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Blastema cells surrounded by transparent cystic spaces. Blastema.jpg
Blastema cells surrounded by transparent cystic spaces.

A blastema (Greek βλάστημα, "offspring" [1] ) is a mass of cells capable of growth and regeneration into organs or body parts. The changing definition of the word blastema since its introduction into the biomedical vocabulary in 1799 has been reviewed by Holland (2021). [2] Historically, blastemas were thought to be composed of undifferentiated pluripotent cells, but recent research indicates that in some organisms blastemas may retain memory of tissue origin. [3] Blastemas are typically found in the early stages of an organism's development such as in embryos, and in the regeneration of tissues, organs and bone. [4]


Some amphibians and certain species of fish and two species of African spiny mice can produce blastemas as adults. [5] For example, salamanders can regenerate many organs after their amputation, including their limbs, tail, retina and intestine. [6] Most animals, however, cannot produce blastemas.

Limb regeneration

When the limb of the salamander is cut off, a layer of epidermis covers the surface of the amputation site. In the first few days after the injury, this wounded epidermis transforms into a layer of signaling cells called the Apical Epithelial Cap (AEC), which has a vital role in regeneration. In the meantime, fibroblasts from the connective tissue migrate across the amputation surface to meet at the center of the wound. These fibroblasts multiply to form a blastema, the progenitor for a new limb. [7]

Blastema cells can differentiate into any cell type with the exception of neurons. This means axons which are cut can be regrown by blastema cells, but if the soma of a neuron is damaged then a new neuron is unable to be created. As a result, neural organs cannot be regenerated.

Blastema formation

Here is an example mechanism of what happens during neoblast specification during regeneration. Mechanism of neoblast specification during regeneration.jpg
Here is an example mechanism of what happens during neoblast specification during regeneration.

As stated above, there are several different types of organisms that can utilize a regenerative blastema as an adult. These organisms include urodele amphibians, zebrafish, and planarian flatworms as major creatures of study. In flatworms, the formation of a blastema needs adult stem cells that are called neoblasts for any type of regeneration to occur. [8] Flatworms use these undifferentiated cells for regeneration after paracrine factors can provide signals from the surface of the wound. The cells in the blastema are also referred to as clonogenic neoblasts (cNeoblasts) that are able to move to the site of the wound and reform the tissue. [9] In urodele amphibians, studies suggest that dedifferentiation of cells leads to the formation of a blastema that is able to form multiple tissue types after the amputation of their tails and wound healing occurs. [10] [11] In zebrafish, and in general, it seems as if experts are still uncertain of what truly forms the blastema. However, two common theories that have often been expressed are cell dedifferentiation and the recruitment of stem cells to the wound site. [12]

Involved signaling pathways

There are several different signaling pathways that have been shown to be involved with limb regeneration through the formation of the blastema. In flatworms, studies suggest that after using RNA interference Smad-beta-catenin-1 was found to set up the anterior-posterior axis. Inhibitions to this results in reversed polarity across the blastema. [8] Urodeles use hedgehog for dorsal-ventral patterning of their regenerating tail and its surrounding tissue. This was suggested by its inhibition leading to reduced blastemas. [11] Zebrafish seem to use IGF signalling in limb regeneration as its inhibition led to clues of them being required for blastema function. [13]

Related Research Articles

Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction, metamorphosis, and the growth and differentiation of stem cells in the adult organism.

Salamander Order of amphibians

Salamanders are a group of amphibians typically characterized by a lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All 10 present-day salamander families are grouped together under the order Urodela. Salamander diversity is highest in the Northern Hemisphere and most species are found in the Holarctic realm, with some species present in the Neotropical realm.

Axolotl Species of amphibian (salamander)

The axolotl, Ambystoma mexicanum, also known as the Mexican walking fish, is a neotenic salamander related to the tiger salamander. Although colloquially known as a "walking fish", the axolotl is not a fish but an amphibian. The species was originally found in several lakes, such as Lake Xochimilco underlying Mexico City. Axolotls are unusual among amphibians in that they reach adulthood without undergoing metamorphosis. Instead of taking to the land, adults remain aquatic and gilled.

Planarian Flatworms of the Turbellaria class

A planarian is one of many flatworms of the traditional class Turbellaria. It usually describes free-living flatworms of the order Tricladida (triclads), although this common name is also used for a wide number of free-living platyhelminthes. Planaria are common to many parts of the world, living in both saltwater and freshwater ponds and rivers. Some species are terrestrial and are found under logs, in or on the soil, and on plants in humid areas.

Regeneration (biology) Biological process of renewal, restoration, and tissue growth

In biology, regeneration is the process of renewal, restoration, and tissue growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. Regeneration can either be complete where the new tissue is the same as the lost tissue, or incomplete where after the necrotic tissue comes fibrosis.

Organogenesis is the phase of embryonic development that starts at the end of gastrulation and continues until birth. During organogenesis, the three germ layers formed from gastrulation form the internal organs of the organism.

Morphallaxis is the regeneration of specific tissue in a variety of organisms due to loss or death of the existing tissue. The word comes from the Greek allazein, (αλλάζειν) which means to change.

Iberian ribbed newt Species of amphibian

The Iberian ribbed newt, gallipato or Spanish ribbed newt is a newt endemic to the central and southern Iberian Peninsula and Morocco. It is the largest European newt species and it is also known for its sharp ribs which can puncture through its sides, and as such is also called the sharp-ribbed newt.

Floor plate Embryonic structure

The floor plate is a structure integral to the developing nervous system of vertebrate organisms. Located on the ventral midline of the embryonic neural tube, the floor plate is a specialized glial structure that spans the anteroposterior axis from the midbrain to the tail regions. It has been shown that the floor plate is conserved among vertebrates, such as zebrafish and mice, with homologous structures in invertebrates such as the fruit fly Drosophila and the nematode C. elegans. Functionally, the structure serves as an organizer to ventralize tissues in the embryo as well as to guide neuronal positioning and differentiation along the dorsoventral axis of the neural tube.

Retinal regeneration

Retinal regeneration refers to the restoration of vision in vertebrates that have suffered retinal lesions or retinal degeneration.

Epimorphosis is defined as the regeneration of a specific part of an organism in a way that involves extensive cell proliferation of somatic stem cells, dedifferentiation, and reformation, as well as blastema formation. Epimorphosis can be considered a simple model for development, though it only occurs in tissues surrounding the site of injury rather than occurring system-wide. Epimorphosis restores the anatomy of the organism and the original polarity that existed before the destruction of the tissue and/or a structure of the organism. Epimorphosis regeneration can be observed in both vertebrates and invertebrates such as the common examples: salamanders, annelidas, and planarians.

Betty Hay Cell biologist and Developmental biologist

Elizabeth Dexter “Betty” Hay was an American cell and developmental biologist. She was best known for her research in limb regeneration, the role of the extracellular matrix (ECM) in cell differentiation, and epithelial-mesenchymal transitions (EMT). Hay led many research teams in discovering new findings in these related fields, which led her to obtain several high honors and awards for her work. Hay primarily worked with amphibians during her years of limb regeneration work and then moved onto avian epithelia for research on the ECM and EMT. Hay was thrilled by the introduction of transmission electron microscopy (TEM) during her lifetime, which aided her in many of her findings throughout her career. Moreover, Hay was a huge advocate of women in science during her lifetime.

Regeneration in humans is the regrowth of lost tissues or organs in response to injury. This is in contrast to wound healing, or partial regeneration, which involves closing up the injury site with some gradation of scar tissue. Some tissues such as skin, the vas deferens, and large organs including the liver can regrow quite readily, while others have been thought to have little or no capacity for regeneration following an injury.

Hox genes in amphibians and reptiles

Hox genes play a massive role in some amphibians and reptiles in their ability to regenerate lost limbs, especially HoxA and HoxD genes.

Scar free healing is the process by which significant injuries can heal without permanent damage to the tissue the injury has affected. In most healing, scars form due to the fibrosis and wound contraction, however in scar free healing tissue is completely regenerated. Scar improvement, and scar-free healing are an important and relevant area of medicine. During the 1990s, published research on the subject increased; it's a relatively recent term in the literature. Scar free healing is something which takes place in foetal life but the capacity is lost during progression to adulthood. In amphibians, tissue regeneration occurs, for example, as in skin regeneration in the adult axolotl.

Bioelectricity Electric current produced in living cells

In biology, developmental bioelectricity refers to the regulation of cell, tissue, and organ-level patterning and behavior as the result of endogenous electrically mediated signaling. Cells and tissues of all types use ion fluxes to communicate electrically. The charge carrier in bioelectricity is the ion, and an electric current and field is generated whenever a net ion flux occurs. Endogenous electric currents and fields, ion fluxes, and differences in resting potential across tissues comprise an ancient and highly conserved communicating and signaling system. It functions alongside biochemical factors, transcriptional networks, and other physical forces to regulate the cell behavior and large-scale patterning during embryogenesis, regeneration, cancer, and many other processes.

Catherina Becker

Catherina Gwynne Becker is an Alexander von Humboldt Professor at TU Dresden, and was formerly Professor of Neural Development and Regeneration at the University of Edinburgh.

Starfish regeneration Star-shaped organisms

Starfish, or sea stars, are radially symmetrical, star-shaped organisms of the phylum Echinodermata and the class Asteroidea. Aside from their distinguished shape, starfish are most recognized for their remarkable ability to regenerate, or regrow, arms and, in some cases, entire bodies. While most species require some part of the central body to be intact in order to regenerate arms, a few tropical species can grow an entirely new starfish from a portion of a severed limb. Starfish regeneration across species follows a common three-phase model and can take up to a year or longer to complete. Though regeneration is used to recover limbs eaten or removed by predators, starfish are also capable of autotomizing and regenerating limbs to evade predators and reproduce.

Dedifferentiation is a transient process by which cells become less specialized and return to an earlier cell state within the same lineage. This suggests an increase in a cell potency, meaning that after dedifferentiation, cells may possess an ability to redifferentiate into more cell types than it did before. This is in contrast to differentiation, where differences in gene expression, morphology, or physiology arise in a cell, making its function increasingly specialized.

Neoblast Planarian regeneration proliferative cells

Neoblasts (ˈniːəʊˌblæst) are non-differentiated cells found in flatworms called planarians. Neoblasts make up about 30 percent of all cells in planaria. Neoblasts give planarians an extraordinary ability to regenerate lost body parts. A planarian split lengthwise or crosswise will regenerate into two separate individuals.


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Further reading