Expression of the RNA-binding protein Musashi1 in adult liver stem-like cells.

Aim: Musashi1 is an RNA-binding protein that regulates the Notch signaling pathway in stem cells. Our previous study revealed that Musashi1 is expressed in early hepatocytes during liver development in the mouse. However, whether this unique protein is expressed with Notch signaling markers in adult liver stem-like cells remains unknown. Methods: Established hepatic stem-like cells (HSLC), which were derived from adult Sprague-Dawley rats, were used for experiments in vitro. HSLC were differentiated into mature cells in terms of producing albumin when co-cultured with epidermal growth factor (EGF). The mRNA expression of Musashi1, Notch family (Notch1 and Notch2), Jagged1 and Hes1 was examined in HSLC before and after cell differentiation using polymerase chain reaction-based techniques. Protein expression of Musashi1 was examined in the HSLC and normal mature hepatocytes by immunofluorescence staining. Results: The mRNA expression of Musashi1, Notch1, Jagged1 and Hes1 was detected in the original HSLC before culturing with EGF but not in primary cultured mature hepatocytes. The mRNA expression of Musashi1 and Hes1 was found to be downregulated in differentiated HSLC that produce albumin. Protein expression of Musashi1 was detectable in the original HSLC but not in both differentiated HSLC and mature hepatocytes. Conclusion: These findings demonstrate that the RNA-binding protein Musashi1 is expressed with Notch signaling markers in adult liver stem-like cells.