Transgenic-cloned pigs systemically expressing red fluorescent protein, Kusabira-Orange

Generation of heterozygous PKD1 mutant pigs exhibiting early-onset renal cyst formation

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease, manifesting as the progressive development of fluid-filled renal cysts. In approximately half of all patients with ADPKD, end-stage renal disease results in decreased renal function. In this study, we used CRISPR-Cas9 and somatic cell cloning to produce pigs with the unique mutation c.152_153insG (PKD1^insG/+). Pathological analysis of founder cloned animals and progeny revealed that PKD1^insG/+ pigs developed many pathological conditions similar to those of patients with heterozygous mutations in PKD1. Pathological similarities included the formation of macroscopic renal cysts at the neonatal stage, number and cystogenic dynamics of the renal cysts formed, interstitial fibrosis of the renal tissue, and presence of a premature asymptomatic stage. Our findings demonstrate that PKD1^insG/+ pigs recapitulate the characteristic symptoms of ADPKD.

Investigation of Clinical Safety of Human iPS Cell-Derived Liver Organoid Transplantation to Infantile Patients in Porcine Model

Transplantation of liver organoids has been investigated as a treatment alternative to liver transplantation for chronic liver disease. Transportal approach can be considered as a method of delivering organoids to the liver. It is important to set the allowable organoid amount and verify translocation by intraportal transplantation. We first examined the transplantation tolerance and translocation of porcine fetal liver-derived allogeneic organoids using piglets. Fetal liver-derived organoids generated from the Kusabira Orange-transduced pig were transplanted to the 10-day-old piglet liver through the left branch of the portal vein. All recipients survived without any observable adverse events. In contrast, both local and main portal pressures increased transiently during transplantation. In necropsy samples, Kusabira Orange-positive donor cells were detected primarily in the target lobe of the liver and partly in other areas, including the lungs and brain. As we confirmed the transplantation allowance by porcine fetal liver-derived organoids, we performed intraportal transplantation of human-induced pluripotent stem cell (iPSC)-derived liver organoid, which we plan to use in clinical trials, and portal pressure and translocation were investigated. Human iPSC-derived liver organoids were transplanted into the same 10-day-old piglet. Portal hypertension and translocation of human iPSC-derived liver organoids to the lungs were observed in one of two transplanted animals. Translocation occurred in the piglet in which patent ductus venosus (PDV) was observed. Therefore, a 28-day-old piglet capable of surgically ligating PDV was used, and after the PDV was ligated, human iPSC-derived liver organoids with the amount of which is scheduled in clinical trials were transplanted. This procedure inhibited the translocation of human iPSC-derived liver organoids to extrahepatic sites without no portal hypertension. In conclusion, human iPSC-derived liver organoids can be safely transplanted through the portal vein. Ligation of the ductus venosus prior to transplantation was effective in inhibiting extrahepatic translocation in newborns and infants.

Compensation of Disabled Organogeneses in Genetically Modified Pig Fetuses by Blastocyst Complementation

We have previously established a concept of developing exogenic pancreas in a genetically modified pig fetus with an apancreatic trait, thereby proposing the possibility of in vivo generation of functional human organs in xenogenic large animals. In this study, we aimed to demonstrate a further proof-of-concept of the compensation for disabled organogeneses in pig, including pancreatogenesis, nephrogenesis, hepatogenesis, and vasculogenesis. These dysorganogenetic phenotypes could be efficiently induced via genome editing of the cloned pigs. Induced dysorganogenetic traits could also be compensated by allogenic blastocyst complementation, thereby proving the extended concept of organ regeneration from exogenous pluripotent cells in empty niches during various organogeneses. These results suggest that the feasibility of blastocyst complementation using genome-edited cloned embryos permits experimentation toward the in vivo organ generation in pigs from xenogenic pluripotent cells.

Pigs with δ-sarcoglycan deficiency exhibit traits of genetic cardiomyopathy

Genetic cardiomyopathy is a group of intractable cardiovascular disorders involving heterogeneous genetic contribution. This heterogeneity has hindered the development of life-saving therapies for this serious disease. Genetic mutations in dystrophin and its associated glycoproteins cause cardiomuscular dysfunction. Large animal models incorporating these genetic defects are crucial for developing effective medical treatments, such as tissue regeneration and gene therapy. In the present study, we knocked out the δ-sarcoglycan (δ-SG) gene (SGCD) in domestic pig by using a combination of efficient de novo gene editing and somatic cell nuclear transfer. Loss of δ-SG expression in the SGCD knockout pigs caused a concomitant reduction in the levels of α-, β-, and γ-SG in the cardiac and skeletal sarcolemma, resulting in systolic dysfunction, myocardial tissue degeneration, and sudden death. These animals exhibited symptoms resembling human genetic cardiomyopathy and are thus promising for use in preclinical studies of next-generation therapies.

Generation of transgenic-cloned Huanjiang Xiang pigs systemically expressing enhanced green fluorescent protein

Huanjiang Xiang pig is a unique native minipig breed originating in Guangxi, China, and has great utility value in agriculture and biomedicine. Reproductive biotechnologies such as somatic cell nuclear transfer (SCNT) and SCNT-mediated genetic modification show great potential value in genetic preservation and utilization of Huanjiang Xiang pigs. Our previous work has successfully produced cloned and transgenic-cloned embryos using somatic cells from a Huanjiang Xiang pig. In this study, we firstly report the generation of transgenic-cloned Huanjiang Xiang pigs carrying an enhanced green fluorescent protein (eGFP) gene. A total of 504 SCNT-derived embryos were transferred to two surrogate recipients, one of which became pregnant and gave birth to three live piglets. Exogenous eGFP transgene had integrated in all of the three Huanjiang Xiang piglets identified by genotyping. Furthermore, expression of eGFP was also detected from in vitro cultured skin fibroblast cells and various organs or tissues from positive transgenic-cloned Huanjiang Xiang pigs. The present work provides a practical method to preserve this unique genetic resource and also lays a foundation for genetic modification of Huanjiang Xiang pigs with improved values in agriculture and biomedicine.

Establishment of DNA methylation patterns of the Fibrillin1 (FBN1) gene in porcine embryos and tissues

DNA methylation in transcriptional regulatory regions is crucial for gene expression. The DNA methylation status of the edges of CpG islands, called CpG island shore, is involved in tissue/cell-type-specific gene expression. Haploinsufficiency diseases are caused by inheritance of one mutated null allele and are classified as autosomal dominant. However, in the same pedigree, phenotypic variances are observed despite the inheritance of the identical mutated null allele, including Fibrillin1 (FBN1), which is responsible for development of the haploinsufficient Marfan disease. In this study, we examined the relationship between gene expression and DNA methylation patterns of the FBN1 CpG island shore focusing on transcriptionally active hypomethylated alleles (Hypo-alleles). No difference in the DNA methylation level of FBN1 CpG island shore was observed in porcine fetal fibroblast (PFF) and the liver, whereas FBN1 expression was higher in PFF than in the liver. However, Hypo-allele ratio of the FBN1 CpG island shore in PFF was higher than that in the liver, indicating that Hypo-allele ratio of the FBN1 CpG island shore likely correlated with FBN1 expression level. In addition, oocyte-derived DNA hypermethylation in preimplantation embryos was erased until the blastocyst stage, and re-methylation of the FBN1 CpG island shore was observed with prolonged in vitro culture of blastocysts. These results suggest that the establishment of the DNA methylation pattern within the FBN1 CpG island shore occurs after the blastocyst stage, likely during organogenesis. In conclusion, Hypo-allele ratios of the FBN1 CpG island shore correlated with FBN1 expression levels in porcine tissues.

Temporal Changes in Cellular Repopulation and Collagen Fibril Remodeling and Regeneration After Allograft Anterior Cruciate Ligament Reconstruction: An Experimental Study Using Kusabira-Orange Transgenic Pigs

BACKGROUND

Distinguishing recipient cells from donor ligament cells is difficult in the early graft-healing phase after anterior cruciate ligament (ACL) reconstruction. The ability to track the distribution and differentiation of recipient cells using genetically engineered transgenic (Tg) animals would have significant clinical and research effects on graft healing after ACL reconstruction.

HYPOTHESIS

Kusabira-Orange Tg pigs may allow the tracking of recipient cells infiltrating the graft after ACL reconstruction. The repopulation of recipient cells within the graft would be apparent even in the early graft-healing phase when necrotic donor cells are still present.

STUDY DESIGN

Descriptive laboratory study.

METHODS

In 17 genetically engineered Tg pigs, which carried the red fluorescent protein Kusabira-Orange, ACL reconstruction was performed on the right knee using a digital flexor tendon harvested from wild-type pigs. Tissue samples harvested at different time points were subjected to histological, immunohistochemical, and electron microscopic analyses.

RESULTS

At 3 weeks postoperatively, recipient cells expressing red fluorescence embraced the graft and were infiltrating the central part of the graft. These cells with oval nuclei gradually infiltrated the gap of collagen fibers, losing their regular orientation. At 6 weeks, cellularity within the graft had doubled to match that of the native ACL, while acellular necrotic regions still existed centrally. Ubiquitous cellular distributions resembling the native ACL were observed at 24 weeks. Electron microscopic analysis showed that the mean collagen fibril diameter and density gradually decreased over 24 weeks.

CONCLUSION

Genetically engineered pigs carrying the Kusabira-Orange gene were useful animal models for analyzing intrinsic and extrinsic cellular dynamics during the course of graft healing after ACL reconstruction. Cellular repopulation by recipient cells occurred in the very early stage, and the cellular distribution within the graft resembled that in the native ACL by 24 weeks, but the reconstructed graft had not restored the ultrastructure of the native ACL by that stage.

CLINICAL RELEVANCE

In allograft ACL reconstruction in a pig model, cellular repopulation was completed by 24 weeks after surgery, but the collagen matrix had not resumed the ultrastructure of the native ACL. Surgeons should be aware that risks may remain with returning to sports activities at 24 weeks after surgery.

A transgenic-cloned pig model expressing non-fluorescent modified Plum

Genetically modified pigs that express fluorescent proteins such as green and red fluorescent proteins have become indispensable biomedical research tools in recent years. Cell or tissue transplantation studies using fluorescent markers should be conducted, wherein the xeno-antigenicity of the fluorescent proteins does not affect engraftment or graft survival. Thus, we aimed to create a transgenic (Tg)-cloned pig that was immunologically tolerant to fluorescent protein antigens. In the present study, we generated a Tg-cloned pig harboring a derivative of Plum modified by a single amino acid substitution in the chromophore. The cells and tissues of this Tg-cloned pig expressing the modified Plum (mPlum) did not fluoresce. However, western blot and immunohistochemistry analyses clearly showed that the mPlum had the same antigenicity as Plum. Thus, we have obtained primary proof of principle for creating a cloned pig that is immunologically tolerant to fluorescent protein antigens.

Generation of heterozygous fibrillin-1 mutant cloned pigs from genome-edited foetal fibroblasts

Marfan syndrome (MFS) is an autosomal dominant genetic disease caused by abnormal formation of the extracellular matrix with an incidence of 1 in 3, 000 to 5, 000. Patients with Marfan syndrome experience poor quality of life caused by skeletal disorders such as scoliosis, and they are at high risk of sudden death from cardiovascular impairment. Suitable animal models of MFS are essential for conquering this intractable disease. In particular, studies employing pig models will likely provide valuable information that can be extrapolated to humans because of the physiological and anatomical similarities between the two species. Here we describe the generation of heterozygous fibrillin-1 (FBN1) mutant cloned pigs (+/Glu433AsnfsX98) using genome editing and somatic cell nuclear transfer technologies. The FBN1 mutant pigs exhibited phenotypes resembling those of humans with MFS, such as scoliosis, pectus excavatum, delayed mineralization of the epiphysis and disrupted structure of elastic fibres of the aortic medial tissue. These findings indicate the value of FBN1 mutant pigs as a model for understanding the pathogenesis of MFS and for developing treatments.

Urine excretion strategy for stem cell-generated embryonic kidneys

There have been several recent attempts to generate, de novo, a functional whole kidney from stem cells using the organogenic niche or blastocyst complementation methods. However, none of these attempts succeeded in constructing a urinary excretion pathway for the stem cell-generated embryonic kidney. First, we transplanted metanephroi from cloned pig fetuses into gilts; the metanephroi grew to about 3 cm and produced urine, although hydronephrosis eventually was observed because of the lack of an excretion pathway. Second, we demonstrated the construction of urine excretion pathways in rats. Rat metanephroi or metanephroi with bladders (developed from cloacas) were transplanted into host rats. Histopathologic analysis showed that tubular lumina dilation and interstitial fibrosis were reduced in kidneys developed from cloacal transplants compared with metanephroi transplantation. Then we connected the host animal's ureter to the cloacal-developed bladder, a technique we called the "stepwise peristaltic ureter" (SWPU) system. The application of the SWPU system avoided hydronephrosis and permitted the cloacas to differentiate well, with cloacal urine being excreted persistently through the recipient ureter. Finally, we demonstrated a viable preclinical application of the SWPU system in cloned pigs. The SWPU system also inhibited hydronephrosis in the pig study. To our knowledge, this is the first report showing that the SWPU system may resolve two important problems in the generation of kidneys from stem cells: construction of a urine excretion pathway and continued growth of the newly generated kidney.

Long time-course monitoring of ZFP809-mediated gene silencing in transgene expression driven by promoters containing MLV-derived PBS

Expression of Moloney murine leukemia virus (MoMLV)-typed retroviral vectors is strictly suppressed in immature cells such as embryonic stem cells. The phenomenon known as gene silencing is primed by the sequence-specific binding of the zinc finger protein 809 (ZFP809) to the primer-binding site of the vectors. However, it has yet to be determined whether the ZFP809-mediated gene silencing is maintained over a long period. In this study, we established an experimental system that can monitor gene silencing during a long-term cell culture using flow cytometry technology combined with fluorescent reporters for the expression of ZFP809 and the transgene expression driven by the promoters of interest. Time-course analysis using our system revealed that ZFP809 maintains gene silencing effect even at a longtime period. Furthermore, our system was useful for the monitoring of ZFP809-mediated gene silencing regardless of the types of vectors and cell lines.

PET Imaging of Serotonin Transporters With 4-[(18)F]-ADAM in a Parkinsonian Rat Model With Porcine Neural Xenografts

Parkinson's disease (PD) is a neurodegenerative disease characterized by a loss of dopaminergic neurons in the nigrostriatal pathway. Apart from effective strategies to halt the underlying neuronal degeneration, cell replacement now offers novel prospects for PD therapy. Porcine embryonic neural tissue has been considered an alternative source to human fetal grafts in neurodegenerative disorders because its use avoids major practical and ethical issues. This study was undertaken to evaluate the effects of embryonic day 27 (E27) porcine mesencephalic tissue transplantation in a PD rat model using animal positron emission tomography (PET) coupled with 4-[(18)F]-ADAM, a serotonin transporter (SERT) imaging agent. The parkinsonian rat was induced by injecting 6-hydroxydopamine into the medial forebrain bundle (MFB) of the right nigrostriatal pathway. The apomorphine-induced rotation behavioral test and 4-[(18)F]-ADAM/animal PET scanning were carried out following 6-OHDA lesioning. At the second week following 6-OHDA lesioning, the parkinsonian rat rotates substantially on apomorphine-induced contralateral turning. In addition, the mean striatal-specific uptake ratio (SUR) of 4-[(18)F]-ADAM decreased by 44%. After transplantation, the number of drug-induced rotations decreased markedly, and the mean SUR of 4-[(18)F]-ADAM and the level of SERT immunoreactivity (SERT-ir) in striatum were partially restored. The mean SUR level was restored to 71% compared to that for the contralateral intact side, which together with the abundant survival of tyrosine hydroxylase (TH) neurons accounted for functional recovery at the fourth week postgraft. In regard to the extent of donor-derived cells, we found the neurons of the xenografts from E27 transgenic pigs harboring red fluorescent protein (RFP) localized with TH-ir cells and SERT-ir in the grafted area. Thus, transplanted E27 porcine mesencephalic tissue may restore dopaminergic and serotonergic systems in the parkinsonian rat. The 4-[(18)F]-ADAM/animal PET can be used to detect serotonergic neuron loss in PD and monitor the efficacy of therapy.

Production of transgenic cloned pigs expressing the far-red fluorescent protein monomeric Plum

Monomeric Plum (Plum), a far-red fluorescent protein with photostability and photopermeability, is potentially suitable for in vivo imaging and detection of fluorescence in body tissues. The aim of this study was to generate transgenic cloned pigs exhibiting systemic expression of Plum using somatic cell nuclear transfer (SCNT) technology. Nuclear donor cells for SCNT were obtained by introducing a Plum-expression vector driven by a combination of the cytomegalovirus early enhancer and chicken beta-actin promoter into porcine fetal fibroblasts (PFFs). The cleavage and blastocyst formation rates of reconstructed SCNT embryos were 81.0% (34/42) and 78.6% (33/42), respectively. At 36-37 days of gestation, three fetuses systemically expressing Plum were obtained from one recipient to which 103 SCNT embryos were transferred (3/103, 2.9%). For generation of offspring expressing Plum, rejuvenated PFFs were established from one cloned fetus and used as nuclear donor cells. Four cloned offspring and one stillborn cloned offspring were produced from one recipient to which 117 SCNT embryos were transferred (5/117, 4.3%). All offspring exhibited high levels of Plum fluorescence in blood cells, such as lymphocytes, monocytes and granulocytes. In addition, the skin, heart, kidney, pancreas, liver and spleen also exhibited Plum expression. These observations demonstrated that transfer of the Plum gene did not interfere with the development of porcine SCNT embryos and resulted in the successful generation of transgenic cloned pigs that systemically expressed Plum. This is the first report of the generation and characterization of transgenic cloned pigs expressing the far-red fluorescent protein Plum.

The Use of a Green Fluorescent Protein Porcine Model to Evaluate Host Tissue Integration into Extracellular Matrix Derived Bionanocomposite Scaffolds

When using heterogeneous extracellular matrix (ECM) derived scaffolds for soft tissue repair, current methods of in vivo evaluation can fail to provide a clear distinction between host collagen and implanted scaffolds making it difficult to assess host tissue integration and remodeling. The purpose of this study is both to evaluate novel scaffolds conjugated with nanoparticles for host tissue integration and biocompatibility and to assess green fluorescent protein (GFP) expressing swine as a new animal model to evaluate soft tissue repair materials. Human-derived graft materials conjugated with nanoparticles were subcutaneously implanted into GFP expressing swine to be evaluated for biocompatibility and tissue integration through histological scoring and confocal imaging. Histological scoring indicates biocompatibility and remodeling of the scaffolds with and without nanoparticles at 1, 3, and 6 months. Confocal microscope images display host tissue integration into scaffolds although nonspecificity of GFP does not allow for quantification of integration. However, the confocal images do allow for spatial observation of host tissue migration into the scaffolds at different depths of penetration. The study concludes that the nanoparticle scaffolds are biocompatible and promote integration and that the use of GFP expressing swine can aid in visualizing the scaffold/host interface and host cell/tissue migration.

Generation and characterization of a transgenic pig carrying a DsRed-monomer reporter gene

BACKGROUND

Pigs are an optimal animal for conducting biomedical research because of their anatomical and physiological resemblance to humans. In contrast to the abundant resources available in the study of mice, few fluorescent protein-harboring porcine models are available for preclinical studies. In this paper, we report the successful generation and characterization of a transgenic DsRed-Monomer porcine model.

METHODS

The transgene comprised a CMV enhancer/chicken-beta actin promoter and DsRed monomeric cDNA. Transgenic pigs were produced by using pronuclear microinjection. PCR and Southern blot analyses were applied for identification of the transgene. Histology, blood examinations and computed tomography were performed to study the health conditions. The pig amniotic fluid progenitor/stem cells were also isolated to examine the existence of red fluorescence and differentiation ability.

RESULTS

Transgenic pigs were successfully generated and transmitted to offspring at a germ-line transmission rate of 43.59% (17/39). Ubiquitous expression of red fluorescence was detected in the brain, eye, tongue, heart, lung, liver, pancreas, spleen, stomach, small intestine, large intestine, kidney, testis, and muscle; this was confirmed by histology and western blot analyses. In addition, we confirmed the differentiation potential of amniotic fluid progenitor stem cells isolated from the transgenic pig.

CONCLUSIONS

This red fluorescent pig can serve as a host for other fluorescent-labeled cells in order to study cell-microenvironment interactions, and can provide optimal red-fluorescent-labeled cells and tissues for research in developmental biology, regenerative medicine, and xenotransplantation.

In vitro development of porcine transgenic nuclear-transferred embryos derived from newborn Guangxi Bama mini-pig kidney fibroblasts

Porcine transgenic cloning has potential applications for improving production traits and for biomedical research purposes. To produce a transgenic clone, kidney fibroblasts from a newborn Guangxi Bama mini-pig were isolated, cultured, and then transfected with red and green fluorescent protein genes using lipofectamine for nuclear transfer. The results of the present study show that the kidney fibroblasts exhibited excellent proliferative capacity and clone-like morphology, and were adequate for generation of somatic cell nuclear transfer (SCNT)-derived embryos, which was confirmed by their cleavage activity and blastocyst formation rate of 70.3% and 7.9%, respectively. Cells transfected with red fluorescent protein genes could be passed more than 35 times. Transgenic embryos cloned with fluorescent or blind enucleation methods were not significantly different with respect to cleavage rates (92.5% vs. 86.8%, p > 0.05) and blastocyst-morula rates (26.9% vs. 34.0%, p > 0.05), but were significantly different with respect to blastocyst rates (3.0% vs. 13.2%, p < 0.05). Cleavage (75.3%, 78.5% vs. 78.0%, p > 0.05), blastocyst (14.1%, 16.1% vs. 23.1%, p > 0.05) and morula/blastocyst rates (43.5%, 47.0% vs. 57.6%, p > 0.05) were not significantly different between the groups of transgenic cloned embryos, cloned embryos, and parthenogenetic embryos. This indicates that long-time screening by G418 caused no significant damage to kidney fibroblasts. Thus, kidney fibroblasts represent a promising new source for transgenic SCNT, and this work lays the foundation for the production of genetically transformed cloned Guangxi Bama mini-pigs.

Transgenic pigs with pancreas-specific expression of green fluorescent protein

The development and regeneration of the pancreas is of considerable interest because of the role of these processes in pancreatic diseases, such as diabetes. Here, we sought to develop a large animal model in which the pancreatic cell lineage could be tracked. The pancreatic and duodenal homeobox-1 (Pdx1) gene promoter was conjugated to Venus, a green fluorescent protein, and introduced into 370 in vitro-matured porcine oocytes by intracytoplasmic sperm injection-mediated gene transfer. These oocytes were transferred into four recipient gilts, all of which became pregnant. Three gilts were sacrificed at 47-65 days of gestation, and the fourth was allowed to farrow. Seven of 16 fetuses obtained were transgenic (Tg) and exhibited pancreas-specific green fluorescence. The fourth recipient gilt produced a litter of six piglets, two of which were Tg. The founder Tg offspring matured normally and produced healthy first-generation (G1) progeny. A postweaning autopsy of four 27-day-old G1 Tg piglets confirmed the pancreas-specific Venus expression. Immunostaining of the pancreatic tissue indicated the transgene was expressed in β-cells. Pancreatic islets from Tg pigs were transplanted under the renal capsules of NOD/SCID mice and expressed fluorescence up to one month after transplantation. Tg G1 pigs developed normally and had blood glucose levels within the normal range. Insulin levels before and after sexual maturity were within normal ranges, as were other blood biochemistry parameters, indicating that pancreatic function was normal. We conclude that Pdx1-Venus Tg pigs represent a large animal model suitable for research on pancreatic development/regeneration and diabetes.

Generation of interleukin-2 receptor gamma gene knockout pigs from somatic cells genetically modified by zinc finger nuclease-encoding mRNA

Zinc finger nuclease (ZFN) is a powerful tool for genome editing. ZFN-encoding plasmid DNA expression systems have been recently employed for the generation of gene knockout (KO) pigs, although one major limitation of this technology is the use of potentially harmful genome-integrating plasmid DNAs. Here we describe a simple, non-integrating strategy for generating KO pigs using ZFN-encoding mRNA. The interleukin-2 receptor gamma (IL2RG) gene was knocked out in porcine fetal fibroblasts using ZFN-encoding mRNAs, and IL2RG KO pigs were subsequently generated using these KO cells through somatic cell nuclear transfer (SCNT). The resulting IL2RG KO pigs completely lacked a thymus and were deficient in T and NK cells, similar to human X-linked SCID patients. Our findings demonstrate that the combination of ZFN-encoding mRNAs and SCNT provides a simple robust method for producing KO pigs without genomic integration.

The effect of cilostamide on gap junction communication dynamics, chromatin remodeling, and competence acquisition in pig oocytes following parthenogenetic activation and nuclear transfer

In the pig, the efficiency of in vitro embryo production and somatic cell nuclear transfer (SCNT) procedures remains limited. It has been suggested that prematuration treatments (pre-IVM) based on the prolongation of a patent, bidirectional crosstalk between the oocyte and the cumulus cells through gap junction mediate communication (GJC), with the maintenance of a proper level of cAMP, could improve the developmental capability of oocytes. The aim of this study was to assess: 1) dose-dependent effects of cilostamide on nuclear maturation kinetics, 2) the relationship between treatments on GJC functionality and large-scale chromatin configuration changes, and 3) the impact of treatments on developmental competence acquisition after parthenogenetic activation (PA) and SCNT. Accordingly, cumulus-oocyte complexes were collected from 3- to 6-mm antral follicles and cultured for 24 h in defined culture medium with or without 1 μM cilostamide. GJC functionality was assessed by Lucifer yellow microinjection, while chromatin configuration was evaluated by fluorescence microscopy after nuclear staining. Cilostamide administration sustained functional coupling for up to 24 h of culture and delayed meiotic resumption, as only 25.6% of cilostamide-treated oocytes reached the pro-metaphase I stage compared to the control (69.7%; P < 0.05). Moreover, progressive chromatin condensation was delayed before meiotic resumption based upon G2/M biomarker phosphoprotein epitope acquisition using immunolocalization. Importantly, cilostamide treatment under these conditions improved oocyte developmental competence, as reflected in higher blastocyst quality after both parthenogenetic activation and SCNT.

DNA methylation profiles provide a viable index for porcine pluripotent stem cells

Porcine induced pluripotent stem cells (iPSCs) provide useful information for translational research. The quality of iPSCs can be assessed by their ability to differentiate into various cell types after chimera formation. However, analysis of chimera formation in pigs is a labor-intensive and costly process, necessitating a simple evaluation method for porcine iPSCs. Our previous study identified mouse embryonic stem cell (ESC)-specific hypomethylated loci (EShypo-T-DMRs), and, in this study, 36 genes selected from these were used to evaluate porcine iPSC lines. Based on the methylation profiles of the 36 genes, the iPSC line, Porco Rosso-4, was found closest to mouse pluripotent stem cells among 5 porcine iPSCs. Moreover, Porco Rosso-4 more efficiently contributed to the inner cell mass (ICM) of blastocysts than the iPSC line showing the lowest reprogramming of the 36 genes (Porco Rosso-622-14), indicating that the DNA methylation profile correlates with efficiency of ICM contribution. Furthermore, factors known to enhance iPSC quality (serum-free medium with PD0325901 and CHIR99021) improved the methylation status at the 36 genes. Thus, the DNA methylation profile of these 36 genes is a viable index for evaluation of porcine iPSCs. genesis 51:763–776. © 2013 Wiley Periodicals, Inc.

Production of diabetic offspring using cryopreserved epididymal sperm by in vitro fertilization and intrafallopian insemination techniques in transgenic pigs

Somatic cell nuclear transfer (SCNT) is a useful technique for creating pig strains that model human diseases. However, production of numerous cloned disease model pigs by SCNT for large-scale experiments is impractical due to its complexity and inefficiency. In the present study, we aimed to establish an efficient procedure for proliferating the diabetes model pig carrying the mutant human hepatocyte nuclear factor-1α gene. A founder diabetes transgenic cloned pig was generated by SCNT and treated with insulin to allow for normal growth to maturity, at which point epididymal sperm could be collected for cryopreservation. In vitro fertilization and intrafallopian insemination using the cryopreserved epididymal sperm resulted in diabetes model transgenic offspring. These results suggest that artificial reproductive technology using cryopreserved epididymal sperm could be a practical option for proliferation of genetically modified disease model pigs.

Generation of transgenic Wuzhishan miniature pigs expressing monomeric red fluorescent protein by somatic cell nuclear transfer

Red fluorescent protein and its variants enable researchers to study gene expression, localization, and protein-protein interactions in vitro in real-time. Fluorophores with higher wavelengths are usually preferred since they efficiently penetrate tissues and produce less toxic emissions. A recently developed fluorescent protein marker, monomeric red fluorescent protein (mRFP1), is particularly useful because of its rapid maturation and minimal interference with green fluorescent protein (GFP) and GFP-derived markers. We generated a pCX-mRFP1-pgk-neoR construct and evaluated the ability of mRFP1 to function as a fluorescent marker in transgenic Wuzhishan miniature pigs. Transgenic embryos were generated by somatic cell nuclear transfer (SCNT) of nuclei isolated from ear fibroblasts expressing mRFP1. Embryos generated by SCNT developed into blastocysts in vitro (11.65%; 31/266). Thereafter, a total of 685 transgenic embryos were transferred into the oviducts of three recipients, two of which became pregnant. Of these, one recipient had six aborted fetuses, whereas the other recipient gave birth to four offspring. All offspring expressed the pCX-mRFP1-pgk-neoR gene as shown by PCR and fluorescence in situ hybridization analysis. The transgenic pigs expressed mRFP1 in all organs and tissues at high levels. These results demonstrate that Wuzhishan miniature pigs can express mRFP1. To conclude, this transgenic animal represents an excellent model with widespread applications in medicine and agriculture.

Generation of transgenic mouse line expressing Kusabira Orange throughout body, including erythrocytes, by random segregation of provirus method

Fluorescent-protein transgenic mice are useful for obtaining marked somatic cells to study kinetics of development or differentiation. Fluorescence-marked hematopoietic stem cells in particular are commonly used for studying hematopoiesis. However, as far as we know, no transgenic mouse line is described in which a fluorescent protein is stably and constitutively expressed in all hematopoietic cells, including erythrocytes and platelets. Using the random segregation of provirus (RSP) method, we generated from retrovirally transduced mouse embryonic stem cells a transgenic mouse line expressing a red/orange fluorescent protein, Kusabira Orange (KuO). KuO transgenic mouse line cells carry only one proviral integration site and stably express KuO in all hematopoietic-lineage elements, including erythrocytes and platelets. Moreover, bone-marrow transplantation in KuO transgenic mice demonstrated normal hematopoieisis. KuO transgenic mice likely will prove useful for study of hematopoiesis that includes erythropoiesis and megakaryopoiesis.

Transgenic pig expressing the red fluorescent protein kusabira-orange as a novel tool for preclinical studies on hepatocyte transplantation

INTRODUCTION

Research on hepatocyte transplantation as an alternative or supplementary treatment for liver transplantation is progressing. However, to advance to clinical trials, confidence in the technique must be established and its safety must be validated by conducting experiments using animals of comparable sizes to humans, such as pigs. We used transgenic pigs expressing red fluorescence protein for investigating the distribution and survival of transplanted cells.

MATERIALS AND METHODS

Donor hepatocytes were isolated from transgenic Kusabira-Orange (KO)-expressing pigs (age, 41 days; weight, 10 kg) created by in vitro fertilization using sperm from a transgenic-cloned KO pig by Matsunari et al. and ova from a domestic pig. The hepatocyte transplant recipients were the nontransgenic, KO-negative littermates. In these recipient pigs, double lumen cannulae were inserted into the supramesenteric veins to access the hepatic portal region. KO-positive donor hepatocytes from the transgenic male pig were isolated using collagenase perfusion. Hepatocytes (1 × 10(9) cells) were transplanted through the cannula. For estimating allogeneic immunogenicity, full-thickness skin (3 × 3 cm) from the same donor was grafted orthotopically on the neck region of the recipients. Immunosuppressive treatment was not implemented. The recipient pigs were humanely killed at 7 and 39 days after transplantation, and the organs were harvested, including the lungs, heart, liver, pancreas, and kidneys.

RESULTS

Strong red fluorescence was detected in both the parenchymal and nonparenchymal hepatocytes of the transgenic male donor pig by fluorescent microscopy. Transplanted cells were detected in the liver and lung of the recipient pigs at 7 days after perfusion. Hepatocytes remained in the liver and lung of recipients on day 39, with lower numbers than that on day 7.

CONCLUSION

Transgenic pigs expressing the fluorescent protein KO serve as a useful model of cell transplantation in preclinical studies.

Pluripotent cells in farm animals: state of the art and future perspectives

Pluripotent cells, such as embryonic stem (ES) cells, embryonic germ cells and embryonic carcinoma cells are a unique type of cell because they remain undifferentiated indefinitely in in vitro culture, show self-renewal and possess the ability to differentiate into derivatives of the three germ layers. These capabilities make them a unique in vitro model for studying development, differentiation and for targeted modification of the genome. True pluripotent ESCs have only been described in the laboratory mouse and rat. However, rodent physiology and anatomy differ substantially from that of humans, detracting from the value of the rodent model for studies of human diseases and the development of cellular therapies in regenerative medicine. Recently, progress in the isolation of pluripotent cells in farm animals has been made and new technologies for reprogramming of somatic cells into a pluripotent state have been developed. Prior to clinical application of therapeutic cells differentiated from pluripotent stem cells in human patients, their survival and the absence of tumourigenic potential must be assessed in suitable preclinical large animal models. The establishment of pluripotent cell lines in farm animals may provide new opportunities for the production of transgenic animals, would facilitate development and validation of large animal models for evaluating ESC-based therapies and would thus contribute to the improvement of human and animal health. This review summarises the recent progress in the derivation of pluripotent and reprogrammed cells from farm animals. We refer to our recent review on this area, to which this article is complementary.

Blastocyst complementation generates exogenic pancreas in vivo in apancreatic cloned pigs

In the field of regenerative medicine, one of the ultimate goals is to generate functioning organs from pluripotent cells, such as ES cells or induced pluripotent stem cells (PSCs). We have recently generated functional pancreas and kidney from PSCs in pancreatogenesis- or nephrogenesis-disabled mice, providing proof of principle for organogenesis from PSCs in an embryo unable to form a specific organ. Key when applying the principles of in vivo generation to human organs is compensation for an empty developmental niche in large nonrodent mammals. Here, we show that the blastocyst complementation system can be applied in the pig using somatic cell cloning technology. Transgenic approaches permitted generation of porcine somatic cell cloned embryos with an apancreatic phenotype. Complementation of these embryos with allogenic blastomeres then created functioning pancreata in the vacant niches. These results clearly indicate that a missing organ can be generated from exogenous cells when functionally normal pluripotent cells chimerize a cloned dysorganogenetic embryo. The feasibility of blastocyst complementation using cloned porcine embryos allows experimentation toward the in vivo generation of functional organs from xenogenic PSCs in large animals.

Advancing pig cloning technologies towards application in regenerative medicine

Regenerative medicine is expected to make a significant contribution by development of novel therapeutic treatments for intractable diseases and for improving the quality of life of patients. Many advances in regenerative medicine, including basic and translational research, have been developed and tested in experimental animals; pigs have played an important role in various aspects of this work. The value of pigs as a model species is being enhanced by the generation of specially designed animals through cloning and genetic modifications, enabling more sophisticated research to be performed and thus accelerating the clinical application of regenerative medicine. This article reviews the significant aspects of the creation and application of cloned and genetically modified pigs in regenerative medicine research and considers the possible future directions of the technology. We also discuss the importance of reproductive biology as an interface between basic science and clinical medicine.

Xenotransplanted embryonic kidney provides a niche for endogenous mesenchymal stem cell differentiation into erythropoietin-producing tissue

Recent findings have demonstrated that stem cells can differentiate into mature tissue when supplied with a niche containing factors identical to those in the normal developmental program. A niche for the development of an organ can be provided by xenotransplantation of a similar developing organ. However, this process has many technical, safety, and ethical concerns. Here, we established xenotransplantation models that control endogenous mesenchymal stem cell (MSC) differentiation into mature erythropoietin (EPO)-producing tissue in a niche provided by a developing xenometanephros. Transplantation of rat metanephroi into mouse omentum, and similarly pig metanephroi into cat omentum, led to the recruitment of host cells and EPO production. EPO-expressing cells were not differentiated from integrating vessels because they did not coexpress endothelial markers (Tie-2 and VE-cadherin). Instead, EPO-expressing cells were shown to be derived from circulating host cells, as shown by enhanced green fluorescent protein (EGFP) expression in the grown transplants of chimeric mice bearing bone marrow from a transgenic mouse expressing EGFP under the control of the EPO promoter. These results suggest that donor cell recruitment and differentiation in a xenotransplanted developing organ may be consistent between species. The cells responsible for EPO expression were identified as MSCs by injecting human bone marrow-derived MSCs and endothelial progenitor cells into NOD/SCID mice. Furthermore, using metanephroi from transgenic ER-E2F1 suicide-inducible mice, the xenotissue component could be eliminated, leaving autologous EPO-producing tissue. Our findings may alleviate adverse effects due to long-lasting immunosuppression and help mitigate ethical concerns.

Generation of naive-like porcine-induced pluripotent stem cells capable of contributing to embryonic and fetal development

In pluripotent stem cells (PSCs), there are 2 types: naive and primed. Only the naive type has the capacity for producing chimeric offspring. Mouse PSCs are naive, but human PSCs are in the primed state. Previously reported porcine PSCs appear in the primed state. In this study, putative naive porcine-induced pluripotent stem cells (iPSCs) were generated. Porcine embryonic fibroblasts were transduced with retroviral vectors expressing Yamanaka's 4 genes. Emergent colonies were propagated in the presence of porcine leukemia inhibitory factor (pLIF) and forskolin. The cells expressed pluripotency markers and formed embryoid bodies, which gave rise to cell types from all 3 embryonic germ layers. The naive state of the cells was demonstrated by pLIF dependency, 2 active X chromosomes (when female), absent MHC class I expression, and characteristic gene expression profiles. The porcine iPSCs contributed to the in vitro embryonic development (11/24, 45.8%) as assessed by fluorescent markers. They also contributed to the in utero fetal development (11/71, 15.5% at day 23; 1/13, 7.7% at day 65). This is the first demonstration of macroscopic fluorescent chimeras derived from naive-like porcine PSCs, although adult chimeras remain to be produced.

Hollow fiber vitrification provides a novel method for cryopreserving in vitro maturation/fertilization-derived porcine embryos

In vitro matured (IVM) oocytes have been used to create genetically modified pigs for various biomedical purposes. However, porcine embryos derived from IVM oocytes are very cryosensitive. Developing improved cryopreservation methods would facilitate the production of genetically modified pigs and also accelerate the conservation of genetic resources. We recently developed a novel hollow fiber vitrification (HFV) method; the present study was initiated to determine whether this new method permits the cryopreservation of IVM oocyte-derived porcine embryos. Embryos were created from the in vitro fertilization of IVM oocytes with frozen-thawed sperm derived from a transgenic pig carrying a humanized Kusabira-Orange (huKO) gene. Morula-stage embryos were assigned to vitrification and nonvitrification groups to compare their in vitro and in vivo developmental abilities. Vitrified morulae developed to the blastocyst stage at a rate similar to that of nonvitrified embryos (66/85, 77.6% vs. 67/84, 79.8%). Eighty-eight blastocysts that developed from vitrified morulae were transferred into the uteri of three recipient gilts. All three became pregnant and produced a total of 17 piglets (19.3%). This piglet production was slightly lower, albeit not significantly, than that of the nonvitrification group (27/88, 30.7%). Approximately half of the piglets in the vitrification (10/17, 58.8%) and nonvitrification (15/27, 55.6%) groups were transgenic. There was no significant difference in the growth rates among the piglets in the two groups. These results indicate that the HFV method is an extremely effective method for preserving cryosensitive embryos such as porcine in vitro maturation/fertilization-derived morulae.

Rapid non-invasive genotyping of reporter transgenic mammals

Here we describe a non-invasive method for rapid and highly reproducible genotyping of transgenic mammals with ubiquitous expression of fluorophore reporters. Hair samples from transgenic mice and pigs with systemic expression of the fluorophore reporter Venus were analyzed with a fluorescence microscope in few minutes. The hair samples can be preserved for long-term storage at ambient temperature conditions. This non-invasive method is useful for genotyping of transgenic large animals and contributes to animal welfare by reducing stress and discomfort of the animals during sample collection.

Precision editing of large animal genomes

Transgenic animals are an important source of protein and nutrition for most humans and will play key roles in satisfying the increasing demand for food in an ever-increasing world population. The past decade has experienced a revolution in the development of methods that permit the introduction of specific alterations to complex genomes. This precision will enhance genome-based improvement of farm animals for food production. Precision genetics also will enhance the development of therapeutic biomaterials and models of human disease as resources for the development of advanced patient therapies.

Genetic modifications of pigs for medicine and agriculture

Genetically modified swine hold great promise in the fields of agriculture and medicine. Currently, these swine are being used to optimize production of quality meat, to improve our understanding of the biology of disease resistance, and to reduced waste. In the field of biomedicine, swine are anatomically and physiologically analogous to humans. Alterations of key swine genes in disease pathways provide model animals to improve our understanding of the causes and potential treatments of many human genetic disorders. The completed sequencing of the swine genome will significantly enhance the specificity of genetic modifications, and allow for more accurate representations of human disease based on syntenic genes between the two species. Improvements in both methods of gene alteration and efficiency of model animal production are key to enabling routine use of these swine models in medicine and agriculture.

Pluripotent stem cells and reprogrammed cells in farm animals

Pluripotent cells are unique because of their ability to differentiate into the cell lineages forming the entire organism. True pluripotent stem cells with germ line contribution have been reported for mice and rats. Human pluripotent cells share numerous features of pluripotentiality, but confirmation of their in vivo capacity for germ line contribution is impossible due to ethical and legal restrictions. Progress toward derivation of embryonic stem cells from domestic species has been made, but the derived cells were not able to produce germ line chimeras and thus are termed embryonic stem-like cells. However, domestic animals, in particular the domestic pig (Sus scrofa), are excellent large animals models, in which the clinical potential of stem cell therapies can be studied. Reprogramming technologies for somatic cells, including somatic cell nuclear transfer, cell fusion, in vitro culture in the presence of cell extracts, in vitro conversion of adult unipotent spermatogonial stem cells into germ line derived pluripotent stem cells, and transduction with reprogramming factors have been developed with the goal of obtaining pluripotent, germ line competent stem cells from domestic animals. This review summarizes the present state of the art in the derivation and maintenance of pluripotent stem cells in domestic animals.

Perspectives on transgenic livestock in agriculture and biomedicine: an update

It has been 30 years since the first transgenic mouse was generated and 26 years since the first example of transferring the technology to livestock was published. While there was tremendous optimism in those initial years, with most convinced that genetically modified animals would play a significant role in agricultural production, that has not come to be. So at first sight one could conclude that this technology has, to a large extent, failed. On the contrary, it is believed that it has succeeded beyond our original expectations, and we are now at what is perhaps the most exciting time in the development and implementation of these technologies. The original goals, however, have drastically changed and it is now biomedical applications that are playing a central role in pushing both technical and scientific developments. The combination of advances in somatic cell nuclear transfer, the development of induced pluripotent stem cells and the completion of the sequencing of most livestock genomes ensures a bright and exciting future for this field, not only in livestock but also in companion animal species.

Production of genetically modified porcine blastocysts by somatic cell nuclear transfer: preliminary results toward production of xenograft-competent miniature pigs

Galα1-3Gal (α-Gal epitope) is the major xenoantigenic epitope responsible for hyperacute rejection upon pig-to-human xenotransplantation. Endo-β-galactosidase C (EndoGalC) from Clostridium perfringens can digest the α-Gal epitope. In this study, gene-engineered primary cultured porcine embryonic fibroblasts (PEF) expressing EndoGalC were obtained and subjected to somatic cell nuclear transfer (SCNT) to test whether xenograft-competent pigs can be created. The EndoGalC-expressing PEF clones exhibited highly reduced expression of α-Gal epitope, as revealed by cytochemical staining with BS-I-B(4) isolectin, a lectin that specifically binds to α-Gal epitope, and FACS analysis. The pattern of low level of α-Gal epitope expression continued for at least 6 months (more than 10 generations) after isolation. SCNT of nuclei from these cells resulted in the generation of blastocysts that displayed nearly complete loss of α-Gal epitope from their cell surface. This is the first study to demonstrate that SCNT using EndoGalC-expressing PEFs as donors would be useful for production of genetically modified cloned pigs suitable for xenotransplantation.

Pregnancies and piglets from large white sow recipients after two transfer methods of cloned and transgenic embryos of different pig breeds

The aim of this study was to report from a larger study with pregnancy and delivery results after transfer of cloned transgenic/non-transgenic Large White or minipig embryos to Large White sow recipients. The effect of both total numbers of transferred embryos as well as site of their deposition (uni- vs. bi-lateral) was studied. Four to five days after natural heat, 85 Large White (LW) sows received Day 5 or 6 handmade cloned embryos. Large White embryos were non-transgenic and were transferred to 36 recipients, while 49 recipients each received Minipig embryos, either non-transgenic or with 1 of 4 types of transgenes. Furthermore, the number of embryos transferred was in two categories, as 46 recipients received 40-60 embryos while 39 received 60-120 embryos. Finally, in 59 of the recipients embryos were transferred to one of the uterine horns (unicornual) while 26 other recipients had embryos transferred to both uterine horns (bicornual). The overall pregnancy rate was 55% with an abortion rate of 26% resulting in 41% deliveries with no difference between LW and Minipig embryos and no difference between transgenic and non-transgenic Minipig embryos. Transfer of 60-120 embryos resulted in more pregnancies and deliveries (62%) than <60 embryos (24%). The mean litter size was 5.1 ± 0.5 and after transfer of 60-120 embryos significantly higher (6.0 ± 0.5) than after transfer of <60 embryos (3.5 ± 0.8). Also, the bicornual transfer resulted in significantly higher delivery rate (74% vs. 44%) and mean litter size (6.1 ± 0.7 vs. 4.2 ± 0.6) than the unicornual. The mean rate of piglets/transferred embryos was 7.3 ± 0.6% while the mean rate of piglets/reconstructed embryos was 179/18,000 = 1% with no difference between breeds or number of embryos transferred. The overall perinatal mortality rate was 49%, and it was significantly lower in LW piglets (20/59 = 34%) than in Minipiglets (67/120 = 56%) (vs. 10-15% in normal piglets at the farm) and the total rate of piglets with one or more malformation was 22%, and lower in LW (12%) than in Minipiglets (28%). This study demonstrate that although the perinatal mortality was rather high, an acceptable birth rate can be achieved after transfer to LW recipients of cloned LW embryos as well as cloned, transgenic/non-transgenic Minipig embryos. Furthermore, the pregnancy rate and litter size were correlated to the number of embryos transferred and to bicornual transfer.

Application of genetically modified and cloned pigs in translational research

Pigs are increasingly being recognized as good large-animal models for translational research, linking basic science to clinical applications in order to establish novel therapeutics. This article reviews the current status and future prospects of genetically modified and cloned pigs in translational studies. It also highlights pigs specially designed as disease models, for xenotransplantation or to carry cell marker genes. Finally, use of porcine somatic stem and progenitor cells in preclinical studies of cell transplantation therapy is also discussed.

Noncytotoxic orange and red/green derivatives of DsRed-Express2 for whole-cell labeling

BACKGROUND

Whole-cell labeling is a common application of fluorescent proteins (FPs), but many red and orange FPs exhibit cytotoxicity that limits their use as whole-cell labels. Recently, a tetrameric red FP called DsRed-Express2 was engineered for enhanced solubility and was shown to be noncytotoxic in bacterial and mammalian cells. Our goal was to create derivatives of this protein with different spectral properties.

RESULTS

Building on previous studies of DsRed mutants, we created two DsRed-Express2 derivatives: E2-Orange, an orange FP, and E2-Red/Green, a dual-color FP with both red and green emission. We show that these new FPs retain the low cytotoxicity of DsRed-Express2. In addition, we show that these new FPs are useful as second or third colors for flow cytometry and fluorescence microscopy.

CONCLUSION

E2-Orange and E2-Red/Green will facilitate the production of healthy, stably fluorescent cell lines and transgenic organisms for multi-color labeling studies.