Enrichment and detection of fetal erythroid cells from maternal peripheral blood using liquid culture

Isolating fetal cells from maternal blood for prenatal genetic analysis is the least invasive method currently being investigated. In order to enrich these fetal erythroid cells we employed a two-phase liquid culture system that supports the growth and differentiation of erythroid progenitor cells. Mononuclear cells were separated from ten maternal blood samples at 8-14(+3) weeks of gestation and cultured in the first phase. After 4-5 days, the non-adherent cells were harvested and recultured with erythropoietin for another 3-4 days. The mean number of total erythroid cells reached approximately 0.77x10(6)/ml with an average purity of 90.5%. Hb F stain disclosed fetal erythroid cells averaging approximately 5.7%, therefore the mean number of fetal erythroid cells isolated was 0.49x10(5)/ml. Female karyotypes were only observed while counting 5-66 metaphases. However, male DNA (SRY or DYZ1) was detected by PCR in 7/10 cases; in four of these cases and in one SRY-negative pregnancy the 46,XY karyotype was found by amniocentesis performed during the second trimester. This liquid culture system provided an enriched source of fetal cells without the need for more complicated separation or sorting procedures.