Laird Diana J, Weissman Irving L
Department of Biological Sciences, Hopkins Marine Station, Stanford University, Ocean View Boulevard, Pacific Grove, CA 93950, USA.
Dev Comp Immunol. 2004 Mar;28(3):201-9. doi: 10.1016/j.dci.2003.08.007.
Colonial organisms provide a unique experimental system for stem cell biology. The colonial Urochordate Botryllus schlosseri reproduces sexually as well as by continuous asexual budding. Adjacent colonies with a shared histocompatibility allele undergo vascular fusion and establish a common blood circulation, performing natural transplantation. Fused colonies become chimeras, often with complete somatic replacement of the host cell genotype by the fused parabiont. We attempted to establish a radioprotection assay for the somatic stem cells that induce long-term chimerism in Botryllus. We demonstrate over a range of radiation doses that neither autologous nor allogeneic cell transplantation enhances survival of host colonies. This suggests that high mitotic index associated with continuous asexual development leads to radiosensitivity of organs and structures essential to survival during engraftment. We observe that radiation induces uncontrolled epithelial cell proliferation in abnormally terminated buds, suggesting that stem cells are not required for the initial stages of bud development.
群体生物为干细胞生物学提供了一个独特的实验系统。群体尾索动物博特氏拟菊海鞘既能进行有性繁殖，也能通过持续的无性出芽进行繁殖。具有共享组织相容性等位基因的相邻群体进行血管融合并建立共同的血液循环，实现自然移植。融合后的群体成为嵌合体，通常供体联体生物会完全体细胞替代宿主细胞基因型。我们试图为在博特氏拟菊海鞘中诱导长期嵌合的体细胞干细胞建立一种辐射防护检测方法。我们在一系列辐射剂量下证明，自体或异体细胞移植均不能提高宿主群体的存活率。这表明与持续无性发育相关的高有丝分裂指数导致移植过程中对生存至关重要的器官和结构具有放射敏感性。我们观察到辐射会在异常终止的芽中诱导上皮细胞不受控制地增殖，这表明芽发育的初始阶段不需要干细胞。
