Background
Stem cells must be located and positively identified to elucidate their role in disease pathogenesis and therapy. In this study the expression patterns of the small intestinal stem cell (SISC) markers Musashi-1 (Msi1) and hairy and enhancer of split 1 (Hes1) were identified and the relationship between their expression and epithelial proliferation in the whole mouse small intestine was examined.
Material and Method
Mouse small intestines were separated into four segments. Msi1 and Hes1 expression levels were quantified in each intestinal segment by immunohistochemistry, real-time reverse-transcription polymerase chain reaction, and Western blot. Small intestinal epithelial proliferation was examined using the bromodeoxyuridine (BrdU) method and proliferating cell nuclear antigen (PCNA) immunostaining.
Results
Msi1- and Hes1-positive cells were predominantly detected at the crypt bases. Msi1 and Hes1 protein expression values were significantly higher in the jejunal segment than in the ileal (P<0.05) and mRNA was directly associated with protein expression values. Greater numbers of proliferative cells were detected in jejunal crypts with BrdU and PCNA labeling (P<0.05).
Conclusions
Expression of the Msi1 and Hes1 SISC markers in the small intestine was not homogenous and the markers were more highly expressed in jejunal tissues. This expression pattern correlated with the small intestinal epithelial proliferation pattern measured by BrdU- and PCNA-labeling methods.

Keywords: RNA-Binding Proteins - metabolism, RNA, Messenger - metabolism, Microvilli - metabolism, Nerve Tissue Proteins - metabolism, Jejunum - metabolism, Homeodomain Proteins - metabolism, Epithelial Cells - metabolism, Gene Expression Regulation, Biological Markers - metabolism, Basic Helix-Loop-Helix Transcription Factors - metabolism, Stem Cells - metabolism