Melinda K Pirity

Hungarian Academy of Sciences, Budapeŝto, Budapest, Hungary

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Publications (34)105.45 Total impact

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    ABSTRACT: Human plexus injuries often include the avulsion of one or more ventral roots, resulting in debilitating conditions. In this study the effects of undifferentiated murine iPSCs on damaged motoneurons were investigated following avulsion of the lumbar 4 (L4) ventral root, an injury known to induce the death of the majority of the affected motoneurons. Avulsion and reimplantation of the L4 ventral root (AR procedure) was accompanied by the transplantation of murine iPSCs into the injured spinal cord segment in rats. Control animals underwent ventral root avulsion and reimplantation, but did not receive iPSCs. The grafted iPSCs induced an improved reinnervation of the reimplanted ventral root by the host motoneurons as compared with the controls (number of retrogradely labeled motoneurons: 503 ± 38 [AR+iPSCs group] vs 48 ± 6 [controls, AR group]). Morphological reinnervation resulted in a functional recovery, i.e. the grafted animals exhibited more motor units in their reinnervated hind limb muscles, which produced a greater force than that in the controls (50 ± 2.1% vs 11.9 ± 4.2% maximal tetanic tension [% ratio of operated/intact side]). Grafting of undifferentiated iPCSs downregulated the astroglial activation within the L4 segment. The grafted cells differentiated into neurons and astrocytes in the injured cord. The grafted iPSCs, host neurons and glia were found to produce the cytokines and neurotrophic factors MIP-1a, IL-10, GDNF and NT-4. These findings suggest that, following ventral root avulsion injury, iPSCs are able to induce motoneuron survival and regeneration through combined neurotrophic and cytokine modulatory effects. Copyright © 2015. Published by Elsevier Inc.
    Experimental Neurology 04/2015; 269. DOI:10.1016/j.expneurol.2015.03.031 · 4.62 Impact Factor
  • Izabella Bajusz, László Sipos, Melinda K Pirity
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    ABSTRACT: POLYCOMB group (PCG) proteins belong to the family of epigenetic regulators of genes playing important roles in differentiation and development. Mutants of PcG genes were isolated first in the fruit fly, Drosophila melanogaster, resulting in spectacular segmental transformations due to the ectopic expression of homeotic genes. Homologs of Drosophila PcG genes were also identified in plants and in vertebrates and subsequent experiments revealed the general role of PCG proteins in the maintenance of the repressed state of chromatin through cell divisions. The past decades of gene targeting experiments have allowed us to make significant strides towards understanding how the network of PCG proteins influences multiple aspects of cellular fate determination during development. Being involved in the transmission of specific expression profiles of different cell lineages, PCG proteins were found to control wide spectra of unrelated epigenetic processes in vertebrates, such as stem cell plasticity and renewal, genomic imprinting and inactivation of X-chromosome. PCG proteins also affect regulation of metabolic genes being important for switching programs between pluripotency and differentiation. Insight into the precise roles of PCG proteins in normal physiological processes has emerged from studies employing cell culture-based systems and genetically modified animals. Here we summarize the findings obtained from PcG mutant fruit flies and mice generated to date with a focus on PRC1 and PRC2 members altered by nucleotide substitutions resulting in specific alleles. We also include a compilation of lessons learned from these models about the in vivo functions of this complex protein family. With multiple knockout lines, sophisticated approaches to study the consequences of peculiar missense point mutations, and insights from complementary gain-of-function systems in hand, we are now in a unique position to significantly advance our understanding of the molecular basis of in vivo functions of PcG proteins. Copyright © 2015 Elsevier Inc. All rights reserved.
    Molecular Genetics and Metabolism 01/2015; 114(4). DOI:10.1016/j.ymgme.2015.01.007 · 2.83 Impact Factor
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    ABSTRACT: One goal of research using induced pluripotent stem cell (iPSC) is to generate patient-specific cells which can be used to obtain multiple types of differentiated cells as disease models. Minimally or non-integrating methods to deliver the reprogramming genes are considered to be the best but they may be inefficient. Lentiviral delivery is currently among the most efficient methods but it integrates transgenes into the genome, which may affect the behavior of the iPSC if integration occurs into an important locus. Here we designed a polycistronic lentiviral construct containing four pluripotency genes with an EGFP selection marker. The cassette was excisable with the Cre-loxP system making possible the removal of the integrated transgenes from the genome. Mouse embryonic fibroblasts were reprogrammed using this viral system, rapidly resulting large number of iPSC colonies. Based on the lowest EGFP expression level, one parental line was chosen for excision. Introduction of the Cre recombinase resulted in transgene-free iPSC subclones. The effect of the transgenes was assessed by comparing the parental iPSC with two of its transgene-free subclones. Both excised and non-excised iPSCs expressed standard pluripotency markers. The subclones obtained after Cre recombination were capable of differentiation in vitro, in contrast to the parental, non-excised cells and formed germ-line competent chimeras in vivo.
    Experimental Cell Research 04/2014; 322(2). DOI:10.1016/j.yexcr.2014.02.006 · 3.37 Impact Factor
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    ABSTRACT: Embryonic stem cell (ESC)-derived cardiomyocytes are a promising cell source for the screening for potential cytoprotective molecules against ischemia/reperfusion injury, however, little is known on their behavior in hypoxia/reoxygenation conditions. Here we tested the cytoprotective effect of the NO-donor SNAP and its downstream cellular pathway. Mouse ESC-derived cardiomyocytes were subjected to 150-min simulated ischemia (SI) followed by 120-min reoxygenation or corresponding non-ischemic conditions. The following treatments were applied during SI or normoxia: the NO-donor S-Nitroso-N-acetyl-D,L-penicillamine (SNAP), the protein kinase G (PKG) inhibitor, the KATP channel blocker glibenclamide, the particulate guanylate cyclase activator brain type natriuretic peptide (BNP), and a non-specific NO synthase inhibitor (N-Nitro-L-arginine, L-NNA) alone or in different combinations. Viability of cells was assayed by propidium iodide staining. SNAP attenuated SI-induced cell death in a concentration-dependent manner, and this protection was attenuated by inhibition of either PKG or KATP channels. However, SI-induced cell death was not affected by BNP or by L-NNA. We conclude that SNAP protects mESC-derived cardiomyocytes against SI/R injury and that soluble guanylate-cyclase, PKG, and KATP channels play a role in the downstream pathway of SNAP-induced cytoprotection. The present mESC-derived cardiomyocyte-based screening platform is a useful tool for discovery of cytoprotective molecules.
    Molecular Biotechnology 09/2013; DOI:10.1007/s12033-013-9704-2 · 2.28 Impact Factor
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    ABSTRACT: Abstract Embryonic stem cells (ESCs) have the ability to form aggregates, which are called embryoid bodies (EBs). EBs mimic early embryonic development and are commonly produced for cardiomyogenesis. Here, we describe a method of EB formation in hydrodynamic conditions using a slow-turning lateral vessel (STLV) bioreactor and the subsequent differentiation of EBs into cardiomyocytes. EBs formed in the STLV were compared with conventional techniques, such as hanging drop (HD) or static suspension cell culture (SSC), for homogeneity of EB size, shape, proliferation, apoptosis, and in vitro cardiac differentiation. After 3 days of culture, a four-fold improvement in the yield of EB formation/mL, a six-fold enhancement in total yield of EB/mL, and a nearly 10-fold reduction of cells that failed to incorporate into EBs were achieved in STLV versus SSC. During cardiac differentiation, a 1.5- to 4.2-fold increase in the area of cardiac troponin T (cTnT) per single EB in STLV versus SSC and HD was achieved. These results demonstrate that the STLV method improves the quality and quantity of ES cells to form EBs and enhances the efficiency of cardiac differentiation. We have demonstrated that the mechanical method of cell differentiation creates different microenvironments for the cells and thus influences their lineage commitments, even when genetic origin and the culture medium are the same. Ascorbic acid (ASC) improved further cardiac commitment in differentiation assays. Hence, this culture system is suitable for the production of large numbers of cells for clinical cell replacement therapies and industrial drug testing applications.
    09/2013; DOI:10.1089/cell.2012.0082
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    ABSTRACT: Somatic cell reprogramming has generated enormous interest after the first report by Yamanaka and his coworkers in 2006 on the generation of induced pluripotent stem cells (iPSCs) from mouse fibroblasts. Here we report the generation of stable iPSCs from mouse fibroblasts by recombinant protein transduction (Klf4, Oct4, Sox2 and c-Myc), a procedure designed to circumvent the risks caused by integration of exogenous sequences in the target cell genome associated with gene delivery systems. The recombinant proteins were fused in frame to the GST tag for affinity purification and to the TAT-NLS polypeptide to facilitate membrane penetration and nuclear localization. We performed the reprogramming procedure on embryonic fibroblasts from inbred (C57BL6) and outbred (ICR) mouse strains. The cells were treated with purified proteins four times, at 48-hour intervals, and cultured on mitomycin C treated MEF (mouse embryonic fibroblast) cells in complete embryonic stem cell medium until colonies formed. The iPSCs generated from the outbred fibroblasts exhibited similar morphology and growth properties to embryonic stem (ESC) cells and were sustained in an undifferentiated state for more than 20 passages. The cells were checked for pluripotency-related markers (Oct4, Sox2, Klf4, cMyc, Nanog) by immunocytochemistry and by RT-PCR. The protein iPSCs (piPSCs) formed EBs and subsequently differentiated towards all three germ layer lineages. Importantly the piPSCs could incorporate into the blastocyst and led to variable degrees of chimerism in newborn mice. These data show that recombinant purified cell-penetrating proteins are capable of reprogramming mouse embryonic fibroblasts to iPSCs. We also demonstrated that the cells of the generated cell line satisfied all the requirements of bona fide mouse ESC cells: form round colonies with defined boundaries; have a tendency to attach together with high nuclear/cytoplasmic ratio; express key pluripotency markers; and are capable of in vitro differentiation into ecto-, endo-, and mesoderm, and in vivo chimera formation.
    Tissue Engineering Part C Methods 09/2013; DOI:10.1089/ten.TEC.2013.0026 · 4.64 Impact Factor
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    ABSTRACT: Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS) is caused by a 1.5-3 Mb microdeletion of chromosome 22q11.2, frequently referred to as 22q11.2 deletion syndrome (22q11DS). This region includes TBX1, a T-box transcription factor gene that contributes to the etiology of 22q11DS. The requirement for TBX1 in mammalian development is dosage-sensitive, such that loss-of-function (LOF) and gain-of-function (GOF) of TBX1 in both mice and humans results in disease relevant congenital malformations. To further gain insight into the role of Tbx1 in development, we have targeted the Rosa26 locus to generate a new GOF mouse model in which a Tbx1-GFP fusion protein is expressed conditionally using the Cre/LoxP system. Tbx1-GFP expression is driven by the endogenous Rosa26 promoter resulting in ectopic and persistent expression. Tbx1 is pivotal for proper ear and heart development; ectopic activation of Tbx1-GFP in the otic vesicle by Pax2-Cre and Foxg1-Cre represses neurogenesis and produces morphological defects of the inner ear. Overexpression of a single copy of Tbx1-GFP using Tbx1Cre/+ was viable, while overexpression of both copies resulted in neonatal lethality with cardiac outflow tract defects. We have partially rescued inner ear and heart anomalies in Tbx1Cre/- null embryos by expression of Tbx1-GFP. We have generated a new mouse model to conditionally overexpress a GFP-tagged Tbx1 protein in vivo. This provides a useful tool to investigate in vivo direct downstream targets and protein binding partners of Tbx1.
    BMC Developmental Biology 08/2013; 13(1):33. DOI:10.1186/1471-213X-13-33 · 2.75 Impact Factor
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    ABSTRACT: Pluripotent stem cells have the capacity to divide indefinitely and to differentiate into all somatic cells and tissue lines. They can be genetically manipulated in vitro by knocking genes in or out, and therefore serve as an excellent tool for gene function studies and for the generation of models for some human diseases. Since 1981, when the first mouse embryonic stem cell (ESC) line was generated, many attempts have been made to generate pluripotent stem cell lines from other species. Comparative characterization of ESCs from different species would help us to understand differences and similarities in the signaling pathways involved in the maintenance of pluripotency and the initiation of differentiation, and would reveal whether the fundamental mechanism controlling self-renewal of pluripotent cells is conserved across different species. This report gives an overview of research into embryonic and induced pluripotent stem cells in the rabbit, an important nonrodent species with considerable merits as an animal model for specific diseases. A number of putative rabbit ESC and induced pluripotent stem cell lines have been described. All of them expressed stem cell-associated markers and maintained apparent pluripotency during multiple passages in vitro, but none have been convincingly proven to be fully pluripotent in vivo. Moreover, as in other domestic species, the markers currently used to characterize the putative rabbit ESCs are suboptimal because recent studies have revealed that they are not always specific to the pluripotent inner cell mass. Future validation of rabbit pluripotent stem cells would benefit greatly from a validated panel of molecular markers specific to pluripotent cells of the developing rabbit embryos. Using rabbit-specific pluripotency genes may improve the efficiency of somatic cell reprogramming for generating induced pluripotent stem cells and thereby overcome some of the challenges limiting the potential of this technology.
    Theriogenology 11/2012; 78(8):1774-86. DOI:10.1016/j.theriogenology.2012.06.017 · 1.85 Impact Factor
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    ABSTRACT: Abstract Mouse embryonic stem cells (ESCs) and induced pluripotent stem (iPS) cells can be used as models of neuronal differentiation for the investigation of mammalian neurogenesis, pharmacological testing, and development of cell-based therapies. Recently, mouse iPS cell lines have been generated by Sleeping Beauty (SB) transposon-mediated transgenesis (SB-iPS). In this study, we determined for the first time the differentiation potential of mouse SB-iPS cells to form neuronal progenitor cells (NPCs) and neurons. Undifferentiated SB-iPS and ES cells were aggregated into embryoid bodies (EBs) and cultured in neuronal differentiation medium supplemented with 5 μM all-trans retinoic acid. Thereafter, EBs were dissociated and plated to observe further neuronal differentiation. Samples were fixed on days 10 and 14 for immunocytochemistry staining using the NPC markers Pax6 and Nestin and the neuron marker βIII-tubulin/Tuj1. Nestin-labeled cells were analyzed further by flow cytometry. Our results demonstrated that SB-iPS cells can generate NPCs and differentiate further into neurons in culture, although SB-iPS cells produced less nestin-positive cells than ESCs (6.12±1.61 vs. 74.36±1.65, respectively). In conclusion, the efficiency of generating SB-iPS cells-derived NPCs needs to be improved. However, given the considerable potential of SB-iPS cells for drug testing and as therapeutic models in neurological disorders, continuing investigation of their neuronal differentiation ability is required.
    Cellular Reprogramming 08/2012; 14(5):390-7. DOI:10.1089/cell.2012.0010 · 2.35 Impact Factor
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    ABSTRACT: Induced pluripotent stem (iPS) cell technology involves reprogramming somatic cells to a pluripotent state. The original technology used to produce these cells requires viral gene transduction and results in the permanent integration of exogenous genes into the genome. This can lead to the development of abnormalities in the derived iPS cells. Here, we report that non-viral transfection of a Sleeping Beauty (SB) transposon containing the coding sequences Oct3/4 (Pouf1), Sox-2, Klf-4 and c-Myc (OSKM) linked with 2A peptides, can reprogram mouse fibroblasts. We have established reprogrammed mouse cell lines from three different genetic backgrounds: (1) ICR-outbred, (2) C57BL/6-inbred and (3) F1-hybrid (C57BL/6 x DBA/2J), with parallel robust expression of all exogenous (Oct3/4, Sox-2, Klf-4, and c-Myc) and endogenous (e.g. Oct3/4 and Nanog) pluripotency genes. The iPS cell lines exhibited characteristics typical for undifferentiated embryonic stem (ES) cell lines: ES cell-like morphology, alkaline phosphatase (ALP) positivity and gene expression pattern (shown by reverse transcription PCR, and immunofluorescence of ES cell markers-e.g. Oct3/4, SSEA1, Nanog). Furthermore, cells were able to form embryoid bodies (EBs), to beat rhythmically, and express cardiac (assayed by immunofluorescence, e.g. cardiac Troponin T, desmin) and neuronal (assayed by immunofluorescence e.g. nestin, Tuj1) markers. The in vitro differentiation potential was found to be the highest in the ICR-derived iPS lines (ICR-iPS). Interestingly, the ICR-iPS lines had even higher differentiation potential than the ICR-ES cell lines: the rate of EBs forming rhythmically beating cardiomyocytes was 4% in ICR-ES and 79% in ICR-iPS cells, respectively. In vivo, the ICR and F1 hybrid iPS cells formed chimeras and one of the iPS cells from the F1 hybrid background transmitted to the germline. Our results suggest that iPS technology may be useful for generating pluripotent stem cells from genetic backgrounds of which good quality ES cell generation is difficult. These studies provide insights into viral-free iPS technology and may contribute towards defining future cell-based therapies, drug-screening methods and production of transgenic animals using genetically modified iPS cells.
    Experimental Cell Research 07/2012; 318(19):2482-9. DOI:10.1016/j.yexcr.2012.07.014 · 3.37 Impact Factor
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    ABSTRACT: Human induced pluripotent stem cells (iPSC) and neural progenitor cells (NPC) are envisioned to play a vital role in future cell replacement therapy. In this context, porcine iPSC and NPC would be highly useful for pre-clinical safety testing by autologous transplantation in a porcine biomedical model. The objective of this study was to establish iPSC from porcine epiblast-derived NPC by use of a tetracycline-inducible Tet-ON approach. A total of 1.5×10(5) porcine NPC at passage 6 (Rasmussen et al. 2011) were transduced O/N with 0.5ml active virus containing the following porcine pluripotency genes: pOCT4 (pO); pOCT4 and pKLF4 (pOK); pOCT4 and pC-MYC (pOM); pOCT4, pC-MYC, and pKLF4 (pOMK) or polycistronic pOCT4, pSOX2, pC-MYC, and pKLF4 (pOSMK); all including 0.25ml transactivator (rtTA). After 3 days, the cells were trypsinized and passaged to MEF feeder cells and cultured in iPSC medium containing DMEM/F12, 20% KSR, 1% NEAA, 10μM β-Me, 20ngmL(-1) human bFGF and 2μgmL(-1) doxycycline. On Day 8, tightly packed colonies of cells presenting an embryonic stem cell-like morphology were visible in the pOM, pOMK, and pOSMK combinations. In contrast, colonies were not observed with the pO and pOK combination. On Day 14, several iPSC-like colonies were manually picked and sub-cultured on MEF feeder cells in iPSC medium. Two lines from the pOSMK combination were capable of prolonged clonal propagation while maintaining an ESC-like morphology. However, when doxycycline was removed from the culture medium, growth arrest and spontaneous differentiation occurred. The iPSC-like lines expressed OCT4, SOX2, C-MYC, and KLF4, as evaluated by immunocytochemistry, and expression of NANOG, SSEA-1, and SSEA-4 was also confirmed, demonstrating activation of endogenous pluripotency genes. The iPSC-like lines were capable of forming embryoid bodies (EB) without addition of doxycycline and in vitro differentiation of EB in medium containing DMEM and 15% FCS confirmed the presence of meso- (SMA) and endodermal (AFP) derivatives by immunocytochemistry. Furthermore, co-culture experiments with MS5 stromal cells in medium containing DMEM, 15% KSR, and 150ngmL(-1) human Noggin resulted in differentiation into neuroectoderm (NESTIN and SOX2), as well as more mature neurons (TUJI and GFAP). The latter resulted in establishment of new NPC lines. The system can be used to study mechanisms involved in the early transition from pluripotency to multipotency in the pig and the reversal of the process caused by reprogramming.
    Reproduction Fertility and Development 12/2011; 24(1):289. DOI:10.1071/RDv24n1Ab252 · 2.58 Impact Factor
  • Z Tancos, O Ujhelly, M K Pirity, A Dinnyes
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    ABSTRACT: Induced pluripotent stem cells (iPSC) technology, which allows direct reprogramming of somatic cells to a pluripotent state, is a promising tool for gene-function studies disease modelling, drug screening, toxicology tests and to generate knockout animal models. The goal of the current work was to close the gap in knowledge with regard to the molecular biological background for rabbit iPS work by isolating the putative pluripotency genes from the rabbit, based on the sequences published for other species. The sequence of known pluripotency genes (Oct4, Sox2, Klf4, c-Myc, Nanog) were analysed and primers designed based on the similarity of sequences. Sequences of each individual rabbit pluripotency gene was compared to other vertebrates (e.g. human, mouse, bovine) phylogenetically. Rabbit ESCs and blastocyst stage embryos were collected from superovulated rabbits to isolate total RNA. Genes of interest were amplified using RT-PCR and electrophoretically separated for cDNA fragment isolation. Isolated and subcloned cDNA fragments were sequenced and analysed. Our results showed that after restriction digestion the size of amplified and cloned rabbit Oct4, Sox2, Klf4, c-Myc and Nanog gene fragments correspond to the expected amplicon size. Furthermore, sequence confirmation by DNA sequencing has been completed in the case of Oct4, c-Myc, Klf4 and Nanog. The homology of these genes to that of their mouse and human orthologs were as follows: Oct4: at Na level 79% homologue to mouse, 85% homologue to human, at Aa level 81% homologue to mouse, 90% homologue to human; Klf4: at Na level 98% homologue to mouse, 85% homologue to human, at Aa level 95% homologue to mouse, 84% homologue to human; c-myc: at Na level 88% homologue to mouse, 92% homologue to human, at Aa level 91% homologue to mouse and 94% homologue to human; Nanog: at Na level 71% homologue to mouse, 78% homologue to human, at Aa level 55% homologue to mouse, 66% homologue to human. In conclusion, we have revealed differences at both Na and Aa level in all four major rabbit pluripotency gene sequences in comparison to their mammalian orthologs which might partially explain difficulties in generation of rabbit iPSC capable of germline transmission. Our further goal is to apply rabbit specific pluripotency genes to reprogram somatic cells and generate iPSC more efficiently than by using mouse or human genes.
    Reproduction Fertility and Development 12/2011; 24(1):223-4. DOI:10.1071/RDv24n1Ab223 · 2.58 Impact Factor
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    ABSTRACT: Human-induced pluripotent stem cells (iPSC) are envisioned to play a vital role in future cell replacement therapy. In this context, porcine iPSC would be highly useful for pre-clinical safety testing by autologous transplantation in a porcine biomedical model. However, a major impediment is that currently, continuous expression of reprogramming factors is required to maintain the pluripotent state of porcine iPSC. In the mouse, neural progenitor cells (NPC) have proved to be highly amenable to reprogramming due to their partly stem-like epigenetic state and expression of pluripotency-related genes such as SOX2. The objective of this study was to establish iPSC from porcine epiblast-derived NPC by use of a tetracycline-inducible Tet-ON approach. A total of 1.5×10(5) porcine NPC at passage 6 (Rasmussen et al. 2011) were transduced O/N with 0.5mL of active virus containing the following porcine pluripotency genes: pOCT4 (pO); pOCT4 and pKLF4 (pOK); pOCT4 and pC-MYC (pOM); pOCT4, pC-MYC and pKLF4 (pOMK) or polycistronic pOCT4, pSOX2, pC-MYC and pKLF4 (pOSMK); all including 0.25mL of transactivator (rtTA). After 3 days, the cells were trypsinized and passaged to MEF feeder cells and cultured in iPSC medium containing DMEM/F12, 20% KSR, 1% NEAA, 10μM β-Me, 20ngmL(-1) human bFGF and 2μgmL(-1) doxycycline. On Day 8, tightly packed colonies of cells presenting an embryonic stem cell-like morphology were visible in the pOM, pOMK and pOSMK combinations. In contrast, colonies were not observed with the pO and pOK combination. On Day 14, several iPSC-like colonies were manually picked and subcultured on MEF feeder cells in iPSC medium. Two lines from the pOSMK combination were capable of prolonged clonal propagation while maintaining an ESC-like morphology. However, when doxycycline was removed from the culture medium, growth arrest and spontaneous differentiation occurred. The iPSC-like lines expressed OCT4, SOX2, C-MYC and KLF4, as evaluated by immunocytochemistry and expression of NANOG, SSEA-1 and SSEA-4 was also confirmed, demonstrating activation of endogenous pluripotency genes. The iPSC-like lines were capable of forming embryoid bodies (EB) without addition of doxycycline and in vitro differentiation of EB in medium containing DMEM and 15% FCS confirmed the presence of meso- (SMA) and endodermal (AFP) derivatives by immunocytochemistry. Furthermore, co-culture experiments with MS5 stromal cells in medium containing DMEM, 15% KSR and 150ngmL(-1) human Noggin resulted in differentiation into neuroectoderm (NESTIN and SOX2), as well as more mature neurons (TUJI and GFAP). The porcine iPSC-like lines could serve as an excellent platform for optimizing culture conditions, which may sustain the pluripotency network in the pig and could be applied for autologous stem cell transplantation in a porcine model for evaluation of safety and efficacy.
    Reproduction Fertility and Development 12/2011; 24(1):217-8. DOI:10.1071/RDv24n1Ab211 · 2.58 Impact Factor
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    ABSTRACT: Embryoid body (EB) formation is a common intermediate during in vitro differentiation of pluripotent stem cells into specialized cell types. We have optimized the slow-turning, lateral vessel (STLV) for large scale and homogenous EB production from mouse embryonic stem cells. The effects of inoculating different cell numbers, time of EB adherence to gelatin-coated dishes, and rotation speed for optimal EB formation and cardiac differentiation were investigated. Using 3 × 10(5) cells/ml, 10 rpm rotary speed and plating of EBs onto gelatin-coated surfaces three days after culture, were the best parameters for optimal size and EB quality on consequent cardiac differentiation. These optimized parameters enrich cardiac differentiation in ES cells when using the STLV method.
    Biotechnology Letters 04/2011; 33(8):1565-73. DOI:10.1007/s10529-011-0614-8 · 1.74 Impact Factor
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    ABSTRACT: Derivation of embryonic stem (ES) cells from parthenogenetic embryos represents a possible alternative approach to create histocompatible cells for regenerative medicine. The objectives of this study were to establish mouse parthenogenetic ES (pES) cell lines from parthenogenetically-derived blastocysts as a model system for human and animal research and to examine pluripotency differences among the pES cell lines. We are able to report the successful establishment of four pluripotent pES cell lines from blastocysts of parthenogenetic origin (22% efficiency of pES cell line establishment). Four pES cell lines (pES#1-4) exhibited a typical ES cell morphology and expression of key pluripotency markers (ALP, Oct4, Nanog and SSEA-1). Three of the four pES cell lines have shown a high percentage of normal karyotype during long-term culture. Variability in the in vitro differentiation potential into cell types of the 3 germ layers was observed among the different pES cell lines. Three of these (pES#1-3) exhibited a higher efficiency towards endo-mesoderm differentiation, strongly expressed differentiation markers towards endo-mesoderm lineage (α-fetoprotein; Flk-1; PECAM and collagen IV) than pES#4. Differentiation towards cardiac cells resulted in all cell lines 33-100% of spontaneous beating cell clusters/well. Furthermore, following injection into blastocysts pES#1 cells differentiated successfully in vivo into chimeric mice with an efficiency of 75% (three chimeras of four newborns). In conclusion, our results have demonstrated that there are major differences among pES lines in their differentiation ability in vitro and that it was possible to generate chimera forming pES cell lines in mouse.
    The Thai veterinary medicine 01/2011; 41:143-155. · 0.12 Impact Factor
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    ABSTRACT: Regenerative cell therapy against cardiovascular disease would require mass production and purification of specific cell types before transplantation. To enable large-scale production of embryonic stem (ES)-derived pure cardiomyocytes, we developed an animal model for a single-step scalable bioprocess that allows direct embryoid body (EB) formation in a fully controlled slow-turning lateral vessel (STLV, Synthecon, Inc., Houston, TX, USA) bioreactor following inoculation with a single cell suspension of mouse ES cells. To enhance the yield of cardiac progenitor cells, mouse ES cells (HM1; 129Sv/Ola, Magin et al. 1992 Nucl. Acids Res. 20, 3795-3796) were targeted with the cardiac-specific mouse Nkx2.5 promoter driven enhanced fluorescent green protein (EGFP). Among 15 targeted colonies, which were characterised based on morphology, the ability to form EB, EGFP expression, and in vitro differentiation ability toward cardiomyocytes, 3 lines were further evaluated for the efficiency of cardiomyocyte production. The 3 lines were cultured in STLV bioreactor and compared with classical hanging drop (HD) and static suspension culture methods. Embryonic bodies at day 3 to 8 were collected and analysed by using fluorescence-activated cell sorting for markers of pluripotency (e.g. Oct-4, SSEA1, Nanog) and cardiac (e.g. Nkx2.5, Troponin T) lineage commitments. Data was analysed by one-way ANOVA and t-tests. The results showed that both level and kinetics of Nkx2.5 expression was dependent on culture conditions. The STLV and static suspension culture methods produced higher rates of Nkx2.5-positive cells on day 5 than that of HD (70 and 54 v. 30%, respectively). The STLV method produced a highly uniform population of efficiently differentiating EB in large quantities and resulted in the highest, 10(8) yield of cardiomyocytes in a single 110-mL STLV on day 4. In conclusion, the STLV method provides a technological platform for controlled large-scale generation of ES-cell-derived cardiomyocytes for clinical and industrial applications. In vivo transplantation tests of cardiomyocytes produced via STLV are currently underway.
    Reproduction Fertility and Development 01/2011; 23(1):244. DOI:10.1071/RDv23n1Ab293 · 2.58 Impact Factor
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    ABSTRACT: Brahma-related gene 1 (Brg1, also known as Smarca4 and Snf2β) encodes an adenosine-5'-triphosphate (ATP)-dependent catalytical subunit of the (switch/sucrose nonfermentable) (SWI/SNF) chromatin remodeling complexes. SWI/SNF complexes are recruited to chromatin through multiple mechanisms, including specific DNA-binding factors (for example, heat shock transcription factor 4 (Hsf4) and paired box gene 6 (Pax6)), chromatin structural proteins (for example, high-mobility group A1 (HMGA1)) and/or acetylated core histones. Previous studies have shown that a single amino acid substitution (K798R) in the Brg1 ATPase domain acts via a dominant-negative (dn) mechanism. Genetic studies have demonstrated that Brg1 is an essential gene for early (that is, prior implantation) mouse embryonic development. Brg1 also controls neural stem cell maintenance, terminal differentiation of multiple cell lineages and organs including the T-cells, glial cells and limbs. To examine the roles of Brg1 in mouse lens development, a dnBrg1 transgenic construct was expressed using the lens-specific αA-crystallin promoter in postmitotic lens fiber cells. Morphological studies revealed abnormal lens fiber cell differentiation in transgenic lenses resulting in cataract. Electron microscopic studies showed abnormal lens suture formation and incomplete karyolysis (that is, denucleation) of lens fiber cells. To identify genes regulated by Brg1, RNA expression profiling was performed in embryonic day 15.5 (E15.5) wild-type and dnBrg1 transgenic lenses. In addition, comparisons between differentially expressed genes in dnBrg1 transgenic, Pax6 heterozygous and Hsf4 homozygous lenses identified multiple genes coregulated by Brg1, Hsf4 and Pax6. DNase IIβ, a key enzyme required for lens fiber cell denucleation, was found to be downregulated in each of the Pax6, Brg1 and Hsf4 model systems. Lens-specific deletion of Brg1 using conditional gene targeting demonstrated that Brg1 was required for lens fiber cell differentiation, for expression of DNase IIβ, for lens fiber cell denucleation and indirectly for retinal development. These studies demonstrate a cell-autonomous role for Brg1 in lens fiber cell terminal differentiation and identified DNase IIβ as a potential direct target of SWI/SNF complexes. Brg1 is directly or indirectly involved in processes that degrade lens fiber cell chromatin. The presence of nuclei and other organelles generates scattered light incompatible with the optical requirements for the lens.
    Epigenetics & Chromatin 11/2010; 3(1):21. DOI:10.1186/1756-8935-3-21 · 4.46 Impact Factor
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    Melinda K Pirity, Andras Dinnyes
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    ABSTRACT: Induced pluripotent stem cells (iPSCs) are novel tools for biomedical research, with a promise for future regenerative medicine applications. Recently, Han and colleagues reported in Nature that T box gene 3 (Tbx3) can improve the quality of mouse iPSCs and increase their germline transmission efficacy. This observation contributes greatly to the improvement of iPSC technology and might be a step towards 'designer' reprogramming strategies by generating high quality iPSCs. Further studies comparing pluripotency regulation in different species, including that in human, will be necessary to verify the universal role of Tbx3 and the medical relevance of the observation.
    Stem Cell Research & Therapy 01/2010; 1(2):12. DOI:10.1186/scrt12 · 4.63 Impact Factor
  • Reproduction Fertility and Development 01/2010; 22(1). DOI:10.1071/RDv22n1Ab398 · 2.58 Impact Factor
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    ABSTRACT: Embryonic stem (ES) cells have the ability to differentiate into all germ layers, holding great promise not only for a model of early embryonic development but also for a robust cell source for cell-replacement therapies and for drug screening. Embryoid body (EB) formation from ES cells is a common method for producing different cell lineages for further applications. However, conventional techniques such as hanging drop or static suspension culture are either inherently incapable of large scale production or exhibit limited control over cell aggregation during EB formation and subsequent EB aggregation. For standardized mass EB production, a well defined scale-up platform is necessary. Recently, novel scenario methods of EB formation in hydrodynamic conditions created by bioreactor culture systems using stirred suspension systems (spinner flasks), rotating cell culture system and rotary orbital culture have allowed large-scale EB formation. Their use allows for continuous monitoring and control of the physical and chemical environment which is difficult to achieve by traditional methods. This review summarizes the current state of production of EBs derived from pluripotent cells in various culture systems. Furthermore, an overview of high quality EB formation strategies coupled with systems for in vitro differentiation into various cell types to be applied in cell replacement therapy is provided in this review. Recently, new insights in induced pluripotent stem (iPS) cell technology showed that differentiation and lineage commitment are not irreversible processes and this has opened new avenues in stem cell research. These cells are equivalent to ES cells in terms of both self-renewal and differentiation capacity. Hence, culture systems for expansion and differentiation of iPS cells can also apply methodologies developed with ES cells, although direct evidence of their use for iPS cells is still limited.
    12/2009; 1(1):11-21. DOI:10.4252/wjsc.v1.i1.11

Publication Stats

475 Citations
105.45 Total Impact Points

Institutions

  • 2012–2015
    • Hungarian Academy of Sciences
      • Institute of Genetics
      Budapeŝto, Budapest, Hungary
  • 2010–2015
    • BioTalentum
      Gödölö, Pest, Hungary
  • 2003–2013
    • Albert Einstein College of Medicine
      • Department of Genetics
      New York, New York, United States
  • 2009–2011
    • Agricultural Biotechnology Center
      Budapeŝto, Budapest, Hungary
  • 1998
    • Samuel Lunenfeld Research Institute
      Toronto, Ontario, Canada