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P. Eberwein, D. Boehringer, C. Auw-Haedrich, T. Reinhard; Limbal Stem Cell Marker Expression in Salzmann Nodules. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2617.
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Recently, increased Cytokeratin 19 (CK19) expression found in Salzmann nodular degeneration (SND) has been correlated with limbal stem cells lying in the basal epithelial layers of SND. To look at this aspect in more detail, the expression of Ck19, Connexin43, BCRP, p63, Enolase-, Inegrin-ß and Ck3/12 was analyzed in the basal epithelial layer of Salzmann nodule.
In accordance to the Declaration of Helsinki, 30 slides of patients with Salzmann nodular degeneration were stained. 3 independent, blinded examiners performed the analysis. 400 cells were counted in a pre-defined cut out in the basal layer and the relation of positive to negative cells was analyzed. For statistical analysis, a Kruskal-Wallis rank sum test was performed using the R-program.
Staining revealed greatest differences between the limbal (group 1) and the central corneal epithelium (group 2), such as group 1 expressed markers of differentiated corneal epithelium and group 2 expressed markers of limbal stem cells. SND (group 3) was either more close to group 1 or to group 2, depending on which marker was stained. Stem cell marker expression in group 3 was significantly lower for BCRP (p=0,001) and BCRP/p63 doublestain (p=0,05) and significantly higher for p63 (p=0,001) when compared to group 1. Looking at markers of differentiated epithelium (CK3/12) and undifferentiated proliferating epithelium (CK19) in group 3, expression was not significantly different compared to group 1 (p=0,27 for Ck3/12 and p=0,99 for Ck19), but significantly different compared to group 2 (p=0,001 for both). Integrin and Connexin 43 did not vary significantly between groups.
Staining of the basal epithelial layer in SND showed characteristic patterns in group 1 and group 2 and served as internal control. Staining in group 3 was neither completely like group 1 nor like group 2. On the one hand, stem cell markers were negative, but on the other hand, markers for differentiated corneal epithelial cells (CK3/12) were negative as well and markers of undifferentiated and proliferating cells (CK19) were positive. Taken all together, group 3 does neither express epithelial stem cell markers nor markers of differentiated epithelium. It seems to be in between the two other groups and could by this be very similar to the transient amplifying cells of the limbus, which exhibit similar staining patterns.
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