Immunophenotyping of mitotic cells from long-term cultures of chorionic villi.

Chromosomal mosaicism in chorionic villus samples (CVS) may arise from different sources, such as clonal diversity within the chorionic tissue or contamination with maternal cells. To determine the origin of karyotyped cells, we compared the immunocytochemical features of mitotic cells in CVS long-term cultures with histological sections of their tissue of origin, i.e. chorionic villi. Immunolabelling of intermediate filaments specific for epithelial cells (cytokeratin) and mesenchymal cells (vimentin) established that mitoses yielded from CVS long-term cultures indeed stem from independently growing clones derived from both the epithelial and mesenchymal parts of the chorionic villi. Thus, mosaicism in CVS cultures may reflect true genetic heterogeneity within the biopsy. However, epithelial chorionic cells undergo in vitro metaplasia leading to co-expression of cytokeratins and vimentin. Fetal-specific immune markers (beta-HCG and SP1-glycoprotein) are not reliably expressed in CVS cell culture.