Optimization of embryo culture conditions for increasing efficiency of cloning in buffalo (Bubalus bubalis) and generation of transgenic embryos via cloning

Astaxanthin enhances the development of bovine cloned embryos by inhibiting apoptosis and improving DNA methylation reprogramming of pluripotency genes

Low cloning efficiency limits the wide application of somatic cell nuclear transfer technology. Apoptosis and incomplete DNA methylation reprogramming of pluripotency genes are considered as the main causes for low cloning efficiency. Astaxanthin (AST), a powerfully antioxidative and antiapoptotic carotenoid, is recently shown to improve the development of early embryos, however, the potential role of AST during the development of cloned embryos remains unclear. This study displayed that treating cloned embryos with AST significantly increased the blastocyst rate and total blastocyst cell number in a concentration dependent manner, and also alleviated the damage of H2O2 to the development of cloned embryos. In addition, compared with the control group, AST significantly reduced the apoptotic cell number and rate in cloned blastocysts, and the significantly upregulated expression of anti-apoptotic gene Bcl2l1 and antioxidative genes (Sod1 and Gpx4) and downregulated transcription of pro-apoptotic genes (Bax, P53 and Caspase3) were observed in the AST group. Moreover, AST treatment facilitated DNA demethylation of pluripotency genes (Pou5f1, Nanog and Sox2), in accompany with the improved transcription levels of DNA methylation reprogramming genes (Tet1, Tet3, Dnmt1, Dnmt3a and Dnmt3b) in cloned embryos, and then, the significantly upregulated expression levels of embryo development related genes including Pou5f1, Nanog, Sox2 and Cdx2 were observed in comparison with the control group. In conclusion, these results revealed that astaxanthin enhanced the developmental potential of bovine cloned embryos by inhibiting apoptosis and improving DNA methylation reprogramming of pluripotency genes, and provided a promising approach to improve cloning efficiency.

Role of tPA in Corticosterone-Induced Apoptosis of Mouse Mural Granulosa and Oviductal Epithelial Cells

Although studies indicate that female stress-increased secretion of glucocorticoids impairs oocyte competence and embryo development, by inducing apoptosis of ovarian and oviductal cells, respectively, the mechanisms by which glucocorticoids induce apoptosis of ovarian and oviductal cells are largely unclear. Tissue plasminogen activator (tPA) has been involved in apoptosis of different cell types. However, while some studies indicate that tPA is proapoptotic, others demonstrate its antiapoptotic effects. This study has explored the role and action mechanisms of tPA in corticosterone-induced apoptosis of mouse mural granulosa cells (MGCs) and oviductal epithelial cells (OECs). The results demonstrate that culture with corticosterone significantly increased apoptosis, while decreasing levels of tPA (Plat) mRNA and tPA protein in both MGCs and OECs. Culture with tPA ameliorated corticosterone-induced apoptosis of MGCs and OECs. Furthermore, while tPA protected MGCs from corticosterone-induced apoptosis by interacting with low-density lipoprotein receptor-related protein 1 (LRP1), it protected OECs from the apoptosis by acting on Annexin 2 (ANXA2). In conclusion, tPA is antiapoptotic in both MGCs and OECs, and it protects MGCs and OECs from corticosterone-induced apoptosis by interacting with LRP1 and ANXA2, respectively, suggesting that tPA may use different receptors to inhibit apoptosis in different cell types.

In vitro embryo production in buffaloes: from the laboratory to the farm

Transvaginal follicular aspiration technique together with in vitro embryo production are the biotechnological alternatives currently available to support genetic improvement breeding programs in buffalo species. However, aspects related to animal management, lack of knowledge of the metabolic needs and biochemical peculiarities of gametes and embryos, as well as the reproductive physiology characteristics have hampered progress in the results. Despite the low availability of good quality oocytes collected after OPU in donors as a physiological characteristic of buffalo species, high rates of oocyte maturation, modest embryo cleavage, blastocyst production and pregnancy rates after transvaginal embryo transfer in recipients could be obtained in buffalo in vitro embryo production programs. The results of implementing an in vitro embryo production program in buffaloes in the northern region of Pará state, Brazil, and results published by other groups demonstrate the feasibility of implementing this biotechnology in the routine of breeding programs. Nevertheless, in order to achieve better and consistent results, it is necessary to deepen the knowledge on the peculiarities of reproductive biology in this specie. Selection of donor animals based on ovarian size and ovarian follicular reserve and on the rate of blastocyst production is presented as an effective alternative to increase the efficiency of the in vitro embryo production technique applied to the buffalo species.

Effect of growth factors on oocyte maturation and allocations of inner cell mass and trophectoderm cells of cloned bovine embryos

This study was conducted to determine the additive effects of exogenous growth factors during in vitro oocyte maturation (IVM) and the sequential culture of nuclear transfer (NT) embryos. Oocyte maturation and culture of reconstructed embryos derived from bovine granulosa cells were performed in culture medium supplemented with either epidermal growth factor (EGF) alone or a combination of EGF with insulin-like growth factor-I (IGF-I). The maturation rates of oocytes matured in the presence of EGF or the EGF + IGF-I combination were significantly higher than those of oocytes matured in the presence of only fetal calf serum (FCS) (P 0.05). IGF-I alone or in combination with EGF in sequential embryo culture medium significantly increased the ratio of inner cell mass (ICM) to total blastocyst cells (P < 0.05). Our results showed that the addition of growth factors to IVM and sequential culture media of cloned bovine embryos increased the ICM without changing the total cell number. These unknown and uncontrolled effects of growth factors can alter the allocation of ICM and trophectoderm cells (TE) in NT embryos. A decrease in TE cell numbers could be a reason for developmental abnormalities in embryos in the cloning system.

Vitamin C supplementation enhances compact morulae formation but reduces the hatching blastocyst rate of bovine somatic cell nuclear transfer embryos

Vitamin C, an antioxidant that reduces reactive oxygen species (ROS) in cells, is capable of significantly improving the developmental competence of porcine and mouse somatic cell nuclear transfer (SCNT) embryos, both in vitro and in vivo. In the present study, the effects of vitamin C on the developmental competence of bovine SCNT embryos were investigated. The results indicated that vitamin C (40 μg/mL) positively affected the scavenging of intracellular ROS, cleavage rate at 24 h (76.67 vs. 68.26%, p<0.05), compact morulae formation (60.83 vs. 51.30%, p<0.05), and the blastomere apoptosis index (3.70 ± 1.41 vs. 4.43% ± 1.65, p<0.05) of bovine SCNT embryos. However, vitamin C supplementation did not significantly affect the blastocyst formation rate and proportion of inner cell mass over total cells per blastocyst on day 7. Moreover, vitamin C supplementation obviously impaired the total cell numbers per blastocyst (97.20 ± 11.35 vs. 88.57 ± 10.43, p<0.05) on day 7 and the hatching blastocysts formation rate on day 9 (26.51 vs. 50.65%, p<0.05) compared with that of the untreated group. Vitamin C supplementation preferentially improved the viability of bovine SCNT embryos prior to the blastocyst stage, but did not enhance the formation and quality of blastocysts in vitro. In conclusion, the effect of vitamin C on the development of bovine SCNT embryos is complex, and vitamin C is not a suitable antioxidant chemical for the in vitro culture of bovine SCNT embryos.

Improvement of cloned embryos development by co-culturing with parthenotes: a possible role of exosomes/microvesicles for embryos paracrine communication

It is well known that embryos cultured in a group can create a microenvironment through secretion of autocrine and paracrine factors that can support and improve the embryos' development when compared to the embryos cultured individually. In this study, we used a co-culture system for paracrine communication between different kinds of embryos. The results showed that co-culture of porcine parthenogenetic (PA) embryos significantly improved the in vitro development of cloned (nuclear transfer, NT) embryos. To reveal the possible mechanism of communication between the two groups, we isolated exosomes/microvesicles (EXs/MVs) from the PA embryos conditioned medium (PA-CM) through differential centrifugation and identified them through transmission electron microscope and immunoflourescence against exosomal/membrane marker CD9. Furthermore, these EXs/MVs were found to contain mRNA of pluripotency genes (Oct4, Sox2, Klf4, c-Myc, and Nanog), and the PKH67-labeled EXs/MVs could be internalized by the NT embryos. The current study demonstrates that cloned embryos' developmental competence can be improved through co-culturing with PA embryos and revealed, for the first time, that in vitro-produced embryos can secrete EXs/MVs as a possible communication tool within their microenvironment. Moreover, it provides a new paradigm for embryo-to-embryo communication in vitro.