| Budget Amount *help |
¥3,780,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥180,000)
Fiscal Year 2007: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
In the Xenopus laevis intestine during metamorphosis, by the inductive action thyroid hormone (TH), the larval epithelium undergoes apoptosis, whereas stem cells appear, actively proliferate and form the adult epithelium similar to the mammalian one. In this study, we studied molecular mechanisms of the larval-to-adult intestinal remodeling as a model for mammalian organ regeneration, using culture and immunohistochemical procedures with transgenic frogs. Our results obtained are summarized as follows.
1. Using transgenic tadpoles expressing GFP under the control of CMV promoter, we showed that intestines isolated from the transgenic tadpoles continued to express GFP in vitro during TH-induced remodeling, but wild intestines did not. Then, to clarify the tissue origin of the stem cells, we performed epithelial-connective tissue recombination experiments with the wild and transgenic intestines and examined GFP expression of the stem cells, which can be identified in the cultured explants with immunohistochemical markers such as P-PTEN and Akt. Our results suggest the epithelial origin of the stem cells.
2. To investigate roles of epithelial-connective tissue interactions in the intestinal remodeling, we used intestines isolated from transgenic tadpoles expressing dominant positive TH receptor (dpTR), which can activate TR responsive promoters constitutively under the control of a heat shock-inducible promoter. We performed epithelial-connective tissue recombination experiments with the wild and transgenic intestines and cultured the explants in the absence of TH. Transgenic expression of dpTR in the epithelium alone induced apoptosis of the larval epithelium, but did not lead to development of the adult epithelium originating from the stem cells. This implicates that TH response genes expressed in the connective tissue are essential for the control of the stem cells. Thus, the Xenopus intestinal model is useful for clarifying molecular aspects of the stem cell niche.
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