A porcine model of phenylketonuria generated by CRISPR/Cas9 genome editing

Phenylalanine hydroxylase-deficient (PAH-deficient) phenylketonuria (PKU) results in systemic hyperphenylalaninemia, leading to neurotoxicity with severe developmental disabilities. Dietary phenylalanine (Phe) restriction prevents the most deleterious effects of hyperphenylalaninemia, but adherence to diet is poor in adult and adolescent patients, resulting in characteristic neurobehavioral phenotypes. Thus, an urgent need exists for new treatments. Additionally, rodent models of PKU do not adequately reflect neurocognitive phenotypes, and thus there is a need for improved animal models. To this end, we have developed PAH-null pigs. After selection of optimal CRISPR/Cas9 genome-editing reagents by using an in vitro cell model, zygote injection of 2 sgRNAs and Cas9 mRNA demonstrated deletions in preimplantation embryos, with embryo transfer to a surrogate leading to 2 founder animals. One pig was heterozygous for a PAH exon 6 deletion allele, while the other was compound heterozygous for deletions of exon 6 and of exons 6-7. The affected pig exhibited hyperphenylalaninemia (2000-5000 μM) that was treatable by dietary Phe restriction, consistent with classical PKU, along with juvenile growth retardation, hypopigmentation, ventriculomegaly, and decreased brain gray matter volume. In conclusion, we have established a large-animal preclinical model of PKU to investigate pathophysiology and to assess new therapeutic interventions.

Long-term survival of pig-to-rhesus macaque renal xenografts is dependent on CD4 T cell depletion

The shortage of available organs remains the greatest barrier to expanding access to transplant. Despite advances in genetic editing and immunosuppression, survival in experimental models of kidney xenotransplant has generally been limited to <100 days. We found that pretransplant selection of recipients with low titers of anti-pig antibodies significantly improved survival in a pig-to-rhesus macaque kidney transplant model (6 days vs median survival time 235 days). Immunosuppression included transient pan-T cell depletion and an anti-CD154-based maintenance regimen. Selective depletion of CD4⁺ T cells but not CD8⁺ T cells resulted in long-term survival (median survival time >400 days vs 6 days). These studies suggested that CD4⁺ T cells may have a more prominent role in xenograft rejection compared with CD8⁺ T cells. Although animals that received selective depletion of CD8⁺ T cells showed signs of early cellular rejection (marked CD4⁺ infiltrates), animals receiving selective CD4⁺ depletion exhibited normal biopsy results until late, when signs of chronic antibody rejection were present. In vitro study results suggested that rhesus CD4⁺ T cells required the presence of SLA class II to mount an effective proliferative response. The combination of low pretransplant anti-pig antibody and CD4 depletion resulted in consistent, long-term xenograft survival.

Young Ossabaw Pigs Fed a Western Diet Exhibit Early Signs of Diabetic Retinopathy

Purpose

Recent clinical data suggest an increasing prevalence of obesity and type 2 diabetes in adolescents, placing them at high risk of developing diabetic retinopathy during adult working years. The present study was designed to characterize the early retinal and microvascular alterations in young Ossabaw pigs fed a Western diet, described as a model of metabolic syndrome genetically predisposed to type 2 diabetes.

Methods

Four-month-old Ossabaw miniature pigs were divided into two groups, lean and diet-induced obesity. Obese pigs were fed a Western diet with high-fat/high-fructose corn syrup/high-choleric content for 10 weeks. Blood and retina were collected for biochemical profiling, trypsin digest, flatmounts, Fluoro-Jade C staining, electron microscopy, quantitative PCR, immunohistochemistry, and Western blots.

Results

Young Ossabaw pigs had elevated fasting blood glucose after feeding on a Western diet for 10 weeks. Their retina showed disrupted cellular architecture across neural layers, with numerous large vacuoles seen in cell bodies of the inner nuclear layer. Microvessels in the obese animals exhibited thickened basement membrane, along with pericyte ghosts and acellular capillaries. The pericyte to endothelial ratio decreased significantly. Retina flatmounts from obese pigs displayed reduced capillary density, numerous terminal capillary loops, and string vessels, which stained collagen IV but not isolectin IB4. Quantitative PCR and Western blots showed significantly high levels of basement membrane proteins collagen IV and fibronectin in obese pigs.

Conclusions

This is the first study to describe the ultrastructural neuronal and vascular changes in the retina of young Ossabaw pigs fed a Western diet, simulating early signs of diabetic retinopathy pathogenesis.

Microvascular insulin resistance in skeletal muscle and brain occurs early in the development of juvenile obesity in pigs

Impaired microvascular insulin signaling may develop before overt indices of microvascular endothelial dysfunction and represent an early pathological feature of adolescent obesity. Using a translational porcine model of juvenile obesity, we tested the hypotheses that in the early stages of obesity development, impaired insulin signaling manifests in skeletal muscle (triceps), brain (prefrontal cortex), and corresponding vasculatures, and that depressed insulin-induced vasodilation is reversible with acute inhibition of protein kinase Cβ (PKCβ). Juvenile Ossabaw miniature swine (3.5 mo of age) were divided into two groups: lean control ( n = 6) and obese ( n = 6). Obesity was induced by feeding the animals a high-fat/high-fructose corn syrup/high-cholesterol diet for 10 wk. Juvenile obesity was characterized by excess body mass, hyperglycemia, physical inactivity (accelerometer), and marked lipid accumulation in the skeletal muscle, with no evidence of overt atherosclerotic lesions in athero-prone regions, such as the abdominal aorta. Endothelium-dependent (bradykinin) and -independent (sodium nitroprusside) vasomotor responses in the brachial and carotid arteries (wire myography), as well as in the skeletal muscle resistance and 2A pial arterioles (pressure myography) were unaltered, but insulin-induced microvascular vasodilation was impaired in the obese group. Blunted insulin-stimulated vasodilation, which was reversed with acute PKCβ inhibition (LY333-531), occurred alongside decreased tissue perfusion, as well as reduced insulin-stimulated Akt signaling in the prefrontal cortex, but not the triceps. In the early stages of juvenile obesity development, the microvasculature and prefrontal cortex exhibit impaired insulin signaling. Such adaptations may underscore vascular and neurological derangements associated with juvenile obesity.

Transcriptome Analysis of Pig In Vivo, In Vitro-Fertilized, and Nuclear Transfer Blastocyst-Stage Embryos Treated with Histone Deacetylase Inhibitors Postfusion and Activation Reveals Changes in the Lysosomal Pathway

Genetically modified pigs are commonly created via somatic cell nuclear transfer (SCNT). Treatment of reconstructed embryos with histone deacetylase inhibitors (HDACi) immediately after activation improves cloning efficiency. The objective of this experiment was to evaluate the transcriptome of SCNT embryos treated with suberoylanilide hydroxamic acid (SAHA), 4-iodo-SAHA (ISAHA), or Scriptaid as compared to untreated SCNT, in vitro-fertilized (IVF), and in vivo (IVV) blastocyst-stage embryos. SAHA (10 μM) had the highest level of blastocyst development at 43.9%, and all treatments except 10 μM ISAHA had the same percentage of blastocyst development as Scriptaid (p<0.05). Two treatments, 1.0 μM ISAHA and 1.0 μM SAHA, had higher mean cell number than No HDACi treatment (p<0.021). Embryo transfers performed with 10 μM SAHA- and 1 μM ISAHA-treated embryos resulted in the birth of healthy piglets. GenBank accession numbers from up- and downregulated transcripts were loaded into the Database for Annotation, Visualization and Integrated Discovery to identify enriched biological themes. HDACi treatment yielded the highest enrichment for transcripts within the Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway, lysosome. The mean intensity of LysoTracker was lower in IVV embryos compared to IVF and SCNT embryos (p<0.0001). SAHA and ISAHA can successfully be used to create healthy piglets from SCNT.

Engineering protein processing of the mammary gland to produce abundant hemophilia B therapy in milk

Both the low animal cell density of bioreactors and their ability to post-translationally process recombinant factor IX (rFIX) limit hemophilia B therapy to <20% of the world’s population. We used transgenic pigs to make rFIX in milk at about 3,000-fold higher output than provided by industrial bioreactors. However, this resulted in incomplete γ-carboxylation and propeptide cleavage where both processes are transmembrane mediated. We then bioengineered the co-expression of truncated, soluble human furin (rFurin) with pro-rFIX at a favorable enzyme to substrate ratio. This resulted in the complete conversion of pro-rFIX to rFIX while yielding a normal lactation. Importantly, these high levels of propeptide processing by soluble rFurin did not preempt γ-carboxylation in the ER and therefore was compartmentalized to the Trans-Golgi Network (TGN) and also to milk. The Golgi specific engineering demonstrated here segues the ER targeted enhancement of γ-carboxylation needed to biomanufacture coagulation proteins like rFIX using transgenic livestock.

Pig oocyte activation using a Zn²⁺ chelator, TPEN

Artificial oocyte activation is a critical step during SCNT. Most current activation protocols focus on inducing an increase in the intracellular free Ca(2+) concentration of the oocyte. Here, we have used a zinc chelator, TPEN, to enhance the efficiency of oocyte activation during SCNT. TPEN treatment of matured pig oocytes resulted in the reduction of available Zn(2+) in pig oocytes; however, the cytosolic Ca(2+) concentration in the oocytes was not affected by the TPEN treatment. When various concentrations (100-250 μM) and incubation durations (45 minutes-2.5 hours) of TPEN were used to activate oocytes, the efficiency of oocyte activation was not different from conventional activation methods. When oocytes that were activated by conventional activation methods were incubated with a lower concentration of TPEN (5-10 μM), a significant increase in embryos developing to the blastocyst stage was observed. In addition, when oocytes receiving a small Ca(2+) stimulus were further activated by higher concentration of TPEN (100-200 μM), a significant increase in the frequency of blastocyst formation was observed, compared to a conventional activation method. This result indicated that TPEN can be a main reagent in oocyte activation. No increase in the cytosolic Ca(2+) level was detected when oocytes were exposed to various concentrations of TPEN, indicating the ability of TPEN to induce oocyte activation is independent of an intracellular Ca(2+) increase. We were able to produce clones through SCNT by using the TPEN-assisted activation procedure, and the piglets produced through the process did not show any signs of abnormality. In this study, we have developed an efficient way to use TPEN to increase the developmental potential of cloned embryos.

Targeted disruption of CD1d prevents NKT cell development in pigs

Studies in mice genetically lacking natural killer T (NKT) cells show that these lymphocytes make important contributions to both innate and adaptive immune responses. However, the usefulness of murine models to study human NKT cells is limited by the many differences between mice and humans, including that their NKT cell frequencies, subsets, and distribution are dissimilar. A more suitable model may be swine that share many metabolic, physiological, and growth characteristics with humans and are also similar for NKT cells. Thus, we analyzed genetically modified pigs made deficient for CD1d that is required for the development of Type I invariant NKT (iNKT) cells that express a semi-invariant T-cell receptor (TCR) and Type II NKT cells that use variable TCRs. Peripheral blood analyzed by flow cytometry and interferon-γ enzyme-linked immuno spot assays demonstrated that CD1d-knockout pigs completely lack iNKT cells, while other leukocyte populations remain intact. CD1d and NKT cells have been shown to be involved in shaping the composition of the commensal microbiota in mice. Therefore, we also compared the fecal microbiota profile between pigs expressing and lacking NKT cells. However, no differences were found between pigs lacking or expressing CD1d. Our results are the first to show that knocking-out CD1d prevents the development of NKT cells in a non-rodent species. CD1d-deficient pigs should offer a useful model to more accurately determine the contribution of NKT cells for human immune responses. They also have potential for understanding how NKT cells impact the health of commercial swine.

Impairment of preimplantation porcine embryo development by histone demethylase KDM5B knockdown through disturbance of bivalent H3K4me3-H3K27me3 modifications

KDM5B (JARID1B/PLU1) is a H3K4me2/3 histone demethylase that is implicated in cancer development and proliferation and is also indispensable for embryonic stem cell self-renewal, cell fate, and murine embryonic development. However, little is known about the role of KDM5B during preimplantation embryo development. Here we show that KDM5B is critical to porcine preimplantation development. KDM5B was found to be expressed in a stage-specific manner, consistent with demethylation of H3K4me3, with the highest expression being observed from the 4-cell to the blastocyst stages. Knockdown of KDM5B by morpholino antisense oligonucleotides injection impaired porcine embryo development to the blastocyst stage. The impairment of embryo development might be caused by increased expression of H3K4me3 at the 4-cell and blastocyst stages, which disturbs the balance of bivalent H3K4me3-H3K27me3 modifications at the blastocyst stage. Decreased abundance of H3K27me3 at blastocyst stage activates multiple members of homeobox genes (HOX), which need to be silenced for faithful embryo development. Additionally, the histone demethylase KDM6A was found to be upregulated by knockdown of KDM5B, which indicated it was responsible for the decreased abundance of H3K27me3 at the blastocyst stage. The transcriptional levels of Ten-Eleven Translocation gene family members (TET1, TET2, and TET3) are found to be increased by knockdown of KDM5B, which indicates cross talk between histone modifications and DNA methylation. The studies above indicate that KDM5B is required for porcine embryo development through regulating the balance of bivalent H3K4me3-H3K27me3 modifications.

Oxamflatin treatment enhances cloned porcine embryo development and nuclear reprogramming

Faulty epigenetic reprogramming of somatic nuclei is thought to be the main reason for low cloning efficiency by somatic cell nuclear transfer (SCNT). Histone deacetylase inhibitors (HDACi), such as Scriptaid, improve developmental competence of SCNT embryos in several species. Another HDACi, Oxamflatin, is about 100 times more potent than Scriptaid in the ability to inhibit nuclear-specific HDACs. The present study determined the effects of Oxamflatin treatment on embryo development, DNA methylation, and gene expression. Oxamflatin treatment enhanced blastocyst formation of SCNT embryos in vitro. Embryo transfer produced more pigs born and fewer mummies from the Oxamflatin-treated group compared to the Scriptaid-treated positive control. Oxamflatin also decreased DNA methylation of POU5F1 regulatory elements and centromeric repeat elements in day-7 blastocysts. When compared to in vitro-fertilized (IVF) embryos, the methylation status of POU5F1, NANOG, and centromeric repeat was similar in the cloned embryos, indicating these genes were successfully reprogrammed. However, compared to the lack of methylation of XIST in day-7 IVF embryos, a higher methylation level in day-7 cloned embryos was observed, implying that X chromosomes were activated in day-7 IVF blastocysts, but were not fully activated in cloned embryos, i.e., reprogramming of XIST was delayed. A time-course analysis of XIST DNA methylation on day-13, -15, -17, and -19 in vivo embryos revealed that XIST methylation initiated at about day 13 and was not completed by day 19. The methylation of the XIST gene in day-19 control cloned embryos was delayed again when compared to in vivo embryos. However, methylation of XIST in Oxamflatin-treated embryos was comparable with in vivo embryos, which further demonstrated that Oxamflatin could accelerate the delayed reprogramming of XIST gene and thus might improve cloning efficiency.

Use of the CRISPR/Cas9 system to produce genetically engineered pigs from in vitro-derived oocytes and embryos

Targeted modification of the pig genome can be challenging. Recent applications of the CRISPR/Cas9 system hold promise for improving the efficacy of genome editing. When a designed CRISPR/Cas9 system targeting CD163 or CD1D was introduced into somatic cells, it was highly efficient in inducing mutations. When these mutated cells were used with somatic cell nuclear transfer, offspring with these modifications were created. When the CRISPR/Cas9 system was delivered into in vitro produced presumptive porcine zygotes, the system was effective in creating mutations in eGFP, CD163, and CD1D (100% targeting efficiency in blastocyst stage embryos); however, it also presented some embryo toxicity. We could also induce deletions in CD163 or CD1D by introducing two types of CRISPRs with Cas9. The system could also disrupt two genes, CD163 and eGFP, simultaneously when two CRISPRs targeting two genes with Cas9 were delivered into zygotes. Direct injection of CRISPR/Cas9 targeting CD163 or CD1D into zygotes resulted in piglets that have mutations on both alleles with only one CD1D pig having a mosaic genotype. We show here that the CRISPR/Cas9 system can be used by two methods. The system can be used to modify somatic cells followed by somatic cell nuclear transfer. System components can also be used in in vitro produced zygotes to generate pigs with specific genetic modifications.

Interaction of photoperiod and vernalization determines flowering time of Brachypodium distachyon

Timing of flowering is key to the reproductive success of many plants. In temperate climates, flowering is often coordinated with seasonal environmental cues such as temperature and photoperiod. Vernalization is an example of temperature influencing the timing of flowering and is defined as the process by which a prolonged exposure to the cold of winter results in competence to flower during the following spring. In cereals, three genes (VERNALIZATION1 [VRN1], VRN2, and FLOWERING LOCUS T [FT]) have been identified that influence the vernalization requirement and are thought to form a regulatory loop to control the timing of flowering. Here, we characterize natural variation in the vernalization and photoperiod responses in Brachypodium distachyon, a small temperate grass related to wheat (Triticum aestivum) and barley (Hordeum vulgare). Brachypodium spp. accessions display a wide range of flowering responses to different photoperiods and lengths of vernalization. In addition, we characterize the expression patterns of the closest homologs of VRN1, VRN2 (VRN2-like [BdVRN2L]), and FT before, during, and after cold exposure as well as in different photoperiods. FT messenger RNA levels generally correlate with flowering time among accessions grown in different photoperiods, and FT is more highly expressed in vernalized plants after cold. VRN1 is induced by cold in leaves and remains high following vernalization. Plants overexpressing VRN1 or FT flower rapidly in the absence of vernalization, and plants overexpressing VRN1 exhibit lower BdVRN2L levels. Interestingly, BdVRN2L is induced during cold, which is a difference in the behavior of BdVRN2L compared with wheat VRN2 during cold.

An organic acid based counter selection system for cyanobacteria

Cyanobacteria are valuable organisms for studying the physiology of photosynthesis and carbon fixation, as well as metabolic engineering for the production of fuels and chemicals. This work describes a novel counter selection method for the cyanobacterium Synechococcus sp. PCC 7002 based on organic acid toxicity. The organic acids acrylate, 3-hydroxypropionate, and propionate were shown to be inhibitory towards Synechococcus sp. PCC 7002 and other cyanobacteria at low concentrations. Inhibition was overcome by a loss of function mutation in the gene acsA, which is annotated as an acetyl-CoA ligase. Loss of AcsA function was used as a basis for an acrylate counter selection method. DNA fragments of interest were inserted into the acsA locus and strains harboring the insertion were isolated on selective medium containing acrylate. This methodology was also used to introduce DNA fragments into a pseudogene, glpK. Application of this method will allow for more advanced genetics and engineering studies in Synechococcus sp. PCC 7002 including the construction of markerless gene deletions and insertions. The acrylate counter-selection could be applied to other cyanobacterial species where AcsA activity confers acrylate sensitivity (e.g. Synechocystis sp. PCC 6803).

Advancing swine models for human health and diseases

Swine models are relatively new kids on the block for modeling human health and diseases when compared to rodents and dogs. Because of the similarity to humans in size, physiology, and genetics, the pig has made significant strides in advancing the understanding of the human condition, and is thus an excellent choice for an animal model. Recent technological advances to genetic engineering of the swine genome enhance the utility of swine as models of human genetic diseases.

The cryobiology of spermatozoa

The impact of successful cryopreservation of spermatozoa can be found in many fields, including agriculture, laboratory animal medicine, and human assisted reproduction, providing a cost-effective and efficient method to preserve genetic material for decades. The success of any cryobiologic protocol depends critically on understanding the fundamentals that underlie the process. In this review, we summarize the biophysical fundamentals critical to much of the research in sperm cryobiology, provide a synopsis of the development of sperm cryobiology as a discipline, and present the current state and directions for future research in sperm cryobiology in the three major areas outlined above-agriculture, laboratory animal medicine, and human clinical assisted reproduction. There is much room for new research, both empiric and fundamental, in all areas, including refinement of mathematical models, optimization of cryoprotective agent addition and removal procedures for spermatozoa from many species, development of effective, efficient, and facile cryopreservation protocols and freezing containers for agricultural sperm cryopreservation, and tailoring cryopreservation protocols for individual human samples.

Xenopus egg extract treatment reduced global DNA methylation of donor cells and enhanced somatic cell nuclear transfer embryo development in pigs

The efficiency to produce offspring by somatic cell nuclear transfer (SCNT) is low. It has been showed that treatment of donor cells with Xenopus oocyte extract increased live births in ovine and handmade cloned embryo development in pigs. Scriptaid treatment after oocyte activation is another approach to improve SCNT efficiency. The present study was carried out to investigate (a) the effects of treatment of donor cells with Xenopus egg extract on donor cell DNA methylation at days 0 and 4 with two digitonin permeabilization concentrations (10 and 15 μg/mL), (b) the effects of treatment of donor cells with Xenopus egg extract on early development of cloned embryos, and (c) the effects of combined treatments, treating donor cells with extract before nuclear transfer and treatment of cloned embryos with scriptaid after oocyte activation, on embryo development. Compared to the control, a decrease of DNA methylation in donor cells was observed at 2.5 h after extract treatment. However, this effect was not observed after the cells were cultured for four more days. More embryos developed into blastocysts in the Xenopus egg extract-treated group than in the control (13.4±1.9% vs. 9.1±1.9%, p=0.01). Furthermore, scriptaid treatment of cloned embryos further increased the frequency of development to blastocyst, compared to the control reconstructed with the same extract-treated cells (22.5±0.9% vs. 15.3±0.9%, p<0.01). In addition, egg extract treatments increased the cell number in the blastocysts. This study demonstrated that Xenopus egg extract treatment reduced donor cell DNA methylation and enhanced the SCNT embryo development. Moreover, the combined treatments of donor cells with egg extract before nuclear transfer and of cloned embryos with scriptaid could improve cloned embryo development additively.

Completion of the swine genome will simplify the production of swine as a large animal biomedical model

Background

Anatomic and physiological similarities to the human make swine an excellent large animal model for human health and disease.

Methods

Cloning from a modified somatic cell, which can be determined in cells prior to making the animal, is the only method available for the production of targeted modifications in swine.

Results

Since some strains of swine are similar in size to humans, technologies that have been developed for swine can be readily adapted to humans and vice versa. Here the importance of swine as a biomedical model, current technologies to produce genetically enhanced swine, current biomedical models, and how the completion of the swine genome will promote swine as a biomedical model are discussed.

Conclusions

The completion of the swine genome will enhance the continued use and development of swine as models of human health, syndromes and conditions.

Effects of combined treatment of MG132 and scriptaid on early and term development of porcine somatic cell nuclear transfer embryos

Although improving, the efficiency of producing offspring by somatic cell nuclear transfer (SCNT) is still low (<1.5%). Our laboratory has demonstrated that histone deacetylase inhibitor (Scriptaid) treatment of reconstructed embryos enhances blastocyst formation and cloning efficiency in pigs. It has also been shown that proteasomal inhibitor MG132 treatment for 2 h after activation of oocytes increases blastocyst rate and pregnancy rate. The current experiment was carried out to determine the effects of combined MG132 and Scriptaid treatment on early embryo development in vitro and on term development in vivo. Immediately after electrofusion and activation, SCNT oocytes were treated with 0, 1, or 10 μM MG132 for 2 h in the presence of 500 nM Scriptaid, washed and treated with Scriptaid for an additional 14 to 15 h, then cultured in porcine zygote medium 3 (PZM3) until day 6. There was no difference in percent cleavage (58.1 ± 7.2%, 62.7 ± 7.2%, and 62.5 ± 7.2%) on day 2, or total cell number (23.1 ± 2.2, 24.0 ± 2.0, and 24.5 ± 2.3 for the 0, 1, and 10 μM MG132 groups, respectively) on day 6 among the three groups. Interestingly, there was no difference in percentage of blastocysts between the 0 (18.5±4.7%) and 1 (25.1 ± 4.7%) μM MG132 treatment groups; however, compared with the 10 μM MG132 group (14.0 ± 4.7%), more embryos from the 1 μM MG132 group developed into blastocysts (p<0.05). To determine the effects on term development in vivo, two MG132 groups were included (0 and 1 μM MG132), and embryos were treated as above and transferred into synchronized surrogates after treatment. There was no difference in the oocyte-donor cell fusion rate, number of embryos transferred, pregnancy rate at days 28, 60, and at term, pigs delivered per embryo transfer, litter size, body weight at birth, nor cloning efficiency between the Scriptaid-alone control and MG132+Scriptaid combined groups. In summary, the combined treatment of MG132 and Scriptaid did not improve term development compared to Scriptaid treatment alone.

Emerging applications of sperm, embryo and somatic cell cryopreservation in maintenance, relocation and rederivation of swine genetics

Advances in porcine assisted reproductive technology (ART) make it possible to use cryopreserved sperm, embryos and somatic cells in the maintenance, relocation and regeneration of swine genetics. In this review, development of key application-limiting technology is discussed in each cell type, focusing on the efficiencies, ease of storage and transportation, and minimization of pathogen transmission. Methods to regenerate swine genetics and/or models using frozen sperm, embryos and somatic cells in combination with other porcine ARTs, such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and somatic cell nuclear transplantation (SCNT), are also discussed. The applications of these ARTs utilizing cryopreserved cells will greatly increase the efficiency as well as biosecurity for maintenance, relocation and rederivation of swine genetics/models.

Regulation of oocyte mitochondrial DNA copy number by follicular fluid, EGF, and neuregulin 1 during in vitro maturation affects embryo development in pigs

Little is known about mitochondrial DNA (mtDNA) replication during oocyte maturation and its regulation by extracellular factors. The present study determined the effects of supplementation of maturation medium with porcine follicular fluid (pFF; 0, 10%, 20%, and 30%) on mtDNA copy number and oocyte maturation in experiment 1; the effects on epidermal growth factor (EGF; 10 ng/mL), neuregulin 1 (NRG1; 20 ng/mL), and NRG1 + insulin-like growth factor 1 (IGF1; 100 ng/mL + NRG1 20 ng/mL), on mtDNA copy number, oocyte maturation, and embryo development after parthenogenic activation in experiment 2; and effects on embryo development after in vitro fertilization in experiment 3. Overall, mtDNA copy number increased from germinal vesicle (GV) to metaphase II (MII) stage oocytes after in vitro maturation (GV: 167 634.6 ± 20 740.4 vs. MII: 275 131.9 ± 9 758.4 in experiment 1; P < 0.05; GV: 185 004.7 ± 20 089.3 vs. MII: 239 392.8 ± 10 345.3 in experiment 2; P < 0.05; Least Squares Means ± SEM). Supplementation of IVM medium with pFF inhibited mtDNA replication (266 789.9 ± 11 790.4 vs. 318 510.1 ± 20 377.4; P < 0.05) and oocyte meiotic maturation (67.3 ± 0.7% vs. 73.2 ± 1.2%, for the pFF supplemented and zero pFF control, respectively; P < 0.01). Compared with the control, addition of growth factors enhanced oocyte maturation. Furthermore, supplementation of NRG1 stimulated mitochondrial replication, increased mtDNA copies in MII oocytes than in GV oocytes, and increased percentage of blastocysts in both parthenogenetic and in vitro fertilized embryos. In this study, mitochondrial biogenesis in oocytes was stimulated during in vitro maturation. Oocyte mtDNA copy number was associated with developmental competence. Supplementation of maturation medium with NRG1 increased mtDNA copy number, and thus provides a means to improve oocyte quality and developmental competence in pigs.

Animal models got you puzzled?: think pig

Swine are an excellent large animal model for human health and disease because their size and physiology are similar to humans, in particular, with respect to the skin, heart, gastrointestinal tract, and kidneys. In addition, the pig has many emerging technologies that will only enhance the development of the pig as the nonrodent biomedical model of choice.

THE PIG AS A BIOMEDICAL MODEL: HOW THE NATIONAL SWINE RESOURCE AND RESEARCH CENTER CAN HELP YOU

Swine are an excellent large animal model for human health and disease because their size and physiology are similar to humans, and the progression of many diseases, such as cardiovascular disease, is similar to humans. Due to these similarities, technology, procedures, and novel treatments that have been developed for human diseases can be applied to swine, and vice versa. In addition there are some human diseases, such as cystic fibrosis, that don't recapitulate in the rodent models but are well modeled in swine. Swine have been accepted as the model of choice for several medical applications such as xenotransplantation and surgical training for medical students. Because of the usefulness of swine to better understand human health, the National Institutes of Health has established the National Swine Research and Resource Center to help meet the needs of the biomedical community. While wild type swine and spontaneous mutants have been shown to be valuable, genetically engineered swine provide a new level of utility. With the improvement of the techniques to add genes and make targeted genetic modifications not only have the number of types of genetically engineered pigs increased, but also the number of different diseases modeled have increased. The completion of the swine genome combined with development and improvements of techniques for gene modification will only enhance the continued use and development of swine as models of human health, syndromes and conditions. The resources at the National Swine Resource and Research Center are available to aid investigators with their swine needs for biomedical research. Here will be discussed the importance of swine as a biomedical model, current technologies to produce genetically engineered swine, current biomedical models, and how the completion of the swine genome will promote swine as a biomedical model.

Birth of piglets from in vitro-produced, zona-intact porcine embryos vitrified in a closed system

As the importance of swine models in biomedical research increases, it is essential to develop low-cost, high-throughput systems to cryopreserve swine germplasm for maintenance of these models. However, porcine embryos are exceedingly sensitive to low temperature and successful cryopreservation is generally limited to the use of vitrification in open systems that allow direct contact of the embryos with liquid nitrogen (LN(2)). This creates a high risk of pathogen transmission. Therefore, cryopreservation of porcine embryos in a "closed" system is of very high importance. In this study, in vitro-produced (IVP) porcine embryos were used to investigate cryosurvival and developmental potential of embryos cryopreserved in a closed system. Optimal centrifugal forces to completely disassociate intracellular lipids from blastomeres were investigated using Day-4 embryos. Cryosurvival of delipidated embryos was investigated by vitrifying the embryos immediately after centrifugation, or after development to blastocysts. In this study, centrifugation for 30 min at 13,000 g was adequate to completely delipidate the embryos; furthermore, these embryos were able to survive cryopreservation at a rate comparable to those centrifuged for only 12 min. When delipidated embryos were vitrified at the blastocyst stage, there was no difference in survival between embryos vitrified using OPS and 0.25 mL straws. Some embryos vitrified by each method developed to term. These experiments demonstrated that porcine embryos can be cryopreserved in a closed system after externalizing their intracellular lipids. This has important implications for banking swine models of human health and disease.

Histone deacetylase inhibitors improve in vitro and in vivo developmental competence of somatic cell nuclear transfer porcine embryos

Faulty epigenetic reprogramming of somatic nuclei is likely to be a major cause of low success observed in all mammals produced through somatic cell nuclear transfer (SCNT). It has been demonstrated that the developmental competence of SCNT embryos in several species were significantly enhanced via treatment of histone deacetylase inhibitors (HDACi) such as trichostatin A (TSA) to increase histone acetylation. Here we report that 50 nM TSA for 10 h after activation increased the developmental competence of porcine SCNT embryos constructed from Landrace fetal fibroblast cells (FFCs) in vitro and in vivo, but not at higher concentrations. Therefore, we optimized the application of another novel HDACi, Scriptaid, for development of porcine SCNT embryos. We found that treatment with 500 nM Scriptaid significantly enhanced the development SCNT embryos to the blastocyst stage when outbred Landrace FFCs and ear fibroblast cells (EFCs) were used as donors compared to the untreated group. Scriptaid increased the overall cloning efficiency from 0.4% (untreated group) to 1.6% for Landrace FFCs and 0 to 3.7% for Landrace EFCs. Moreover, treatment of SCNT embryos with Scriptaid improved the histone acetylation on Histone H4 at lysine 8 (AcH4K8) in a pattern similar to that of the in vitro fertilized (IVF) embryos.

Mutational insertion of a ROSA26-EGFP transgene leads to defects in spermiogenesis and male infertility in mice

Pronuclear injection has been a successful strategy for generating genetically engineered mouse models to better understand the functionality of genes. A characteristic of pronuclear injection is that random integration of the transgene into the genome can disturb a functional gene and result in a phenotype unrelated to the transgene itself. In this study, we have characterized a mouse model containing an insertional mutation that, in the homozygous state, severely affects spermatogenesis as characterized by lack of sperm motility and acrosomal aplasia. Whereas homozygous female mice had normal fertility, male mice homozygous for the insertional mutation were unable to produce pups by natural mating with either homozygous or wild-type female mice. No fertilized embryos were produced by matings to homozygous male mice, and no sperm were present in the reproductive tract of mated female mice. Spermatozoa isolated from homozygous male mice exhibited head and midpiece defects, but no major defects in the principal piece of these sperm. Histologic examination and immunohistochemical staining of the testes revealed vacuolar degeneration of Sertoli cells and loss of structural seminiferous tubule integrity and organization, indicating that spermatogenesis is severely affected in this mouse model. Although the males are always infertile, the severity of the histologic and sperm morphologic defects appeared to be age-related.

Significant improvement in cloning efficiency of an inbred miniature pig by histone deacetylase inhibitor treatment after somatic cell nuclear transfer

The National Institutes of Health (NIH) miniature pig was developed specifically for xenotransplantation and has been extensively used as a large-animal model in many other biomedical experiments. However, the cloning efficiency of this pig is very low (<0.2%), and this has been an obstacle to the promising application of these inbred swine genetics for biomedical research. It has been demonstrated that increased histone acetylation in somatic cell nuclear transfer (SCNT) embryos, by applying a histone deacetylase (HDAC) inhibitor such as trichostatin A (TSA), significantly enhances the developmental competence in several species. However, some researchers also reported that TSA treatment had various detrimental effects on the in vitro and in vivo development of the SCNT embryos. Herein, we report that treatment with 500 nM 6-(1,3-dioxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid hydroxyamide (termed scriptaid), a novel HDAC inhibitor, significantly enhanced the development of SCNT embryos to the blastocyst stage when NIH inbred fetal fibroblast cells (FFCs) were used as donors compared with the untreated group (21% vs. 9%, P < 0.05). Scriptaid treatment resulted in eight pregnancies from 10 embryo transfers (ETs) and 14 healthy NIH miniature pigs from eight litters, while no viable piglets (only three mummies) were obtained from nine ETs in the untreated group. Thus, scriptaid dramatically increased the cloning efficiency when using inbred genetics from 0.0% to 1.3%. In contrast, scriptaid treatment decreased the blastocyst rate in in vitro fertilization embryos (from 37% to 26%, P < 0.05). In conclusion, the extremely low cloning efficiency in the NIH miniature pig may be caused by its inbred genetic background and can be improved by alteration of genomic histone acetylation patterns.

Production of piglets after cryopreservation of embryos using a centrifugation-based method for delipation without micromanipulation

It is still difficult to successfully cryopreserve in vitro-produced (IVP) swine embryos, as they are sensitive to chilling due to the abundance of intracellular lipids. Mechanical delipation through micromanipulation is successful, but this method increases the potential of pathogen transmission because of the damage inflicted upon the zona pellucida during micromanipulation, and it is labor intensive. Reported here is a method to remove the lipid of IVP porcine embryos, without significantly compromising the zona pellucida, by trypsin treating the embryos or exposing the embryo to a high-osmolality solution to enlarge the perivitelline space so that the lipid could be polarized and separated completely after subsequent centrifugation without micromanipulation. The procedures work both for nuclear transfer-derived embryos and in vitro-fertilized embryos. Both methods provide a high-throughput process that leaves the zona pellucida intact (or relatively intact for the trypsin treatment) to aid in preventing disease transmission. It is also demonstrated that this procedure results in viable piglets, a claim that could not be made in many previous reports. Although the efficiencies of cryopreservation have not been dramatically improved, these procedures allow a single person to process very large numbers of embryos without the necessity of manipulating each individual embryo on a micromanipulator. Such high-throughput processing overcomes the lack of high efficiency (i.e., the system can be overloaded with embryos for transfer to surrogates).

Toward culture of single gametes: the development of microfluidic platforms for assisted reproduction

During the last few decades in vitro production of mammalian embryos and assisted reproductive technologies such as embryo transfer, cryopreservation, and cloning have been used to produce and propagate genetically superior livestock. However, efficiencies of these technologies remain low. For these technologies to become more commercially viable, the efficiencies must improve. Despite this importance of reproduction for the livestock industry, little progress in decreasing embryonic mortality has been made. The livestock industry has succeeded in achieving large increases in average milk production of dairy cattle, growth rate in beef cattle and leanness in swine but reproductive efficiency has actually decreased. For example, research has provided little progress toward developing an objective method to examine viability of a single living embryo. At the same time, the growth of miniaturization technologies beyond integrated circuits and toward small mechanical systems has created opportunities for fresh examination of a wide range of existing problems. While the investigation and application of miniaturization technologies to medicine and biology is progressing rapidly, there has been limited exploration of microfabricated systems in the area of embryo production. Microfluidics is an emerging technology that allows a fresh examination of the way assisted reproduction is performed. Here we review the progress in demonstrating microfluidic systems for in vitro embryo production (IVP) and embryo manipulation. Microfluidic technology could have a dramatic impact on the development of new techniques as well as on our basic understanding of gamete and embryo physiology.

Estrogenic effects of genistein on reproductive tissues of ovariectomized gilts1

The soybean phytoestrogen genistein has a range of estrogenic actions demonstrated in various species; however, only limited research has been done to investigate its effects in swine. The objective of this study was to characterize the effects of a graded dose of genistein on estrogen-sensitive uterine and cervical tissues in ovariectomized gilts. Thirty-four postpubertal gilts were ovariectomized and assigned randomly to 1 of 6 treatment groups 15 d postovariectomy. Treatment groups received vehicle, estradiol benzoate (2 mg/d), or genistein (50, 100, 200, or 400 mg/d) via intramuscular injection at 12-h intervals for 10 d. Following the treatment period, gilts were euthanized, and uterine and cervical tissues were collected and processed for chemical or histological analysis. Uterine and cervical tissue mass, as indicated by wet, dry, and protein weights and total DNA content (expressed per 100 kg of BW), increased as the dosage of genistein increased (P < 0.001 for each regression). Uterine and cervical wet weights were increased by a dosage of 200 mg of genistein/d (P < 0.001 and P < 0.01, respectively) but not by 100 mg of genistein/d (P = 0.38 and P = 0.14, respectively) compared with those of control gilts. Height of epithelial cells lining the uterine glands and the lumen of uterus and cervix increased when gilts were treated with estradiol benzoate or 400 mg of genistein/d (P < 0.01). When the gilts were treated with estradiol benzoate or 400 mg of genistein/d, immunohistochemical staining demonstrated an increase in the percentage of cells that stained positive for progesterone receptor in the uterine glands and in the cells lining the vaginal cervix (P < 0.05). In gilts treated with 400 mg of genistein/d, the percentage of cells stained positive for proliferating cell nuclear antigen increased in the epithelium of the uterine glands, uterine lumen, and vaginal cervix (P < 0.05). Tissue growth was stimulated by genistein in a dosage-dependent manner, although no dosage of genistein induced a response as great as that of estradiol benzoate. Estrogen-sensitive tissues of the ovariectomized gilt, such as the cervix and uterus, are affected by injection of large dosages of the phytoestrogen genistein. The sensitivity of the uterus of the gilt to estrogenic substances makes it a potential model to examine the impact of environmental endocrine modulators on reproductive tissues.

Osmotic tolerance of mouse spermatozoa from various genetic backgrounds: acrosome integrity, membrane integrity, and maintenance of motility

All cells have an intrinsic biophysical property related to their ability to undergo osmotically driven volume changes. This project is of fundamental importance to our understanding of the basic cryobiology of mouse spermatozoa. The objectives of this study were to determine the osmotic tolerance limits for (1) motility, (2) acrosome integrity, and (3) membrane integrity of mouse spermatozoa from multiple genetic backgrounds including: C57BL/6, BALB/c, FVB, C3H, 129/SVS2 hsd B6C3F1, CB6F1, and ICR. The maintenance of acrosomal and plasma membrane integrity was not affected by genetic background (p=0.13), however, there was an interaction between genetic background and osmolality. In addition, acrosome and plasma membrane integrity was highly correlated within each strain (p<0.01). In contrast to acrosome and plasma membrane integrity, the motility of spermatozoa from different genetic backgrounds fell sharply on both sides of isosmolality, both with and without return to isosmotic conditions. Exposure to hyposmotic conditions caused morphological changes in the spermatozoa, which inhibited motility. However, this morphological change was not reversible in all cases when returned to isosmotic conditions. The ability to maintain motility in an anisosmotic media was affected by genetic background, osmolality as well as the interaction between genetic background and osmolality (p<0.05). In conclusion, mice with different genetic backgrounds appear to have similar tolerance to osmotic changes in terms of sperm acrosome and plasma membrane integrity; however, the ability to maintain motility differs between genetic backgrounds.

Embryonic development in the mouse is enhanced via microchannel culture

Microfluidic devices (microchannels) have been fabricated and tested for embryo culture. Three different microfabrication materials (silicon, polydimethylsiloxane (PDMS), and borosilicate) were used to fabricate the microchannels. The objective of this study was to determine if static microchannels permitted culture of mouse embryos to the blastocyst stage. Groups of 10 two-cell ICR x B6SJL/F1 mouse embryos were cultured for 96 hours in 4 different physical culture systems: 1) silicon/borosilicate microchannels, 2) PDMS/borosilicate microchannels, and 3) standard microdrops. Embryos cultured in the silicon/borosilicate and PDMS/borosilicate microchannels exhibited a faster rate of cleavage (P < 0.05), and produced more blastocysts (P < 0.01) than control microdrops. Furthermore, microchannels had a lower percentage of degenerated embryos than control embryos (P < 0.01). The results suggest that the microchannel culture systems may provide a culture environment that more closely mimics the in vivo environment.

Transgenic animals in biomedicine and agriculture: outlook for the future

Transgenic animals are produced by introduction of 'foreign' deoxyribonucleic acid (DNA) into preimplantation embryos. The foreign DNA is inserted into the genetic material and may be expressed in tissues of the resulting individual. This technique is of great importance to many aspects of biomedical science including gene regulation, the immune system, cancer research, developmental biology, biomedicine, manufacturing and agriculture. The production of transgenic animals is one of a number of new and developing technologies that will have a profound impact on the genetic improvement of livestock. The rate at which these technologies are incorporated into production schemes will determine the speed at which we will be able to achieve our goal of more efficiently producing livestock, which meets consumer and market demand.

Use of energy substrates by various stage preimplantation pig embryos produced in vivo and in vitro

The aim of in vitro embryo systems is to produce embryos of comparable quality to those derived in vivo. Comparison of embryo metabolism as an indicator of viability may be useful in optimization of culture conditions. The aim of the present study was to determine glucose, glutamine and pyruvate use by various stage pig embryos produced in vitro and in vivo. The results indicate that pig embryos use glucose via glycolysis in significant amounts at all stages examined, regardless of embryo origin. In vitro-derived embryos have significantly increased glycolytic activity after the eight-cell stage, whereas in vivo-derived embryos have increased glycolysis at the blastocyst stage. In vivo-derived embryos have higher rates of glycolysis compared with in vitro-derived embryos. Glucose usage through the Krebs cycle for in vitro- and in vivo-derived embryos increased significantly at the blastocyst stage. Pig embryos produced in vitro used constant amounts of glutamine throughout development, whereas in vivo-derived embryos increased glutamine usage after the eight-cell stage. Pyruvate use was minimal at all stages examined for both in vitro- and in vivo-derived pig embryos, showing significant increases at the blastocyst stage. Krebs cycle metabolism of pyruvate, glutamine and glucose by in vivo-derived embryos was higher than that by in vitro-derived embryos. Current in vitro culture conditions produce pig embryos with altered metabolic activity, which may compromise embryo viability.

Use of energy substrates by various stage preimplantation pig embryos produced in vivo and in vitro

The aim of in vitro embryo systems is to produce embryos of comparable quality to those derived in vivo. Comparison of embryo metabolism as an indicator of viability may be useful in optimization of culture conditions. The aim of the present study was to determine glucose, glutamine and pyruvate use by various stage pig embryos produced in vitro and in vivo. The results indicate that pig embryos use glucose via glycolysis in significant amounts at all stages examined, regardless of embryo origin. In vitro-derived embryos have significantly increased glycolytic activity after the eight-cell stage, whereas in vivo-derived embryos have increased glycolysis at the blastocyst stage. In vivo-derived embryos have higher rates of glycolysis compared with in vitro-derived embryos. Glucose usage through the Krebs cycle for in vitro- and in vivo-derived embryos increased significantly at the blastocyst stage. Pig embryos produced in vitro used constant amounts of glutamine throughout development, whereas in vivo-derived embryos increased glutamine usage after the eight-cell stage. Pyruvate use was minimal at all stages examined for both in vitro- and in vivo-derived pig embryos, showing significant increases at the blastocyst stage. Krebs cycle metabolism of pyruvate, glutamine and glucose by in vivo-derived embryos was higher than that by in vitro-derived embryos. Current in vitro culture conditions produce pig embryos with altered metabolic activity, which may compromise embryo viability.

Transgenic technology and applications in swine

The introduction of foreign DNA into the genome of livestock and its stable integration into the germ line has been a major technical advance in agriculture. Production of transgenic livestock provides a method to rapidly introduce "new" genes into cattle, swine, sheep and goats without crossbreeding. It is a more extreme methodology, but in essence, not really different from crossbreeding or genetic selection in its result. Several recent developments will profoundly impact the use of transgenic technology in livestock production. These developments are: 1) the ability to isolate and maintain in vitro embryonic stem (ES) cells from preimplantation embryos, embryonic germ (EG) and somatic cells from fetuses; and somatic cells from adults, and 2) the ability to use these embryonic and somatic cells as nuclei donors in nuclear transfer or "cloning" strategies. Cell based (ES, EG, and somatic cells) strategies have several distinct advantages for use in the production of transgenic livestock that cannot be attained using pronuclear injection of DNA. There are many potential applications of transgenic methodology to develop new and improved strains of livestock. Practical applications of transgenesis in livestock production include enhanced prolificacy and reproductive performance, increased feed utilization and growth rate, improved carcass composition, improved milk production and/or composition and increased disease resistance. Development of transgenic farm animals will allow more flexibility in direct genetic manipulation of livestock.