How Does Blastema Help in Organ and Tissue Regeneration?
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.
Conclusion
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.
FAQs on What Is Blastema? Definition, Formation, and Function
1. What exactly is a blastema in the context of biology?
A blastema is a mass of undifferentiated cells that forms at the site of an injury or amputation in certain animals. These cells have the remarkable ability to grow and re-differentiate to regenerate a lost body part, such as a limb or a tail. It essentially acts as a pool of precursor cells that can rebuild complex tissues in their correct anatomical arrangement.
2. What is the primary function of a blastema during regeneration?
The primary function of a blastema is to serve as the control centre and cellular source for regenerating a lost organ or limb. It orchestrates the entire process by having its cells proliferate (multiply rapidly) and then differentiate into all the necessary cell types—such as bone, muscle, nerve, and skin—to form a complete, functional, and correctly patterned replacement structure.
3. What are some key examples of blastema-led regeneration in the animal kingdom?
Blastema-led regeneration is famously observed in several animals. Some of the most studied examples include:
- Salamanders and Newts: They can regenerate entire limbs, jaws, eyes, and portions of their brain and heart through blastema formation.
- Zebrafish: Capable of regenerating fins, scales, and even damaged heart muscle.
- Planarians (Flatworms): These simple organisms exhibit extraordinary regenerative abilities, where a small fragment can regenerate into a complete new worm via a blastema.
4. How is a blastema formed after an animal loses a limb?
The formation of a blastema is a multi-step process. First, epidermal cells from the surrounding skin migrate to cover the wound surface, forming a structure called the Apical Ectodermal Cap (AEC). Beneath the AEC, mature cells from tissues like muscle and cartilage undergo dedifferentiation, reverting to a more primitive, stem-cell-like state. These undifferentiated cells then accumulate and multiply, creating the blastema which serves as the foundation for the new limb.
5. Why can't humans and other mammals typically form a blastema to regenerate limbs?
Humans and most mammals have lost the ability for large-scale epimorphic regeneration for several reasons. Our immune systems are highly reactive to injury, leading to rapid scar tissue formation instead of blastema formation. Scarring effectively creates a physical barrier that prevents the underlying cellular processes of dedifferentiation and organised growth. Furthermore, mammalian cells have more robust mechanisms to prevent cells from reverting to a pluripotent state, as a safeguard against cancer.
6. What is the difference between the cells in a blastema and embryonic stem cells?
While both are pluripotent, there is a key difference. Embryonic stem cells are naturally undifferentiated and can give rise to any cell type in the body. In contrast, the cells of a regeneration blastema are often derived from adult somatic cells that have undergone dedifferentiation. A crucial distinction is that blastema cells often retain 'positional memory'—meaning a muscle-derived blastema cell is more likely to form muscle again, and it 'knows' whether it came from an upper arm or a wrist, ensuring correct patterning.
7. How do the cells within a blastema 'know' what specific structure to regenerate?
Blastema cells rely on a concept called positional information. The cells retain a molecular 'memory' of their original location within the limb (e.g., shoulder vs. hand). This information, encoded by genes like the Hox genes and guided by signalling from the Apical Ectodermal Cap (AEC) and surrounding tissues, dictates the regeneration pattern. This ensures that if a hand is amputated at the wrist, the blastema regenerates only the hand, not another full arm.
