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

Abstract

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.

Keywords::

• Sphere
• auditory pathway
• BrdU
• microarray

Acknowledgments

The authors thank Mikiya Asako and Seiji Bruce Shibata for their technical advice and assistance, and Kanna Nakagawa and Chikako Sougawa for their secretarial assistance. This work was supported by research grant B from Kansai Medical University, by the ‘Academic Frontier' Project for Private Universities, by ‘Strategic Research Base Development Program for Private Universities' matching fund subsidy from MEXT (Ministry of Education, Culture, Sports, Science and Technology), by grants from the Japanese Ministry of Education, Culture, Sports, Science and Technology (nos 16791029 and 18790740), and by a Fund from the Society for Research Aid in Otolaryngology, Kansai Medical University.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.