Limb Regeneration in Xenopus laevis

H. Matsuda, H. Yokoyama, T. Endo, K. Tamura, H. Ide

Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Japan

Limbs of urodele amphibians have high regeneration potency. Even in adult, complete limb regeneration occurs after amputation.

Limbs of mammals or birds have very low regeneration potency. Only finger tip regeneration occurs after amputation in mouse.

Anuran amphibians are in an important point between these two extremes. In Xenopus, limb bud at early stages (stage 51) regenerates completely. The regeneration potency decreases at advanced stages, and no regeneration occurs in stage 56 limbs, in which a definite cartilage pattern has already formed.

The decrease in regeneration potency paralleled with the decrease in fgf-10 expression in the limb mesenchyme. By implanting FGF-10 bead into the amputated limbs at stage 56, limb regeneration restored.

Limbs of Xenopus froglet form a spike, cartilage rod, after amputation. The expression of fgf-10 recovered in the amputated froglet limbs.

In some spikes, segmentation or bifuracation was observed, although the frequency is low.

FGF-10 may be responsible for the elongation of regenerated limbs. In the amputated limb bud at stage 56, FGF-10 induces limb regeneration with cartilage pattern, and in the amputated limbs of froglets, FGF-10 induces spike formation with poor cartilage pattern.

The difference in pattern formation potency between larval and froglet limbs may be concerned with signaling system such as SHH or Lmx.