Regenerative responses in larval axolotl limbs with skin grafts over the amputation surface.

Complete flaps of whole skin over the amputation surface of larval axolotl limbs did not prevent dedifferentiation, DNA synthesis, and mitosis. However, even by two weeks, insufficient cell division had occurred for blastema formation. In about 50% of the cases, small areas of wound epidermis formed over the amputated tip of the radius or ulna. At two weeks after amputation, mitotic figures and dedifferentiated cells which incorporated H3-thymidine were predominantly located in the vicinity of the small area of wound epidermis. Although delayed in relation to controls, these limbs regenerated. The results are consistent with the view that the wound epidermis is necessary to maintain dedifferentiated cells in the cell cycle.