Blastemas

Blastema is a mass of relatively undifferentiated, proliferating cells that forms at a wound site during regeneration in certain animals, and in some contexts, in plants. The blastema serves as the tissue source from which new structures such as limbs, fins, or other organs are formed as regeneration proceeds.

In vertebrates, the best-studied examples occur in salamanders and newts, which can regenerate whole limbs after amputation. After injury, nearby mature cells dedifferentiate into a progenitor-like state and proliferate to build the blastema. The blastemal cells then re-differentiate to reconstruct tissues such as muscle, bone or cartilage, nerves, and connective tissue, under the influence of signaling from the wound epidermis and innervating nerves.

Similar blastemal tissue appears in other regenerating animals, including certain fish fins and various invertebrates, and in planarian flatworms where a blastema forms at the wound and supplies cells for regrowth of missing parts.

Formation and function of the blastema involve wound signaling, cellular plasticity, rapid cell division, and patterning cues that guide differentiation. Studying blastema biology informs regenerative biology and has implications for tissue engineering and medicine, though processes differ considerably across lineages.