EFFECT OF DENERVATION ON HINDLIMB REGENERATION IN XENOPUS-LAEVIS LARVAE

Xenopus laevis larvae at stages 51–57, according to Nieuwkoop and Faber [18], were subjected to amputation of the right hindlimb or of both limbs at the thigh or the tarsal level, as well as to somatic denervation of the right limb. Larvae at the same stage having undergone amputation of the right limb or of both limbs and sham denervation of the right limb were used as controls. In experimental series I a single denervation of the right limb was performed at the time of amputation. In experimental series II repeated denervations were performed (before, during and after amputation). Results show that in larvae at stages 51–53 subjected to limb amputation at the proximal level (thigh) even repeated denervation of the right limb did not prevent regeneration, although giving rise to various degrees of hypotrophy. In stage-55 larvae partial inhibition of the regenerative process in the right limb was clearly visible only after repeated denervations and amputation at the proximal level. After amputation at the distal level (tarsalia) the regenerative process in the right limb underwent no significant delay with respect to the controls, although the regenerated right limb was hypotrophic. In stage-57 larvae even a single denervation at the time of amputation was enough to inhibit regeneration of the right limb after either proximal or distal amputation. Therefore, in Xenopus laevis larvae, nerve-dependence for hindlimb regeneration takes place proximodistally as the nerve fibers grow in the limb and it gradually undergoes a process of proximodistal differentiation. Comparison of the regenerative processes occurring in regenerating innervated and denervated limbs amputated at various larval stages has revealed that the evolution of the regenerative process and the morphological complexity of the regenerate depend on the stage of development reached by the limb at the time of amputation rather than on extent of innervation. Therefore, in Xenopus laevis larvae, the decrease in the regenerative capacity of the developing hindlimb cannot be explaned solely in terms of extrinsic changes, i.e. through a reduction in the innervation of the limb, but could be dependent upon intrinsic changes occurring in limb cells during development. © 1990, International Society of Differentiation. All rights reserved.