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I.K. Gipson, S. Spurr–Michaud, A. Tisdale; Membrane Associated Mucins and Ocular Surface Membrane Structure . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4774.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The apical surface of the corneal epithelium has membrane projections and folds termed microvilli and microplicae, respectively, which change in height and density as cells age at the ocular surface. The purpose of this investigation was to compare the distribution of the membrane associated mucins MUC1 and MUC16 on the surfaces of human corneal epithelium in a culture model that differentiates to produce microvilli and microplicae mimicking those found on the native epithelium. Methods: Immortalized human corneal–limbal epithelial (HCLE) cells were cultured to confluence in serum–free media, then switched to serum–containing media and cultured for 7 days. At confluence, cells express MUC1 but not MUC16. By 7 days of culture with serum, cells stratify and apical cells of stratified islands express MUC16. Cultures at both these stages were fixed in 4% paraformaldehyde, and MUC1 and MUC16 were localized on their surfaces using immunogold labeling followed by high resolution field emission scanning electron microscopy. Results: At confluence, prior to culture in serum, cells had branching filapodia–like projections as well as short microvilli on the apical cells. MUC1 localized to the short microvilli. After 7 days of culture with serum, some cells exhibited densely packed microvilli and others exhibited long ridges termed microplicae. MUC1 was prevalent on microvilli, but was sparsely localized on microplicae. By comparison, MUC16 also localized on microvilli, but was more densely aligned along the ridges of the microplicae. Conclusions: In human corneal epithelial cells in culture, MUC1 appears first on early emerging microvilli, even in the absence of serum. With the addition of serum and differentiation of the cultures, microplicae appear. Concomitant with this, MUC16 appears on both microvilli and microplicae, while MUC1 remains predominantly on the microvilli. These data suggest that membrane associated mucins are involved in the formation and differentiation of the surface features of the apical cells of the ocular surface.
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