NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES REGENERATION PAGE 1

Regeneration

Regeneration is the natural process of replacing or restoring damaged or missing 

cells, tissues, organs, and even entire body parts to full function in plants and animals. 

What are regeneration 

and regenerative medicine?

Regeneration is the natural process of replacing 

or restoring damaged or missing cells, tissues, 

organs, and even entire body parts to full 

function in plants and animals. Scientists are 

studying regeneration for its potential uses in 

medicine, such as treating a variety of injuries 

and diseases. Researchers also hope to learn 

more about the human aging process through 

studies of regeneration. This rapidly advancing 

field is called regenerative medicine.

A Mexican salamander can regenerate almost any limb, organ, or 

other body part. Credit: iStock 

What organisms can regenerate? 

All living organisms have some ability to regenerate 

as part of natural processes to maintain tissues and 

organs. Some animals have extensive regenerative 

abilities. For example, the tiny freshwater animal 

called Hydra can form two whole bodies after being 

cut in half. The axolotl, or Mexican salamander, is an 

animal with a backbone that can regenerate the form 

and function of almost any limb, organ, or other 

body part. 

This tiny freshwater animal Hydra can form two whole bodies after 

being cut in half. Credit: iStock 

More complex animals such as mammals have limited 

regenerative capacities. These include:

• Forming thick scars in tissues and skin to promote 

the healing of injured or amputated body parts. 

• Regrowing hair and skin. 

• Healing a bone fracture by using new tissue to knit 

the bone pieces together. 

How do different organisms regenerate?

Organisms regenerate in different ways. Plants and 

some sea creatures, such as jellyfish, can replace 

missing parts by extensively remodeling their 

remaining tissues.

Some animals such as lobsters, catfish, and lizards 

replace missing parts by first growing a blastema. The 

blastema cells rapidly divide to form the skin, scales, 

muscle, bone, or cartilage needed for 

creating the lost limb, fin, or tail.
NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES REGENERATION PAGE 2

In other animals, including humans, organs such 

as the liver undergo what’s called compensatory 

hypertrophy. When part of the liver is removed or 

destroyed, the remaining portion grows to the original 

size and allows the liver to function as it did before. 

Our kidneys, pancreas, thyroid, adrenal glands, and 

lungs compensate for organ loss in a similar, but more 

limited, way.

A planarian worm. Credit: iStock 

Research organisms that are particularly useful 

for studying regeneration include the blue-andwhite-striped zebrafish and the planarian, a type of 

flatworm. The zebrafish can replace a damaged or 

lost fin; and can also repair significant damage to its 

heart, pancreas, retina, brain, and even spinal cord.

T he regeneration of the f in on a zebraf ish caudal over 

several weeks. Credit : Alejandro Sánchez Alvarado 

The planarian uses organogenesis on a very large 

scale to regrow its entire body from a tiny fragment 

of its tissue if that piece of tissue contains one 

single neoblast. Humans have the same genes and 

pathways used by these animals; however, scientists 

don’t yet fully understand how to turn on or start such 

extensive regeneration in humans. 

The National Institute of General Medical Sciences 

(NIGMS) funds research to understand how 

regeneration works at the basic level, and why some 

organisms have less regenerative capacity than 

others. By studying regeneration in other species, 

scientists may learn more about how the human body 

heals and discover our regeneration pathways to 

repair damaged hearts or to even replace lost limbs.

What role do stem cells have in regeneration?

Stem cells play an important role in regeneration 

because they can develop into many different cell 

types in the body and renew themselves millions of 

times, something specialized cells in the body—such 

as nerve cells—cannot do. The primary roles of stem 

cells are to maintain and repair the tissue in which 

they’re found. Scientists are exploring whether a 

person’s own stem cells could “grow” replacement 

tissue that wouldn’t be rejected by the body’s 

immune system.

How is regeneration related to aging?

Throughout an organism’s life, its cells regenerate. 

But as part of the aging process, this ability gradually 

declines. To better understand the changes that occur, 

scientists are studying animals that show few signs 

of aging throughout their lifespans. Sea urchins, for 

example, can reproduce and regrow damaged parts 

throughout their lives. Because they maintain these 

abilities, sea urchins may help scientists answer 

questions about human aging as well as regeneration.
What type of regeneration research does 

NIGMS support? 

NIGMS-funded scientists are focused on 

understanding the basic features of regeneration. For 

example, researchers are looking closely at where 

the cells involved in regenerated tissue originate. 

State-of-the-art imaging tools let them watch tissue 

regeneration in living animals, and genetic techniques 

allow them to systematically identify the genes 

involved in regeneration. Many scientists are working to 

better understand the unique properties of stem cells 

and their role in regeneration. Others are looking for 

chemical compounds that could be used as medicines 

to stimulate regeneration. Knowledge gained from 

these basic biomedical studies will provide a foundation 

for future clinical applications.

Scientist working in a lab. Credit: iStock 

Learn More

NIGMS Resources

• Regeneration (Biomedical Beat blog posts) 

• Regeneration (Pathways)

• Research Organisms (Fact sheet)

• Understanding the Source of Regenerative Ability in 

Animals (Videocast)

• Glossary (Pronunciations and easy-to-understand 

definitions)

Other Resources

• Regenerative Medicine Innovation Project (NIH videocast)

• Skin Cells Can Be Reprogrammed In Vivo (NIH Director’s 

Blog)

• Stem Cell Information (NIH)

• Tissue Engineering and Regenerative Medicine (NIBIB) 

• Regenerative Medicine (The Partnership in Education)

Connect With Us:

NIGMS is a part of the National Institutes of Health that supports basic research to increase our understanding 

of biological processes and lays the foundation for advances in disease diagnosis, treatment, and prevention. 

For more information on the Institute’s research and training programs, visit https://www.nigms.nih.gov.

National Institute of General Medical Sciences | 45 Center Drive, MSC 6200. Bethesda, MD 20892-6200.

301-496-7301 | info@nigms.nih.gov

Content Updated April 2020

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