'Human Embryo' - A biological definition
The NHMRC Embryo Research Licensing Committee (NHMRC Licensing Committee) developed this discussion paper in response to a request from the Council of the NHMRC for a definition of 'human embryo' from a purely biological standpoint. The paper was presented to Council in December 2005 and members recommended that the report be released as a discussion paper to provide an opportunity for a wider audience to comment on the biological definition of 'human embryo'. The definition proposed in this paper was subsequently adopted by the Australian Parliament in the Prohibition of Human Cloning for Reproduction and Regulation of Human Embryo Research Amendment Act 2006 to replace the previously used definition.
An edited version of the discussion paper was published in Human Reproduction.
Findlay, JK, Gear, ML, Illingworth, PJ, Junk, SM, Kay G, Mackerras AH, Pope A, Rothenfluh, HS, Wilton L. Human Embryo: a biological definition. Human Reproduction (2007) 22:905-911.
What is an excess assisted reproductive technology (ART) embryo?
A human embryo that:
(a) was created by ART, for use in the ART treatment of a woman; and
(b) is excess to the needs of:
(i) the woman for whom it was created; and
(ii) her spouse (if any) at the time that the embryo was created.
For the purposes of paragraph (b), a human embryo is excess to the needs of the persons mentioned in that paragraph at a particular time if:
(a) each such person has given written authority for the use of the embryo for a purpose other than a purpose relating to the ART treatment of the woman concerned, and the authority is in force at the time; or
(b) each such person has determined in writing that the embryo is excess to their needs, and the determination is in force at that time.
What are stem cells?
- Stem cells are ‘unspecialised’ cells that have the unique potential to develop into ‘specialised’ cell types in the body (for example blood cells, muscle cells or nerve cells). This can be either for growth and development, or for replenishment and repair.
- Stem cells occur at all stages of human development, from embryo to adult but their versatility and numbers tend to decrease with age.
- Given the right conditions in the body or the laboratory, stem cells (unlike muscle cells, nerve cells and or blood cells) can replicate themselves many times over.
- When a stem cell replicates, the resulting cells can either remain as stem cells or can become specialised cells.
What are embryonic stem cells?
- Embryonic stem cells, as their name suggests, are derived from the early embryo. They have the potential to develop into all cell types in the body.
- In Australia, human embryonic stem cells are derived from human embryos that are excess to the needs of patients undergoing assisted reproductive technology (ART) treatment programs and have been donated to research by the couple for whom they were created. They are not derived from eggs fertilised in a woman’s body.
- Embryonic stem cells can also be derived from embryos created by somatic cell nuclear transfer (see 'Cloning' section below).
What is cloning?
- "Cloning" is an umbrella term traditionally used by scientists to describe different processes for duplicating biological material.
- The possibility of human cloning arose when Scottish scientists at the Roslin Institute created the much-celebrated sheep 'Dolly' (Nature 385, 810-13, 1997)
- Reproductive cloning is banned in Australia under the Prohibition of Human Cloning for Reproduction Act 2002. Click here for more information.
- Therapeutic cloning, also known as somatic cell nuclear transfer (SCNT) is permitted in Australia under a licence issued by the NHMRC Embryo Research Licensing Committee.
- SCNT was the technique used to create the first cloned mammal, 'Dolly' the sheep. SCNT involves isolating a somatic cell from an adult body, often a skin cell, and transferring the nucleus from that cell to an egg from which the nucleus has been removed. This new cell is then stimulated to begin embryonic growth.
- The first human embryonic stem cell lines derived from SCNT research were announced in May 2013 by Mitalipov and coworkers from Oregon Health and Science University.
Two other groups reported successful stem cell line derivations in 2014 – Yamada, M et al Human oocytes reprogram adult somatic nuclei of a type 1 diabetic to diploid pluripotent stem cells. Nature (2014) 510: 533-6; Chung YG et al Human somatic cell nuclear transfer using adult cells Cell Stem Cell (2014) 14: 777-780.
What is parthenogenesis?
- Parthenogenesis is a process where an unfertilised egg is induced to divide and develop as though it had been fertilised.
- Parthenogenetic embryos cannot be used for reproduction as they will not develop past an early stage of pregnancy under section 20 of the Prohibition of Human Cloning for Reproduction Act 2002.
- Creation of embryos by parthenogenesis and their use for research is permitted in Australia under a licence issued by the NHMRC Embryo Research Licensing Committee.
- Embryonic stem cell lines derived from a parthenogenetic embryo are genetically matched to the woman who provided the egg.