Microsatellite analysis provides efficient confirmation of fetal trophoblast isolation from maternal circulation

Fetal trophoblasts can be found in maternal circulation from an early stage of pregnancy and thus provide a potential source of DNA for non-invasive p renatal diagnosis. We have developed a two-step method for trophoblast isol ation between the 8th and 12th week of pregnancy. Blood was sampled from 14 women undergoing termination of pregnancy or spontaneous abortion. Immunom agnetic beads precoated with HLA class I and II, and with anti-cytokeratin- 18 monoclonal antibodies. were used to remove CD8+ and other maternal cells , and to select for fetal trophoblasts. respectively. Microsatellite analys is was performed on DNA extracted from the isolated. maternal, paternal and placental cells after PCR amplification. Recovery of the trophoblasts was confirmed in 13/14 cases (93%) by the identification of an identical micros atellite pattern for fetal and placental cells. Further evidence was the pr esence of heterozygous alleles of both maternal and paternal origin. The co rrect prediction of gender in all five male fetuses was an additional confi rmation of trophoblast recovery. We conclude that trophoblasts can be effec tively isolated from maternal blood in the first trimester. and by using po lymorphic microsatellite markers to confirm sample purity, this method has potential future application in prenatal diagnosis. Copyright (C) 2001 John Wiley & Sons. Ltd.