Minute changes to the culture environment of mouse pre-implantation embryos affect the health of the conceptus

H19/Igf2 Expression and Methylation of Histone 3 in Mice Chimeric Blastocysts

Background

Currently, the efficient production of chimeric mice and their survival are still challenging. Recent researches have indicated that preimplantation embryo culture media and manipulation lead to abnormal methylation of histone in the H19/Igf2 promotor region and consequently alter their gene expression pattern. This investigation was designed to evaluate the relationship between the methylation state of histone H3 and H19/Igf2 expression in mice chimeric blastocysts.

Methods

Mouse 129/Sv embryonic stem cells (mESCs) expressing the green fluorescent protein (mESCs-GFP) were injected into the perivitelline space of 2.5 days post-coitis (dpc) embryos (C57BL/6) using a micromanipulator. H3K4 and H3K9 methylation, and H19 and Igf2 expression was measured by immunocytochemistry and q-PCR, respectively, in blastocysts.

Results

Histone H3 trimethylation in H3K4 and H3K9 in chimeric blastocysts was significantly less and greater, respectively (p< 0.05), than in controls. H19 expression was significantly less (p< 0.05), while Igf2 expression was less, but not significantly so, in chimeric than in control blastocysts.

Conclusion

Our results showed, that the alteration ofH3K4me3 and H3K9me3 methylation, change H19/Igf2 expression in chimeric blastocysts.

The effect of laser-assisted hatching on the methylation and expression pattern of imprinted gene IGF2/H19 in mouse blastocysts and offspring

PURPOSE

This study aimed to determine the effects of drilling and thinning treatment of laser-assisted hatching on the expression and methylation of imprinted gene IGF2/H19 in embryos and offspring.

METHODS

The prehatching blastocysts with treatment of drilling or thinning, or control prehatching blastocysts, were transplanted in surrogate uteri. The DNA methylation of IGF2/H19 imprinting control region (ICR) and the expression of IGF2 and H19 were respectively evaluated using bisulfite conversion-mediated sequencing and real-time PCR.

RESULTS

The drilling group showed a significant increase in the development rate of hatched blastocysts in comparison with the control and thinning group. DNA methylation level of IGF2/H19 ICR of hatched blastocysts in the thinning group was 27.33% in comparison with the 38.67% and 36% observed in the control and drilling group. The thinning treatment increased the DNA methylation level of IGF2/H19 ICR in the placenta in comparison with the control and drilling group. The drilling and thinning treatment decreased the expression level of H19 mRNA in prehatching and hatched blastocysts as well as placenta, while a significant increase in the expression level of H19 mRNA of offspring was observed in the thinning group. The thinning treatment increased the expression level of IGF2 mRNA of prehatching blastocysts and offspring and a significant decrease in placenta, while the drilling treatment resulted in a significant increase in the expression level of IGF2 mRNA of hatched blastocysts and placenta.

CONCLUSION

These observations suggested that drilling used for hatching of in vitro cultured mouse blastocysts may improve the production of offspring.

Anti-Oxidative Effects of Human Adipose Stem Cell Conditioned Medium with Different Basal Medium during Mouse Embryo In Vitro Culture

Simple Summary

Assisted reproductive techniques, which are used to resolve various infertility problems, have advanced following the emphasis on their use. Embryos produced in vitro rather than in vivo are exposed to greater stress, with the quality of the embryos being affected by the in vitro culture conditions. To reduce oxidative stress and consequent apoptosis of embryos for successful implantation and pregnancy maintenance, the present study evaluated the anti-oxidative effect of human adipose stem cell conditioned medium (ASC-CM) with different basal medium as supplement in in vitro culture (IVC) medium for mouse preimplantation embryo. Treatment of 5% human ASC-CM based on Dulbecco′s modified Eagle′s medium (DMEM-CM) indicated an enhanced development of mouse in vitro fertilized embryo, decreased expression level of indicators for oxidative stress, and apoptosis in blastocysts. To our knowledge, this is the first study to demonstrate that DMEM-CM can be an optimal supplement during IVC to promote in vitro embryo development and the success rate of assisted reproduction with its anti-oxidative and anti-apoptotic effects.

Abstract

The quality of embryos produced by assisted reproductive techniques should be advanced by the improvement of in vitro culture conditions for successful implantation and pregnancy maintenance. We investigated the anti-oxidative effect of human adipose stem cell (ASC) conditioned medium with its optimal basal medium, Dulbecco′s modified Eagle′s medium (DMEM-CM), or keratinocyte serum-free medium (KSFM-CM) as supplements during in vitro culture (IVC) of in vitro fertilized mouse embryo. At first, preimplantation embryo development was evaluated in KSFM-CM and DMEM-CM supplemented cultures at various concentrations. The blastocyst (BL) and hatched BL formation rates were significantly increased in 5% DMEM-CM, while no difference was observed from KSFM-CM. Next, comparing the efficacy of KSFM-CM and DMEM-CM at the same concentration, DMEM-CM enhanced the developmental rate of 16 cells, morula, BL, and hatched BL. The expression level of reactive oxygen species decreased and that of glutathione increased in BL cultured with DMEM-CM, which confirms its anti-oxidative effect. Furthermore, apoptosis in BL cultured with DMEM-CM was reduced compared with that in KSFM-CM. This study demonstrated that the comparative effect of human ASC-CM made of two different basal media during mouse embryo IVC and anti-oxidative effect of 5% DMEM-CM was optimal to improve preimplantation embryo development.

pH: the silent variable significantly impacting meiotic spindle assembly in mouse oocytes

RESEARCH QUESTION

Temperature fluctuation negatively impacts the assembly and function of the meiotic spindle, but does pH have a similar effect?

DESIGN

Polarized light microscopy was used to study the spindle in living mouse oocytes under different pH conditions. Female mice (n = 53) were superovulated, and oocytes collected, denuded and allocated to treatment groups. All experiments were performed at 37°C, and standard bicarbonate-buffered medium was used either pre-equilibrated in 6% CO₂ or unequilibrated (in ambient CO₂). Mean oocyte spindle retardance was measured over time in response to changing pH. Spindles were also assessed to understand whether this effect was reversible, by using a fixed pH in a zwitterionic buffer.

RESULTS

The data show the spindle is impacted by pH fluctuation, with mean retardance significantly higher at pH 7.4-7.5 than at the point of media equilibration (P < 0.001). This effect was found to be reversible; retardance significantly decreased after transition of the oocytes from pH 7.43 or pH 7.53 back to the original pre-equilibration pH of 7.32 (P < 0.05).

CONCLUSIONS

This study has shown that the meiotic spindle in mouse oocytes is highly sensitive to changes in oocyte culture media pH. If comparable in humans, this has significance as to the pH level of culture media currently used in assisted reproductive technology clinics worldwide, and reinforces the requirement for stringent control over extrinsic variables in the IVF laboratory.