Nicotine induces multinuclear formation and causes aberrant embryonic development in bovine

The present study was designed to investigate the effects of nicotine on development of bovine embryos derived from parthenogenetic activation (PA) and in vitro fertilization (IVF). Nicotine caused disfigured secondary meiotic spindle structures and affected embryonic development in a dose-dependent manner. Concentrations at 0.01-0.5 mM resulted in cleavage and blastocyst rates similar to the controls for both PA and IVF embryos. Nicotine at 2.0 and 4.0 mM significantly decreased the cleavage rates and none of the embryos developed beyond the 16-cell stage. Nicotine might disrupt the polymerization of microfilaments leading to impaired chromosome alignment or segregation, and induce the formation of polynuclei with a variety of abnormal nuclear structures such as 2-6 nuclei, 2-4 metaphase plates, 2-4 sets of anaphase/telophase plates, and the co-existence of polynuclei and 2-4 sets of anaphase/telophase plates. Nicotine adversely affected blastocyst chromosomal composition. Fifty-six to 70% of the IVF blastocysts and 71-88% of the PA blastocysts were polyploid and/or mixoploid after culture in 0.2-1.0 mM nicotine-containing media, which were higher (P < 0.05 or P < 0.01) than the controls. Cell numbers of the nicotine-cultured blastocysts were significantly lower than the control. In conclusion, nicotine induced disfigured spindles and irregular chromosome alignment and possibly impaired cytokinesis, which lead to decreased quality of the yielded blastocysts.