Understanding Stem Cell Research

by Zoë Gamble
Human Embryonic Stem Cell

Human Embryonic Stem Cells CC-BY-SA Nissim Benvenisty

The words ‘stem cells‘ should be familiar to most people, but what may not be familiar is what they actually are, and how they are used in research. Media coverage on embryonic stem cells in particular (stem cells that are taken from an early embryo) has been polarised. So what are they, miracle cure or tampering with nature?

What is a stem cell?

A stem cell is a type of cell in our body that is undifferentiated. That is, a cell that has yet to become a particular type such as a skin cell, a muscle cell or a liver cell. As well as specialising into a particular cell type, they also replicate to create more stem cells.

Types of stem cell

There are two broad categories of stem cell: adult stem cells and embryonic stem cells. Stem cells are also classified by their potency – their ability to become other types of cells.

Unipotent – gives rise to just one type of cell.

Multipotent – can give rise to several types of cells, but are limited. One example is haematopoietic cells, which can differentiate into all types of blood cells.

Pluripotent – has the potential to develop into nearly all the cells in the body. For example, stem cells isolated from an embryo.

Totipotent – has the ability to create any cell. The only true human totipotent cell is a zygote (when a sperm fertilises an egg). After about 4 days of replicating, they begin to specialise to create pluripotent cells.

In medicine, they hold exciting possibilities to be used in cell replacement therapies, regenerative medicine, and are useful clinical tools for drug stem cell screening and research.

Induced Pluripotent – an adult cell that has been reprogrammed, and ‘regressed’ back to a state of reduced differentiation. This is an interesting one to consider – there are no ethical considerations with the source of the cells as no embryos are used to create them, and there is no risk of immune rejection. However, the question remains as to whether induced pluripotent cells are functionally equivalent to embryonic stem cells, and to what extent an induced pluripotent cell ‘remembers’ its previous fate.

Stem cell therapies

Bone marrow transplant

This is by far the most widespread type of stem cell therapy, used in severe cases such as leukaemia. This involves taking haematopoietic stem cells from either the patient or a donor, and then destroying the malignant cells within the patient. This also destroys their own bone marrow cells. The donor cells are then transplanted into the patient, restoring the ability to create bone marrow. It is not known as a controversial treatment, although as it is a dangerous procedure it is only normally performed in patients with a life-threatening condition.

Other therapies that have been approved include the use of umbilical cord blood for treating blood and immunological disorders, and using stem cells from the patient’s own eye to treat eye damage.

Cloning

The word ‘cloning‘ might bring to mind unethical practices, or even Dolly the sheep. Reproductive cloning is where an entire organism is cloned. Dolly the sheep was the first mammal to be cloned from an adult cell. However, human reproductive cloning is illegal in the UK and many other countries.

Therapeutic cloning begins in the same way as reproductive cloning. A normal adult cell (somatic cell) is taken from the patient and the nucleus (the part containing all the genetic information) is removed. This nucleus is then transferred to an egg cell that has had its own nucleus removed. The resulting cell – consisting of the patients’ genetic information inside the donor egg cell – then behaves like an embryo.

In reproductive cloning, this cell would be transplanted back into a surrogate womb, as was the case with Dolly. In therapeutic cloning, the cells are replicated in the lab and researched. They offer huge potential in not only enhancing our understanding, but also in providing novel cures.The hope is that in the future, these cells would be able to be transplanted back into the patient and treat diseases such as Parkinson’s disease or diabetes. They also offer potential benefits in the field of donor organs.

Stem cell technique: therapeutic vs reproductive cloning

Derived from image by Schorschski and Groth CC BY-SA 3.0

Problems

One problem with therapeutic cloning is that it is an incredibly difficult procedure, and it can require many attempts before a viable cell is created.

Another problem is a question of the ethics of therapeutic cloning. With reproductive cloning, the general consensus is completely against the creation of a cloned human being and the scientific community agrees that the risks and ethics of this completely outweigh any potential benefits. However, it is not so clear cut in the case of therapeutic cloning, since the process involves the destruction of an embryo – an embryo that has the potential to develop into a human baby. Some liken this to abortion, and believe that the destruction of the embryo is no different to the destruction of any other human life. Others believe that the pros outweigh the cons, and see the embryos as cells, which we may in time derive important, perhaps life-saving research from.

Embryonic Stem Cell Debate

There are compelling arguments for and against embryonic stem cell research. The main arguments on each side are listed below.

Against
  • The creation of a new embryonic stem cell destroys a potential human life.
  • Using embryos in this way devalues human life, and is the start of a slippery slope to allowing other unethical practises.
  • They are not needed. Therapies have been successfully developed from other types of stem cells taken from adults
  • There are new techniques available to create similar cells that do not destroy an embryo.
  • Any embryonic stem cells therapies will be limited due to a likelihood of immune reaction.
For
  • The cells are taken from ‘left-over’ embryos from in-vitro fertilisation. If not used in research, these embryos are incinerated. It is better to utilise this resource than allow it to go to waste.
  • Embryonic stem cells are the ‘gold standard’ of stem cells, against which all others are compared, and offer the greatest potential for future therapies.
  • Alternative methods of creating similar cells require more research before they may be used with any success.
  • Human trials with embryonic stem cells are currently underway, with some success. For example, macular degeneration patients having their vision improve after one treatment.

 

Whatever your personal views on the different types of stem cells and stem cell research, there is no doubt that they hold a strong potential for exciting new therapies and cures in the future.

 

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About the Blogger – Zoë Gamble

Zoë is a STEM Communicator and trainer for science made simple. She has a BSc. Functional Genomics and Stem Cell Science, MSc. Science, Media and Communication, and over 5 years’ experience presenting science to audiences around the world.

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Posted in Biology