Effect of nicotine on gene expression and developmental competence of bovine oocytes

Abstract

Nicotine affected meiosis during oocyte maturation is associated with poor subsequent embryonic
development. The aim of this study was to analyze the effects of nicotine exposure during in vitro maturation (IVM)
on the outcomes of in vitro fertilization (IVF) and the expression of gene related development of oocytes and embryos.
Immature (germinal vesicle, GV) oocytes were randomly cultured in IVM media containing nicotine at concentrations
of 0.0 (control) 2.5, 5.0, and 10.0 mM. After culturing for 24 h, oocytes were assessed for their maturation rate, subjected
to IVF and mRNA extraction for gene expression analysis using quantitative real time PCR (qRT-PCR). The maturation
rates of oocytes exposed to nicotine at 5.0 (62%) and 10.0 mM (54%) was significantly (P<0.05) lower than oocytes
exposed to nicotine at 2.5 mM (87%) and the control (95%). Following IVF, oocytes exposed to nicotine at 0, 2.5, 5 and
10 mM resulted in similar cleavage rates (96, 91, 91 and 89%, respectively). However, blastocyst rates developed from
oocytes treated with nicotine were lower than the control (11, 14, 12 and 24%, respectively). The expressions of GDF9
and ZAR1 in oocytes treated with nicotine at 5 mM were upregulated significantly (P<0.05) than the control. The
expression of BCL2 and DMNT in oocytes treated with nicotine at 2.5 and 5.0 mM was upregulated significantly
(P<0.05) than the control. The expression of BAX in all nicotine treated groups was comparatively higher than the
control but not statistically different (P>0.05). The present study indicated that nicotine negatively affected oocyte and
blastocyst development in a dose dependent manner and altered the expression levels of genes associated with the
development of oocytes and embryos.