Identification of hematopoietic progenitor cells in human amniotic fluid before the 12th week of gestation.

Due to technical difficulties in performing amniocentesis before the 12th week of pregnancy, very little is known about the components of human amniotic fluid before that time. Amniocentesis was performed between the 7th-11th week of gestation in 25 informed and consenting patients, who had to undergo therapeutic interruption of pregnancy. The cells from the amniotic fluid were stained, counted on a hemocytometer, and checked for vitality. The origin of these cells was determined from cellular cultures the intracellular content of the hemoglobin and the chloroacetate esterase content of the hemoglobin and the chloroacetate esterase contents were also studied. Taking advantage of the "in vitro" adhesive properties of these cells to the bone marrow stromal feeder layer, we obtained clonal growth of an erythroid nature from 18 out of 33 samples. At the 17th week of gestation, an increased number of cells and a decrease in their vitality was found. Between the 7th and 12th week, the cellular composition of the fluid was totally different from that found later in the pregnancy. Small nucleated, round cells were identified as hematopoietic progenitor cells. At the beginning of the 11th week, a cellular population, typically used to perform prenatal diagnosis of chromosomal abnormalities from the 14th week of pregnancy appeared. Since hematopoietic progenitor cells were found in the amniotic fluid before the 12th week of gestation, these cells most probably come from the hematopoietic cells of the yolk sac through the thin membrane of the yolk sac at this time.