Primordial germ cell-derived embryonic germ cells of the mouse - In vitro model for cytotoxicity studies with chemical mutagens

Different screening methods to detect the toxic effects of xenobiotics using cells from vertebrates and invertebrates in cytotoxicity and viability assays have been developed, but up to now appropriate in vitro methods with mammalian germ cells have not been available. In the present study the primordial germ (PG) cell-derived permanent embryonic germ (EG) cell line EG-1 was used as in vitro model in toxicity studies with chemical mutagens. EG-1 cells and embryonic stem cells of line D3 were comparatively investigated for their cell survival in response to N-ethyl-N-nitiosourea (ENU), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and mitomycin C (MMC) and the results compared with those obtained for undifferentiated embryonic carcinoma cells of line P19 and differentiated epithelioid EPI-7 cells. As a prerequisite for in vitro toxicity and viability studies the cultivation conditions for EG-1 and D3 cells in the absence of a feeder layer were improved by a conditioned medium, increasing the plating efficiency from 0.08% to 17.5% and from 21.1% to 25.1% for EG-1 and D3 cells, respectively. The resulting mean generation time (MGT) of 16.9 hr for EG-1 cells was identical to the generation time of PG cells in vivo, and was not significantly different from the MGT of D3 (15.6 hr) and EPI-7 (13.7 hr) cells, but significantly longer than the MGT of P19 cells (9.3 hr). Calculations of the concentrations resulting in vitro in a 50% decrease in cell survival demonstrated that EG-1 cells were more sensitive to the toxic effects of ENU, MNNG and MMC than D3 and P19 cells and, with the exception of MNNG, also more sensitive than EPI-7 cells. It is proposed that EG cells are used as a model system to screen for toxic effects of teratogenic and embryotoxic chemical agents in vitro.