A Primer on Regneration

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The ability to restore lost tissues and body regions, a process known as regeneration, is broadly represented in both plant and animal kingdoms (Birnbaum and Sanchez Alvarado, 2008). Despite a wide phylogenetic distribution of regeneration abilities among metazoans, cumulative studies have identified a conserved series of events that take place during regeneration of complex animal structures (King and Newmark, 2012). Immediately following amputation, an organism recognizes damage and initiates wound healing, which is followed by programmed cell death in the vicinity of tissue damage and subsequent proliferation and migration of cells that foster the development of new tissue. Finally, rearrangement of pre-existing tissue and integration with newly differentiated cells restore the function and proportionality displayed prior to damage. While these conserved processes suggest that the ability to regenerate is ancestrally common (Bely, 2010), heterogeneity exists in some basic mechanisms displayed during regeneration in different animal species. Perhaps one of the most noticeable differences is the cellular source contributing to the formation of new tissue during regeneration. Organisms such as planarians and Hydra rely on active reservoirs of somatic pluripotent stem cells abundantly distributed throughout their bodies while vertebrates rely primarily on progenitor cell activation and dedifferentiation to generate cells with limited potential that then develop specific structures. However, not all regenerative events rely on cellular replacement. Recent research has identified autonomous repair mechanisms and functional regeneration of single cells – be it neurons or ciliated protozoa. The fact that organisms can achieve regeneration through diverse cellular sources is remarkable, but can these processes and conserved molecular pathways be activated to achieve regeneration in species lacking such abilities? Analysis of these pathways will contribute to better understanding of human development and provide potential avenues for regenerative medicine.


Presented at the National Academy of Sciences' 26th Annual Kavli Frontiers on Science Symposium, Irvine, CA, November 17-19, 2014.