人甲状腺成体干细胞的分离、培养及诱导分化

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

目的探索甲状腺成体干细胞的分离和培养方法。方法应用流式细胞荧光激活分选法从甲状腺结节组织中分离出侧群干细胞，从干细胞标志物表达及细胞形态特征等方面进行鉴定；同时应用悬浮培养方式促进干细胞的迅速增殖，进一步应用促甲状腺素（TSH）对甲状腺干细胞进行诱导分化，最后检测其基因谱及摄碘能力的变化。结果侧群细胞显示出典型的干细胞表达谱及细胞形态特征；同时在干细胞生长因子的刺激下甲状腺干细胞可以悬浮细胞球的方式迅速增殖，亦表达干细胞表面分子ATP一结合盒转运载体蛋白2（ABCG2）及甲状腺干细胞核因子。在TSH的作用下干细胞球来源细胞可逐渐分化为表达甲状腺分化标志物的甲状腺滤泡样细胞，并形成具有较强摄碘能力的滤泡样结构。结论存在于甲状腺结节组织中的干细胞能在干细胞生长因子的刺激下以细胞球的方式迅速扩增，并在TSH的诱导下向甲状腺滤泡样细胞分化。

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 ceils 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.