Early cleavage of handmade cloned buffalo (Bubalus bubalis) embryos is an indicator of their developmental competence and quality

Blastulation time measured with time-lapse system can predict in vitro viability of bovine blastocysts

The objective of this study was to evaluate the time of blastulation monitored by time-lapse technology to predict in vitro viability of bovine blastocysts. This technology can be a powerful tool for bovine embryos selection with higher implantation capacity and competence. Also, in humans an early blastulation is associated with higher quality and pregnancy rate. Cumulus oocyte complexes (COCs) were matured for 20 to 22 h and then fertilized by co-incubation of COCs and spermatozoa (10,000 sperm per oocyte) for 18 h. Presumptive zygotes were placed individually in microwells, in droplets of commercial culture medium. The Primo Vision TL system (EVO+; Vitrolife) captured digital images of developing embryos every 15 minutes. The time frame from IVF to the start of blastulation (tSB) and to blastocyst development (tB) was recorded. After day 7.5, the blastocysts were in vitro culture for 48 h until day 9.5 after IVF to evaluate post hatching development. In vitro viability was evaluated at day 9.5: those with a diameter greater than 200 μm and a total cell count greater than 180 were classified as viable (value 1), while the rest were classified as non in vitro viable (value 0). The area under the ROC curve (AUC) was estimated to determine the predictive power of in vitro viability through blastulation time. In addition, binary logistic regression analysis was used to generate a mathematical model with morphokinetic variables that allow the best prediction of in vitro viability. In 13 sessions, the blastocyst production rate was 46.2% (96/208). The cut-off time to discriminate early or late blastulation was 149.8 h. The post-hatching development of the embryos with early blastulation was 63.3% (31/49), being statistically superior (p = 0.001) than the late blastulation group 14.9% (7/47). Likewise, the time of blastulation showed an accuracy of 90.8% (p < 0.001) in predicting in vitro viability of bovine blastocysts. In conclusion, the selection of blastocysts based on blastulation time (< 155 h) and blastocyst diameter measured on day 7.5 after IVF (> 180 μm) maximizes the in vitro viability.

Production of Water Buffalo SCNT Embryos by Handmade Cloning

Cloning by somatic cell nuclear transfer (SCNT) involves the transfer of a somatic nucleus into an enucleated oocyte followed by chemical activation and embryo culture. Further, handmade cloning (HMC) is a simple and efficient SCNT method for large-scale embryo production. HMC does not require micromanipulators for oocyte enucleation and reconstruction since these steps are carried out using a sharp blade controlled by hand under a stereomicroscope. In this chapter, we review the status of HMC in the water buffalo (Bubalus bubalis) and further describe a protocol for the production of buffalo-cloned embryos by HMC and assays to estimate their quality.

RNA-Seq Reveals the Underlying Molecular Mechanism of First Cleavage Time Affecting Porcine Embryo Development

The selection and evaluation of high-quality embryos are the key factors affecting in vitro embryo development and pregnancy outcome. The timing of first embryonic cleavage has been considered a positive indicator of the in vitro developmental potential of embryos, while the underlying molecular mechanism is still not fully understood. In this study, the embryos generated by parthenogenetic activation (PA) or in vitro fertilization (IVF) were monitored and recorded every 2 h and divided into two groups (early cleavage or late cleavage) based on the cleavage rate and blastocyst formation data. RNA sequencing was used to analyze the gene expression pattern of the embryos. We identified 667 and 71 different expression genes (DEGs) in early cleavage and late cleavage porcine PA and IVF embryos, respectively. Further Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that the DEGs are mainly enriched in pathways concerning the proteasome, DNA repair, cell cycle arrest, autophagy, and apoptosis, suggesting that severe endoplasmic reticulum stress (ERS) and DNA damage may be the key factors that led to the low development potential of late cleavage embryos. This study provides a theoretical basis for the following application and offers important information about the understanding of the timely manner of porcine embryo development.

Effects of Trichostatin A on the Timing of the First Cleavage and In Vitro Developmental Potential of Bovine Somatic Cell Nuclear Transfer Embryos

This study examined the relationship between the timing of the first cleavage and in vitro development of bovine somatic cell nuclear transfer (SCNT) embryos treated with trichostatin A (TSA). SCNT embryos were visually assessed at 22, 26, and 48 hours after activation. Each embryo with two or more distinct blastomeres was transferred into a microwell and cultured until day 7. Irrespective of TSA treatment, approximately half of the cleaved embryos were observed at 22 hours, and a significantly higher blastocyst formation rate was shown in the SCNT embryos cleaved at 22 hours than those cleaved at ≥26 hours. The blastocyst formation rate of TSA-treated embryos cleaved at 22 hours (80%) was slightly higher than that of the control embryos (70%). In addition, interferon-τ (IFN-τ) expression was significantly lower in control SCNT embryos and late-cleaving (>26 hours) TSA-treated embryos than in in vitro fertilized (IVF) embryos. However, a significant difference was not observed between TSA-treated SCNT embryos cleaved at 22 and 26 hours, and IVF embryos. These results suggest that TSA treatment has no influence on the timing of the first cleavage of SCNT embryos; however, it slightly improves the blastocyst formation rate and the expression level of IFN-τ in early-cleaving embryos.

Developmental dynamics of cloned Mexican bighorn sheep embryos using morphological quality standards

The developmental dynamics of cloned Mexican bighorn sheep (Ovis canadensis mexicana) embryos were evaluated based on morphological quality standards. Categories determined by standards were correlated with the embryonic development stage, number of nuclei and viability. The results showed no differences in the blastocyst rate between the experimental (cloned Mexican bighorn sheep embryos) and control (parthenogenetic domestic sheep embryos) groups (p > .05), while type IV fragmentation was higher in clones (p < .05). The standards allowed for the identification of embryos that divided at least once or fragmented after 24 hr of culture. The highest percentage of morulae appeared at 96 hr, the final stages of development: nonsegmented, blocked, fragmented and blastocysts appeared at 192 hr. Embryonic quality decreased over time, making 96 hr the ideal time point to predict the final morphological quality of embryos. Nuclear staining of the morulae and blastocysts showed that higher embryo quality was associated with a higher percentage of normal and viable blastomeres. The evaluated criteria allowed for descriptions of the dynamics, stage and quality of cloned Mexican bighorn sheep embryos with a high degree of reliability. In addition, developmental anomalies, including fragmentation, multinucleation and blocking, were identified.

Improvement of in vitro and early in utero porcine clone development after somatic donor cells are cultured under hypoxia

Genetically engineered pigs serve as excellent biomedical and agricultural models. To date, the most reliable way to generate genetically engineered pigs is via somatic cell nuclear transfer (SCNT), however, the efficiency of cloning in pigs is low (1-3%). Somatic cells such as fibroblasts frequently used in nuclear transfer utilize the tricarboxylic acid cycle and mitochondrial oxidative phosphorylation for efficient energy production. The metabolism of somatic cells contrasts with cells within the early embryo, which predominately use glycolysis. We hypothesized that fibroblast cells could become blastomere-like if mitochondrial oxidative phosphorylation was inhibited by hypoxia and that this would result in improved in vitro embryonic development after SCNT. In a previous study, we demonstrated that fibroblasts cultured under hypoxic conditions had changes in gene expression consistent with increased glycolytic/gluconeogenic metabolism. The goal of this pilot study was to determine if subsequent in vitro embryo development is impacted by cloning porcine embryonic fibroblasts cultured in hypoxia. Here we demonstrate that in vitro measures such as early cleavage, blastocyst development, and blastocyst cell number are improved (4.4%, 5.5%, and 17.6 cells, respectively) when donor cells are cultured in hypoxia before nuclear transfer. Survival probability was increased in clones from hypoxic cultured donors compared to controls (8.5 vs. 4.0 ± 0.2). These results suggest that the clones from donor cells cultured in hypoxia are more developmentally competent and this may be due to improved nuclear reprogramming during somatic cell nuclear transfer.

Pharmacologic treatment of donor cells induced to have a Warburg effect-like metabolism does not alter embryonic development in vitro or survival during early gestation when used in somatic cell nuclear transfer in pigs

Somatic cell nuclear transfer is a valuable technique for the generation of genetically engineered animals, however, the efficiency of cloning in mammalian species is low (1-3%). Differentiated somatic cells commonly used in nuclear transfer utilize the tricarboxylic acid cycle and cellular respiration for energy production. Comparatively the metabolism of somatic cells contrasts that of the cells within the early embryos which predominately use glycolysis. Early embryos (prior to implantation) are evidenced to exhibit characteristics of a Warburg Effect (WE)-like metabolism. We hypothesized that pharmacologically driven fibroblast cells can become more blastomere-like and result in improved in vitro embryonic development after SCNT. The goals were to determine if subsequent in vitro embryo development is impacted by (1) cloning pharmacologically treated donor cells pushed to have a WE-like metabolism or (2) culturing non-treated donor clones with pharmaceuticals used to push a WE-like metabolism. Additionally, we investigated early gestational survival of the donor-treated clone embryos. Here we demonstrate that in vitro development of clones is not hindered by pharmacologically treating either the donor cells or the embryos themselves with CPI, PS48, or the combination of these drugs. Furthermore, these experiments demonstrate that early embryos (or at least in vitro produced embryos) have a low proportion of mitochondria which have high membrane potential and treatment with these pharmaceuticals does not further alter the mitochondrial function in early embryos. Lastly, we show that survival in early gestation was not different between clones from pharmacologically induced WE-like donor cells and controls.

Toxic effects of atrazine on porcine oocytes and possible mechanisms of action

Because atrazine is a widely used herbicide, its adverse effects on the reproductive system have been extensively researched. In this study, we investigated the effects of atrazine exposure on porcine oocyte maturation and the possible mechanisms. Our results showed that the rates of oocyte maturation significantly decreased after treatment with 200 μM atrazine in vitro. Atrazine treatment resulted in abnormal spindle morphology but did not affect actin distribution. Atrazine exposure not only triggered a DNA damage response but also decreased MPF levels in porcine oocytes. Our results also revealed that atrazine worsened porcine oocyte quality by causing excessive accumulation of superoxide radicals, increasing cathepsin B activity, and decreasing the GSH level and mitochondrial membrane potential. Furthermore, atrazine decreased developmental competence of porcine oocytes up to the blastocyst stage and changed some properties: cell numbers, apoptosis, and related gene expression levels. Collectively, our results indicate that porcine oocyte maturation is defective after atrazine treatment at least through disruption of spindle morphology, MPF activity, and mitochondrial function and via induction of DNA damage, which probably reduces developmental competence.

Handmade cloning: recent advances, potential and pitfalls

Handmade cloning (HMC) is the most awaited, simple and micromanipulator-free version of somatic cell nuclear transfer (SCNT). The requirement of expensive micromanipulators and skilled expertise is eliminated in this technique, proving it as a major revolution in the field of embryology. During the past years, many modifications have been incorporated in this technique to boost its efficiency. This alternative approach to micromanipulator based traditional cloning (TC) works wonder in generating comparable or even higher birth rates in addition to declining costs drastically and enabling cryopreservation. This technique is not only applicable to intraspecies nuclear transfer but also to interspecies nuclear transfer (iSCNT) thus permitting conservation of endangered species. It also offers unique possibilities for automation of SCNT which aims at production of transgenic animals that can cure certain human diseases by producing therapeutics hence, providing a healthier future for the wellbeing of humans. The present review aims at highlighting certain aspects of HMC including recent advancements in procedure and factors involved in elevating its efficiency besides covering the potentials and pitfalls of this technique.