Arginine increases development of in vitro-produced porcine embryos and affects the protein arginine methyltransferase-dimethylarginine dimethylaminohydrolase-nitric oxide axis

Novel off-Targeting Events Identified after Genome Wide Analysis of CRISPR-Cas Edited Pigs

CRISPR-Cas technology has transformed our ability to introduce targeted modifications, allowing unconventional animal models such as pigs to model human diseases and improve its value for food production. The main concern with using the technology is the possibility of introducing unwanted modifications in the genome. In this study, we illustrate a pipeline to comprehensively identify off-targeting events on a global scale in the genome of three different gene-edited pig models. Whole genome sequencing paired with an off-targeting prediction software tool filtered off-targeting events amongst natural variations present in gene-edited pigs. This pipeline confirmed two known off-targeting events in IGH knockout pigs, AR and RBFOX1, and identified other presumably off-targeted loci. Independent validation of the off-targeting events using other gene-edited DNA confirmed two novel off-targeting events in RAG2/IL2RG knockout pig models. This unique strategy offers a novel tool to detect off-targeting events in genetically heterogeneous species after genome editing.

Arginine and its metabolites stimulate proliferation, differentiation, and physiological function of porcine trophoblast cells through β-catenin and mTOR pathways

Arginine, which is metabolized into ornithine, proline, and nitric oxide, plays an important role in embryonic development. The present study was conducted to investigate the molecular mechanism of arginine in proliferation, differentiation, and physiological function of porcine trophoblast cells (pTr2) through metabolic pathways. The results showed that arginine significantly increased cell viability (P < 0.05). The addition of arginine had a quadratic tendency to increase the content of progesterone (P = 0.06) and protein synthesis rate (P = 0.03), in which the maximum protein synthesis rate was observed at 0.4 mM arginine. Arginine quadratically increased (P < 0.05) the intracellular contents of spermine, spermidine and putrescine, as well as linearly increased (P < 0.05) the intracellular content of NO in a dose-dependent manner. Arginine showed a quadratic tendency to increase the content of putrescine (P = 0.07) and a linear tendency to increase NO content (P = 0.09) in cell supernatant. Moreover, increasing arginine activated (P < 0.05) the mRNA expressions for ARG, ODC, iNOS and PCNA. Furthermore, inhibitors of arginine metabolism (L-NMMA and DFMO) both inhibited cell proliferation, while addition of its metabolites (NO and putrescine) promoted the cell proliferation and cell cycle, the mRNA expressions of PCNA, EGF and IGF-1, and increased (P < 0.05) cellular protein synthesis rate, as well as estradiol and hCG secretion (P < 0.05). In conclusion, our results suggested that arginine could promote cell proliferation and physiological function by regulating the metabolic pathway. Further studies showed that arginine and its metabolites modulate cell function mainly through β-catenin and mTOR pathways.

The Role of L-Arginine-NO System in Female Reproduction: A Narrative Review

Accumulating evidence are available on the involvement of l-arginine-nitric oxide (NO) system in complex biological processes and numerous clinical conditions. Particular attention was made to reveal the association of l-arginine and methylarginines to outcome measures of women undergoing in vitro fertilization (IVF). This review attempts to summarize the expression and function of the essential elements of this system with particular reference to the different stages of female reproduction. A literature search was performed on the PubMed and Google Scholar systems. Publications were selected for evaluation according to the results presented in the Abstract. The regulatory role of NO during the period of folliculogenesis, oocyte maturation, fertilization, embryogenesis, implantation, placentation, pregnancy, and delivery was surveyed. The major aspects of cellular l-arginine uptake via cationic amino acid transporters (CATs), arginine catabolism by nitric oxide synthases (NOSs) to NO and l-citrulline and by arginase to ornithine, and polyamines are presented. The importance of NOS inhibition by methylated arginines and the redox-sensitive elements of the process of NO generation are also shown. The l-arginine-NO system plays a crucial role in all stages of female reproduction. Insufficiently low or excessively high rates of NO generation may have adverse influences on IVF outcome.

Arginine Regulates Zygotic Genome Activation in Porcine Embryos Under Nutrition Restriction

Arginine has a positive effect on pre-implantation development in pigs. However, the exact mechanism by which arginine promotes embryonic development is undefined. Here, single-cell RNA sequencing technology was applied to porcine in vivo pre-implantation embryos from the zygote to morula stage, it was found that that the expression of arginine metabolism-related genes clearly changed from the 2-cell stage to the 4-cell stage, when zygotic genome activation (ZGA) occurs in porcine embryos. Further analysis showed that arginine metabolism-related genes are significantly correlated with key ZGA genes. To determine the function of arginine in porcine embryos during ZGA, the in vitro fertilization embryos were cultured in PZM-3 medium (0.12 mM arginine, Control group), a modified PZM-3 medium (0 mM arginine, Block group) and a modified PZM-3 medium supplemented with arginine (0.12 mM arginine, Block + Arg group). The results showed that the 4-cell arrest rate was significantly increased in the Block group compared to the Control group (P < 0.05). The 4-cell arrest rate in the Block + Arg group was significantly decreased than that in the Block group (P < 0.05). Meanwhile, the expression of ZGA marker genes and SIRT1 protein in 4-cell embryos was significantly decreased in the Block group compared to the Control group, and their expression was significantly increased in the Block + Arg group. In addition, we observed that the glutathione (GSH), ATP levels, and lipid droplet contents were significantly increased, and the reactive oxygen species (ROS) level was decreased in the Block + Arg group compared to the Block group. Compared with Control group, spermine content in culture medium and the mRNA expression of ornithine decarboxylase1 (ODC1) of embryos in the Block group were significantly decreased (P < 0.05), and those in the Block + Arg group were significantly increased compared with the Block group (P < 0.05). Moreover, when difluoromethylornithine (an inhibitor of ODC1) was added to the modified PZM-3 medium supplemented with arginine, the effect of arginine on ZGA was inhibited. In summary, our findings demonstrated that arginine may regulate ZGA under nutrition restriction in porcine embryos by promoting polyamine synthesis.

Production of Pigs From Porcine Embryos Generated in vitro

Generating porcine embryos in vitro is a critical process for creating genetically modified pigs as agricultural and biomedical models; however, these embryo technologies have been scarcely applied by the swine industry. Currently, the primary issue with in vitro-produced porcine embryos is low pregnancy rate after transfer and small litter size, which may be exasperated by micromanipulation procedures. Thus, in this review, we discuss improvements that have been made to the in vitro porcine embryo production system to increase the number of live piglets per pregnancy as well as abnormalities in the embryos and piglets that may arise from in vitro culture and manipulation techniques. Furthermore, we examine areas related to embryo production and transfer where improvements are warranted that will have direct applications for increasing pregnancy rate after transfer and the number of live born piglets per litter.

Importance of the pig as a human biomedical model

[Figure: see text].

Amino Acid Transport and Metabolism Regulate Early Embryo Development: Species Differences, Clinical Significance, and Evolutionary Implications

In this review we discuss the beneficial effects of amino acid transport and metabolism on pre- and peri-implantation embryo development, and we consider how disturbances in these processes lead to undesirable health outcomes in adults. Proline, glutamine, glycine, and methionine transport each foster cleavage-stage development, whereas leucine uptake by blastocysts via transport system B^0,+ promotes the development of trophoblast motility and the penetration of the uterine epithelium in mammalian species exhibiting invasive implantation. (Amino acid transport systems and transporters, such as B^0,+, are often oddly named. The reader is urged to focus on the transporters’ functions, not their names.) B^0,+ also accumulates leucine and other amino acids in oocytes of species with noninvasive implantation, thus helping them to produce proteins to support later development. This difference in the timing of the expression of system B^0,+ is termed heterochrony—a process employed in evolution. Disturbances in leucine uptake via system B^0,+ in blastocysts appear to alter the subsequent development of embryos, fetuses, and placentae, with undesirable consequences for offspring. These consequences may include greater adiposity, cardiovascular dysfunction, hypertension, neural abnormalities, and altered bone growth in adults. Similarly, alterations in amino acid transport and metabolism in pluripotent cells in the blastocyst inner cell mass likely lead to epigenetic DNA and histone modifications that produce unwanted transgenerational health outcomes. Such outcomes might be avoided if we learn more about the mechanisms of these effects.

Challenges and Considerations during In Vitro Production of Porcine Embryos

Genetically modified pigs have become valuable tools for generating advances in animal agriculture and human medicine. Importantly, in vitro production and manipulation of embryos is an essential step in the process of creating porcine models. As the in vitro environment is still suboptimal, it is imperative to examine the porcine embryo culture system from several angles to identify methods for improvement. Understanding metabolic characteristics of porcine embryos and considering comparisons with other mammalian species is useful for optimizing culture media formulations. Furthermore, stressors arising from the environment and maternal or paternal factors must be taken into consideration to produce healthy embryos in vitro. In this review, we progress stepwise through in vitro oocyte maturation, fertilization, and embryo culture in pigs to assess the status of current culture systems and address points where improvements can be made.

Effects of RAD51-stimulatory compound 1 (RS-1) and its vehicle, DMSO, on pig embryo culture

Pigs have become an important model for agricultural and biomedical purposes. The advent of genomic engineering tools, such as the CRISPR/Cas9 system, has facilitated the production of livestock models with desired modifications. However, precise site-specific modifications in pigs through the homology-directed repair (HDR) pathway remains a challenge. In mammalian embryos, the use of small molecules to inhibit non-homologous end joining (NHEJ) or to improve HDR have been tested, but little is known about their toxicity. The compound RS-1 stimulates the activity of the RAD51 protein, which plays a key role in the HDR mechanism, demonstrating enhancement of HDR events in rabbit and bovine zygotes. Thus, in this study, we evaluated the dosage and temporal effects of RS-1 on porcine embryo development and viability. Additionally, we assessed the effects of its vehicle, DMSO, during embryo in vitro culture. Transient exposure to 7.5 μM of RS-1 did not adversely affect early embryo development and was compatible with subsequent development to term. Additionally, low concentrations of its vehicle, DMSO, did not show any toxicity to in vitro produced embryos. The transient use of RS-1 at 7.5 μM during in vitro culture seems to be the best protocol of choice to reduce the potentially toxic effects of RS-1 while attempting to improve HDR in the pig. Direct injection of the CRISPR/Cas9 system, combined with strategies to increase the frequency of targeted modifications via HDR, have become an important tool to simplify and accelerate the production of genetically modified livestock models.

Evidence of haptoglobin in the porcine female genital tract during oestrous cycle and its effect on in vitro embryo production

Recent evidence supports involvement of the acute phase protein haptoglobin in numerous events during mammalian reproduction. The present study represents an in-depth investigation of haptoglobin expression and secretion in the porcine oviduct and uterus, and assesses its effect on porcine in vitro embryo production. A systematic study was made of sows in different oestrous stages: late follicular, early luteal and late luteal stages. Relative haptoglobin mRNA abundance was quantified by RT-qPCR. In addition, expression of the protein was analysed by immunohistochemistry and the results were complemented by Western-blot and proteomic analyses of the oviductal and uterine fluids. In vitro porcine fertilization and embryo culture were carried out in the presence of haptoglobin. The results indicate that haptoglobin mRNA expression in the porcine oviduct and uterus is most abundant during the late luteal stage of the oestrous cycle. By means of Western blot and proteomic analyses haptoglobin presence was demonstrated in the oviduct epithelium and in the oviductal and uterine fluids in different stages of the oestrous cycle. The addition of haptoglobin during gamete co-incubation had no effect on sperm penetration, monospermy or efficiency rates; however, compared with the control group, blastocyst development was significantly improved when haptoglobin was present (haptoglobin: 64.50% vs. control: 37.83%; p < 0.05). In conclusion, the presence of haptoglobin in the oviduct and uterus of sows at different stages of the oestrous cycle suggests that it plays an important role in the reproduction process. The addition of haptoglobin during in vitro embryo production improved the blastocyst rates.

Glutaminolysis is involved in the activation of mTORC1 in in vitro-produced porcine embryos

Glutamine supplementation to porcine embryo culture medium improves development, increases leucine consumption, and enhances mitochondrial activity. In cancer cells, glutamine has been implicated in the activation of mechanistic target of rapamycin complex 1 (mTORC1) to support rapid proliferation. The objective of this study was to determine if glutamine metabolism, known as glutaminolysis, was involved in mTORC1 activation in porcine embryos. Culture with 3.75 mM GlutaMAX improved development to the blastocyst stage compared to culture with 1 mM GlutaMAX, and culture with 0 mM GlutaMAX decreased development compared to all groups with GlutaMAX. Ratios of phosphorylated to total MTOR were increased when embryos were cultured with 3.75 or 10 mM GlutaMAX, which was enhanced by the absence of leucine, but ratios for RPS6K were unchanged. As another indicator of mTORC1 activation, colocalization of MTOR and a lysosomal marker was increased in embryos cultured with 3.75 or 10 mM GlutaMAX in the absence of leucine. Culturing embryos with glutaminase inhibitors decreased development and the ratio of phosphorylated to total MTOR, indicating reduced activation of the complex. Therefore, glutaminolysis is involved in the activation of mTORC1 in porcine embryos, but further studies are needed to characterize downstream effects on development.

Neither gonadotropin nor cumulus cell expansion is needed for the maturation of competent porcine oocytes in vitro†

In-vitro maturation (IVM) of oocytes from immature females is widely used in assisted reproductive technologies. Here we illustrate that cumulus cell (CC) expansion, once considered a key indicator of oocyte quality, is not needed for oocytes to mature to the metaphase II (MII) stage and to gain nuclear and cytoplasmic competence to produce offspring. Juvenile pig oocytes were matured in four different media: (1) Basal (-gonadotropins (GN) - FLI); (2) -GN + FLI (supplement of FGF2, LIF, and IGF1); (3) +GN - FLI; and (4) +GN + FLI. There was no difference in maturation to MII or progression to the blastocyst stage after fertilization of oocytes that had been matured in -GN + FLI medium and oocytes matured in +GN + FLI medium. Only slight CC expansion occurred in the two media lacking GN compared with the two where GN was present. The cumulus-oocytes-complexes (COC) matured in +GN + FLI exhibited the greatest expansion. We conclude that FLI has a dual role. It is directly responsible for oocyte competence, a process where GN are not required, and, when GN are present, it has a downstream role in enhancing CC expansion. Our study also shows that elevated phosphorylated MAPK may not be a necessary correlate of oocyte maturation and that the greater utilization of glucose by COC observed in +GN + FLI medium probably plays a more significant role to meet the biosynthetic needs of the CC to expand than to attain oocyte developmental competence. Gene expression analyses have not been informative in providing a mechanism to explain how FLI medium enhances oocyte competence without promoting CC expansion.

PRMT5 inhibition modulates murine dendritic cells activation by inhibiting the metabolism switch: a new therapeutic target in periodontitis

Background

Protein arginine methyltransferase 5 (PRMT5) catalyzes the methylation of arginine residues in multiple proteins. Recent reports have highlighted the anti-inflammatory role of PRMT5. Dendritic cells (DCs) are well-known professional antigen-presenting cells that are crucial for immune response initiation. However, whether PRMT5 participates in DC immunity processes is unknown.

Methods

In an in vitro experiment, a PRMT5 inhibitor (EPZ015666) was used to inhibit PRMT5 expression, and lipopolysaccharide (LPS) stimulation was applied to mimic the inflammation context. Proinflammatory cytokine production, interferon-stimulated genes (ISGs), costimulatory molecules, major histocompatibility complex (MHC) expression and DC metabolism were measured following PRMT5 inhibition and LPS stimulation. In an in vivo study, we first tested PRMT5 mRNA and protein expression in a BALB/c mouse ligature-induced periodontitis model. Then, we evaluated changes in periodontal tissue and DC migration to cervical lymph nodes after local treatment with the PRMT5 inhibitor.

Results

The in vitro results revealed that PRMT5 inhibition attenuated DC activation and maturation by inhibiting the expression of proinflammatory cytokines, ISGs, costimulatory molecules, and MHC induced by LPS stimulation. We also found that inhibition of PRMT5 blocked the DC metabolic switch to glycolysis. In the in vivo study, we found that PRMT5 inhibition reversed the severity of the lesions and slowed the migration of DCs to cervical lymph nodes.

Conclusions

The results show a critical role of PRMT5 in the control of DC activation through inhibition of the metabolic switch and indicate that PRMT5 is a promising therapeutic target in periodontitis.

Iron deficiency negatively regulates protein methylation via the downregulation of protein arginine methyltransferase

Iron is an essential trace metal for all biological processes and plays a role in almost every aspect of body growth. Previously, we found that iron-depletion downregulated the expression of proteins, arginine methyltransferase-1 and 3 (PRMT1 and PRMT3), by an iron-specific chelator, deferoxamine (DFO), in rat liver FAO cell line using DNA microarray analysis (unpublished data). However, regulatory mechanisms underlying the association between iron deficiency and PRMT expression are unclear in vitro and in vivo. In the present study, we revealed that the treatment of cells with two iron-specific chelators, DFO and deferasirox (DFX), downregulated the gene and protein expression of PRMT1 and 3 as compared with the untreated cells. Subsequently, DFO and DFX treatments decreased protein methylation. Importantly, these effects were attenuated by a holo-transferrin treatment. Furthermore, weanling Wistar-strain rats were fed a control diet or an iron-deficient diet for 4 weeks. Dietary iron deficiency was found to decrease the concentration of hemoglobin and liver iron while increasing the heart weight. PRMT and protein methylation levels were also significantly reduced in the iron-deficient group as compared to the control group. To our knowledge, this is the first study to demonstrate that PRMT levels and protein methylation are reduced in iron-deficient models, in vitro and in vivo.

Removal of hypotaurine from porcine embryo culture medium does not impair development of in vitro-fertilized or somatic cell nuclear transfer-derived embryos at low oxygen tension

Hypotaurine (HT) is a routine component of porcine embryo culture medium, functioning as an antioxidant, but its requirement may be diminished as most embryo culture systems now use 5% O2 instead of atmospheric (20%) O2 . Our objective was to determine the effects of removing HT from the culture medium on porcine preimplantation embryo development. Embryos cultured in 20% O2 without HT had decreased blastocyst development compared to culture with HT or in 5% O2 with or without HT. Notably, differences in blastocyst development or total cell number were not detected between embryos cultured in 5% O2 with or without HT. After culture in 5% O2 without HT and embryo transfer, healthy fetuses were retrieved from two pregnancies on Day 42, confirming in vivo developmental competence. Transcript abundance of proapoptotic markers was decreased in embryos cultured without HT regardless of oxygen tension; however, assays for apoptosis did not demonstrate differences between groups. Additionally, no differences were observed in the development or apoptosis of somatic cell nuclear transfer-derived embryos cultured in 5% O2 with or without HT. With decreased utility in 5% O2 , removing HT from porcine embryo culture medium would also have economic advantages because it is undoubtedly the most expensive component.

A novel culture medium with reduced nutrient concentrations supports the development and viability of mouse embryos

Further refinement of culture media is needed to improve the quality of embryos generated in vitro. Previous results from our laboratory demonstrated that uptake of nutrients by the embryo is significantly less than what is supplied in traditional culture media. Our objective was to determine the impact of reduced nutrient concentrations in culture medium on mouse embryo development, metabolism, and quality as a possible platform for next generation medium formulation. Concentrations of carbohydrates, amino acids, and vitamins could be reduced by 50% with no detrimental effects, but blastocyst development was impaired at 25% of standard nutrient provision (reduced nutrient medium; RN). Addition of pyruvate and L-lactate (+PL) to RN at 50% of standard concentrations restored blastocyst development, hatching, and cell number. In addition, blastocysts produced in RN + PL contained more ICM cells and ATP than blastocysts cultured in our control (100% nutrient) medium; however, metabolic activity was altered. Similarly, embryos produced in the RN medium with elevated (50% control) concentrations of pyruvate and lactate in the first step medium and EAA and Glu in the second step medium were competent to implant and develop into fetuses at a similar rate as embryos produced in the control medium. This novel approach to culture medium formulation could help define the optimal nutrient requirements of embryos in culture and provide a means of shifting metabolic activity towards the utilization of specific metabolic pathways that may be beneficial for embryo viability.

Analysis of the uterine lumen in fertility-classified heifers: II. Proteins and metabolites†

Survival and growth of the bovine conceptus is dependent on endometrial secretions or histotroph. Previously, serial blastocyst transfer was used to classify heifers as high fertile (HF), subfertile (SF), or infertile (IF). Here, we investigated specific histotroph components (proteins and metabolites) in the uterine lumen of day 17 fertility-classified heifers. Interferon tau (IFNT) was more abundant in uterine lumenal fluid (ULF) of pregnant HF than SF animals as the conceptus was longer in HF heifers. However, no differences in endometrial expression of selected classical and nonclassical interferon-stimulated genes (ISGs) were observed, suggesting that IFNT signaling in the endometrium of pregnant HF and SF heifers was similar. Pregnancy significantly increased the abundance of several proteins in ULF. Based on functional annotation, the abundance of a number of proteins involved in energy metabolism, oxidative stress, amino acid metabolism, and cell proliferation and differentiation were greater in the ULF of pregnant HF than SF heifers. Metabolomics analysis found that pregnancy only changed the metabolome composition of ULF from HF heifers. The majority of the metabolites that increased in the ULF of pregnant HF as compared to SF heifers were associated with energy and amino acid metabolism. The observed differences in ULF proteome and metabolome are hypothesized to influence uterine receptivity with consequences on conceptus development and survival in fertility-classified heifers.

Inhibition of PRMT5 Attenuates Oxidative Stress-Induced Pyroptosis via Activation of the Nrf2/HO-1 Signal Pathway in a Mouse Model of Renal Ischemia-Reperfusion Injury

Background

Extensive evidence has demonstrated that oxidative stress, pyroptosis, and proinflammatory programmed cell death are related to renal ischemia/reperfusion (I/R) injury. However, the underlying mechanism remains to be illustrated. Protein arginine methylation transferase 5 (PRMT5), which mediates arginine methylation involved in the regulation of epigenetics, exhibits a variety of biological functions and essential roles in diseases. The present study investigated the role of PRMT5 in oxidative stress and pyroptosis induced by I/R injury in a mouse model and in a hypoxia/reoxygenation (H/R) model of HK-2 cells.

Methods

C57 mice were used as an animal model. All mice underwent right nephrectomy, and the left renal pedicles were either clamped or not. Renal I/R injury was induced by ligating the left renal pedicle for 30 min followed by reperfusion for 24 h. HK-2 cells were exposed to normal conditions or stimulation through H/R. EPZ015666(EPZ)—a selective potent chemical inhibitor—and small interfering RNA (siRNA) were administered to suppress the function and expression of PRMT5. The levels of urea nitrogen and creatinine in the serum and renal tissue injury were assessed. Immunohistochemistry, western blotting, and reverse transcription-polymerase chain reaction were used to evaluate pyroptosis-related proteins including nod-like receptor protein-3, ASC, caspase-1, caspase-11, GSDMD-N, and interleukin-1β. Cell apoptosis and cell viability were detected through flow cytometry, and the levels of reactive oxygen species (ROS) and hydrogen peroxide (H₂O₂) were measured. Ki-67 was used to assess the proliferation of renal tubular epithelium. In addition, the activity of malondialdehyde and superoxide dismutase was determined.

Results

I/R or H/R induced an increase in the expression of PRMT5. Inhibition of PRMT5 by EPZ alleviated oxidative stress and I/R- or H/R-induced pyroptosis. In renal tissue, the application of EPZ promoted the proliferation of tubular epithelium. In addition, H/R-induced pyroptosis in HK-2 cells was dependent on oxidative stress in vitro. Administration of either EPZ or siRNA led to decreased expression of pyroptosis-related proteins. Inhibition of PRMT5 also attenuated the I/R- or H/R-induced oxidative stress in vivo and in HK-2 cells, respectively. It also resulted in a distinct decrease in the levels of malondialdehyde and H₂O₂, and an apparent increase in superoxide dismutase activity in mouse renal tissue. Moreover, it led to a significant decrease in the levels of ROS and H₂O₂ in HK-2 cells. When activated, NF-E2-related factor/heme oxygenase-1 (Nrf2/HO-1)—a key regulator of various cytoprotective proteins that withstand oxidative damage—can decrease the generation of ROS. Nrf2/HO-1 was downregulated during I/R in tissues and H/R in HK-2 cells, and this effect was reversed by the PRMT5 inhibitor. Furthermore, the expressions of Nrf2 and HO-1 proteins were markedly upregulated by EPZ or siRNA against PRMT5.

Conclusion

PRMT5 is involved in ischemia- and hypoxia-induced oxidative stress and pyroptosis in vitro and in vivo. Inhibition of PRMT5 may ameliorate renal I/R injury by suppressing oxidative stress and pyroptosis via the activation of the Nrf2/HO-1 pathway, as well as promoting the proliferation of tubular epithelium. Therefore, PRMT5 may be a promising therapeutic target.

Contributions of RNA-seq to improve in vitro embryo production (IVP)

In Vitro Embryo Production (IVP) is widely used to improve the reproductive efficiency of livestock animals, however increasing the embryo development rates and pregnancy outcomes is still a challenge for some species. Thus, the lack of biological knowledge hinders developing specie-specific IVP protocols. Therefore, the contributions of RNA-seq to generate relevant biological knowledge and improve the efficiency of IVP in livestock animals are reviewed herein.

Glutamine supplementation enhances development of in vitro-produced porcine embryos and increases leucine consumption from the medium

Improper composition of culture medium contributes to reduced viability of in vitro-produced embryos. Glutamine (Gln) is a crucial amino acid for preimplantation embryos as it supports proliferation and is involved in many different biosynthetic pathways. Previous transcriptional profiling revealed several upregulated genes related to Gln transport and metabolism in in vitro-produced porcine blastocysts compared to in vivo-produced counterparts, indicating a potential deficiency in the culture medium. Therefore, the objective of this study was to determine the effects of Gln supplementation on in vitro-produced porcine embryo development, gene expression, and metabolism. Cleaved embryos were selected and cultured in MU2 medium supplemented with 1 mM Gln (control), 3.75 mM Gln (+Gln), 3.75 mM GlutaMAX (+Max), or 3.75 mM alanine (+Ala) until day 6. Embryos cultured with +Gln or +Max had increased development to the blastocyst stage and total number of nuclei compared to the control (P < 0.05). Moreover, expression of misregulated transcripts involved in glutamine and glutamate transport and metabolism was corrected when embryos were cultured with +Gln or +Max. Metabolomics analysis revealed increased production of glutamine and glutamate into the medium by embryos cultured with +Max and increased consumption of leucine by embryos cultured with +Gln or +Max. As an indicator of cellular health, mitochondrial membrane potential was increased when embryos were cultured with +Max which was coincident with decreased apoptosis in these blastocysts. Lastly, two embryo transfers by using embryos cultured with +Max resulted in viable piglets, confirming that this treatment is consistent with in vivo developmental competence.

Applications of omics and nanotechnology to improve pig embryo production in vitro

An appropriate environment to optimize porcine preimplantation embryo production in vitro is required as genetically modified pigs have become indispensable for biomedical research and agriculture. To provide suitable culture conditions, omics technologies have been applied to elucidate which metabolic substrates and pathways are involved during early developmental processes. Metabolomic profiling and transcriptional analysis comparing in vivo- and in vitro-derived embryos have demonstrated the important role of amino acids during preimplantation development. Transcriptional profiling studies have been helpful in assessing epigenetic reprogramming agents to allow for the correction of gene expression during the cloning process. Along with this, nanotechnology, which is a highly promising field, has allowed for the use of engineered nanoplatforms in reproductive biology. A growing number of studies have explored the use of nanoengineered materials for sorting, labeling, and targeting purposes; which demonstrates their potential to become one of the solutions for precise delivery of molecules into gametes and embryos. Considering the contributions of omics and the recent progress in nanoscience, in this review, we focused on their emerging applications for current in vitro pig embryo production systems to optimize the generation of genetically modified animals.

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.

In Vitro Maturation, Fertilization, and Culture of Pig Oocytes and Embryos

Assisted reproductive technologies in the pig are critical for the production of genetically modified pigs as models of human disease and to improve production agriculture. Methods of oocyte maturation, fertilization, and culture all play an extremely important role in how the embryo, fetus, and offspring will develop. In this chapter, we discuss the historical methods and recent advances that have been essential in promoting efficient and competent embryo development. Here we describe the procedures that can be used to mature, fertilize, and culture pig embryos to the blastocyst stage.

Resistance to coronavirus infection in amino peptidase N-deficient pigs

The alphacoronaviruses, transmissible gastroenteritis virus (TGEV) and Porcine epidemic diarrhea virus (PEDV) are sources of high morbidity and mortality in neonatal pigs, a consequence of dehydration caused by the infection and necrosis of enterocytes. The biological relevance of amino peptidase N (ANPEP) as a putative receptor for TGEV and PEDV in pigs was evaluated by using CRISPR/Cas9 to edit exon 2 of ANPEP resulting in a premature stop codon. Knockout pigs possessing the null ANPEP phenotype and age matched wild type pigs were challenged with either PEDV or TGEV. Fecal swabs were collected daily from each animal beginning 1 day prior to challenge with PEDV until the termination of the study. The presence of virus nucleic acid was determined by PCR. ANPEP null pigs did not support infection with TGEV, but retained susceptibility to infection with PEDV. Immunohistochemistry confirmed the presence of PEDV reactivity and absence of TGEV reactivity in the enterocytes lining the ileum in ANPEP null pigs. The different receptor requirements for TGEV and PEDV have important implications in the development of new genetic tools for the control of enteric disease in pigs.

Iloprost supports early development of in vitro-produced porcine embryos through activation of the phosphatidylinositol 3-kinase/AKT signalling pathway

Despite evidence of the presence of prostaglandin (PG) I₂ in mammalian oviducts, its role in early development of in vitro-produced (IVP) embryos is largely unknown. Thus, in the present study we examined the effects of iloprost, a PGI₂ analogue, on the in vitro developmental competence of early porcine embryos and the underlying mechanism(s). To examine the effects of iloprost on the development rate of IVF embryos, iloprost was added to the in vitro culture (IVC) medium and cultured for 6 days. Supplementation of the IVC medium with iloprost significantly improved developmental parameters, such as blastocyst formation rate, the trophectoderm:inner cell mass ratio and cell survival in IVF and parthenogenetically activated (PA) embryos. In addition, post-blastulation development into the expanded blastocyst stage was improved in iloprost-treated groups compared with controls. Interestingly, the phosphatidylinositol 3-kinase (PI3K)/AKT signalling pathway was significantly activated by iloprost supplementation in a concentration-dependent manner (10-1000nM), and the beneficial effects of iloprost on the early development of porcine IVF and PA embryos was completely ablated by treatment with 2.5μM wortmannin, a PI3K/AKT signalling inhibitor. Importantly, expression of the PI3K/AKT signalling pathway was significantly reduced in somatic cell nuclear transfer (SCNT) compared with IVF embryos, and iloprost supported the early development of SCNT embryos, as was the case for IVF and PA embryos, suggesting a consistent effect of iloprost on the IVC of IVP porcine embryos. Together, these results indicate that iloprost can be a useful IVC supplement for production of IVP early porcine embryos with high developmental competence.

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.

miRNA-145 is associated with spontaneous hypertension by targeting SLC7A1

Previous studies have indicated that microRNAs (miRNAs/miRs) may participate in the pathogenesis of hypertension. miR-145 has been demonstrated to serve important roles in the development of numerous cardiovascular diseases. However, the specific role of miR-145 in hypertension remains unclear. The present study aimed to investigate the role of miR-145 in spontaneously hypertensive rats (SHR) and rat vascular endothelial cells (RVECs). The results of the present study demonstrated that in the SHR group miR-145 expression was significantly upregulated in the thoracic aorta compared with the control group. Furthermore, a significant decrease in nitric oxide (NO) content was observed in the SHR group compared with the control rats. In RVECs, silencing miR-145 induced a significant increase in the expression of solute carrier family 7 member 1 (SLC7A1) and phosphorylated endothelial nitric oxide synthase, and a dual-luciferase reporter assay confirmed that SLC7A1 is a direct target of miR-145. The results of the present study indicate that miR-145 functions as a key mediator in the pathogenesis of hypertension via targeting SLC7A1, which suggests that miR-145 is a potential target for the treatment of hypertension.

Quadrupling efficiency in production of genetically modified pigs through improved oocyte maturation

Assisted reproductive technologies in all mammals are critically dependent on the quality of the oocytes used to produce embryos. For reasons not fully clear, oocytes matured in vitro tend to be much less competent to become fertilized, advance to the blastocyst stage, and give rise to live young than their in vivo-produced counterparts, particularly if they are derived from immature females. Here we show that a chemically defined maturation medium supplemented with three cytokines (FGF2, LIF, and IGF1) in combination, so-called "FLI medium," improves nuclear maturation of oocytes in cumulus-oocyte complexes derived from immature pig ovaries and provides a twofold increase in the efficiency of blastocyst production after in vitro fertilization. Transfer of such blastocysts to recipient females doubles mean litter size to about nine piglets per litter. Maturation of oocytes in FLI medium, therefore, effectively provides a fourfold increase in piglets born per oocyte collected. As they progress in culture, the FLI-matured cumulus-oocyte complexes display distinctly different kinetics of MAPK activation in the cumulus cells, much increased cumulus cell expansion, and an accelerated severance of cytoplasmic projections between the cumulus cells outside the zona pellucida and the oocyte within. These events likely underpin the improvement in oocyte quality achieved by using the FLI medium.

Zygote injection of CRISPR/Cas9 RNA successfully modifies the target gene without delaying blastocyst development or altering the sex ratio in pigs

The CRISPR/Cas9 genome editing tool has increased the efficiency of creating genetically modified pigs for use as biomedical or agricultural models. The objectives were to determine if DNA editing resulted in a delay in development to the blastocyst stage or in a skewing of the sex ratio. Six DNA templates (gBlocks) that were designed to express guide RNAs that target the transmembrane protease, serine S1, member 2 (TMPRSS2) gene were in vitro transcribed. Pairs of CRISPR guide RNAs that flanked the start codon and polyadenylated Cas9 were co-injected into the cytoplasm of zygotes and cultured in vitro to the blastocyst stage. Blastocysts were collected as they formed on days 5, 6 or 7. PCR was performed to determine genotype and sex of each embryo. Separately, embryos were surgically transferred into recipient gilts on day 4 of estrus. The rate of blastocyst development was not significantly different between CRISPR injection embryos or the non-injected controls at day 5, 6 or 7 (p = 0.36, 0.09, 0.63, respectively). Injection of three CRISPR sets of guides resulted in a detectable INDEL in 92-100 % of the embryos analyzed. There was not a difference in the number of edits or sex ratio of male to female embryos when compared between days 5, 6 and 7 to the controls (p > 0.22, >0.85). There were 12 resulting piglets and all 12 had biallelic edits of TMRPSS2. Zygote injection with CRISPR/Cas9 continues to be a highly efficient tool to genetically modify pig embryos.

Direct and Osmolarity-Dependent Effects of Glycine on Preimplantation Bovine Embryos

Concentrations of glycine (Gly) in embryo culture media are often lower (~0.1 mM) than those in oviductal or uterine fluids (≥1.2 mM). The objective of this study was to determine direct and osmolarity-dependent effects of physiological concentrations of Gly on blastocyst formation and hatching, cell allocation to the trophectoderm (TE) and inner cell mass (ICM), and metabolic activity of bovine embryos. In experiment 1, zygotes were cultured with 100 or 120 mM NaCl and 0 or 1 mM Gly for the first 72 h of culture. Blastocyst formation and hatching were improved (P<0.05) when embryos were cultured with 100 compared to 120 mM NaCl. Inclusion of 1 mM Gly improved (P<0.05) blastocyst formation compared to 0 mM Gly, but this effect was only significant (P<0.05) for embryos cultured with 120 mM NaCl, suggesting bovine embryos can utilize Gly as an osmolyte. In experiment 2, embryos were cultured with 0.1, 1.1, 2.1, or 4.1 mM Gly (100 mM NaCl) for the final 96 h of culture. Blastocyst development was not affected (P>0.05) by Gly, but hatching (0.1 mM Gly, 18.2%) was improved (P<0.05) when embryos were cultured with 1.1 (31.4%) or 2.1 (29.4%) mM Gly. Blastocyst, TE, and ICM cell numbers were not affected (P>0.05) by Gly in either experiment. Blastocysts produced alanine, glutamine, pyruvate, and urea and consumed aspartate, but this metabolic profile was not affected (P>0.05) by Gly. In conclusion, Gly (1.0 mM) improves the development of both early and late stage embryos, but beneficial effects are more pronounced for early embryos exposed to elevated osmolarity.

Glycine supplementation in vitro enhances porcine preimplantation embryo cell number and decreases apoptosis but does not lead to live births

Most in vitro culture conditions are less‐than‐optimal for embryo development. Here, we used a transcriptional‐profiling database to identify culture‐induced differences in gene expression in porcine blastocysts compared to in vivo‐produced counterparts. Genes involved in glycine transport (SLC6A9), glycine metabolism (GLDC, GCSH, DLD, and AMT), and serine metabolism (PSAT1, PSPH, and PHGDH) were differentially expressed. Addition of 10 mM glycine to the culture medium (currently containing 0.1 mM) reduced the abundance of SLC6A9 transcript and increased total cell number, primarily in the trophectoderm lineage (P = 0.003); this was likely by decreasing the percentage of apoptotic nuclei. As serine and glycine can be reversibly metabolized by serine hydroxymethyltransferase 2 (SHMT2), we assessed the abundance of SHMT2 transcript as well as its functional role by inhibiting it with aminomethylphosphonic acid (AMPA), a glycine analog, during in vitro culture. Both AMPA supplementation and elevated glycine decreased the mRNA abundance of SHMT2 and tumor protein p53 (TP53), which is activated in response to cellular stress, compared to controls (P ≤ 0.02). On the other hand, mitochondrial activity of blastocysts, mtDNA copy number, and abundance of mitochondria‐related transcripts did not differ between control and 10 mM glycine culture conditions. Despite improvements to these metrics of blastocyst quality, transfer of embryos cultured in 10 mM glycine did not result in pregnancy whereas the transfer of in vitro‐produced embryos cultured in control medium yielded live births. Mol. Reprod. Dev. 83: 246–258, 2016. © 2016 The Authors.