Somatic cell nuclear transfer, also called "therapeutic cloning" is an exciting scientific and medical pursuit that promises great benefit to the community.
What is somatic cell nuclear transfer?
Human cells have 46 chromosomes (23 pairs), except the germ cells (eggs and sperm), which have just 23 single chromosomes. In normal reproduction, when an egg is fertilised by a sperm, their two sets of 23 chromosomes
combine to give the resulting embryo a full complement.
Somatic cell nuclear transfer (SCNT) involves removing the 23-chromosome cell nucleus from a human egg and replacing it with the 46-chromosome cell nucleus from a normal body cell. (In our jargon, we call the body cell a somatic cell. The process is therefore called Somatic Cell Nuclear Transfer or SCNT.)
The reconstructed egg (which we call an SCNT embryo) contains the full 46 chromosomes and is in principle capable of developing into an SCNT blastocyst without the need for fertilisation by sperm.
Sydney IVF hopes to find a standard, repeatable process for producing these SCNT embryos and then deriving a line of SCNT embryonic stem cells from them.
No one has achieved this yet with humans. On the other hand, Sydney IVF is very experienced with the second step: deriving stem cell lines from donated IVF embryos.
Why are we trying to do this?
If we can achieve it, the SCNT procedure will produce embryonic stem cells that are a perfect match for the provider of the somatic cell. This may pave the way towards three major advances...
- Understanding disease. By using somatic cells from a donor who carries a particular genetic disease, we will be able to create disease specific stem cells that carry the gene for the disease. Researchers studying the effects of disease at a cellular level will have virtually unlimited quantities of ‘diseased’ cells of uniform quality to study.
- Developing drug treatments for rare serious diseases. Scientists developing new drug therapies for the disease would test their treatments on these diseased human cells, making their research more relevant and effective than trials using animals and less risky than conducting early-stage clinical trials in people.
- Using stem cells directly for treatment. The proposed treatment of diseases such as Parkinson’s disease, diabetes and muscular dystrophy, or repairing tissue damage after accidents such as major burns and spinal cord injuries, may benefit from stem cells injected into a patient. SCNT would allow a patient’s own stem cells to be used for the treatment rather than stem cells from an unrelated and possibly incompatible cell donor. The chance of the body rejecting SCNT-derived stem cells should be almost negligible. These treatments are still a long way in the future, but successful SCNT could be an important step and the crucial advance to bring stem cell therapy to reality.
Clinically, the use of IVF with therapeutic cloning will enable a young person (especially and obviously a young woman) with a life threatening disease such as acute myeloid leukaemia, particularly if she has no sibling to act as bone marrow donor, to “treat herself” with our help by cloning one of her cumulus cells in one of her eggs to generate haemopoietic stem cells and thus overcome her affliction. This is some time off, but it is very much within our clinical spectrum: help people with difficulties to conceive; help women who are prone to miscarry not to miscarry; and ensure optimal health for the children as we help people form their families, as those children get to the age of having their own children.