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C.S. de Paiva, D. Li, H. Kim, S.C. Pflugfelder; ABCG2 Transporter, a Potential Molecular Marker to Identify Human Corneal Epithelial Stem Cells . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2032.
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Purpose: ABCG2, a member of the ATP binding cassette (ABC) transporters, has been identified as a molecular determinant for bone marrow stem cells, and is a proposed universal marker for stem cells. This study evaluated the expression of ABCG2 by human corneal epithelial cells and it’s potential as a marker for corneal epithelial stem cells. Methods: ABCG2 expression in human corneal tissue and cultured corneal epithelial cells was detected by immunofluorescent staining and flow cytometry with BXP-21 monoclonal antibody. Total RNA was extracted from corneal and limbal epithelia, and subjected to RT-PCR with GAPDH as an internal control. Corneal epithelial cells isolated from limbal rims were selected by adhering to collagen IV-coated dishes for 20 and 60 minutes sequentially. Fractionated cell populations were evaluated for their growth potential on a mitomycin C treated 3T3 feeder layer and their expression of ΔNp63 and ABCG2 mRNA by RT-PCR. Results: ABCG2 protein was mainly located in the membrane and cytoplasm of basal epithelial cells of human limbus, but not cornea. Expression of ΔNp63 and ABCG2 mRNAs was higher in limbal epithelia than cornea. About 1-2% cells were positively stained or labeled with BXP-21 mAb in limbal epithelial cultures analyzed by immunofluorescent staining or flow cytometry. Isolated by adhesion, the rapid adhering cells in 20 min, accounted for 5-10% of the entire population, displayed the greatest growth capacity, the highest number of p63 positive cells, and the strongest expression of ΔNp63 and ABCG2 mRNA, compared with later adhering in 60 min, non-adhering after 60 min, or unselected cells. Conclusions: It was demonstrated for the first time that corneal epithelial cells express ABCG2 transporter, which is expressed by a population of basal limbal epithelial cells with putative stem cell properties.
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