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James V Jester, Geraint John Parfitt, Yilu Xie, Krystal Ceballos, Behdad Kavianpour, Donald Brown; Low Humidity Alone Induces Meibocyte Proliferation in a Mouse Dry Eye Model.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):341.
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© ARVO (1962-2015); The Authors (2016-present)
Recent studies have shown that the mouse dry eye desiccating stress model with low humidity and scopolamine injection results in marked up-regulation of meibocyte proliferation leading to qualitative lipid changes in the gland. Since meibomian glands express muscarinic receptors, it is not known if the changes in the meibomian gland result from low humidity, scopolamine or both. The purpose of this study was to determine the effects of scopolamine on meibocyte proliferation and lipid synthesis.
C57Bl6 mice were housed in an environmental chamber with controlled humidity (12.7% ± 2.3%), temperature (26.7oC ± 0.5 oC) and light (12 Hr light/dark cycle) for 7 days with and without injection 3 times/day of 0.1 ml of 5 mg/ml scopolamine in PBS. Experimental animals and control mice housed in the animal facility were then sacrificed, eyelids collected, sectioned and stained for Ki67 to measure the meibocyte proliferation index. Additionally, a mouse SV40 meibocyte cell line and a human meibomian epithelial cell line were tested for the effects of scopolamine on cell proliferation and lipid synthesis.
Control mice showed a labeling index of 2.74 ± 0.22 cells/100 μm of basement membrane compared to 3.6 ± 0.40 for scopolamine injected and 4.43 ± 0.29 for low humidity alone. Low humidity with (p<0.01) and without (p<0.001) scopolamine resulted in a significantly greater meibocyte proliferation index than measured in control mice, however the labeling index for mice exposed to low humidity alone was significantly greater than that observed in scopolamine injected mice exposed to the same low humidity environment (p<0.02). In cell culture, scopolamine at concentrations of 1-100 μM showed no significant effects on either cell proliferation or lipid synthesis in either cell line.
Together these findings suggest that low humidity and increased ocular surface evaporation can regulate meibomian gland proliferation and potentially lipid synthesis.
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