NUCLEI NUMBER IN HUMAN EMBRYOS COCULTURED WITH HUMAN AMPULLARY CELLS

A study was undertaken to evaluate the effect on nuclei number in huma n embryos cultured in vitro with primary cell lines of human Fallopian tube epithelium. The development of 203 surplus human embryos, cultur ed in standard culture medium (Earle's balanced salt solution + 15% A5 ) with or without ampullary cells, was observed from day 2 to day 5.5 post-insemination. The expanded blastocysts in both culture conditions were analysed for nuclei numbers per blastocyst. Embryos transferred to co-culture at the 2-cell stage had an average of 120.7 nuclei per b lastocyst, which was significantly higher than the average of 62.9 nuc lei per blastocyst (P = 0.023) for the embryos transferred to co-cultu re at the 4-cell stage. The embryos cultured in the control medium had an average of 42.1 nuclei per blastocyst, which was significantly les s than cocultured embryos (P = 0.04). Severely fragmented embryos (gra des 3 and 4) did not show recovery in co-culture. Our results show tha t when human embryos are transferred to co-cultures before the 4-cell stage, the blastulation rate and the cell number per embryo increase s ignificantly compared to the embryos cultured in standard culture medi um. The possible effect of co-culture on embryonic gene expression is discussed.