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L.J. Muller, A. de Wolf, C. Pool; Nuclear Size and Nuclear/Cytoplasmic (N/C) Ratio of Basal Epithelial Cells in the Limbus, Lateral and Central Human Cornea . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1106.
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© ARVO (1962-2015); The Authors (2016-present)
Several stem cell associated markers suggest that limbal basal epithelial cells are smaller than those in the cornea. As most quantitative studies were performed on dissociated roundish cells, we have focused here on their ultrastructure in tissue and on several quantitative morphological parameters.
Central, lateral and limbal samples of 6 fresh corneas from melanoma eyes with a short post–enucleation time (<1hr) were analyzed in plastic embedded serial–horizontal and vertical sections. Cellular and nuclear profiles were drawn with a drawing tube attached to a Zeiss light microscope (final magnification1000x), scanned with a flatbed scanner and measured with Image–pro Plus 5.0. Photographs were taken with an Axioplan light and a Tecnai® Philips electron microscope.
The electron dense nuclei of the closely packed basal cells in the limbus were irregular in shape and could be identified easily, even in horizontal ultrathin sections. They were significantly smaller (P<0.001) than the electron lucent nuclei in the cornea e.g. horizontal: limbal 32 ± 6 µm2 (n=417), lateral 48 ± 8 µm2 (n=440) and central 54 ± 8 µm2 (n=475). The clear morphological differences between limbal and corneal cells was reflected in the N/C ratio, which was more evident in the vertical direction: limbal 0.42 (n=125), lateral 0.24 (n=109) and central 0.25 (n=99) than in the horizontal direction: limbal 0.51(n=235), lateral 0.47 (n=179) and central 0.56 (n=230). In contrast to the columnar corneal basal epithelial cells with a relatively large cytoplasm (ratio ∼0.25 vs 0.5), the limbal basal epithelial cells in the clusters are oval to round in shape (ratio 0.42 vs 0.51) with a relatively small cytoplasm.
It is much easier to identify the delineated "stem cell" clusters in horizontal than in vertical direction. The current data show that measurements on dissociated limbal and corneal basal epithelial cells result in clear differences in size but not in shape.
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