Reproductive technologies and embryology
What are reproductive technologies?
Reproductive technologies are associated with assisting and improving reproduction as well as for therapeutic cloning in humans and animals. Reproductive technologies include:
- Artificial insemination (AI), a process which involves inserting fertile sperm into a female who carries at least one fertile egg.
- In vitro fertilization (IVF), which involves fertilizing a female egg with a sperm in an artificially created environment; zygotes produced from this process are cultured to a very early stage of development and are then either transferred into the mother to continue growth and development, or used for scientific research.
- Pre-implantation genetic diagnosis (PGD) uses one cell from an embryo, or five or six cells from a blastocyst, which are tested for a desirable trait, or for an undesirable trait, such as a defect or disorder.
- Embryo transfer (ET). Embryos can be fertilised and cultured up until very early stages of embryonic differentiation in artificially created environments. In human infertility clinics however, embryos are often transferred earlier to maximize the chances of success for pregnancy.
What is embryology?
Embrology is the study of embryos. It involves research into embryo biology, the embryonic environment and embryo manipulation. Embryology and reproductive technologies work hand in hand to deliver healthy embryos which are produced outside the female reproductive system. Technologies can also be used to generate stem cells that can be used for research into organ production and treatments for disease (pictured right: Day 7 blastocysts after fertilisation of egg and sperm).
Embryology and associated reproductive technologies are often highlighted in the media due to ethically challenging issues.
Advantages
- Artificial insemination (AI) involves collecting semen from valuable bulls and freezing it into vials, which can be shipped anywhere in the world at little expense (pictured top right).
- In vitro fertilization (IVF) brings together male sperm and female oocytes and the controlled fertilization produces embryos whose sex can then be determined (pictured right: obtaining eggs from a cow's ovary).
- For a valuable animal, a specific form of IVF, intracellular sperm injection (ICSI), requires only one sperm. This is significant in humans as well as animals where there may be a low sperm count or where the sperm have low ability to move.
Using pre-implantation genetic diagnosis (PGD) embryos can be selected or deselected for desirable or undesirable traits.
- Embryo transfer technology allows embryos to be transported around the world and to be inserted into a range of mothers.
- Culture of embryos outside the female reproductive system has developed considerably over the last few decades.
Challenges
- In artificial insemination (AI), only the male genetics are used to improve the genetic makeup of offspring.
- Cost - as we progress through the various stages of improving embryo quality, the cost increases very significantly.
- The potential to produce a genetically similar population has to be guarded against.
- The longer embryos spend in culture media in vitro, the more they lose their quality, reducing their viability. Research is continually improving culture media.
Applications in the Dairy CRC
The Dairy CRC uses reproductive technologies including IVF, and in deriving embryonic stem cells in the cow.
Mastitis is an infection of the mammary (udder) tissue in dairy cattle caused by arrange of bacteria. This disease results in reduced milk production, altered milk quality and costs the Australian dairy industry millions of dollars each year. If we can identify genes associated with susceptibility to mastitis, we could look for the allele causing the defect and eliminate these embryos from an embryo population. Similarly if we can identify embryos that are infected with a virus, these would not be used for transfer.
Any process that can improve embryo quality is very important before embarking on the expensive and long term (280 days gestation for cow) transfers to recipient cows.
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