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Wendy R. Kam, Shaohui Liu, David A. Sullivan; Influence of Proliferation and Differentiation on Lipid Accumulation and Gene Expression in Human Meibomian Gland Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2012;53(14):597.
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© ARVO (1962-2015); The Authors (2016-present)
We hypothesize that factors (e.g. FBS) stimulating differentiation of immortalized human meibomian gland epithelial (SLHMG) cells will promote lipid accumulation, an upregulation of cell differentiation genes, and a downregulation of cell proliferation genes. We also hypothesize that: [a] FBS will induce analogous effects in primary human meibomian gland epithelial (PHMG) cells; and [b] agents inducing proliferation (e.g. epidermal growth factor [EGF] and bovine pituitary extract [BPE]) will have opposite molecular biological actions and will not facilitate lipid generation. Our goal was to test these hypotheses.
SLHMG, PHMG, or immortalized human conjunctival epithelial cells were cultured for varying time periods with or without FBS or EGF and BPE, followed by either staining with LipidTox neutral lipid stain and DAPI, or RNA extraction for Illumina BeadChip analyses.
Our studies show that: [a] differentiation, but not proliferation, is associated with a pronounced lipid accumulation in SLHMG cells. This lipogenic response is unique and not duplicated in conjunctival epithelial cells; [b] FBS-induced differentiation promotes significant upregulation in the expression of genes related to tissue development, cell differentiation, proteolysis, lysosomes, and apoptosis, and a reduction in those linked to cell cycle, M Phase, DNA replication, and translation; [c] FBS elicits the same responses (i.e. significant up- or downregulation) in over 2,500 genes in both SLHMG and PHMG cells; and [d] EGF and BPE-stimulated proliferation causes a significant increase in the expression of genes associated with the cell cycle, DNA replication, M phase, translation, and ribosomes, and a significant decrease in those related to tissue development, lipid metabolic processes, cell differentiation, intracellular transport, and PPAR signaling. EGF and BPE also induced an 8.3- to 36-fold increase in the mRNA levels of anti-oxidative stress genes, and an 8.7- to 252-fold decrease in the expression of keratinization- and immune-related genes.
Our results support our hypotheses and advance our understanding of the processes involved in the proliferation and differentiation of human meibomian gland epithelial cells.
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