Stem cell research and cloning
In December 2002 the Federal Government passed 2 laws which regulate the research that Australian scientists can do using human embryos.
The Prohibition of Human Cloning Act 2002 and the Research Involving Human Embryos Act 2002 were the result of hours of parliamentary debate, however, public opinion remains polarised over the laws and stem cell research.
The laws were reviewed 3 years later by the Lockhart Committee, and this review was tabled in Federal Parliament in December 2005. This review made a number of recommendations, including continuing the ban on reproductive cloning and the creation of hybrid embryos. It did, however, recommend lifting the ban on human embryonic cloning for research, clinical and training purposes, including deriving stem cell lines for possible therapeutic purposes, provided such embryos were not implanted into the womb and were not allowed to develop for more than 14 days.
Prohibition of Human Cloning for Reproduction and the Regulation of Human Embryo Research Amendment Act 2006 now covers stem cell research and cloning in Australia. States and territories have their own legislation regulating use of embryos and seek to be consistent with Commonwealth legislation.
The use of human stem cell lines in research must also comply with National Health and Medical Research Council (NH&MRC) guidelines and the Therapeutic Goods Administration (TGA) is developing a national regulatory framework for human tissues and biological therapies
To understand what these laws mean for us and for medical research, we need to understand a little about stem cells and the human embryo.
What are stem cells?
Stem cells are the precursor (starter) cells to all kinds of different cells of the body. While most adult cells, such as skin, nerve and muscle cells, still contain the genetic code necessary to form different types of cells they are, in fact, unable to do so. When these cells divide, they only give rise to the same type of cells. Stem cells retain the capacity to produce offspring that can change (differentiate) into a variety of different cell types. For example, bone marrow stem cells give rise to red blood cells, white blood cells and platelets (a kind of blood cell that is involved in clotting).
There are many different types of stem cells in the adult body, which give rise to different types of specialised cells — skin, nerves, muscle, etc. They are important for organ growth, development and repair. Unless they have a particular disorder, everybody has these different types of stem cells in their body.
Scientists have managed to extract some types of stem cells from the body and grow them in culture in the laboratory. Stem cells can divide indefinitely in culture and can keep producing specific cells, such as red blood cells, as offspring. This is known as a stem cell line.
A stem cell line that has particular characteristics can be used in the laboratory to test whether new drugs work or to study how diseases arise.
How can stem cells be extracted?
Stem cells can be extracted from embryos, from children and from adults. Embryonic stem cells can only be harvested from early human embryos. The embryos come from in-vitro fertilisation (IVF) clinics and are generally left over from infertility treatments.
People arguing against embryonic stem cell research say that other methods of harvesting stem cell lines where embryos aren’t destroyed can be just as effective at producing stem cells, or at least should be fully explored as an option first. These other methods include harvesting stem cells from cord blood taken from the umbilical cords of newborns and from bone marrow and other adult tissue. Stem cells extracted from umbilical cord blood are still adult stem cells.
Stem cells and the embryo
When sperm fertilises a human egg, the resulting cell has the potential to grow into a complete human being. It is known as ‘totipotent’ because its potential is total. After fertilisation, as it continues its journey down the fallopian tube to the uterus, the cell is dividing to form a ball of cells. These cells start to differentiate and become specialised a few days after fertilisation. Before they start differentiating, though, each of the cells contains all the genetic code needed to grow into a fetus, therefore they are all totipotent at this point.
Blastocyst
When the cells reach the uterus they start to differentiate. A sac of fluid appears inside the ball of cells and the ball splits into an outer shell of cells and a cluster of cells to one side. This hollow sphere of cells is called a blastocyst.
The outer layer of cells will go on to form the placenta. The inner cluster of cells goes on to form the fetus. It is the inner cluster of cells that we are interested in. These cells in the inner cluster contain the genetic code to be able to make many types of human cells. They are known as pluripotent. However, they are not enough on their own to form an embryo. They can’t give rise to the cells of the placenta and other tissues needed to support the embryo.
Embryonic stem cells
These pluripotent cells from the inner cluster are the focus of much of the argument over stem cell research. The potential for their use in medical science is great, however, to extract these so-called embryonic stem cells the embryo has to be destroyed, hence the moral dilemma.
How embryonic stem cells might advance medical science
The pluripotent cells are capable of using their genetic code to propagate many types of human cells. Cell lines of heart, nerve or other cells could be created to replace damaged ones, for example in heart attack patients or people with Parkinson’s or Alzheimer’s disease.
Embryonic stem cells could also be used in research to further our understanding of the human development process or to test new drugs, before they were tested in animals or humans.
Therapeutic cloning
Therapeutic cloning is the creation of an embryo by cloning techniques, known as somatic cell nuclear transfer, for the purpose of extracting stem cells from the embryo. Because it is cloned, the embryo is an identical genetic match to a person, which means that stem cells from the embryo could then be used in transplant procedures or for treatments of that person, without fear of tissue rejection which is a common problem of transplant procedures. To extract the stem cells, though, the embryo must be destroyed.
What research is allowed in Australia?
Research is allowed on left-over embryos from assisted reproductive technology (ART), i.e. IVF programmes, as well as embryos created specifically for research via somatic cell nuclear transfer (therapeutic cloning). There are many thousands of frozen embryos at present in Australia, but the vast majority are intended to be used to achieve a pregnancy. Very few ART embryos have been declared excess to requirements.
Researchers have to apply for a licence from the National Health and Medical Research Council (NHMRC) to do the research, and it is carefully regulated within an ethical framework. It is permitted to use the embryos to derive embryonic stem cells. Part of the framework is that written permission must be given by the woman for whom the embryo was created and her partner (if relevant), so scientists cannot use your embryos for research unless you give them written permission.
The Prohibition of Human Cloning Act 2002 banned human cloning in any way, shape or form. The Amendment passed in December 2006 allows some previously prohibited practices, such as creating embryos for the purpose of therapeutic cloning, that is to harvest stem cells tailor-made to an individual, then to destroy the embryo.
The situation around the world
In February 2002, the UK House of Lords gave the go-ahead for the Human Fertilisation and Embryology Authority to issue licences to researchers so that they can create human embryo clones for stem cell research. It is hoped that this therapeutic cloning will provide ways to make genetically matched new body tissues and cells for people with diseases such as Parkinson’s or diabetes.
In the USA, on March 9, 2009, President Obama issued Executive Order 13505 – Removing Barriers to Responsible Scientific Research Involving Human Stem Cells. This changes the way National Institutes of Health (NIH) can support and conduct human stem cell research and revokes the 2001 Bush presidential statement limiting federal funding for such research.
The new guidelines (effective from July 2009) remove limitations on scientific enquiry, expand NIH support for exploration of human stem cell research and enhance US scientists' important new discoveries and new treatments. There are currently over 20 countries around the world engaged in stem cell research and legislation surrounding this research changes rapidly.
Future
Scientists are excited about the potential of stem cell research. Bone marrow stem cells are already routinely used to treat diseases such as leukaemia. It is hoped that stem cells will be useful in a range of other diseases such as diabetes, Parkinson's disease and Alzheimer's disease. It is also hoped that they may eventually be used to repair damaged nerves after spinal cord injury and damaged heart muscle after heart attack, as well as in many other clinical situations. The growing of entire new organs for transplant is a theoretical, but very distant possibility.
| Stem cells: glossary of terms |
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|---|---|
| Term | Definition |
| Stem cell | Precursor cell. The ‘offspring’ of this cell can change into other cell types. For example, there are stem cells in our bone marrow. They divide, eventually to form red blood cells, white blood cells and platelets. This is called differentiation. |
| Embryonic stem cell (ESC) | Embryonic stem cells are extracted from live embryos at about 3-4 days after fertilisation. They come from the inner cell mass. These cells can develop into any cell type in the body. |
| Totipotent | With the ability to mature into all cell types, including the embryo and the tissues necessary to nurture the embryo and for fetal development. |
| Pluripotent | With the ability to mature into many cell types in the body, e.g. into blood stem cells and skin stem cells. |
| Multipotent | More specialised stem cells that can give rise to a certain type of cell, e.g. blood stem cells give rise to different blood cells; skin stem cells give rise to the different types of skin cells. |
| Cloning embryos | Researchers take an egg and remove the genetic material from it (the nucleus). They they fuse it with a somatic cell (one that isn't an egg or sperm cell). The egg cell and the somatic cell can be from the same species or from different ones. The cell that results can multiply and can grow into an entire animal. This is how Dolly the sheep was cloned. Dolly was produced by transferring the genetic material from a sheep cell into an unfertilised sheep egg which had had its genetic material removed. |
| Therapeutic cloning | Also called somatic cell nuclear transfer. This is the creation of embryos by cloning for the sole purpose of harvesting stem cells from the embryo. The stem cells are then differentiated into healthy body cells to replace diseased or dead cells in a person. In the process of harvesting the stem cells, the embryo must be destroyed. |
Last Reviewed: 17 July 2009
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