Medical Uses of Human Stem Cells

Because stem cells can differentiate into specialised cells, they have the potential to be used in medicine to replace cells in damaged or diseased tissues.

Stem cells are already used in this way in bone marrow transplants. Bone marrow transplants are used to treat blood cancers (such as leukemia and lymphoma) as well as some other conditions. In a bone marrow transplant, healthy adult stem cells from the bone marrow (often from another person) are used to replace damaged ones.

Diagram of a bone marrow transplant. The title at the top says "Bone Marrow Transplant". Below that is a drawing of a bone with a needle injecting something into it. The needle is filled with red fluid. A label line from the red fluid points to a drawing of a group bone marrow stem cells, indicating that these cells are in the fluid. The cells are labelled "Healthy Bone Marrow Stem Cells" and underneath them it says, "Injected into patient's bones".

In a bone marrow transplant, healthy bone marrow stem cells are injected into the patient's bones to replace damaged ones.

Many researchers are trying to develop stem cell treatments for other medical conditions. Most of this research is focused on using embryonic stem cells, since they can differentiate into a much wider range of cell types than adult stem cells.

Embryonic stem cells can be obtained from human embryos

At an early stage in the development of a human, the embryo becomes a ball of cells. Within this ball of cells, at one end, there is a clump of embryonic stem cells. Scientists have learnt how to extract these cells from a human embryo and keep them alive. The rest of the embryo is destroyed in the process.

Diagram showing the extraction of embryonic stem cells from a human embryo. On the left is a human embryo, labelled "Human Embryo". It consists of a ball cells. Within the ball of cells is a large cavity. At the bottom of this cavity there is a little clump of cells. An arrow shows embryonic stem cells being extracted from this clump of cells. The arrow is labelled, "Human embryonic stem cells extracted". The arrow splits in two. One branch points to a drawing of the extracted human embryonic stem cells. The other branch points to a drawing showing that the embryo has been destroyed in the process. This part of the diagram is labelled "Embryo destroyed in the process".

Embryonic stem cells can be extracted from a human embryo. The embryo is destroyed in the process.

In order to obtain embryonic stem cells for use in research or medicine, you need a human embryo to extract them from. There are two main ways to get human embryos for this purpose.

The first way is to use leftover embryos from a fertility treatment called IVF. In IVF, egg cells and sperm cells are combined outside of the body in a laboratory in order to produce several zygotes, each of which develops into a embryo. One of these embryos is implanted into the uterus of a person who wants to get pregnant. If the process is successful, this embryo will develop into a fetus and then be born. The rest of the embryos are unneeded. These embryos are sometimes used as a source of embryonic stem cells. If they were not used in this way, they would still be destroyed.

Diagram illustrating the way that spare embryos from IVF can be used as a source of stem cells. On the left, there is a vertical line of egg cells. To the right of each one is a plus sign, then a sperm cell, then an arrow and then a zygote. A label says, "Egg cells and sperm cells are combined in a lab to produce many zygotes". Each zygote then has an arrow which points to an embryo. A label says, "The zygotes develop into embryos". Each embryo is a hollow ball of cells containing a clump of cells. The top embryo has a label which reads, "One of the embryos is used in IVG". The other embryos have a label which reads, "The rest of the embryos can be used as a source of embryonic stem cells". Under this label, there is a diagram of two embryonic stem cells.

IVF is a fertility treatment used to help people get pregnant. It produces leftover embryos, which are sometimes used as a source of stem cells.

The second way is through a process called therapeutic cloning. In therapeutic cloning, an embryo is created using DNA from a patient. Embryonic stem cells can then be extracted from this embryo. These embryonic stem cells could then potentially be used to treat the patient. The advantage of using therapeutic cloning is that the stem cells that are produced are genetically identical to the patient's cells, so the patient's body will not reject them.

Diagram of the process of therapeutic cloning. A cell is obtained from the patient's body. An egg cell from a donor has its nucleus removed. The patient's is fused with the egg cell, so that the egg cell now contains the patient's nucleus. This egg cell then develops into an embryo which is genetically identical to the patient. Embryonic stem cells are then extracted from this embryo. In the process, the embryo is destroyed.

In therapeutic cloning, an embryo is created which is genetically identical to the patient. Embryonic stem cells are then extracted from this embryo. One day, it might be possible to use these stem cells to treat medical conditions.

Potential medical uses of human embryonic stem cells

Once human embryonic stem cells have been obtained, they can be cloned to produce more of them, and they can be made to differentiate into almost any human cell type.

It is hoped that these cells could one day be used to treat a wide range of medical conditions, including diabetes and paralysis.

Photograph of a patient with diabetes talking to a community health worker about their condition.

A patient with diabetes talking to a community health worker about their condition. It is hoped that one day it will be possible to use embryonic stem cells to treat diabetes, along with many other conditions.

Although there are many promising areas of research, so far there are no widely used medical treatments that use embryonic stem cells. Bone marrow transplants are the only widely used form of stem cell treatment and they use adult stem cells, not embryonic stem cells.

Problems with using human stem cells

There are problems with using human stem cells.

One problem is the risk of viral transfer. When stem cells from one person (a donor) are put into the body of another person (a patient), there is a risk that the donor could be infected with viruses, and these viruses could be transferred to the patient's body.

Another issue is that some people have ethical or religious objections to the use of human stem cells.

This is especially the case for embryonic stem cells since human embryos have to be destroyed to obtain them.

Also, in therapeutic cloning, the embryos which are produced are clones of an existing person. Of course, the embryos are destroyed and not allowed to develop further. However, some people may worry that such an embryo could one day be allowed to develop to maturity, in which case it would become a person who is a clone of an existing person. Also, some people may object to the production of embryos which are clones even if they are destroyed.


Flashcards help you memorise information quickly. Copy each question onto its own flashcard and then write the answer on the other side. Testing yourself on these regularly will enable you to learn much more quickly than just reading and making notes.


How can human embryonic stem cells be obtained for research and medical treatment?


What is the advantage of using therapeutic cloning rather than using embryos from IVF?


What can be done with human embryonic stem cells once they have been obtained?


How might human embryonic stem cells be used in the future?


What are some of the problems with using human stem cells?


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