Vertebrate Limb Ontogeny and Limb Regeneration: Morphogenetic Parallels

Abstract

The problems in limb regeneration are the same as those of embryonic limb development. Supernumerary limbs can be induced by grafting foreign tissues to the flank of late urodele embryos. The basement membrane of the flank skin in the graft region, where the new limb will develop, is thin or absent, and an accumulation of mesodermal cells arises in this area. The embryonic limb bud, once established, is capable of self-differentiation and produces a complete limb, even if transplanted at an early stage. The specificity for limb quality of the skeleton resides in the limb bud mesoderm. This chapter discusses the morphogenetic factors acting in limb regeneration and the parallels that can be discerned with limb ontogeny. The chapter focuses on work performed with urodele blastemas obtained by amputation through the upper arm or leg, which are morphologically analogous to embryonic limb buds except that they do not give rise to elements of the girdle skeleton. The role of the epidermis in the morphogenesis of the autopodium, and the role of tissue mass in proximodistal organization of the limb might be important focuses of research.