What is all the fuss about?Stem Cell Research

Stem cells may be seen as the basic ‘building blocks’ or ‘starter cells’ of the human body in that they have the potential to develop in to any possible cell line. Effectively all the cells in your body from the hair on your head down to the tip of your toe nails all started off in exactly the same form: that of stem cells

There are three main types of stem cells, categorised according to their location within the body and the time in life in which they occur.

1. Embryonic stem cells

Embryonic stem cells are those that are found in the first few days of embryo development. They are especially important to researchers as they have the potential to become any possible body cell. This has two big advantages:

  1. Embryonic stem cells are essentially immortal as they can be grown forever under the correct conditions. This eliminates the need to constantly harvest new cells for research.
  2. Embryonic stem cells can be manipulated to grow in to any desired cell line, enabling researchers to grow Set X of cells for use in one project, and Set Y for use in another, from exactly the same original cell batch. This eliminates the need to regularly acquire specific cell lines from adult subjects.

At present, researchers tend to use stem cells derived from mouse embryos. If human stem cells are used they are derived from embryos created for other purposes for example embryos that were created for the purpose of in-vitro fertilisation (IVF) but not eventually used.

Stem cell therapy or ‘therapeutic cloning’ differs slightly to stem cell research in that it is involves the creation of new embryos via the process of cell nucleus replacement (CNR). CNR involves taking the nucleus from a patient’s cell and placing it in a donated egg cell (that had already had its own nuclear material removed); and then promoting this new ‘embryo’ to develop. The genes and subsequent cell lines of that embryo would be almost identical to the patient’s own i.e. the embryo would effectively be an early clone of the patient.

Dolly the sheep was created by CNR whereby the nucleus of an adult sheep cell was inserted into an emptied egg cell. The embryo was then prompted to develop by an electrical impulse and subsequently implanted into the womb of another sheep.

It must be stressed however, that the creation of Dolly was essentially a form of ‘reproductive cloning’. This practice is expressly forbidden in humans with regulations stressing that no embryo created by CNR is to be implanted in to the womb of a woman. In vitro experimentation, in the form of therapeutic cloning is permitted in the UK but only under specific licensing conditions (as shall be outlined later).

Since embryos used in stem cell research, regardless of their source, will never be allowed to develop in to human beings (as they would do under normal conditions), it is the use of embryonic stem cells that makes up the largest area of debate surrounding the topic, with opponents claiming (in parallel with opposition to abortion) that such experimentation leads to the destruction of potential people.

It should also be stressed that the process of research on embryonic stem cells is difficult to say the least. Whilst the stem cells are in theory ‘immortal’ the process of initially promoting their growth and maintaining them over time is a delicate one. Subsequent, cell differentiation in to specific cell lines is more difficult still, especially if attempting to develop these cells in to tissue suitable for transplantation in to a live host.

Conversely, if transplantation were successful, it remains uncertain whether we could then prevent the cells continuing their unrestricted growth. Whilst this was originally the desirable feature of the cells, if allowed to grow in an unrestricted manner in a live host, the tissue may cure the initial problem that it were intended for but then may go on developing leading to the formation of multiple tumours. As with all forms of tissue transplantation, the potential for rejection would also still exist unless the tissue were grown as a result of stem cell therapy/therapeutic cloning.

2. Foetal stem cells

An embryo becomes a foetus at 8 weeks gestation. Foetal stem cells can be obtained at birth from blood from donated placentas or umbilical cords; or from aborted foetuses. Although many of these stem cells are differentiated, many still have their ability to develop in to any cell line.

These stem cells are relatively easy to collect and have been heralded as a major use as alternatives to bone marrow transplants since they have a lower potential for rejection especially within ethnic minorities where the numbers of bone marrow donors remains low.

However, research on childhood leukaemia sufferers that received foetal stem cell transplants, found pre-cancerous cell development even if the initial leukaemia were successfully treated, leading to higher rates of recurrence. Since, especially in leukaemias, treatments become less effective with increasing age and numbers of recurrences, this research is a significant blow to the use of foetal stem cells for such purposes.

3. Adult stem cells

Adult stem cells are found in the body throughout life. However, in contrast to an embryonic or undifferentiated foetal stem cell, an adult stem cell will only have the potential to develop in to one of a few specific cell lines, depending on its nature. For example, a haematopoietic stem cell may develop in to a neutrophil or erythrocyte but never in to an osteoblast or a myocyte.

This traditional view has, however, recently been questioned when researchers used haematopoietic stem cells from mice to develop other cell lines such as muscle, liver and even brain cells. The correlation to human adult stem cells remains to be seen.

Adult stem cells (obtained from bone marrow) have however have already been used in trials for cancer treatments and heart disease. However, obtaining bone marrow cells is a difficult procedure that can be potentially painful. It also yields relatively few cells. Cells from other body areas are in such small numbers that at present, researchers are unsure as to how to obtain them.

Whilst adult stem cells are more limited in terms of their potential use, they can be obtained without the use of embryos. Whilst the development of live human clones (reproductive cloning) is forbidden, initial trials have shown the potential for the use of therapeutic cloning in vitro to enable autologous transplantation (where a patient’s own stem cells are taken and transplanted back in to their own body) to be promising as treatment for certain diseases. This is especially promising since such transplantation does not pose any risk of rejection.

Consequently, research on adult stem cells has far fewer ethical considerations and opponents, compared to research involving embryonic stem cells. As such, the use of the term ‘stem cells’ for the remainder of this section can be assumed to refer to embryonic stem cells unless stated otherwise.