The majority of<unk><unk>  present in the<unk>  fluid share many characteristics, which suggests they may have a common origin. In 2007, it was confirmed that the<unk>  fluid contains a heterogeneous mixture of multipotent<unk>  after it was demonstrated that they were able to differentiate into<unk>  from all three germ layers but they could not form teratomas following implantation into immunodeficient mice. This characteristic differentiates them from embryonic<unk><unk>  but indicates similarities with adult<unk><unk> . However, foetal<unk><unk>  attained from the<unk>  fluid are more stable and more plastic than their adult counterparts making it easier for them to be reprogrammed to a pluripotent state. A variety of techniques has been developed for the isolation and culturing of<unk> . One of the more common isolation methods involves the removal of<unk>  fluid by amniocentesis. The<unk>  are then extracted from the fluid based on the presence of c-Kit. Several variations of this method exist. There is some debate whether c-Kit is a suitable marker to distinguish<unk>  from other<unk> types because<unk>  lacking c-Kit also display differentiation potential. Culture conditions may also be adjusted to promote the growth of a particular<unk> type. Mesenchymal<unk><unk>  Mesenchymal<unk><unk>  (MSCs) are highly abundant in the<unk>  fluid and several techniques have been described for their isolation. They usually involve the removal of<unk>  fluid by amniocentesis and their distinction from other<unk>  may be based on their morphology or other characteristics. Human leukocyte antigen testing has been utilised to confirm that the MSCs<unk>  from the fetus and not from the mother. Originally it was proposed that the MSCs were discarded from the embryo at the end of their life cycle but since the<unk>  remained viable in the<unk>  fluid and were able to proliferate in culture this hypothesis was overturned. However, it remains unclear whether the<unk>  originate from the fetus itself, the placenta or possibly the inner<unk> mass of the blastocyst. Comparison of<unk>  fluid-derived MSCs to bone-marrow-derived ones showed that the former has a higher expansion potential in culture. However, the cultured<unk>  fluid-derived MSCs have a similar phenotype to both adult bone-marrow-derived MSCs and MSCs originating from second trimester fetal tissue. In animals, the MSCs seem to have a unique immunological profile which was observed after their isolation and in vitro culturing. Embryonic-like<unk><unk>  As opposed to mesenchymal<unk><unk> , embryonic-like<unk><unk>  are not abundant in the<unk>  fluid, making up less than 1% of amniocentesis samples. Embryonic-like<unk><unk>  were originally identified using markers common to embryonic<unk><unk>  such as nuclear Oct4, CD34, vimentin, alkaline phosphatase,<unk> <unk> factor and c-Kit. However, these markers were not necessarily concomitantly expressed. In addition, all of these markers can occur on their own or in some combination in other types of<unk> . The pluripotency of these embryonic-like<unk><unk>  remains to be fully established. Although those<unk>  which expressed the markers were able to differentiate into muscle, adipogenic, osteogenic, nephrogenic, neural and endothelial<unk> , this did not necessarily occur from a homogenous population of undifferentiated<unk> . Evidence in favour of their embryonic<unk> <unk> nature is the<unk> ’ ability to produce clones.
Amniotic stem cells
Neural stem cell
Embryoid body
Progenitor cell
Extravillous trophoblast
Syncytiotrophoblast
Cytotrophoblast
Hemangioblast