Kato K, Orii H, Watanabe K, Agata K
Laboratory of Regeneration Biology, Department of Life Science, Faculty of Science, Himeji Institute of Technology, Harima Science Garden City, Hyogo, 678-1297, Japan.
Dev Biol. 2001 May 1;233(1):109-21. doi: 10.1006/dbio.2001.0226.
We previously showed by grafting experiments that the dorsoventral (DV) interaction evokes morphogenetic events similar to those that occur in regeneration. However, it is not yet understood whether the stem cells themselves or differentiated cells have the ability to induce regeneration. Here we demonstrated by a combination of X-ray irradiation and grafting experiments that the dorsal and ventral positional cues inducing morphogenetic events are retained in X-ray-irradiated tissues, suggesting that the differentiated cells may be responsible for the positional cues. We grafted a small piece of irradiated worm, in which the stem cells were certainly eliminated, to an intact one in DV-reversed orientation. We observed that projections were developed from the host-donor boundary, as in the previous experiments. Whole-mount in situ hybridization with several markers demonstrated that the projections had a newly established DV axis and also had anterior or posterior characteristics. Furthermore, chimeric analysis with a strain-specific marker showed that the projections consisted of nonirradiated cells and that IFb-expressing cells, which normally belonged to the ventral tissue, could be generated even from the stem cells located on the dorsal side. Taken together, the findings suggest that the stem cells may simply differentiate depending on the surroundings and that differentiated cells may present positional cues that induce morphogenesis.
我们之前通过移植实验表明，背腹（DV）相互作用引发的形态发生事件与再生过程中发生的事件相似。然而，目前尚不清楚是干细胞本身还是分化细胞具有诱导再生的能力。在这里，我们通过X射线照射和移植实验相结合的方法证明，诱导形态发生事件的背侧和腹侧位置线索保留在X射线照射的组织中，这表明分化细胞可能是位置线索的来源。我们将一小片经过照射且干细胞肯定已被清除的蠕虫组织以背腹颠倒的方向移植到一个完整的蠕虫上。我们观察到，与之前的实验一样，在宿主 - 供体边界处形成了突起。用几种标记物进行的全组织原位杂交表明，这些突起具有新建立的背腹轴，并且还具有前部或后部特征。此外，用菌株特异性标记物进行的嵌合分析表明，这些突起由未受照射的细胞组成，并且即使是位于背侧的干细胞也能产生通常属于腹侧组织的表达IFb的细胞。综上所述，这些发现表明干细胞可能只是根据周围环境进行分化，而分化细胞可能提供诱导形态发生的位置线索。
