Characterization of side population (SP) cells in murine cochlear nucleus

Conclusion: We characterized side population (SP) cells in the cochlear nucleus (CN). Some genes of stem/progenitor markers in sorted SP cells were identified by microarray analysis and RT-PCR. Furthermore, some cells in the CN also demonstrated self-renewal and clonal expansion activities. These results suggest that tissue stem/progenitor like cells would be identified and characterized as a slow cycling and immaturity in SP cells of CN. Objectives: SP cells were sorted and characterized as regards their activity in the CN in order to identify the tissue progenitor/stem cells in the auditory nervous system. Methods: Bromodeoxyuridine (BrdU)-injected mice were prepared and the long-term BrdU-retaining cells were detected by flow cytometry. Gene expression of SP and MP cells was analyzed by microarray analysis and RT-PCR. SP cells were cultured in conditioned medium to expand stem/progenitor cells in vitro and to estimate the spheroid-forming activity of stem cells. Results: In all, 1% of cells in the CN were detected as BrdU-positive. SP cells were detected at a frequency of 4.4% and expressed stem/progenitor markers, Abcb1b, Abcg2, Sca1, Notch1, Notch4, Hes1, and Jag1 in microarray analysis. Expression of Abcb1b, Abcg2, Sca1, Oct3/4, and Sox2 as determined by RT-PCR was supported by the microarray data. CN cells also had sphere-forming activity in young mice, but this activity was decreased by aging.