Genetically engineered pig models for diabetes research

An inducible model of chronic hyperglycemia

Transgene driven expression of Escherichia coli nitroreductase (NTR1.0) renders animal cells susceptible to the antibiotic metronidazole (MTZ). Many NTR1.0/MTZ ablation tools have been reported in zebrafish, which have significantly impacted regeneration studies. However, NTR1.0-based tools are not appropriate for modeling chronic cell loss as prolonged application of the required MTZ dose (10 mM) is deleterious to zebrafish health. We established that this dose corresponds to the median lethal dose (LD50) of MTZ in larval and adult zebrafish and that it induced intestinal pathology. NTR2.0 is a more active nitroreductase engineered from Vibrio vulnificus NfsB that requires substantially less MTZ to induce cell ablation. Here, we report on the generation of two new NTR2.0-based zebrafish lines in which acute β-cell ablation can be achieved without MTZ-associated intestinal pathology. For the first time, we were able to sustain β-cell loss and maintain elevated glucose levels (chronic hyperglycemia) in larvae and adults. Adult fish showed significant weight loss, consistent with the induction of a diabetic state, indicating that this paradigm will allow the modeling of diabetes and associated pathologies.

The Pig as a Translational Animal Model for Biobehavioral and Neurotrauma Research

In recent decades, the pig has attracted considerable attention as an important intermediary model animal in translational biobehavioral research due to major similarities between pig and human neuroanatomy, physiology, and behavior. As a result, there is growing interest in using pigs to model many human neurological conditions and injuries. Pigs are highly intelligent and are capable of performing a wide range of behaviors, which can provide valuable insight into the effects of various neurological disease states. One area in which the pig has emerged as a particularly relevant model species is in the realm of neurotrauma research. Indeed, the number of investigators developing injury models and assessing treatment options in pigs is ever-expanding. In this review, we examine the use of pigs for cognitive and behavioral research as well as some commonly used physiological assessment methods. We also discuss the current usage of pigs as a model for the study of traumatic brain injury. We conclude that the pig is a valuable animal species for studying cognition and the physiological effect of disease, and it has the potential to contribute to the development of new treatments and therapies for human neurological and psychiatric disorders.

Research Progress on the Construction and Application of a Diabetic Zebrafish Model

Diabetes is a metabolic disease characterized by high blood glucose levels. With economic development and lifestyle changes, the prevalence of diabetes is increasing yearly. Thus, it has become an increasingly serious public health problem in countries around the world. The etiology of diabetes is complex, and its pathogenic mechanisms are not completely clear. The use of diabetic animal models is helpful in the study of the pathogenesis of diabetes and the development of drugs. The emerging vertebrate model of zebrafish has many advantages, such as its small size, large number of eggs, short growth cycle, simple cultivation of adult fish, and effective improvement of experimental efficiency. Thus, this model is highly suitable for research as an animal model of diabetes. This review not only summarizes the advantages of zebrafish as a diabetes model, but also summarizes the construction methods and challenges of zebrafish models of type 1 diabetes, type 2 diabetes, and diabetes complications. This study provides valuable reference information for further study of the pathological mechanisms of diabetes and the research and development of new related therapeutic drugs.

Banking on a new understanding: translational opportunities from veterinary biobanks

Current advances in geroscience are due in part to the discovery of biomarkers with high predictive ability in short-lived laboratory animals such as flies and mice. These model species, however, do not always adequately reflect human physiology and disease, highlighting the need for a more comprehensive and relevant model of human aging. Domestic dogs offer a solution to this obstacle, as they share many aspects not only of the physiological and pathological trajectories of their human counterpart, but also of their environment. Furthermore, they age at a considerably faster rate. Studying aging in the companion dog provides an opportunity to better understand the biological and environmental determinants of healthy lifespan in our pets, and to translate those findings to human aging. Biobanking, the systematic collection, processing, storage, and distribution of biological material and associated data has contributed to basic, clinical, and translational research by streamlining the management of high-quality biospecimens for biomarker discovery and validation. In this review, we discuss how veterinary biobanks can support research on aging, particularly when integrated into large-scale longitudinal studies. As an example of this concept, we introduce the Dog Aging Project Biobank.

Somatic Cell Nuclear Transfer in Pigs

Somatic cell nuclear transfer (SCNT) has been successfully applied to clone animals of several species. Pigs are one of the main livestock species for food production and are also important for biomedical research due to their physiopathological similarities with humans. In the past 20 years, clones of several swine breeds have been produced for a variety of purposes, including biomedical and agricultural applications. In this chapter, we describe a protocol to produce cloned pigs by SCNT.

Challenges faced in developing an ideal chronic wound model

INTRODUCTION

Chronic wounds are a major drain on healthcare resources and can lead to substantial reductions in quality of life for those affected. Moreover, they often precede serious events such as limb amputations and premature death. In the long run, this burden is likely to escalate with an ageing population and lifestyle diseases such as obesity. Thus far, the identification of beneficial therapeutics against chronic wounds have been hindered by the lack of an ideal chronic wound animal model. Although animal models of delayed healing have been developed, none of these models fully recapitulate the complexity of the human chronic wound condition. Furthermore, most animals do not develop chronic wounds. Only the thoroughbred racehorse develops chronic ulcers.

AREAS COVERED

In this review, the different characteristics of chronic wounds that highlight its complexity are described. In addition, currently available models reflecting different aspects of chronic wound pathology and their relevance to human chronic wounds are discussed. This article concludes by listing relevant features representative of an ideal chronic wound model. Additionally, alternative approaches for the development of chronic wound models are discussed.

EXPERT OPINION

Delayed models of healing, including the streptozotocin diabetic model, skin flap model and magnet-induced IR models have emerged. While these models have been widely adopted for preclinical therapeutic testing, their relevance towards human chronic wounds remains debatable. In particular, current delayed healing models often fail to fully incorporate the key characteristics of chronic ulcers. Ultimately, more representative models are required to expedite the advancement of novel therapeutics to the clinic.

Streptozotocin-Induced Diabetes Causes Changes in Serotonin-Positive Neurons in the Small Intestine in Pig Model

Serotonin (5-hydroxytryptamine or 5-HT) is an important neurotransmitter of the central and peripheral nervous systems, predominantly secreted in the gastrointestinal tract, especially in the gut. 5-HT is a crucial enteric signaling molecule and is well known for playing a key role in sensory-motor and secretory functions in the gut. Gastroenteropathy is one of the most clinical problems in diabetic patients with frequent episodes of hyperglycemia. Changes in 5-HT expression may mediate gastrointestinal tract disturbances seen in diabetes, such as nausea and diarrhea. Based on the double immunohistochemical staining, this study determined the variability in the population of 5-HT-positive neurons in the porcine small intestinal enteric neurons in the course of streptozotocin-induced diabetes. The results show changes in the number of 5-HT-positive neurons in the examined intestinal sections. The greatest changes were observed in the jejunum, particularly within the myenteric plexus. In the ileum, both de novo 5-HT synthesis in the inner submucosal plexus neurons and an increase in the number of neurons in the outer submucosal plexus were noted. The changes observed in the duodenum were also increasing in nature. The results of the current study confirm the previous observations concerning the involvement of 5-HT in inflammatory processes, and an increase in the number of 5-HT -positive neurons may also be a result of increased concentration of the 5-HT in the gastrointestinal tract wall and affects the motor and secretory processes, which are particularly intense in the small intestines.

The Novel-miR-659/SPP1 Interaction Regulates Fat Deposition in Castrated Male Pigs

Simple Summary

Castration is a standard method for eliminating boar taint in industrial hog production, but it also causes enormous fat accumulation in the carcass. Secreted phosphoprotein 1 (SPP1) was selected to investigate its functions on the regulation of adipose deposition based on our previous data. In the present study, SPP1 overexpression and interference bidirectionally verified that SPP1 inhibited adipogenic differentiation of porcine bone marrow mesenchymal stem cells (pBMSCs). Testosterone-treated cell models were used to simulate the androgen status of intact pigs, and testosterone addition influenced SPP1 mRNA levels during the differentiation of pBMSCs. Moreover, we identified novel-miR-659 and targeted the 3′ untranslated region of SPP1 based on bioinformatics analysis and dual-luciferase assays, and found that the novel-miR-659 upregulation promoted adipogenesis while novel-miR-659 downregulation suppressed adipogenesis in pBMSCs detected by Oil Red O staining and adipogenic markers. Collectively, the interaction between novel-miR-659 and SPP1 can regulate adipose accumulation in castrated male pigs. Our data provide a theoretical basis for further study on the fat deposition mechanism caused by castration.

Abstract

Castration is usually used to remove boar taint in commercial pork production, but the adipose accumulation was increased excessively, which affected the meat quality of pigs. Based on our previous study, secreted phosphoprotein 1 (SPP1) was significantly differentially expressed between castrated and intact male pigs. However, the role of SPP1 in regulating adipose growth and fat storage caused by castration is unknown. In this study, SPP1 was identified to inhibit adipogenesis by the expression of adipogenic markers PPARγ and FABP4 as well as Oil red staining assay during differentiation of porcine bone marrow mesenchymal stem cells (pBMSCs). Subsequently, testosterone was used to treat pBMSCs to simulate the androgen status of intact pigs. Compared with the control groups without testosterone, the SPP1 expression in the testosterone group was markedly increased in the late stage of pBMSCs differentiation. Furthermore, novel-miR-659 was predicted by TargetScan and miRDB to target SPP1 and verified through a dual-luciferase reporter assay. Oil Red O staining assay indicated that novel-miR-659 overexpression significantly promoted adipogenesis, whereas novel-miR-659 inhibition suppressed adipogenesis. The expressions of adipogenic markers PPARγ and FABP4 showed the same tendency. Taken together, our study found that the targeted interaction between novel-miR-659 and SPP1 is involved in regulation of fat deposition in castrated male pigs.

Comparatively analyzing the liver-specific transcriptomic profiles in Kunming mice afflicted with streptozotocin- and natural food-induced type 2 diabetes mellitus

BACKGROUND

Streptozotocin is a classic drug used to induce diabetes in animal models.

OBJECTIVE

The aim of this study is to investigate the liver transcriptome of Kunming mice with diabetes induced by either streptozotocin (STZ) or Non-STZ.

METHODS

Forty male mice were randomly assigned into four groups: Control (Ctr, standard diet), mHH (high fat and high carbohydrate diet), mHS (high fat and high carbohydrate diet for 4 weeks followed by 60 mg/kg STZ for 3 consecutive days) and mSH (60 mg/kg STZ for 3 consecutive days followed by a high fat and high carbohydrate diet for 12 weeks). All mice injected with STZ were identified as diabetic despite the sequential feeding of high fat and high carbohydrate diets.

RESULTS

Only 7 of 13 mice in the mHH group met the diagnostic criteria for diabetes. The asting blood glucose (FBG) of the mHH, mHS, mSH and Ctrl groups was 13.27 ± 1.14, 15.01 ± 2.59, 15.95 ± 4.38 and 6.28 ± 0.33 mmol/L at the 12th week, respectively. Compared with the mHH group, transcription was elevated in 85 genes in the livers of mHS mice, while 21 genes were downregulated and 97 genes were upregulated in the mSH group while 35 genes were decreased. A total of 43 co-expressed genes were identified in the mHS vs mHH and mSH vs mHH groups. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses showed that two corporate GO terms and two KEGG pathways were significantly annotated in the STZ-treated groups. Both the GO term and pathway were related to the metabolism mediated by p53.

CONCLUSION

A high fat and high carbohydrate diet combined with a low dose of STZ can effectively induce diabetes in Kunming mice despite the abnormal expressions of genes in the liver. The differentially expressed genes were related to metabolism mediated by p53.

Importance of the pig as a human biomedical model

[Figure: see text].

Multimodal characterization of Yucatan minipig behavior and physiology through maturation

Brain injuries induced by external forces are particularly challenging to model experimentally. In recent decades, the domestic pig has been gaining popularity as a highly relevant animal model to address the pathophysiological mechanisms and the biomechanics associated with head injuries. Understanding cognitive, motor, and sensory aspects of pig behavior throughout development is crucial for evaluating cognitive and motor deficits after injury. We have developed a comprehensive battery of tests to characterize the behavior and physiological function of the Yucatan minipig throughout maturation. Behavioral testing included assessments of learning and memory, executive functions, circadian rhythms, gait analysis, and level of motor activity. We applied traditional behavioral apparatus and analysis methods, as well as state-of-the-art sensor technologies to report on motion and activity, and artificial intelligent approaches to analyze behavior. We studied pigs from 16 weeks old through sexual maturity at 35 weeks old. The results show multidimensional characterization of minipig behavior, and how it develops and changes with age. This animal model may capitulate the biomechanical consideration and phenotype of head injuries in the developing brain and can drive forward the field of understanding pathophysiological mechanisms and developing new therapies to accelerate recovery in children who have suffered head trauma.

Epigenetic clock and DNA methylation analysis of porcine models of aging and obesity

DNA-methylation profiles have been used successfully to develop highly accurate biomarkers of age, epigenetic clocks, for many species. Using a custom methylation array, we generated DNA methylation data from n = 238 porcine tissues including blood, bladder, frontal cortex, kidney, liver, and lung, from domestic pigs (Sus scrofa domesticus) and minipigs (Wisconsin Miniature Swine™). Samples used in this study originated from Large White X Landrace crossbred pigs, Large White X Minnesota minipig crossbred pigs, and Wisconsin Miniature Swine™. We present 4 epigenetic clocks for pigs that are distinguished by their compatibility with tissue type (pan-tissue and blood clock) and species (pig and human). Two dual-species human-pig pan-tissue clocks accurately measure chronological age and relative age, respectively. We also characterized CpGs that differ between minipigs and domestic pigs. Strikingly, several genes implicated by our epigenetic studies of minipig status overlap with genes (ADCY3, TFAP2B, SKOR1, and GPR61) implicated by genetic studies of body mass index in humans. In addition, CpGs with different levels of methylation between the two pig breeds were identified proximal to genes involved in blood LDL levels and cholesterol synthesis, of particular interest given the minipig's increased susceptibility to cardiovascular disease compared to domestic pigs. Thus, breed-specific differences of domestic and minipigs may potentially help to identify biological mechanisms underlying weight gain and aging-associated diseases. Our porcine clocks are expected to be useful for elucidating the role of epigenetics in aging and obesity, and the testing of anti-aging interventions.

Sequential in vivo labeling of insulin secretory granule pools in INS-SNAP transgenic pigs

β cells produce, store, and secrete insulin upon elevated blood glucose levels. Insulin secretion is a highly regulated process. The probability for insulin secretory granules to undergo fusion with the plasma membrane or being degraded is correlated with their age. However, the molecular features and stimuli connected to this behavior have not yet been fully understood. Furthermore, our understanding of β cell function is mostly derived from studies of ex vivo isolated islets in rodent models. To overcome this translational gap and study insulin secretory granule turnover in vivo, we have generated a transgenic pig model with the SNAP-tag fused to insulin. We demonstrate the correct targeting and processing of the tagged insulin and normal glycemic control of the pig model. Furthermore, we show specific single- and dual-color granular labeling of in vivo-labeled pig pancreas. This model may provide unprecedented insights into the in vivo insulin secretory granule behavior in an animal close to humans.

Supplementation with asiatic acid during in vitro maturation improves porcine oocyte developmental competence by regulating oxidative stress

Asiatic acid is a natural triterpene found in Centella asiatica that acts as an effective free radical scavenger. Our previous research showed that asiatic acid delayed porcine oocyte ageing in vitro and improved preimplantation embryo development competence in vitro; however, the protective effects of asiatic acid against oxidative stress in porcine oocyte maturation are still unclear. Here, we investigated the effects of asiatic acid on porcine oocyte in vitro maturation (IVM) and subsequent embryonic development competence after parthenogenetic activation (PA) and in vitro fertilization (IVF). The results of the present research showed that 10 μM asiatic acid supplementation did not affect the expansion of cumulus cells or polar body extrusion of porcine oocytes, while asiatic acid application significantly increased the subsequent blastocyst formation rate and quality of porcine PA and IVF embryos. Hydrogen peroxide (H₂O₂) is a reactive oxygen species (ROS) that induces oxidative stress in porcine oocytes. As expected, asiatic acid supplementation not only decreased intracellular ROS levels but also attenuated H₂O₂-induced intracellular ROS generation. Further analysis revealed that asiatic acid supplementation enhanced intracellular glutathione production, mitochondrial membrane potential, and ATP generation at the end of IVM. In summary, our results reveal that asiatic acid supplementation exerts beneficial effects on porcine oocytes by regulating oxidative stress during the IVM process and could act as a potential antioxidant in porcine oocytes matured in vitro production systems.

A New Toolbox in Experimental Embryology-Alternative Model Organisms for Studying Preimplantation Development

Preimplantation development is well conserved across mammalian species, but major differences in developmental kinetics, regulation of early lineage differentiation and implantation require studies in different model organisms, especially to better understand human development. Large domestic species, such as cattle and pig, resemble human development in many different aspects, i.e., the timing of zygotic genome activation, mechanisms of early lineage differentiations and the period until blastocyst formation. In this article, we give an overview of different assisted reproductive technologies, which are well established in cattle and pig and make them easily accessible to study early embryonic development. We outline the available technologies to create genetically modified models and to modulate lineage differentiation as well as recent methodological developments in genome sequencing and imaging, which form an immense toolbox for research. Finally, we compare the most recent findings in regulation of the first lineage differentiations across species and show how alternative models enhance our understanding of preimplantation development.

Cas9-expressing chickens and pigs as resources for genome editing in livestock

Genetically modified animals continue to provide important insights into the molecular basis of health and disease. Research has focused mostly on genetically modified mice, although other species like pigs resemble the human physiology more closely. In addition, cross-species comparisons with phylogenetically distant species such as chickens provide powerful insights into fundamental biological and biomedical processes. One of the most versatile genetic methods applicable across species is CRISPR-Cas9. Here, we report the generation of transgenic chickens and pigs that constitutively express Cas9 in all organs. These animals are healthy and fertile. Functionality of Cas9 was confirmed in both species for a number of different target genes, for a variety of cell types and in vivo by targeted gene disruption in lymphocytes and the developing brain, and by precise excision of a 12.7-kb DNA fragment in the heart. The Cas9 transgenic animals will provide a powerful resource for in vivo genome editing for both agricultural and translational biomedical research, and will facilitate reverse genetics as well as cross-species comparisons.

A decade of experience with genetically tailored pig models for diabetes and metabolic research

The global prevalence of diabetes mellitus and other metabolic diseases is rapidly increasing. Animal models play pivotal roles in unravelling disease mechanisms and developing and testing therapeutic strategies. Rodents are the most widely used animal models but may have limitations in their resemblance to human disease mechanisms and phenotypes. Findings in rodent models are consequently often difficult to extrapolate to human clinical trials. To overcome this ‘translational gap’, we and other groups are developing porcine disease models. Pigs share many anatomical and physiological traits with humans and thus hold great promise as translational animal models. Importantly, the toolbox for genetic engineering of pigs is rapidly expanding. Human disease mechanisms and targets can therefore be reproduced in pigs on a molecular level, resulting in precise and predictive porcine (PPP) models. In this short review, we summarize our work on the development of genetically (pre)diabetic pig models and how they have been used to study disease mechanisms and test therapeutic strategies. This includes the generation of reporter pigs for studying beta-cell maturation and physiology. Furthermore, genetically engineered pigs are promising donors of pancreatic islets for xenotransplantation. In summary, genetically tailored pig models have become an important link in the chain of translational diabetes and metabolic research.

Technical and Anatomical Considerations for Reproducible Inactivation of Large Animal Carcasses by Steam Sterilization

Introduction:

The complete inactivation of infectious tissues of large animal carcasses is one of the most challenging tasks in high-containment facilities. Steam sterilization is a method frequently in use to achieve biological inactivation of liquid and solid waste.

Objective:

This study aims to highlight parameters most effective in creating reproducible cycles for steam sterilization of pig and calf carcasses.

Methods:

Two pigs or 1 calf were sterilized by running a liquid cycle (n = 3) at 121°C for at least 120 minutes in a pass-through autoclave. To assess the physical and biological parameters, temperature data loggers and biological indicators (BIs) with spores of Geobacillus stearothermophilus (ATCC 7953) were placed at defined positions within animal carcasses. After completion of each cycle, data loggers were analyzed and BIs were incubated for 7 days at 60°C.

Results:

Initial testing with an undissected pig carcass resulted in suboptimal temperatures at the tissue level with growth on 1 BI. After modifications of the used stainless-steel boxes and by placing the reference probe of the autoclave in the animal carcass, reproducible cycles could be created. A complete inactivation of BIs and a temperature profile of >121°C for at least 20 minutes could be achieved in almost all probed tissues.

Conclusion:

Only minor modifications in carcass preparation and the used sterilization equipment resulted in effective and reproducible cycles to inactivate large animal carcasses by using a steam autoclave.

Effect of Streptozotocin-Inducted Diabetes on the Pathophysiology of Enteric Neurons in the Small Intestine Based on the Porcine Diabetes Model

Hyperglycemia is one of the main causes of diabetes complications. Gastrointestinal (GI) disturbances are one of the most frequent complications during diabetes. The porcine digestive tract possesses physiological and pathological similarities to the human digestive tract. This also applies to the innervation of the gastrointestinal tract. In this study, the influence of experimentally-inducted hyperglycemia was examined on the expression of vesicular acetylcholine transporter (VAChT), cocaine- and amphetamine-regulated transcript (CART), galanin (GAL), vasoactive intestinal polypeptide (VIP), and calcitonin gene-related peptide (CGRP) in the enteric nervous system (ENS) neurons in the small intestine of the pig. During the current study, an increased number of neurons containing CART, VIP, GAL, and CGRP under streptozotocin injection were observed. The augmentation of expression included all enteric plexuses present in the small intestine. The same results were obtained in the case of VAChT; namely, chronic hyperglycemia led to an increase in the number of neurons utilizing VAChT in all investigated plexuses. The obtained results suggested that the function of neuropeptides studied in this experiment depended on their localization in the ENS structures, as well as part of the GI tract. Diabetes led to alterations in the neurochemical phenotype of small intestine enteric neurons.

Generation of viable PDX1 gene-edited founder pigs as providers of nonmosaics

Pancreatic duodenal homeobox 1 (PDX1) is a crucial gene for pancreas development during the fetal period. PDX1-modified pigs have the potential to be used as a model of diabetes mellitus. However, the severe health problems caused by the PDX1 mutation limit phenotypic studies of PDX1-modified pigs as diabetes models. In this study, we generated PDX1-modified pigs by the CRISPR/Cas9 system introduced into zygotes via electroporation and investigated the mosaicism, phenotypes, and inheritance of the resulting pigs. After the embryo transfer of PDX1-modified zygotes, nine mutant piglets were delivered. Two piglets were apancreatic biallelic mutants. For the other seven piglets, the ratio of mutant alleles to total alleles was 17.5-79.7%. Two mutant piglets with high mutation rates (67.7% and 79.7%) exhibited hypoplasia of the pancreas, whereas the other five piglets were healthy. One of the male mutant piglets was further analyzed. The ejaculated semen from the pig contained PDX1-mutant spermatozoa and the pig showed normal reproductive ability. In conclusion, the frequency of the PDX1 mutation is presumed to relate to pancreas formation, and PDX1 mutant founder pigs generated from zygotes introduced to the CRISPR/Cas9 system can serve as providers of nonmosaics to contribute to medical research on diabetes mellitus.

Validation of mouse phosphoprotein enriched in astrocyte 15 (mPEA15) expressing transgenic pig as a potential model in diabetes translational research

The present study aimed to investigate the characteristics of mPEA15 expressing transgenic pig (TG pig) as a potential model for diabetes. Expression analysis confirmed the ubiquitous expression of mPEA15 in TG pigs at F4. Oral glucose tolerance test results showed that restoration of normal glucose levels was significantly delayed in the TG pigs when compared with that in the wild-type pigs (WT pigs). Primary skeletal muscle cells isolated from TG pigs demonstrated reduced glucose uptake and reduced GLUT4 translocation to the plasma membrane in response to insulin treatment. Combined, these results suggest that mPEA15 expressing pigs has a glucose intolerance and insulin resistance which are known to mediate the pathophysiology of type 2 diabetes mellitus. Thus, mPEA15 transgenic pigs would serve as a promising model for diabetes translational research.

Animal models of arrhythmia: classic electrophysiology to genetically modified large animals

Arrhythmias are common and contribute substantially to cardiovascular morbidity and mortality. The underlying pathophysiology of arrhythmias is complex and remains incompletely understood, which explains why mostly only symptomatic therapy is available. The evaluation of the complex interplay between various cell types in the heart, including cardiomyocytes from the conduction system and the working myocardium, fibroblasts and cardiac immune cells, remains a major challenge in arrhythmia research because it can be investigated only in vivo. Various animal species have been used, and several disease models have been developed to study arrhythmias. Although every species is useful and might be ideal to study a specific hypothesis, we suggest a practical trio of animal models for future use: mice for genetic investigations, mechanistic evaluations or early studies to identify potential drug targets; rabbits for studies on ion channel function, repolarization or re-entrant arrhythmias; and pigs for preclinical translational studies to validate previous findings. In this Review, we provide a comprehensive overview of different models and currently used species for arrhythmia research, discuss their advantages and disadvantages and provide guidance for researchers who are considering performing in vivo studies.

Porcine models for studying complications and organ crosstalk in diabetes mellitus

The worldwide prevalence of diabetes mellitus and obesity is rapidly increasing not only in adults but also in children and adolescents. Diabetes is associated with macrovascular complications increasing the risk for cardiovascular disease and stroke, as well as microvascular complications leading to diabetic nephropathy, retinopathy and neuropathy. Animal models are essential for studying disease mechanisms and for developing and testing diagnostic procedures and therapeutic strategies. Rodent models are most widely used but have limitations in translational research. Porcine models have the potential to bridge the gap between basic studies and clinical trials in human patients. This article provides an overview of concepts for the development of porcine models for diabetes and obesity research, with a focus on genetically engineered models. Diabetes-associated ocular, cardiovascular and renal alterations observed in diabetic pig models are summarized and their similarities with complications in diabetic patients are discussed. Systematic multi-organ biobanking of porcine models of diabetes and obesity and molecular profiling of representative tissue samples on different levels, e.g., on the transcriptome, proteome, or metabolome level, is proposed as a strategy for discovering tissue-specific pathomechanisms and their molecular key drivers using systems biology tools. This is exemplified by a recent study providing multi-omics insights into functional changes of the liver in a transgenic pig model for insulin-deficient diabetes mellitus. Collectively, these approaches will provide a better understanding of organ crosstalk in diabetes mellitus and eventually reveal new molecular targets for the prevention, early diagnosis and treatment of diabetes mellitus and its associated complications.

Large Animal Models of Diabetes

Safe and reliable large animal diabetes models are a key prerequisite for advanced preclinical studies on diabetes. Chemical induction is the standard model of diabetes in rodents but is often critiqued in higher animals due to reduced efficacy, relevant side effects, and inadequate mortality rate. In this chapter, we aim to describe both pharmacological and surgical approaches for reproducible and safe diabetes models in minipigs and primates. In addition, genetically modified pig models for diabetes research are described.

Placental structure in gestational diabetes mellitus

The placenta is a transitory organ, located between the mother and the foetus, which supports intrauterine life. This organ has nutritional, endocrine and immunologic functions to support foetal development. Several factors are related to the correct functioning of the placenta including foetal and maternal blood flow, appropriate nutrients, expression and function of receptors and transporters, and the morphology of the placenta itself. Placental morphology is crucial for understanding the pathophysiology of the organ as represents the physical structure where nutrient exchange occurs. In pathologies of pregnancy such as diabetes mellitus in humans and animal models, several changes in the placental morphology occur, related mainly with placental size, hypervascularization, higher branching capillaries of the villi and increased glycogen deposits among others. Gestational diabetes mellitus is associated with modifications in the structure of the human placenta including changes in the surface area and volume, as well as histological changes including an increased volume of intervillous space and terminal villi, syncytiotrophoblast number, fibrinoid areas, and glycogen deposits. These modifications may result in functional changes in this organ thus limiting the wellbeing of the developing foetus. This review gives an overview of recurrent morphological changes at macroscopic and histological levels seen in the placenta from gestational diabetes in humans and animal models. This article is part of a Special Issue entitled: Membrane Transporters and Receptors in Pregnancy Metabolic Complications edited by Luis Sobrevia.

Overexpression of MBD3 Improves Reprogramming of Cloned Pig Embryos

Methyl-CpG-binding domain protein 3 (MBD3) is a core component of the nucleosome remodeling and deacetylase (NuRD) complex, which is crucial for pluripotent stem cell differentiation and embryonic development. MBD3 was shown to play important roles in transcription factor-induced somatic cell reprogramming. Expression level of MBD3 was demonstrated to be higher in somatic cell nuclear transfer-generated cloned pig embryos than in fertilization-derived porcine embryos. However, the functions of MBD3 in nuclear transfer-mediated somatic cell reprogramming are unknown. In this study, MBD3 was overexpressed in cloned pig embryos, and the effects of MBD3 overexpression on gene transcription, DNA methylation, and in vitro developmental competence of cloned pig embryos were analyzed. Results indicated that overexpression of MBD3 in cloned pig embryos not only increased blastocyst rate and number of cells per blastocyst but also upregulated mRNA expression levels and decreased the DNA methylation of NANOG, OCT4, and LINE1 genes to the levels close to those in in vivo fertilization-produced pig embryos. These findings suggest that overexpression of MBD3 improves reprogramming of cloned pig embryos.

Modelling the endocrine pancreas in health and disease

Diabetes mellitus is a multifactorial disease affecting increasing numbers of patients worldwide. Progression to insulin-dependent diabetes mellitus is characterized by the loss or dysfunction of pancreatic β-cells, but the pathomechanisms underlying β-cell failure in type 1 diabetes mellitus and type 2 diabetes mellitus are still poorly defined. Regeneration of β-cell mass from residual islet cells or replacement by β-like cells derived from stem cells holds great promise to stop or reverse disease progression. However, the development of new treatment options is hampered by our limited understanding of human pancreas organogenesis due to the restricted access to primary tissues. Therefore, the challenge is to translate results obtained from preclinical model systems to humans, which requires comparative modelling of β-cell biology in health and disease. Here, we discuss diverse modelling systems across different species that provide spatial and temporal resolution of cellular and molecular mechanisms to understand the evolutionary conserved genotype-phenotype relationship and translate them to humans. In addition, we summarize the latest knowledge on organoids, stem cell differentiation platforms, primary micro-islets and pseudo-islets, bioengineering and microfluidic systems for studying human pancreas development and homeostasis ex vivo. These new modelling systems and platforms have opened novel avenues for exploring the developmental trajectory, physiology, biology and pathology of the human pancreas.

Thymosin β4-mediated protective effects in the heart

INTRODUCTION

Despite recent advances in the treatment of coronary heart disease, a significant number of patients progressively develop heart failure. Reduction of infarct size after acute myocardial infarction and normalization of microvasculature in chronic myocardial ischemia could enhance cardiac survival.

AREAS COVERED

Induction of neovascularization using vascular growth factors has emerged as a promising novel approach for cardiac regeneration. Thymosin β4 (Tβ4) might be a promising candidate for the treatment of ischemic heart disease. It has been characterized as a major G-actin-sequestering factor regulating cell motility, migration, and differentiation. During cardiac development, Thymosin β4 seems essential for vascularization of the myocardium. In the adult organism, Thymosin β4 has anti-inflammatory properties, increases myocyte and endothelial cell survival accompanied by differentiation of epicardial progenitor cells. In chronic myocardial ischemia, Tβ4 overexpression enhances micro- and macrovasculature in the ischemic area and thereby improves myocardial function. A comparable effect is seen in diabetic and dyslipidemic pig ischemic hearts, suggesting an attractive therapeutic potential of adeno-associated virus encoding for Tβ4 for patients with ischemic heart disease.

EXPERT OPINION

Induction of mature micro-vessels is a prerequisite for chronic myocardial ischemia and might be achieved via a long-term overexpression of Thymosin β4.

Potential use of transgenic domestic pigs expressing recombinant human erythropoietin in diabetes translation research

Recently, diabetes mellitus (DM) has shown rapid global increases with about five million deaths annually. Animal models are imperative to understand disease mechanisms and develop diagnostic, preventive, and therapeutic interventions in translational research. Rodent and mini-pig models have been established and widely used for DM research. However, domestic pig models are limited in spite of advantages such as pharmacokinetic and physiopathological availability. This study examines the potential use of domestic pigs expressing recombinant human erythropoietin (rhEPO) as disease and therapeutic response models for DM. We previously generated transgenic pigs (n = 16, EPO Tg) in which rhEPO was expressed and circulated in all organs. Thirty-two pigs, including 16 controls, were fed high fat (HF) diets for 42 weeks. Subsequently, blood samples for chemical and metabolic analysis were collected after fasting for 24 h and glucose loading for oral glucose tolerance tests (OGTTs). We found increased activation of the PI3 K/Akt signaling pathway under hypoxic conditions after rhEPO treatment, and HF diet-inducible-obesity in the EPO Tg and control pigs. OGTTs showed lower fasting glucose levels in the EPO Tg pigs than in controls before and after the HF diet, suggesting that rhEPO may affect glucose concentrations. Insulin and C-peptide concentrations responded slowly to glucose administration and returned to initial levels after 2 h. The blood test results suggest that EPO might affect metabolic and chemical components such as glucose, high-density lipoprotein, glucagon, triglyceride, and free fatty acid. Our findings support the use of rhEPO transgenic domestic pigs as model animals for translational DM research.

Generation of insulin-deficient piglets by disrupting INS gene using CRISPR/Cas9 system

Diabetes mellitus is a chronic disease with accompanying severe complications. Various animal models, mostly rodents due to availability of genetically modified lines, have been used to investigate the pathophysiology of diabetes. Using pigs for diabetic research can be beneficial because of their similarity in size, pathogenesis pathway, physiology, and metabolism with human. However, the use of pigs for diabetes research has been hampered due to only few pig models presenting diabetes symptoms. In this study, we have successfully generated insulin-deficient pigs by generating the indels of the porcine INS gene in somatic cells using CRISPR/Cas9 system followed by somatic cell nuclear transfer. First, somatic cells carrying a modified INS gene were generated using CRISPR/Cas9 system and their genotypes were confirmed by T7E1 assay; targeting efficiency was 40.4% (21/52). After embryo transfer, three live and five stillborn piglets were born. As expected, INS knockout piglets presented high blood glucose levels and glucose was detected in the urine. The level of insulin and c-peptide in the blood serum of INS knockout piglets were constant after feeding and the expression of insulin in the pancreas was absent in those piglets. This study demonstrates effectiveness of CRISPR/Cas9 system in generating novel pig models. We expect that these insulin-deficient pigs can be used in diabetes research to test the efficacy and safety of new drugs and the recipient of islet transplantation to investigate optimal transplantation strategies.

Loss-of-function myostatin mutation increases insulin sensitivity and browning of white fat in Meishan pigs

Myostatin-deficient mice showed a remarkable hypertrophy of skeletal muscle, with a decreased fat mass and enhanced insulin sensitivity. Currently, it is unclear if the inhibition of myostatin could be used as an approach to treat human obesity and insulin resistance. In this study, we investigated if the inhibition of porcine myostatin has any effect on fat deposition and insulin sensitivity using genetically engineered Meishan pigs containing a myostatin loss-of-function mutation (Mstn^−/− ). Our results indicated that, when compared with wild-type pigs, the amount of subcutaneous fat and leaf fat of Mstn^−/− pigs were significantly decreased mainly due to the browning of subcutaneous adipose tissue. Additionally, the serum insulin level decreased and the insulin sensitivity increased significantly in Mstn^−/− pigs. Moreover, we found a significant increase in levels of insulin receptor and insulin receptor substrate proteins in skeletal muscle of Mstn^−/− pigs, which then activating the insulin signaling pathway. Irisin-mediated regulation is not the only pathway for the activation of insulin signal in Mstn^−/− skeletal muscle. This study provides valuable insight for the treatment of human obesity and diabetes mellitus.

Doxazosin attenuates renal matrix remodeling mediated by anti-α1-adrenergic receptor antibody in a rat model of diabetes mellitus

Diabetic nephropathy is a major complication of diabetes mellitus (DM). Recent studies suggest that immunological mechanisms have a key role in the pathogenesis of DM, therefore these mechanisms may be important targets for diabetes therapy. The present study evaluated the effects of anti-α₁-adrenergic receptor antibody (α₁-R Ab) mediation and doxazosin treatment in a rat model of DM. It was observed that levels of 24-h urinary protein, serum creatinine and transforming growth factor-β₁ in DM were significantly increased after α₁-R Ab mediation (all P<0.05). In addition, electron microscopy identified severe damage in the renal tissue microstructures of DM rats following α₁-R Ab mediation, while only mild abnormalities were observed in that of healthy rats mediated with α₁-R Ab and of untreated DM rats. No marked abnormalities were observed in the renal tissue of healthy blank controls. Furthermore, in DM rats treated with α₁-R Ab mediation + doxazosin intervention, the expression of TGF-β₁ significantly decreased, and renal functions and renal matrix remodeling were significantly improved, relative to untreated DM controls (P<0.01). These results suggest that α₁-R Ab may be involved in renal matrix remodeling during DM, and that kidney protection during DM may be achieved through treatment with corresponding receptor antagonists.

Retinopathy with central oedema in an INS C94Y transgenic pig model of long-term diabetes

AIMS/HYPOTHESIS

Diabetic retinopathy is a severe complication of diabetes mellitus that often leads to blindness. Because the pathophysiology of diabetic retinopathy is not fully understood and novel therapeutic interventions require testing, there is a need for reliable animal models that mimic all the complications of diabetic retinopathy. Pig eyes share important anatomical and physiological similarities with human eyes. Previous studies have demonstrated that INS ^C94Y transgenic pigs develop a stable diabetic phenotype and ocular alterations such as cataracts. The aim of this study was to conduct an in-depth analysis of pathological changes in retinas from INS ^C94Y pigs exposed to hyperglycaemia for more than 2 years, representing a chronic diabetic condition.

METHODS

Eyes from six INS ^C94Ypigs and six age-matched control littermates were analysed via histology and immunohistochemistry. For histological analyses of retinal (layer) thickness, sections were stained with H&E or Mallory's trichrome. For comparison of protein expression patterns and vessel courses, sections were stained with different antibodies in immunohistochemistry. Observed lesions were compared with reported pathologies in human diabetic retinopathy.

RESULTS

INS ^C94Ypigs developed several signs of diabetic retinopathy similar to those seen in humans, such as intraretinal microvascular abnormalities, symptoms of proliferative diabetic retinopathy and central retinal oedema in a region that is cone rich, like the human macula.

CONCLUSIONS/INTERPRETATION

The INS ^C94Ypig is an interesting model for studying the pathophysiology of diabetic retinopathy and for testing novel therapeutic strategies.

Identification and characterization of long non-coding RNAs in subcutaneous adipose tissue from castrated and intact full-sib pair Huainan male pigs

Background

Long non-coding RNAs (lncRNAs) regulate adipose tissue metabolism, however, their function on testosterone deficiency related obesity in humans is less understood. For this research, intact and castrated male pigs are the best model animal because of their similar proportional organ sizes, cardiovascular systems and metabolic features.

Results

We identified lncRNAs in subcutaneous adipose tissue by deep RNA-sequencing using the intact and castrated Huainan male pigs. The results showed that castration reduced serum testosterone but increased body fatness-related traits (serum triglyceride levels, backfat thickness, intramuscular fat content, and adipocyte size). Meanwhile, 343 lncRNAs from subcutaneous adipose tissue were identified, including 223 intergenic lncRNAs (lincRNAs), 68 anti-sense lncRNAs, and 52 intronic lncRNAs. It was predicted that there were 416 recognition sites for C/EBPα in the 303 lncRNA promoter region, and 13 adipogenesis-promoting miRNAs and five adipogenesis-depressing miRNAs target these lncRNAs. Eighteen lncRNAs, including nine up- and nine down-regulated had more than 2-fold differential expression between the castrated and intact male pigs (q-value < 0.05). Functional analysis indicated that these 18 lncRNAs and their target genes were involved in fatty acid, insulin, and the adipocytokine signaling pathway. We further analyzed the features of a conserved mouse lncRNA gene ENSMUST00000189966 and found it mainly expressed in the cell nucleus and target the Nuclear Receptor Subfamily 2 Group F Member 2 (NR2F2) gene. In 3 T3-L1 cells, differentiation down-regulated their expression, but dihydrotestosterone (DHT) significantly up-regulated their expression in a concentration-dependent manner (P < 0.05).

Conclusions

These results suggested that lncRNAs and their target genes might participated in the castration-induced fat deposition and provide a new therapeutic target for combatting testosterone deficiency-related obesity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3907-z) contains supplementary material, which is available to authorized users.

A high sucrose and high fat diet induced the development of insulin resistance in the skeletal muscle of Bama miniature pigs through the Akt/GLUT4 pathway

A high sucrose and high fat (HSHF) diet induces insulin resistance (IR) and increased susceptibility to type 2 diabetes mellitus (T2DM), but the underlying mechanisms are poorly characterized. This study aimed to investigate the molecular mechanisms by which the HSHF diet impairs insulin sensitivity in Bama miniature pigs (sus scrofa domesticus). Twelve Bama miniature pigs were randomly assigned to the control diet (CD) group (n=6) or the HSHF group (n=6) for 6 months. Biochemical parameters were measured. Western blot, RT-qPCR and immunohistochemistry were used to profile the changes of protein expression, mRNA expression and glucose transporter 4 (GLUT4) expression in skeletal muscle tissues, respectively. In comparison to the CD group, the homeostasis model assessment-insulin resistance (HOMA-IR) index of the HSHF group demonstrated a 2.9-fold increase, and the insulin sensitivity showed a 24.8% decrease. Compared with the CD group, p-Akt S473 decreased by approximately 59% and GLUT4 decreased by 43.8% in the skeletal muscle of the HSHF group. However, the expression of p-mTOR S2448 between the 2 groups was not significantly different (P=0.309). This study demonstrates that a 6-month HSHF diet caused IR, decreased insulin sensitivity, and reduced the expression of p-Akt S473 and GLUT4 in the skeletal muscle of Bama miniature pigs.

Annotation of the Domestic Pig Genome by Quantitative Proteogenomics

The pig is one of the earliest domesticated animals in the history of human civilization and represents one of the most important livestock animals. The recent sequencing of the Sus scrofa genome was a major step toward the comprehensive understanding of porcine biology, evolution, and its utility as a promising large animal model for biomedical and xenotransplantation research. However, the functional and structural annotation of the Sus scrofa genome is far from complete. Here, we present mass spectrometry-based quantitative proteomics data of nine juvenile organs and six embryonic stages between 18 and 39 days after gestation. We found that the data provide evidence for and improve the annotation of 8176 protein-coding genes including 588 novel and 321 refined gene models. The analysis of tissue-specific proteins and the temporal expression profiles of embryonic proteins provides an initial functional characterization of expressed protein interaction networks and modules including as yet uncharacterized proteins. Comparative transcript and protein expression analysis to human organs reveal a moderate conservation of protein translation across species. We anticipate that this resource will facilitate basic and applied research on Sus scrofa as well as its porcine relatives.

Simple and reproducible approaches for the collection of select porcine ganglia

BACKGROUND

The anatomy and physiology of the pig nervous system is more similar to humans compared to traditional rodent models. This makes the pig an attractive model to answer questions relating to human health and disease. Yet the technical and molecular tools available to pig researchers are limited compared to rodent researchers.

NEW METHOD

We developed simple and rapid methods to isolate the trigeminal, nodose (distal vagal), and dorsal root ganglia from neonatal pigs. We selected these ganglia due to their broad applicability to basic science researchers and clinicians.

RESULTS

Use of these methods resulted in reproducible isolation of all three types of ganglia as validated by histological examination.

COMPARISON WITH EXISTING METHOD(S)

There are currently no methods that describe a step-by-step protocol to isolate these porcine ganglia.

CONCLUSIONS

In conclusion, these methods for ganglia collection will facilitate and accelerate future neuroscience investigations in pig models of human disease.

Effect of Cell Cycle Interactions and Inhibition of Histone Deacetylases on Development of Porcine Embryos Produced by Nuclear Transfer

The aim of this study was to evaluate if the positive effects of inhibiting histone deacetylase enzymes on cell reprogramming and development of somatic cell nuclear transfer (SCNT) embryos is affected by the cell cycle stage of nuclear donor cells and host oocytes at the time of embryo reconstruction. SCNT embryos were produced with metaphase II (MII) or telophase II (TII) cytoplasts and nuclear donor cells that were either at the G1-0 or G2/M stages. Embryos reconstructed with the different cell cycle combinations were treated or not with the histone deacetylase inhibitor (HDACi) Scriptaid for 15 h and then cultured in vitro for 7 days. Embryos reconstructed with MII-G1-0 and TII-G2/M developed to the blastocyst stage with a higher frequency compared to the other groups, confirming the importance of cell cycle interactions on cell reprogramming and SCNT embryo development. Treatment with HDACi improved development of SCNT embryos produced with MII but not TII cytoplasts, independently of the cell cycle stage of nuclear donor cells. These findings provide evidence that the positive effect of HDACi treatment on development of SCNT embryos depends upon cell cycle interactions between the host cytoplast and the nuclear donor cells.

Clinical potential of human-induced pluripotent stem cells : Perspectives of induced pluripotent stem cells

The recent establishment of induced pluripotent stem (iPS) cells promises the development of autologous cell therapies for degenerative diseases, without the ethical concerns associated with human embryonic stem (ES) cells. Initially, iPS cells were generated by retroviral transduction of somatic cells with core reprogramming genes. To avoid potential genotoxic effects associated with retroviral transfection, more recently, alternative non-viral gene transfer approaches were developed. Before a potential clinical application of iPS cell-derived therapies can be planned, it must be ensured that the reprogramming to pluripotency is not associated with genome mutagenesis or epigenetic aberrations. This may include direct effects of the reprogramming method or "off-target" effects associated with the reprogramming or the culture conditions. Thus, a rigorous safety testing of iPS or iPS-derived cells is imperative, including long-term studies in model animals. This will include not only rodents but also larger mammalian model species to allow for assessing long-term stability of the transplanted cells, functional integration into the host tissue, and freedom from undifferentiated iPS cells. Determination of the necessary cell dose is also critical; it is assumed that a minimum of 1 billion transplantable cells is required to achieve a therapeutic effect. This will request medium to long-term in vitro cultivation and dozens of cell divisions, bearing the risk of accumulating replication errors. Here, we review the clinical potential of human iPS cells and evaluate which are the most suitable approaches to overcome or minimize risks associated with the application of iPS cell-derived cell therapies.

Zinc supplementation during in vitro maturation increases the production efficiency of cloned pigs

Zinc supplementation (0.8 µg/ml) in in vitro maturation (IVM) medium significantly enhances oocyte quality. In this study, we compared the development of somatic cell nuclear transfer (SCNT) embryos produced from conventional IVM (control) and zinc-supplemented IVM oocytes. A total of 1206 and 890 SCNT embryos were produced using control and zinc-supplemented oocytes, respectively, and then were transferred to 11 and 8 recipients, respectively. Five control recipients and three zinc-supplemented recipients became pregnant. Two live piglets and eight mummies were born from two control recipients, and ten live piglets and six stillborn piglets were born from three zinc-supplemented recipients. The production efficiency significantly increased in the zinc-supplemented group (0.33% vs. 3.02%). This report suggests that zinc supplementation in IVM medium improved the production efficiency of cloned pigs.

Diet before and during Pregnancy and Offspring Health: The Importance of Animal Models and What Can Be Learned from Them

This review article outlines epidemiologic studies that support the hypothesis that maternal environment (including early nutrition) plays a seminal role in determining the offspring’s long-term health and metabolism, known as the concept of Developmental Origins of Health and Diseases (DOHaD). In this context, current concerns are particularly focused on the increased incidence of obesity and diabetes, particularly in youth and women of child-bearing age. We summarize key similarities, differences and limitations of various animal models used to study fetal programming, with a particular focus on placentation, which is critical for translating animal findings to humans. This review will assist researchers and their scientific audience in recognizing the pros and cons of various rodent and non-rodent animal models used to understand mechanisms involved in fetal programming. Knowledge gained will lead to improved translation of proposed interventional therapies before they can be implemented in humans. Although rodents are essential for fundamental exploration of biological processes, other species such as rabbits and other domestic animals offer more tissue-specific physiological (rabbit placenta) or physical (ovine maternal and lamb birth weight) resemblances to humans. We highlight the important maternal, placental, and fetal/neonatal characteristics that contribute to developmentally programmed diseases, specifically in offspring that were affected in utero by undernutrition, overnutrition or maternal diabetes. Selected interventions aimed at prevention are summarized with a specific focus on the 1000 days initiative in humans, and maternal exercise or modification of the n-3/n-6 polyunsaturated fatty acid (PUFA) balance in the diet, which are currently being successfully tested in animal models to correct or reduce adverse prenatal programming. Animal models are essential to understand mechanisms involved in fetal programming and in order to propose interventional therapies before they can be implemented in humans. Non-rodent animals are particularly important and should not be neglected, as they are often more physiologically-appropriate models to mimic the human situation.

Gene targeting, genome editing: from Dolly to editors

One of the most powerful strategies to investigate biology we have as scientists, is the ability to transfer genetic material in a controlled and deliberate manner between organisms. When applied to livestock, applications worthy of commercial venture can be devised. Although initial methods used to generate transgenic livestock resulted in random transgene insertion, the development of SCNT technology enabled homologous recombination gene targeting strategies to be used in livestock. Much has been accomplished using this approach. However, now we have the ability to change a specific base in the genome without leaving any other DNA mark, with no need for a transgene. With the advent of the genome editors this is now possible and like other significant technological leaps, the result is an even greater diversity of possible applications. Indeed, in merely 5 years, these 'molecular scissors' have enabled the production of more than 300 differently edited pigs, cattle, sheep and goats. The advent of genome editors has brought genetic engineering of livestock to a position where industry, the public and politicians are all eager to see real use of genetically engineered livestock to address societal needs. Since the first transgenic livestock reported just over three decades ago the field of livestock biotechnology has come a long way-but the most exciting period is just starting.

Generation of liver-specific TGF-α/c-Myc-overexpressing porcine induced pluripotent stem-like cells and blastocyst formation using nuclear transfer

Transgenic porcine induced pluripotent stem (iPS) cells are attractive cell sources for the development of genetically engineered pig models, because they can be expanded without senescence and have the potential for multiple gene manipulation. They are also useful cell sources for disease modeling and treatment. However, the generation of transgenic porcine iPS cells is rare, and their embryonic development after nuclear transfer (NT) has not yet been reported. We report here the generation of liver-specific oncogenes (TGF-α/c-Myc)-overexpressing porcine iPS (T/M iPS)-like cells. They expressed stem cell characteristics and were differentiated into hepatocyte-like cells that express oncogenes. We also confirmed that NT embryos derived from T/M iPS-like cells successfully developed blastocysts in vitro. As an initial approach toward porcine transgenic iPS cell generation and their developmental competence after NT, this study provides foundations for the efficient generation of genetically modified porcine iPS cells and animal models.

Comparative aspects of rodent and nonrodent animal models for mechanistic and translational diabetes research

The prevalence of diabetes mellitus, which currently affects 387 million people worldwide, is permanently rising in both adults and adolescents. Despite numerous treatment options, diabetes mellitus is a progressive disease with severe comorbidities, such as nephropathy, neuropathy, and retinopathy, as well as cardiovascular disease. Therefore, animal models predictive of the efficacy and safety of novel compounds in humans are of great value to address the unmet need for improved therapeutics. Although rodent models provide important mechanistic insights, their predictive value for therapeutic outcomes in humans is limited. In recent years, the pig has gained importance for biomedical research because of its close similarity to human anatomy, physiology, size, and, in contrast to non-human primates, better ethical acceptance. In this review, anatomic, biochemical, physiological, and morphologic aspects relevant to diabetes research will be compared between different animal species, that is, mouse, rat, rabbit, pig, and non-human primates. The value of the pig as a model organism for diabetes research will be highlighted, and (dis)advantages of the currently available approaches for the generation of pig models exhibiting characteristics of metabolic syndrome or type 2 diabetes mellitus will be discussed.

Tissue Sampling Guides for Porcine Biomedical Models

This article provides guidelines for organ and tissue sampling adapted to porcine animal models in translational medical research. Detailed protocols for the determination of sampling locations and numbers as well as recommendations on the orientation, size, and trimming direction of samples from ∼50 different porcine organs and tissues are provided in the Supplementary Material. The proposed sampling protocols include the generation of samples suitable for subsequent qualitative and quantitative analyses, including cryohistology, paraffin, and plastic histology; immunohistochemistry;in situhybridization; electron microscopy; and quantitative stereology as well as molecular analyses of DNA, RNA, proteins, metabolites, and electrolytes. With regard to the planned extent of sampling efforts, time, and personnel expenses, and dependent upon the scheduled analyses, different protocols are provided. These protocols are adjusted for (I) routine screenings, as used in general toxicity studies or in analyses of gene expression patterns or histopathological organ alterations, (II) advanced analyses of single organs/tissues, and (III) large-scale sampling procedures to be applied in biobank projects. Providing a robust reference for studies of porcine models, the described protocols will ensure the efficiency of sampling, the systematic recovery of high-quality samples representing the entire organ or tissue as well as the intra-/interstudy comparability and reproducibility of results.

Genetically engineered livestock for biomedical models

To commemorate Transgenic Animal Research Conference X, this review summarizes the recent progress in developing genetically engineered livestock species as biomedical models. The first of these conferences was held in 1997, which turned out to be a watershed year for the field, with two significant events occurring. One was the publication of the first transgenic livestock animal disease model, a pig with retinitis pigmentosa. Before that, the use of livestock species in biomedical research had been limited to wild-type animals or disease models that had been induced or were naturally occurring. The second event was the report of Dolly, a cloned sheep produced by somatic cell nuclear transfer. Cloning subsequently became an essential part of the process for most of the models developed in the last 18 years and is stilled used prominently today. This review is intended to highlight the biomedical modeling achievements that followed those key events, many of which were first reported at one of the previous nine Transgenic Animal Research Conferences. Also discussed are the practical challenges of utilizing livestock disease models now that the technical hurdles of model development have been largely overcome.

Multi‑transgenic minipig models exhibiting potential for hepatic insulin resistance and pancreatic apoptosis

There are currently no multi‑transgenic minipig models of diabetes for the regulation of multiple genes involved in its pathogenesis. The foot and mouth disease virus 2A (F2A)‑mediated polycistronic system possesses several advantages, and the present study developed a novel multi‑transgenic minipig model associated with diabetes using this system. The tissue‑specific polycistronic system used in the present study consisted of two expression cassettes, separated by an insulator: (i) 11‑β‑hydroxysteroid dehydrogenase 1 (11β‑HSD1), driven by the porcine liver‑specific apolipoprotein E promoter; (ii) human islet amyloid polypeptide (hIAPP) and C/EBP homologous protein (CHOP), linked to the furin digested site and F‑2A, driven by the porcine pancreas‑specific insulin promoter. In the present study, porcine fetal fibroblasts were transfected with this vector. Following somatic cell nuclear transfer using 10 cell clones and the transplantation of 1,459 embryos in total, three Landrace x Yorkshire surrogates became pregnant and delivered three Wuzhishan piglets. Genomic polymerase chain reaction (PCR) demonstrated that the piglets were multi‑transgenic. Reverse transcription‑quantitative PCR confirmed that 11β‑HSD1 transcription was upregulated in the targeted liver. Similarly, hIAPP and CHOP were expressed at high levels, compared with the control (P<0.05 and P<0.01) in the pancreas, consistent with the western blotting and immunohistochemistry results. The primary results also showed that overexpression of 11β‑HSD1 in the liver increased the liver fat lipid parameters; and the levels of hIAPP and CHOP in the pancreatic islet cells, leading to delayed β‑cell development and apoptosis. This novel tissue‑specific polycistronic system offers a promising starting point for efficiently mimicking multigenic metabolic disease.

Fetal Sex Modulates Developmental Response to Maternal Malnutrition

The incidence of obesity and metabolic diseases is dramatically high in rapidly developing countries. Causes have been related to intrinsic ethnic features with development of a thrifty genotype for adapting to food scarcity, prenatal programming by undernutrition, and postnatal exposure to obesogenic lifestyle. Observational studies in humans and experimental studies in animal models evidence that the adaptive responses of the offspring may be modulated by their sex. In the contemporary context of world globalization, the new question arising is the existence and extent of sex-related differences in developmental and metabolic traits in case of mixed-race. Hence, in the current study, using a swine model, we compared male and female fetuses that were crossbred from mothers with thrifty genotype and fathers without thrifty genotype. Female conceptuses evidence stronger protective strategies for their adequate growth and postnatal survival. In brief, both male and female fetuses developed a brain-sparing effect but female fetuses were still able to maintain the development of other viscerae than the brain (mainly liver, intestine and kidneys) at the expense of carcass development. Furthermore, these morphometric differences were reinforced by differences in nutrient availability (glucose and cholesterol) favoring female fetuses with severe developmental predicament. These findings set the basis for further studies aiming to increase the knowledge on the interaction between genetic and environmental factors in the determination of adult phenotype