Many factors are involved in the process of liver regeneration after the loss of hepatic tissue. Studies with hepatic restrictions in large animals and humans have established that the regenerative response is directly proportional to the amount of liver removed. Liver mass is precisely regulated and signals from the body can have negative as well as positive effects on liver size. Liver regeneration is an orchestrated response induced by such stimuli as hepatocyte growth factor, epidermal growth factor, transforming growth factor-alpha, insulin, and norepinephrine. Mechanical stresses and signals also play a role in wound response and regeneration.
Urodele amphibians provide exceptional examples of vertebrate regeneration after limb amputation.
The relationship between urodele regeneration and possible regeneration in mammalian prospects is hard to evidence, but the idea of possible epimorphic regeneration in mammals is an area of potential clinical importance that is under investigation. Homeotic Transformation of Crab Walking Legs into Claw by Autotransplantation of Claw Tissue . Crabs have easily distinguishable forelimbs, claws, hindlimbs, and walking legs as well as regenerative ability which make them a prime specimen on which to study pattern formation and regeneration. Upon autotransplantation of claw tissue into the stump of the fourth walking leg, the stump can regenerate a complete claw with normal handedness and the combined features of claw and walking leg. This suggests a role for both host and donor tissues in regeneration as well as homeotic transformation of tissue.