Characterization of the biophysical properties of human erythroblasts as a preliminary step to the isolation of fetal erythroblasts from maternal peripheral blood for non invasive prenatal genetic investigation

BACKGROUND AND OBJECTIVE: Fetal erythroblasts in maternal circulation represent a valuable source of fetal cell material which can be obtained with non-invasive procedures that do not endanger the fetus. Physical separation techniques have been invaluable in the isolation and characterization of different cells. There are basically two principles that have been used most successfully: separation according to density and separation according to size. In order to determine whether physical separation procedures are capable of purifying human erythroblasts, the biophysical characteristics of these cells were determined. METHODS: Bone marrow particles were obtained from formal adults and peripheral blood buffy coats from blood banks. A single cell suspension was initially fractionated by buoyant density gradient centrifugation. Fractions enriched in erythroblasts were pooled and further processed by velocity sedimentation in order to take advantage of the differences in size of erythroblasts and other cells. RESULTS: Density distribution curves were drawn after density gradient centrifugation for the different cell types present in the starting cell samples. Separation of the erythroblast-enriched density fractions by velocity sedimentation was successful and a highly purified population of erythroblasts was obtained. Cell size distribution of the different cell types was determined. INTERPRETATION AND CONCLUSIONS: This initial study defines the biophysical properties (size and density) of human erythroblasts in bone marrow and peripheral blood and is a necessary preliminary step in setting up the optimal procedure for the isolation of fetal erythroblasts from maternal peripheral blood in sufficient amounts and purity for prenatal non-invasive genetic investigation.