Embryonic stem cells are derived from early stage embryos (called blastocysts) that are five to seven days old. In Australia these blastocysts are donated for research with consent from patients who have completed treatment for infertility, and have surplus embryos. The embryos donated and used in research would otherwise be discarded. At this stage of development the blastocyst is a hollow ball of about 150 cells and no bigger than a pinhead. The blastocyst is a unique stage of development, as there are two different types of cells, an outer layer called the trophectoderm, and a small group of approximately 30 cells called the inner cell mass. The inner cell mass is what ultimately becomes the embryo, and the trophectoderm becomes the placenta.

Embryonic stem cells are isolated from the blastocyst when the inner cell mass is removed and cultured in the laboratory. During this process the blastocyst is destroyed.Once the cells have been isolated they can be grown continuously in a laboratory culture dish that contains a nutrient-rich culture medium. As the stem cells divide and spread over the surface of the dish some are removed to populate fresh subcultures to form a stem cell line. Because these cells have the ability to keep dividing (self-renewing), large numbers of embryonic stem cells can be grown in the laboratory and also frozen for future use. As a result, established embryonic stem cell lines can be maintained in laboratories for research, shared between researchers and maybe ultimately used in cell-based therapies.

It has been legal to use human embryos for stem cell research in Australia since 2002 but only where scientists meet strict regulatory requirements such as obtaining a licence for the creation of the human embryonic stem cells.

To learn more about embryonic stem cells watchCreation of human embryonic stem cell linesin our video library.

To learn more about the Australian laws that regulate this area of science watchThe Stem Cell Debateor visitIs stem cell research legal in Australia?

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What are embryonic stem cells or ES cells?