Adult Stem Cells: Facts, Research and Potential Medical Uses

An adult stem cell in the bone marrow is multipotent because it produces multiple types of cells, including red blood cells, white blood cells and platelets. This is a simplified diagram of stem cell activity in the marrow.
An adult stem cell in the bone marrow is multipotent because it produces multiple types of cells, including red blood cells, white blood cells and platelets. This is a simplified diagram of stem cell activity in the marrow. | Source

What Are Adult Stem Cells?

Adult stem cells are unspecialized but very important cells that are found at various sites in our body. Most of our cells are specialized and have specific characteristics to help them do their jobs. They are generally unable to divide. Stem cells divide repeatedly to produce the specialized cells that our body needs in order to repair minor injuries.

Adult stem cells have been found in many places in the body. For example, they've been discovered in the bone marrow, heart, brain, muscles, teeth and gastrointestinal tract. The list of locations is growing as scientists do more research. Despite their name, the cells are present in both adults and children.

Scientists are very excited by the potential benefits of adult stem cells. It may be possible to stimulate the cells to become more numerous and more active. It may also be possible to trigger them to produce specific target cells. In the future, adult stem cells may be useful in the treatment of major problems in the body.

A Stem Cell Overview

Although most forms of stem cell therapy are not used as medical treatments yet, bone marrow transplants are. Bone marrow contains hematopoietic stem cells. These produce all types of blood cells.

Cell Potency

"Potency" is the ability of an unspecialized stem cell to produce specialized cells. There are four types of potency.

  • Totipotent cells can produce all the cell types in the body as well as extraembryonic tissues, such as those needed to form the placenta. Extraembryonic tissues are needed for the embryo's development but aren't part of its body. The zygote is an example of a totipotent cell. A zygote is produced when an egg joins with a sperm. It's the first cell of a new individual.
  • Unipotent cells can produce only one type of specialized cell.
  • Multipotent cells can produce several types of specialized cells. For example, stem cells in the bone marrow can make red blood cells, white blood cells and platelets.
  • Pluripotent cells can form any cell type in the body. However, unlike totipotent cells, pluripotent cells can't make extraembyonic tissue.

Progenitor Cells and Target Cells

When an adult stem cell divides, it produces either two stem cells or one stem cell and one progenitor cell. The progenitor cell is slightly more specialized than the stem cell and undergoes additional divisions. The cells become more and more differentiated (or specialized) with each division. Eventually the target cells are produced. The target cells are generally ones needed by the tissue in which the stem cells are located.

The Wonder of Stem Cells

Functions of Adult Stem Cells in the Body

The job of adult stem cells is to replace cells that are damaged or have died. These cells include our red blood cells or erythrocytes, which live for only about 120 days, and our white blood cells, which are sometimes killed when fighting bacteria or other microbes. Stem cells in the lining of the small intestine produced the specialized cells needed for digestion and absorption. In the brain, stem cells can produce neurons (nerve cells) as well as the astrocytes and oligodendrocytes that support the neurons. Satellite cells are a type of stem cell in muscles.

The end products of stem cell division are controlled by factors inside the cell as well as by factors outside the cell. Gene expression (the turning on of specific genes), the prevention of gene expression, chemicals produced by other cells, additional chemicals in the cell's surroundings and physical contact with neighbouring cells can all have an effect on cell differentiation as cells become more specialized.

Mesenchymal stem cells are found in various tissues. They are multipotent and form bone, cartilage and fat cells. They may form other types of cells, too, although this is uncertain.

Satellite Cells in Muscles

Stimulating Stem Cell Activity

Stem cells seem to have a limited ability to repair damage in our bodies. Under natural conditions, they can't produce an entire organ or body part to keep us alive after we're injured. In addition, they are more numerous or more active in some areas of the body than in others. Still, their potential to replace injured tissue is exciting. It may be possible to stimulate their activity.

Researchers hope to discover the signals that trigger a stem cell to produce specific target cells. Scientists may then be able to produce large numbers of target cells in the laboratory or large numbers of stem cells directed to produce the target cells. The hope is that either the stimulated cells or unstimulated ones that have multiplied will be able to repair serious damage in a person's body. There have been some clinical successes using stem cell technology, but more research is needed before the technology is widely used.

An exciting discovery is that under certain laboratory conditions some multipotent stem cells can be stimulated to produce any other cell type instead of just a few types. These pluripotent cells may have very useful applications. However, the manipulation of stem cells to make them pluripotent or to direct their multipotency involves controlling genes in the cells, which raises safety concerns.

A Potential Method of Treating Heritable Diseases

Embryonic Stem Cells

In the early stages of stem cell research, cells from human embryos were used instead of cells from adults. Embryonic stem cells are still used in some research labs today.

The embryos that supply the stem cells are usually ones that remain after in-vitro fertilization. This is a procedure that helps some couples who have been unable to have children. Donated eggs and sperm are joined in laboratory equipment and then one or more of the resulting embryos are implanted in the woman's uterus. Multiple embryos are produced because the first embryo or embryos that are used may not implant in the lining of the uterus successfully. The embryos that are not needed by the couple are frozen and may eventually be used in embryonic stem cell research, with the couple's consent.

Embryos are used for research when they have completed about five days of development. At this stage an embryo is known as a blastocyst. The inner cells of the blastocyst are stem cells. Once the embryonic cells are obtained they are allowed to replicate in the laboratory, producing a huge number of stem cells for research as they continue to divide. The fact that the cells are pluripotent makes them especially useful.

The blastocyst and its pluripotent stem cells
The blastocyst and its pluripotent stem cells | Source

Controversy and a Problem

The use of embryonic stem cells is controversial, since when the original cells are obtained the intact embryo is destroyed and is unable to develop any further. Some people believe that a new human life begins the moment that a sperm joins with an egg. Another problem is that if cells derived from an embryo are placed inside someone's body, the recipient's immune system may treat the transplanted cells as invaders and destroy them.

Reducing the Controversy

The use of adult stem cells is much less controversial than the use of embryonic cells because the adult cells can be obtained from a donor without destroying human life. If the donor is also the person who needs a transplant of specialized cells or stem cells, the problem of rejection is eliminated, since the person's body won't attack its own cells.

Adult stem cells are also known as somatic stem cells. A "somatic" cell is a body cell, or one that isn't involved in reproduction. At first it was thought that adult stem cells weren't as valuable as embryonic stem cells, since the adult cells are multipotent but not pluripotent. Now scientists have found a way to trigger adult stem cells to become pluripotent.

In 2012, the Nobel Prize for physiology or medicine was awarded to Sir John Gurdon and Shinya Yamanaka for their discovery that adult cells can be reprogrammed to become pluripotent cells.

Making Pluripotent Stem Cells

Transformation of Adult Stem Cells into Pluripotent Cells

Adult stem cells may be transformed from multipotent cells into pluripotent ones by controlling which genes are expressed and by altering the chemical environment of the cells. The transformed cells are known as induced pluripotent stem cells, IPSCs, or IPS cells. They have a state much like that of an embryonic stem cell.

IPS cells are not ready to use in humans yet. One problem with the creation of induced pluripotent cells is that viruses are sometimes used to change the genetic programming of the original cells. Viruses are useful in biotechnology because some can add or remove genes from host cell DNA and some can change the gene expression of the host cell. In tests with animals, the viruses added to cells to reprogram them have sometimes caused cancer in their host. Researchers are trying to find ways to force adult stem cells to become pluripotent without increasing the risk of cancer development.

Some researchers have found that certain chemicals can trigger pluripotency in stem cells, which may be a viable alternative to virus use. Transforming adult stem cells into pluripotent stem cells safely could have enormous benefits in the field of medicine.

Making IPS Cells

Uses of Stem Cell Technology

Adult stem cell technology appears to be very promising, since in tests it has helped to improve certain symptoms and conditions. However, there is a great deal that researchers don't yet know or understand about stem cells and their actions in our bodies.

Some individuals, organizations and companies are making wonderful claims about the benefits of stem cell therapy. We need to be cautious when assessing these claims. Once scientists have a better understanding of how stem cells work and of how to control them, we may discover that some of the claims are true. We're not at this stage yet, however.

Researchers hope to be able to help a range of disorders with stem cell technology, including heart disease. A few ailing hearts have been helped by stem cell technology in test procedures. It's hoped that in the future insulin-secreting cells will be produced for implanting into the pancreas of people with Type 1 diabetes. Other diseases which may respond to stem cell therapy include Alzheimer's disease, osteoarthritis, rheumatoid arthritis, strokes, spinal cord injuries and burns.

Potential Uses of Stem Cells
Potential Uses of Stem Cells | Source

Additional Benefits of Adult Stem Cells

Even if stem cells and their products aren't used for transplants, they may still be useful. For example, they may be helpful in testing drug action in cells and in studying human development and birth defects. They may also be useful in the study of cancer. In addition, learning how stem cells work may help researchers develop new therapies for illnesses.

Early tests indicate that adult stem cell technology may have important benefits, but many questions about multipotent and induced pluripotent stem cells remain. For example, is it possible to stimulate multipotent cells to produce cells found in different tissues from the one in which the stem cells are located? What are the most efficient methods for making adult stem cells pluripotent? Are genetically altered stem cells safe?

A Doctor Warns About Unproven Stem Cell Therapy

Requirements for Successful Therapy

There are many requirements in order for stem cell technology to be successful as a therapeutic treatment.

  • The transplanted cells must be able to survive in the patient's body after the transplant.
  • They cells must be incorporated into the correct tissue or organ.
  • Unspecialized stem cells must divide repeatedly to produce a sufficient number of replacement cells for the patient.
  • The new cells must differentiate into the correct target cells.
  • The cells must remain active in the person's body for a long time.
  • The stem cells mustn't harm the recipient.

If all these requirements are met, some wonderful medical treatments may be available. A lot of researchers are investigating stem cells. Hopefully, new and effective ways to treat certain health problems will soon exist.

© 2012 Linda Crampton

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Comments 16 comments

teaches12345 profile image

teaches12345 4 years ago

So very, very interesting, Alicia. I am fascinated by the research on this subject and hope that it does lead to new hope and medical solutions for many. Voted up.


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you very much for the comment and the vote, teaches. I am very hopeful that adult stem cell technology will produce cures for diseases, too. If the safety issues can be addressed, the technology might provide a wonderful breakthrough in our ability to treat some serious illnesses.


Eiddwen profile image

Eiddwen 4 years ago from Wales

Interesting and useful ;thanks for sharing and enjoy your weekend.

Eddy.


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you, Eddy. I hope that you enjoy your weekend, too!


mary615 profile image

mary615 4 years ago from Florida

I've never fully understood the role of stem cells. Your Hub has helped me to better understand stem cells. I think it would be wonderful if research provided cures for diseases.

I voted this Hub UP, etc.


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you for the comment and the votes, Mary. It would certainly be wonderful if stem cell research enabled more diseases to be cured! I hope the technology becomes useful in the near future.


drbj profile image

drbj 4 years ago from south Florida

Exellent article about stem cell research, Alicia. In the future stem cells may help treat and possibly cure many medical problems including Parkinson's, Alzheimer's, diabetes, heart disease, birth defects, spinal cord injuries, cancer, and even repair damaged organs. It will be exciting to learn what breakthroughs this research may accomplish.


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you, drbj. Yes, the future of stem cell research looks as though it's going to be very exciting - and very important, too. It will be wonderful if diseases such as the ones that you mention are helped by stem cell therapy.


kashmir56 profile image

kashmir56 4 years ago from Massachusetts

Awesome hub and so well written and explained about stem cell research. Well done ! This was a fascinating read !


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you very much, Tom! I appreciate your comment.


Mama Kim 8 profile image

Mama Kim 8 4 years ago

Wonderfully informative and enlightening article Alicia! I'm voting and sharing this!


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you, Sasha! I appreciate your comment, the vote and the share very much.


conradofontanilla profile image

conradofontanilla 3 years ago from Philippines

Voted useful and interesting. Some suggestions, though. The differences between meiotic, mitotic and stem cells should be made clearer. Differentiation must be clarified. The term divide must be distinguished from the term differentiate. The phases or stages of differentation should be clarified if they are irreversible, and shown in their proper sequence, like totipotent, pluripotent, multipotent, unipotent (if in fact this is the sequence). The diagram does not show multipotent stage.

Last Dec. 17,2012 I had a talk with Dr. Arturo V. Estuita, MD, a Filipino internist and chelationist who also administers stem cell therapy. He told me of his shop talk with a fellow chelationist whom he visited in Quebec. Canada. He said that oral stem cell therapy triggers the stem cells to produce unipotent cells to replace torn off or worn off or diseased parts of the body. If an earlobe had been torn off stem cell therapy will regrow the earlobe using the original earlobe as scaffold. I have a Hub on this topic. Dr. Estuita said that his clinic has the capability to administer oral stem cell therapy. He said that cirrhosis and liver cancer can be prevented by oral stem cell therapy.

The technology of reprogramming adult cells into multipotent or unipotent stem cells makes the use of embryonic stem cells unnecessary and the ethical issues involved are now remote. In fact, cord blood can now be used in research and used to treat leukemia, among other degenerative diseases.


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Hi, conradofontanilla. Thank you for the votes. This hub is meant to be a basic guide to stem cells for beginners and I don’t want it to become too detailed (such as by referring to mitosis and meiosis). I will add more information about differentiation and potency when I next edit the hub, though. The second diagram does show the cells in their proper sequence based on potency, except as you say, the multipotent cells are omitted.

Bone marrow stem cells and stem cells from umbilical cord blood are used in mainstream medicine to produce new blood cells, but other stem cell therapies are considered experimental at the moment. Similarly, chelation is used in conventional medicine to treat poisoning by heavy metals but is considered experimental and unproven in other contexts.

Some of the experimental stem cell treatments are very interesting and are potentially very useful. However, it's extremely important that a patient checks with their regular doctor or doctors if they are considering receiving an unproven therapy in order to learn about any safety concerns. Some alternate health treatments may be useful and may eventually be accepted by mainstream doctors, but other treatments may be not only useless but also dangerous.

The use of reprogrammed adult stem cells may involve risks. Although these cells may be useful one day they are not ready to use in humans yet.


StaceyDematos profile image

StaceyDematos 19 months ago from Buda, TX

I am a stem cell transplant survivor. I fully support stem cell research. This procedure helped me gain my life back. Dr. Richard K. Burt is doing wonders with stem cell research for Autoimmune Diseases. I suffered from a debilitating autoimmune disease, CIDP, much like MS. I was almost to the point of needing a wheelchair. Today, I am 15 months post transplant an disease free and back to normal. I am running again and riding my bike and walk with no assistance.


AliciaC profile image

AliciaC 19 months ago from British Columbia, Canada Author

I'm so glad that stem cell technology helped you, Stacey. Thanks for sharing your interesting story.

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