• What are Stem Cells?

• Types of Stem Cells
• Embryonic Stem Cells
• Embryonic Germ Cells
• Cord Blood Stem Cells
• Adult Stem Cells
• What is the Potential?

• Research in Australia
• Stem Cell Fact Sheets
• FAQs
• Glossary
• Links
• Patient Information

Embryonic Stem Cells

Embryonic stem cells hold the blueprint of the entire human or animal. These cells, throughout the process of development will replicate and generate every cell type of the body. These cells are considered to be pluripotent – the ability to create any cell type necessary for the development of all of the tissues and organs of the organism.

Human embryonic stem cells are derived from human embryos that are 4 to 7 days old. At this stage of development the embryo is a hollow ball of about 200 to 250 cells, no bigger than a pinhead, and is called a blastocyst. Within the blastocyst is a small group of 30 to 34 cells, called the inner cell mass. The remaining cells in the blastocyst become the fetal membranes and placenta. The inner mass cells are able to develop into any type of cell in our body that is they are pluripotent. They make up all the cells and tissue of the adult organism.

Once the inner mass cells are harvested, they can be used to create pluripotent stem cell ‘lines’ – cell cultures that can be grown indefinitely in the laboratory.

Embryonic stem cells are taken from embryos that come from eggs fertilised in an IVF (in vitro fertilisation) clinic. Spare embryos that are not required for implantation are used. They are donated for research purposes only with informed consent from the donors. They are not derived from eggs fertilised within a woman’s body as it is illegal in Australia to conduct any type of research on embryos that are conceived naturally. Embryos cannot be specifically created for research purposes.

Embryonic stem cells can become all cell types of the body because they are pluripotent, making them attractive for developing different tissues for cell-based therapies. They are not, however, capable of developing into a whole new organism because they cannot from the placenta and implant the womb and they cannot assemble into a whole organism as they do not have an inbuilt body plan.

Neural Progenitor Cells JPG, Click to view enlargment

Large numbers of embryonic stem cells can be grown in the laboratory relatively easily. Embryonic stem cell lines are sometimes referred to as immortal, due to their ability to keep dividing (self-renew) over many generations. Therefore established cell lines can be maintained in laboratories for further research and for production
of cells for cell-based therapies.

Embryonic stem cells may have great potential in cell-based therapies, but issues regarding their safety must first be determined. Differentiated stem cell populations are heterogenous (a mixture of stem cell types). It is not yet known how these heterogenous populations of embryonic stem cell will behave inside the body. Scientists are concerned that these differentiated embryonic stem cells will divide uncontrollably once transplanted. Such uncontrolled growth may generate tumours, as occurs in experimental animals. However, homogenous (pure populations) of differentiated embryonic stem cells do not produce tumours.

Another issue with the use of embryonic stem cells in regenerative medicine is that they may trigger rejection by the patient’s immune system. A number of alternatives are being investigated to produce patient specific embryonic stem cells.

There are a range of opinions about human embryonic stem cell research in the community. The overwhelming issue for most people opposed to embryonic stem cell research is that obtaining inner mass cells inevitably leads to the destruction of the embryo. For those that view a fertilised egg as a human life this is most distressing, others consider the blastocyst nothing more than a ball of cells with the potential to become a human. Debate on this issue is essential.

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