Differentiation and properties of amniotic fluid cells
Amniotic fluid cells have been widely used, initially in the assessment of gestational age and Rhesus isoimmunization; more recently in the antenatal diagnosis of chromosomal disorders, inborn errors of metabolism, haemoglobinopathies, some congenital malformations and detection of high risk pregnancy. However, the amniotic fluid cell origin is not yet clear. This study examined the properties of uncultured and cultured amniotic fluid cells, as well as their differentiation through culture. Amniotic fluids were divided into normal and abnormal according to their alpha fetoprotein values (Brock, 1981) and the following cell characteristics were examined: numbers, morphology, viability, adherence, phagocytosis, presence of Fc receptors, non-specific acid esterase, behaviour in vitro by cinemicrography and immunocytochemistry. The heterogeneity of amniotic fluid cells was confirmed and their origin is discussed. The use of the previously neglected uncultured amniotic fluid cells is enhanced. The presence of macrophages in normal (Hoyes, 1968) and abnormal (Sutherland et al., 1973, 1975) amniotic fluids was confirmed. Macrophages were increased in number in amniotic fluids from fetuses with anencephaly but not in those with spina bifida. The macrophages were short lived and incapable of survival and proliferation in culture. The presence of neural cells in amniotic fluids from fetuses with a neural tube defect (Gosden and Brock, 1978a) was also confirmed. The neural cells consisted of neuroblasts which differentiated through culture into neurons; glial cells which seem to dedifferentiate into glioblasts; and microglia. The studies in normal amniotic fluids suggested that the main cell type (AF) of long-term amniotic fluid cell cultures originates from trophoblast (Priest et al., 1979) and that their heterogeneity is due to differentiation in culture from cytotrophoblast into syncytiotrophoblast. The implications of these findings in antenatal diagnosis are discussed.