An optimized culture system for efficient derivation of porcine expanded potential stem cells from preimplantation embryos and by reprogramming somatic cells

Pigs share anatomical and physiological traits with humans and can serve as a large-animal model for translational medicine. Bona fide porcine pluripotent stem cells (PSCs) could facilitate testing cell and drug therapies. Agriculture and biotechnology may benefit from the ability to produce immune cells for studying animal infectious diseases and to readily edit the porcine genome in stem cells. Isolating porcine PSCs from preimplantation embryos has been intensively attempted over the past decades. We previously reported the derivation of expanded potential stem cells (EPSCs) from preimplantation embryos and by reprogramming somatic cells of multiple mammalian species, including pigs. Porcine EPSCs (pEPSCs) self-renew indefinitely, differentiate into embryonic and extra-embryonic lineages, and permit precision genome editing. Here we present a highly reproducible experimental procedure and data of an optimized and robust porcine EPSC culture system and its use in deriving new pEPSC lines from preimplantation embryos and reprogrammed somatic cells. No particular expertise is required for the protocols, which take ~4-6 weeks to complete. Importantly, we successfully established pEPSC lines from both in vitro fertilized and somatic cell nuclear transfer-derived embryos. These new pEPSC lines proliferated robustly over long-term passaging and were amenable to both simple indels and precision genome editing, with up to 100% targeting efficiency. The pEPSCs differentiated into embryonic cell lineages in vitro and teratomas in vivo, and into porcine trophoblast stem cells in human trophoblast stem cell medium. We show here that pEPSCs have unique epigenetic features, particularly H3K27me3 levels substantially lower than fibroblasts.

Genetic knockout of porcine GGTA1 or CMAH/GGTA1 is associated with the emergence of neo-glycans

BACKGROUND

Pig-derived tissues could overcome the shortage of human donor organs in transplantation. However, the glycans with terminal α-Gal and Neu5Gc, which are synthesized by enzymes, encoded by the genes GGTA1 and CMAH, are known to play a major role in immunogenicity of porcine tissue, ultimately leading to xenograft rejection.

METHODS

The N-glycome and glycosphingolipidome of native and decellularized porcine pericardia from wildtype (WT), GGTA1-KO and GGTA1/CMAH-KO pigs were analyzed by multiplexed capillary gel electrophoresis coupled to laser-induced fluorescence detection.

RESULTS

We identified biantennary and core-fucosylated N-glycans terminating with immunogenic α-Gal- and α-Gal-/Neu5Gc-epitopes on pericardium of WT pigs that were absent in GGTA1 and GGTA1/CMAH-KO pigs, respectively. Levels of N-glycans terminating with galactose bound in β(1-4)-linkage to N-acetylglucosamine and their derivatives elongated by Neu5Ac were increased in both KO groups. N-glycans capped with Neu5Gc were increased in GGTA1-KO pigs compared to WT, but were not detected in GGTA1/CMAH-KO pigs. Similarly, the ganglioside Neu5Gc-GM3 was found in WT and GGTA1-KO but not in GGTA1/CMAH-KO pigs. The applied detergent based decellularization efficiently removed GSL glycans.

CONCLUSION

Genetic deletion of GGTA1 or GGTA1/CMAH removes specific epitopes providing a more human-like glycosylation pattern, but at the same time changes distribution and levels of other porcine glycans that are potentially immunogenic.

Xenotransplantate vom Schwein – ist das Ende des Organmangels in Sicht?

Unter „Xenotransplantation“ wird die Übertragung von funktionsfähigen Zellen, Geweben oder Organen zwischen verschiedenen Spezies verstanden, insbesondere von Schweinen auf den Menschen. In den meisten Industrieländern klafft eine große Lücke zwischen der Anzahl geeigneter Spenderorgane und der Anzahl benötigter Transplantate. Weltweit können nur etwa 10% des Organbedarfs durch Spenden gedeckt werden. Eine erfolgreiche Xenotransplantation könnte diesen Mangel mildern oder sogar weitgehend vermeiden. Das Schwein wird aus verschiedenen Erwägungen heraus als am besten geeignete Spenderspezies angesehen. Bei einer Übertragung porziner Organe auf Primaten treten verschiedene immunologisch bedingte Abstoßungsreaktionen auf, die das übertragene Organ innerhalb kurzer Zeit zerstören können, wie die HAR (hyperakute Abstoßung), die AVR (akute vaskuläre Abstoßung) und die spätere zelluläre Abstoßung. Diese Abstoßungsreaktionen müssen durch genetische Modifikationen im Schwein und eine geeignete immunsuppressive Behandlung des Empfängers kontrolliert werden. Dazu müssen Tiere mit mehrfachen genetischen Veränderungen produziert und im Hinblick auf ihre Eignung für eine erfolgreiche Xenotransplantation geprüft werden. Inzwischen können die HAR und auch die AVR durch Knockouts von antigenen Oberflächenepitopen (z. B. αGal [Galaktose-α1,3-Galaktose]) und transgene Expression humaner Gene mit antiinflammatorischer, antiapoptotischer oder antikoagulativer Wirkung zuverlässig kontrolliert werden. Nach orthotopen Transplantationen in nicht humane Primaten konnten inzwischen mit Schweineherzen Überlebensraten von bis zu 264 Tagen und mit porzinen Nieren von 435 Tagen erzielt werden. Eine Übertragung pathogener Erreger auf den Empfänger kann bei Einhaltung einschlägiger Hygienemaßnahmen ausgeschlossen werden. PERV (porzine endogene Retroviren) können durch RNA-(Ribonukleinsäure-)Interferenz oder Gen-Knockout ausgeschaltet werden. Sie stellen damit kein Übertragungsrisiko für den Empfänger mehr dar. Anfang 2022 wurde in Baltimore (USA) ein Schweineherz mit 10 genetischen Modifikationen auf einen Patienten mit schwerem Herzleiden übertragen, mit dem der Empfänger 2 Monate offenbar ohne größere Probleme lebte. Es wird erwartet, dass Xenotransplantate vom Schwein in absehbarer Zeit zur klinischen Anwendungsreife kommen werden. Dazu werden klinische Versuche zur systematischen Erfassung aller Auswirkungen solcher Transplantate auf den Patienten sowie geeignete rechtliche und finanzielle Rahmenbedingungen benötigt.

Species-Specific Paternal Age Effects and Sperm Methylation Levels of Developmentally Important Genes

A growing number of sperm methylome analyses have identified genomic loci that are susceptible to paternal age effects in a variety of mammalian species, including human, bovine, and mouse. However, there is little overlap between different data sets. Here, we studied whether or not paternal age effects on the sperm epigenome have been conserved in mammalian evolution and compared methylation patterns of orthologous regulatory regions (mainly gene promoters) containing both conserved and non-conserved CpG sites in 94 human, 36 bovine, and 94 mouse sperm samples, using bisulfite pyrosequencing. We discovered three (NFKB2, RASGEF1C, and RPL6) age-related differentially methylated regions (ageDMRs) in humans, four (CHD7, HDAC11, PAK1, and PTK2B) in bovines, and three (Def6, Nrxn2, and Tbx19) in mice. Remarkably, the identified sperm ageDMRs were all species-specific. Most ageDMRs were in genomic regions with medium methylation levels and large methylation variation. Orthologous regions in species not showing this age effect were either hypermethylated (>80%) or hypomethylated (<20%). In humans and mice, ageDMRs lost methylation, whereas bovine ageDMRs gained methylation with age. Our results are in line with the hypothesis that sperm ageDMRs are in regions under epigenomic evolution and may be part of an epigenetic mechanism(s) for lineage-specific environmental adaptations and provide a solid basis for studies on downstream effects in the genes analyzed here.

Stem cell-derived porcine macrophages as a new platform for studying host-pathogen interactions

BACKGROUND

Infectious diseases of farmed and wild animals pose a recurrent threat to food security and human health. The macrophage, a key component of the innate immune system, is the first line of defence against many infectious agents and plays a major role in shaping the adaptive immune response. However, this phagocyte is a target and host for many pathogens. Understanding the molecular basis of interactions between macrophages and pathogens is therefore crucial for the development of effective strategies to combat important infectious diseases.

RESULTS

We explored how porcine pluripotent stem cells (PSCs) can provide a limitless in vitro supply of genetically and experimentally tractable macrophages. Porcine PSC-derived macrophages (PSCdMs) exhibited molecular and functional characteristics of ex vivo primary macrophages and were productively infected by pig pathogens, including porcine reproductive and respiratory syndrome virus (PRRSV) and African swine fever virus (ASFV), two of the most economically important and devastating viruses in pig farming. Moreover, porcine PSCdMs were readily amenable to genetic modification by CRISPR/Cas9 gene editing applied either in parental stem cells or directly in the macrophages by lentiviral vector transduction.

CONCLUSIONS

We show that porcine PSCdMs exhibit key macrophage characteristics, including infection by a range of commercially relevant pig pathogens. In addition, genetic engineering of PSCs and PSCdMs affords new opportunities for functional analysis of macrophage biology in an important livestock species. PSCs and differentiated derivatives should therefore represent a useful and ethical experimental platform to investigate the genetic and molecular basis of host-pathogen interactions in pigs, and also have wider applications in livestock.

Immunological and functional features of decellularized xenogeneic heart valves after transplantation into GGTA1-KO pigs

Decellularization of xenogeneic heart valves might lead to excellent regenerative implants, from which many patients could benefit. However, this material carries various xenogeneic epitopes and thus bears a considerable inherent immunological risk. Here, we investigated the regenerative and immunogenic potential of xenogeneic decellularized heart valve implants using pigs deficient for the galactosyltransferase gene (GGTA1-KO) as novel large animal model. Decellularized aortic and pulmonary heart valves obtained from sheep, wild-type pigs or GGTA1-KO pigs were implanted into GGTA1-KO pigs for 3, or 6 months, respectively. Explants were analyzed histologically, immunhistologically (CD3, CD21 and CD172a) and anti-αGal antibody serum titers were determined by ELISA. Xenogeneic sheep derived implants exhibited a strong immune reaction upon implantation into GGTA1-KO pigs, characterized by massive inflammatory cells infiltrates, presence of foreign body giant cells, a dramatic increase of anti-αGal antibody titers and ultimately destruction of the graft, whereas wild-type porcine grafts induced only a mild reaction in GGTA1-KO pigs. Allogeneic implants, wild-type/wild-type and GGTA1-KO/GGTA1-KO valves did not induce a measurable immune reaction. Thus, GGTA1-KO pigs developed a 'human-like' immune response toward decellularized xenogeneic implants showing that immunogenicity of xenogeneic implants is not sufficiently reduced by decellularization, which detracts from their regenerative potential.

Melatonin improves rate of monospermic fertilization and early embryo development in a bovine IVF system

The developmental competence of male and female gametes is frequently reduced under in vitro conditions, mainly due to oxidative stress during handling. The amino-acid derived hormone melatonin has emerged as a potent non-enzymatic antioxidant in many biological systems. The goal of the present study was to evaluate the effects of melatonin on post-thaw sperm quality, fertilizing ability, and embryo development and competence in vitro after in vitro fertilization. Frozen-thawed bovine spermatozoa were incubated either in the presence of 10⁻¹¹ M melatonin (MT), or its solvent (ethanol; Sham-Control), or plain Tyrode’s Albumin Lactate Pyruvate medium (TALP, Control). Computer-Assisted Sperm Analysis (CASA) and flow cytometry data after 30 min, 120 min, and 180 min incubation did not reveal any significant effects of melatonin on average motility parameters, sperm subpopulation structure as determined by hierarchical cluster, or on the percentage of viable, acrosome intact sperm, or viable sperm with active mitochondria. Nevertheless, in vitro matured cumulus-oocyte-complexes fertilized with spermatozoa which had been preincubated with 10⁻¹¹ M melatonin (MT-Sperm) showed higher (P < 0.01) rates of monospermic fertilization, reduced (P < 0.05) polyspermy and enhanced (P < 0.05) embryo development compared to the Control group. Moreover, the relative abundance of MAPK13 in the in vitro-derived blastocysts was greater (P < 0.05) than observed in the Control group. In conclusion, adding melatonin to the sperm-preparation protocol for bovine IVF improved proper fertilization and enhanced embryonic development and competence in vitro.

Parental genome unification is highly error-prone in mammalian embryos

Most human embryos are aneuploid. Aneuploidy frequently arises during the early mitotic divisions of the embryo, but its origin remains elusive. Human zygotes that cluster their nucleoli at the pronuclear interface are thought to be more likely to develop into healthy euploid embryos. Here, we show that the parental genomes cluster with nucleoli in each pronucleus within human and bovine zygotes, and clustering is required for the reliable unification of the parental genomes after fertilization. During migration of intact pronuclei, the parental genomes polarize toward each other in a process driven by centrosomes, dynein, microtubules, and nuclear pore complexes. The maternal and paternal chromosomes eventually cluster at the pronuclear interface, in direct proximity to each other, yet separated. Parental genome clustering ensures the rapid unification of the parental genomes on nuclear envelope breakdown. However, clustering often fails, leading to chromosome segregation errors and micronuclei, incompatible with healthy embryo development.

Direct conversion of porcine primary fibroblasts into hepatocyte-like cells

The pig is an important model organism for biomedical research, mainly due to its extensive genetic, physiological and anatomical similarities with humans. Until date, direct conversion of somatic cells into hepatocyte-like cells (iHeps) has only been achieved in rodents and human cells. Here, we employed lentiviral vectors to screen a panel of 12 hepatic transcription factors (TF) for their potential to convert porcine fibroblasts into hepatocyte-like cells. We demonstrate for the first time, hepatic conversion of porcine somatic cells by over-expression of CEBPα, FOXA1 and HNF4α2 (3TF-piHeps). Reprogrammed 3TF-piHeps display a hepatocyte-like morphology and show functional characteristics of hepatic cells, including albumin secretion, Dil-AcLDL uptake, storage of lipids and glycogen and activity of cytochrome P450 enzymes CYP1A2 and CYP2C33 (CYP2C9 in humans). Moreover, we show that markers of mature hepatocytes are highly expressed in 3TF-piHeps, while fibroblastic markers are reduced. We envision piHeps as useful cell sources for future studies on drug metabolism and toxicity as well as in vitro models for investigation of pig-to-human infectious diseases.

Melatonin enhances in vitro developmental competence of cumulus-oocyte complexes collected by ovum pick-up in prepubertal and adult dairy cattle

Bovine oocytes from prepubertal donors have been used for in vitro embryo production to decrease the generation interval. However, reduced cumulus-oocyte competence, mainly attributed to increased apoptosis, has been observed in oocytes/embryos collected from prepubertal donors. Here, we investigated the effects of the potent antioxidative molecule melatonin on cumulus-oocyte competence and embryo development in prepubertal and adult dairy cattle in vitro. A total of fifteen Holstein Friesian calves, six to ten months old (7.6 ± 1.34 months of age). And fifteen adult cows with one to four calvings (2.3 ± 0.96 calvings) were enrolled as ovum pick up (OPU) donors in this study. Cumulus-oocyte complexes (COCs) were cultured either in the presence or absence of melatonin (0.01 nM). The proportion of cleavage stages, blastocysts, and advanced blastocysts was determined. Embryo quality was assessed via differential staining to determine the total embryonic cells and allocation to the inner cell mass (ICM) and trophectoderm (TE) cells. Melatonin treatment yielded a greater percentage of blastocysts compared to the control group, i.e. oocytes from both adult cows (P = 0.0485; 24.8 ± 3.5% vs. 16.0 ± 3.4%, respectively), and from prepubertal donors (P = 0.0007; Melatonin 23.1 ± 5.1% vs. Control: 11.1 ± 3.5%). Adult cows had significantly (P = 0.0370) greater advanced blastocyst rates than those found in the prepubertal group (13.9%± vs. 7.0±%, respectively). Additionally, the number of ICM, total cells, and the ratios ICM: Total, ICM: TE, respectively, were greater (P < 0.05) after melatonin treatment compared with the control group (39.1 ± 2.8, 98.6 ± 5.7, 0.4 ± 0.01, and 0.7 ± 0.04 vs. 27.3 ± 2.9, 81.2 ± 5.8, 0.34 ± 0.01, and 0.52 ± 0.04, respectively). Blastocysts derived from adult cows had a greater number of TE (P = 0.01) and total embryonic cells (P = 0.0095) compared to the prepubertal donor group (63.5 ± 3.2 and 101.05 ± 4.8 vs. 48.9 ± 4.3 and 78.8 ± 6.5, respectively). Nevertheless, embryonic cell counting in embryos derived from prepubertal COCs equated to that observed from adult donors after melatonin exposure. In conclusion, these results indicate that the presence of melatonin during in vitro maturation improves cumulus-oocyte competence, embryo development, and quality by increasing the allocation of embryonic cells to the ICM compartment and the total number of embryonic cells in both adult and prepubertal bovine donors.

Dot blots of solubilized extracellular matrix allow quantification of human antibodies bound to epitopes present in decellularized porcine pulmonary heart valves

BACKGROUND

The present study reports the development of a sensitive dot blot protocol for determining the level of preformed antibodies against porcine heart valve tissue derived from wild-type (WT) and α-Gal-KO (GGTA1-KO) pigs in human sera.

METHODS

The assay uses decellularized and solubilized heart valve tissue; antibody binding found in this dot blot assay could be correlated with antibody titers of preformed anti-α-Gal and anti-Neu5Gc antibodies detected by a sensitive ELISA.

RESULTS

The ultimate protocol had an inter-assay variance of 9.5% and an intra-assay variance of 9.2%, showing that the test is reliable and highly reproducible. With the aid of this dot blot assay, we found significant variation with regard to antibody contents among twelve human sera. Binding of preformed antibodies to WT tissue was significantly higher than to GGTA1-KO tissue.

CONCLUSIONS

The dot blot assay described herein could be a valuable tool to measure preformed antibody levels in human sera against unknown epitopes on decellularized tissue prior to implantation. Ultimately, this prescreening may allow a matching of the porcine xenograft with the respective human recipients in demand and thus may become an important tool for graft long-term survival similar to current allotransplantation settings.

CRISPR/Cas12a mediated knock-in of the Polled Celtic variant to produce a polled genotype in dairy cattle

In modern livestock farming horned cattle pose an increased risk of injury for each other as well as for the farmers. Dehorning without anesthesia is associated with stress and pain for the calves and raises concerns regarding animal welfare. Naturally occurring structural variants causing polledness are known for most beef cattle but are rare within the dairy cattle population. The most common structural variant in beef cattle consists of a 202 base pair insertion-deletion (Polled Celtic variant). For the generation of polled offspring from a horned Holstein-Friesian bull, we isolated the Polled Celtic variant from the genome of an Angus cow and integrated it into the genome of fibroblasts taken from the horned bull using the CRISPR/Cas12a system (formerly Cpf1). Modified fibroblasts served as donor cells for somatic cell nuclear transfer and reconstructed embryos were transferred into synchronized recipients. One resulting pregnancy was terminated on day 90 of gestation for the examination of the fetus. Macroscopic and histological analyses proved a polled phenotype. The remaining pregnancy was carried to term and delivered one calf with a polled phenotype which died shortly after birth. In conclusion, we successfully demonstrated the practical application of CRISPR/Cas12a in farm animal breeding and husbandry.

Increasing methylation of sperm rDNA and other repetitive elements in the aging male mammalian germline

In somatic cells/tissues, methylation of ribosomal DNA (rDNA) increases with age and age‐related pathologies, which has a direct impact on the regulation of nucleolar activity and cellular metabolism. Here, we used bisulfite pyrosequencing and show that methylation of the rDNA transcription unit including upstream control element (UCE), core promoter, 18S rDNA, and 28S rDNA in human sperm also significantly increases with donor's age. This positive correlation between sperm rDNA methylation and biological age is evolutionarily conserved among mammals with widely different life spans such as humans, marmoset, bovine, and mouse. Similar to the tandemly repeated rDNA, methylation of human α‐satellite and interspersed LINE1 repeats, marmoset α‐satellite, bovine alpha‐ and testis satellite I, mouse minor and major satellite, and LINE1‐T repeats increases in the aging male germline, probably related to their sperm histone packaging. Deep bisulfite sequencing of single rDNA molecules in human sperm revealed that methylation does not only depend on donor's age, but also depend on the region and sequence context (A vs. G alleles). Both average rDNA methylation of all analyzed DNA molecules and the number of fully (>50%) methylated alleles, which are thought to be epigenetically silenced, increase with donor's age. All analyzed CpGs in the sperm rDNA transcription unit show comparable age‐related methylation changes. Unlike other epigenetic aging markers, the rDNA clock appears to operate in similar ways in germline and soma in different mammalian species. We propose that sperm rDNA methylation, directly or indirectly, influences nucleolar formation and developmental potential in the early embryo.

In Vitro and In Vivo Interspecies Chimera Assay Using Early Pig Embryos

Chimeric pigs harboring organs derived from human stem cells are promising for patient-specific regenerative therapies. Induced pluripotent stem cells (iPSCs) can contribute to all cell types of the fetus, including germline after injection into embryos. However, ethical concerns prohibit testing human iPSCs in chimera assays. Here, we evaluated porcine embryos as hosts for an interspecies chimera assay using iPSCs from either cynomolgus monkeys (cyiPSCs) or mouse (miPSCs). To establish an in vitro culture system compatible for cyiPSCs and porcine embryos, we determined blastocyst development in eight different stem cell media. The highest developmental rates of blastocysts were achieved in Knockout Dulbecco's modified Eagle's medium with 20% knockout serum replacement. We found that cyiPSCs injected into porcine embryos survived in vitro and were mostly located in the trophectoderm (TE). Instead, when miPSCs were injected into porcine embryos, the cells rapidly proliferated. The behavior of chimeras developed in vitro was recapitulated in vivo; cyiPSCs were observed in the TE, but not in the porcine epiblast. However, when miPSCs were injected into in vivo derived porcine embryos, mouse cells were found in both, the epiblast and TE. These results demonstrate that porcine embryos could be useful for evaluating the interspecies chimera-forming ability of iPSCs from different species.

Triple (GGTA1, CMAH, B2M) modified pigs expressing an SLA class Ilow phenotype-Effects on immune status and susceptibility to human immune responses

Porcine xenografts lacking swine leukocyte antigen (SLA) class I are thought to be protected from human T cell responses. We have previously shown that SLA class I deficiency can be achieved in pigs by CRISPR/Cas9-mediated deletion of β₂ -microglobulin (B2M). Here, we characterized another line of genetically modified pigs in which targeting of the B2M locus did not result in complete absence of B2M and SLA class I but rather in significantly reduced expression levels of both molecules. Residual SLA class I was functionally inert, because no proper differentiation of the CD8⁺ T cell subset was observed in B2M^low pigs. Cells from B2M^low pigs were less capable in triggering proliferation of human peripheral blood mononuclear cells in vitro, which was mainly due to the nonresponsiveness of CD8⁺ T cells. Nevertheless, cytotoxic effector cells developing from unaffected cell populations (eg, CD4⁺ T cells, natural killer cells) lysed targets from both SLA class I⁺ wildtype and SLA class I^low pigs with similar efficiency. These data indicate that the absence of SLA class I is an effective approach to prevent the activation of human CD8⁺ T cells during the induction phase of an anti-xenograft response. However, cytotoxic activity of cells during the effector phase cannot be controlled by this approach.

Generating low immunogenic pig pancreatic islet cell clusters for xenotransplantation

Xenotransplantation of pancreatic islets offers a promising alternative to overcome the shortage of allogeneic donors. Despite significant advances, either immune rejection or oxygen supply in immune protected encapsulated islets remains major bottlenecks for clinical application. To decrease xenogeneic immune responses, we generated tissue engineered swine leucocyte antigen (SLA)‐silenced islet cell clusters (ICC). Single‐cell suspensions from pancreatic islets were generated by enzymatic digestion of porcine ICCs. Cells were silenced for SLA class I and class II by lentiviral vectors encoding for short hairpin RNAs targeting beta2‐microglobulin or class II transactivator, respectively. SLA‐silenced ICCs‐derived cells were then used to form new ICCs in stirred bioreactors in the presence of collagen VI. SLA class I silencing was designed to reach a level of up to 89% and class II by up to 81% on ICCs‐derived cells. Xenogeneic T cell immune responses, NK cell and antibody‐mediated cellular‐dependent immune responses were significantly decreased in SLA‐silenced cells. In stirred bioreactors, tissue engineered islets showed the typical 3D structure and insulin production. These data show the feasibility to generate low immunogenic porcine ICCs after single‐cell engineering and post‐transduction islet reassembling that might serve as an alternative to allogeneic pancreatic islet cell transplantation.

Discovery and quantification of a widespread methane ebullition event in a coastal inlet (Baltic Sea) using a novel sonar strategy

How much of the greenhouse gas methane is transported from the seafloor to the atmosphere is unclear. Here, we present data describing an extensive ebullition event that occurred in Eckernförde Bay, a shallow gas-hosting coastal inlet in the Baltic Sea, in the fall of 2014. A weak storm induced hydrostatic pressure fluctuations that in turn stimulated gas ebullition from the seabed. In a finely tuned sonar survey of the bay, we obtained a hydroacoustic dataset with exceptionally high sensitivity for bubble detection. This allowed us to identify 2849 bubble seeps rising within 28 h from the seafloor across the 90 km² study site. Based on our calculations, the estimated bubble-driven episodic methane flux from the seafloor across the bay is 1,900 μMol m⁻² d⁻¹. Our study demonstrates that storm-associated fluctuations of hydrostatic pressure induce bulk gas-driven ebullitions. Given the extensive occurrence of shallow gas-hosting sediments in coastal seas, similar ebullition events probably take place in many parts of the Western Baltic Sea. However, these are likely to be missed during field investigations, due to the lack of high-quality data acquisition during storms, such that atmospheric inputs of marine-derived methane will be highly underestimated.

First Observation of a Stable Highly Dissipative Divertor Plasma Regime on the Wendelstein 7-X Stellarator

For the first time, the optimized stellarator Wendelstein 7-X has operated with an island divertor. An operation regime in hydrogen was found in which the total plasma radiation approached the absorbed heating power without noticeable loss of stored energy. The divertor thermography recorded simultaneously a strong reduction of the heat load on all divertor targets, indicating almost complete power detachment. This operation regime was stably sustained over several energy confinement times until the preprogrammed end of the discharge. The plasma radiation is mainly due to oxygen and is located at the plasma edge. This plasma scenario is reproducible and robust at various heating powers, plasma densities, and gas fueling locations. These experimental results show that the island divertor concept actually works and displays good power dissipation potential, producing a promising exhaust concept for the stellarator reactor line.

Establishment of porcine and human expanded potential stem cells

We recently derived mouse expanded potential stem cells (EPSCs) from individual blastomeres by inhibiting the critical molecular pathways that predispose their differentiation. EPSCs had enriched molecular signatures of blastomeres and possessed developmental potency for all embryonic and extra-embryonic cell lineages. Here, we report the derivation of porcine EPSCs, which express key pluripotency genes, are genetically stable, permit genome editing, differentiate to derivatives of the three germ layers in chimeras and produce primordial germ cell-like cells in vitro. Under similar conditions, human embryonic stem cells and induced pluripotent stem cells can be converted, or somatic cells directly reprogrammed, to EPSCs that display the molecular and functional attributes reminiscent of porcine EPSCs. Importantly, trophoblast stem-cell-like cells can be generated from both human and porcine EPSCs. Our pathway-inhibition paradigm thus opens an avenue for generating mammalian pluripotent stem cells, and EPSCs present a unique cellular platform for translational research in biotechnology and regenerative medicine.

Possible detrimental effects of beta-2-microglobulin knockout in pigs

BACKGROUND

Despite major improvements in pig-to-primate xenotransplantation, long-term survival of xenografts is still challenging. The major histocompatibility complex (MHC) class I, which is crucial in cellular immune response, is an important xenoantigen. Abrogating MHC class I expression on xenografts might be beneficial for extending graft survival beyond current limits.

METHODS

In this study, we employed the CRISPR/Cas9 system to target exon 2 of the porcine beta-2-microglobulin (B2M) gene to abrogate SLA class I expression on porcine cells. B2M-KO cells served as donor cells for somatic cell nuclear transfer, and cloned embryos were transferred to three recipient sows. The offspring were genotyped for mutations at the B2M locus, and blood samples were analyzed via flow cytometry for the absence of SLA class I molecules.

RESULTS

Pregnancies were successfully established and led to the birth of seven viable piglets. Genomic sequencing proved that all piglets carried biallelic modifications at the B2M locus leading to a frameshift, a premature stop codon, and ultimately a functional knockout. However, survival times of these animals did not exceed 4 weeks due to unexpected disease processes.

CONCLUSION

Here, we demonstrate the feasibility of generating SLA class I knockout pigs by targeting the porcine beta-2-microglobulin gene using the CRISPR/Cas9 system. Additionally, our findings indicate for the first time that this genetic modification might have a negative impact on the viability of the animals. These issues need to be solved to unveil the real value for xenotransplantation in the future.

Comparative gene expression profiling of pig-derived iPSC-like cells: Effects of induced pluripotency on expression of porcine endogenous retrovirus (PERV)

BACKGROUND

Porcine induced pluripotent stem cells (piPSCs) offer an alternative strategy in xenotransplantation (XTx). As human endogenous retroviruses (HERV), particularly HERV-K, are highly expressed in natural human stem cells, we compared the expression of porcine endogenous retroviruses (PERV) and retrotransposon LINE-1 (L1) open reading frames 1 and 2 (pORF1 and pORF2) in different piPSC-like cell lines with their progenitors (porcine fetal fibroblasts, pFF).

METHODS

Cells reprogrammed via Sleeping Beauty-transposed transcription factors were cultured and analyzed on a custom-designed microarray representing the reference pig genome. Data were complemented by qRT-PCR and reverse transcriptase (RT) assay.

RESULTS

The expression profiles revealed that 8515 of 26 967 targets were differentially expressed. A total of 4443 targets showed log₂ expression ratio >1, and 4072 targets showed log₂ expression ratio less than -1 with 0.05 P-value threshold. Approximately ten percent of the targets showed highly significant expression ratios with log₂ ≥4 or ≤-4. Besides this general switch in cellular gene expression that was accompanied by an altered morphology, expression of both PERV and L1 pORF1/pORF2 was significantly enhanced. piPSC-like cells revealed a 10-fold to 100-fold higher transcription of the viral PERV-A and PERV-B envelope genes (env), viral protease/polymerase (prt/pol), and L1 elements. No functional retrovirus could be detected under these conditions.

CONCLUSION

Epigenetic reprogramming has functional impact on retrotransposons. Thus, the induction of pig-derived pluripotent cells influences their PERV expression profile. Data emphasize the necessity to focus on animals, which show non-functional endogenous viral background to ensure virological safety.

182 Establishment of expanded potential embryonic stem cell lines from porcine embryos

The domestic pig is an excellent large animal in biomedical medicine and holds great potential for testing the clinical safety and efficacy of stem cell therapies. Previously, numerous studies reported the derivation of porcine embryonic stem cell (ESC)-like lines, but none of these lines fulfilled the stringent criteria for true pluripotent germline competent ESC. Here, we report the first establishment of porcine expanded potential stem cells (pEPSC) from parthenogenetic and in vivo-derived blastocysts. A total of 12 cell lines from parthenogenetic blastocysts from Day 7 (12/24) and 26 cell lines from in vivo-derived blastocysts from Day 5 (26/27) were established using defined stem cell culture conditions. These cells closely resembled mouse ESC with regard to morphology, formed compact colonies with high nuclear/cytoplasmic ratios, and could be maintained in vitro for more than 40 passages with a normal karyotype. The pEPSC expressed key pluripotency genes, including OCT4, NANOG, SOX2, and SALL4 at similar levels as porcine blastocysts. Immunostaining analysis confirmed expression of critical cell surface markers SSEA-1 and SSEA-4 in pEPSC. The EPSC differentiated in vitro into tissues expressing markers of the 3 germ layers: SOX7, AFP, T, DES, CRABP2, α-SMA, β-tubulin, PAX6, and, notably, the trophoblast markers HAND1, GATA3, PGF, and KRT7. After injection into immunocompromised mice, the pEPSC formed teratomas with derivatives of the 3 germ layers and placental lactogen-1 (PL-1)-positive trophoblast-like cells. Additionally, pEPSC cultured in vitro under conditions specific for germ cells formed embryoid bodies, which contained ~9% primordial germ cell (PGC)-like cells (PGCLC) that expressed PGC-specific genes, including NANOS3, BLIMP1, TFAP2C, CD38, DND1, KIT, and OCT4 as detected by quantitative RT-PCR and immunostaining. Next, we examined the in vivo differentiation potential of pEPSC and injected pEPSC stably expressing the CAG-H2B-mCherry transgene reporter into porcine embryos. The donor cells proliferated and were localised in both the trophectoderm and inner cell mass of the blastocysts cultured in vitro. After transfer to 3 recipient sows, chimeric embryos implanted and a total of 45 fetuses were recovered on Days 26 to 28. Flow cytometry of single cells collected from embryonic and extraembryonic tissues of the fetuses revealed mCherry+ cells in 7 conceptuses, in both the placenta and embryonic tissues; in 3 chimeric conceptuses, mCherry+ cells were exclusively found in embryonic tissues; and in 2 conceptuses, mCherry+ cells were exclusively localised in the placenta. The contribution of the mCherry+ cells was low (0.4-1.7%), but they were found and co-detected in multiple porcine embryonic tissues using tissue lineage-specific markers, including SOX2, TUJ1, GATA4, SOX17, AFP, α-SMA, and trophoblast markers PL-1 and KRT7 in the placental cells. The successful establishment of pEPSC represents a major step forward in stem cell research and provides cell lines with the unique state of cellular potency useful for genetic engineering and unravelling pluripotency regulation in pigs.

Towards a new image processing system at Wendelstein 7-X: From spatial calibration to characterization of thermal events

Wendelstein 7-X (W7-X) is the most advanced fusion experiment in the stellarator line and is aimed at proving that the stellarator concept is suitable for a fusion reactor. One of the most important issues for fusion reactors is the monitoring of plasma facing components when exposed to very high heat loads, through the use of visible and infrared (IR) cameras. In this paper, a new image processing system for the analysis of the strike lines on the inboard limiters from the first W7-X experimental campaign is presented. This system builds a model of the IR cameras through the use of spatial calibration techniques, helping to characterize the strike lines by using the information given by real spatial coordinates of each pixel. The characterization of the strike lines is made in terms of position, size, and shape, after projecting the camera image in a 2D grid which tries to preserve the curvilinear surface distances between points. The description of the strike-line shape is made by means of the Fourier Descriptors.

A divertor scraper observation system for the Wendelstein 7-X stellarator

Two graphite divertor elements called scrapers have been installed on the Wendelstein 7-X stellarator in the throat of the magnetic island divertor. To diagnose one, we have designed, built, calibrated, and installed a new infrared/visible imaging endoscope system to enable detailed observations of the plasma interactions and heat loads at one of the scrapers and the nearby divertor surfaces. The new system uses a shuttered pinhole-protected pair of 90° off-axis 228 mm focal length aluminum parabolic mirrors, and two flat turning metal mirrors, to send light to a sapphire vacuum window 1.6 meters away, beyond which we have co-located telephoto lens-based infrared and visible cameras. The back-to-back off-axis parabolas serve to cancel out most aberrations, enabling the use of off-the-shelf commercial optics outside of the vessel. For the infrared, we use a 3-5 μm 1-megapixel FLIR SC8303HD camera and for the visible, a 5-megapixel CMOS PCO 5.5 edge camera. A short 1-m quartz pickoff fiber is used to send 200-1100 nm light to a compact spectrometer, also located in the same iron shield box as the cameras. The camera field of view covers the 700 mm length of the scraper, and includes locations monitored by thermocouples and Langmuir probes embedded in some of the scraper tiles. Predicted and actual optical test performances of the overall system are compared.

Anticonvulsant effects after grafting of rat, porcine, and human mesencephalic neural progenitor cells into the rat subthalamic nucleus

Cell transplantation based therapy is a promising strategy for treating intractable epilepsies. Inhibition of the subthalamic nucleus (STN) or substantia nigra pars reticulata (SNr) is a powerful experimental approach for remote control of different partial seizure types, when targeting the seizure focus is not amenable. Here, we tested the hypothesis that grafting of embryonic/fetal neural precursor cells (NPCs) from various species (rat, human, pig) into STN or SNr of adult rats induces anticonvulsant effects. To rationally refine this approach, we included NPCs derived from the medial ganglionic eminence (MGE) and ventral mesencephalon (VM), both of which are able to develop a GABAergic phenotype. All VM- and MGE-derived cells showed intense migration behavior after grafting into adult rats, developed characteristics of inhibitory interneurons, and survived at least up to 4 months after transplantation. By using the intravenous pentylenetetrazole (PTZ) seizure threshold test in adult rats, transient anticonvulsant effects were observed after bilateral grafting of NPCs derived from human and porcine VM into STN, but not after SNr injection (site-specificity). In contrast, MGE-derived NPCs did not cause anticonvulsant effects after grafting into STN or SNr (cell-specificity). Neither induction of status epilepticus by lithium-pilocarpine to induce neuronal damage prior to the PTZ test nor pretreatment of MGE cells with retinoic acid and potassium chloride to increase differentiation into GABAergic neurons could enhance anticonvulsant effectiveness of MGE cells. This is the first proof-of-principle study showing anticonvulsant effects by bilateral xenotransplantation of NPCs into the STN. Our study highlights the value of VM-derived NPCs for interneuron-based cell grafting targeting the STN.

Gene-specific profiling of DNA methylation and mRNA expression in bovine oocytes derived from follicles of different size categories

Epigenetic changes, such as DNA methylation, play an essential role in the acquisition of full developmental competence by mammalian oocytes during the late follicular growth phase. Here we used the bovine model to investigate the DNA methylation profiles of seven candidate genes (imprinted: bH19, bSNRPN; non-imprinted: bZAR1, bDNMT3A, bOCT4, bDNMT3 Lo and bDNMT3 Ls) and the mRNA expression of nine candidate genes (imprinted: bSNRPN, bPEG3, bIGF2R; non-imprinted: bPRDX1, bDNMT1B, bDNMT3A, bZAR1, bHSF1 and bNLRP9) in oocytes from antral follicles of three different size classes (≤2mm, 3-5mm, ≥6mm) to unravel the epigenetic contribution to this process. We observed an increased number of aberrantly methylated alleles in bH19, bSNRPN and bDNMT3 Lo of oocytes from small antral follicles (≤2mm), correlating with lower developmental competence. Furthermore, we detected an increased frequency of CpG sites with an unclear methylation status for DNMT3 Ls, specifically in oocytes from follicles ≥6mm, predominantly at three CpG positions (CpG2, CpG7 and CpG8), of which CpG7 is a potential regulatory site. No major differences in mRNA expression were observed, indicating that the transcriptional machinery may not yet be active during the follicular growth phase. Our results support the notion that a follicle diameter of ~2mm is a critical stage for establishing DNA methylation profiles and indicate a link between DNA methylation and the acquisition of oocyte developmental competence.

Efficient Knock-in of a Point Mutation in Porcine Fibroblasts Using the CRISPR/Cas9-GMNN Fusion Gene

During CRISPR/Cas9 mediated genome editing, site-specific double strand breaks are introduced and repaired either unspecific by non-homologous end joining (NHEJ) or sequence dependent by homology directed repair (HDR). Whereas NHEJ-based generation of gene knock-out is widely performed, the HDR-based knock-in of specific mutations remains a bottleneck. Especially in primary cell lines that are essential for the generation of cell culture and animal models of inherited human diseases, knock-in efficacy is insufficient and needs significant improvement. Here, we tested two different approaches to increase the knock-in frequency of a specific point mutation into the MYH7-gene in porcine fetal fibroblasts. We added a small molecule inhibitor of NHEJ, SCR7 (5,6-bis((E)-benzylideneamino)-2-mercaptopyrimidin-4-ol), during genome editing and screened cell cultures for the point mutation. However, this approach did not yield increased knock-in rates. In an alternative approach, we fused humanized Cas9 (hCas9) to the N-terminal peptide of the Geminin gene (GMNN). The fusion protein is degraded in NHEJ-dominated cell cycle phases, which should increase HDR-rates. Using hCas9-GMNN and point mutation-specific real time PCR screening, we found a two-fold increase in genome edited cell cultures. This increase of HDR by hCas9-GMNN provides a promising way to enrich specific knock-in in porcine fibroblast cultures for somatic cloning approaches.

Successful knock-in of Hypertrophic Cardiomyopathy-mutation R723G into the MYH7 gene mimics HCM pathology in pigs

Familial Hypertrophic Cardiomyopathy (HCM) is the most common inherited cardiac disease. About 30% of the patients are heterozygous for mutations in the MYH7 gene encoding the ß-myosin heavy chain (MyHC). Hallmarks of HCM are cardiomyocyte disarray and hypertrophy of the left ventricle, the symptoms range from slight arrhythmias to sudden cardiac death or heart failure. To gain insight into the underlying mechanisms of the diseases' etiology we aimed to generate genome edited pigs with an HCM-mutation. We used TALEN-mediated genome editing and successfully introduced the HCM-point mutation R723G into the MYH7 gene of porcine fibroblasts and subsequently cloned pigs that were heterozygous for the HCM-mutation R723G. No off-target effects were determined in the R723G-pigs. Surprisingly, the animals died within 24 h post partem, probably due to heart failure as indicated by a shift in the a/ß-MyHC ratio in the left ventricle. Most interestingly, the neonatal pigs displayed features of HCM, including mild myocyte disarray, malformed nuclei, and MYH7-overexpression. The finding of HCM-specific pathology in neonatal R723G-piglets suggests a very early onset of the disease and highlights the importance of novel large animal models for studying causative mechanisms and long-term progression of human cardiac diseases.

Developmental Competence and Epigenetic Profile of Porcine Embryos Produced by Two Different Cloning Methods

The "Dolly" based cloning (classical nuclear transfer, [CNT]) and the handmade cloning (HMC) are methods that are nowadays routinely used for somatic cloning of large domestic species. Both cloning protocols share several similarities, but differ with regard to the required in vitro culture, which in turn results in different time intervals until embryo transfer. It is not yet known whether the differences between cloned embryos from the two protocols are due to the cloning methods themselves or the in vitro culture, as some studies have shown detrimental effects of in vitro culture on conventionally produced embryos. The goal of this study was to unravel putative differences between two cloning methods, with regard to developmental competence, expression profile of a panel of developmentally important genes and epigenetic profile of porcine cloned embryos produced by either CNT or HMC, either with (D5 or D6) or without (D0) in vitro culture. Embryos cloned by these two methods had a similar morphological appearance on D0, but displayed different cleavage rates and different quality of blastocysts, with HMC embryos showing higher blastocyst rates (HMC vs. CNT: 35% vs. 10%, p < 0.05) and cell numbers per blastocyst (HMC vs. CNT: 31 vs. 23 on D5 and 42 vs. 18 on D6, p < 0.05) compared to CNT embryos. With regard to histone acetylation and gene expression, CNT and HMC derived cloned embryos were similar on D0, but differed on D6. In conclusion, both cloning methods and the in vitro culture may affect porcine embryo development and epigenetic profile. The two cloning methods essentially produce embryos of similar quality on D0 and after 5 days in vitro culture, but thereafter both histone acetylation and gene expression differ between the two types of cloned embryos.

Evaluation of Computer-assisted Image Enhancement in Minimal Invasive Endoscopic Surgery

Objectives: This paper focusses on the evaluation of the usage of computer-aided image processing methods for minimal invasive surgery. During video endoscopy of visceral cavities the images are displayed directly on the monitor without further processing. In the course of the operation the former good quality of the images decreases due to typical disturbances like bleeding, smoke or flying particles. These disturbances can be reduced by using image processing methods like color normalization, temporal filtering or equalization.

Methods: In this double-blinded analysis, 14 surgeons with different levels of experience evaluated 120 image pairs and 5 image sequences, directly comparing original and processed images or movies.

Results: Color normalization and equalization proved to significantly enhance video endoscopic images. With regard to temporal filtering, an improvement could be seen in the image sequences with filter size 5 being a greater enhancement than filter size 3. Comparing the state of experience and its influence on the results, it occurred that the experienced surgeons preferred the original color while altogether agreeing that the color-normalized images were better.

Conclusions: The results obtained in the present evaluation show that the image processing methods which were used can significantly improve the quality of video endoscopic images. As a result of this, necessary lavages of the operated area are reduced and a better overview and orientation for the surgeon can be reached.

Light Fields for Minimal Invasive Surgery Using an Endoscope Positioning Robot

Objectives: To generate a fast and robust 3-D visualization of the operation site during minimal invasive surgery.

Methods: Light fields are used to model and visualize the 3-D operation site during minimal invasive surgery. An endoscope positioning robot provides the position and orientation of the endoscope. The a priori unknown transformation from the endoscope plug to the endoscope tip (hand-eye transformation) can either be determined by a three-step algorithm, which includes measuring the endoscope length by hand or by using an automatic hand-eye calibration algorithm. Both methods are described in this paper and their respective computation times and accuracies are compared.

Results: Light fields were generated during real operations and in the laboratory. The comparison of the two methods to determine the unknown hand-eye transformation was done in the laboratory. The results which are being presented in this paper are: rendered images from the generated light fields, the calculated extrinsic camera parameters and their accuracies with respect to the applied hand-eye calibration method, and computation times.

Conclusion: Using an endoscope positioning robot and knowing the hand-eye transformation, the fast and robust generation of light fields for minimal invasive surgery is possible.

Efficient inhibition of African swine fever virus replication by CRISPR/Cas9 targeting of the viral p30 gene (CP204L)

African swine fever is a devastating viral disease of domestic and wild pigs against which no vaccine or therapy is available. Therefore, we applied the CRISPR (clustered regularly interspaced short palindromic repeats) – Cas9 nuclease system to target the double-stranded DNA genome of African swine fever virus (ASFV). To this end, a permissive wild boar lung (WSL) cell line was modified by stable transfection with a plasmid encoding Cas9 and a guide RNA targeting codons 71 to 78 of the phosphoprotein p30 gene (CP204L) of ASFV. Due to targeted Cas9 cleavage of the virus genome, plaque formation of ASFV was completely abrogated and virus yields were reduced by four orders of magnitude. The specificity of these effects could be demonstrated by using a natural ASFV isolate and escape mutants possessing nucleotide exchanges within the target sequence, which were not inhibited in the Cas9-expressing cell line. Growth of the cell line was not affected by transgene expression which, as well as virus inhibition, proved to be stable over at least 50 passages. Thus, CRISPR-Cas9 mediated targeting of the ASFV p30 gene is a valid strategy to convey resistance against ASF infection, which may also be applied in its natural animal host.

122 A New Maturation Medium Improves Porcine Embryo Production In Vitro

Recently (Spate et al. 2017 Reprod. Fertil. Dev. 29, 150), a new medium [TCM-199 supplemented with hCG 10 IU, pregnant mare serum gonadotropin (PMSG) 10 IU mL−1, fibroblast growth factor (FGF) 40 ng mL−1, leukemia inhibitory factor (LIF) 2000 U mL−1, IGF-1 20 ng mL−1, epidermal growth factor (EGF) 10 ng mL−1], termed FLI medium, was demonstrated to improve porcine oocyte maturation in vitro. The effects on embryo development and quality have not yet been investigated. The purpose of the present study was to compare the FLI medium in porcine in vitro embryo production (IVP) with our standard maturation medium (DMEM supplemented with 10 IU mL−1 PMSG and hCG, 50 ng mL−1 EGF, 100 ng mL−1 IGF1, and 5 ng mL−1 FGF). Briefly, gilt oocytes were collected via aspiration of follicles from abattoir ovaries and matured for 44 h in either FLI or standard DMEM medium at 39°C, 5% CO2 in humidified air. In vitro fertilization was performed with freshly ejaculated sperm (250,000 mL−1) of a multi-transgenic boar (GGTA1-KO/hCD46/hCD55/hCD59/hHO-1/hA20) by co-incubation with the matured oocytes in PGMTac4 medium for 4 h. Zygotes were washed twice and then cultured for 6 days in PZM3 medium. Development to the blastocyst stage was recorded at Day 6 of culture. Blastocysts were fixed and Hoechst33342 stained for counting the nuclei. Each of the experiments was repeated 3 times. In a second step, Day 5 blastocysts derived from the FLI medium were transferred to synchronized pubertal gilts to test the in vivo developmental competence of the IVF embryos. Maturation of oocytes in FLI medium resulted in a significantly higher blastocyst rate (49.3 vs. 13.5; P ≤ 0.001, Chi-squared test) and nuclei number (41.3 ± 12.2 vs. 35.3 ± 10.8; P ≤ 0.001, one-way ANOVA) compared with the standard medium, whereas the cleavage rate was not affected. Transfer of Day 5 blastocysts (average 35 embryos/recipient) derived from the FLI system using 8 recipients resulted in 7 pregnancies (87.5%) as determined by ultrasound scanning on Day 25 of gestation. At the time of writing, one recipient had delivered 5 healthy piglets after a gestation length of 114 days. Results indicate that the FLI medium significantly improves blastocyst rates and the cell number of the resulting blastocysts (Table 1) and yields pig IVF embryos with a high developmental capacity in vivo. By producing high-quality porcine embryos, this FLI-based IVF system provides an efficient method to modify the porcine genome by cytoplasmic microinjection of CRISPR/Cas molecules into IVF-derived zygotes. Table 1.Results of maturation of oocytes in FLI medium compared with DMEM

198 Germline-Specific Expression of the Murine Oct4-EGFP Transgene in the Pig

The Oct4 gene is crucial for undisturbed early embryonic development and maintenance of pluripotency in the mouse. It is found in mouse pre-implantation embryos after embryonic genome activation. After gastrulation, expression is restricted to germ cells. Limited research has been performed on OCT4 expression in the domestic pig, which is a valuable large animal model in biomedicine. Previously, we generated Oct4-EGFP reporter pigs carrying the genomic sequence of the murine Oct4 gene fused to the EGFP cDNA (Nowak-Imialek et al. 2011 Stem Cells Dev. 20, 1563-1575, 10.1089/scd.2010.0399). In the present study, we used this animal model to analyse the expression profile of the murine Oct4-EGFP transgene in porcine oocytes, in vivo-derived embryos (4-cell embryos, 8- to 16-cell embryos, morulae, and blastocysts) and ovaries. We studied whether the murine Oct4-EGFP transgene mimics the expression pattern of the endogenous OCT4 protein in transgenic pigs. Immature oocytes were isolated from ovaries of Oct4-EGFP transgenic sows (n = 5) using slicing methods. For collection of porcine embryos, wild-type sows were inseminated with sperm from an Oct4-EGFP transgenic boar. Sows were sacrificed 3, 4, and 5 days after insemination, and embryos were recovered by flushing oviducts and uterus and analysed by confocal microscopy. Ovaries obtained from female animals (5–12 months) were enzymatically dissociated and analysed using flow cytometry. Immature oocytes (n = 19) showed a very low, diffuse EGFP signal in cytoplasm. Embryos up to the 4-cell stage (n = 45) did not show Oct4-EGFP transgene expression. For the first time, EGFP fluorescence was detected at the 8-cell stage (n = 29) and a strong EGFP signal was observed in 16-cell stages and morulae (n = 53). In blastocysts from Day 5 (n = 40) EGFP fluorescence was not restricted to the inner cell mass (ICM), but was also seen in the trophectoderm (TE). Expression of EGFP was not detected in ovarian cells (n = 12). Thereafter, we analysed the expression pattern of endogenous OCT4 protein by immunostaining in nontransgenic porcine oocytes and pre-implantation embryos. As in Oct4-EGFP transgenic embryos, no expression of OCT4 was observed in 4-cell embryos (n = 12). Nuclear staining first became visible at the 8-cell stage (n = 12), with a strong signal observed in 16-cell stages and morulae (n = 18). In blastocysts from Day 5 (n = 26), both ICM and TE cell nuclei showed expression of OCT4 protein. These results demonstrate that the Oct4-EGFP transgene expression pattern reproduces the endogenous OCT4 protein expression profile in porcine oocytes and pre-implantation embryos. The Oct4-EGFP transgene was first detected at the 8-cell stage, consistent with embryonic genome activation, which is initiated at the 4-cell stage. However, Oct4-EGFP expression was not detected in ovarian cells. This might be related to the very low expression pattern of the Oct4-EGFP transgene in primary oocytes. In summary, the Oct4-EGFP transgene in the pig provides a useful marker for monitoring pluripotency in pre-implantation embryos after embryonic genome activation. In ongoing experiments, we are analysing the expression profile of the Oct4-EGFP transgene and endogenous OCT4 protein in porcine pre-implantation embryos from Days 8 and 11.

Mouse iPSC generated with porcine reprogramming factors as a model for studying the effects of non-silenced heterologous transgenes on pluripotency

Mouse somatic cells can be reprogrammed to pluripotency by the ectopic expression of four pluripotency transcription factors, Oct4, Sox2, cmyc, and Klf4. Usually, silencing of the exogenous reprogramming factors is considered to be essential for complete reprogramming and differentiation. In the vast majority of studies, murine pluripotency transcription factor sequences have been used for the reprogramming of mouse fibroblasts to induced pluripotent stem cells (iPSC). The effectiveness of xenogeneic transcription factors in miPSC generation has not yet been investigated in detail. Here, we evaluated transposon-based vectors with four porcine pluripotency factors for their ability to reprogram mouse fetal fibroblasts (MEFs) harboring an Oct4-EGFP reporter construct to pluripotency. Additionally, we examined the effects of the non-silenced heterologous transgenes on the expression levels of key endogenous pluripotency markers and the differentiation capacities of the miPSC. Within 8 days of transfection with porcine reprogramming transcription factors the MEFs acquired typical compact miPSC morphology and upregulated expression of endogenous Oct4 and other critical pluripotency genes. Consequently, the transgenes under the control of the TetO promoter became silenced, while the CAG-controlled constructs were expressed throughout the period of culture. Despite the continuous transgene expression, the CAG-miPSC showed normal morphology and were capable of differentiation into the three primary germ layers in vitro and in vivo. However, the expression levels of important endogenous pluripotency markers, Klf4, c-myc, Rex1, and Utf1, were significantly lower in CAG-miPSC compared with TetO-miPSC with silenced reprogramming cassettes. Surprisingly, the endogenous Oct4 and Sox2 expression levels were not affected by the residual transgene expression. Our results suggest that porcine reprogramming transcription factors are suitable for production of miPSC, but silencing of the heterologous transgenes may be necessary for complete reprogramming to pluripotency.

148 EFFECTS OF CAFFEINE SUPPLEMENTATION ON BOVINE OOCYTE DEVELOPMENTAL CAPACITY

Oocyte culture in the presence of the nonspecific competitive phosphodiesterase inhibitor caffeine has been reported to increase developmental capacity of oocytes in different mammalian species. Here, we evaluated the effects of caffeine supplementation during the final phase of in vitro maturation (IVM) on developmental rates and blastocyst cell numbers. Bovine ovaries were collected from a local abattoir. A total of 1142 cumulus-oocyte-complexes were obtained by slicing. Cumulus-oocyte complexes were either in vitro matured for 24 h (Standard) or matured for 20 h followed by additional culture for 6 h in fresh IVM medium supplemented with 10 mM caffeine (Caffeine 6 h). In vitro fertilization was performed for 19 h using frozen-thawed sperm from 2 different bulls. After IVF, presumptive zygotes were cultured in vitro for 8 days until the blastocyst stage. Cleavage and blastocyst rates were evaluated 3 and 8 days after IVF, respectively. Expanded blastocysts from the different treatments were submitted to differential staining. SAS/STAT software (SAS Institute Inc., Cary, NC, USA) was used to evaluate cleavage and blastocyst rates using the Glimmix procedure and blastocyst cell numbers were compared using the linear model procedure. Cleavage rates were lower using caffeine for bull B and blastocyst production decreased for bull A. Caffeine treatment increased inner cell mass (ICM) number for bull B and decreased trophectoderm (TE) and total cell numbers for bull A. However, similar TE and total cells were obtained for bull B (Table 1; P < 0.05). Results show that developmental competence can be affected by caffeine supplementation at the final phase of IVM probably due to oocyte-sperm interaction changes. Table 1. In vitro developmental competence of oocytes cultured with caffeine at the end of IVM

3 SIRT1—A POSSIBLE MARKER FOR REPRODUCTIVE AGING OF IN VIVO-DERIVED BOVINE OOCYTES?

Maternal aging-associated reduction of oocyte viability is a common feature in mammals. Effective measures to counteract this process have not yet been developed. Cows are commonly used as a model of early human development, including maternal aging, because both species share a very high degree of similarity, including follicle selection, cleavage and blastocyst formation and a long reproductive lifespan. SIRT1, a member of the Sirtuin family, deacetylates transcriptional regulators localised in the nucleus and cytoplasm by a NAD+-dependent mechanism. Resveratrol (3,4′,5-trihydroxystilbene) is an antioxidant identified in various plant species and red wine which enhances SIRT1 activity. Based on these observations, the goal of the present study was to examine, if SIRT1 gene and protein expression is either affected by maternal age and/or can be modulated by resveratrol. Cumulus-oocyte-complexes of prepubertal (5–6 months old) and adult/aged (2 to 8 lactation) cows were collected by ovum pick-up twice a week. Medium for in vitro maturation (TCM 199) and in vitro fertilization (FertTalp) was supplemented with 20 µL of Resveratrol® (Sigma-Aldrich, Buchs, Switzerland) to get a final concentration of 2 µM Resveratrol respectively. Standard (TCM 199 and FertTalp) media without Resveratol were used as control. Cleavage rates and blastocyst formation were evaluated. Comprehensive gene expression assays of germinal vesicle and metaphase II (MII)-stage oocytes and blastocyst were conducted using next-generation sequencing technology. Finally, SIRT1 protein expression in oocytes and blastocysts were analysed by fluorescence immunostaining under a confocal microscope (LSM510, Zeiss, Germany) and relative fluorescent intensity was calculated. The cleavage rates of adult and prepubertal donors did not differ significantly among the treatments (standard protocol: 56.5 ± 5.4% for adult and 53.0 ± 4.7% for prepubertal donors, Resveratrol supplemented protocol: 62.1 ± 4.3% for cows and 63.6 ± 3.9% for calves). The blastocyst rates were slightly enhanced in the Resveratrol supplemented groups (cows: 34.2 ± 3.8% and calves: 33.1 ± 4.2%) compared to those of standard protocol (cows: 27.5 ± 4.8% and calves: 26.4 ± 3.3%). Relative mRNA abundance levels of SIRT1 were lower in oocytes and blastocysts derived from cows than in those derived from their younger counterparts (2.8-fold change; P = 0.05), but did not differ significantly among treatment groups. Protein expression profiles revealed that bovine SIRT1 was localised in the nucleus. The relative fluorescence levels of SIRT1 were significantly lower (221 ± 34 FIU) in control groups compared to the resveratrol treated groups (865 ± 45 FIU, respectively; P = 0.05). Additionally, SIRT1 protein levels were significantly higher in MII-oocytes (1255 ± 56 FIU) and blastocysts (984 ± 26 FIU) derived from calves compared with their older counterparts (442 ± 37 FIU and 310 ± 23 FIU, respectively, P = 0.05). In conclusion, these results indicate that resveratrol affects SIRT1 protein expression in oocytes and blastocysts of donors in different age. Thus, we hypothesise that SIRT1 is a reliable marker for reproductive aging, which could also be useful for better understanding of human infertility caused by aging.

Overview of diagnostic performance and results for the first operation phase in Wendelstein 7-X (invited)

Wendelstein 7-X, a superconducting optimized stellarator built in Greifswald/Germany, started its first plasmas with the last closed flux surface (LCFS) defined by 5 uncooled graphite limiters in December 2015. At the end of the 10 weeks long experimental campaign (OP1.1) more than 20 independent diagnostic systems were in operation, allowing detailed studies of many interesting plasma phenomena. For example, fast neutral gas manometers supported by video cameras (including one fast-frame camera with frame rates of tens of kHz) as well as visible cameras with different interference filters, with field of views covering all ten half-modules of the stellarator, discovered a MARFE-like radiation zone on the inboard side of machine module 4. This structure is presumably triggered by an inadvertent plasma-wall interaction in module 4 resulting in a high impurity influx that terminates some discharges by radiation cooling. The main plasma parameters achieved in OP1.1 exceeded predicted values in discharges of a length reaching 6 s. Although OP1.1 is characterized by short pulses, many of the diagnostics are already designed for quasi-steady state operation of 30 min discharges heated at 10 MW of ECRH. An overview of diagnostic performance for OP1.1 is given, including some highlights from the physics campaigns.

Synthetic plasma edge diagnostics for EMC3-EIRENE, highlighted for Wendelstein 7-X

Interpretation of spectroscopic measurements in the edge region of high-temperature plasmas can be a challenge since line of sight integration effects make direct interpretation in terms of quantitative, local emission strengths often impossible. The EMC3-EIRENE code-a 3D fluid edge plasma and kinetic neutral gas transport code-is a suitable tool for full 3D reconstruction of such signals. A versatile synthetic diagnostic module has been developed recently which allows the realistic 3D setup of various plasma edge diagnostics to be captured. We highlight these capabilities with two examples for Wendelstein 7-X (W7-X): a visible camera for the analysis of recycling, and a coherent-imaging system for velocity measurements.

The Influence of Interspecies Somatic Cell Nuclear Transfer on Epigenetic Enzymes Transcription in Early Embryos

One of the main reason for the incorrect development of embryos derived from somatic cell nuclear transfer is caused by insufficient demethylation of injected somatic chromatin to a state comparable with an early embryonic nucleus. It is already known that the epigenetic enzymes transcription in oocytes and early embryos of several species including bovine and porcine zygotes is species-dependent process and the incomplete DNA methylation correlates with the nuclear transfer failure rate in mammals. In this study the transcription of DNA methyltransferase 1 and 3a (DNMT1, DNMT3a) genes in early embryonic stages of interspecies (bovine, porcine) nuclear transfer embryos (iSCNT) by RT-PCR were analyzed. Coming out from the diverse timing of embryonic genome activation (EGA) in porcine and bovine preimplantation embryos, the intense effect of ooplasm on transferred somatic cell nucleus was expected. In spite of the detection of ooplasmic DNA methyltransferases, the somatic genes for DNMT1 and DNMT3a enzymes were not expressed and the development of intergeneric embryos stopped at the 4-cell stage. Our results indicate that the epigenetic reprogramming during early mammalian development is strongly influenced by the ooplasmic environment.

DNA methylation and mRNA expression of developmentally important genes in bovine oocytes collected from donors of different age categories

Epigenetic changes are critical for the acquisition of developmental potential by oocytes and embryos, yet these changes may be sensitive to maternal ageing. Here, we investigated the impact of maternal ageing on DNA methylation and mRNA expression in a panel of eight genes that are critically involved in oocyte and embryo development. Bovine oocytes were collected from donors of three different age categories-prepubertal (9-12 months old), mature (3-7 years old), and aged (8-11 years old)-and were analyzed for gene-specific DNA methylation (bTERF2, bREC8, bBCL-XL, bPISD, bBUB1, bDNMT3Lo, bH19, and bSNRPN) and mRNA expression (bTERF2, bBCL-XL, bPISD, and bBUB1). A total of 1,044 alleles with 88,740 CpGs were amplified and sequenced from 362 bovine oocytes. Most of the detected molecules were either fully methylated or completely unmethylated. Only 9 out of 1,044 alleles (<1%) were abnormally methylated (>50% of CpGs with an aberrant methylation status), and seven of the nine abnormally methylated alleles were within only two candidate genes (bDNMT3Lo and bH19). No significant differences were detected with regard to mRNA expression between oocytes from the three groups of donors. These results suggest that genes predominantly important for early embryo development (bH19 and bDNMT3Lo) are less resistant to abnormal methylation than genes critically involved in oocyte development (bTERF2, bBCL-XL, bPISD, bBUB1, and bSNRPN). Establishment of DNA methylation in bovine oocytes seems to be largely resistant to changes caused by maternal ageing, irrespective of whether the genes are critical to achieve developmental competence in oocytes or early embryos. Mol. Reprod. Dev. 83: 802-814, 2016 © 2016 Wiley Periodicals, Inc.

Efficient production of biallelic GGTA1 knockout pigs by cytoplasmic microinjection of CRISPR/Cas9 into zygotes

BACKGROUND

Xenotransplantation is considered to be a promising solution to the growing demand for suitable donor organs for transplantation. Despite tremendous progress in the generation of pigs with multiple genetic modifications thought to be necessary to overcoming the severe rejection responses after pig-to-non-human primate xenotransplantation, the production of knockout pigs by somatic cell nuclear transfer (SCNT) is still an inefficient process. Producing genetically modified pigs by intracytoplasmic microinjection of porcine zygotes is an alluring alternative. The porcine GGTA1 gene encodes for the α1,3-galactosyltransferase that synthesizes the Gal epitopes on porcine cells which constitute the major antigen in a xenotransplantation setting. GGTA1-KO pigs have successfully been produced by transfecting somatic cells with zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), or CRISPR/Cas targeting GGTA1, followed by SCNT.

METHODS

Here, we microinjected a CRISPR/Cas9 vector coding for a single-guide RNA (sgRNA) targeting exon 8 of the GGTA1 gene into the cytoplasm of 97 in vivo-derived porcine zygotes and transferred 86 of the microinjected embryos into three hormonally synchronized recipients. Fetuses and piglets were analyzed by flow cytometry for remaining Gal epitopes. DNA was sequenced to detect mutations at the GGTA1 locus.

RESULTS

Two of the recipients remained pregnant as determined by ultrasound scanning on day 25 of gestation. One pregnancy was terminated on day 26, and six healthy fetuses were recovered. The second pregnancy was allowed to go to term and resulted in the birth of six healthy piglets. Flow cytometry analysis revealed the absence of Gal epitopes in four of six fetuses (66%), indicating a biallelic KO of GGTA1. Additionally, three of the six live-born piglets (50%) did not express Gal epitopes on their cell surface. Two fetuses and two piglets showed a mosaicism with a mixed population of Gal-free and Gal-expressing cells. Only a single piglet did not have any genomic modifications. Genomic sequencing revealed indel formation at the GGTA1 locus ranging from +17 bp to -20 bp.

CONCLUSIONS

These results demonstrate the efficacy of CRISPR/Cas to generate genetic modifications in pigs by simplified technology, such as intracytoplasmic microinjection into zygotes, which would significantly facilitate the production of genetically modified pigs suitable for xenotransplantation. Importantly, this simplified injection protocol avoids the penetration of the vulnerable pronuclear membrane, and is thus compatible with higher survival rates of microinjected embryos, which in turn facilitates production of genetically modified piglets.