US scientists have dramatically improved the in vitro maturation (IVM) of pig egg cells, offering the possibility that similar successes could be achieved in humans.
By investigating the conditions in which egg cells were growing in the lab, researchers were able to double both the number of viable pig embryos and the size of litters birthed.
Professor R. Michael Roberts of the University of Missouri said: 'It was a serendipitous discovery, really. Generally, there are multiple steps to producing viable embryos … however, it’s costly and sometimes yields very little return. We were seeking a way to do that more efficiently and stumbled upon a method that may have implications in human fertility clinics as well.'
IVM involves the removal of immature eggs, which are then matured in the laboratory prior to fertilisation and implantation. This is different to IVF (in vitro fertilisation), where eggs are allowed to mature in the body before being removed for fertilisation.
The research, published in the journal PNAS, investigated ways to improve the number of live piglets born from eggs which had undergone IVM and IVF. Cells in the lab need to be grown in a growth medium, which contains not only nutrients, but also small proteins known as cytokines, which affect cell growth and behaviour. Using the correct cytokines in a growth medium helps to mimic the environment the cells would be in inside the body, and can be vital in keeping cells in good condition.
By adding three specific cytokines, FGF2, LIF and IGF1, to the egg cells' medium, named FLI medium, the researchers were able to double the number of viable embryos suitable for implantation, and when these embryos were used they gave double the litter size of piglets born. This, in effect, quadrupled the total efficiency of the procedure.
The scientists, from the University of Missouri, do not work on human fertility, but on cattle and pig breeding as well as making animal models of human disease, where efficient IVM and IVF is also key to success. The researchers hope the FLI medium may be effective in human IVF.