blastéma

Blastéma is a term used in regenerative biology to describe a mass of undifferentiated, proliferating cells that forms at a site of injury and has the potential to grow into multiple tissue types, thereby reconstituting a lost structure. The word derives from Greek blastēs, meaning bud, and -ema, indicating a mass.

Formation and role: following injury, a wound epidermis covers the site and underlying cells respond by proliferating and/or dedifferentiating to establish a blastema. The cells within the blastema are largely progenitor or stem-like and stay capable of differentiating into various tissues required to reconstruct the lost organ or limb. Patterning and growth are coordinated by signals from surrounding tissues, guiding the blastema to restore correct form and function.

Occurrence and examples: blastemas are a central feature of regeneration in several groups. In amphibians such as salamanders and newts, limb and tail regeneration proceeds via a limb or tail blastema. In zebrafish, fin regeneration involves a fin blastema. Planarians form a blastema-like structure from neoblasts that enables whole-body regeneration. In mammals, blastema-like tissue has been observed in digit tip regeneration, and in some wound-healing contexts, though mammals show limited regenerative capacity compared with amphibians and fish.

Significance: the blastema concept is foundational to understanding vertebrate regeneration and informs efforts in regenerative medicine and tissue engineering. Studying how blastemas form, grow, and differentiate across species helps identify factors that may enhance or limit regenerative outcomes in humans.