RESUMEN
The first successful reprogramming of differentiated cells to a pluripotent state was done by retroviral introduction of four transcription factors (Oct4, Sox2, Klf4, cMyc) by the group of Yamanaka in 2006. Since then, scientists all over the world have attempted various methods to avoid insertional mutagenesis, a major limitation of the retrovirus-based method, however no technique was found to completely avoid DNA integration. Recently, a non-viral mRNA-based approach, inherent to avoid genomic integration, was implemented to generate stem cell-like cells, yet, seventeen daily transfections were required, inducing substantial stress on the cells. In this work, we demonstrate successful activation of pluripotency-associated genes in mouse embryonic fibroblasts by means of cationic lipid-mediated introduction of mRNAs encoding the four factors. Moreover, our transfection protocol required maximally three transfections. Up-regulation of the transfected factors as well as Nanog and SSEA-1, typical mouse pluripotency markers, was detected already after the first transfection. Nuclear localization of the introduced factors was confirmed. Positive alkaline phosphatase staining of cell clusters further confirmed the onset of the reprogramming process. In conclusion, the transfection method presented here holds great promise for safe generation of induced pluripotent stem cells of mouse origin.
Asunto(s)
Fibroblastos/citología , Células Madre Pluripotentes Inducidas/citología , ARN Mensajero/genética , Transfección/métodos , Fosfatasa Alcalina/metabolismo , Animales , Diferenciación Celular , Células Cultivadas , Reprogramación Celular , Fibroblastos/metabolismo , Regulación de la Expresión Génica , Células Madre Pluripotentes Inducidas/metabolismo , Factor 4 Similar a Kruppel , Factores de Transcripción de Tipo Kruppel/genética , Factores de Transcripción de Tipo Kruppel/metabolismo , Antígeno Lewis X/genética , Antígeno Lewis X/metabolismo , Ratones , Factor 3 de Transcripción de Unión a Octámeros/genética , Factor 3 de Transcripción de Unión a Octámeros/metabolismo , Proteínas Proto-Oncogénicas c-myc/genética , Proteínas Proto-Oncogénicas c-myc/metabolismo , ARN Mensajero/metabolismo , Factores de Transcripción SOXB1/genética , Factores de Transcripción SOXB1/metabolismo , Regulación hacia ArribaRESUMEN
Friedreich's ataxia is an inherited neurodegenerative disease caused by the reduced expression of the mitochondrially active protein frataxin. We have previously shown that mice with a hepatocyte-specific frataxin knockout (AlbFxn(-/-)) develop multiple hepatic tumors in later life. In the present study, hepatic carbohydrate metabolism in AlbFxn(-/-) mice at an early and late life stage was analyzed. In young (5-week-old) AlbFxn(-/-) mice hepatic ATP, glucose-6-phosphate and glycogen levels were found to be reduced by â¼74, 80 and 88%, respectively, when compared with control animals. This pronounced ATP, G6P and glycogen depletion in the livers of young mice reverted in older animals: while half of the mice die before 30 weeks of age, the other half reaches 17 months of age and exhibits glycogen, G6P and ATP levels similar to those in age-matched controls. A key event in this respect seems to be the up-regulation of GLUT1, the predominant glucose transporter in fetal liver parenchyma, which became evident in AlbFxn(-/-) mice being 5-12 weeks of age. The most significant histological findings in animals being 17 or 22 months of age were the appearance of multiple clear cell, mixed cell and basophilic foci throughout the liver parenchyma as well as the development of hepatocellular adenomas and carcinomas. The hepatocarcinogenic process in AlbFxn(-/-) mice shows remarkable differences regarding carbohydrate metabolism alterations when compared with all other chemically and virally driven liver cancer models described up to now.
Asunto(s)
Metabolismo de los Hidratos de Carbono , Proteínas de Unión a Hierro/genética , Neoplasias Hepáticas Experimentales/metabolismo , Proteínas Mitocondriales/genética , Adenosina Trifosfato/metabolismo , Animales , Proteínas Facilitadoras del Transporte de la Glucosa/metabolismo , Glucosa-6-Fosfato/metabolismo , Glucógeno/metabolismo , Glucógeno Sintasa , Glucógeno Sintasa Quinasa 3/metabolismo , Hepatocitos/metabolismo , Proteínas de Unión a Hierro/metabolismo , Hígado/enzimología , Hígado/metabolismo , Hígado/patología , Neoplasias Hepáticas Experimentales/etiología , Ratones , Ratones Noqueados , Mitocondrias/metabolismo , Proteínas Mitocondriales/metabolismo , FrataxinaRESUMEN
Somatic cells can be reprogrammed to induced pluripotent stem cells by over-expression of OCT4, SOX2, KLF4 and c-MYC (OSKM). With the aim of unveiling the early mechanisms underlying the induction of pluripotency, we have analyzed transcriptional profiles at 24, 48 and 72 hours post-transduction of OSKM into human foreskin fibroblasts. Experiments confirmed that upon viral transduction, the immediate response is innate immunity, which induces free radical generation, oxidative DNA damage, p53 activation, senescence, and apoptosis, ultimately leading to a reduction in the reprogramming efficiency. Conversely, nucleofection of OSKM plasmids does not elicit the same cellular stress, suggesting viral response as an early reprogramming roadblock. Additional initiation events include the activation of surface markers associated with pluripotency and the suppression of epithelial-to-mesenchymal transition. Furthermore, reconstruction of an OSKM interaction network highlights intermediate path nodes as candidates for improvement intervention. Overall, the results suggest three strategies to improve reprogramming efficiency employing: 1) anti-inflammatory modulation of innate immune response, 2) pre-selection of cells expressing pluripotency-associated surface antigens, 3) activation of specific interaction paths that amplify the pluripotency signal.
Asunto(s)
Reprogramación Celular/genética , Redes Reguladoras de Genes/genética , Factores de Transcripción de Tipo Kruppel/genética , Factor 3 de Transcripción de Unión a Octámeros/genética , Proteínas Proto-Oncogénicas c-myc/genética , Factores de Transcripción SOXB1/genética , Animales , Senescencia Celular/genética , Transición Epitelial-Mesenquimal/genética , Fibroblastos/metabolismo , Regulación de la Expresión Génica , Humanos , Factor 4 Similar a Kruppel , Factores de Transcripción de Tipo Kruppel/metabolismo , Masculino , Ratones , Modelos Biológicos , Factor 3 de Transcripción de Unión a Octámeros/metabolismo , Células Madre Pluripotentes/metabolismo , Proteínas Proto-Oncogénicas c-myc/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Retroviridae/genética , Factores de Transcripción SOXB1/metabolismo , Factores de Tiempo , Transcripción Genética , Transcriptoma , Transducción Genética , Transfección , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
Human amniotic fluid cells (AFCs) are routinely obtained for prenatal diagnostics procedures. Recently, it has been illustrated that these cells may also serve as a valuable model system to study developmental processes and for application in regenerative therapies. Cellular reprogramming is a means of assigning greater value to primary AFCs by inducing self-renewal and pluripotency and, thus, bypassing senescence. Here, we report the generation and characterization of human amniotic fluid-derived induced pluripotent stem cells (AFiPSCs) and demonstrate their ability to differentiate into the trophoblast lineage after stimulation with BMP2/BMP4. We further carried out comparative transcriptome analyses of primary human AFCs, AFiPSCs, fibroblast-derived iPSCs (FiPSCs) and embryonic stem cells (ESCs). This revealed that the expression of key senescence-associated genes are down-regulated upon the induction of pluripotency in primary AFCs (AFiPSCs). By defining distinct and overlapping gene expression patterns and deriving the LARGE (Lost, Acquired and Retained Gene Expression) Principle of Cellular Reprogramming, we could further highlight that AFiPSCs, FiPSCs and ESCs share a core self-renewal gene regulatory network driven by OCT4, SOX2 and NANOG. Nevertheless, these cell types are marked by distinct gene expression signatures. For example, expression of the transcription factors, SIX6, EGR2, PKNOX2, HOXD4, HOXD10, DLX5 and RAXL1, known to regulate developmental processes, are retained in AFiPSCs and FiPSCs. Surprisingly, expression of the self-renewal-associated gene PRDM14 or the developmental processes-regulating genes WNT3A and GSC are restricted to ESCs. Implications of this, with respect to the stability of the undifferentiated state and long-term differentiation potential of iPSCs, warrant further studies.
Asunto(s)
Líquido Amniótico/citología , Regulación de la Expresión Génica , Células Madre Pluripotentes/citología , Regulación hacia Abajo , HumanosRESUMEN
Human embryonic stem (ES) cells possess an enormous potential for applications in regenerative medicine. However, these cells have several inevitable hurdles limiting their clinical applications, such as transplant rejection and embryo destruction. A milestone recently achieved was the derivation of induced pluripotent stem (iPS) cells by over-expressing combinations of defined transcription factors, namely, OCT4, SOX2, NANOG, and LIN28 or OCT4, SOX2, KLF4, and c-MYC. Human iPS cells exhibit many characteristics identical to those of inner cell mass-derived ES cells. Here, we summarize the generation of human fibroblast-derived iPS cells and discuss the promises and limitations of their use. In addition, by utilising numerous published transcriptome datasets related to ES cells, fibroblast-derived iPS cells, partially induced pluripotent stem cells (PiPSC) and wild type fibroblasts, we reveal similarities (self-renewal signature) and differences (donor cell-type and PiPSC signatures) in genes and associated signaling pathways operative in the induction of pluripotency in fibroblasts. In particular, we highlight that induction of ground state pluripotency is also favoured by the inhibition of epithelial mesenchymal transition (EMT) and hence the induction of mesenchymal epithelial transition (MET). We anticipate that these findings might aid in the establishment of more efficient protocols for inducing pluripotency in somatic cells.