Regenerations

Regeneration is the process by which lost or damaged tissues or organs are restored to their normal structure and function. It ranges from the regrowth of whole limbs in some animals to the replacement of cells within an organ. Regeneration is distinct from repair, which often leaves scar tissue and may not fully restore original architecture or function.

Biological regeneration proceeds through several strategies. Epimorphic regeneration involves the formation of a blastema, a mass of proliferating cells that reorganizes to recreate the missing structure. Compensatory or hypertrophic regeneration uses remaining tissue to restore function without creating a blastema, as seen in liver growth after injury. Stem cells and lineage-reprogrammed cells often supply the new cells, with signaling pathways guiding patterning and growth.

Notable examples include planarians, salamanders and axolotls capable of limb or tail regeneration; zebrafish can regrow heart tissue and fins; and some species regenerate lenses or parts of their eyes. In humans, liver regeneration after partial removal is well documented, and skin and bone repair are common, though the central nervous system has limited regenerative capacity.

Regeneration is a major focus of biomedical research, aiming to enhance intrinsic repair, grow tissues in the lab, or replace damaged organs. Variation among species and tissues, plus age and immune responses, influence regenerative capacity. Advances in understanding regeneration hold potential for therapies in regenerative medicine, tissue engineering, and stem cell biology.