[Isolation, proliferation and differentiation of thyroid stem cell from human thyroid nodule tissue].

Objective To explore the presence of a characteristic stem cell population (side population,SP) in human thyroid gland and perform sphere culture method for the isolation and proliferation of thyroid stem cell.Methods Flow cytometry and cell sorting were performed to identify and isolate the ABCG2-positive SP cells from primary thyroid cells. The comparison of gene profiles and morphology between SP and main population (MP) were performed. Primary thyroid cells were also cultured in neurosphere-like growth condition for sphere formation.Gene profile of developed spheres was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and thyroid lineage commitment was then induced in a differentiating condition. In stem cell-derived thyrocytes,embedded in collagen to form follicles,TSH-dependent 125I uptake was measured.Results The SP was identified as a population enriched in stem cells with typical morphology,and characteristics of self-renewal and differentiation.Nonadherent clonal spheres developed in thyroid cell cultures,displaying an expression pattern resembling that of SP cells and in response to TSH and serum these sphere cells differentiated into thyrocytes expressing PAX8,thyroglobulin,sodium iodide symporter,thyroid-stimulating hormone receptor and thyroperoxidase mRNA.And there was TSH-dependent 125I uptake.Conclusion It is shown first time that human thyroid contains an undescribed population of cells with SP phenotype and clonal expansion capacity.Moreover sphere culture method is developed for the isolation and proliferation of thyroid stem cell. Key words: Thyroid; Adult tem cells; Cell separation; Cell culture technology; Cell differentiation