This effect involves the IGF-1R, but not the insulin receptor (IR), and is associated with a stimulation of cell proliferation and neutral lipid accumulation. In contrast, high glucose exposure alters cell morphology, causes a progressive cell loss, and significantly reduces the levels of IGF-1R, phospho (p)-AKT, Foxhead box protein O1 (FOXO1), and sterol-regulatory element binding protein (SREBP-1) in IHMGECs.

CONCLUSIONS

Our data show that insulin stimulates, and that high glucose is toxic for, IHMGECs. These results support our hypothesis that insulin resistance/deficiency and hyperglycemia are deleterious for HMGECs and may help explain why type II diabetes is a risk factor for MGD.

Lid wiper epitheliopathy

Some recent research has resulted in a hypothesis that there is a common 'lid wiper' region that is apposite to the ocular surface or anterior lens surface (where contact lenses are worn), responsible for spreading tears during blinking. In the upper eyelid, it extends about 0.6 mm from the crest of the sharp posterior (inner) lid border (i.e. the mucocutaneous junction, or line of Marx) to the subtarsal fold superiorly and from the medial upper punctum to the lateral canthus horizontally. Histologically, it is seen as an epithelial elevation comprising of stratified epithelium with a transitional conjunctival structure of (moving posteriorly) squamous cells then cuboidal cells, with some parakeratinised cells and goblet cells. Lid wiper epitheliopathy (LWE) denotes staining of the lid wiper observed after instillation of dyes such as fluorescein, rose bengal or lissamine green. There have been some reports of higher rates of LWE in dry eye patients and contact lens wearers, but others have failed to find such associations. The primary cause of LWE is thought to be increased friction between the lid wiper and ocular or anterior contact lens surface due to inadequate lubrication, which could be caused by dry eye and may be exacerbated by factors such as abnormal blinking patterns, poor contact lens surface lubricity and adverse environmental influences. Recent evidence suggests that LWE is associated with sub-clinical inflammation. LWE has the potential to provide the missing mechanistic link between clinical observation and symptoms associated with dry eye and contact lens wear. Clinical and fundamental research into LWE is still in its infancy and in many instances equivocal; however, it is an idea that provides a potentially important new avenue for further investigation of anterior eye discomfort associated with ocular dryness and contact lens wear.

Evaluation of Optical Coherence Tomography Meibography in Patients With Obstructive Meibomian Gland Dysfunction

PURPOSE

To evaluate optical coherence tomography meibography (OCT-M) in patients with and without obstructive meibomian gland dysfunction (MGD) and to determine the relationship between OCT-M and ocular surface clinical tests.

METHODS

Twenty-two patients with MGD and 16 control subjects were included. Each patient underwent an evaluation of ocular surface disease symptoms, lid margin abnormality score, lipid layer thickness evaluation, and meibomian gland (MG) morphological changes using noncontact infrared meibography and OCT-M. OCT-M scans were acquired in 4 different locations. OCT-M parameters including the MG length and width and palpebral conjunctival thickness were evaluated.

RESULTS

Within the OCT-M parameters, the mean length and width of MGs were significantly decreased in patients with MGD (310 ± 60 μm and 214 ± 30 μm, respectively) compared with the control group (361 ± 53 μm, P = 0.041 and 264 ± 41 μm, P = 0.021, respectively). The mean conjunctival thickness was also significantly increased in patients with MGD (448 ± 68 μm) than in the control group (356 ± 59 μm, P = 0.03). The mean length of MGs was correlated with symptoms (r = 0.34, P = 0.034), and the mean MG width was correlated with tear film breakup time (r = -0.412, P = 0.009) and the lid margin abnormality score (r = 0.334, P = 0.038).

CONCLUSIONS

The MG length and width were significantly decreased in patients with MGD than in the control group. These parameters were correlated to both ocular surface symptoms and clinical signs. This new imaging technique may be a useful tool for MGD evaluation.

Sebaceous lipids are essential for water repulsion, protection against UVB-induced apoptosis and ocular integrity in mice

Sebocytes, which are characterized by lipid accumulation that leads to cell disruption, can be found in hair follicle-associated sebaceous glands (SGs) or in free SGs such as the Meibomian glands in the eyelids. Because genetic tools that allow targeting of sebocytes while maintaining intact epidermal lipids are lacking, the relevance of sebaceous lipids in health and disease remains poorly understood. Using Scd3, which is expressed exclusively in mature sebocytes, we established a mouse line with sebocyte-specific expression of Cre recombinase. Both RT-PCR analysis and crossing into Rosa26-lacZ reporter mice and Kras(G12D) mice confirmed Cre activity specifically in SGs, with no activity in other skin compartments. Importantly, loss of SCD3 function did not cause detectable phenotypical alterations, endorsing the usefulness of Scd3-Cre mice for further functional studies. Scd3-Cre-induced, diphtheria chain A toxin-mediated depletion of sebaceous lipids resulted in impaired water repulsion and thermoregulation, increased rates of UVB-induced epidermal apoptosis and caused a severe pathology of the ocular surface resembling Meibomian gland dysfunction. This novel mouse line will be useful for further investigating the roles of sebaceous lipids in skin and eye integrity.

In Vivo Laser Scanning Confocal Microscopy of Human Meibomian Glands in Aging and Ocular Surface Diseases

Meibomian glands (MGs) play a crucial role in the ocular surface homeostasis by providing lipids to the superficial tear film. Their dysfunction destabilizes the tear film leading to a progressive loss of the ocular surface equilibrium and increasing the risk for dry eye. In fact, nowadays, the meibomian gland dysfunction is one of the leading causes of dry eye. Over the past decades, MGs have been mainly studied by using meibography, which, however, cannot image the glandular structure at a cellular level. The diffusion of the in vivo laser scanning confocal microscopy (LSCM) provided a new approach for the structural assessment of MGs permitting a major step in the noninvasive evaluation of these structures. LSCM is capable of showing MGs modifications during aging and in the most diffuse ocular surface diseases such as dry eye, allergy, and autoimmune conditions and in the drug-induced ocular surface disease. On the other hand, LSCM may help clinicians in monitoring the tissue response to therapy. In this review, we summarized the current knowledge about the role of in vivo LSCM in the assessment of MGs during aging and in the most diffuse ocular surface diseases.