Stem cells from an adult mouse have been used to grow a structure resembling a mouse embryo in vitro for the first time.

The ability to study the early stages of embryo development outside the womb may one day help explain why a significant number of human pregnancies fail. This breakthrough in developmental research originated from the same team at University of Cambridge which recently developed a technique that allows human embryos to develop in the lab up to the legal limit of 14 days in the UK.

'We are very optimistic that this will allow us to study key events of this critical stage of human development without actually having to work on (IVF) embryos,'said lead researcher Professor Magdalena Zernicka-Goetzof the University of Cambridge.

The development of a fertilised egg into a fetus is a complex and poorly understood process of self-assembly and intricate cell-to-cell interaction. In a few days a small ball of undifferentiated cells develops into a blastocyst consisting of three different types of embryonic stem cell. Previous attempts to grow embryos using only one kind of stem cell proved unsuccessful because the cells would not assemble into their correct positions.

The researchers placed both placental andembryonic stem cellsinto a three-dimensional scaffold and discovered that within 96 hoursthe cells had begun to communicate, forming two distinct clusters of cells at each end and a cavity in the middle.

'We knew that interactions between the different types of stem cell are important for development, but the striking thing that our new work illustrates is that this is a real partnership these cells truly guide each other,' said Professor Zernicka-Goetz.

The scientists' goal was not to grow mice outside of the womb, but to open a new window on embryonic development just prior to implantation the so-called 'black box' of embryonic development,later than human embryos can be studiedin vitrobut earlier than ultrasound imaging can be used to view the embryo in the womb. About two-thirds of pregnancies are thought to fail during this stage, but because it is so difficult to study, the reasons are poorly understood.

Professor Robin Lovell-Badge of The Crick Institute, who was not involved in the research,lauded the findings as 'permitting study of events that normally take place within the uterus and are therefore difficult to observe, but in this case with an essentially unlimited supply of starting material'.

If used in human embryology, this methodology could make scientists less dependent on fertilised eggs;using artificial embryos could speed up research and potentially sidestep some ethical concerns.

Some critics fear that the technique could be used irresponsibly however. Dr David King, director of Human Genetics Alert,told the Telegraph: 'What concerns me about the possibility of artificial embryos is that this may become a route to creating GM or even cloned babies.'

The research was published in the journal Science.

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Artificial mouse embryo created out of stem cells - BioNews