Two doctors who paved the way for modern stem cell therapy were award the Nobel Prize in October for their pioneering work. Professor Arthur T Porter, on behalf of the National Stem Cell Task Force, said the event clearly establishes “the bona fides of this important new direction for the future of medicine”.
The Nobel Assembly at Karolinska Institutet, the body which administers the Nobel Prize, awarded the Nobel Prize in Medicine to Dr John Gurdon and Dr Shinya Yamanaka. Their pioneering work in cell biology was pivotal to the development of the science that is now called stem cell therapy.
“As there is much confusion regarding this particular topic, we thought that it be apropos to provide a short primer to guide a common understanding of stem cells today,” said Professor Porter.
- What are stem cells?
Stem cells are cells that are defined by being able to renew themselves and to differentiate. Renewal means that they can reproduce themselves and differentiation means that they can give rise to more mature, specialised cell types such as those that make up our tissues and organs.
- Are there different types of stem cells?
Yes, there are many different types of stem cells that come from different places in the body or are formed at different times in our lives. These include embryonic stem cells that exist only at the earliest stages of development and various types of ‘adult’ stem cells that appear during foetal development and remain in our bodies throughout life.
In addition, scientists have recently been able to create ‘induced pluripotent stem cells” or iPS cells in the laboratory. These cells, which are not found in nature but rather are engineered from specialised cells such as those from the skin or fat, have properties similar to those of embryonic stem cells.
- What are embryonic stem cells?
Embryonic stem cells are pluripotent stem cells, meaning they can give rise to all cell types of the body. This makes them very valuable for regenerative medicine.
Embryonic stem cells are obtained from a very early stage in development, usually the blastocyst stage, which in the human forms about 4-5 days after fertilisation of an egg. A blastocyst is a mainly hollow ball, barely visible to the naked eye. Inside is a clump of approximately 150 cells, called the inner cell mass that eventually forms the entire body of the developing animal. Embryonic stem cells are formed by removing the cells from the inner cell mass and growing them in culture.
- What are ‘adult’ stem cells?
Many tissues contain stem cells that can replace cells that die or restore tissue after injury. Skin, muscle, intestine and bone marrow, for example, each contain their own stem cells. In the bone marrow, many millions of new blood cells are made every day from blood-forming stem cells.
‘Adult’ stem cells are multipotent, meaning they can give rise to only some types of mature cell types, usually corresponding to the tissues in which they come from.
- What are ‘induced pluripotent cells’ or iPS cells?
Induced pluripotent cells (iPS cells) are normal cells that have been scientifically made to become pluripotent that is able to form all cell types of the body. In other words a cell with a specialised function (for example a skin cell) is ‘reprogrammed’ to an unspecialised state similar to that of an embryonic stem cell. While iPS cells and embryonic stem cells share many characteristics they are not identical.
iPS cells hold great promise for creating patient and disease-specific cell lines for research purposes. A great deal of work remains before these methods can be used to generate stem cells suitable for safe and effective therapies.
- Why is umbilical cord blood used?
Umbilical cord blood is rich in blood stem cells and is currently used as an alternative to bone marrow transplantation. Umbilical cord blood can be collected from the umbilical cord and placenta after birth, tested and stored frozen in tissue banks ready to use. The host-donor match required for transplantation is much easier, increasing the number of patients that can benefit.
- What is somatic cell nuclear transfer (SCNT)?
Somatic cell nuclear transfer (SCNT) is a technique in which the nucleus of a normal (somatic) cell is transferred into an egg that has had its original nucleus removed. The egg now has the same DNA, or genetic material, as the donor normal cell. Under the right conditions, the egg can develop as if it had been fertilised. The egg would divide to form two cells, then four cells, then eight cells and so on.
- What is bioethics and what are some of the ethical questions in stem cell research?
Bioethics is the study of the social, moral and ethical issues in the fields of scientific research, medical treatment and, more generally, in the life sciences. With advancing technology come new and exciting insights into scientific processes and diseases; at the same time new ethical issues arise.
One of the most commonly asked questions in stem cell research is whether it is ethical to use human embryos to procure embryonic stem cells. Furthermore, wherever there is the potential for medical treatments there are complex decisions that need to be made about how and when to begin trial treatments in humans, and if the trials are successful, how to make such treatments fairly available.
- Are stem cells currently used in therapies today?
Yes, a bone marrow transplant, also called a haematopoietic stem cell transplant, is a medical procedure used to treat conditions of the blood such as leucaemia, sickle cell anaemia, or some metabolic conditions. It relies on the haematopoietic (blood) stem cells that are present in the bone marrow that are the precursors to all blood cells. Doctors have been transferring blood stem cells by bone marrow transplant for more than 40 years.
Other stem cell applications are the use of skin progenitor cells for burns, and the use of limbal stem cells, which reside in the cornea, for injury of the eye.
“Over the next decade we will see great leaps forward in medicine. However, together with these opportunities will come challenges to society. We need to be well prepared to deal with these challenges to the benefit of the country,” said Professor Porter.