Regeneration across metazoan phylogeny: Lessons from model organisms

Comprehending the diversity of the regenerative potential across metazoan phylogeny represents a fundamental challenge in biology. Invertebrates like Hydra and planarians exhibit amazing feats of regeneration, in which an entire organism can be restored from minute body segments. Vertebrates like teleost fish and amphibians can also regrow large sections of the body. While this regenerative capacity is greatly attenuated in mammals, there are portions of major organs that remain regenerative. Regardless of the extent, there are common basic strategies to regeneration, including activation of adult stem cells and proliferation of differentiated cells. Here, we discuss the cellular features and molecular mechanisms that are involved in regeneration in different model organisms, including Hydra, planarians, zebrafish and newts as well as in several mammalian organs.