Karyotype, growth, and cell cycle analysis of human embryonic palatal mesenchymal cells: relevance to the use of these cells in an in vitro teratogenicity screening assay.

Human embryonic palatal mesenchyme (HEPM) is an established cell line that is presently under investigation as an in vitro prescreening assay used to determine the teratogenic potential of chemicals. We describe here general growth characteristics, karyotype, and cell cycle analysis of these cells. HEPM cells had plating efficiencies of less than 95% and displayed notable contact growth inhibition following an exponential growth phase that lasted for approximately 6 days. These cells had the diploid karyotype of a female human embryo. The chromosomal complement showed no dramatic change between passage 5 and 14. Flow cytofluorometry analysis using bromodeoxyuridine (BrdU) pulse labeling and a direct immunofluorescence anti-BrdU FITC probe revealed that the total cell cycle transit time was approximately 22 hr: the duration of G1 was 12.2 hr, S was 6.1 hr, and G2-M lasted for 3.7 hr. The results indicate that HEPM cells met the criteria regarding karyotype stability that were assumed by the National Toxicology Program of the USA.