Name: how tissues regrow and heal after injury
Uploaded: 2023-04-30T12:10:20.000Z
Duration: 1 min 19 s
Channel: JoVE

K12 Standards

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NC K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.2.1

Overview of Regeneration and Repair

Animal tissues frequently encounter damage due to accidental injuries and diseases, and also degenerate with aging.
Regeneration and repair are natural processes that help fix tissue damage and restore them to a certain extent.
Regeneration can physiologically restore damaged tissues and, in some animals, even complete organs, back to their fully-functional form.
For instance, some amphibians, such as salamanders, have extraordinary regeneration capabilities. They can fully regenerate their appendages, like limbs and tails; lower and upper jaws; and even the ocular tissues, including the retina and lens.
However, most animal tissues cannot regenerate fully. Instead, they heal through the repair mechanism, which can only reestablish the architecture of damaged tissue but not its complete function. Its main aim is to prevent blood loss and bacterial infection at the injury site.
For instance, injuries like burns and deep cuts in the skin are fixed by adding new connective tissues, mainly made up of cells and collagen, to the wound site; often, leaving behind a scar.

overview of regeneration and repair

Regeneration and repair processes are critical in healing damages caused by injury, disease, and aging. In regeneration, the damaged tissue is entirely replaced with new growth that restores the original architecture and function. In contrast, tissue repair usually results in a fixed tissue architecture involving scar formation. Scars generally do not reestablish tissue function and may also exhibit structural abnormalities at the injury site.
Regeneration
All animals have varying degrees of regenerative capabilities, but only some animals exhibit exceptional regeneration, such as generating an entire organ. For example, salamanders have a specialized population of stem cells that plays a significant role in regenerating fully functional limbs and tails. In mammals, only a few adult tissues like the liver, epithelium of the gut, and bone marrow can regenerate after an injury. The planarian flatworms, with a much simpler body structure, are capable of whole-body regeneration; if a planarium is cut into several pieces, each piece can develop into a completely new organism. Similarly, the hydra can regenerate its whole body even from a small fragment.
The regeneration process begins with the crucial step of covering the injury site. The epidermal cells migrate to the injury site, forming a thick covering called the apical epidermal cap. This is followed by clustering of undifferentiated fibroblast cells underneath the cap, forming a blastema. The blastema is a population of stem cells that has the potential to differentiate&#160; into any tissue or organ. The blastema is supplied with oxygen and nutrients via a new blood capillary network, allowing the cells to divide and differentiate.
Repair
The repair mechanism involves four phases: hemostasis, inflammation, proliferation, and remodeling. After an injury, the exposure of collagen&#8212; a structural protein in the walls of blood vessels&#8212; begins a coagulation cascade and vasoconstriction, thus, minimizing blood loss. During hemostasis, the clot fills the wound bed, providing a temporary matrix for the movement of various cells such as macrophages, neutrophils, and platelets. Platelet degranulation activates the complement cascade that stimulates inflammatory cells to attack the bacteria. During the proliferation phase, various cytokines and growth factors are released into the wound site, signaling the cells to proliferate and heal the wound. The final repair phase involves forming scar tissue that marks the completion of repair.

Regeneration and repair processes are critical in healing damages caused by injury, disease, and aging. In regeneration, the damaged tissue is entirely ...

Education

JoVE Core

Cell Biology

Unit 1

Regeneration and Repair

KEY TERMS AND CONCEPTS

how tissues regrow and heal after injury

Regeneration and repair are two ways the body responds to injury, disease, and aging. Regeneration replaces damaged tissue with new growth that restores the original structure and function. Repair usually leaves a fixed tissue pattern and forms a scar. Scars do not usually bring back full tissue function, and the injured area may still look or act abnormal.

Animals show very different levels of regeneration. Some, like salamanders, have specialized stem cells that help them regrow fully functional limbs and tails. In mammals, only a few adult tissues can regenerate well after injury, including the liver, the epithelium of the gut, and bone marrow. Planarian flatworms can regenerate an entire body from pieces, and hydra can also rebuild a whole body from a small fragment.

Regeneration starts when the injury site is covered by migrating epidermal cells. These cells form a thick layer called the apical epidermal cap. Undifferentiated fibroblast cells then gather underneath this cap and form a blastema. The blastema is a stem cell population that can differentiate into any tissue or organ. It is supported by a new capillary network that brings in oxygen and nutrients so the cells can divide and specialize.

Repair follows four phases: hemostasis, inflammation, proliferation, and remodeling. After injury, exposed collagen in blood vessel walls triggers vasoconstriction and the coagulation cascade, which reduces blood loss. A clot fills the wound bed and acts as a temporary matrix for macrophages, neutrophils, and platelets. Platelet degranulation also activates the complement cascade, which helps inflammatory cells attack bacteria.

During proliferation, cytokines and growth factors are released into the wound site. These signals tell cells to multiply and help close the wound. The final remodeling phase forms scar tissue and completes repair. This scar marks the end of the healing process, even though it may not restore the original tissue structure.

How Tissues Regrow and Heal After Injury

Regeneration and repair are two ways the body responds to injury, disease, and aging. Regeneration replaces damaged tissue with new growth that restores the original structure and function. Repair usually leaves a fixed tissue pattern and forms a scar. Scars do not usually bring back full tissue function, and the injured area may still look or act abnormal. Animals show very different levels of regeneration. Some, like salamanders, have specialized stem cells that help them regrow fully...

phases of wound repair

How Blood Clots Support Wound Healing

Wound healing begins when injured tissue works to restore its normal structure. In skin, this repair process depends on resident skin cells, blood mononuclear cells, the extracellular matrix, growth factors, and cytokines. Together, these signals guide the healing cascade. Deep injuries can damage blood vessels and cause blood loss. Endothelial cells release phospholipids from their ruptured membrane, which are converted into arachidonic acid and metabolites such as thromboxane A2 and...

whole body regeneration

Planarian Regeneration and Body Patterning

Planarian regeneration shows how a flatworm can rebuild missing body parts and restore the correct body pattern. Regeneration is the process of replacing injured or lost tissues, organs, or body parts. In some simpler organisms, whole-body regeneration is especially strong. Planarians are a key example because biologists study them to understand how this process works. Other organisms also have extreme regenerative ability. Hydra can regenerate so well that each piece can become a new...

liver regeneration

How the Liver Repairs Itself

The liver can repair itself after injury, and this process depends on several specialized liver cells. The liver also has key jobs in metabolism. It stores and redistributes carbohydrates, fats, and vitamins. It also releases bile salts, which help digest food and remove toxic metabolites from the body. The liver contains four major cell types: hepatocytes, stellate cells, Kupffer cells, and sinusoidal endothelial cells. Hepatocytes are large, polyhedral epithelial cells. They store glycogen,...

stem cell therapy for tissue regeneration

stem-cell-therapy-for-tissue-regeneration

Stem Cell Repair in Blood and Tissues

Stem cell therapy is used in regenerative medicine to repair damaged tissues and organs and help restore function. Stem cells can multiply and change into different tissue types, which makes them useful for tissue repair. One common example is hematopoietic stem cell transplantation, which is used in blood cancer treatment to replace damaged bone marrow and rebuild healthy blood cells. Two main stem cell types are used in stem cell therapy: adult stem cells and embryonic stem cells, or ESCs.

introduction to nuclear reprogramming

Nuclear Reprogramming in Cloning and Stem Cells

Nuclear reprogramming changes the gene expression of one cell type to match another cell type. It often shifts a differentiated cell into a more undifferentiated state. This process is important during development, morphogenesis, tissue regeneration, and malignancy. Cells can also be reprogrammed with laboratory methods. These include nuclear transfer, induced pluripotency, and cell fusion. Scientists use these approaches in molecular medicine, biotechnology, and oncology. A classic early...

methods of nuclear reprogramming

How Nuclear Reprogramming Changes Cell Fate

Nuclear reprogramming changes one cell type into another by epigenetic changes that shift gene expression. Epigenetic changes do not alter the DNA sequence itself. Instead, they change which genes a cell turns on or off. This process has uses in reproductive cloning for livestock propagation and in regenerative medicine, where patient-specific cells may help with injury repair. A key step in nuclear reprogramming is opening the DNA inside the nucleus so regulatory proteins can reach it. Cells...

cloning of dolly the sheep

How Dolly the Sheep Was Cloned

Dolly the sheep was the first successfully cloned mammal. She was born on 5 July 1996 at the Roslin Institute in Scotland, and her name came from the American singer Dolly Parton. Dolly lived for seven years, and she died from respiratory complications. Scientists think her shortened life may have been linked to the age of the DNA used to make her. In cloned cells, the DNA comes from an older individual. Analysis of Dolly’s DNA also showed shorter telomeres than those in other sheep of the...

key terms and concepts

Explore how regeneration and repair heal injury. Learn about blastema formation, clotting, inflammation, proliferation, and scar tissue in high school biology.

How Tissues Regrow and Heal After Injury | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

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Alabama Course of Study Science

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How Tissues Regrow and Heal After Injury

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