Matrix metalloproteinase expression during blastema formation in regeneration-competent versus regeneration-deficient amphibian limbs.

We used an antibody array to compare the protein expression of matrix metalloproteinases (MMPs)-1, -2, -3, -8, -9, -10, and -13, as well as the tissue inhibitors of metalloproteinases (TIMPs)-1, -2, and -4 during blastema formation in amputated hindlimbs of regeneration-competent wild-type axolotls and stage-54 Xenopus, and regeneration-deficient short-toes axolotls and Xenopus froglets. Expression of MMP-9 and -2 was also compared by zymography. Both short-toes and froglet failed to up-regulate MMPs in a pattern comparable to the wild-type axolotl, suggesting that subnormal histolysis is at least in part responsible for the poor blastema formation characteristic of both short-toes and froglet. MMP levels were much lower in amputated stage-54 Xenopus limb buds than in the other animals, suggesting that blastema formation in these limb buds requires much less extracellular matrix degradation than in fully differentiated limbs. TIMP expression patterns followed the same trends as the MMP's in each group of animals.