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Friedrich E Kruse, Naresh Polisetti, Johannes Menzel-Severing, Matthias Zenkel, Ursula Schlotzer-Schrehardt; Immunoglobulin superfamily cell adhesion molecules (IgCAMs) as novel surface markers of limbal epithelial progenitor cells. Invest. Ophthalmol. Vis. Sci. 2014;55(13):518.
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© ARVO (1962-2015); The Authors (2016-present)
Interactions between stem cells and their surrounding microenvironment are critical for the regulation and maintenance of stem cell function. In order to define molecular cues of the limbal stem cell niche and to identify specific ocular surface markers of corneal epithelial progenitor cells, a comprehensive expression analysis of molecules related to cell-cell and cell-matrix adhesion was performed.
RNA from basal limbal and corneal epithelial cells was obtained from human corneolimbal specimens (n=5) by combining laser capture microdissection (LCM) and mRNA-amplification . Gene expression profiles of both cell populations were compared using a custom-made PCR array (RT2 profiler PCR array, Quiagen) including 86 genes related to cell-cell and cell-matrix adhesion. Differentially expressed genes were verified using specific real time PCR assays and immunofluorescence on cryosections of human donor eyes. In double labeling experiments, antibodies against putative stem cell and differentiation markers were additionally used.
Real time-PCR array and subsequent assay analyses showed increased expression levels of integrins (CD49d, CD18), cadherins (N-cadherin, P-cadherin) and heparin sulphate proteoglycans (syndecan-2, glypican-3 and -4) in LCM-isolated limbal epithelial progenitor cell clusters compared to corneal epithelial cells. In particular, several members of the immunoglobulin superfamily of adhesion molecules (Ig-CAMs) including ICAM-1 (CD54), VCAM-1 (CD106), L1CAM (CD171), JAM-C and Nectin-3 were highly (>100-fold) upregulated, whereas EpCAM (CD326) and the majority of integrins, cadherins, and tight junction proteins were clearly downregulated in limbal specimens. Accordingly, limbal progenitor cell clusters, which were characterized by positive staining for p63alpha, Keratin 15, p75NGFR and Sox-9, showed preferential immunoreactivity for all surface molecules identified, and were found to express ICAM-1, VCAM-1 and L1CAM predominantly along their basal aspects in close association with CD45-and CD11-positive immune cells.
These findings define IgCAMs and specific heparin sulphate proteoglycans as novel surface markers for limbal epithelial progenitor cells and suggest a functional significance for maintenance of the limbal stem cell niche.
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