Regeneration Potency of Xenopus Limbs

虽然蝾螈或蝾螈的截肢可以完全再生，但哺乳动物或鸟类等高等脊椎动物的再生只发生在肢体的远端边缘。在青蛙中，再生能力在变态过程中发生变化。早期蝌蚪的肢芽在任何近端-远端水平截肢后都能完全再生，但再生能力迅速下降，在变态的幼蛙中没有观察到肢再生。在非洲爪蟾，软骨杆，穗，形成代替。因此，青蛙肢体是一种适合于再生潜能分析的材料。我们分析了青蛙变态各阶段肢体再生的分子机制，并尝试诱导无再生能力或再生能力弱的肢体再生，发现肢体再生能力的降低是由于间充质组织的变化，特别是fgf-10表达的变化。将含有FGF-10蛋白的珠粒应用于变态晚期的后肢截肢部位诱导具有分段和分叉软骨的肢体。背腹信号也影响肢体再生能力。来自背表皮的信号因子可诱导再生肢体背间充质中Lmx-1的表达，但在变态后期肢体的表皮中该因子的表达较弱。在幼蛙中，切断后形成软骨杆（spike），但有些spike分叉或分节。此外，Hoxa-13的表达被发现在穗的远端区域的情况下，发展的肢体。应用含有SHH蛋白或PDGF的珠子增加了分叉或分段尖峰的频率。

Although amputated limbs of newts or salamanders regenerate completely, the regeneration of higher vertebrates such as mammals or birds occurs only distal margin of limbs. In frogs, the regeneration potency changes during metamorphosis. The limb bud of tadpoles at early stages regenerates completely after amputation at any proximal-distal levels, but the regeneration potency rapidly decreases and no limb regeneration is observed in the metamorphosed froglets. In Xenopus, a cartilage rod, spike, is formed instead. Thus, frog limb is a suitable material for the analysis of regeneration potency. We analyzed molecular mechanisms of limb regeneration in the frog at various stages of metamorphosis and tried to induce regeneration in the limbs with no or weak regeneration potency.The decrease in the limb regeneration potency was found to be caused by the changes of mesenchymal tissues, especially in the expression of fgf-10. Application of bead containing FGF-10 protein to the amputated site of the hindlimbs at advanced stages of metamorphosis induced the limbs with segmented and bifurcated cartilage.Dorsal-ventral signalling also affected limb regeneration potency. Signalling factor from dorsal epidermis induced Lmx-1 expression in the dorsal mesenchyme of regenrating limbs, but the factor was weak in the epidermis of the limbs at later stages of metamorphosis.In the froglet, a cartilage rod, spike, is formed after amputation, but some spikes were bifurcated or segmented. Furthermore, Hoxa-13 expression was found in the distal region of the spike as in the case of developing limbs. Application of beads containing SHH protein or PDGF increased the frequency of bifurcated or segmented spikes.