AMNION/AMNIOTIC FLUID STEM CELLS

The amniotic fluid itself contains mesenchymal stem cells and the lining of the amniotic cavity- the amniotic epithelial cell layer- also contains stem cells. In mammals, the allantois forms the umbilical cord and the mesodermal components of the fetal placenta.  Gastrulation occurs during the third week of gestation and the process establishes all three germ layers including the ectoderm, mesoderm and the endoderm.  Gastrulation begins on the surface of the epiblast and is responsible for the differentiation and specification of cell fate.   As the embryo and the placenta develop, various stem cell entities become operative.  Amniotic Epithelium (AE) cells are derived from the epiblast during early embryonic life at approximately 8 days after fertilization.  The AE cells therefore are derived before gastrulation which occurs between days 15 to 17.  Gastrulation marks a “tipping point” when cell fate is determined.  Because the amnion and therefore the AE cells differentiate from this epiblast, these cells retain their pluripotentency and these AE cells differentiate into cells from all three germ layers.