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K. Higa, S. Shimmura, H. Miyashita, J. Shimazaki, K. Tsubota; Melanocytes in the Corneal Limbus Interact With K19–Positive Basal Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2098.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To identify the distribution and association of melanocytes with epithelial cells in the human limbus. Methods: Human limbal tissues were examined by whole mounts and serial histological sections to localize epithelial cells containing melanin granules. Immunohistochemistry in the basal epithelial layer of the limbus was done for cytokeratin 19 (K19), and melanocytes were identified by vimentin and the melanocyte–specific marker MART–1. Tyrosinase activity, the enzyme responsible for melanin formation, was assayed in non–pigmented donor tissue by the reaction with the enzyme substrate DOPA. Immunocytochemistry with anti–K19 and anti–MART–1 was done in dissociated limbal cells to analyze the ratio of MART–1 (+) melanocytes to K19 (+) epithelial cells. Results: Whole mount tissue from a pigmented donor revealed densely pigmented tissue corresponding to the palisades of Vogt in the limbal area. K19 positive cells were observed lining the limbal basal epithelium, which were highly associated with melanin granules. A superimposed image revealed that melanin granules were oriented towards the apex of each basal cell, acting as a pigmented cap facing the ocular surface. Melanocytes identified by vimentin and MART–1 were shown to exist as sporadic cells with dendritic processes that extend to pigmented basal cells. K19 (+) epithelial cells comprised an average of 48.7 ± 10.4 %, and melanocytes were found in the order of 5.3 ± 2.7 % of total cells in cytospin samples from 3 different donors. Tyrosinase assay confirmed melanocytes in non–pigmented limbal tissue. Conclusions: Melanocytes were sporadically located in the basal limbal epithelium in both pigmented and non–pigmented tissue. Tyrosinase positive melanocytes produce melanin, which are transported predominantly to K–19 positive basal epithelial cells.
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