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Sun Woong Kim, Xie Yile, Donald Brown, James V Jester; PPARγ Signaling Regulates Meibocyte Differentiation of Cultured Human Meibomian Gland Epithelial Cells (hMGEC). Invest. Ophthalmol. Vis. Sci. 2018;59(9):3831.
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© ARVO (1962-2015); The Authors (2016-present)
PPARγ is a lipid sensitive, nuclear receptor that regulates expression of genes involved in adipocyte differentiation. In recent studies we have shown that PPARγ agonists upregulates lipogenesis of mouse meibocytes in culture and is downregulated in aged mice and human meibomian glands. This study aims to evaluate the role of PPARγ in regulating meibocyte differentiation and lipid synthesis in a telomerized human meibomian gland epithelial cell line (hMGEC).
An immortalized HMGECs, a gift from David Sullivan, were cultured in DMEM/F12 supplemented with 10ng/ml EGF and exposed to the PPARγ agonist, Rosiglitazone (Rosi) at 10-50 μM for 24 hours. Cultures were also exposed to PPARγ antagonist, GW9662 or T0070907 to block PPARγ induced effects. Cells were then stained with Ki67 to determine the effect on the cell cycling and LipidTox to measure lipid synthesis. Expression of meibocyte differentiation related proteins such as PPARγ, ADFP, ELOVL4, and FABP4 were evaluated by quantitative PCR, western blotting, and/or immunocytochemistry. Gene expression and lipid synthesis following Rosi exposure were also investigated in an immortalized human corneal epithelial cell line (hTCEpi) as a comparison.
Rosi significantly decreased Ki67 staining within 24 hours in a dose-dependent manner (P = 0.003). Rosi significantly upregulated expression of PPARγ, ADFP, ELOVL4, and FABP4 by 5.7, 9.6, 2.6, and 3.3 folds on average, respectively (all P < 0.05 except for FABP4, which was P = 0.057) in hMGEC. T0070907 significantly abrogated Rosi-induced upregulation of these genes when treated prior to and during Rosi treatment (all P<0.05). Rosi also increased lipid accumulation in hMGEC and a specific PPARγ antagonist GW 96662 and T0070907 suppressed PPARγ induced lipid synthesis. The observed lipogenic differentiation responses were not duplicated in hTCEpi after exposure to Rosi.
Rosi induced cell cycle exit and upregulation of lipogenic gene expression leading to lipid accumulation in hMGEC. These effects were suppressed by PPARγ antagonist indicating that PPARγ signaling specifically directs lipogenesis in hMGEC. Based on these finding, we hypothesize that PPARγ is a master regulator of meibocyte differentiation. Identifying the major up-stream and down-stream modifiers of PPARγ signaling may provide novel approaches for treating meibomian gland dysfunction.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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