Comparison of three differential mouse blastocyst staining methods

Boric acid supplementation promotes the development of in vitro-produced mouse embryos by related pluripotent and antioxidant genes

Boric acid (BA) is an important mineral for plants, animals and humans that assists metabolic function and has both positive and negative effects on biological systems. The present study aimed to investigate the effects of different concentrations of BA added to the culture media, the quality and in vitro development potential of mouse embryos. Superovulated C57Bl6/6j female mice were sacrificed ∼18 hours after human chorionic gonadotropin (hCG) injection. Single-cell-stage embryos were collected from the oviduct, divided into experiment groups and cultured in embryo medium with supplemented BA+ in 5% CO2 at 37 °C until 96 hours at the blastocyst stage. The blastocyst development rates of 0, 1.62 × 10-1, 1.62 × 10-2, 1.62 × 10-3 and 1.62 × 10-4 µM BA were 51.52%, 73.47%, 77.36% and 81.13%, respectively. The in vitro development rates were significantly higher in the 1.62 × 10-3 (p < 0.05) and 1.62 × 10-4 µM BA groups than in the control group (p < 0.001). These results indicated that low BA doses influenced embryo development by positively affecting in vitro development rates, embryo cell numbers, biochemical parameters and development at the molecular level by pluripotent and antioxidant genes. Therefore, BA seems to play an important role on in vitro embryo development.

Boric Acid Improved Cryopreserved Mouse Embryo Development

Boric acid (BA) is an essential trace element that is required to support the metabolic pathways in plants, humans, and animals. The present study investigates the in vitro development and quality of single-cell mouse embryos in a BA-added culture medium after cryopreservation using the solid-surface vitrification method. For this purpose, the pronuclear-stage embryos derived from superovulated C57Bl/6j mouse strains and the one-cell embryos were then cryopreserved using the solid-surface vitrification (SSV) method. After thawing, the embryos were cultured in a BA-added medium at 37 °C in a 5% CO2 environment until the blastocyst stage. The resulting in vitro development rates of the embryos in the control group, SSV group, and SSV + 1.62 × 10-4 μM BA group were 68.11% (36/59), 40.16% (16/48), and 64.92% (28/48) respectively, indicating that the BA supported the in vitro development of the embryos cryopreserved using the SSV method. Our results suggest that the addition of boric acid to the culture media increased the development rate of the embryos that were vitrified using the SSV method.

A Brief Incubation of Cumulus-Enclosed Mouse Eggs in a Calcium-Free Medium Containing a High Concentration of Calcium-Chelator Markedly Improves Preimplantation Development

The presence of cumulus cells (CCs) surrounding ovulated eggs is beneficial to in vitro fertilization and preimplantation development outcomes in several mammalian species. In the mouse, this contribution has a negligible effect on the fertilization rate; however, it is not yet clear whether it has positive effects on preimplantation development. Here, we compared the rates of in vitro fertilization and preimplantation development of ovulated B6C3F1 CC-enclosed vs. CC-free eggs, the latter obtained either after a 5 min treatment in M2 medium containing hyaluronidase or after 5-25 min in M2 medium supplemented with 34.2 mM EDTA (M2-EDTA). We found that, although the maintenance of CCs around ovulated eggs does not increment their developmental rate to blastocyst, the quality of the latter is significantly enhanced. Most importantly, for the first time, we describe a further quantitative and qualitative improvement, on preimplantation development, when CC-enclosed eggs are isolated from the oviducts in M2-EDTA and left in this medium for a total of 5 min prior to sperm insemination. Altogether, our results establish an important advancement in mouse IVF procedures that would be now interesting to test on other mammalian species.

N-acetylcysteine addition after vitrification improves oocyte mitochondrial polarization status and the quality of embryos derived from vitrified murine oocytes

Background

Vitrification is the safest method to cryopreserve oocytes, however the process alters mitochondrial function resulting from increased reactive oxygen species (ROS) production. Our aim was to alleviate ROS stress in vitrified mice oocytes using N-acetylcysteine (NAC at 1 mM), to improve the oocyte’s developmental competence.

Results

Hence, four experimental groups were compared: fresh oocytes (F-C), vitrified oocytes (V-C), NAC addition prior to oocyte vitrification (V-NAC-Pre) and NAC addition after vitrification (V-NAC-Post). V-NAC-Pre and V-NAC-Post exhibited higher levels of mitochondrial polarization compared to vitrified oocytes (36.5 ± 3.1, 37.7 ± 1.3 and 27.2 ± 2.4 measured as the spatial coefficient of variation/oocyte respectively, mean ± SEM; p < 0.05). However, ROS production increased in vitrified oocytes added with NAC compared to the vitrified control (1124.7 ± 102.1 [V-NAC-Pre] and 1063.2 ± 82.1 [V-NAC-Post] vs. 794.6 ± 164.9 [V-C]; arbitrary fluorescence units/oocyte, mean ± SEM; p < 0.05). ATP significantly decreased in V-NAC-Pre compared to V-NAC-Post oocytes (18.5 ± 6.9 vs. 54.2 ± 4.6 fmol/oocyte respectively, mean ± SEM; p < 0.05), and no differences were observed between V-NAC-Post, F-C and V-C groups. Blastocyst rates derived from F-C oocytes was higher than those derived from V-NAC-Pre (90.7 ± 1.8 vs. 79.1 ± 1.8, respectively, mean % ± SEM,; p < 0.05) but similar to those derived from V-NAC-Post (90.7 ± 1.8, mean % ± SEM, p > 0.05). Total blastomere count of blastocysts derived from V-NAC-Post after in vitro fertilization (IVF) was higher than embryos produced from V-C.

Conclusions

The addition of NAC after vitrification improves the quality of vitrified mature murine oocytes while its addition prior to vitrification is advised against.

Improved development of somatic cell cloned mouse embryos by vitamin C and latrunculin A

Impaired development of embryos produced by somatic cell nuclear transfer (SCNT) is mostly associated with faulty reprogramming of the somatic nucleus to a totipotent state and can be improved by treatment with epigenetic modifiers. Here we report that addition of 100 μM vitamin C (VitC) to embryo culture medium for at least 16 h post-activation significantly increases mouse blastocyst formation and, when combined with the use of latrunculin A (LatA) during micromanipulation and activation procedures, also development to term. In spite of this, no significant effects on pluripotency (OCT4 and NANOG) or nuclear reprogramming markers (H3K14 acetylation, H3K9 methylation and DNA methylation and hydroxymethylation) could be detected. The use of LatA alone significantly improved in vitro development, but not full-term development. On the other hand, the simultaneous treatment of cloned embryos with VitC and the histone deacetylase inhibitor psammaplin A (PsA), in combination with the use of LatA, resulted in cloning efficiencies equivalent to those of VitC or PsA treatments alone, and the effects on pluripotency and nuclear reprogramming markers were less evident than when only the PsA treatment was applied. These results suggest that although both epigenetic modifiers improve cloning efficiencies, possibly through different mechanisms, they do not show an additive effect when combined. Improvement of SCNT efficiency is essential for its applications in reproductive and therapeutic cloning, and identification of molecules which increase this efficiency should facilitate studies on the mechanism of nuclear reprogramming and acquisition of totipotency.