Role of Retinoic acid in Limb Regeneration

两栖动物肢体的再生胚泡已被广泛用于分析再生潜力和花纹形成。无尾两栖动物被认为是进行此类分析的有趣材料，因为在变态过程中再生能力逐渐下降。众所周知，维甲酸可以调节尾两栖动物的肢体模式。实验动物截肢后，在含维甲酸的水中饲养，诱发肢体近远端重复，前半胚基形成完整肢体，背侧半胚基形成完整肢体。结果如下：1.位置值从远端到近端，从前到后，从背侧到腹侧。本项目的目的是通过与斯托库姆教授的合作，观察维甲酸对无尾两栖动物修复肢体胚芽的影响。斯托库姆教授发现了尾部肢体胚芽的位置值的变化。结果如下：1.作为位置值后化的分子标记，维甲酸对无尾两栖动物修复肢体胚芽的影响Sonic hedgehog的表达(Shh)在非洲爪哇被检测到。shh在肢芽和胚泡的后缘表达，这是首次在胚泡中表达shh的证据。2.维甲酸抑制肢体的发育和再生，目前尚不清楚是否发生位置值的变化。3.通过移植由游离的肢芽间充质组成的重组肢芽，形成30-50指，这可能是由于胚泡中不同位置的间充质的分离和调节能力的丧失所致。维甲酸对这一多指形成的影响的研究正在进行中

Regeneration blastema of amphibian limbs has been widely used for the analysis of regeneration potency and pattern formation. Anuran amphibians were regarded as an interesting material for such analysis since the regeneration potency gradually decreased during the course of metamorphosis.Retinoic acid is known to modulate limb pattern in urodela amphibians. By rearing the animal in retinoic acid-contaning water after limb amputation, the proximo-distal duplication of limbs, complete limb formation from anterior half blastema and complete limb formationfrom dorsal half blastema have been induced which were caused by the changes in positional values from distal to proximal, from anterior to posterior and from dorsal to ventral.The aim of this project is to examine the effects of retinoic acid administration on the rehenerating limb blastema of anuran amphibians by collaborting with Prof.Stocum who found the changes in positional values in urodela limb blastema.The results obtained were as fllows :1.As a molecular marker for the posteriorization of positional value, sonic hedgehog expression (shh) was examined in Xenopus.shh was expressed in the posterior margin of limb bud and blastema, which was the first evidence on shh expression in the blastema.2.Retinoic acid inhibited the limb development and regeneration.It remains uncertain whether the chages in positional value occur or not.3.By grafting recombinant limb bud composed of dissociated limb bud mesenchyme, feet with 30-50 digits were formed, which may be induced by the sorting out of the mesenchyme with different positional values and loss of regulation potency in the blastema.The study on the effects of retinoic acid on this multiple digit formation is now in progress