Nicotinamide (NAM), a precursor for nicotinamide adenine dinucleotide (NAD+), is widely used as a supplement during different cells culturing. Although its antioxidative and anti-apoptotic properties, the specific effects on bovine embryo quality and implantation potential remain partly explored. The current study aimed to investigate the impact of NAM on developmental competence and quality of bovine embryos, focusing on cell apoptosis, survival, and trophoblast invasion. NAM was treated during in vitro maturation (IVM) and late-stage embryo culture (IVC3; the morula stage embryo), the cleavage and blastocyst formation rates were evaluated on Days 4 and 8 post-fertilization, respectively. Underlying mechanisms affecting embryo quality and invasion potential were examined in developed blastocysts using RT-qPCR, immunofluorescence, reactive oxygen species (ROS) measurement, TUNEL and trophoblast invasion assays. Results showed that the cleavage and blastocyst formation rates were significantly increased in the NAM-treated group relative to controls (83.62 ± 1.38% vs. 80.08 ± 0.52%, and 37.54 ± 1.15% vs. 28.74 ± 0.70%, respectively). Additionally, the in vitro-developed embryos supplemented with NAM during IVM and IVC3 exhibited lower levels of ROS and mRNA of caspase-3, and higher mRNA levels of the survival genes SOD1 and SOD2. Similarly, the DNA fragmentation rate was lower, and the total cell counts and inner cell mass to trophectoderm (ICM:TE) ratios were higher in embryos supplemented with NAM compared to untreated embryos. Furthermore, the MMP2 and MMP9 protein expression and trophoblast invasion rate of blastocysts treated with NAM were enhanced. These findings highlight the potential role of NAM in improving bovine embryo quality and enhancing trophoblast invasive capacity, thereby suggesting an improved implantation potential.
