The effect of nerve growth factor on hindlimb regeneration in Xenopus laevis froglets

Abstract

The effect of nerve growth factor (NGF) on hindlimb regeneration in postmetamorphic Xenopus laevis froglets was investigated. Two different dosage levels of NGF were tested on froglets whose hindlimbs had been amputated either above or below the knee joint. The course of regeneration in the NGF‐treated froglets was followed for 100 days post‐amputation.Treatment with NGF at a level of 2,500 Biological Units per froglet increases the extent of hindlimb regeneration attained compared with the controls, regardless of the level of amputation. On the other hand, a higher dose of NGF, 5,000 Units per froglet, does not alter the extent of hindlimb regeneration significantly. Treatment with NGF at either dosage does not appear to affect the shape or histological constitution of the regenerated limb segment. The general shape of the regenerate correlates with the level at which the limb was amputated. All regenerates obtained in this study conform to a common pattern in terms of histological constitution. They are composed of a central core of cartilage with a perichondrial membrane surrounded by a thin layer of connective tissue and covered by fully differentiated epidermis. No differentiated bone, muscle or nervous tissue was detected in any of the regenerates, but evidence of cartilage calcification was observed in limbs amputated below the knee. Possible implications of these results are discussed.