Project description:Ectopic expression of four transcription factors including Oct4, Sox2, Klf4 and c-Myc in differentiated fibroblast cells could reset the cell fate of fibroblast cells to pluripotent state. Subsequently, fully pluripotency of these so-called induced pluripotent stem cells (iPSCs) has been demonstrated as viable mice could be generated autonomously from iPS cells through tetraploid blastocyst complementation. Moreover, the generation of human and patient-specific iPS cells have raised the possibility of utilizing iPS cells clinically. However, the utilization of c-Myc in iPS cells induction greatly increased the incidence of tumorigenecity in the iPS-chimeric mice and also might hinder the clinical application of human iPS cells in the future. Fortunately, c-Myc has been recently found dispensable for iPS induction even though the iPS induction efficiency is greatly reduced in the absence of c-Myc. However, it remains unknown if these three factors-induced iPS cells are fully pluripotent. In the present study, we have successfully demonstrated that 3-factor iPS cells could also be fully pluripotent as viable mice could be generated from 3-factor iPS cells autonomously via tetraploid complementation and moreover, our data indicated that the pluripotency regulatory mechanism in 3-factor iPS cells might be distinct from 4-factor iPS cells.
Project description:Hepatocyte-like cells differentiated from human iPS cells are expected to be utilized in pharmaceutical research and regenerative medicine. Recently, various culture methods for human iPS cell maintenance have been developed. However, it is not well known whether human iPS cell maintenance method affects hepatic differentiation potency. In this study, we cultured human iPS cells using four maintenance methods: ReproStem medium with feeder cells (mouse embryonic fibroblasts), AK02N medium with iMatrix-511 (E8 fragments of laminin511), Essential 8 medium with Vitronectin N (N-terminal domain of vitronectin), TeSR-E8 medium with Vitronectin XF (xeno-free vitronectin). Then, these human iPS cells were differentiated into the hepatocyte-like cells. Interestingly, the gene expression levels of definitive endoderm markers in the definitive endoderm cells generated from human iPS cells cultured with ReproStem or TeSR-E8 medium were higher than those in other groups. The gene expression level of foregut marker, HHEX, in the definitive endoderm cells generated from human iPS cells cultured with ReproStem medium was higher than that in other groups. Consistently, the expression levels of hepatocyte markers, albumin and urea secretion capacity, and CYP3A4 activity in the hepatocyte-like cells generated from human iPS cells cultured with ReproStem medium were higher than those in other groups. Our data indicated that the most suitable human iPS cell maintenance method for efficient hepatic differentiation was the on-feeder method which uses mouse embryonic fibroblasts, but not feeder-free methods. In conclusion, human iPS cell maintenance method largely affects hepatic differentiation potency.
Project description:Ectopic expression of four transcription factors including Oct4, Sox2, Klf4 and c-Myc in differentiated fibroblast cells could reset the cell fate of fibroblast cells to pluripotent state. Subsequently, fully pluripotency of these so-called induced pluripotent stem cells (iPSCs) has been demonstrated as viable mice could be generated autonomously from iPS cells through tetraploid blastocyst complementation. Moreover, the generation of human and patient-specific iPS cells have raised the possibility of utilizing iPS cells clinically. However, the utilization of c-Myc in iPS cells induction greatly increased the incidence of tumorigenecity in the iPS-chimeric mice and also might hinder the clinical application of human iPS cells in the future. Fortunately, c-Myc has been recently found dispensable for iPS induction even though the iPS induction efficiency is greatly reduced in the absence of c-Myc. However, it remains unknown if these three factors-induced iPS cells are fully pluripotent. In the present study, we have successfully demonstrated that 3-factor iPS cells could also be fully pluripotent as viable mice could be generated from 3-factor iPS cells autonomously via tetraploid complementation and moreover, our data indicated that the pluripotency regulatory mechanism in 3-factor iPS cells might be distinct from 4-factor iPS cells. We compared the gene expression profile of iPS cells with and without the tetraploid embryo complementation competence. Three biological repeats were included for each line.
Project description:It has been shown that DNA demethylation has a pivotal role in the generation of induced pluripotent stem (iPS) cells. However, the underlying mechanism is still unclear. Previous reports indicated that activation-induced cytidine deaminase (Aid) is involved in DNA demethylation in several developmental processes and cell fusion-mediated reprogramming. Based on the reports, we hypothesized that Aid may be involved in DNA demethylation during the iPS cell generation. In this study, we examined the function of Aid in iPS cell generation using Aid knockout (Aid-/-) mice expressing a GFP reporter under the control of a pluripotent stem cell marker, Nanog. By the introduction of Oct3/4, Sox2, Klf4 and c-Myc, Nanog-GFP positive iPS cells could be generated from the fibroblasts and primary B cells of Aid-/- mice. The Aid-/- iPS cells showed normal proliferation and gave rise to chimeras, indicating their capacity for self-renewal and pluripotency. The comprehensive DNA methylation analysis by MBD-sequening demonstrated that there were only a few differences between Aid+/+ and Aid-/- iPS cells. Aid+/+ and Aid-/- iPS colonies were generated from Aid+/+ and Aid-/- MEFs and picked up mechanically. The clones were passaged four times on feeder cells and two times on gelatin-coated dishes to exclude the contamination of feeder cells. Subsequently, the genome was isolated. Four Aid+/+ iPS cell clones and four Aid-/- iPS cell clones were compared. To confirm the validity of MBD-sequencing, four Aid+/+ iPS cell clones were compared with three ES cell clones or three Aid+/+ MEFs.
Project description:Ten-eleven translocation (TET) family enzymes can convert 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC) in DNA and have been proposed as potential DNA demethylase candidates1. Evidences from recent studies indicated that Tet1 is predominantly expressed in ES cells and plays dual functions in promoting transcription of pluripotency genes and as well as participating in the repression of developmental genes by facilitating recruitment of PRC21-5. These studies further raised the possibility that Tet1 might play a role in somatic cell reprogramming. Here, we provide evidence showing that Tet1 can substitute for pluripotent transcription factors in reprogramming differentiated somatic cells to pluripotent stem cells. Tet1 can replace any one of the four traditional transcription factors including Oct4, Sox2, Klf4 and c-Myc during somatic cell reprogramming. Subsequently, the chimeric mice with germline transmission capacity could be efficiently produced from all induced pluripotent stem (iPS) cell lines reprogrammed by OT (Oct4, Tet1), TSKM (Tet1, Sox2, Klf4, c-Myc), OTK, OTKM and OSTM combinations. Furthermore, the TSKM-reprogrammed iPS cells without using Oct4 could produce viable full-term iPS mice with normal fertility through tetraploid complementation and secondary iPS cells could be induced subsequently from the somatic cells retrieved from the iPS mice. Moreover, we demonstrated that conversion of 5mC into 5hmC in Nanog promoter occurred during reprogramming, which might account in part for the mechanism of Tet1 mediated reprogramming. To our knowledge, our study provides the first evidence demonstrating that DNA modifying enzyme Tet1 can replace the pluripotent transcription factors to reprogram differentiated somatic cells to iPS cells. Gene expression profile of iPS cells and ES cells were generated by Affymetrix Mouse Gene 1.0 ST Array. The Gene expression profile of ES cell R1 was used as control. Three biological repeats were included for each line.
Project description:Full pluripotency of induced pluripotent stem (iPS) cells has been determined as viable all-iPS mice can be generated through tetraploid complementation. Subsequently, activation of imprinted Dlk-Dio3 gene cluster has been suggested to correlate with the pluripotency of iPS cells1. However, evidence from recent studies has demonstrated that loss of imprinting at the Dlk-Dio3 locus did not correlate strictly with the reduced pluripotency of iPS cells. Therefore, it becomes indispensable to exploit other reliable molecular markers for evaluating the quality of iPS cells accurately. In the present study, we successfully utilize the sequential reprogramming approach and produce all-iPS mice to six generations using iPS cell lines derived from different cell lineages which contain the same proviral integration in the genome. By comparing the global gene expression and epigenetic modifications of both “tetra-on” and corresponding “tetra-off” iPS cell lines established from either mesenchymal or hematopoietic lineages through deep sequencing analysis of mRNA expression, small RNA profiling, histone modifications (H3K4m2, H3K4me3 and H3K27me3) and DNA methylation, very few differences are detected among all the iPS cell lines investigated. However, we find that two imprinted genes, disruption of which correlate with the reduced pluripotency of iPS cells. Therefore, our data not only provide the first demonstration that producing of all-iPS mice to six generations is feasible, but reveal that two imprinted regions can be served as pluripotency markers of iPS cells Examination of DNA methylation in 13 cell types
Project description:Full pluripotency of induced pluripotent stem (iPS) cells has been determined as viable all-iPS mice can be generated through tetraploid complementation. Subsequently, activation of imprinted Dlk-Dio3 gene cluster has been suggested to correlate with the pluripotency of iPS cells1. However, evidence from recent studies has demonstrated that loss of imprinting at the Dlk-Dio3 locus did not correlate strictly with the reduced pluripotency of iPS cells. Therefore, it becomes indispensable to exploit other reliable molecular markers for evaluating the quality of iPS cells accurately. In the present study, we successfully utilize the sequential reprogramming approach and produce all-iPS mice to six generations using iPS cell lines derived from different cell lineages which contain the same proviral integration in the genome. By comparing the global gene expression and epigenetic modifications of both “tetra-on” and corresponding “tetra-off” iPS cell lines established from either mesenchymal or hematopoietic lineages through deep sequencing analysis of mRNA expression, small RNA profiling, histone modifications (H3K4m2, H3K4me3 and H3K27me3) and DNA methylation, very few differences are detected among all the iPS cell lines investigated. However, we find that two imprinted genes, disruption of which correlate with the reduced pluripotency of iPS cells. Therefore, our data not only provide the first demonstration that producing of all-iPS mice to six generations is feasible, but reveal that two imprinted regions can be served as pluripotency markers of iPS cells Examination of 3 different histone modifications in 13 cell types
Project description:Human induced pluripotent stem (iPS) cells have the potential to establish a new field of promising regenerative medicine. Therefore, the safety and the efficiency of iPS-derived cells must be tested rigorously using appropriate animal models before human trials can commence. Here, we report the establishment of rabbit iPS cells as the first human-type iPS cells generated from a small laboratory animal species. Using lentiviral vectors, four human reprogramming genes (c-MYC, KLF4, SOX2 and OCT3/4) were introduced successfully into adult rabbit liver and stomach cells. The resulting rabbit iPS cells closely resembled human iPS cells; they formed flattened colonies with sharp edges and proliferated indefinitely in the presence of bFGF. They expressed the endogenous pluripotency markers c-MYC, KLF4, SOX2, OCT3/4 and NANOG, while the introduced human genes were completely silenced. Using in vitro differentiating conditions, rabbit iPS cells readily differentiated into ectoderm, mesoderm and endoderm. They also formed teratomas containing a variety of tissues of all three germ layers in immunodeficient mice. Thus, the rabbit iPS cells fulfilled all of the requirements for the acquisition of the fully reprogrammed state, showing high similarity to their embryonic stem (ES) cell counterparts we generated recently. However, their global gene expression analysis revealed a slight, but rigid difference between these two types of rabbit pluripotent stem cells. The rabbit model should enable us to compare iPS cells and ES cells under the same standardized conditions in evaluating their ultimate feasibility for pluripotent cell-based regenerative medicine in humans.
Project description:Pluripotent stem cells have the potential to differentiate in vitro in many, if not all, functional cell types. Induced pluripotent stem cells (iPS) have recently emerged as a reproducible model of pluripotent stem cells that can be generated from post-natal tissues. To understand this process at the transcriptome level, we generated iPS cell lines, partially reprogrammed cell lines and compared their transcriptome with that of the partental human foreskin fibroblasts and human embryonic stem cell lines. Four categories of samples, comprising human foreskin fibroblasts, fully reprogrammed iPS cell lines, partially reprogrammed iPS cell lines and human embryonic stem cell lines were compared using Significance Analysis of Microarrays (SAM). These data were also compared to a compendium of differentiated human samples and a pluripotency classifier was computed.