Nature is quite mysterious. Some animals can regenerate their limbs and body parts whereas some can do it to some extent. A non-symmetric mass of cells accumulates in an injury location where the regeneration part occurs. This mass is called a blastema. It can be found in almost all animals. The capabilities of a blastema to regenerate limbs and other body parts depend on the genetics of the animal. In this section, we will learn more about the meaning and cytology of blastema.
What is Blastema?
The lump of cells forming in the injured locations of an animal’s body or the uterus in the form of a zygote is called a blastema. This is an asymmetric accumulation of cells that occur either in an injured location or in the regeneration sites in an animal’s body. It can be found in the uterine cavity of the vertebrates. As the blastema meaning, this lump of cells can be found where regeneration of organs, limbs, tissues, etc takes place.
Many animals are capable of generating their lost limbs, organs, etc after an injury. The injured location starts growing cells. As per the histological reference, blastemas are made of undifferentiated pluripotent stem cells. These stem cells have the capability of giving birth to different tissues and organs. Previously, it was thought that these stem cells do not have any memory. They depend on the genetic messages for developing tissue or an organ. In fact, it was thought that the surrounding tissues helped or guided these pluripotent stem cells to divide systematically and generate tissues/organs.
The latest research suggests that the cells in a blastema can retain the memories linked to tissue origin. It means that the damaged tissue will be regenerated from those memories stored in the form of genes to give birth to an organ. Many animals, especially reptiles, can give birth to an entire limb or tail when amputated. Salamanders can regenerate different organs such as the intestine, retina, limbs, and tail. Most advanced animals in the kingdom do not have the power to produce blastemas.
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Formation of Blastema
As per the blastema meaning, the injured area of an animal’s body gets covered by a layer of apical epithelial tissue. The loss of a limb or an organ leaves an open injury. This tissue covers this open injury. The epidermis then becomes a signalling tissue layer that plays a vital role. In the meantime, the fibroblasts from the connective tissue start to accumulate in this location.
The amputation surface then bulges to form a blastema. These fibroblasts then start multiplying to form a lump. These are stem cells that started dividing to form the lost limb or organ eventually. The stem cells can remember the formation of previous tissues and follow the same. These fibroblasts in the blastema migrate within the injured area to take a position and initiate the process of regeneration. Only neurons are not regenerated. If the axons are damaged, they can be rebuilt using the same cells but the neurons are unable to regenerate from the fibroblasts. This is why the neural organs in an animal cannot be regenerated.
Which Organisms Can Regenerate Organs?
Many organisms can use this regenerative process to gain back their significant organs. In the adult stage, the redevelopment of the injured part occurs the same way it happened during the embryonic stage. In the animal kingdom, planarian flatworms, amphibians, zebrafish, etc can use blastema as a regenerative stage. Flatworms from blastema using the neoblasts for regeneration. These are undifferentiated cells that can take any tissue cell shape using the cell memory in the injured tissues.
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The paracrine factors generate signals that form these particular cells to form specific tissues that will eventually result in a new organ. The same undifferentiated cells have the power to regenerate new and different tissues. The experts in this field are researching the regeneration process of zebrafish and are still uncertain how it happens. Two common theories suggest the recruitment of specific stem cells and cell dedifferentiation in the wound site.
As it turns out, there are signalling systems in the physiology of the organisms that enjoy the regeneration process through the formation of the blastema. It has become a huge domain of science for research where scientists are trying to find out the regeneration ways using stem cells for replacing damaged organs. This process can reduce the risk of rejection of donated organs as the stem cells of the same patient will be used to develop new organs.
The formation of blastema and its function to generate new organs in an injured location is no less than a miracle of nature. Many primitive vertebrates and invertebrates can do the same to regenerate limbs and other organs to regain physical prowess. Extensive research in this field is going on to find out the specific ways to trigger stem cells for the formation of blastemas and to develop new organs.