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Nguyen A, Naidoo KK, Ajouz L, Xu X, Zhao C, Robinson MR, Borchman D. Changes in Human Meibum Lipid Composition Related to the Presence and Severity of Meibomian Gland Dysfunction. J Ocul Pharmacol Ther 2024. [PMID: 39150383 DOI: 10.1089/jop.2024.0063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/17/2024] Open
Abstract
Purpose: Changes in meibum composition and quantity in meibomian gland dysfunction (MGD) result in tear film instability and dry eye. This exploratory study aimed to identify changes in (O-acyl)-ω-hydroxy fatty acid (OAHFA) and hydrocarbon chain (HC) unsaturation levels in meibum related to the presence and severity of MGD. Methods: Meibum samples were collected from 3 cohorts of adults with no MGD, mild-to-moderate MGD, and severe MGD in a noninterventional clinical trial (NCT01979887). OAHFAs, cholesterol esters (CE), HC unsaturation, and HC length in the meibum samples were quantified with 1H-nuclear magnetic resonance spectroscopy using 2 methods of normalization. Results: Meibum samples from 62 subjects were analyzed: 21 non-MGD, 21 mild-to-moderate MGD, and 20 severe MGD. Meibum OAHFA and CE levels and HC unsaturation were reduced with increasing severity of MGD, with most pairwise comparisons significant (P < 0.05, t-tests), following the order non-MGD > mild-to-moderate MGD > severe MGD. Regardless of the resonances used for normalization, each pairwise comparison of OAHFA, CE, and HC unsaturation levels in MGD (combined severities) versus non-MGD samples was significant (P < 0.01, t-test). Analysis using various normalization equations showed reductions of 20%-22% for OAHFAs, 51%-57% for CE, and 36%-66% for HC unsaturation in MGD (combined severities) compared with non-MGD. HC length was not altered in MGD (combined severities) compared with non-MGD samples (t-test). Conclusions: Meibum OAHFA, CE, and HC unsaturation levels were reduced in MGD and were lowest in the severe MGD cohort. These findings may contribute to the understanding of the pathophysiology of MGD.
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Affiliation(s)
- Ashley Nguyen
- Allergan, an AbbVie company, Irvine, California, USA
| | - Kugen K Naidoo
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, USA
| | - Layla Ajouz
- Allergan, an AbbVie company, Irvine, California, USA
| | - Xiaoming Xu
- Allergan, an AbbVie company, Irvine, California, USA
| | - Cathy Zhao
- Allergan, an AbbVie company, Irvine, California, USA
| | | | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, USA
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Nagar S, Ajouz L, Nichols KK, Kumar S, Zhao C, Naidoo KK, Robinson MR, Borchman D. Relationship Between Human Meibum Lipid Composition and the Severity of Meibomian Gland Dysfunction: A Spectroscopic Analysis. Invest Ophthalmol Vis Sci 2023; 64:22. [PMID: 37466951 PMCID: PMC10362926 DOI: 10.1167/iovs.64.10.22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023] Open
Abstract
Purpose Information on the relationship between meibum lipid composition and severity of meibomian gland dysfunction (MGD) is limited. The purpose of this study was to analyze the molecular components of meibum collected from individuals with no MGD, mild-to-moderate MGD, and severe MGD. Methods Adults with and without MGD were enrolled in a prospective, multicenter, exploratory clinical trial (ClinicalTrials.gov Identifier: NCT01979887). Molar ratios of cholesteryl ester to wax ester (RCE/WE) and aldehyde to wax ester (Rald/WE) in meibum samples were measured with 1H-NMR spectroscopy. Results were evaluated for participants grouped by MGD disease status and severity (non-MGD, mild-to-moderate MGD, and severe MGD), as defined by maximum meibum quality scores, Schirmer test results, and Subject Ocular Symptom Questionnaire responses. Results Sixty-nine meibum samples from 69 individuals were included in the analysis: 24 non-MGD, 24 mild-to-moderate MGD, and 21 severe MGD. Mean RCE/WE was 0.29 in non-MGD, 0.14 in mild-to-moderate MGD (P = 0.038 vs. non-MGD, 51% lower), and 0.07 in severe MGD (P = 0.16 vs. mild-to-moderate MGD, 52% lower; P = 0.002 vs. non-MGD, 76% lower). Mean Rald/WE was 0.00022 in non-MGD, 0.00083 in mild-to-moderate MGD (P = 0.07 vs. non-MGD, 277% higher), and 0.0024 in severe MGD (P = 0.003 vs. mild-to-moderate MGD, 190% higher; P < 0.001 vs. non-MGD, 992% higher). Conclusions RCE/WE was lowest and Rald/WE was highest in the severe MGD cohort, suggesting that these meibum constituent molar ratios may result from the pathophysiology associated with MGD and can impact ocular surface lipid and tear film homeostasis. These findings may potentially help identify targets for MGD treatment.
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Affiliation(s)
- Saumya Nagar
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Layla Ajouz
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Kelly K Nichols
- School of Optometry, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Sandeep Kumar
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Cathy Zhao
- Allergan, an AbbVie company, Irvine, CA, United States
| | - Kugen K Naidoo
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, United States
| | | | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, United States
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Zhang C, Ma Y, Zhang J, Kuo JCT, Zhang Z, Xie H, Zhu J, Liu T. Modification of Lipid-Based Nanoparticles: An Efficient Delivery System for Nucleic Acid-Based Immunotherapy. Molecules 2022; 27:molecules27061943. [PMID: 35335310 PMCID: PMC8949521 DOI: 10.3390/molecules27061943] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 03/07/2022] [Accepted: 03/07/2022] [Indexed: 02/05/2023] Open
Abstract
Lipid-based nanoparticles (LBNPs) are biocompatible and biodegradable vesicles that are considered to be one of the most efficient drug delivery platforms. Due to the prominent advantages, such as long circulation time, slow drug release, reduced toxicity, high transfection efficiency, and endosomal escape capacity, such synthetic nanoparticles have been widely used for carrying genetic therapeutics, particularly nucleic acids that can be applied in the treatment for various diseases, including congenital diseases, cancers, virus infections, and chronic inflammations. Despite great merits and multiple successful applications, many extracellular and intracellular barriers remain and greatly impair delivery efficacy and therapeutic outcomes. As such, the current state of knowledge and pitfalls regarding the gene delivery and construction of LBNPs will be initially summarized. In order to develop a new generation of LBNPs for improved delivery profiles and therapeutic effects, the modification strategies of LBNPs will be reviewed. On the basis of these developed modifications, the performance of LBNPs as therapeutic nanoplatforms have been greatly improved and extensively applied in immunotherapies, including infectious diseases and cancers. However, the therapeutic applications of LBNPs systems are still limited due to the undesirable endosomal escape, potential aggregation, and the inefficient encapsulation of therapeutics. Herein, we will review and discuss recent advances and remaining challenges in the development of LBNPs for nucleic acid-based immunotherapy.
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Affiliation(s)
- Chi Zhang
- College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA; (C.Z.); (J.C.-T.K.); (Z.Z.)
| | - Yifan Ma
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH 43210, USA; (Y.M.); (J.Z.)
| | - Jingjing Zhang
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH 43210, USA; (Y.M.); (J.Z.)
| | - Jimmy Chun-Tien Kuo
- College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA; (C.Z.); (J.C.-T.K.); (Z.Z.)
| | - Zhongkun Zhang
- College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA; (C.Z.); (J.C.-T.K.); (Z.Z.)
| | - Haotian Xie
- Department of Statistics, The Ohio State University, Columbus, OH 43210, USA;
| | - Jing Zhu
- College of Nursing and Health Innovation, The University of Texas Arlington, Arlington, TX 76010, USA
- Correspondence: (J.Z.); (T.L.); Tel.: +1-614-570-1164 (J.Z.); +86-186-6501-3854 (T.L.)
| | - Tongzheng Liu
- College of Pharmacy, Jinan University, Guangzhou 511443, China
- Correspondence: (J.Z.); (T.L.); Tel.: +1-614-570-1164 (J.Z.); +86-186-6501-3854 (T.L.)
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Eftimov P, Ewurum A, Ankem A, Borchman D, Georgiev GA. Correlations between bulk and surface properties of meibomian lipids with alteration of wax-to-sterol esters content. Chem Phys Lipids 2021; 242:105163. [PMID: 34864017 DOI: 10.1016/j.chemphyslip.2021.105163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/29/2021] [Accepted: 11/30/2021] [Indexed: 11/03/2022]
Abstract
In a recent study (Ewurum et al., 2021), wax (WE) and sterol esters (CE) from human meibum secretions (MGS) were separated and reconstituted with controlled WE/CE ratios (0%, 20%, 30%, 40%, 50%, 75% and 100% CE weight fractions). It was found that the alterations in the CE content of WE/CE mixtures modified the hydrocarbon chain conformation and packing of the mixture. A major question that emerges is whether the spectroscopic packing parameters determined for bulk meibum translate to a change in the performance of meibomian layers at the air/water interface, as it is the surface film functionality that is crucial for the performance of MGS at the ocular surface. The study of human meibum films with Langmuir surface balance was performed to access the surface properties at blink-like deformations of the film area. Surface pressure (π)-area (A) isocycles and stress relaxations were used to assess the layer's reorganization during area cycling and dilatational elasticity, respectively. The morphology of the films was monitored by Brewster angle microscopy. It was found that the increased order and chain melting temperature of the bulk samples correlated with a raise in the maximum surface pressure attained at minimal surface area and in the transient dilatational modulus of the meibomian layers. Such correlations may allow for development of an improved understanding between the bulk and surface properties of human meibum and of other natural and synthetic tear lipid films.
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Affiliation(s)
- Petar Eftimov
- Department of Cytology, Histology and Embryology, Faculty of Biology, St. Kliment Ohridski University of Sofia, Bulgaria
| | - Anthony Ewurum
- Department of Chemistry, University of Louisville, Louisville, KY, USA
| | - Akhila Ankem
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, USA
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, USA
| | - Georgi As Georgiev
- iBB - Institute for Bioengineering and Biosciences, Interdisciplinary Complex, IST, University of Lisbon, 1649-004 Lisbon, Portugal.
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Phan MAT, Madigan MC, Stapleton F, Willcox M, Golebiowski B. Human meibomian gland epithelial cell culture models: Current progress, challenges, and future directions. Ocul Surf 2021; 23:96-113. [PMID: 34843998 DOI: 10.1016/j.jtos.2021.11.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 11/04/2021] [Accepted: 11/23/2021] [Indexed: 12/13/2022]
Abstract
The widely used immortalised human meibomian gland epithelia cell (iHMGEC) line has made possible extensive studies of the biology and pathophysiology of meibomian glands (MG). Tissue culture protocols for iHMGEC have been revised and modified to optimise the growth conditions for cell differentiation and lipid accumulation. iHMGEC proliferate in serum-free medium but require serum or other appropriate exogenous factors to differentiate. Several supplements can enhance differentiation and neutral lipid accumulation in iHMGEC grown in serum-containing medium. In serum-free medium, rosiglitazone, a peroxisome proliferator activator receptor-γ (PPARγ) agonist, is reported to induce iHMGEC differentiation, neutral lipid accumulation and expression of key biomarkers of differentiation. iHMGEC cultured in serum-containing medium under hypoxia or with azithromycin increases DNAse 2 activity, a biomarker of terminal differentiation in sebocytes. The production of lipids with composition similar to meibum has not been observed in vitro and this remains a major challenge for iHMGEC culture. Innovative methodologies such as 3D ex vivo culture of MG and generation of MG organoids from stem cells are important for further developing a model that more closely mimics the in vivo biology of human MG and to facilitate the next generation of studies of MG disease and dry eye.
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Affiliation(s)
- Minh Anh Thu Phan
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia.
| | - Michele C Madigan
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
| | - Fiona Stapleton
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
| | - Mark Willcox
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
| | - Blanka Golebiowski
- School of Optometry and Vision Science, Faculty of Medicine and Health, UNSW Sydney, NSW, 2033, Australia
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Khanal S, Bai Y, Ngo W, Nichols KK, Wilson L, Barnes S, Nichols JJ. Human Meibum and Tear Film Derived (O-Acyl)-Omega-Hydroxy Fatty Acids as Biomarkers of Tear Film Dynamics in Meibomian Gland Dysfunction and Dry Eye Disease. Invest Ophthalmol Vis Sci 2021; 62:13. [PMID: 34236383 PMCID: PMC8267210 DOI: 10.1167/iovs.62.9.13] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To investigate the association between precorneal tear film (PCTF)- and meibum-derived (O-Acyl)-omega-hydroxy fatty acids (OAHFAs) and PCTF thinning in meibomian gland health and dysfunction. Methods Of 195 eligible subjects (18-84 years, 62.6% female), 178 and 170 subjects provided both PCTF optical coherence tomography (OCT) imaging and mass spectrometry data for tears (n = 178) and meibum (n = 170). The PCTF thinning rate was measured in the right eye using an ultra-high-resolution, custom-built OCT. Tear and meibum samples from the right eye were infused into the SCIEX 5600 TripleTOF mass spectrometer in the negative ion mode. Intensities (m/z) of preidentified OAHFAs were measured with Analyst 1.7TF and LipidView 1.3 (SCIEX). Principal component (PC) analyses and Spearman's correlations (ρ) were performed to evaluate the association between OAHFAs and PCTF thinning rates. Results In meibum and tear samples, 76 and 78 unique OAHFAs were detected, respectively. The first PC scores of the meibum-derived OAHFAs had statistically significant correlations with PCTF thinning rates (ρ = 0.18, P = 0.016). Among 10 OAHFAs with the highest first PC loadings, six OAHFAs had negative correlations with PCTF thinning rate (18:2/16:2, ρ = -0.19, P = 0.01; 18:2/30:1, ρ = -0.21, P = 0.008; 18:1/28:1, ρ = -0.22, P = 0.004; 18:1/30:1, ρ = -0.22, P = 0.005; 18:1/25:0, ρ = 0.22, P = 0 .006; and 18:1/26:1, ρ = -0.22, P = 0.006), while one OAHFA had a positive correlation with PCTF thinning rate (18:2/18:1, ρ = 0.48, P = 0.006). Tear film-derived OAHFAs had no association with the PCTF thinning rate. Conclusions Several human meibum-derived OAHFAs showed significant associations with PCTF thinning, suggesting that these OAHFAs could be implicated in the mechanism underlying the stabilization and thinning of the PCTF. The tear-film derived OAHFAs were, however, independent of the rate of PCTF thinning.
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Affiliation(s)
- Safal Khanal
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Yuqiang Bai
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - William Ngo
- Centre for Ocular Research & Education, School of Optometry & Vision Science, University of Waterloo, Waterloo, Ontario, Canada.,Centre for Eye and Vision Research, 17W Hong Kong Science Park, Hong Kong
| | - Kelly K Nichols
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Landon Wilson
- Department of Pharmacology and Toxicology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.,Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Stephen Barnes
- Department of Pharmacology and Toxicology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.,Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Jason J Nichols
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
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Ewurum A, Ankem A, Georgiev G, Borchman D. A spectroscopic study of the composition and conformation of cholesteryl and wax esters purified from meibum. Chem Phys Lipids 2021; 238:105088. [PMID: 33965419 DOI: 10.1016/j.chemphyslip.2021.105088] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/20/2021] [Accepted: 05/02/2021] [Indexed: 10/21/2022]
Abstract
Elucidating wax ester (WE) and cholesteryl ester (CE) compositional, structural and functional relationships is key to our understanding of how these lipids are involved in natural and pathological processes. Little is known about how CE and WE interact with one another. The focus of the present study is to bridge this gap of knowledge. CE and WE were collected from human meibum as a source of esters with complex hydrocarbon chains. MgO column chromatography was used to separate WE and CE. The esters were characterized using 1H-NMR and Fourier transform infrared spectroscopy. The complexity of the hydrocarbon chains of native WE and CE influenced how changes in the ratio of WE and CE ester influenced some lipid phase transitional parameters but not others. Changes in CE content of WE/CE mixtures undoubtedly modifies the hydrocarbon chain conformation and packing of the mixture. The nature of the change depends on the conformation of the WE and CE. Differences in the complexity of the hydrocarbon chains are likely not to be a major influence on alterations in the order or phase transition temperature when more ordered WE is added to less ordered CE.
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Affiliation(s)
- Anthony Ewurum
- Department of Chemistry, University of Louisville, Louisville, KY, USA
| | - Akhila Ankem
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, USA
| | - Georgi Georgiev
- iBB - Institute for Bioengineering and Biosciences, Interdisciplinary Complex, IST, University of Lisbon, 1649-004, Lisbon, Portugal
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, USA.
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Borchman D. Lipid conformational order and the etiology of cataract and dry eye. J Lipid Res 2021; 62:100039. [PMID: 32554545 PMCID: PMC7910524 DOI: 10.1194/jlr.tr120000874] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/15/2020] [Indexed: 12/12/2022] Open
Abstract
Lens and tear film lipids are as unique as the systems they reside in. The major lipid of the human lens is dihydrosphingomylein, found in quantity only in the lens. The lens contains a cholesterol to phospholipid molar ratio as high as 10:1, more than anywhere else in the body. Lens lipids contribute to maintaining lens clarity, and alterations in lens lipid composition due to age are likely to contribute to cataract. Lens lipid composition reflects adaptations to the unique characteristics of the lens: no turnover of lens lipids or proteins; the lowest amount of oxygen of any tissue; and contains almost no intracellular organelles. The tear film lipid layer (TFLL) is also unique. The TFLL is a thin (100 nm) layer of lipid on the surface of tears covering the cornea that contributes to tear film stability. The major lipids of the TFLL are wax esters and cholesterol esters that are not found in the lens. The hydrocarbon chains associated with the esters are longer than those found anywhere else in the body (as long as 32 carbons), and many are branched. Changes in the composition and structure of the 30,000 different moieties of TFLL contribute to the instability of tears. The focus of the current review is how spectroscopy has been used to elucidate the relationships between lipid composition, conformational order and function, and the etiology of cataract and dry eye.
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Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202.
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Ramasubramanian A, Ahmed SF, Borchman D. Changes in meibum composition following plaque bachytherapy for choroidal melanoma. BMJ Open Ophthalmol 2020; 5:e000614. [PMID: 33294624 PMCID: PMC7689590 DOI: 10.1136/bmjophth-2020-000614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/27/2020] [Accepted: 11/12/2020] [Indexed: 11/03/2022] Open
Abstract
Objectives Dry eye is common when external beam radiation is used for the treatment of choroidal melanoma (CM). As meibum structure and composition have been related to dry eye, we determined if plaque bachytherapy for CM alters meibum composition. Design 1H-NMR spectroscopy was used to measure the lipid composition of meibum. Setting The University of Louisville, Kentucky, USA. Participants All 13 participants had CM and one participant had iris melanoma. Main outcome measures Cholesteryl ester (CE) to wax ester (WE) ratio, amount of meibum esters (ME) and meibum lipid saturation were measured. Results ME decreased by 80%±18% (±99% CI) in 11 eyes that were treated compared with the contralateral untreated eye. ME increased by 181% in two eyes that were treated compared with the contralateral untreated eye. The mole % CE/WE for meibum was significantly (p<0.0001) 67% lower in eyes that were irradiated compared with control eyes from donors without CM and were not treated. Plaque brachytherapy induced the de-esterification of CE. The intensity of the meibum cis double bond resonances did not change significantly (p>0.05). Conclusion Eyes that had plaque brachytherapy had a lower amount of expressible meibum and a lower CE/WE ratio compared with meibum from the contralateral eye that received no treatment and eyes that did not have uveal melanoma. Both the quality and quantity of meibum should be considered in designing a therapy for dry eye after plaque brachytherapy.
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Affiliation(s)
| | - Simra Fatima Ahmed
- Department of Ophthtalmology, University of Louisville School of Medicine, Louisville, Kentucky, USA
| | - Douglas Borchman
- Department of Ophthtalmology, University of Louisville School of Medicine, Louisville, Kentucky, USA
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Meibum lipid hydrocarbon chain branching and rheology after hematopoietic stem cell transplantation. Biochem Biophys Rep 2020; 23:100786. [PMID: 32715105 PMCID: PMC7374597 DOI: 10.1016/j.bbrep.2020.100786] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 06/22/2020] [Accepted: 06/23/2020] [Indexed: 12/16/2022] Open
Abstract
Purpose Meibum from donors who have had hematological stem cell transplantations (MHSCT) are susceptible to severe dry eye symptoms and exhibit very high lipid order (stiffness) compared with meibum from donors without dry eye (Mn). Since lipid order could have functional consequences, we compared the rheology and composition of Mn and MHSCT to measure meibum compositional, structural and functional relationships. Methods The rheology and composition was measured using Langmuir trough and 1H NMR spectroscopy, respectively. Results MHSCT and Mn was studied from 16 to 43 donors, respectively, using NMR spectroscopy. MHSCT contained significantly 16% more straight chain and 24% less iso-chain hydrocarbons compared with Mn. The cholesteryl ester to wax ester molar ratio, and hydrocarbon chain unsaturation were not significantly different, for MHSCT compared with Mn. Surface pressure-area isotherms of meibum from 30 donors without dry-eye were grouped into 4 pools (PC) and meibum from 32 donors with dry eye who had hematopoietic stem cell transplantation (PT) were grouped into 3 pools. Above 15 years of age the Пmax and (Cs−1)max increased with age for both the PC and the PT cohorts. (Cs−1)max values were higher for PT samples compared with age matched PC samples, indicating they had higher elasticity and stiffness. A more ordered lipid could contribute to the formation of a discontinuous patchy tear film lipid layer, which in turn results in deteriorated spreading, and decreased surface elasticity. Conclusions The composition and rheology of meibum from donors with dry eye and who have had HSCT support the idea from other studies that more ordered meibum may contribute to or be a marker of dry eye. More straight chain and less iso-chain hydrocarbons could contribute to HSCT dry eye. Meibum elasticity and stiffness increased with age. Meibum elasticity and stiffness increased with HSCT dry eye. Differences could contribute to a discontinuous patchy tear film lipid layer. Differences could result in deteriorated spreading, and decreased surface elasticity.
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Mixed polar-nonpolar lipid films as minimalistic models of Tear Film Lipid Layer: A Langmuir trough and fluorescence microscopy study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183300. [PMID: 32243884 DOI: 10.1016/j.bbamem.2020.183300] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 03/11/2020] [Accepted: 03/29/2020] [Indexed: 12/11/2022]
Abstract
The Tear Film Lipid Layer (TFLL) covering the surface of the aqueous film at human cornea forms a first barrier between the eye and environment. Its alterations are related to dry eye disease. TFLL is formed by a complex mixture of lipids, with an excess of nonpolar components and a minor fraction of polar molecules. Its thickness is up to 160 nm, hence a multilayer-like structure of TFLL is assumed. However, details of TFLL organization are mostly unavailable in vivo due to the dynamic nature of the human tear film. To overcome this issue, we employ a minimalistic in vitro lipid model of TFLL. We study its biophysical characteristics by using a combination of the Langmuir trough with fluorescence microscopy. The model consists of two-component polar-nonpolar lipid films with a varying component ratio spread on the aqueous subphase at physiologically relevant temperature. We demonstrate that the model lipid mixture undergoes substantial structural reorganization as a function of lateral pressure and polar to nonpolar lipid ratio. In particular, the film is one-molecule-thick and homogenous under low lateral pressure. Upon compression, it transforms into a multilayer structure with inhomogeneities in the form of polar-nonpolar lipid assemblies. Based on this model, we hypothesize that TFLL in vivo has a duplex polar-nonpolar structure and it contains numerous mixed lipid aggregates formed because of film restructuring. These findings, despite the simplified character of the model, seem relevant for TFLL physiology as well as for understanding pathological conditions related to the lipids of the tear film.
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Hetman ZA, Borchman D. Concentration dependent cholesteryl-ester and wax-ester structural relationships and meibomian gland dysfunction. Biochem Biophys Rep 2020; 21:100732. [PMID: 32042930 PMCID: PMC7000810 DOI: 10.1016/j.bbrep.2020.100732] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 01/13/2020] [Accepted: 01/14/2020] [Indexed: 01/08/2023] Open
Abstract
Background With dry eye, the ratio of cholesteryl ester (CE) to wax ester (WE) decreases substantially in meibum, but the functional and structural consequences of this change are speculative. The aim of this study is to confirm this finding and to bridge this gap in knowledge by investigating the effect of varying CE/WE ratios on lipid structure and thermodynamics. Methods Infrared spectroscopy was use to quantify CE and WE in human meibum and to measure hydrocarbon chain conformation and thermodynamics in a cholesteryl behenate, stearyl stearate model system. Results The CE/WE molar ratio was 36% lower for meibum from donors with dry eye due to meibomian gland dysfunction compared with meibum from donors without dry eye. CE (5 mol %) dramatically increased the phase transition temperature of pure WE from -0.12 °C to 63 °C in the mixture. Above 5 mol % CB, the phase transition temperature increased linearly, from 68.5 °C to 85 °C. In the ordered state, CE caused an increase in lipid order from about 72% trans rotamers to about 86% trans rotamers. Above 10% CE, the hydrocarbon chains were arranged in a monoclinic geometry. Conclusions The CE/WE is lower in meibum from donors with dry eye due to meibomian-gland dysfunction. Major conformational changes in the hydrocarbon chains of wax and cholesteryl ester mixtures begin to occur with just 5% CB and above. General significance CE-WE interactions may be important for in understanding lipid layer structure and functional relationships on the surface of tears, skin and plants. The CE/WE is lower in meibum from donors with meibomian-gland dysfunction. CE may be important for the tear film lipid layer structure and function. CE-WE interactions may be important on the surface of tears, skin and plants. Conformational changes in WE and CE mixtures begin to occur with just 5% CE. CE, cholesteryl ester; WE, wax ester.
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Affiliation(s)
| | - Douglas Borchman
- Corresponding author. The Kentucky Lions Eye Center, University of Louisville, 301 E. Muhammad Ali Blvd, Louisville, KY, 40202.
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Borchman D, Ramakrishnan V, Henry C, Ramasubramanian A. Differences in Meibum and Tear Lipid Composition and Conformation. Cornea 2020; 39:122-128. [PMID: 31369460 PMCID: PMC8454188 DOI: 10.1097/ico.0000000000002095] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PURPOSE The compositional, structural, and functional relationships of meibum may provide insights into the loss of tear film stability. Although the conformation of meibum lipids has been studied rigorously, that of tear lipids has not. METHODS Tear lipids (TLHSCT) and meibum (MHSCT) from patients who had hematopoietic stem cell transplantation were pooled prospectively. The infrared spectra of meibum from donors with (MMGD) and without (Mn) meibomian gland dysfunction were retrospectively analyzed to measure the lipid composition and structure. The infrared CH stretching region was used to measure the relative content of CH3 and CH2 moieties in the meibum. RESULTS The 3 major findings of the current study are as follows: 1) compared with Mn, MHSCT and MMGD had 18% fewer CH3 moieties; 2) compared with MHSCT, the phase transition temperature, cooperativity, and order were approximately 20% greater for TLHSCT; and 3) compared with Mn and MMGD, MHSCT and TLHSCT contained fewer double bonds. CONCLUSIONS Tear lipids are more ordered than meibum lipids, which could have functional consequences. The human meibum peak height ratio of the CH3/CH2 bands is not a factor related to tear film stability with age or sex. The amount of CH3 moieties relative to CH2 moieties and saturation could contribute to a higher meibum lipid order associated with a younger age, meibomian gland dysfunction, and dry eye from hematopoietic stem cell transplantation. Therefore, the hydrocarbon order may be a marker of or contribute to an unstable tear film layer.
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Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY
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Tear Film Instability and Meibomian Gland Dysfunction Correlate with the Pterygium Size and Thickness Pre- and Postexcision in Patients with Pterygium. J Ophthalmol 2019; 2019:5935239. [PMID: 31885889 PMCID: PMC6914971 DOI: 10.1155/2019/5935239] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 11/02/2019] [Indexed: 01/04/2023] Open
Abstract
Purpose This study aimed to evaluate the effects of excision on dry eye and meibomian gland dysfunction (MGD) in individuals with pterygium, before and after surgery. It also aimed to investigate how these effects correlate with the size and thickness of the pterygium. Subjects and Methods 63 eyes from 63 patients with primary nasal pterygium and 45 eyes from 45 healthy volunteers without ocular pathologies were enrolled in this study. 63 eyes from 63 patients underwent pterygium surgery. ImageJ software was used to calculate the pterygium size based on images of the anterior segments. Anterior segment spectral domain optical coherence tomography (SD-OCT) was performed preoperatively to measure the thickness of the pterygium 1 mm anterior to the nasal scleral spur. The ocular surface disease index (OSDI), Schirmer I Test (SIT), and MGD grade were used to evaluate the eyes, and the eyes were imaged using the noninvasive keratograph average tear film breakup time (NIBUTav), tear meniscus height (TMH), meiboscore, and lipid layer grading tools of the Oculus® Keratograph 5M, preoperatively and at 1, 3, and 6 months postoperatively. Results The OSDI, NIBUTav, lid margin abnormality, meiboscore, and lipid layer grading values differed significantly in the pterygium patients in comparison with the controls (p < 0.01 for all scores). However, the SIT and TMH values were unchanged between the two groups (all p > 0.05). Multivariate regression analysis demonstrated that the NIBUTav, meiboscore, and lipid layer grading score was significantly correlated with the pterygium parameters, such as size and thickness. The postoperative OSDI, NIBUTav, lid margin abnormality, and lipid layer grading values improved significantly (p < 0.05 for all scores). The SIT, TMH, and meiboscore results did not differ significantly between the pre- and postoperative values (p > 0.05). Among the conventional and automated indexes, at 1 month postoperatively, SIT and TMH were significantly correlated with the pterygium parameters, but no correlation was observed at 3 and 6 months postoperatively. The OSDI, NIBUTav, meiboscore, and lipid layer grading values at 1, 3, and 6 months postoperatively were significantly correlated with the pterygium parameters. Conclusion Abnormal tear film and meibomian gland (MG) function improved following pterygium excision in the patients with primary pterygium, which was associated with uncomfortable ocular symptoms. Pterygium parameters, such as size and thickness, correlated with the dry eye and MGD indexes in patients pre- and postoperatively, potentially offering a novel strategy for clinical implementation of pterygium excision surgery.
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Borchman D, Ramasubramanian A, Foulks GN. Human Meibum Cholesteryl and Wax Ester Variability With Age, Sex, and Meibomian Gland Dysfunction. Invest Ophthalmol Vis Sci 2019; 60:2286-2293. [PMID: 31112994 PMCID: PMC6530518 DOI: 10.1167/iovs.19-26812] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Purpose Relationships between tear film lipid (TFL) layer composition, structure, and function could provide insight into the etiology of dry eye. The molar ratio of cholesteryl ester (CE)/wax ester (WE) was measured in meibum from normal donors (Mn) and compared with meibum from donors with meibomian gland dysfunction (MMGD). Methods CE/WE was measured using nuclear magnetic resonance spectroscopy. Results CE/WE was distributed into two populations with 81% distributed near 0.55 and 19% near 0.3. CE/WE were higher in donors 13 to 19 years old compared with donors 1 to 12 years old and 20 to 88 years old. CE/WE for MMGD was 30% lower, 0.34 ± 0.04, compared with Mn, 0.49 ± 0.04. There were no sex differences in CE/WE. There were no significant racial differences between the CE/WE ratios for Asians and Caucasians. The CE/WE ratio was higher for blacks and lower for Hispanics compared to Caucasians. Due to the small number sampled, confirmation of the later racial results is needed. The packing of CE and WE in the TFL layer was proposed. Conclusions Although MMGD contains much less CE than Mn, factors other than the CE content, such as the levels of saturation and/or proteins, may be responsible for the higher order of MMGD. In addition to saturation, CE could contribute to the increase in order of Mn between 0 and 20 years of age. Observed changes in the meibum content of CE alone is not likely to influence tear film stability.
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Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Aparna Ramasubramanian
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Gary N Foulks
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
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Mudgil P. Evaluation of use of essential fatty acids in topical ophthalmic preparations for dry eye. Ocul Surf 2019; 18:74-79. [PMID: 31589924 DOI: 10.1016/j.jtos.2019.10.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Revised: 09/20/2019] [Accepted: 10/03/2019] [Indexed: 01/31/2023]
Abstract
PURPOSE Essential fatty acids (EFAs) as dietary supplements are used in treating dry-eye for reducing inflammation at the ocular surface. Their topical application in eye drops to deliver fatty acid (FA) directly to the ocular surface requires thorough investigation. Being lipids in nature EFAs can interact with tear lipids and affect tear stability. This study aimed at investigating the biophysical interactions of EFAs with Meibomian lipids. METHODS Rheology of mixtures of Human Meibomian lipids with EFAs (LA-linoleic acid, ALA-alpha-linolenic acid), OA (oleic acid), and GLA (gamma-linolenic acid) was studied using Langmuir trough technology on an artificial tear solution at the ocular surface temperature. Pressure-area profiles were used to determine compressibility and elasticity of the mixed films. RESULTS LA enhanced spreading of Meibomian lipids and increased their compressibility and elasticity which can be beneficial for tear stability. ALA condensed Meibomian lipids film with less elasticity deemed unfavourable for tear stability. OA expanded Meibomian lipids but decreased elasticity at high compressions making films less stable. GLA had little or no favourable effect on tear stability. Higher concentrations of FAs made films less stable. CONCLUSIONS EFAs or OA in topical ophthalmic preparations can affect spread and stability of the tear film lipid layer. Rheology of mixed films should be tested using Langmuir trough technology to determine suitable type and amount of a lipid additive for therapeutic eye drops. In topical applications, the omega-6 LA (not omega-3 FA) at low concentrations (20 mol%) can be beneficial for enhancing tear stability in dry eye patients.
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Affiliation(s)
- Poonam Mudgil
- School of Medicine, Western Sydney University, Locked Bag 1797, Penrith, New South Wales, 2751, Australia.
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17
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Abstract
PURPOSE Meibum is considered to be a key component of tears that serve to protect the eye, and conformational changes in meibum have not been studied extensively within the population of patients who had hematopoietic stem cell transplantation (HSCT). The aim of this study was to determine possible lipid conformational changes in the meibum of patients who had HSCT. METHODS Participants who had HSCT were randomly sampled for this prospective comparative study. Control participants did not have dry eye or had not undergone allogeneic or autologous stem cell transplantation. Fourier-transform infrared spectroscopy was used to measure meibum phase transition. RESULTS Meibum was collected from both eyes of 36 donors without dry eye (Mc) and from 22 patients who had undergone HSCT (MHSCT). There were no significant differences between the phase transition parameters based on gender or race. The following were the significant differences (P < 0.0001) between the parameters for Mc compared with MHSCT : lipid order (% trans) at 33.4°C increased from 40 (1) to 54 (2), cooperativity decreased from 7.9 (0.4) to 5.4 (0.3), the phase transition temperature (C) increased from 30.3 (0.4) to 34.2 (0.9), and the magnitude of the phase transition (cm) increased from 4.0 (0.1) to 4.7 (0.5) (standard error of the mean). CONCLUSIONS Conformational and thermodynamic differences were observed between Mc and MHSCT. The changes observed in the lipid conformation of meibum from patients receiving HSCTs suggest that meibum composition changes after stem cell transplantation, and clinicians should consider treating the meibomian glands to improve the ocular surface.
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Lipid Saturation and the Rheology of Human Tear Lipids. Int J Mol Sci 2019; 20:ijms20143431. [PMID: 31336861 PMCID: PMC6678947 DOI: 10.3390/ijms20143431] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 06/24/2019] [Accepted: 07/04/2019] [Indexed: 02/03/2023] Open
Abstract
Elevated levels of acyl chain saturation of meibomian lipids are associated with enhanced tear film (TF) stability in infants to shortened TF breakup time with meibomian gland dysfunction. Thus, the effect of saturation on the surface properties of human TF lipids (TFLs) using a Langmuir surface balance and Brewster angle microscopy was studied. Lipid phase transitions were measured using infrared spectroscopy. The raise in the % of saturation resulted in thicker, and more elastic films at π = 12 mN/m, with the effects being proportional to the saturation level. At the same time, at lower (≤10 mN/m) π, the raise in saturation resulted in an altered spreading and modified structure of TFL layers. The strong impact of saturation on TFL surface properties correlated with a saturation induced increase of the TFL acyl chain order, phase transition temperature, and lipid-lipid interactions. The native TFL order and πmax were significantly greater, compared with native meibum collected from the same individual. Aggregation of lipids on the tear surface due to saturation was not as significant as it was for meibum. Although the surface pressure/area isotherms for TFL were similar for meibum, differences in rheology and phase transition parameters warrant the study of both.
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Borchman D. The optimum temperature for the heat therapy for meibomian gland dysfunction. Ocul Surf 2019; 17:360-364. [PMID: 30794947 PMCID: PMC6529265 DOI: 10.1016/j.jtos.2019.02.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 02/06/2019] [Accepted: 02/15/2019] [Indexed: 11/23/2022]
Abstract
PURPOSE Numerous devices have been developed to warm the eyelid as a therapy for Meibomian gland dysfunction. The optimum temperature for such therapy was determined. METHODS Meibum lipid disorder versus temperature was calculated from previously published phase transition parameters measured using infrared spectroscopy. Phase transitions parameters were calculated from meibum obtained from donors with Meibomian gland dysfunction (MMGD), donors who were susceptible to dry eye after hematopoietic stem cell transplantations (MHSCT) and meibum from donors without dry eye (Mn). RESULTS Heating Mn to 40 °C increases the lipid disorder by 20.4%-90%. Heating the meibum another 4° increases the disorder to 95%. MMGD is 73.2% disordered with no heating. Heating MMGD to 41.5 °C increases the disorder by 26.8%-90% disordered. Heating MMGD another 5.1 °C increases the disorder to 95%. As MHSCT is much more ordered, 56.9% disordered compared with Mn and MMGD, a higher temperature above safety limits, 52 and 59 °C is need to disorder MHSCT to 90 and 95% disorder. CONCLUSIONS Heating the eye lid above the phase transition temperature of meibum increases the disorder of meibum lipid which could ameliorate dry eye symptoms. The optimum temperature for disordering Mn and MMGD to 90% maximum disorder is 40 and 41.5 °C, respectively. Safety issues and discomfort should be considered in obtaining an optimal level of disorder, especially for severe cases of dry eye.
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Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, 40202, USA.
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Human meibum chain branching variability with age, gender and meibomian gland dysfunction. Ocul Surf 2018; 17:327-335. [PMID: 30553000 DOI: 10.1016/j.jtos.2018.12.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 11/07/2018] [Accepted: 12/11/2018] [Indexed: 12/26/2022]
Abstract
NMR spectroscopy was used to measure hydrocarbon chain branching variability in meibum with age, gender and Meibomian gland dysfuction (MGD). A cohort of 65 meibum donors without dry eye and 31 donors with MGD was studied. Heteronuclear 2D NMR was used to confirm CH3 resonance assignments allowing us to positively identify 23 of the 27 proton resonances of cholesteryl ester and 1H resonances due to straight chain, iso-branched and anteiso-branched hydrocarbons. Meibum from donors without dry eye contained 57 ± 1% straight-chains, 23 ± 1% iso-branched chains and 20 ± 1% anteiso-branched hydrocarbon chains. Compared with meibum from donors without dry eye, meibum from donors with MGD contained less, 50 ± 2% straight-chains, more, 32 ± 2% iso-branched chains and the same amount, 18.0 ± 0.07%, of anteiso-branched hydrocarbon chains. Meibum hydrocarbon chain branching did not change with age between 22 and 68 years of age, nor was it influenced by gender. Based on previous studies, one would expect anteiso-branched chains would contribute to lowering the phase transition temperature of meibum, decrease the elasticity of the tear film lipid layer and increase the molecular area and spreading of meibum on the surface of the eye. Although we speculate that the observed differences in iso-chain branching do not influence tear film stability or rheology, the speculation has yet to be tested.
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Mudgil P, Borchman D, Ramasubramanian A. Insights into Tear Film Stability from Babies and Young Adults: A Study of Human Meibum Lipid Conformation and Rheology. Int J Mol Sci 2018; 19:ijms19113502. [PMID: 30405031 PMCID: PMC6275043 DOI: 10.3390/ijms19113502] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 10/31/2018] [Accepted: 11/02/2018] [Indexed: 11/22/2022] Open
Abstract
Babies have the most stable tears and people with dry eye have the least stable tears. Meibum may contribute to tear film stability, so in this study, the hydrocarbon chain conformation and rheology of meibum from babies was studied for the first time. Infrared spectroscopy was used to measure lipid phase transitions. Rheology was measured using Langmuir film technology. Meibum from 25 donors 1 to 13 years old was compared with meibum from 18 donors 13 to 25 years old. The phase transition temperature and lipid order (stiffness) increased with increasing age from 1 to 25 years. The increase in meibum lipid order from 1 to 25 years of age may contribute to the instability of the tear film with age and contribute to films with a higher reciprocal compressibility modulus that are not as compressible and not as viscoelastic. Changes in the lipid phase transition parameters of meibum lipid with dry eye are an exacerbation of the changes observed with age. The lower reciprocal compressibility moduli of meibum films from children and babies compared with meibum from adults reiterates higher stability in their films which spread better, resist deformation, and facilitates their ability to be quickly restored after blinking.
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Affiliation(s)
- Poonam Mudgil
- School of Medicine, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia.
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Aparna Ramasubramanian
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
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22
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Effects of Lipid Saturation on the Surface Properties of Human Meibum Films. Int J Mol Sci 2018; 19:ijms19082209. [PMID: 30060578 PMCID: PMC6121396 DOI: 10.3390/ijms19082209] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 07/23/2018] [Accepted: 07/24/2018] [Indexed: 11/28/2022] Open
Abstract
Elevated levels of acyl chain saturation of meibomian lipids are associated with vastly different effects: from enhanced tear film (TF) stability in infants to shortened TF breakup time in meibomian gland disease patients. Thus it is important to study the effect of saturation on the surface properties of human meibum (MGS). Therefore, MGS films (1, 2, 3, 4, 5, 10, 25, 50, 67, and 100% saturation) were spread at the air/water interface of a Langmuir surface balance. The layers’ capability to reorganize during dynamic area changes was accessed via the surface pressure (π)-area (A) compression isotherms and step/relaxation dilatational rheology studies. Film structure was monitored with Brewster angle microscopy. The raise in the % (at ≥10%) of saturation resulted in the formation of stiffer, thicker, and more elastic films at π ≥ 12 mN/m with the effects being proportional to the saturation level. At the same time, at low (≤10 mN/m) π the raise in saturation resulted in altered spreading and heterogeneous structure of MGS layers. The strong impact of saturation on MGS surface properties correlates with our recent spectroscopy study, which demonstrated that saturation induced increase of MGS acyl chain order, phase transition temperature, and cooperativity.
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Inaba T, Tanaka Y, Tamaki S, Ito T, Ntambi JM, Tsubota K. Compensatory increases in tear volume and mucin levels associated with meibomian gland dysfunction caused by stearoyl-CoA desaturase-1 deficiency. Sci Rep 2018; 8:3358. [PMID: 29463801 PMCID: PMC5820245 DOI: 10.1038/s41598-018-21542-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 02/06/2018] [Indexed: 12/25/2022] Open
Abstract
The stearoyl-CoA desaturase (SCD) family of enzymes catalyzes monounsaturated fatty acid synthesis by inserting a cis double bond at the Δ9 position of saturated fatty acids. Disruption of these enzymes has been reported to induce a severe dry skin phenotype. Since lipid abnormalities in the meibomian glands have been associated with dry eye, we analyzed selected eye tissues contributing to tear volume and composition in genetically SCD-1-deficient mice (SCD-1 KO), including the lacrimal glands and conjunctiva. Previous histopathological analysis had revealed atrophy and loss of meibomian glands; taken together with the increased goblet cell and MUC5AC expression in the conjunctiva reported here, these findings suggest that the tear volume and mucin levels secreted are enhanced in the absence of lipid secretion as a compensatory mechanism. The expression of lipid metabolism genes in lacrimal glands was decreased in SCD1 KO mice. Thus, these results provide new pathophysiological mechanisms to pursue with regard to meibomian gland dysfunction. In addition, lack of SCD-1 causes a compensatory increase in the tear volume and mucin levels associated with changes in expression of lipid metabolism genes. These results may be useful as a new concept for dry eye treatment strategies.
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Affiliation(s)
- Takaaki Inaba
- Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Yasuhisa Tanaka
- Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Shusaku Tamaki
- Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Tomotaka Ito
- Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - James M Ntambi
- Departments of Biochemistry and of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Kazuo Tsubota
- Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
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Georgiev GA, Eftimov P, Yokoi N. Structure-function relationship of tear film lipid layer: A contemporary perspective. Exp Eye Res 2017; 163:17-28. [PMID: 28950936 DOI: 10.1016/j.exer.2017.03.013] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 03/27/2017] [Accepted: 03/31/2017] [Indexed: 01/29/2023]
Abstract
Tear film lipid layer (TFLL) stabilizes the air/tear surface of the human eye. Meibomian gland dysfunction (MGD) resulting in quantitative and qualitative modifications of TFLL major (>93%) component, the oily secretion of meibomian lipids (MGS), is the world leading cause of dry eye syndrome (DES) with up to 86% of all DES patients showing signs of MGD. Caused by intrinsic factors (aging, ocular and general diseases) and by extrinsic everyday influences like contact lens wear and extended periods in front of a computer screen, DES (resulting in TF instability, visual disturbances and chronic ocular discomfort) is the major ophthalmic public health disease of the present time affecting the quality of life of 10-30% of the human population worldwide. Therefore there is a pressing need to summarize the present knowledge, contradictions and open questions to be resolved in the field of TFLL composition/structure/functions relationship. The following major aspects are covered by the review: (i) Do we have a reliable mimic for TFLL: MGS vs contact lens lipid extracts (CLLE) vs lipid extracts from whole tears. Does TFLL truly consist of lipids only or it is important to keep in mind the TF proteins as well?; (ii) Structural properties of TFLL and of its mimics in health and disease in vitro and in vivo. How the TFLL uniformity and thickness ensures the functionality of the lipid layer (barrier to evaporation, surface properties, TF stability etc.); (iii) What are the main functions of the TFLL? In this aspect an effort is done to emphasize that there is no single main function of TFLL but instead it simultaneously fulfills plethora of functions: suppresses the evaporation (alone or probably in cooperation with other TF constituents) of the aqueous tears; stabilizes (due to its surface properties) the air/tear surface at eye opening and during the interblink interval; and even acts as a first line of defense against bacterial invasion due to its detergency action on the bacterial membranes. An effort is done to highlight how the concept on the importance of TFLL and TF viscoelasticity transpires from old and new studies and what are its clinical implications. An attempt is made to outline the future hot directions of research into the field ranging from quest for molecules that can significantly alter TFLL properties to addressing open questions on the contribution of TFLL to the overall performance of the TF.
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Affiliation(s)
- Georgi As Georgiev
- St. Kliment Ohridski University of Sofia, Department of Optics and Spectroscopy, Faculty of Physics, 5 James Bourchier Blvd., 1164 Sofia, Bulgaria.
| | - Petar Eftimov
- Department of Cytology, Histology and Embryology, Faculty of Biology, St. Kliment Ohridski University of Sofia, Sofia, Bulgaria
| | - Norihiko Yokoi
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
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25
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Ye F, Zhou F, Xia Y, Zhu X, Wu Y, Huang Z. Evaluation of meibomian gland and tear film changes in patients with pterygium. Indian J Ophthalmol 2017; 65:233-237. [PMID: 28440253 PMCID: PMC5426129 DOI: 10.4103/ijo.ijo_743_16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Background: Recent studies have demonstrated that pterygium has a close relationship with dry eye disease. This study is to determine abnormalities in meibomian gland and tear function in patients with pterygium and to assess the relationship between the variables. Materials and Methods: Forty eyes from forty patients with primary nasal pterygium and forty eyes from forty volunteers without ocular pathologies were enrolled in this study. Ocular surface disease index scores, meibomian gland expression scores, lid margin abnormality scores, meiboscore, tear film breakup time (BUT), Schirmer test (SIT) value, and the lower tear meniscus height (TMH), tear meniscus depth (TMD), and tear meniscus area (TMA) using Fourier domain optical coherence were performed. Analysis of variance was applied for intergroup comparisons. A statistical significance level of P < 0.05 was considered. Results: Ocular symptom scores, BUT scores, lid margin abnormality, meibomian gland expression, and meiboscore were significantly higher in pterygium patients than in controls (P < 0.01 for all scores). However, the SIT scores, the lower TMH, TMD, and TMA values did not revealed a significant difference between two groups (all P > 0.05). Multivariate regression analysis demonstrated that meiboscore significantly correlated with ocular symptom scores, BUT, lid margin abnormality scores, and meibomian gland expression scores. Conclusions: Meibomian gland function may be altered in pterygium patients, which is associated with uncomfortable ocular symptoms. Being aware of meibomian gland changes seems essential to understand the complex relationship among pterygium, tear film functions, and ocular surface changes.
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Affiliation(s)
- Fen Ye
- Department of Ophthalmology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, China
| | - Fen Zhou
- Eye Hospital, Nanjing Medical University, Nanjing, China
| | - Yuan Xia
- Department of Ophthalmology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, China
| | - Xiaomin Zhu
- Department of Ophthalmology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, China
| | - Yan Wu
- Department of Ophthalmology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, China
| | - Zhenping Huang
- Department of Ophthalmology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, China
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Sledge S, Henry C, Borchman D, Yappert MC, Bhola R, Ramasubramanian A, Blackburn R, Austin J, Massey K, Sayied S, Williams A, Georgiev G, Schikler KN. Human Meibum Age, Lipid-Lipid Interactions and Lipid Saturation in Meibum from Infants. Int J Mol Sci 2017; 18:ijms18091862. [PMID: 28846660 PMCID: PMC5618511 DOI: 10.3390/ijms18091862] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/25/2017] [Accepted: 08/17/2017] [Indexed: 01/21/2023] Open
Abstract
Tear stability decreases with increasing age and the same signs of instability are exacerbated with dry eye. Meibum lipid compositional changes with age provide insights into the biomolecules responsible for tear film instability. Meibum was collected from 69 normal donors ranging in age from 0.6 to 68 years of age. Infrared spectroscopy was used to measure meibum lipid phase transition parameters. Nuclear magnetic resonance spectroscopy was used to measure lipid saturation. Increasing human meibum lipid hydrocarbon chain unsaturation with age was related to a decrease in hydrocarbon chain order, cooperativity, and in the phase transition temperature. The change in these parameters was most dramatic between 1 and 20 years of age. Meibum was catalytically saturated to determine the effect of saturation on meibum lipid phase transition parameters. Hydrocarbon chain saturation was directly related to lipid order, phase transition temperature, cooperativity, changes in enthalpy and entropy, and could account for the changes in the lipid phase transition parameters observed with age. Unsaturation could contribute to decreased tear film stability with age.
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Affiliation(s)
- Samiyyah Sledge
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Collin Henry
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Marta C Yappert
- Department of Chemistry, University of Louisville, Louisville, KY 40292, USA.
| | - Rahul Bhola
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
- Division of Ophthalmology, Children's Hospital of Orange County, Orange, CA 92868, USA.
| | - Aparna Ramasubramanian
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Ryan Blackburn
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Jonathan Austin
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Kayla Massey
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Shanzeh Sayied
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Aliza Williams
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
| | - Georgi Georgiev
- Model Membranes Lab, Department of Biochemistry, Faculty of Biology, St. Kliment Ohridski University of Sofia, Sofia 1164, Bulgaria.
| | - Kenneth N Schikler
- Department of Pediatrics, University of Louisville, Louisville, KY 40202, USA.
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Mudgil P, Borchman D, Gerlach D, Yappert MC. Sebum/Meibum Surface Film Interactions and Phase Transitional Differences. Invest Ophthalmol Vis Sci 2017; 57:2401-11. [PMID: 27145473 PMCID: PMC5113983 DOI: 10.1167/iovs.16-19117] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Purpose Sebum may contribute to the composition of the tear film lipid layer naturally or as a contaminant artifact from collection. The aims of this study were to determine: if sebum changes the rheology of meibum surface films; if the resonance near 5.2 ppm in the 1H-NMR spectra of sebum is due to squalene (SQ); and if sebum or SQ, a major component of sebum, interacts with human meibum. Methods Human meibum was collected from the lid margin with a platinum spatula. Human sebum was collected using lipid absorbent tape. Langmuir trough technology was used to measure the rheology of surface films. Infrared spectroscopy was used to measure lipid conformation and phase transitions. We used 1H-NMR to measure composition and confirm the primary structure of SQ. Results The NMR resonance near 5.2 ppm in the spectra of human sebum was from SQ which composed 28 mole percent of sebum. Both sebum and SQ lowered the lipid order of meibum. Sebum expanded meibum films at lower concentrations and condensed meibum films at higher concentrations. Sebum caused meibum to be more stable at higher pressures (greater maximum surface pressure). Conclusions Physiological levels of sebum would be expected to expand or fluidize meibum making it spread better and be more surface active (qualities beneficial for tear film stability). Sebum would also be expected to stabilize the tear film lipid layer, which may allow it to withstand the high shear pressure of a blink.
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Affiliation(s)
- Poonam Mudgil
- School of Medicine Western Sydney University, Penrith, New South Wales, Australia
| | - Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Dylan Gerlach
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
| | - Marta C Yappert
- Department of Chemistry, University of Louisville, Louisville, Kentucky, United States
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Wolkoff P. External eye symptoms in indoor environments. INDOOR AIR 2017; 27:246-260. [PMID: 27444579 DOI: 10.1111/ina.12322] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/19/2016] [Indexed: 05/22/2023]
Abstract
Eye irritation, for example dry or irritated eyes, is generally among top three reported symptoms in office-like environments, in particular among workplaces with cognitive demanding visual display unit (VDU) work. The symptoms are especially among middle and advanced ages and particularly among women more than men. The symptoms are also among the most commonly reported complaints in the eye clinic. To be in a position to interpret the high prevalence of eye symptoms, a multidisciplinary and integrated approach is necessary that involves the external eye physiology (separate from internal eye effects), eye diseases (evaporative dry eye (DE), aqueous-deficient DE, and gland dysfunctions), and risk factors that aggravate the stability of precorneal tear film (PTF) resulting in hyperosmolarity and initiation of inflammatory reactions. Indoor environmental, occupational and personal risk factors may aggravate the PTF stability; factors such as age, contact lenses, cosmetics, diet, draft, gender, low humidity and high temperature, medication, outdoor and combustion pollutants, and VDU work. Psychological stressors may further influence the reporting behavior of eye symptoms. The impact of the risk factors may occur in a combined and exacerbating manner.
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Affiliation(s)
- P Wolkoff
- National Research Centre for the Working Environment, Copenhagen, Denmark
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