The long-term goal of this project is to understand the mechanism of age-related meibomian gland dysfunction (MGD) and evaporative Dry Eye. Recently we have shown that mouse and human meibomian glands undergo specific age-related changes including decreased acinar cell proliferation, acinar atrophy, and altered peroxisome proliferator-activated receptor gamma (PPARg) localization from cytoplasmic-vesicluar/nuclear in young to nuclear in old mice and humans. Since PPARg is a lipid sensitive, nuclear receptor implicated in regulating adipocyte and sebocyte differentiation and lipogenesis, our findings suggest that PPARg may be involved in modulating meibomian gland differentiation during aging. Based on these findings we propose that aging of the meibomian gland may result in down-regulation of PPARg leading to decreased meibocyte differentiation and lipid synthesis, gland atrophy, and a hyposecretory MGD. Currently, there is a MAJOR GAP in knowledge regarding the role of PPARg in meibomian gland function. To test this hypothesis we have develop novel imaging and cell culture systems to assess gland volume, lipid synthesis and their regulation by PPARg. Using non-linear optical (NLO) microscopy and array tomography we have volumetrically reconstructed the mouse meibomian gland and measured total, cellular and lipid volumes in young and old glands. Preliminary studies suggest that atrophy of aging meibomian glands involves a marked loss in the lipid volume suggesting decreased meibocyte differentiation. Additionally, we have used coherent anti-stokes raman spectroscopy (CARS) to identify the regional lipid profiles within the meibomian gland and have tentatively shown that there is an age-related change in the maturation of meibomian gland lipids moving from the acini into the duct. Furthermore, we have developed an SV40 immortalized mouse meibocyte cell line that synthesizes lipids and expresses PPARg. Using these novel tools we propose the following Specific Aims. (1). Establish the age-related changes in PPARg localization and associated gene expression patterns by quantifying the subcellular localization, post-translational modification and downstream response gene expression patterns in the mouse and human meibomian gland. (2) Determine the effects of aging on the meibomian gland by quantifying the volume and lipid synthesis using NLO microscopy and array tomography to volumetrically reconstruct the meibomian gland and CARS to assess regional changes in lipid components present in the acini, ductule and duct of the mouse and human meibomian gland. (3) Assess the effects of natural and synthetic PPARg ligands on lipid synthesis by quantifying the subcellular localization, post- translational modification and downstream response gene expression patterns in cultured mouse meibocytes. (4) Measure the effect of PPARg ligands on meibocyte differentiation in vivo by quantifying the changes in PPARg expression, meibocyte proliferation, gland volume and lipid synthesis in young and old mouse meibomian glands.

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 peroxisome proliferator-activated receptor gamma (PPARg) localization. Since PPARg is known to regulate lipogenesis and sebocyte differentiation, understanding its role in age-related MGD may provide a mechanistic understanding of evaporative dry eye as well as suggest novel therapeutic strategies for treating human MGD.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
1R01EY021510-01
Application #
8085875
Study Section
Anterior Eye Disease Study Section (AED)
Program Officer
Mckie, George Ann
Project Start
2011-09-30
Project End
2015-08-31
Budget Start
2011-09-30
Budget End
2012-08-31
Support Year
1
Fiscal Year
2011
Total Cost
$382,708
Indirect Cost
Name
University of California Irvine
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
046705849
City
Irvine
State
CA
Country
United States
Zip Code
92697
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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
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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; Geyfman, Mikhail; Xie, Yilu et al. (2015) Characterization of quiescent epithelial cells in mouse meibomian glands and hair follicle/sebaceous glands by immunofluorescence tomography. J Invest Dermatol 135:1175-1177
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
Jester, James V; Parfitt, Geraint J; Brown, Donald J (2015) Meibomian gland dysfunction: hyperkeratinization or atrophy? BMC Ophthalmol 15 Suppl 1:156

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