Scientists find potential stem cells in amniotic fluid – a new source?

Research by Austrian geneticists has raised the possibility that stem cells[1] could be isolated from amniotic fluid – the protective ’bath water’ that surrounds the unborn baby.

Geneticist Professor Markus Hengstschläger and his team at the University of Vienna have isolated a subgroup of cells from amniotic fluid that express a protein called Oct-4 – known to be a key marker for human pluripotent stem cells.

Reporting the findings today (Monday 30 June) in Europe’s leading reproductive medicine journal Human Reproduction[2], Professor Hengstschläger stressed that the investigation was at an early stage. A lot more work had to be done to verify the finding, and tests were now under way to establish in which direction the cells could be differentiated. However, preliminary experiments have already provided evidence that they can be differentiated into nerve cells.

If, after extensive research these stem cells do prove to have similar potential to embryonic stem cells, ultimately it could reduce the need to use human embryos as a source, thus easing the tensions in this ethically controversial area.

Professor Hengstschläger believes that his team will know within two years what the amniotic cells are capable of becoming. “We have already presented good evidence in this paper for the existence of stem cells in amniotic fluid and we have evidence for neuronal differentiation. The question for the future will be – what can these cells do, in which directions can they be differentiated? Whether these cells have the same potential as embryonic stem cells is a question that can only be answered by a variety of experiments. However, our gene marker analyses demonstrate that they at least appear to resemble embryonic stem cells.”

Professor Hengstschläger’s group is the first to identify amniotic fluid as a potential source of pluripotent stem cells although others have previously suggested that amniotic fluid cells might be able to make skin.

To find the cells the researchers examined amniotic fluid taken from routine diagnostic amniocentesis on pregnant women. Genetic tests on 11 independent samples revealed Oct-4 mRNA (messenger RNA) in five of the samples. They went on to test for further indications of their potential and identified stem cell factor (a growth factor), vimentin and the enzyme alkaline phosphatase mRNA expression. All three of these molecules are markers for pluripotent stem cells.

“There is no doubt as to the importance of Oct-4 for the maintenance of stem cells,” said Professor Hengstschläger. “Each mammalian pluripotent stem cell line expresses Oct-4, which rapidly disappears when the cells differentiate.”

Further tests on the nucleus confirmed that the correct molecule had been analysed and suggested that the Oct-4 protein expression in the amniotic fluid cells was indeed functional.

Professor Hengstschläger said that the fact that only half the amniotic fluid samples were Oct-4 positive and that only 0.1 to 0.5% of cells within these positive samples expressed the Oct-4 transcription factor indicated that there was a distinct sub-population within the amniotic fluid cell sample with the potential to differentiate, rather than indicating that they had simply found a low general background Oct-4 expression. The cells were also shown to have dividing ability because cyclin A – a crucial protein that drives cell division – was present.

“Even if, in due course, we find that this new source of stem cells only have the ability to differentiate into a specific subset of cell lines, this is still an extremely interesting finding,” he said. “We believe that our findings, together with the recent demonstration that amniotic fluid can be used for tissue engineering, encourages the further investigation of human amniotic fluid as a putative new source of stem cells with high potency.”

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[1] Stem cells: the body’s master cells. They develop a few days after fertilisation. They have the facility to divide indefinitely and develop into many different specialised cells i.e. they differentiate – becoming the cells that make up all our tissues e.g. skin, blood, muscle, glands, nerves…. Stem cells have become one of the most exciting areas of research because of their ability to be cultured in a laboratory and stimulated with chemicals to become any one of the scores of specialist cells in the body. The vision is that they will one day be used to repair damaged organs, rather than using drugs or transplants. Stems cells consist of three types: totipotent (can become any cell in the body or in the placenta), pluripotent (can become any cell in the body except embryonic membranes) and multipotent (can become a limited number of types of cell).

[2] Oct-4-expressing cells in human amniotic fluid: a new source for stem cell research? Human Reproduction. Vol. 18. No 7. Pp 1489-1493.

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