In vitro differentiation of reprogrammed murine somatic cells into hepatic precursor cells

Hypertonic pressure affects the pluripotency and self-renewal of mouse embryonic stem cells

As an important mechanical cue in the extracellular microenvironment, osmotic stress directly affects the proliferation, migration, and differentiation of cells. In this paper, we focused on the influence of hypertonic pressure on the colony morphology, stemness, and self-renew of mouse embryonic stem cells (mESCs). Our results showed that culture media with hypertonic pressure are more conducive to the maintenance of 3D colony morphology and pluripotency of mESCs after withdrawing the glycogen synthase kinase 3β (GSK3β) inhibitor CHIR99021 and the mitogen-activated protein kinase (MEK) inhibitor PD0325901 (hereinafter referred to as 2i) for 48 h. Furthermore, we revealed the microscopic mechanisms of the this finding: hypertonic pressure resulted in the depolymerization of F-actin cytoskeleton and limits Yes-associated protein (hereinafter referred to as YAP) transmission into the nucleus which play a vital role in the regulation of cell proliferation, and resulting in cell-cycle arrest at last.

Murine pluripotent stem cells with a homozygous knockout of Foxg1 show reduced differentiation towards cortical progenitors in vitro

Foxg1 is a transcription factor critical for the development of the mammalian telencephalon. Foxg1 controls the proliferation of dorsal telencephalon progenitors and the specification of the ventral telencephalon. Homozygous knockout of Foxg1 in mice leads to severe microcephaly, attributed to premature differentiation of telencephalic progenitors, mainly of cortical progenitors. Here, we analyzed the influence of a Foxg1 knockout on differentiation of murine pluripotent stem cells (mPSCs) in an in vitro model of neuronal development. Murine PSCs were prone to neuronal differentiation in embryoid body like culture with minimal medium conditions, based on the intrinsic default of PSCs to develop into cortical progenitors. Differences between Foxg1 wildtype (Foxg1^WT) and knockout (Foxg1^KO) mPSCs were analyzed. Several mPSC lines with homozygous mutations in Foxg1 were produced using the CRISPR/Cas9 system leading to loss of functional domains. Analysis of mRNA expression using quantitative Real-Time (q) PCR revealed that Foxg1^KO mPSCs expressed significantly less mRNA of Foxg1, Emx1, and VGlut1 compared to Foxg1^WT controls, indicating reduced differentiation towards dorsal telencephalic progenitors. However, the size of the derived EB-like structures did not differ between Foxg1^WT and Foxg1^KO mPSCs. These results show that loss of dorsal telencephalic progenitors can be detected using a simple and rapid differentiation protocol. This study is a first hint that this differentiation method can be used to analyze even extreme phenotypes that are lethal in vivo.

The Application of Human iPSCs in Neurological Diseases: From Bench to Bedside

In principle, induced pluripotent stem cells (iPSCs) are generated from somatic cells by reprogramming and gaining the capacity to self-renew indefinitely as well as the ability to differentiate into cells of different lineages. Human iPSCs have absolute advantages over human embryonic stem cells (ESCs) and animal models in disease modeling, drug screening, and cell replacement therapy. Since Takahashi and Yamanaka first described in 2007 that iPSCs can be generated from human adult somatic cells by retroviral transduction of the four transcription factors, Oct3/4, Sox2, Klf4, and c-Myc, disease specific iPSC lines have sprung up worldwide like bamboo shoots after a spring rain, making iPSC one of the hottest and fastest moving topics in modern science. The craze for iPSCs has spread throughout main branches of clinical medicine, covering neurology, hematology, cardiology, endocrinology, hepatology, ophthalmology, and so on. Here in this paper, we will focus on the clinical application of human iPSCs in disease modeling, drug screening, and cell replacement therapy for neurological diseases.

Two Effective Routes for Removing Lineage Restriction Roadblocks: From Somatic Cells to Hepatocytes

The conversion of somatic cells to hepatocytes has fundamentally re-shaped traditional concepts regarding the limited resources for hepatocyte therapy. With the various induced pluripotent stem cell (iPSC) generation routes, most somatic cells can be effectively directed to functional stem cells, and this strategy will supply enough pluripotent material to generate promising functional hepatocytes. However, the major challenges and potential applications of reprogrammed hepatocytes remain under investigation. In this review, we provide a summary of two effective routes including direct reprogramming and indirect reprogramming from somatic cells to hepatocytes and the general potential applications of the resulting hepatocytes. Through these approaches, we are striving toward the goal of achieving a robust, mature source of clinically relevant lineages.

MicroRNA-199a-5p inhibition enhances the liver repopulation ability of human embryonic stem cell-derived hepatic cells

BACKGROUND & AIMS

Current hepatic differentiation protocols for human embryonic stem cells (ESCs) require substantial improvements. MicroRNAs (miRNAs) have been reported to regulate hepatocyte cell fate during liver development, but their utility to improve hepatocyte differentiation from ESCs remains to be investigated. Therefore, our aim was to identify and to analyse hepatogenic miRNAs for their potential to improve hepatocyte differentiation from ESCs.

METHODS

By miRNA profiling and in vitro screening, we identified miR-199a-5p among several potential hepatogenic miRNAs. Transplantation studies of miR-199a-5p-inhibited hepatocyte-like cells (HLCs) in the liver of immunodeficient fumarylacetoacetate hydrolase knockout mice (Fah(-/-)/Rag2(-/-)/Il2rg(-/-)) were performed to assess their in vivo liver repopulation potential. For target determination, western blot and luciferase reporter assay were carried out.

RESULTS

miRNA profiling revealed 20 conserved candidate hepatogenic miRNAs. By miRNA screening, only miR-199a-5p inhibition in HLCs was found to be able to enhance the in vitro hepatic differentiation of mouse as well as human ESCs. miR-199a-5p inhibition in human ESCs-derived HLCs enhanced their engraftment and repopulation capacity in the liver of Fah(-/-)/Rag2(-/-)/Il2rg(-/-) mice. Furthermore, we identified SMARCA4 and MST1 as novel targets of miR-199a-5p that may contribute to the improved hepatocyte generation and in vivo liver repopulation.

CONCLUSIONS

Our findings demonstrate that miR-199a-5p inhibition in ES-derived HLCs leads to improved hepatocyte differentiation. Upon transplantation, HLCs were able to engraft and repopulate the liver of Fah(-/-)/Rag2(-/-)/Il2rg(-/-) mice. Thus, our findings suggest that miRNA modulation may serve as a promising approach to generate more mature HLCs from stem cell sources for the treatment of liver diseases.

Production of functional coagulation factor VIII from iPSCs using a lentiviral vector

The use of induced pluripotent stem cells (iPSCs) as an autologous cell source has shed new light on cell replacement therapy with respect to the treatment of numerous hereditary disorders. We focused on the use of iPSCs for cell-based therapy of haemophilia. We generated iPSCs from mesenchymal stem cells that had been isolated from C57BL/6 mice. The mouse iPSCs were generated through the induction of four transcription factor genes Oct3/4, Klf-4, Sox-2 and c-Myc. The derived iPSCs released functional coagulation factor VIII (FVIII) following transduction with a simian immunodeficiency virus vector. The subcutaneous transplantation of iPSCs expressing FVIII into nude mice resulted in teratoma formation, and significantly increased plasma levels of FVIII. The plasma concentration of FVIII was at levels appropriate for human therapy at 2-4 weeks post transplantation. Our data suggest that iPSCs could be an attractive and prospective autologous cell source for the production of coagulation factor, and that engineered iPSCs expressing coagulation factor might provide a cell-based therapeutic strategy appropriate for haemophilia.

Characterization of Oct4-GFP spermatogonial stem cell line and its application in the reprogramming studies

Establishment of mouse spermatogonial stem cell (SSC) culture systems offers a useful stem cell model for studies of proliferation and self-renewal of mammalian germline stem cells. In addition, spontaneous development of pluripotent stem cells from cultured SSCs emphasizes their possible applications in regenerative medicine as a substitute for embryonic stem cells (ESCs). These pluripotent stem cells termed multipotent germline stem cells (mGSCs) or germline-derived pluripotent stem cells (gPSCs) exhibit almost identical properties in terms of morphology and gene expression patterns to mouse ESCs (mESCs). In this study, to help understand mechanisms underlying reprogramming of SSCs into pluripotent stem cells, we established a culture system of SSCs derived from mice harboring green fluorescence protein (GFP) transgene whose expression is modulated by Oct4 regulatory sequences. Our results indicated that GFP intensity faithfully reflected cellular states upon reprogramming of SSCs or treatment with a selective extracellular signal-regulated kinase (ERK) inhibitor PD0325901. Moreover, in contrast to mESCs, regulation of Nanog expression did not appear to couple to the Oct4 level in SSCs. Further analysis of Oct4-GFP SSCs demonstrated that a posttranscriptional control of pluripotency marker genes such as Oct4 and Sox2 might play an important role as an inhibitory mechanism preventing the acquisition of pluripotency.

Hepatic differentiation of murine disease-specific induced pluripotent stem cells allows disease modelling in vitro

Direct reprogramming of somatic cells into pluripotent cells by retrovirus-mediated expression of OCT4, SOX2, KLF4, and C-MYC is a promising approach to derive disease-specific induced pluripotent stem cells (iPSCs). In this study, we focused on three murine models for metabolic liver disorders: the copper storage disorder Wilson's disease (toxic-milk mice), tyrosinemia type 1 (fumarylacetoacetate-hydrolase deficiency, FAH(-/-) mice), and alpha1-antitrypsin deficiency (PiZ mice). Colonies of iPSCs emerged 2-3 weeks after transduction of fibroblasts, prepared from each mouse strain, and were maintained as individual iPSC lines. RT-PCR and immunofluorescence analyses demonstrated the expression of endogenous pluripotency markers. Hepatic precursor cells could be derived from these disease-specific iPSCs applying an in vitro differentiation protocol and could be visualized after transduction of a lentiviral albumin-GFP reporter construct. Functional characterization of these cells allowed the recapitulation of the disease phenotype for further studies of underlying molecular mechanisms of the respective disease.

Efficient hematopoietic redifferentiation of induced pluripotent stem cells derived from primitive murine bone marrow cells

Heterogeneity among induced pluripotent stem cell (iPSC) lines with regard to their gene expression profile and differentiation potential has been described and at least partly linked to the tissue of origin. Here, we generated iPSCs from primitive [lineage negative (Lin(neg))] and nonadherent differentiated [lineage positive (Lin(pos))] bone marrow cells (BM-iPSC), and compared their differentiation potential to that of fibroblast-derived iPSCs (Fib-iPSC) and embryonic stem cells (ESC). In the undifferentiated state, individual iPSC clones but also ESCs proved remarkably similar when analyzed for alkaline phosphatase and SSEA-1 staining, endogenous expression of the pluripotency genes Nanog, Oct4, and Sox2, or global gene expression profiles. However, substantial differences between iPSC clones were observed after induction of differentiation, which became most obvious upon cytokine-mediated instruction toward the hematopoietic lineage. All 3 BM-iPSC lines derived from undifferentiated Lin(neg) cells yielded high proportions of cells expressing the hematopoietic differentiation marker CD41 and in 2 of these lines high proportions of CD41+/ CD45+ cells were detected. In contrast, little hematopoiesis-specific surface marker expression was detected in 4 Lin(pos) BM-iPSC and 3 Fib-iPSC lines. These results were corroborated by functional studies demonstrating robust colony outgrowth from hematopoietic progenitors in 2 of the Lin(neg) BM-iPSCs only. Thus, in conclusion, our data demonstrate efficient generation of iPSCs from primitive hematopoietic tissue as well as efficient hematopoietic redifferentiation for Lin(neg) BM-iPSC lines, thereby supporting the notion of an epigenetic memory in iPSCs.

Generation of healthy mice from gene-corrected disease-specific induced pluripotent stem cells

Using the murine model of tyrosinemia type 1 (fumarylacetoacetate hydrolase [FAH] deficiency; FAH^−/− mice) as a paradigm for orphan disorders, such as hereditary metabolic liver diseases, we evaluated fibroblast-derived FAH^−/−-induced pluripotent stem cells (iPS cells) as targets for gene correction in combination with the tetraploid embryo complementation method. First, after characterizing the FAH^−/− iPS cell lines, we aggregated FAH^−/−-iPS cells with tetraploid embryos and obtained entirely FAH^−/−-iPS cell–derived mice that were viable and exhibited the phenotype of the founding FAH^−/− mice. Then, we transduced FAH cDNA into the FAH^−/−-iPS cells using a third-generation lentiviral vector to generate gene-corrected iPS cells. We could not detect any chromosomal alterations in these cells by high-resolution array CGH analysis, and after their aggregation with tetraploid embryos, we obtained fully iPS cell–derived healthy mice with an astonishing high efficiency for full-term development of up to 63.3%. The gene correction was validated functionally by the long-term survival and expansion of FAH-positive cells of these mice after withdrawal of the rescuing drug NTBC (2-(2-nitro-4-fluoromethylbenzoyl)-1,3-cyclohexanedione). Furthermore, our results demonstrate that both a liver-specific promoter (transthyretin, TTR)-driven FAH transgene and a strong viral promoter (from spleen focus-forming virus, SFFV)-driven FAH transgene rescued the FAH-deficiency phenotypes in the mice derived from the respective gene-corrected iPS cells. In conclusion, our data demonstrate that a lentiviral gene repair strategy does not abrogate the full pluripotent potential of fibroblast-derived iPS cells, and genetic manipulation of iPS cells in combination with tetraploid embryo aggregation provides a practical and rapid approach to evaluate the efficacy of gene correction of human diseases in mouse models.

Pluripotent stem cells have unlimited self-renewing capability and the potential to differentiate into virtually all cell types of the body. Pluripotent stem cells are therefore of great interest for future cell-based therapies and are already in use today for studying diseases “in a dish” and screening for new drugs. After the seminal discovery that induced pluripotent stem cells (iPS cells) can be generated by the delivery of four transcription factors into non-pluripotent cells, a tremendous amount of enthusiasm arose about the idea that patient-derived pluripotent stem cells could be obtained and genetically corrected in order to develop customized therapies for regenerative medicine. Here, we present a mouse model of acute metabolic liver failure that fulfills such criteria. First, we demonstrated by stringent assays that disease-specific iPS cells exhibited full cellular and developmental potential and the iPS cell–derived mice reproduced the phenotypes of the founding FAH^−/− mice faithfully. Then, we genetically repaired the disease-specific iPS cells by lentiviral delivery of an intact gene copy, and we investigated the impact of this additional genetic manipulation on these cells. With our analyses, we ruled out major, and even minor, chromosomal aberrations in the gene-corrected iPS cells. Most importantly, we demonstrated that the gene-corrected cells maintained their full potential and we generated viable mice that were completely derived from these repaired cells via tetraploid complementation approach, and these mice were healthy, without any signs of the metabolic liver disease.

A novel Fbxo25 acts as an E3 ligase for destructing cardiac specific transcription factors

Alterations in ubiquitin-proteasome system (UPS) have been implicated in the etiology of human cardiovascular diseases. Skp1/Cul1/F-box (SCF) ubiquitin E3 ligase complex plays a pivotal role in ubiquitination of cardiac proteins. However, a specific ubiquitin E3 ligase responsible for the destruction of cardiac transcription factors such as Nkx2-5, Isl1, Mef2C, and Tbx5 remains elusive to date. Here, we show that a novel F-box containing Fbxo25 is cardiac-specific and acts as an ubiquitin E3 ligase for cardiac transcription factors. Fbxo25 expression was nuclei-specific in vitro and cardiomyocytes. Expression level of Fbxo25 was higher in a fetal heart than an adult. Moreover, Fbxo25 expression was increased along with those of cardiac-specific genes during cardiomyocyte development from ESCs. Fbxo25 expression facilitated protein degradation of Nkx2-5, Isl1, Hand1, and Mef2C. Especially, Fbxo25 ubiquitinated Nkx2-5, Isl1, and Hand1. Altogether, Fbxo25 acts as an ubiquitin E3 ligase to target cardiac transcription factors including Nkx2-5, Isl1, and Hand1, indicating that cardiac protein homeostasis through Fbxo25 has a pivotal impact on cardiac development.

The 22q11.2 microdeletion: fifteen years of insights into the genetic and neural complexity of psychiatric disorders

Over the last fifteen years it has become established that 22q11.2 deletion syndrome (22q11DS) is a true genetic risk factor for schizophrenia. Carriers of deletions in chromosome 22q11.2 develop schizophrenia at rate of 25-30% and such deletions account for as many as 1-2% of cases of sporadic schizophrenia in the general population. Access to a relatively homogeneous population of individuals that suffer from schizophrenia as the result of a shared etiological factor and the potential to generate etiologically valid mouse models provides an immense opportunity to better understand the pathobiology of this disease. In this review we survey the clinical literature associated with the 22q11.2 microdeletions with a focus on neuroanatomical changes. Then, we highlight results from work modeling this structural mutation in animals. The key biological pathways disrupted by the mutation are discussed and how these changes impact the structure and function of neural circuits is described.

Induced pluripotent stem cells (iPSCs): the emergence of a new champion in stem cell technology-driven biomedical applications

Pluripotent stem cells possess the unique property of differentiating into all other cell types of the human body. Further, the discovery of induced pluripotent stem cells (iPSCs) in 2006 has opened up new avenues in clinical medicine. In simple language, iPSCs are nothing but somatic cells reprogrammed genetically to exhibit pluripotent characteristics. This process utilizes retroviruses/lentiviruses/adenovirus/plasmids to incorporate candidate genes into somatic cells isolated from any part of the human body. It is also possible to develop disease-specific iPSCs which are most likely to revolutionize research in respect to the pathophysiology of most debilitating diseases, as these can be mimicked ex vivo in the laboratory. These models can also be used to study the safety and efficacy of known drugs or potential drug candidates for a particular diseased condition, limiting the need for animal studies and considerably reducing the time and money required to develop new drugs. Recently, functional neurons, cardiomyocytes, pancreatic islet cells, hepatocytes and retinal cells have been derived from human iPSCs, thus re-confirming the pluripotency and differentiation capacity of these cells. These findings further open up the possibility of using iPSCs in cell replacement therapy for various degenerative disorders. In this review we highlight the development of iPSCs by different methods, their biological characteristics and their prospective applications in regenerative medicine and drug screening. We further discuss some practical limitations pertaining to this technology and how they can be averted for the betterment of human life.

Histochemistry and cell biology: the annual review 2010

This review summarizes recent advances in histochemistry and cell biology which complement and extend our knowledge regarding various aspects of protein functions, cell and tissue biology, employing appropriate in vivo model systems in conjunction with established and novel approaches. In this context several non-expected results and discoveries were obtained which paved the way of research into new directions. Once the reader embarks on reading this review, it quickly becomes quite obvious that the studies contribute not only to a better understanding of fundamental biological processes but also provide use-oriented aspects that can be derived therefrom.

Decreased collagen types I and IV, laminin, CK-19 and α-SMA expression after bone marrow cell transplantation in rats with liver fibrosis

Bone marrow cells have frequently been tested in animal models of liver fibrosis to assess their role in hepatic regeneration. The mononuclear fraction of bone marrow cells is of particular interest, as many studies show that these cells may be beneficial to treat hepatic fibrosis. In this study, we used the bile duct ligation model to induce hepatic fibrosis in an irreversible manner, and rats were treated with bone marrow mononuclear (BMMN) cells after fibrosis was established. Analysis of collagen types I and IV, laminin and α-SMA showed a decreased expression of these proteins in fibrotic livers after 7 days of BMMN cell injection. Moreover, cytokeratin-19 analysis showed a reduction in bile ducts in the BMMN cell-treated group. These results were accompanied by ameliorated levels of hepatic enzymes GPT (Glutamic-pyruvic transaminase), GOT (glutamic-oxaloacetic transaminase) and alkaline phosphatase (AP). Therefore, we showed that BMMN cells decrease hepatic fibrosis by significantly reducing myofibroblast numbers and through reduction of the collagen and laminin-rich extracellular matrix of fibrotic septa and hepatic sinusoids.

Technical challenges in using human induced pluripotent stem cells to model disease

Reprogramming of human somatic cells uses readily accessible tissue, such as skin or blood, to generate embryonic-like induced pluripotent stem cells (iPSCs). This procedure has been applied to somatic cells from patients who are classified into a disease group, thus creating "disease-specific" iPSCs. Here, we examine the challenges and assumptions in creating a disease model from a single cell of the patient. Both the kinetics of disease onset and progression as well as the spatial localization of disease in the patient's body are challenges to disease modeling. New tools in genetic modification, reprogramming, biomaterials, and animal models can be used for addressing these challenges.

Induced pluripotent stem cells: characteristics and perspectives

The induction of pluripotency in somatic cells is widely considered as a major breakthrough in regenerative medicine, because this approach provides the basis for individualized stem cell-based therapies. Moreover, with respect to cell transplantation and tissue engineering, expertise from bioengineering to transplantation medicine is now meeting basic research of stem cell biology.In this chapter, we discuss techniques, potential and possible risks of induced pluripotent stem (iPS) cells in the light of needs for patient-derived pluripotent stem cells. To this end, we compare these cells with other sources of pluripotent cells and discuss the first encouraging results of iPS cells in pharmacological research, disease modeling and cell transplantation, providing fascinating perspectives for future developments in biotechnology and regenerative medicine.

Induced human pluripotent stem cells: promises and open questions

Adult cells have been reprogrammed into induced pluripotent stem (iPS) cells by introducing pluripotency-associated transcription factors. Here, we discuss recent advances and challenges of in vitro reprogramming and future prospects of iPS cells for their use in diagnosis and cell therapy. The generation of patient-specific iPS cells for clinical application requires alternative strategies, because genome-integrating viral vectors may cause insertional mutagenesis. Moreover, when suitable iPS cell lines will be available, efficient and selective differentiation protocols are needed to generate transplantable grafts. Finally, we point to the requirement of a regulatory framework necessary for the commercial use of iPS cells.