| Lower vertebrates (amphibians and fish) can regenerate limbs, fins and tails. In higher vertebrates (reptiles, birds and mammals) the regeneration ability is remarkably reduced. Reptile tail regeneration is one example in which amniotes can regenerate a whole appendage organ effectively. Regeneration requires either stem cells or the ability to dedifferentiate. I propose that developmental related signaling molecules (beta-catenin, Msx, Shh and BMP) are recapitulated in this regenerative process. I cloned their reptile homologues and followed their changes during the phases of repair, re-epithelialization, blastema formation, morphogenesis, and differentiation. In the mesenchyme, the blastema progressed to form the hollow cartilage rod. In the epidermis, wound epithelium stratified forming neogenic scales, periodically arranged, from downward invaginations. Signaling molecules were expressed in a temporal-spatial dynamic fashion, similar but not identical to those expressed during development. Direction functional roles will be tested in future studies. |
