Characterization and categorization of fluorescence activated cell sorted planarian stem cells by ultrastructural analysis
Characterization and categorization of fluorescence activated cell sorted planarian stem cells by ultrastructural analysis
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DOI：
10.1111/j.1440-169x.2007.00947.x
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发表时间：
2007-09-01
影响因子：
2.5
通讯作者：
Agata, Kiyokazu
中科院分区：
文献类型：
--
作者：
Higuchi, Sayaka;Hayashi, Tetsutaro;Agata, Kiyokazu
Planarians具有再生能力，这是由称为neoblast的多能干细胞实现的。经典的超微结构研究表明，干细胞可以通过独特的细胞质结构（称为类染色体体）及其未分化特征来区分，并且它们可以通过X射线照射特异性消除。最近，通过使用荧光激活细胞分选术（FACS），根据DNA含量和细胞质大小，将真涡虫细胞分离成两个X射线敏感部分（X1和X2）和一个X射线不敏感部分（XIS）。在这里，我们通过透射电子显微镜（TEM）分析了分离的细胞。首先，我们发现未分化细胞（干细胞）和再生细胞（分化细胞）都集中在含有S/G2/M期细胞的X1级分中。再生细胞被认为是定向干细胞或祖细胞，这表明即使在细胞命运定向后，一些干细胞也可能保持增殖能力。其次，我们成功地鉴定出一种新型的干细胞，这种干细胞体积小，几乎没有类染色体，细胞核中富含异染色质。有趣的是，它们集中在含有G 0/G1期细胞的X2组分中。这些结果表明，涡虫干细胞不是同质的，但可能包括异质群体，像哺乳动物干细胞。
Planarians have regenerative ability made possible by pluripotent stem cells referred to as neoblasts. Classical ultrastructural studies have indicated that stem cells can be distinguished by a unique cytoplasmic structure known as the chromatoid body and their undifferentiated features, and they are specifically eliminated by X-ray irradiation. Recently, by using fluorescence activated cell sorting (FACS), planarian cells were separated into two X-ray-sensitive fractions (X1 and X2) and an X-ray-insensitive fraction (XIS) according to DNA content and cytoplasmic size. Here we analyzed the fractionated cells by transmission electron microscopy (TEM). First, we found that both undifferentiated cells (stem cells) and regenerative cells (differentiating cells) were concentrated in the X1 fraction containing the S/G2/M phase cells. The regenerative cells were considered to be committed stem cells or progenitor cells, suggesting that some stem cells may maintain proliferative ability even after cell fate-commitment. Second, we succeeded in identifying a new type of stem cells, which were small in size with few chromatoid bodies and a heterochromatin-rich nucleus. Interestingly, they were concentrated in the X2 fraction, containing G0/G1 phase cells. These results suggest that planarian stem cells are not homogeneous, but may consist of heterogeneous populations, like mammalian stem cells.