title: Side population cells in the mouse thyroid exhibit stem/progenitor cell-like characteristics.
abstract: Side population (SP) cells are characterized by their ability to efflux the vital dye Hoechst 33342 (Sigma-Aldrich, St. Louis, MO) due to expression of the ATP binding cassette (ABC)-dependent transporter ABCG2, and are highly enriched for stem/progenitor cell activity. In this study we identified SP cells in murine thyroid, which are composed of two populations of cells: CD45(-)/c-kit(-)/Sca1(+) and CD45(-)/c-kit(-)/Sca1(-) cells. Quantitative RT-PCR analysis revealed that SP cells highly express ABCG2 and the stem cell marker genes encoding nucleostemin and Oct4, whereas the expression of genes encoding the thyroid differentiation markers, thyroid peroxidase, thyroglobulin (TG), and TSH receptor, and two transcription factors, thyroid transcription factor 1 (TITF1) and paired PAX8, critical for thyroid specific gene expression, are low in SP cells as compared with the main population cells. In situ hybridization and double immunofluorescence demonstrated that cells expressing Abcg2 gene reside in the interfollicular space of the thyroid gland. Approximately half and a small percentage of the ABCG2-positive cells were also positive for vimentin and calcitonin, respectively. After 9 wk under three-dimensional thyroid primary culture conditions, main population cells formed an epithelial arrangement and follicle-like structures that are immunoreactive for TITF1 and TG. In contrast, SP cells demonstrated very few morphological changes without any epithelial or follicle-like structure and negative immunostaining for TITF1 and TG. These results demonstrate that thyroid possesses SP cells that may represent stem/progenitor cells.
authors.affiliation: Laboratory of Metabolism, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Hoshi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kusakabe
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Taylor
authors.forename: Shioko
authors.initials: S
authors.lastname: Kimura
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000818:Animals; D018929:Cell Culture Techniques; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000502:physiology*; D006651:Histocytochemistry; D007453:Iodide Peroxidase / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D050814:Octamer Transcription Factor-3 / Q000235:genetics; D011989:Receptors, Thyrotropin / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D013954:Thyroglobulin / Q000235:genetics; D013961:Thyroid Gland / Q000166:cytology* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics
chemical_list: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C501412:Abcg2 protein, mouse; D017931:DNA Primers; D050814:Octamer Transcription Factor-3; C494174:Pou5f1 protein, mouse; D011989:Receptors, Thyrotropin; D014157:Transcription Factors; D013954:Thyroglobulin; D007453:Iodide Peroxidase