The long-term goal of this project is to understand the mechanism of age-related meibomian gland dysfunction (MGD) and evaporative Dry Eye EDED. Recent published studies from our laboratory using Stimulated Raman Spectroscopy (SRS) to evaluate meibomian gland lipid quality (meibum) indicate that there is a decrease in protein content of normal meibum within individual glands as it moves progressively from the acinus to the orifice. This finding suggests that normal meibocyte differentiation involves removal of protein from meibum prior to release onto the tear film. Additionally our laboratory has shown that mice exposed to low humidity environmental stress, known to induce signs of EDED, display marked hyperproliferation of the meibomian gland with retention of protein in the meibum lipid suggesting that environmental stress induces abnormal or incomplete meibocyte differentiation. These findings support two alternative HYPOTHESES for the development of MGD:1) Environmental stress or aging leads to incomplete or abnormal meibocyte differentiation causing retention of protein in meibum, loss of lipid fluidity and inspissation. And 2) Aging and/or repeated environmental stress leads to depletion of meibocyte stem cells and meibomian gland dropout. These hypotheses emphasize two MAJOR GAPS in knowledge regarding meibomian gland function: GAP1, while the lipid composition of meibum and potential hormonal and other risk factors for MGD has been intensively studied, little is known regarding meibocyte differentiation and the cellular and molecular mechanisms that control this process. GAP2, although the turnover rate for the meibomian gland acinar cells has been studied, the presence of meibomian gland stem cells remains controversial and the effects of environmental stress, aging and sex are unknown. The following Specific Aims will test our hypotheses and explore these GAPS in knowledge: 1) Characterize using SRS the protein to lipid ratio (P/L) in expressed meibum from human subjects exhibiting signs and symptoms of EDED and correlate P/L ratio to EDED/MGD severity in a clinical study. 2) Identify the cellular and molecular mechanism of meibocyte differentiation and disintegration in vitro and determine the effects of environmental stress, aging and sex on meibocyte differentiation in vivo. 3) Identify the source of meibocyte and ductal epithelial renewal through lineage tracing and determine the effects of environmental stress, age and sex on meibomian gland ductal epithelial and meibocyte renewal using Confetti and the H2B-GFP/K5tTA mice and IT reconstruction.

Public Health Relevance

. Age-Related meibomian gland dysfunction (MGD) is a common eyelid disorder having a widespread prevalence of 39-50% in the US population and is a major cause of evaporative dry eye disease in the aging population. Our studies thus far suggest that age-related MGD in humans and mice involve altered meibocyte differentiation induced by age and environmental stress leading to retention of protein in the expressed meibum lipid. This proposal will evaluate the presence of protein in meibum as a function of MGD severity in patients, establish the cellular and molecular mechanism of meibocyte differentiation and determine the effects of environmental stress on meibocyte renewal.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Mckie, George Ann
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University of California Irvine
Schools of Medicine
United States
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Paugh, Jerry R; Alfonso-Garcia, Alba; Nguyen, Andrew Loc et al. (2018) Characterization of expressed human meibum using hyperspectral stimulated Raman scattering microscopy. Ocul Surf :
Kitano, Takashi; Yamada, Hiroshi; Kida, Maki et al. (2017) Impaired Healing of a Cutaneous Wound in an Inducible Nitric Oxide Synthase-Knockout Mouse. Dermatol Res Pract 2017:2184040
Mizoguchi, Shin; Iwanishi, Hiroki; Arita, Reiko et al. (2017) Ocular surface inflammation impairs structure and function of meibomian gland. Exp Eye Res 163:78-84
Hwang, Ho Sik; Parfitt, Geraint J; Brown, Donald J et al. (2017) Meibocyte differentiation and renewal: Insights into novel mechanisms of meibomian gland dysfunction (MGD). Exp Eye Res 163:37-45
Mizoguchi, Shin; Iwanishi, Hiroki; Kokado, Masahide et al. (2017) Ocular surface alkali injury damages meibomian glands in mice. Ocul Surf 15:713-722
Alfonso-GarcĂ­a, Alba; Paugh, Jerry; Farid, Marjan et al. (2017) A machine learning framework to analyze hyperspectral stimulated Raman scattering microscopy images of expressed human meibum. J Raman Spectrosc 48:803-812
Parfitt, Geraint J; Lewis, Phillip N; Young, Robert D et al. (2016) Renewal of the Holocrine Meibomian Glands by Label-Retaining, Unipotent Epithelial Progenitors. Stem Cell Reports 7:399-410
Parfitt, Geraint J; Brown, Donald J; Jester, James V (2016) Transcriptome analysis of aging mouse meibomian glands. Mol Vis 22:518-27
Jester, James V; Potma, Eric; Brown, Donald J (2016) PPAR? Regulates Mouse Meibocyte Differentiation and Lipid Synthesis. Ocul Surf 14:484-494
Parfitt, Geraint J; Kavianpour, Behdad; Wu, Karen L et al. (2015) Immunofluorescence Tomography of Mouse Ocular Surface Epithelial Stem Cells and Their Niche Microenvironment. Invest Ophthalmol Vis Sci 56:7338-44

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