Embryonic stem cells: Where to next?
Dr Peter Hollands
Anglia Polytechnic University, East Road, Cambridge, UK, CB1 1PT
Progress Educational Trust
08 May 2002
Back in the 1980's Bob Edwards and myself laid the theoretical and practical foundations for the current work on embryonic stem cells with a series of animal experiments. Since that time there have been further significant advances including the isolation of human embryonic stem cells. The question remains however as to the ultimate usefulness of this technology.
When Bob Edwards carried out his pioneering basic research in human fertilisation in vitro he was very aware of the potential which lay in the embryos he worked on. In his many publications he often refers to the possibility of growing, extracting and transplanting embryonic stem cells derived from human embryos. These ideas were brilliant in their conception and we are now at the stage where some of the initial ideas are becoming technically possible. It has now been clearly shown that human embryonic stem cells of various types including nerve, muscle and connective tissue can be grown in the experimental laboratory with reasonable efficiency.
If this technology is to grow then the first requirement will be the human embryos from which the stem cells are derived. This may or may not be a problem depending on where in the World the work is carried out but as we all know there are strict laws in many countries regarding any work on human embryos. One potential source of embryos for this kind of work is embryos donated to research from IVF clinics. This source would be acceptable for research procedures but if the process was taken to a clinical service then this source would be far too unreliable. It must be remembered that the first step in this work is to obtain a blastocyst which, despite all the efforts of the media manufacturers, is still rather hit and miss. A second source might be to create the embryo specifically for the recipient. Many people may find this idea repugnant but from a practical point of view this may be the best approach. Consider this scenario:
A couple with two children and one of the parents suffers damage to the spine in an accident resulting in paralysis from the neck down. The couple decide that they would like to create an embryo to provide stem cells to repair the damage to the spine and give that parent the chance to return to normal life. Is this acceptable? Similar real life questions are already being asked around the World and embryologists must join the debate. There is already a study underway in the UK where a healthy embryo is being selected using PGD to create a child which will subsequently donate its' umbilical cord stem cells to its' ill sibling. This is clearly very different to the scenario I have proposed as the embryo is allowed to grow on naturally and the 'waste product' umbilical cord stem cells are then used for transplantation. Nevertheless, it still involves an embryo providing donor cells and as such may lay the groundwork for further advances.
Therapeutic cloning is another potential source of embryonic stem cells for transplantation, possibly the most promising yet. Here the recipient would undergo a cloning procedure and the resultant embryo would be used to provide stem cells for transplantation back into the recipient. This is technically very difficult but if successful may offer an acceptable source of embryonic cells.
Another barrier which must be crossed is the potential problem which lies in the number of embryonic stem cells which would be required to provide a successful transplant into one recipient. It is well known that it is often difficult to obtain sufficient cells for a transplant from an umbilical cord blood sample. The problem will be amplified when using embryonic cells unless the properties of the embryonic cells are found to be very different. It may therefore be necessary to amplify embryonic stem cell numbers in vitro prior to transplantation perhaps using cytokines. Such studies on adult stem cells have had varying levels of success and this is an area which will require extensive research prior to any clinical applications.
Once cell lines of embryonic stem cells are obtained it may be possible to freeze them for later use. Some people even seek to patent such cell lines for their own gain! I personally disagree with such activities unless the money is put directly back into research and development and ultimately to treatment.
This brings me nicely to the final part of the puzzle which is the recipient. It may be possible to obtain embryonic stem cells in the laboratory but unless they can be safely and efficiently transplanted into the recipient then the whole process is pretty useless! Working on the blood forming haemopoietic stem cells may be relatively easy as these cells may follow the properties of their adult and umbilical counterparts and be able to be transplanted intravenously. Other tissues will not be so easy to transplant and again much time and effort must be put into this area.
Human embryonic stem cells clearly have lots of potential and the current ideas reflect this. As embryologists we must follow this research and the associated debates very closely because in the not too distant future a stem cell transplant will become part of the daily routine of many IVF clinics.
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Reproduced with permission from BioNews, an email and online sources of news, information and comment on assisted reproduction and genetics.
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