An intracytoplasmic injection of deionized bovine serum albumin immediately after somatic cell nuclear transfer enhances full-term development of cloned mouse embryos.

In mouse somatic cell nuclear transfer (SCNT), polyvinylpyrrolidone (PVP) is typically included in the nuclear donor injection medium. However, the cytotoxicity of PVP, which is injected into the cytoplasm of oocytes, has recently become a cause of concern. In the present study, we determined whether bovine serum albumin deionized with an ion-exchange resin treatment (d-BSA) was applicable to the nuclear donor injection medium in SCNT as an alternative to PVP. The results obtained showed that d-BSA introduced into the cytoplasm of an enucleated oocyte together with a donor nucleus significantly enhanced the rate of in vitro development of cloned embryos to the blastocyst stage compared with that of a conventional nuclear injection with PVP in SCNT. We also defined the enhancing effects of d-BSA on the blastocyst formation rate when d-BSA was injected into the cytoplasm of oocytes reconstructed using the fusion method with a hemagglutinating virus of Japan envelope before oocyte activation. Furthermore, immunofluorescence experiments revealed that the injected d-BSA increased the acetylation levels of histone H3 lysine 9 and histone H4 lysine 12 in cloned pronuclear (PN) and 2-cell embryos. The injection of d-BSA before oocyte activation also increased the production of cloned mouse offspring. These results suggested that intracytoplasmic injection of d-BSA into SCNT oocytes before oocyte activation was beneficial for enhancing the in vitro and in vivo development of mouse cloned embryos through epigenetic modifications to nuclear reprogramming.

Infertility in murine acute Trypanosoma cruzi infection is associated with inhibition of pre-implantation embryo development.

We previously showed that Trypanosoma cruzi acute infection induced infertility in a great proportion of female mice, which resulted from a defect taking place before implantation. In this study, we have analyzed every step of reproduction from mating to implantation to identify the most sensitive event. Our results show that mating, ovulation, fertilization, and first division of the zygote of infected mice take place normally compared with uninfected mice, indicating that the defect occurred after the two-cell stage. In vivo development of two-cell embryos to the blastocyst stage was indeed dramatically delayed; some embryos even arrested their development before having reached the eight-cell stage while others degenerated. The effect was less pronounced when embryos were allowed to develop in vitro, indicating that the infectious context of the mother plays a role in maintaining growth retardation. The delay of embryonic development was associated with insufficient divisions of the blastomeres and led to abnormal blastocyst outgrowth that may explain implantation failure. Inhibition of cell division was correlated with the maternal parasitemia. This work clearly shows that T. cruzi infection dramatically impedes embryonic development, offering a model for further in vivo studies of embryotrophic factors produced by the oviduct of infected females.

Observations on the fertilization and development of preimplantation bovine embryos in vitro in the presence of Tritrichomonas foetus.

Tritrichomonas foetus, a world-wide distributed parasitic protozoan is a cause of infertility and abortion. There is no documented information on the susceptibility of bovine embryos to the parasite. To determine the effect of T. foetus on fertilization and embryonic development of preimplantation bovine embryos, we added approximately 10(4)/ml or 10(6)/ml T. foetus (Belfast strain) to sperm cells and oocytes prior to in vitro fertilization (IVF) or to presumptive zygotes 24 h post-fertilization. Light and scanning electron microscopy (SEM) revealed that exposure of oocytes or embryos at any stage of development to T. foetus caused rapid adhesion of the trichomonads to the embryonic intact zona pellucida (ZP) and to trophoblastic cells of hatched blastocysts. Treatment of contaminated embryos with 0.25% trypsin for 3 min did not render them free from T. foetus. Motile parasites were not observed after 18 h incubation in IVF medium, or after 72 h in synthetic oviductal fluid (SOF) embryo culture medium. The percentages of cleaved zygotes, blastocysts and hatched embryos resulting from culture of experimental and uninfected control groups of embryos were not different (P > 0.05). Tritrichomonas foetus was not detected in embryonic cells of ZP-intact or hatched embryos when examined by transmission electron microscopy (TEM). In conclusion, T. foetus has no detrimental effect on the fertilization and development of IVF embryos and the potential risk of transmission of trichomonosis is unlikely, due to the limited survival of the parasite in IVF culture conditions.