Morphological differentiation of cytotrophoblasts cultured in Medium 199 and in keratinocyte growth medium

In culture, cytotrophoblast cells differentiate biochemically as well as morphologically into syncytiotrophoblast-like structures. Morphological and biochemical differentiation can be affected by the composition of the culture medium. The aim of this study was to analyze the morphological differentiation (syncytium formation) of cytotrophoblasts cultured in Medium 199 (M199) and keratinocyte growth medium (KGM). Term human cytotrophoblast cells were cultured in either M199 or KGM with daily refreshment of the media. Both media induced biochemical differentiation, as monitored by measuring hCG secretion. Syncytium formation was visualized by immunocytochemical staining of desmosomes (cell membranes). Cytotrophoblasts rapidly formed aggregates; however, single cells were seen throughout culture. Though the aggregates developed into syncytia, approximately 15% of the nuclei were still found in cell aggregates at the end of the culture period (4 days). The final percentage of nuclei in syncytia (60-70%) did not differ between the culture media used. Syncytium formation occurred more rapidly in KGM medium. Approximately 50% of the nuclei were found in syncytia after 40 and 50 h in KGM and M199, respectively. The number of nuclei per syncytium was slightly higher in M199, but the average surface area of the syncytia was larger in KGM cultured cells (162-132 mm2). These differences did not reach significance. We conclude that there is no major difference in morphological differentiation between cytotrophoblast cells in KGM or M199. Moreover, both media sustain equal rates of hCG secretion.