Production and Breeding of Transgenic Cloned Pigs Expressing Human CD73

RRM2 promotes the proliferation of chicken myoblasts, inhibits their differentiation and muscle regeneration

During myogenesis and regeneration, the proliferation and differentiation of myoblasts play key regulatory roles and may be regulated by many genes. In this study, we analyzed the transcriptomic data of chicken primary myoblasts at different periods of proliferation and differentiation with protein‒protein interaction network, and the results indicated that there was an interaction between cyclin-dependent kinase 1 (CDK1) and ribonucleotide reductase regulatory subunit M2 (RRM2). Previous studies in mammals have a role for RRM2 in skeletal muscle development as well as cell growth, but the role of RRM2 in chicken is unclear. In this study, we investigated the effects of RRM2 on skeletal muscle development and regeneration in chickens in vitro and in vivo. The interaction between RRM2 and CDK1 was initially identified by co-immunoprecipitation and mass spectrometry. Through a dual luciferase reporter assay and quantitative real-time PCR, we identified the core promoter region of RRM2, which is regulated by the SP1 transcription factor. In this study, through cell counting kit-8 assays, 5-ethynyl-2'-deoxyuridine incorporation assays, flow cytometry, immunofluorescence staining, and Western blot analysis, we demonstrated that RRM2 promoted the proliferation and inhibited the differentiation of myoblasts. In vivo studies showed that RRM2 reduced the diameter of muscle fibers and slowed skeletal muscle regeneration. In conclusion, these data provide preliminary insights into the biological functions of RRM2 in chicken muscle development and skeletal muscle regeneration.

Identification of the Porcine Vascular Endothelial Cell-Specific Promoter ESAM1.0 Using Transcriptome Analysis

The vascular endothelium of xenografted pig organs represents the initial site of rejection after exposure to recipient immune cells. In this study, we aimed to develop a promoter specific to porcine vascular endothelial cells as a step toward overcoming xenograft rejection. Transcriptome analysis was performed on porcine aortic endothelial cells (PAECs), ear skin fibroblasts isolated from GGTA knockout (GTKO) pigs, and the porcine renal epithelial cell line pk-15. RNA sequencing confirmed 243 differentially expressed genes with expression changes of more than 10-fold among the three cell types. Employing the Human Protein Atlas database as a reference, we identified 34 genes exclusive to GTKO PAECs. The endothelial cell-specific adhesion molecule (ESAM) was selected via qPCR validation and showed high endothelial cell specificity and stable expression across tissues. We selected 1.0 kb upstream sequences of the translation start site of the gene as the promoter ESAM1.0. A luciferase assay revealed that ESAM1.0 promoter transcriptional activity was significant in PAECs, leading to a 2.8-fold higher level of expression than that of the porcine intercellular adhesion molecule 2 (ICAM2) promoter, which is frequently used to target endothelial cells in transgenic pigs. Consequently, ESAM1.0 will enable the generation of genetically modified pigs with endothelium-specific target genes to reduce xenograft rejection.

Endothelial Effects of Simultaneous Expression of Human HO-1, E5NT, and ENTPD1 in a Mouse

The vascular endothelium is key target for immune and thrombotic responses that has to be controlled in successful xenotransplantation. Several genes were identified that, if induced or overexpressed, help to regulate the inflammatory response and preserve the transplanted organ function and metabolism. However, few studies addressed combined expression of such genes. The aim of this work was to evaluate in vivo the effects of the simultaneous expression of three human genes in a mouse generated using the multi-cistronic F2A technology. Male 3-month-old mice that express human heme oxygenase 1 (hHO-1), ecto-5'-nucleotidase (hE5NT), and ecto-nucleoside triphosphate diphosphohydrolase 1 (hENTPD1) (Transgenic) were compared to wild-type FVB mice (Control). Background analysis include extracellular nucleotide catabolism enzymes profile on the aortic surface, blood nucleotide concentration, and serum L-arginine metabolites. Furthermore, inflammatory stress induced by LPS in transgenic and control mice was used to characterize interleukin 6 (IL-6) and adhesion molecules endothelium permeability responses. Transgenic mice had significantly higher rates of extracellular adenosine triphosphate and adenosine monophosphate hydrolysis on the aortic surface in comparison to control. Increased levels of blood AMP and adenosine were also noticed in transgenics. Moreover, transgenic animals demonstrated the decrease in serum monomethyl-L-arginine level and a higher L-arginine/monomethyl-L-arginine ratio. Importantly, significantly decreased serum IL-6, and adhesion molecule levels were observed in transgenic mice in comparison to control after LPS treatment. Furthermore, reduced endothelial permeability in the LPS-treated transgenic mice was noted as compared to LPS-treated control. The human enzymes (hHO-1, hE5NT, hENTPD1) simultaneously encoded in transgenic mice demonstrated benefits in several biochemical and functional aspects of endothelium. This is consistent in use of this approach in the context of xenotransplantation.

Cardiac xenotransplantation: from concept to clinic

For many patients with terminal/advanced cardiac failure, heart transplantation is the most effective, durable treatment option, and offers the best prospects for a high quality of life. The number of potentially life-saving donated human organs is far fewer than the population who could benefit from a new heart, resulting in increasing numbers of patients awaiting replacement of their failing heart, high waitlist mortality, and frequent reliance on interim mechanical support for many of those deemed among the best candidates but who are deteriorating as they wait. Currently, mechanical assist devices supporting left ventricular or biventricular heart function are the only alternative to heart transplant that is in clinical use. Unfortunately, the complication rate with mechanical assistance remains high despite advances in device design and patient selection and management, and the quality of life of the patients even with good outcomes is only moderately improved. Cardiac xenotransplantation from genetically multi-modified (GM) organ-source pigs is an emerging new option as demonstrated by the consistent long-term success of heterotopic (non-life-supporting) abdominal and life-supporting orthotopic porcine heart transplantation in baboons, and by a recent 'compassionate use' transplant of the heart from a GM pig with 10 modifications into a terminally ill patient who survived for 2 months. In this review, we discuss pig heart xenotransplantation as a concept, including pathobiological aspects related to immune rejection, coagulation dysregulation, and detrimental overgrowth of the heart, as well as GM strategies in pigs to prevent or minimize these problems. Additional topics discussed include relevant results of heterotopic and orthotopic heart transplantation experiments in the pig-to-baboon model, microbiological and virologic safety concepts, and efficacy requirements for initiating formal clinical trials. An adequate regulatory and ethical framework as well as stringent criteria for the selection of patients will be critical for the safe clinical development of cardiac xenotransplantation, which we expect will be clinically tested during the next few years.

Transgenic Rodent Models in Toxicological and Environmental Research: Future Perspectives

The coexistence of humans and animals has existed for centuries. Over the past decade, animal research has played a critical role in drug development and discovery. More and more diverse animals, including transgenic animals, are used in basic research than in applied research. Transgenic animals are generated using molecular genetic techniques to add functional genes, alter gene products, delete genes, insert reporter genes into regulatory sequences, replace or repair genes, and make changes in gene expression. These genetically engineered animals are unique tools for studying a wide range of biomedical issues, allowing the exhibition of specific genetic alterations in various biological systems. Over the past two decades, transgenic animal models have played a critical role in improving our understanding of gene regulation and function in biological systems and human disease. This review article aims to highlight the role of transgenic animals in pharmacological, toxicological, and environmental research. The review accounts for various types of transgenic animals and their appropriateness in multiple types of studies.

Mechanisms and strategies to promote cardiac xenotransplantation

End stage heart failure is a terminal disease, and the only curative therapy is orthotopic heart transplantation. Due to limited organ availability, alternative strategies have received intense interest for treatment of patients with advanced heart failure. Recent studies using gene-edited porcine organs suggest that cardiac xenotransplantation may provide a future source of organs. In this review, we highlight the historical milestones for cardiac xenotransplantation and the gene editing strategies designed to overcome immunological barriers, which have culminated in a recent cardiac pig-to-human xenotransplant. We also discuss recent results of studies on the engineering of human-porcine chimeric organs that may provide an alternative and complementary strategy to overcome some of the major immunological barriers to producing a new source of transplantable organs.

Bioinformatic analysis as a first step to predict the compatibility of hematopoiesis and immune system genes between humans and pigs

The shortage of allogeneic donor organs leaves its supply far short of clinical need. There are great expectations on xenotransplantation, especially with pigs' organs. With the genetic modification of donor pigs, the rejection and cross-species transmission issues have now been widely addressed. However, research on the compatibility of genes between humans and pigs was limited. We performed a systematic screening analysis of predicted incompatible genes between humans and pigs, judged by low protein sequence similarities or different predicted protein domain compositions. By combining with gene set enrichment analysis, we screened out several key genes of hematopoiesis and the immune system with possible incompatibilities, which might be important for establishing chimera and xenotransplantation between humans and pigs. There were seven chemokine genes, including CCL1, CCL5, CCL24, CCL25, CCL28, CXCL12, and CXCL16, that exhibited limited similarity between humans and pigs (similarity < 0.8). Among hematopoiesis process-related genes, 15 genes of adhesion molecules, Notch ligands, and cytokine receptors exhibited differences between humans and pigs. In complement and coagulation cascades, 19 genes showed low similarity and 77 genes had different domain compositions between humans and pigs. Our study provides a good reference for further genetic modification of pigs, which might be beneficial for xenotransplantation.

Technical, Biological and Molecular Aspects of Somatic Cell Nuclear Transfer – A Review

Since the announcement of the birth of the first cloned mammal in 1997, Dolly the sheep, 24 animal species including laboratory, farm, and wild animals have been cloned. The technique for somatic cloning involves transfer of the donor nucleus of a somatic cell into an enucleated oocyte at the metaphase II (MII) stage for the generation of a new individual, genetically identical to the somatic cell donor. There is increasing interest in animal cloning for different purposes such as rescue of endangered animals, replication of superior farm animals, production of genetically engineered animals, creation of biomedical models, and basic research. However, the efficiency of cloning remains relatively low. High abortion, embryonic, and fetal mortality rates are frequently observed. Moreover, aberrant developmental patterns during or after birth are reported. Researchers attribute these abnormal phenotypes mainly to incomplete nuclear remodeling, resulting in incomplete reprogramming. Nevertheless, multiple factors influence the success of each step of the somatic cloning process. Various strategies have been used to improve the efficiency of nuclear transfer and most of the phenotypically normal born clones can survive, grow, and reproduce. This paper will present some technical, biological, and molecular aspects of somatic cloning, along with remarkable achievements and current improvements.

Select Porcine Elongation Factor 1α Sequences Mediate Stable High-Level and Upregulated Expression of Heterologous Genes in Porcine Cells in Response to Primate Serum

Genetically engineered (GE) pigs with various combinations of genetic profiles have been developed using heterologous promoters. This study aimed to identify autologous promoters for high and ubiquitous expression of xenotransplantation relevant genes in GE pigs. A 1.4 kb upstream regulatory sequence of porcine elongation factor 1α (pEF1α) gene was selected and isolated for use as a promoter. Activity of the pEF1α promoter was subsequently compared with that of the cytomegalovirus (CMV) promoter, CMV enhancer/chicken β-actin (CAG) promoter, and human EF1α (hEF1α) promoter in different types of pig-derived cells. Comparative analysis of luciferase and mutant human leukocyte antigen class E-F2A-β-2 microglobulin (HLA-E) expression driven by pEF1α, CMV, CAG, and hEF1α promoters revealed the pEF1α promoter mediated comparable expression levels with those of the CAG promoter in porcine ear skin fibroblasts (PEFs) and porcine kidney-15 (PK-15) cells, but lower than those of the CAG promoter in porcine aortic endothelial cells (PAECs). The pEF1α promoter provided long-term stable HLA-E expression in PEFs, but the CAG promoter failed to sustain those levels of expression. For xenogeneic serum-induced cytotoxicity assays, the cells were cultured for several hours in growth medium supplemented with primate serum. Notably, the pEF1α promoter induced significant increases in luciferase and HLA-E expression in response to primate serum in PAECs compared with those driven by the CAG promoter, suggesting the pEF1α promoter could regulate temporal expression of heterologous genes under xenogeneic-cytotoxic conditions. These results suggest the pEF1α promoter may be valuable for development of GE pigs spatiotemporally and stably expressing immunomodulatory genes for xenotransplantation.

Immunogenetics of xenotransplantation

Xenotransplantation may become the highly desired solution to close the gap between the availability of donated organs and number of patients on the waiting list. In recent years, enormous progress has been made in the development of genetically engineered donor pigs. The introduced genetic modifications showed to be efficient in prolonging xenograft survival. In this review, we focus on the type of immune responses that may target xeno-organs after transplantation and promising immunogenetic modifications that show a beneficial effect in ameliorating or eliminating harmful xenogeneic immune responses. Increasing histocompatibility of xenografts by eliminating genetic discrepancies between species will pave their way into clinical application.

Porcine genome engineering for xenotransplantation

The extreme shortage of human donor organs for treatment of patients with end-stage organ failures is well known. Xenotransplantation, which might provide unlimited organ supply, is a most promising strategy to solve this problem. Domestic pigs are regarded as ideal organ-source animals owing to similarity in anatomy, physiology and organ size to humans as well as high reproductive capacity and low maintenance cost. However, several barriers, which include immune rejection, inflammation and coagulative dysfunctions, as well as the cross-species transmission risk of porcine endogenous retrovirus, blocked the pig-to-human xenotransplantation. With the rapid development of genome engineering technologies and the potent immunosuppressive medications in recent years, these barriers could be eliminated through genetic modification of pig genome together with the administration of effective immunosuppressants. A number of candidate genes involved in the regulation of immune response, inflammation and coagulation have been explored to optimize porcine xenograft survival in non-human primate recipients. PERV inactivation in pigs has also been accomplished to firmly address the safety issue in pig-to-human xenotransplantation. Many encouraging preclinical milestones have been achieved with some organs surviving for years. Therefore, the clinical trials of some promising organs, such as islet, kidney and heart, are aimed to be launched in the near future.

Skin xenotransplantation: technological advances and future directions

PURPOSE OF REVIEW

To summarize the evolution of skin xenotransplantation and contextualize technological advances and the status of clinically applicable large animal research as well as prospects for translation of this work as a viable future treatment option.

RECENT FINDINGS

Porcine xenografts at the start of the millennium were merely biologic dressings subject to rapid rejection. Since then, numerous important advances in swine to nonhuman primate models have yielded xenotransplant products at the point of clinical translation. Critical genetic modifications in swine from a designated pathogen-free donor herd have allowed xenograft survival reaching 30 days without preconditioning or maintenance immunosuppression. Further, xenograft coverage appears not to sensitize the recipient to subsequent allograft placement and vice versa, allowing for temporary coverage times to be doubled using both xeno and allografts.

SUMMARY

Studies in large animal models have led to significant progress in the creation of living, functional skin xenotransplants with clinically relevant shelf-lives to improve the management of patients with extensive burns.

The Influence of the Flow of Detergent and Donor Characteristics on the Extracellular Matrix Composition After Human Pancreas Decellularization

INTRODUCTION

The extracellular matrix (ECM) consists, among others, of polysaccharides, glycosaminoglycans, and proteins. It is being increasingly used in tissue bioengineering. Obtaining ECM of the highest quality through decellularization is a big challenge because of some differences in organ structure. To deprive organs of the cellular part, chemical, enzymatic, or mechanical methods are used. After decellularization, we get a scaffold made of a variety of proteins, and it is the role of these proteins that can significantly affect the maintenance of the spatial structure and be a suitable environment for cells to rebuild a specific organ.

AIM

Estimation of the detergent (Triton X-100) flow parameters and anthropometric donors' decellularization process accuracy on the final ECM composition.

MATERIALS

Five human pancreata, rejected from transplantation, were used for decellularization. All organs were harvested from brain-dead donors age 13 to 60 years.

METHODS

Decellularization was carried out using the flow method with Triton X-100 as an active agent. The experiment compared 5 different flow values. After decellularization, an assessment of the final DNA concentration and the protein composition was performed. Results were compared to anthropometric data of donors. In addition, a microscopic analysis was also carried out.

RESULTS

The best results were obtained using a flow of 120 mL/minute. A higher detergent flow was associated with a lower concentration of residual DNA in scaffold. Analysis of the protein profile with anthropometric data has shown that LAM A2 was increasing with age and LAMA5 was decreasing. Being overweight was associated with a higher proportion of COL1 and 4 and a smaller proportion of COL6.

Developmental and Degenerative Characterization of Porcine Parthenogenetic Fetuses during Early Pregnancy

Simple Summary

To increase the early implantation rate, oocytes and zygotes have been subjected to various artificial stimulations before and/or after in vitro fertilization, nuclear transfer, or sperm (spermatid) injection, etc. However, the stimulation process may induce parthenogenetic development. It is difficult to identify whether the embryo or fetus is normally fertilized or parthenogenetically activated in early pregnancy. In the present study, the porcine parthenotes originated from electric stimulation implanted and developed normally during the first month, in a manner similar to artificially inseminated embryos and fetuses. There were no statistical differences in the formation of the major organs such as the brain, liver, kidney, or heart in both groups. However, the implanted parthenotes radically ceased their development and degenerated after one month. It can be postulated that the parthenotes are one of the reasons for the gap between early pregnancy and delivery rate in assisted reproduction techniques.

Abstract

The difference between early pregnancy and delivery rate is quite large in assisted reproduction techniques (ARTs), including animal cloning. However, it is not clear why the implanted fetuses aborted after the early pregnancy stage. In the present study, we tried to evaluate the developmental and morphological characteristics of porcine parthenogenetically activated (PA) embryos or fetuses by electric stimulation during the early pregnancy period. The implanted PA and artificially inseminated (AI) embryos and fetuses were collected at day 26 and 35 after embryo transfer, respectively. The developmental and morphological parameters in the PA embryos at day 26 were similar to the AI embryos. The size, weight, formation of major organs, and apoptotic cells were not statistically different in both embryos at day 26. However, the PA fetuses at day 35 showed ceased fetal development and degenerated with abnormal morphologies in their organs. The day 35 PA fetuses showed significantly higher apoptotic cells and lower methylation status in three differentially methylated regions of the H19 gene compared to their comparators. Therefore, the normal development of PA embryos and fetuses during early gestation could lead to these pregnancies being misinterpreted as normal and become one of the main reasons for the gap between early pregnancy and delivery rate.

CRISPR/Cas9-Mediated Biallelic Knockout of IRX3 Reduces the Production and Survival of Somatic Cell-Cloned Bama Minipigs

Bama minipigs are a local pig breed that is unique to China and has a high development and utilization value. However, its high fat content, low feed utilization rate, and slow growth rate have limited its popularity and utilization. Compared with the long breeding cycle and high cost of traditional genetic breeding of pigs, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) endonuclease 9 system (CRISPR/Cas9)-mediated gene editing can cost-effectively implement targeted mutations in animal genomes, thereby providing a powerful tool for rapid improvement of the economic traits of Bama minipigs. The iroquois homeobox 3 (IRX3) gene has been implicated in human obesity. Mouse experiments have shown that knocking out IRX3 significantly enhances basal metabolism, reduces fat content, and controls body mass and composition. This study aimed to knock out IRX3 using the CRISPR/Cas9 gene editing method to breed Bama minipigs with significantly reduced fat content. First, the CRISPR/Cas9 gene editing method was used to efficiently obtain IRX3-/- cells. Then, the gene-edited cells were used as donor cells to produce surviving IRX3-/- Bama minipigs using somatic cell cloning. The results show that the use of IRX3-/- cells as donor cells for the production of somatic cell-cloned pigs results in a significant decrease in the average live litter size and a significant increase in the average number of stillbirths. Moreover, the birth weight of surviving IRX3-/- somatic cell-cloned pigs is significantly lower, and viability is poor such that all piglets die shortly after birth. Therefore, the preliminary results of this study suggest that IRX3 may have important biological functions in pigs, and IRX3 should not be used as a gene editing target to reduce fat content in Bama minipigs. Moreover, this study shows that knocking out IRX3 does not favor the survival of pigs, and whether targeted regulation of IRX3 in the treatment of human obesity will also induce severe adverse consequences requires further investigation.

Identifying Biomarkers of Autophagy and Apoptosis in Transfected Nuclear Donor Cells and Transgenic Cloned Pig Embryos

In this study, we first investigated the effects of 3-methyladenine (3-MA), an autophagy inhibitor, and the inducer – rapamycin (RAPA) on the incidence of programmed cell death (PCD) symptoms during in vitro development of porcine somatic cell nuclear transfer (SCNT)-derived embryos. The expression of autophagy inhibitor mTOR protein was decreased in porcine SCNT blastocysts treated with 3MA. The abundance of the autophagy marker LC3 increased in blastocysts following RAPA treatment. Exposure of porcine SCNT-derived embryos to 3-MA suppressed their developmental abilities to reach the blastocyst stage. No significant difference in the expression pattern of PCD-related proteins was found between non-transfected dermal cell and transfected dermal cell groups. Additionally, the pattern of PCD in SCNT-derived blastocysts generated using SC and TSC was not significantly different, and in terms of porcine SCNT-derived embryo development rates and total blastocyst cell numbers, there was no significant difference between non-transfected cells and transfected cells. In conclusion, regulation of autophagy affected the development of porcine SCNT embryos. Regardless of the type of nuclear donor cells (transfected or non-transfected dermal cells) used for SCNT, there was no difference in the developmental potential and quantitative profiles of autophagy/apoptosis biomarkers between porcine transgenic and non-transgenic cloned embryos. These results led us to conclude that PCD is important for controlling porcine SCNT-derived embryo development, and that transfected dermal cells can be utilized as a source of nuclear donors for the production of transgenic cloned progeny in pigs.

Will Genetic Engineering Carry Xenotransplantation of Pig Islets to the Clinic?

PURPOSE OF REVIEW

Porcine islets represent a potentially attractive beta-cell source for xenotransplantation into patients with type 1 diabetes, who are not eligible to islet allo-transplantation due to a lack of suitable human donor organs. Recent progress in genetic engineering/gene editing of donor pigs provides new opportunities to overcome rejection of xeno-islets, to improve their engraftment and insulin secretion capacity, and to reduce the risk for transmission of porcine endogenous retroviruses. This review summarizes the current issues and progress in islet xenotransplantation with special emphasis on genetically modified/gene edited donor pigs.

RECENT FINDINGS

Attempts to overcome acute rejection of xeno-islets, especially after intraportal transplantation into the liver, include the genetic elimination of specific carbohydrate antigens such as αGal, Neu5Gc, and Sd(a) for which humans and-in part-non-human primates have natural antibodies that bind to these targets leading to activation of complement and coagulation. A complementary approach is the expression of one or more human complement regulatory proteins (hCD46, hCD55, hCD59). Transgenic attempts to overcome cellular rejection of islet xenotransplants include the expression of proteins that inhibit co-stimulation of T cells. Expression of glucagon-like peptide-1 and M3 muscarinic receptors has been shown to increase the insulin secretion of virally transduced porcine islets in vitro and it will be interesting to see the effects of these modifications in transgenic pigs and islet products derived from them. Genome-wide inactivation of porcine endogenous retrovirus (PERV) integrants by mutating their pol genes using CRISPR/Cas9 is a recent approach to reduce the risk for PERV transmission by xeno-islets. Genetic engineering/gene editing of xeno-islet donor pigs facilitated major progress towards clinical islet xenotransplantation. The required set of genetic modifications will depend on the source of islets (fetal/neonatal vs. adult), the mode of delivery (encapsulated vs. free), and the transplantation site.