Generation of Footprint-Free Canine Induced Pluripotent Stem Cells Using Auto-Erasable Sendai Virus Vector

Canine induced pluripotent stem cells can be successfully maintained in weekend-free culture systems

Canine induced pluripotent stem cells (ciPSCs) can provide useful insights into novel therapies in both veterinary and medical fields. However, limited accessibility to the present culture medium and requirement of considerable time, effort, and cost for routine ciPSC maintenance restrict advancement in ciPSC research. In addition, it is unknown whether ciPSC culture conditions influence differentiation propensity. We investigated the availability of the common human pluripotent stem cells (hPSCs) culture systems for ciPSC maintenance and the differentiation propensities of the ciPSCs maintained in these culture systems. StemFlex and mTeSR Plus supported PSC-like colony formation and pluripotency markers expression in ciPSCs even after five passages. Additionally, ciPSCs were maintained under weekend-free culture conditions with a stable growth rate, pluripotency marker expression, and differentiation abilities using vitronectin (VTN-N) and Geltrex. Following maintenance of spontaneously differentiated ciPSCs under various conditions by embryoid body formation, there were few differences in the differentiation propensities of ciPSCs among the tested culture conditions. Thus, ciPSCs were successfully cultured under weekend-free conditions for ciPSC maintenance using StemFlex or mTeSR Plus with VTN-N or Geltrex. The present study offers simpler and more effort-, time-, and cost-saving options for ciPSC culture systems, which may lead to further development in research using ciPSCs.

Generation of canine induced pluripotent stem cells under feeder-free conditions using Sendai virus vector encoding six canine reprogramming factors

Although it is in its early stages, canine induced pluripotent stem cells (ciPSCs) hold great potential for innovative translational research in regenerative medicine, developmental biology, drug screening, and disease modeling. However, almost all ciPSCs were generated from fibroblasts, and available canine cell sources for reprogramming are still limited. Furthermore, no report is available to generate ciPSCs under feeder-free conditions because of their low reprogramming efficiency. Here, we reanalyzed canine pluripotency-associated genes and designed canine LIN28A, NANOG, OCT3/4, SOX2, KLF4, and C-MYC encoding Sendai virus vector, called 159cf. and 162cf. We demonstrated that not only canine fibroblasts but also canine urine-derived cells, which can be isolated using a noninvasive and straightforward method, were successfully reprogrammed with or without feeder cells. ciPSCs existed in undifferentiated states, differentiating into the three germ layers in vitro and in vivo. We successfully generated ciPSCs under feeder-free conditions, which can promote studies in veterinary and consequently human regenerative medicines.

Pluripotent Stem Cells of Order Carnivora: Technical Perspective

Human and mouse induced pluripotent stem cells (PSCs) are widely used for studying early embryonic development and for modeling of human diseases. Derivation and studying of PSCs from model organisms beyond commonly used mice and rats may provide new insights into the modeling and treating human diseases. The order Carnivora representatives possess unique features and are already used for modeling human-related traits. This review focuses on the technical aspects of derivation of the Carnivora species PSCs as well as their characterization. Current data on dog, feline, ferret, and American mink PSCs are summarized.

Genetic Basis of Dilated Cardiomyopathy in Dogs and Its Potential as a Bidirectional Model

Simple Summary

Heart disease is a leading cause of death for both humans and dogs. Inherited heart diseases, including dilated cardiomyopathy (DCM), account for a proportion of these cases. Human and canine patients with DCM suffer from an enlarged heart that can no longer pump efficiently, resulting in heart failure. This causes symptoms or clinical signs like difficulty breathing, irregular heartbeat, and eventually death. The symptoms or clinical signs of this disease vary in age of onset at the beginning of symptoms, sex predisposition, and overall disease progression. Despite the many similarities in DCM in both species, only a few candidate genes so far have been linked to this disease in dogs versus tens of genes identified in human DCM. Additionally, the use of induced pluripotent stem cells, or engineered stem cells, has been widely used in the study of human genetic heart disease but has not yet been fully adapted to study heart disease in dogs. This review describes the current knowledge on the genetics and subtypes of naturally occurring DCM in dogs, and how advances in research might benefit the dog but also the human patient. Additionally, a novel method using canine engineered stem cells to uncover unknown contributions of mistakes in DNA to the progression of DCM will be introduced along with its applications for human DCM disease modeling and treatment.

Abstract

Cardiac disease is a leading cause of death for both humans and dogs. Genetic cardiomyopathies, including dilated cardiomyopathy (DCM), account for a proportion of these cases in both species. Patients may suffer from ventricular enlargement and systolic dysfunction resulting in congestive heart failure and ventricular arrhythmias with high risk for sudden cardiac death. Although canine DCM has similar disease progression and subtypes as in humans, only a few candidate genes have been found to be associated with DCM while the genetic background of human DCM has been more thoroughly studied. Additionally, experimental disease models using induced pluripotent stem cells have been widely adopted in the study of human genetic cardiomyopathy but have not yet been fully adapted for the in-depth study of canine genetic cardiomyopathies. The clinical presentation of DCM is extremely heterogeneous for both species with differences occurring based on sex predisposition, age of onset, and the rate of disease progression. Both genetic predisposition and environmental factors play a role in disease development which are identical in dogs and humans in contrast to other experimental animals. Interestingly, different dog breeds have been shown to develop distinct DCM phenotypes, and this presents a unique opportunity for modeling as there are multiple breed-specific models for DCM with less genetic variance than human DCM. A better understanding of DCM in dogs has the potential for improved selection for breeding and could lead to better overall care and treatment for human and canine DCM patients. At the same time, progress in research made for human DCM can have a positive impact on the care given to dogs affected by DCM. Therefore, this review will analyze the feasibility of canines as a naturally occurring bidirectional disease model for DCM in both species. The histopathology of the myocardium in canine DCM will be evaluated in three different breeds compared to control tissue, and the known genetics that contributes to both canine and human DCM will be summarized. Lastly, the prospect of canine iPSCs as a novel method to uncover the contributions of genetic variants to the pathogenesis of canine DCM will be introduced along with the applications for disease modeling and treatment.

Derivation of Ringed Seal (Phoca hispida) Induced Multipotent Stem Cells

Induced pluripotent stem (iPS) cells have been produced just for a few species among order Carnivora: snow leopard, Bengal tiger, serval, jaguar, cat, dog, ferret, and American mink. We applied the iPS cell derivation protocol to the ringed seal (Phoca hispida) fibroblasts. The resulting cell line had the expression of pluripotency marker gene Rex1. Differentiation in embryoid body-like structures allowed us to register expression of AFP, endoderm marker, and Cdx2, trophectoderm marker, but not neuronal (ectoderm) markers. The cells readily differentiated into adipocytes and osteocytes, mesoderm cell types of origin. Transcriptome analysis allowed us to conclude that the cell line does not resemble human pluripotent cells, and, therefore, most probably is not pluripotent. Thus, we produced ringed seal multipotent stem cell line capable of differentiation into adipocytes and osteocytes.

Canine induced pluripotent stem cell maintenance under feeder-free and chemically-defined conditions

Canine induced pluripotent stem cells (ciPSCs) provide a platform for regenerative veterinary medicine, disease modeling, and drug discovery. However, in the conventional method, ciPSCs are maintained using chemically-undefined media containing unknown animal components under on-murine embryonic fibroblast feeder conditions, which were reported to modify cell surface of iPSCs and increases the risk of immune rejection when the cells are transplanted into patients. Moreover, in the conventional method, ciPSCs are mechanically passaged, which requires much time and effort. Therefore, the large-scale expansion of ciPSCs is difficult, which should be resolved for using ciPSCs in clinical application and research. Here, it was shown that StemFit® AK02N and iMatrix-511 could maintain the pluripotency of ciPSCs using conventional culture method. Furthermore, it was demonstrated that the feeder-free and chemically-defined ciPSC culture systems using StemFit® AK02N and iMatrix-511 could stably maintain and allow the easy expansion of ciPSCs generated using N2B27 and StemFit® AK02N, without causing karyotype abnormalities. ciPSCs expressed several pluripotency markers and formed teratomas, including cells derived from three germ layers.

Perspectives of pluripotent stem cells in livestock

The recent progress in derivation of pluripotent stem cells (PSCs) from farm animals opens new approaches not only for reproduction, genetic engineering, treatment and conservation of these species, but also for screening novel drugs for their efficacy and toxicity, and modelling of human diseases. Initial attempts to derive PSCs from the inner cell mass of blastocyst stages in farm animals were largely unsuccessful as either the cells survived for only a few passages, or lost their cellular potency; indicating that the protocols which allowed the derivation of murine or human embryonic stem (ES) cells were not sufficient to support the maintenance of ES cells from farm animals. This scenario changed by the innovation of induced pluripotency and by the development of the 3 inhibitor culture conditions to support naïve pluripotency in ES cells from livestock species. However, the long-term culture of livestock PSCs while maintaining the full pluripotency is still challenging, and requires further refinements. Here, we review the current achievements in the derivation of PSCs from farm animals, and discuss the potential application areas.

Efficient Reprogramming of Canine Peripheral Blood Mononuclear Cells into Induced Pluripotent Stem Cells

Forced coexpression of the transcription factors Oct3/4, Klf4, Sox2, and c-Myc reprograms somatic cells into pluripotent stem cells (PSCs). Such induced PSCs (iPSCs) can generate any cell type of the adult body or indefinitely proliferate without losing their potential. Accordingly, iPSCs can serve as an unlimited cell source for the development of various disease models and regenerative therapies for animals and humans. Although canine peripheral blood mononuclear cells (PBMCs) can be easily obtained, they have a very low iPSC reprogramming efficiency. In this study, we determined the reprogramming efficiency of canine PBMCs under several conditions involving three types of media supplemented with small-molecule compounds. We found that canine iPSCs (ciPSCs) could be efficiently generated from PBMCs using N2B27 medium supplemented with leukemia inhibitory factor (LIF), basic fibroblast growth factor (bFGF), and a small-molecule cocktail (Y-27632, PD0325901, CHIR99021, A-83-01, Forskolin, and l-ascorbic acid). We generated five ciPSC lines that could be maintained in StemFit® medium supplemented with LIF. The SeVdp(KOSM)302L vectors were appropriately silenced in four ciPSC lines. Of the two lines characterized, both were positive for alkaline phosphatase activity and expressed pluripotency markers, including the Oct3/4, Sox2, and Nanog transcripts, as well as the octamer-binding transcription factor (OCT) 3/4 and NANOG proteins, and the SSEA-1 carbohydrate antigen. The ciPSCs could form embryoid bodies and differentiate into the three germ layers, as indicated by marker gene and protein expression. Furthermore, one ciPSC line formed teratomas comprising several tissues from every germ layer. Our ciPSC lines maintained a normal karyotype even after multiple passages. Moreover, our new reprogramming method was able to generate ciPSCs from multiple donor PBMCs. In conclusion, we developed an easy and efficient strategy for the generation of footprint-free ciPSCs from PBMCs. We believe that this strategy can be useful for disease modeling and regenerative medicine in the veterinary field.

The use of induced pluripotent stem cells in domestic animals: a narrative review

Induced pluripotent stem cells (iPSCs) are undifferentiated stem cells characterized by the ability to differentiate into any cell type in the body. iPSCs are a relatively new and rapidly developing technology in many fields of biology, including developmental anatomy and physiology, pathology, and toxicology. These cells have great potential in research as they are self-renewing and pluripotent with minimal ethical concerns. Protocols for their production have been developed for many domestic animal species, which have since been used to further our knowledge in the progression and treatment of diseases. This research is valuable both for veterinary medicine as well as for the prospect of translation to human medicine. Safety, cost, and feasibility are potential barriers for this technology that must be considered before widespread clinical adoption. This review will analyze the literature pertaining to iPSCs derived from various domestic species with a focus on iPSC production and characterization, applications for tissue and disease research, and applications for disease treatment.

Chromatin accessibility in canine stromal cells and its implications for canine somatic cell reprogramming

Naturally occurring disease in pet dogs is an untapped and unique resource for stem cell-based regenerative medicine translational research, given the many similarities and complexity such disease shares with their human counterparts. Canine-specific regulators of somatic cell reprogramming and pluripotency maintenance are poorly understood. While retroviral delivery of the four Yamanaka factors successfully reprogrammed canine embryonic fibroblasts, adult stromal cells remained resistant to reprogramming in spite of effective viral transduction and transgene expression. We hypothesized that adult stromal cells fail to reprogram due to an epigenetic barrier. Here, we performed assay for transposase-accessible chromatin using sequencing (ATAC-seq) on canine stromal and pluripotent stem cells, analyzing 51 samples in total, and establishing the global landscape of chromatin accessibility before and after reprogramming to induced pluripotent stem cells (iPSC). We also studied adult stromal cells that do not yield iPSC colonies to identify potential reprogramming barriers. ATAC-seq analysis identified distinct cell type clustering patterns and chromatin remodeling during embryonic fibroblast reprogramming. Compared with embryonic fibroblasts, adult stromal cells had a chromatin accessibility landscape that reflects phenotypic differentiation and somatic cell-fate stability. We ultimately identified 76 candidate genes and several transcription factor binding motifs that may be impeding somatic cell reprogramming to iPSC, and could be targeted for inhibition or activation, in order to improve the process in canines. These results provide a vast resource for better understanding of pluripotency regulators in dogs and provide an unbiased rationale for novel canine-specific reprogramming approaches.

Positioning canine induced pluripotent stem cells (iPSCs) in the reprogramming landscape of naïve or primed state in comparison to mouse and human iPSCs

AIMS

Deriving canine-induced pluripotent stem cells (ciPSCs) have paved the way for developing novel cell-based disease models and transplantation therapies in the dog. Though ciPSCs have been derived in the presence of Leukemia inhibitory factor (LIF) as well in the presence of basic fibroblast growth factor (bFGF), the positioning of ciPSCs in the naïve or the primed state of pluripotency remains elusive. This study aims to understand whether canine iPSCs belong to naïve or prime state in comparison to mouse (m) iPSCs and human (h) iPSCs.

MAIN METHODS

In the present study, we derived ciPSCs in presence of LIF and compared their state of pluripotency with that of miPSCs and hiPSCs by culturing them in the presence of LIF, bFGF, and LIF + bFGF. Gene expression level at transcript level was performed by RT-PCR and qRT-PCR and at the protein level was analysed by immunofluorescence. We also attempted to understand the pluripotency state using lipid body analysis by bodipy staining and blue fluorescence emission.

KEY FINDINGS

In contrast to miPSCs, the naïve pluripotent stem cells, ciPSCs showed the expression of FGF5 similar to that of primed pluripotent stem cell, hiPSCs. Compared to miPSCs, ciPSCs cultured in presence of LIF showed enhanced expression of primed pluripotent marker FGF5, similar to hiPSCs cultured in presence of bFGF. Upon culturing in hiPSC culture condition, ciPSCs showed enhanced expression of core pluripotency genes compared to miPSCs cultured in similar condition. However, ciPSCs expressed naïve pluripotent marker SSEA1 similar to miPSCs and lacked the expression of primed state marker SSEA4 unlike hiPSCs. Interestingly, for the first time, we demonstrate the ciPSC pluripotency using lipid body analysis wherein ciPSCs showed enhanced bodipy staining and blue fluorescence emission, reflecting the primed state of pluripotency. ciPSCs expressed higher levels of fatty acid synthase (FASN), the enzyme involved in the synthesis of palmitate, similar to that of hiPSCs and higher than that of miPSCs. As ciPSCs exhibit characteristic properties of both naïve and primed pluripotent state, it probably represents a unique intermediary state of pluripotency that is distinct from that of mice and human pluripotent stem cells.

SIGNIFICANCE

Elucidating the pluripotent state of ciPSCs assists in better understanding of the reprogramming events and development in different species. The study would provide a footprint of species-specific differences involved in reprogramming and the potential implication of iPSCs as a tool to analyse evolution.

Optimized Approaches for the Induction of Putative Canine Induced Pluripotent Stem Cells from Old Fibroblasts Using Synthetic RNAs

Simple Summary

A non-integrating and self-replicating Venezuelan equine encephalitis RNA replicon system can potentially make a great contribution to the generation of clinically applicable canine induced pluripotent stem cells. Our study shows a new method to utilize the synthetic RNA-based approach for canine somatic cell reprogramming regarding transfection and reprogramming efficiency.

Abstract

Canine induced pluripotent stem cells (ciPSCs) can provide great potential for regenerative veterinary medicine. Several reports have described the generation of canine somatic cell-derived iPSCs; however, none have described the canine somatic cell reprogramming using a non-integrating and self-replicating RNA transfection method. The purpose of this study was to investigate the optimal strategy using this approach and characterize the transition stage of ciPSCs. In this study, fibroblasts obtained from a 13-year-old dog were reprogrammed using a non-integrating Venezuelan equine encephalitis (VEE) RNA virus replicon, which has four reprogramming factors (collectively referred to as T7-VEE-OKS-iG and comprised of hOct4, hKlf4, hSox2, and hGlis1) and co-transfected with the T7-VEE-OKS-iG RNA and B18R mRNA for 4 h. One day after the final transfection, the cells were selected with puromycin (0.5 µg/mL) until day 10. After about 25 days, putative ciPSC colonies were identified showing TRA-1-60 expression and alkaline phosphatase activity. To determine the optimal culture conditions, the basic fibroblast growth factor in the culture medium was replaced with a modified medium supplemented with murine leukemia inhibitory factor (mLIF) and two kinase inhibitors (2i), PD0325901(MEK1/2 inhibitor) and CHIR99021 (GSK3β inhibitor). The derived colonies showed resemblance to naïve iPSCs in their morphology (dome-shaped) and are dependent on mLIF and 2i condition to maintain an undifferentiated phenotype. The expression of endogenous pluripotency markers such as Oct4, Nanog, and Rex1 transcripts were confirmed, suggesting that induced ciPSCs were in the late intermediate stage of reprogramming. In conclusion, the non-integrating and self-replicating VEE RNA replicon system can potentially make a great contribution to the generation of clinically applicable ciPSCs, and the findings of this study suggest a new method to utilize the VEE RNA approach for canine somatic cell reprogramming.

Oocytes, embryos and pluripotent stem cells from a biomedical perspective

The veterinary and animal science professions are rapidly developing and their inherent and historical connection to agriculture is challenged by more biomedical and medical directions of research. While some consider this development as a risk of losing identity, it may also be seen as an opportunity for developing further and more sophisticated competences that may ultimately feed back to veterinary and animal science in a synergistic way. The present review describes how agriculture-related studies on bovine in vitro embryo production through studies of putative bovine and porcine embryonic stem cells led the way to more sophisticated studies of human induced pluripotent stem cells (iPSCs) using e.g. gene editing for modeling of neurodegeneration in man. However, instead of being a blind diversion from veterinary and animal science into medicine, these advanced studies of human iPSC-derived neurons build a set of competences that allowed us, in a more competent way, to focus on novel aspects of more veterinary and agricultural relevance in the form of porcine and canine iPSCs. These types of animal stem cells are of biomedical importance for modeling of iPSC-based therapy in man, but in particular the canine iPSCs are also important for understanding and modeling canine diseases, as e.g. canine cognitive dysfunction, for the benefit and therapy of dogs.

Large Animal Models for the Clinical Application of Human Induced Pluripotent Stem Cells

Induced pluripotent stem cell (iPSC) technology offers a practically infinite and ethically acceptable source to obtain a variety of somatic cells. Coupled with the biotechnologies of cell therapy or tissue engineering, iPSC technology will enormously contribute to human regenerative medicine. Before clinical application, such human iPSC (hiPSC)-based therapies should be assessed using large animal models that more closely match biological or biomechanical properties of human patients. Therefore, it is critical to generate large animal iPSCs, obtain their iPSC-derived somatic cells, and preclinically evaluate their therapeutic efficacy and safety in large animals. During the past decade, the establishment of iPSC lines of a series of large animal species has been documented, and the acquisition and preclinical evaluation of iPSC-derived somatic cells has also been reported. Despite this progress, significant obstacles, such as obtaining or preserving the bona fide pluripotency of large animal iPSCs, have been encountered. Simultaneously, studies of large animal iPSCs have been overlooked in comparison with those of mouse and hiPSCs, and this field deserves more attention and support due to its important preclinical relevance. Herein, this review will focus on the large animal models of pigs, dogs, horses, and sheep/goats, and summarize current progress, challenges, and potential future directions of research on large animal iPSCs.

Induced pluripotent stem cells throughout the animal kingdom: Availability and applications

Up until the mid 2000s, the capacity to generate every cell of an organism was exclusive to embryonic stem cells. In 2006, researchers Takahashi and Yamanaka developed an alternative method of generating embryonic-like stem cells from adult cells, which they coined induced pluripotent stem cells (iPSCs). Such iPSCs possess most of the advantages of embryonic stem cells without the ethical stigma associated with derivation of the latter. The possibility of generating “custom-made” pluripotent cells, ideal for patient-specific disease models, alongside their possible applications in regenerative medicine and reproduction, has drawn a lot of attention to the field with numbers of iPSC studies published growing exponentially. IPSCs have now been generated for a wide variety of species, including but not limited to, mouse, human, primate, wild felines, bovines, equines, birds and rodents, some of which still lack well-established embryonic stem cell lines. The paucity of robust characterization of some of these iPSC lines as well as the residual expression of transgenes involved in the reprogramming process still hampers the use of such cells in species preservation or medical research, underscoring the requirement for further investigations. Here, we provide an extensive overview of iPSC generated from a broad range of animal species including their potential applications and limitations.

Use of a Sendai virus-based vector for effcient transduction of pinniped fbroblasts

Generation of induced pluripotent stem (iPS) cells expanded possibilities of pluripotency and early development studies. Generation of order Carnivora iPS cells from dog (Canis lupus familiaris), snow leopard (Panthera uncia), and American mink (Neovison vison) was previously reported. The aim of the current study was to examine conditions of pinniped fbroblast reprogramming. Pinnipeds are representatives of the suborder Caniformia sharing conservative genomes. There are several ways to deliver reprogramming transcription factors: RNA, proteins, plasmids, viral vectors etc. The most effective delivery systems for mouse and human cells are based on viral vectors. We compared a lentiviral vector which integrates into the genome and a Sendai virus­based vector, CytoTune EmGFP Sendai Fluorescence Reporter. The main advantage of Sendai virus­based vectors is that they do not integrate into the genome. We performed delivery of genetic constructions carrying fluorescent proteins to fbroblasts of seven Pinnipeds: northern fur seal (Callorhinus ursinus), Steller sea lion (Eumetopias jubatus), walrus (Odobenus rosmarus), bearded seal (Erignathus barbatus), Baikal seal (Pusa sibirica), ringed seal (Phoca hispida), and spotted seal (Phoca largha). We also transduced American mink (N. vison), human (Homo sapiens), and mouse (Mus musculus) fbroblasts as a control. We showed that the Sendai virus­based transduction system provides transgene expression one­two orders of magnitude higher than the lentiviral system at a comparable multiplicity of infection. Also, transgene expression after Sendai virus­based transduction is quite stable and changes only slightly at day four compared to day two. These data allow us to suggest that Sendai virus­based vectors are preferable for generation of Pinniped iPS cells.