Oxidative Stress Alters the Profile of Transcription Factors Related to Early Development on In Vitro Produced Embryos

Abstract

High oxygen levels during in vitro culture (IVC) can induce oxidative stress through accumulation of reactive oxygen species (ROS), negatively affecting embryo development. This study evaluated the effect of different O2 tensions during IVC on bovine blastocyst development and transcriptional status, considering transcription factors that play an essential role during early embryo development. For this purpose, embryos were produced in vitro by conventional protocols and cultured in two different oxygen tensions, physiological (5%) and atmospheric (20%). Expanded blastocysts were subjected to transcript quantitation analysis by RT-qPCR with Biomark™ HD System (Fluidigm, US), using 67 TaqMan assays specific for Bos taurus. Differences were observed in genes related to oxidation-reduction processes, DNA-dependent transcription factors, and factors related to important functional pathways for embryo development. Blastocyst rate was higher in the 5% O2 group and the number of cells was assessed, with the 5% O2 group having a higher number of cells. ROS concentration was evaluated, with a higher ROS presence in the 20% O2 group. Taken together, these results allow us to conclude that IVC of embryos at atmospheric O2 tension affects the expression of important transcription factors involved in multiple cell biology pathways that can affect embryo development, quality, and viability.

Sexual dimorphic expression and release of transcription factors in bovine embryos exposed to oxidative stress

“…Accordingly, the maturation and fertilization were done at high oxygen tension in the current study. Furthermore, here we showed that irrespective of the sex of embryo, those embryos cultured under 5% oxygen level showed higher development rate of blastocyst than those under 20% oxygen level, as it has been reported before (Amin et al, ; Leite et al, ). Differences in metabolism (Gómez et al, ) and genetics (Bermejo‐Alvarez et al, ) between male and female bovine embryo could contribute to skewness in sex ratio of the resulted embryos (Oliveira et al, ; Xu, Yadav, King, & Betteridge, ).…”

“…The suboptimal culture conditions of the in vitro production system are partly responsible for the reduction in number and quality of blastocysts (Farin & Farin, ; Gad et al, ). In addition to the culture media, the higher oxygen level in in vitro system is responsible for contributing to the suboptimal environment (Amin et al, ; Kelley & Gardner, ; Leite et al, ). However, previous evidence indicated that there was no significant difference observed in terms of embryo development between maturation followed by fertilization at high oxygen tension and maturation at low oxygen followed by fertilization at high oxygen level, but a dramatic effect was observed in case of fertilization at low oxygen level (Bermejo‐Alvarez, Lonergan, Rizos, & Gutiérrez‐Adan, ).…”

“…Early embryogenesis involves various morphological, cellular, and biochemical changes related to genome activity (Stanton, Macgregor, & Green, ), which could be orchestrated by several transcription factors (TFs). TFs are involved in several biological functions such as embryo development, apoptosis, differentiation, and stress response (Leite et al, ). The exposure of embryos to the in vitro culture conditions is known to alter an array of TFs involved in cell death, lipid metabolism, cellular growth, proliferation, and oxidative stress (OS) response (Gad et al, ; Leite et al, ).…”

“…TFs are involved in several biological functions such as embryo development, apoptosis, differentiation, and stress response (Leite et al, ). The exposure of embryos to the in vitro culture conditions is known to alter an array of TFs involved in cell death, lipid metabolism, cellular growth, proliferation, and oxidative stress (OS) response (Gad et al, ; Leite et al, ). OS is triggered by an imbalance between reactive oxygen species (ROS) and its scavenger of antioxidant molecules (Martindale & Holbrook, ), due to culture media, temperature, pH, and oxygen tension (Cagnone & Sirard, ; Wale & Gardner, ).…”

“…OS is triggered by an imbalance between reactive oxygen species (ROS) and its scavenger of antioxidant molecules (Martindale & Holbrook, ), due to culture media, temperature, pH, and oxygen tension (Cagnone & Sirard, ; Wale & Gardner, ). For instance, the oxygen levels in oviduct and uterus of most mammalian species (1.5–8.7%) are less than half of atmospheric oxygen level (20%; Fischer & Bavister, ), which is widely used in In vitro fertilization (IVF) laboratories and consequently lead to elevation of ROS (Amin et al, ; Leite et al, ; Yoon et al, ). Excess accumulation of ROS damages cellular bioactive molecules such as DNA, protein, and lipid (Martindale & Holbrook, ), subsequently compromising the mitochondrial integrity and activity (Amin et al, ; Kadenbach, Arnold, Lee, & Hüttemann, ) as well as cell number (Amin et al, ; Kelley & Gardner, ; Leite et al, ), resulting in abnormal embryonic development or apoptosis (Amin et al, ; Kadenbach et al, ; Leite et al, ).…”