Enhanced development of mouse single blastomeres into blastocysts via the simultaneous inhibition of TGF-β and ERK pathways in microdroplet culture

Developmental capacity is unevenly distributed among single blastomeres of 2-cell and 4-cell stage mouse embryos

During preimplantation development, mammalian embryo cells (blastomeres) cleave, gradually losing their potencies and differentiating into three primary cell lineages: epiblast (EPI), trophectoderm (TE), and primitive endoderm (PE). The exact moment at which cells begin to vary in their potency for multilineage differentiation still remains unknown. We sought to answer the question of whether single cells isolated from 2- and 4-cell embryos differ in their ability to generate the progenitors and cells of blastocyst lineages. We revealed that twins were often able to develop into blastocysts containing inner cell masses (ICMs) with PE and EPI cells. Despite their capacity to create a blastocyst, the twins differed in their ability to produce EPI, PE, and TE cell lineages. In contrast, quadruplets rarely formed normal blastocysts, but instead developed into blastocysts with ICMs composed of only one cell lineage or completely devoid of an ICM altogether. We also showed that quadruplets have unequal capacities to differentiate into TE, PE, and EPI lineages. These findings could explain the difficulty of creating monozygotic twins and quadruplets from 2- and 4-cell stage mouse embryos.

Schisanhenol improves early porcine embryo development by regulating the phosphorylation level of MAPK

Schisanhenol (SAL), a biphenyl cyclooctene-type lignin compound which can be extracted and isolated from many plants of the Schisandra family, exhibits a variety of biological activities including anti chronic cough, night sweating, thirst, diabetes, and obesity. However, its effects on the female reproductive system are unclear. Previous studies showed that SAL had potential antioxidant activity in heart, liver, and brain. Therefore, we hypothesized that SAL could improve porcine early development by reducing oxidative stress. The purpose of this study was to investigate the effects of SAL on preimplantation porcine embryos and the potential mechanisms. In this study, we analyzed the effects of SAL on embryo quality, reactive oxygen species (ROS) accumulation, mitochondrial function, cell proliferation and apoptosis, and the activation of MAPK pathway. The results showed that 10 μM SAL significantly increased the blastocyst formation rate, proliferation ability, and mitochondrial activity while reducing ROS accumulation and apoptosis level. During this process, the phosphorylation levels of ERK1/2, JNK1/2/3, and p38 were decreased. In summary, 10 μM SAL improves porcine preimplantation embryo development by reducing ROS accumulation.

Totipotency of mouse zygotes extends to single blastomeres of embryos at the four-cell stage

In multicellular organisms, oocytes and sperm undergo fusion during fertilization and the resulting zygote gives rise to a new individual. The ability of zygotes to produce a fully formed individual from a single cell when placed in a supportive environment is known as totipotency. Given that totipotent cells are the source of all multicellular organisms, a better understanding of totipotency may have a wide-ranging impact on biology. The precise delineation of totipotent cells in mammals has remained elusive, however, although zygotes and single blastomeres of embryos at the two-cell stage have been thought to be the only totipotent cells in mice. We now show that a single blastomere of two- or four-cell mouse embryos can give rise to a fertile adult when placed in a uterus, even though blastomere isolation disturbs the transcriptome of derived embryos. Single blastomeres isolated from embryos at the eight-cell or morula stages and cultured in vitro manifested pronounced defects in the formation of epiblast and primitive endoderm by the inner cell mass and in the development of blastocysts, respectively. Our results thus indicate that totipotency of mouse zygotes extends to single blastomeres of embryos at the four-cell stage.

Suppression of TGF-β and ERK Signaling Pathways as a New Strategy to Provide Rodent and Non-Rodent Pluripotent Stem Cells

Stem cells are unspecialized cells and excellent model in developmental biology and a promising approach to the treatment of disease and injury. In the last 30 years, pluripotent embryonic stem (ES) cells were established from murine and primate sources, and display indefinite replicative potential and the ability to differentiate to all three embryonic germ layers. Despite large efforts in many aspects of rodent and non-rodent pluripotent stem cell culture, a number of diverse challenges remain. Natural and synthetic small molecules (SMs) strategy has the potential to overcome these hurdles. Small molecules are typically fast and reversible that target specific signaling pathways, epigenetic processes and other cellular processes. Inhibition of the transforming growth factor-β (TGF-β/Smad) and fibroblast growth factor 4 (FGF4)/ERK signaling pathways by SB431542 and PD0325901 small molecules, respectively, known as R2i, enhances the efficiency of mouse, rat, and chicken pluripotent stem cells passaging from different genetic backgrounds. Therefore, the application of SM inhibitors of TGF-β and ERK1/2 with leukemia inhibitory factor (LIF) allows the cultivation of pluripotent stem cells in a chemically defined condition. In this review, we discuss recently emerging evidence that dual inhibition of TGF-β and FGF signaling pathways plays an important role in regulating pluripotency in both rodent and non-rodent pluripotent stem cells.