Stem cell therapy, also known as regenerative medicine, promotes the repair response of diseased, dysfunctional or injured tissue using stem cells or their derivatives. It is the next chapter in organ transplantation and uses cells instead of donor organs, which are limited in supply.
Stem cells offer promise for new medical treatments. Learn about stem cell types, current and possible uses, and the state of research and practice.
Stem cells are a special type of cell that have two important properties.
Stem cells are able to make more cells like themselves. That is, stem cells renew themselves. Stem cells can become other cells that do different things in a process known as differentiation. Stem cells are found in almost all tissues of the body.
Stem cells are needed for tissue maintenance and for repair after injury.
Depending on where the stem cells are located, they can develop into different tissues. For example, hematopoietic stem cells are found in the bone marrow and can give rise to all the functioning cells in the blood. Stem cells can also become brain cells, heart muscle cells, bone cells, or other types of cells.
There are different types of stem cells.
Embryonic stem cells are the most versatile because they can develop into all the cells of a developing fetus. Most stem cells in the body have much less ability to produce cells and may only help maintain and repair the tissues and organs in which they are located.
No other cells in the body have the natural ability to produce new types of cells.
Why is there so much interest in stem cells?
Researchers study stem cells to see if they can help to: Improve our understanding of how diseases occur. By watching stem cells grow into cells in bone, heart muscle, nerves, and other organs and tissues, researchers can better understand how diseases and conditions develop.
Produce healthy cells to replace diseased cells (regenerative medicine). Stem cells can be directed to become specific cells that can be used in people to regenerate and repair tissues that have been damaged or diseased.
People who may benefit from stem cell therapy include those with leukemia, Hodgkin's disease, non-Hodgkin's lymphoma, and some solid tumor cancers. Stem cell therapy may also benefit people with aplastic anemia, immune deficiencies, and inherited metabolic conditions.
Stem cells are being studied to treat
Type 1 diabetes,
Parkinson's disease,
Amyotrophic lateral sclerosis,
Heart failure,
Osteoarthritis, and
other conditions.
Stem cells may have the potential to grow into new tissues for use in transplantation and regenerative medicine. Researchers continue to expand their knowledge of stem cells and their applications in transplantation and regenerative medicine.
Testing new drugs for safety and effectiveness. Before giving a drug in development to humans, researchers can use certain types of stem cells to test the drug for safety and quality. This type of testing can help assess drugs in development for toxicity to the heart.
A new area of study involves the effectiveness of using human stem cells that have been programmed into tissue-specific cells to test new drugs. In order for new drugs to be tested accurately, the cells must be programmed to acquire the properties of the type of cell the drug is targeting. Techniques for programming cells into specific cells are being studied.
Where do stem cells come from?
There are several sources of stem cells:
Embryonic stem cells. These stem cells come from embryos that are 3 to 5 days old. At this stage, the embryo is called a blastocyst and has about 150 cells.
These are pluripotent (ploo-RIP-uh-tunt) stem cells, which means they can divide into more stem cells or become any type of cell in the body. This allows embryonic stem cells to be used to regenerate or repair diseased tissues and organs.
Adult stem cells. These stem cells are found in small numbers in most adult tissues, such as bone marrow or fat. Compared with embryonic stem cells, adult stem cells have a more limited ability to produce the full range of body cells.
Adult cells altered Embryonic stem cells. Adult cells are modified to have the properties of embryonic stem cells. Scientists have turned ordinary adult cells into stem cells using genetic reprogramming. By changing the genes in adult cells, researchers can make them act similarly to embryonic stem cells. These cells are called induced pluripotent stem cells (iPSCs).
The new technique allows the reprogrammed cells to be used as a substitute for embryonic stem cells and prevents the immune system from rejecting the new stem cells. However, scientists don’t yet know whether using modified adult cells will cause adverse effects in humans.
Researchers have been able to take ordinary connective tissue cells and reprogram them to become functioning heart cells. In studies, animals with heart failure that were injected with the new heart cells had better heart function and survival times.
Perinatal stem cells. Researchers have found stem cells in amniotic fluid and umbilical cord blood. These stem cells can turn into specialized cells.
Amniotic fluid fills the sac that surrounds and protects a developing fetus in the womb. Researchers have identified stem cells in samples of amniotic fluid taken from pregnant women for testing or treatment — a procedure called amniocentesis.
Apple Stem Cell. Stem cell can be derived from the apple, grapes, with other fruits that can work in the same way every other stem cell works. This research carried to replace the rigourous process of producing the stem cell through the human embryo.
Why is there controversy over the use of embryonic stem cells?
Embryonic stem cells are taken from early-stage embryos — a group of cells that form when an egg is fertilized with sperm at an in vitro fertilization clinic. Because human embryonic stem cells are taken from human embryos, some questions have been raised about the ethics of embryonic stem cell research.
The National Institutes of Health created guidelines for human stem cell research in 2009. The guidelines define embryonic stem cells and how they can be used in research and include recommendations for embryonic stem cell donation. In addition, the guidelines state that embryonic stem cells from embryos created through in vitro fertilization can be used only when the embryo is no longer needed.
Where do these embryos come from?
The embryos used in embryonic stem cell research come from eggs that were fertilized at an in vitro fertilization clinic but were never implanted into a woman’s uterus. The stem cells are donated with the consent of the donor. Stem cells can live and grow in a special solution in a test tube or petri dish in a lab.
Why can’t researchers use adult stem cells instead?
Advances in cell reprogramming and the creation of iPSCs have greatly advanced research in this area. However, reprogramming is an inefficient process. When possible, iPSCs are used instead of embryonic stem cells because this avoids the ethical issues of using embryonic stem cells that may be morally objectionable to some.
While research on adult stem cells is promising, adult stem cells may not be as versatile and long-lasting as embryonic stem cells. Adult stem cells may not be able to be manipulated to produce all cell types, which limits how adult stem cells can be used to treat disease.
Adult stem cells are also more likely to contain irregularities due to environmental hazards, such as toxins, or from errors that cells make during replication. However, researchers have found that adult stem cells are more adaptable than previously thought.
What is a stem cell line, and why would researchers want to use them?
A stem cell line is a group of cells that all come from a single original stem cell and are grown in the laboratory. The cells in a stem cell line continue to grow but do not become specialized cells. Ideally, these cells remain free of genetic defects and continue to create more stem cells. Groups of cells can be taken from a stem cell line and frozen for storage or shared with other researchers.
What is stem cell therapy (regenerative medicine), and how does it work?
Stem cell therapy, also known as regenerative medicine, stimulates a repair response in diseased, dysfunctional, or injured tissue using stem cells or their derivatives. It is the next chapter in organ transplantation and uses cells to replace donor organs, which are in short supply.
Researchers grow stem cells in the laboratory. These stem cells are manipulated to specialize into specific types of cells, such as heart muscle cells, blood cells, or nerve cells.
These specialized cells can then be implanted into a person’s body. For example, if the person has heart disease, the cells can be injected into the heart muscle. The transplanted, healthy heart muscle cells can then help repair the injured heart muscle.
Researchers have shown that adult bone marrow cells directed to become heart-like cells can repair heart tissue in humans, and further research is ongoing.
Have stem cells been used to treat disease?
Yes. Doctors have been performing stem cell transplants, also known as bone marrow transplants, for decades. In hematopoietic stem cell transplants, stem cells replace cells damaged by chemotherapy or disease or serve as a way for the donor’s immune system to fight off some cancers and blood-related diseases. Leukemia, lymphoma, neuroblastoma, and multiple myeloma are often treated this way. These transplants use adult stem cells or umbilical cord blood.
Researchers are testing adult stem cells to treat other conditions, including some degenerative diseases such as heart failure.
What are some potential problems with using embryonic stem cells in humans?
For embryonic stem cells to be useful, researchers must be sure that they will differentiate into the specific cell types they want.
Researchers have found ways to direct stem cells to become specific cell types, such as directing embryonic stem cells to become heart cells. Research is ongoing in this area.
Embryonic stem cells can also grow irregularly or specialize into different cell types spontaneously. Researchers are studying how to control the growth and development of embryonic stem cells.
Embryonic stem cells can also trigger an immune response in which the recipient’s body attacks the stem cells as foreign invaders, or the stem cells may fail to function as expected, with unknown consequences. Researchers are continuing to study how to avoid these potential complications.
What is therapeutic cloning, and what benefits might it offer?
Therapeutic cloning, also called somatic cell nuclear transfer, is a way to create versatile stem cells that are independent of a fertilized egg. In this technique, the nucleus is removed from an unfertilized egg. This nucleus contains the genetic material. The nucleus is also removed from a donor cell.
This donor nucleus is then injected into the egg, replacing the removed nucleus, in a process called nuclear transfer. The egg is allowed to divide and soon forms a blastocyst. This process creates a line of stem cells that is genetically identical to the donor cell — essentially, a clone.
Some researchers believe that stem cells derived from therapeutic cloning may offer advantages over stem cells derived from fertilized eggs because the cloned cells are less likely to be rejected after being transplanted back into the donor. And it allows researchers to see exactly how a disease progresses.
Has therapeutic cloning in humans worked?
No. Researchers have not yet succeeded in therapeutic cloning in humans, although it has been successful in a number of other species. Researchers continue to study the potential of therapeutic cloning in humans.
