A New Methodology of Fetal Stem Cell Isolation,Purification,and Expansion: Preliminary Results for Noninvasive Prenatal Diagnosis

We developed a combined methodological approach to enrich and to proliferate in vitro fetal CD34⁺ stem progenitor cells. Using a magnetic cell-sorting technique, CD34⁺ cells from pregnant women at the early-second trimester were isolated and enriched and compared to those isolated from blood of nonpregnant women. The number and frequency of CD34⁺ cells were significantly higher (p< 0.001) in the pregnant women. Unenriched peripheral blood mononuclear cells (PBMC) and enriched CD34⁺ cells were cultured in a methylcellulose system to evaluate the cloning potential of progenitor cells. After culture, the numbers of burst-forming units erythroid/colony-forming units erythroid (BFU-E/CFU-E) and colony-forming units granulocyte-macrophage (CFU-GM) colonies were increased by 33 and 16 times, respectively. Finally, to distinguish between fetal and maternal cells, four cases of cultured cells were hybridized with specific probes for X and Y chromosomes and two cases with a specific probe for chromosome 21. In normal pregnancies, we identified a high number of male fetal cells and an elevated fetal/maternal ratio. When we analyzed blood samples from pregnancies with trisomic fetuses, we scored a high ratio of trisomic cells respect to maternal cells that was significantly different from the ratio of pregnancies with normal fetuses. Our results demonstrate fetal progenitor cells may be cultured and detected successfully with an appropriate combined methodological approach, which may significantly increase the feasibility of noninvasive prenatal diagnosis.