Generation of induced pluripotent stem cells from adult rhesus monkey fibroblasts

Monkey hybrid stem cells develop cellular features of Huntington's disease

Background

Pluripotent stem cells that are capable of differentiating into different cell types and develop robust hallmark cellular features are useful tools for clarifying the impact of developmental events on neurodegenerative diseases such as Huntington's disease. Additionally, a Huntington's cell model that develops robust pathological features of Huntington's disease would be valuable for drug discovery research.

Results

To test this hypothesis, a pluripotent Huntington's disease monkey hybrid cell line (TrES1) was established from a tetraploid Huntington's disease monkey blastocyst generated by the fusion of transgenic Huntington's monkey skin fibroblast and a wild-type non-transgenic monkey oocyte. The TrES1 developed key Huntington's disease cellular pathological features that paralleled neural development. It expressed mutant huntingtin and stem cell markers, was capable of differentiating to neural cells, and developed teratoma in severely compromised immune deficient (SCID) mice. Interestingly, the expression of mutant htt, the accumulation of oligomeric mutant htt and the formation of intranuclear inclusions paralleled neural development in vitro , and even mutant htt was ubiquitously expressed. This suggests the development of Huntington's disease cellular features is influenced by neural developmental events.

Conclusions

Huntington's disease cellular features is influenced by neural developmental events. These results are the first to demonstrate that a pluripotent stem cell line is able to mimic Huntington's disease progression that parallels neural development, which could be a useful cell model for investigating the developmental impact on Huntington's disease pathogenesis.

Human embryonic stem cells and genomic instability

Owing to their original properties, pluripotent human embryonic stem cells (hESCs) and their progenies are highly valuable not only for regenerative medicine, but also as tools to study development and pathologies or as cellular substrates to screen and test new drugs. However, ensuring their genomic integrity is one important prerequisite for both research and therapeutic applications. Until recently, several studies about the genomic stability of cultured hESCs had described chromosomal or else large genomic alterations detectable with conventional karyotypic methods. In the past year, several laboratories have reported many small genomic alterations, in the megabase-sized range, using more sensitive karyotyping methods, showing that hESCs are prone to acquire focal genomic abnormalities in culture. As these alterations were found to be nonrandom, these findings strongly advocate for high-resolution monitoring of human pluripotent stem cell lines, especially when intended to be used for clinical applications.

The mighty mice prove pluripotency for iPSCs

By injecting induced pluripotent stem cells (iPSCs) into tetraploid blastocysts to generate live pups, two groups in China demonstrated that the injected cells are as pluripotent as embryonic stem cells, i.e. capable of giving rise to every cell in the newborn mice. This achievement validates iPS technology for regenerative medicine.

Are induced pluripotent stem cells the future of cell-based regenerative therapies for spinal cord injury?

Despite advances in medical and surgical care, current clinical therapies for spinal cord injury (SCI) are limited. During the last two decades, the search for new therapies has been revolutionized by the discovery of stem cells, inspiring scientists and clinicians to search for stem cell-based reparative approaches for many disorders, including neurotrauma. Cell-based therapies using embryonic and adult stem cells in animal models of these disorders have provided positive outcome results. However, the availability of clinically suitable cell sources for human application has been hindered by both technical and ethical issues. The recent discovery of induced pluripotent stem (iPS) cells holds the potential to revolutionize the field of regenerative medicine by offering the option of autologous transplantation, thus eliminating the issue of host rejection. Herein, we will provide the rationale for the use of iPS cells in SCI therapies. In this review, we will evaluate the recent advancements in the field of iPS cells including their capacity for differentiation toward neural lineages that may allow iPS cells transplantation in cell-based therapy for spinal cord repair.

Generation of functional hepatocytes from mouse induced pluripotent stem cells

Induced pluripotent stem cells are derived from somatic cells by forced expression of several transcriptional factors. Induced pluripotent stem cells resemble embryonic stem cells in many aspects, such as the expression of certain stem cell markers, chromatin methylation patterns, embryoid body formation and teratoma formation. Therefore, induced pluripotent stem cells provide a powerful tool for study of developmental biology and unlimited resources for transplantation therapy. Here we reported the successful induction of mouse induced pluripotent stem cells and a simple and efficient process for generation of functional hepatocytes from mouse induced pluripotent stem cells by sequential addition of inducing factors. These induced pluripotent stem cell-derived hepatocytes, just as mouse embryonic stem cell-derived hepatocytes, expressed hepatic lineage markers including CK7, CK8, CK18, CK19, alpha-fetoprotein, albumin, Cyp7a1, and exhibited functional hepatic characteristics, including glycogen storage, indocyanine green (ICG) uptake and release, low-density lipoprotein (LDL) uptake and urea secretion. Although we observed some variations in the efficiency of hepatic differentiation between induced pluripotent stem cells and common mouse embryonic stem cell lines, our results indicate that mouse induced pluripotent stem cells can efficiently differentiate into functional hepatocytes in vitro, which may be helpful for the study of liver development and regenerative medicine.

Genesis of myocardial repair with cardiac progenitor cells and tissue engineering

BACKGROUND

There is mounting evidence to suggest that the heart has regenerative potential in the event of myocardial injury. Recent studies have shown that a resident population of cardiac progenitor cells (CPCs) in the heart contains both vasculogenic and myogenic lineages. CPCs are able to migrate to the site of injury in the heart for participation in the healing process. The resident CPCs in the heart may also be activated through outside pharmacological intervention to promote their participation in the intrinsic repair process. In the light of these characteristics, CPCs provide a logical source for the heart cell therapy. During the regenerative cardiac process, stem cell niches (a specialised environment surrounding stem cells) provide crucial support needed for their maintenance.

DISCUSSION

Compromised niche function may lead to the selection of stem cells that no longer depend on self-renewal factors produced by its environment. The objective of stem cell transplantation associated with tissue-engineered approaches is to create a new modality in the treatment of heart failure. The use of efficient scaffolds will aid to re-establish a favourable microenvironment for stem cell survival, multiplication, differentiation and function. Cardiac tissue engineering using natural and/or synthetic materials in this regard provides a novel possibility in cardiovascular therapeutics.

Induced pluripotent stem (iPS) cells: an up-to-the-minute review

Recent advances in nuclear reprogramming technology allow the transformation of terminally differentiated, adult cells into induced pluripotent stem cells whose phenotype is indistinguishable from that of embryonic stem cells. This leap forward enables the creation of patient-specific pluripotent cell lines that carry disease genotypes. These cell lines could be used both as in vitro models for the study of disease and as potential sources of material for cell replacement therapy. Ultimately, a greater understanding of the process by which cellular identity is shaped and altered may allow the generation of particular cell types for the treatment of degenerative disease.

[Induced pluripotent stem cells (iPS cells)]

There is less than three years, the reprogramming of adult cells in induced pluripotent stem cells (iPS cells) has been added to the techniques producing natural or manufactured embryonic cells. Easier to obtain than these last, the human iPS cells are ethically irreproachable. They allow the study of many disorders at the cellular level and put at the disposal of pharmacologists a material of an exceptional interest. The improvement of the quality of their reprogramming is the object of active search all over the world. It is not utopian to hope that the iPS cells will quickly take a choice place in human cellular therapy.

Genetic basis of inherited macular dystrophies and implications for stem cell therapy

Untreatable hereditary macular dystrophy (HMD) presents a major burden to society in terms of the resulting patient disability and the cost to the healthcare provision system. HMD results in central vision loss in humans sufficiently severe for blind registration, and key issues in the development of therapeutic strategies to target these conditions are greater understanding of the causes of photoreceptor loss and the development of restorative procedures. More effective and precise analytical techniques coupled to the development of transgenic models of disease have led to a prolific growth in the identification and our understanding of the genetic mutations that underly HMD. Recent successes in driving differentiation of pluripotent cells towards specific somatic lineages have led to the development of more efficient protocols that can yield enriched populations of a desired phenotype. Retinal pigmented epithelial cells and photoreceptors derived from these are some of the most promising cells that may soon be used in the treatment of specific HMD, especially since rapid developments in the field of induced pluripotency have now set the stage for the production of patient-derived stem cells that overcome the ethical and methodological issues surrounding the use of embryonic derivatives. In this review we highlight a selection of HMD which appear suitable candidates for combinatorial restorative therapy, focusing specifically on where those photoreceptor loss occurs. This technology, along with increased genetic screening, opens up an entirely new pathway to restore vision in patients affected by HMD.

Genome 10K: a proposal to obtain whole-genome sequence for 10,000 vertebrate species

The human genome project has been recently complemented by whole-genome assessment sequence of 32 mammals and 24 nonmammalian vertebrate species suitable for comparative genomic analyses. Here we anticipate a precipitous drop in costs and increase in sequencing efficiency, with concomitant development of improved annotation technology and, therefore, propose to create a collection of tissue and DNA specimens for 10,000 vertebrate species specifically designated for whole-genome sequencing in the very near future. For this purpose, we, the Genome 10K Community of Scientists (G10KCOS), will assemble and allocate a biospecimen collection of some 16,203 representative vertebrate species spanning evolutionary diversity across living mammals, birds, nonavian reptiles, amphibians, and fishes (ca. 60,000 living species). In this proposal, we present precise counts for these 16,203 individual species with specimens presently tagged and stipulated for DNA sequencing by the G10KCOS. DNA sequencing has ushered in a new era of investigation in the biological sciences, allowing us to embark for the first time on a truly comprehensive study of vertebrate evolution, the results of which will touch nearly every aspect of vertebrate biological enquiry.

Sox2 is dispensable for the reprogramming of melanocytes and melanoma cells into induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) have been derived at low frequencies from different cell types through ectopic expression of the transcription factors Oct4 and Sox2, combined with either Klf4 and c-Myc or Lin28 and Nanog. In order to generate iPSCs more effectively, it will be crucial to identify somatic cells that are easily accessible and possibly require fewer factors for conversion into iPSCs. Here, we show that both human and mouse melanocytes give rise to iPSCs at higher efficiencies than fibroblasts. Moreover, we demonstrate that a mouse malignant melanoma cell line, which has previously been reprogrammed into embryonic stem cells by nuclear transfer, remains equally amenable to reprogramming into iPSCs by these transcription factors. In contrast to skin fibroblasts, melanocytes and melanoma cells did not require ectopic Sox2 expression for conversion into iPSCs. iPSC lines from melanocytic cells expressed pluripotency markers, formed teratomas and contributed to viable chimeric mice with germ line transmission. Our results identify skin melanocytes as an alternative source for deriving patient-specific iPSCs at increased efficiency and with fewer genetic elements. In addition, our results suggest that cancer cells remain susceptible to transcription factor-mediated reprogramming, which should facilitate the study of epigenetic changes in human cancer.

iPS cells produce viable mice through tetraploid complementation

Since the initial description of induced pluripotent stem (iPS) cells created by forced expression of four transcription factors in mouse fibroblasts, the technique has been used to generate embryonic stem (ES)-cell-like pluripotent cells from a variety of cell types in other species, including primates and rat. It has become a popular means to reprogram somatic genomes into an embryonic-like pluripotent state, and a preferred alternative to somatic-cell nuclear transfer and somatic-cell fusion with ES cells. However, iPS cell reprogramming remains slow and inefficient. Notably, no live animals have been produced by the most stringent tetraploid complementation assay, indicative of a failure to create fully pluripotent cells. Here we report the generation of several iPS cell lines that are capable of generating viable, fertile live-born progeny by tetraploid complementation. These iPS cells maintain a pluripotent potential that is very close to ES cells generated from in vivo or nuclear transfer embryos. We demonstrate the practicality of using iPS cells as useful tools for the characterization of cellular reprogramming and developmental potency, and confirm that iPS cells can attain true pluripotency that is similar to that of ES cells.

Cell-based therapies for Parkinson's disease: past, present, and future

Parkinson's disease (PD) researchers have pioneered the use of cell-based therapies (CBTs) in the central nervous system. CBTs for PD were originally envisioned as a way to replace the dopaminergic nigral neurons lost with the disease. Several sources of catecholaminergic cells, including autografts of adrenal medulla and allografts or xenografts of mesencephalic fetal tissue, were successfully assessed in animal models, but their clinical translation has yielded poor results and much controversy. Recent breakthroughs on cell biology are helping to develop novel cell lines that could be used for regenerative medicine. Their future successful clinical application depends on identifying and solving the problems encountered in previous CBTs trials. In this review, we critically analyze past CBTs' clinical translation, the impact of the host in graft survival, and the role of preclinical studies and emerging new cell lines. We propose that the prediction of clinical results from preclinical studies requires experimental designs that allow blind data acquisition and statistical analysis, assessment of the therapy in models that parallel clinical conditions, looking for sources of complications or side effects, and limiting optimism bias when reporting outcomes.

Differentiation stage determines potential of hematopoietic cells for reprogramming into induced pluripotent stem cells

The reprogramming of somatic cells into induced pluripotent stem (iPS) cells upon overexpression of the transcription factors Oct4, Sox2, Klf4 and cMyc is inefficient. It has been assumed that the somatic differentiation state provides a barrier for efficient reprogramming; however, direct evidence for this notion is lacking. Here, we tested the potential of mouse hematopoietic cells at different stages of differentiation to be reprogrammed into iPS cells. We show that hematopoietic stem and progenitor cells give rise to iPS cells up to 300 times more efficiently than terminally differentiated B and T cells do, yielding reprogramming efficiencies of up to 28%. Our data provide evidence that the differentiation stage of the starting cell has a critical influence on the efficiency of reprogramming into iPS cells. Moreover, we identify hematopoietic progenitors as an attractive cell type for applications of iPS cell technology in research and therapy.

Current progress and prospects of induced pluripotent stem cells

Induced pluripotent stem (iPS) cells are derived from somatic cells by ectopic expression of few transcription factors. Like embryonic stem (ES) cells, iPS cells are able to self-renew indefinitely and to differentiate into all types of cells in the body. iPS cells hold great promise for regenerative medicine, because iPS cells circumvent not only immunological rejection but also ethical issues. Since the first report on the derivation of iPS cells in 2006, many laboratories all over the world started research on iPS cells and have made significant progress. This paper reviews recent progress in iPS cell research, including the methods to generate iPS cells, the molecular mechanism of reprogramming in the formation of iPS cells, and the potential applications of iPS cells in cell replacement therapy. Current problems that need to be addressed and the prospects for iPS research are also discussed.

Molecules that promote or enhance reprogramming of somatic cells to induced pluripotent stem cells

Reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) can be achieved by viral-mediated transduction of defined transcription factors. Moving toward the eventual goal of clinical application, it is necessary to overcome limitations such as low reprogramming efficiency and genomic alterations due to viral integration. Here, we review recent progress made in the usage of genetic factors, chemical inhibitors, and signaling molecules that can either replace core reprogramming factors or enhance reprogramming efficiency. Current iPSC studies will provide a paradigm for the combinatorial use of genetic factors and chemicals for the broader applications to alter cellular states of potency.

Induced pluripotent stem cells and the stability of the differentiated state

For much of the last century, the differentiated state that characterizes the many cell types of an adult organism was thought to be stable and abrogated only in rare instances by transdifferentiation, metaplasia or cancer. This stability was thought to reside in the autoregulatory molecular circuitry that exists between the cytoplasm and the nucleus, a status quo that could be disrupted during somatic cell nuclear transfer, to reprogramme cells to a pluripotent state. Pioneering work in the 1980s showed that transdifferentiation of cell lineages could be induced by the addition of transcription factors. However, these conversions were usually confined to cell types from the same germ layer, and proof of conversion was difficult to obtain. This deficiency has now been overturned by demonstrations that exogenously added transcription factors can convert differentiated cell types into embryonic-like induced pluripotent stem cells. Here, we highlight the recent progress, and the implications of this work for our understanding of the relationship between the pluripotent and more differentiated cell states.

Derivation of induced pluripotent stem cells from pig somatic cells

For reasons that are unclear the production of embryonic stem cells from ungulates has proved elusive. Here, we describe induced pluripotent stem cells (iPSC) derived from porcine fetal fibroblasts by lentiviral transduction of 4 human (h) genes, hOCT4, hSOX2, hKLF4, and hc-MYC, the combination commonly used to create iPSC in mouse and human. Cells were cultured on irradiated mouse embryonic fibroblasts (MEF) and in medium supplemented with knockout serum replacement and FGF2. Compact colonies of alkaline phosphatase-positive cells emerged after approximately 22 days, providing an overall reprogramming efficiency of approximately 0.1%. The cells expressed porcine OCT4, NANOG, and SOX2 and had high telomerase activity, but also continued to express the 4 human transgenes. Unlike human ESC, the porcine iPSC (piPSC) were positive for SSEA-1, but negative for SSEA-3 and -4. Transcriptional profiling on Affymetrix (porcine) microarrays and real time RT-PCR supported the conclusion that reprogramming to pluripotency was complete. One cell line, ID6, had a normal karyotype, a cell doubling time of approximately 17 h, and has been maintained through >220 doublings. The ID6 line formed embryoid bodies, expressing genes representing all 3 germ layers when cultured under differentiating conditions, and teratomas containing tissues of ectoderm, mesoderm, and endoderm origin in nude mice. We conclude that porcine somatic cells can be reprogrammed to form piPSC. Such cell lines derived from individual animals could provide a means for testing the safety and efficacy of stem cell-derived tissue grafts when returned to the same pigs at a later age.

Generation of pig induced pluripotent stem cells with a drug-inducible system

Domesticated ungulate pluripotent embryonic stem (ES) cell lines would be useful for generating precise gene-modified animals. To date, many efforts have been made to establish domesticated ungulate pluripotent ES cells from early embryos without success. Here, we report the generation of porcine-induced pluripotent stem (iPS) cells using drug-inducible expression of defined factors. We showed that porcine iPS cells expressed alkaline phosphatase, SSEA3, SSEA4, Tra-1-60, Tra-1-81, Oct3/4, Nanog, Sox2, Rex1 and CDH1. Pig iPS cells expressed high levels of telomerase activity and showed normal karyotypes. These cells could differentiate into cell types of all three germ layers in vitro and in teratomas. Our study reveals properties of porcine pluripotent stem cells that may facilitate the eventual establishment of porcine ES cells. Moreover, the porcine iPS cells produced may be directly useful for the generation of precise gene-modified pigs.

Generation of induced pluripotent stem cell lines from Tibetan miniature pig

Induced pluripotent stem cell (iPS) technology appears to be a general strategy to generate pluripotent stem cells from any given mammalian species. So far, iPS cells have been reported for mouse, human, rat, and monkey. These four species have also established embryonic stem cell (ESC) lines that serve as the gold standard for pluripotency comparisons. Attempts have been made to generate porcine ESC by various means without success. Here we report the successful generation of pluripotent stem cells from fibroblasts isolated from the Tibetan miniature pig using a modified iPS protocol. The resulting iPS cell lines more closely resemble human ESC than cells from other species, have normal karyotype, stain positive for alkaline phosphatase, express high levels of ESC-like markers (Nanog, Rex1, Lin28, and SSEA4), and can differentiate into teratomas composed of the three germ layers. Because porcine physiology closely resembles human, the iPS cells reported here provide an attractive model to study certain human diseases or assess therapeutic applications of iPS in a large animal model.

A fresh look at iPS cells

The potential of induced pluripotent stem (iPS) cells is enormous, but many obstacles remain before their medical and pharmaceutical applications can be fully realized.

Upping the ante: recent advances in direct reprogramming

The concept of reversing the characteristics of differentiated tissues to pluripotency through reprogramming was introduced over 50 years ago in the first somatic cell nuclear transfer (SCNT) experiments. More recently, direct reprogramming of differentiated somatic cells by gene transfer of a small number of defined transcription factors has been shown to yield cells that are indistinguishable from inner cell mass-derived embryonic stem (ES) cells. These cells, termed induced pluripotent stem (iPS) cells, offer exciting possibilities for studying mechanism of pluripotency, establishing models for disease-specific investigations, and enabling future applications in regenerative medicine. In this review, we discuss the basic foundation of reestablishing pluripotency and recent progress toward enhancing the efficiency and safety of the process through optimization of the reprogramming factor combination, identification of small molecules that augment efficiency, and assessment of distinct target cells in reprogramming efficiency. We also highlight recent advances that eliminate stable genetic modification from the reprogramming process, and summarize preclinical models that provide proof-of-concept for ES/iPS cell-based regenerative medicine.

Guidelines and techniques for the generation of induced pluripotent stem cells

Direct reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) provides an invaluable resource for regenerative medicine, enabling the generation of patient-specific cells of any lineage without the use of embryonic material. A variety of methods exist for iPSC derivation, all reliant upon manipulation of a select group of transcription factors. We compare the currently reported protocols, identify essential steps common to these methods, and suggest minimal criteria for defining fully reprogrammed cells. In addition, specific procedures aimed to optimize reproducible iPSC derivation are presented, with an emphasis on standardization of certain parameters for accurate comparison between independent experiments.

Preclinical assessment of stem cell therapies for neurological diseases

Stem cells, as subjects of study for use in treating neurological diseases, are envisioned as a replacement for lost neurons and glia, a means of trophic support, a therapeutic vehicle, and, more recently, a tool for in vitro modeling to understand disease and to screen and personalize treatments. In this review we analyze the requirements of stem cell-based therapy for clinical translation, advances in stem cell research toward clinical application for neurological disorders, and different animal models used for analysis of these potential therapies. We focus on Parkinson's disease (typically defined by the progressive loss of dopaminergic nigral neurons), stroke (neurodegeneration associated with decreased blood perfusion in the brain), and multiple sclerosis (an autoimmune disorder that generates demyelination, axonal damage, astrocytic scarring, and neurodegeneration in the brain and spinal cord). We chose these disorders for their diversity and the number of people affected by them. An additional important consideration was the availability of multiple animal models in which to test stem cell applications for these diseases. We also discuss the relationship between the limited number of systematic stem cell studies performed in animals, in particular nonhuman primates and the delayed progress in advancing stem cell therapies to clinical success.

Rats, cats, and elephants, but still no unicorn: induced pluripotent stem cells from new species

Two independent studies in this issue of Cell Stem Cell (Liao et al., 2009; Li et al., 2009) derive rat induced pluripotent stem cells (iPSCs). In one report, the method used results in rat and human iPSCs that exhibit phenotypic traits similar to mouse embryonic stem cells.