Transcervical recovery of fetal cells from the lower uterine pole: reliability of recovery and histological/immunocytochemical analysis of recovered cell populations

The aim of this work was to isolate, enumerate and attempt the identificati on of fetal cells recovered from the lower uterine pole. Immediately before elective termination of pregnancy at 7-17 weeks gestation, samples were re covered by transcervical flushing of the lower uterine pole (n = 108) or tr anscervical aspiration of mucus from just above the internal os (n = 187), and their contents examined using histological, immunohistochemical and mol ecular techniques. Syncytiotrophoblasts were identified morphologically in 28 out of 89 (31%) and 50 out of 180 (28%) flushings and aspirates respecti vely (mean 29%), Immunocytochemistry with monoclonal antibodies (mAbs) reco gnizing trophoblast or epithelial cell antigens on a smaller number of samp les (n = 69) identified putative placental cells in 13 out of 19 (68%) and 25 out of 50 (50%) bushings and aspirates respectively (mean 55%), These in cluded groups of distinctive cells with a small, round, hyperchromatic nucl eus, strongly reactive with mAbs FLAP, NDOG1 and FT1.41.1. Smaller groups o f larger, amorphous cells, usually containing multiple large, pale staining nuclei, reactive with mAb 340 and to a lesser degree with mAb NDOG5 were a lso observed. Taking cellular morphology and immunophenotype into considera tion, the smaller uninucleate cells were likely to be villous mesenchymal c ells, while the larger cells were possibly degrading villous syncytiotropho blast. There was no significant difference in the frequency of fetal cells obtained by the two recovery methods. Squamous or columnar epithelial cells , labelled strongly with antibodies to cytokeratins or human milk fat globu le protein, were observed in 97% (29 out of 30) of aspirates. The use of ce rvagem in a small number of patients prior to termination of pregnancy did not appear to influence the subsequent recovery of placental cells. Y-speci fic DNA was detected by polymerase chain reaction (PCR) in 13 out of 26 (50 %) flushings and (99 out of 154) 64% aspirates analysed (mean 62%), In-situ hybridization (ISH) revealed Y-specific targets in 40 out of 69 (60%) of a spirates analysed. A comparison of PCR data obtained from transcervical rec overed samples and placental tissues showed a concordance of 80% (76 out of 95), with 10 false positives. Comparing the PCR data from tissues with dat a derived by ISH from 41 aspirates gave a concordance of 90% with two false positives. Although syncytiotrophoblasts were much more likely to be prese nt in samples containing immunoreactive placental cells, the detection rate s of fetal-derived DNA were similar regardless of the morphological and/or immunological presence of placental cells. We conclude that the transcervic al recovery of fetal cells, while promising, requires considerable addition al effort being expended in further research and development, particular in the sampling procedure.