Bifurcation and segmentation in regenerating limb

具有完全再生能力的蝾螈和没有再生能力的哺乳动物在蛙肢再生能力方面表现出重要的特点。爪蟾断肢后，小爪蟾再生软骨杆、刺。发现穗是一个不完全再生，没有分叉和分节。此外，尖刺没有肌肉组织。为了诱导棘突分叉，我们检测了BMP的表达。骨突中未见BMP基因的表达，在骨突中植入含有BMP蛋白的微球可诱导软骨节段的形成。加入一种BMP抑制剂chordin完全阻断了分割的诱导。这些结果表明BMP在再生细胞的分割中起作用。SHH蛋白的植入增加了尖刺分叉形成的频率。将肌前体细胞移植到棘突内，诱导棘突内肌肉形成。肌肉组织的分化是由产生肝细胞生长因子的细胞观察到的，肝细胞生长因子是肌源性细胞的引诱物。这些结果表明，在刺突中肌肉组织的缺失至少可以部分恢复。

Frog limbs show important characteristics in regeneration potency between newt with complete regeneration potency and mammals with no rgeneration potency. Froglets of Xenopus lexis rgenerate cartilage rod, spike, after amputaion of limbs. The spike was found to be an incomplete regenerate without bifurcation and segmentation. Furthermore, the spike has no muscle tissues.To induce bifurcation in the spike, we examined the expression of BMP. No expression of BMP gene in the spike was observed, and implantation of beads contraining BMP protein into the spike induced the segment formation in the cartilage. THe induction of segmentation was completely blocked by the addition of chordin, a BMP inhibitor. These results suggest that BMP play a role in the segmentation of regenerates.The frequency of spike formation with bifurcation increased by the implantation of SHH protein.To induce muscke formation in the spike, Muscle precursor cells were transplanted into the spike. Differentiation of muscle tissue was observed in the spike by the cells producing hepatocyte growth factor, an attractant of myogenic cells. These results suggest that the lack of muscle tissues in the spike can be restored at least partially.