Pluripotent stem cells derived from amniotic fluid and placenta
US researchers have obtained stem cells from the amniotic fluid of pregnant women, which can develop into different cell types. The amniotic fluid stem cells came from the respective fetus.
The researchers from the Wake Forest Institute for Regenerative Medicine in Winston-Salem and the Children's Hospital and Harvard Medical School in Boston examined amniotic fluid samples from 19 pregnant women who had come to the hospital for a prenatal screening of possible genetic defects in their babies. A needle was pushed through the building ceiling into the amniotic sac and some amniotic fluid was removed.
In the amniotic fluid samples, the researchers led by Anthony Atala found a small number of cells that had a very specific stem cell antigen, the c-Kit. This antigen plays a role in the activation of pluripotent cells and therefore serves as a recognition feature of stem cells. About one percent of the cells contained in the amniotic fluid could be identified as stem cells.
In addition to the embryonic markers, the stem cells also contained gene markers that are actually only present in adult stem cells. So the researchers looked at the cells' chromosomes to see if they came from the mother or the foetus. In subjects who were expecting a boy, a Y and an X chromosome were found in the amniotic fluid stem cells: the cells were therefore from the male fetus. However, since they have both embryonic and adult gene markers, the researchers suspect that this is an intermediate stage.
During subsequent cultivation in the test tube, the amniotic fluid stem cells developed into all known cell types of the embryonic germ layer. The researchers were also able to differentiate them into various adult cell types such as neurons or bone-forming cells. Unlike embryonic stem cells, they did not develop tumors.
In order to test the applicability of the amniotic fluid stem cells in brain diseases, for example, the researchers also planted human neurons obtained from them in the brains of sick mice in which a progressive disease had left holes in the brain mass. The human neurons colonized the destroyed areas and formed connections to the surrounding nerve cells.
As early as 2003, a group led by physician Markus Hengstschläger from the Medical University of Vienna announced similar results. At that time, however, the scientists only discovered neuronal stem cells. The fact that there are other pluripotent cells and that they could also be used for therapeutic purposes was only proven with the current study.
In the future, the amniotic fluid stem cells could be obtained as a by-product of amniotic fluid tests. After birth, the mother's placenta could also serve as an additional source of stem cells. The researchers also found the child's stem cells there. The researchers involved now hope that with the new method they have created a way of obtaining a supply of stem cells in an ethically acceptable manner that could be accessed both by the respective child and by other people who would be suitable recipients. (tk)