1
|
Nguyen NTB, Leung HW, Pang KT, Tay SJ, Walsh I, Choo ABH, Yang Y. Optimizing effector functions of monoclonal antibodies via tailored N-glycan engineering using a dual landing pad CHO targeted integration platform. Sci Rep 2023; 13:15620. [PMID: 37731040 PMCID: PMC10511539 DOI: 10.1038/s41598-023-42925-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 09/16/2023] [Indexed: 09/22/2023] Open
Abstract
Monoclonal antibodies (mAbs) eliminate cancer cells via various effector mechanisms including antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC), which are influenced by the N-glycan structures on the Fc region of mAbs. Manipulating these glycan structures on mAbs allows for optimization of therapeutic benefits associated with effector functions. Traditional approaches such as gene deletion or overexpression often lead to only all-or-nothing changes in gene expression and fail to modulate the expression of multiple genes at defined ratios and levels. In this work, we have developed a CHO cell engineering platform enabling modulation of multiple gene expression to tailor the N-glycan profiles of mAbs for enhanced effector functions. Our platform involves a CHO targeted integration platform with two independent landing pads, allowing expression of multiple genes at two pre-determined genomic sites. By combining with internal ribosome entry site (IRES)-based polycistronic vectors, we simultaneously modulated the expression of α-mannosidase II (MANII) and chimeric β-1,4-N-acetylglucosaminyl-transferase III (cGNTIII) genes in CHO cells. This strategy enabled the production of mAbs carrying N-glycans with various levels of bisecting and non-fucosylated structures. Importantly, these engineered mAbs exhibited different degrees of effector cell activation and CDC, facilitating the identification of mAbs with optimal effector functions. This platform was demonstrated as a powerful tool for producing antibody therapeutics with tailored effector functions via precise engineering of N-glycan profiles. It holds promise for advancing the field of metabolic engineering in mammalian cells.
Collapse
|
2
|
Yap L, Murali S, Bhakta G, Titmarsh DM, Chen AKL, Chiin Sim L, Bardor M, Lim YM, Goh JCH, Oh SKW, Choo ABH, van Wijnen AJ, Robinson DE, Whittle JD, Birch WR, Short RD, Nurcombe V, Cool SM. Immobilization of vitronectin-binding heparan sulfates onto surfaces to support human pluripotent stem cells. J Biomed Mater Res B Appl Biomater 2017; 106:1887-1896. [PMID: 28941021 DOI: 10.1002/jbm.b.33999] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 08/11/2017] [Accepted: 09/01/2017] [Indexed: 11/10/2022]
Abstract
Functionalizing medical devices with polypeptides to enhance their performance has become important for improved clinical success. The extracellular matrix (ECM) adhesion protein vitronectin (VN) is an effective coating, although the chemistry used to attach VN often reduces its bioactivity. In vivo, VN binds the ECM in a sequence-dependent manner with heparan sulfate (HS) glycosaminoglycans. We reasoned therefore that sequence-based affinity chromatography could be used to isolate a VN-binding HS fraction (HS9) for use as a coating material to capture VN onto implant surfaces. Binding avidity and specificity of HS9 were confirmed by enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR)-based assays. Plasma polymerization of allylamine (AA) to tissue culture-treated polystyrene (TCPS) was then used to capture and present HS9 as determined by radiolabeling and ELISA. HS9-coated TCPS avidly bound VN, and this layered surface supported the robust attachment, expansion, and maintenance of human pluripotent stem cells. Compositional analysis demonstrated that 6-O- and N-sulfation, as well as lengths greater than three disaccharide units (dp6) are critical for VN binding to HS-coated surfaces. Importantly, HS9 coating reduced the threshold concentration of VN required to create an optimally bioactive surface for pluripotent stem cells. We conclude that affinity-purified heparan sugars are able to coat materials to efficiently bind adhesive factors for biomedical applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1887-1896, 2018.
Collapse
|
3
|
Ding V, Lew QJ, Chu KL, Natarajan S, Rajasegaran V, Gurumurthy M, Choo ABH, Chao SH. HEXIM1 induces differentiation of human pluripotent stem cells. PLoS One 2013; 8:e72823. [PMID: 23977357 PMCID: PMC3748041 DOI: 10.1371/journal.pone.0072823] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 07/19/2013] [Indexed: 02/07/2023] Open
Abstract
Hexamethylene bisacetamide inducible protein 1 (HEXIM1) is best known as the inhibitor of positive transcription elongation factor b (P-TEFb), which is composed of cyclin-dependent kinase 9 (CDK9)/cyclin T1. P-TEFb is an essential regulator for the transcriptional elongation by RNA polymerase II. A genome-wide study using human embryonic stem cells shows that most mRNA synthesis is regulated at the stage of transcription elongation, suggesting a possible role for P-TEFb/HEXIM1 in the gene regulation of stem cells. In this report, we detected a marked increase in HEXIM1 protein levels in the differentiated human pluripotent stem cells (hPSCs) induced by LY294002 treatment. Since no changes in CDK9 and cyclin T1 were observed in the LY294002-treated cells, increased levels of HEXIM1 might lead to inhibition of P-TEFb activity. However, treatment with a potent P-TEFb inhibiting compound, flavopiridol, failed to induce hPSC differentiation, ruling out the possible requirement for P-TEFb kinase activity in hPSC differentiation. Conversely, differentiation was observed when hPSCs were incubated with hexamethylene bisacetamide, a HEXIM1 inducing reagent. The involvement of HEXIM1 in the regulation of hPSCs was further supported when overexpression of HEXIM1 concomitantly induced hPSC differentiation. Collectively, our study demonstrates a novel role of HEXIM1 in regulating hPSC fate through a P-TEFb-independent pathway.
Collapse
|
4
|
Berrill A, Tan HL, Wuang SC, Fong WJ, Choo ABH, Oh SKW. Assessment of stem cell markers during long-term culture of mouse embryonic stem cells. Cytotechnology 2012; 44:77-91. [PMID: 19003231 DOI: 10.1023/b:cyto.0000043414.90681.c2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Embryonic stem (ES) cells have been in the fore front of scientific literature lately as having the potential for regeneration of many tissue types. Two important issues that need to be addressed are the culture conditions for maintaining ES cells and the accuracy of ES cell markers in monitoring the undifferentiated state. Leukaemia inhibitory factor (LIF) is routinely used to sustain mouse ES cells (mES) in a pluripotent fashion. In this paper, we assessed three markers during long-term maintenance of ES cells with various concentrations of LIF to see if decreasing concentration would lead to changes in marker expressions and growth behavior. Common markers of pluripotency such as alkaline phosphatase enzyme activity (ALP), surface staining for stage specific embryonic antigen 1 (SSEA-1), Oct-4 transcription factor, cell doubling time, as well as visual observations of cell morphology were analyzed during long-term maintenance of mES cells with LIF concentrations ranging from 0 to 500 pM. The morphology of the cells at LIF concentrations of 0 25 pM changed from being tight clusters to more flattened shapes while cells in 50-500 pM retained the clustered shape but growth rates remained essentially identical at between 10 and 16 h. ES cells at all concentrations of LIF continued expressing ALP, SSEA-1 and Oct-4 markers over a period of 6 weeks, which indicate that mES cells are capable of either producing autocrine LIF or are able to proliferate at very low levels of LIF. Pluripotency markers such as Oct-4 and SSEA-1 are only moderately reduced after 5-6 weeks. Oct-4 mRNA expression levels were partially diminished in LIF free conditions only at weeks 5 and 6 compared to controls with LIF at 500 pM. Changes in morphology of cells by visual observation seemed to be a faster indication of the onset of differentiation in mES cells, although other reliable means also include decreased levels of Oct-4, SSEA-1 and ALP markers. It is preferable to maintain long-term cultures of mES cells above 50 pM of LIF to have a more homogenous, stable population of pluripotent cells.
Collapse
|
5
|
Chan LY, Yim EKF, Choo ABH. Normalized median fluorescence: an alternative flow cytometry analysis method for tracking human embryonic stem cell states during differentiation. Tissue Eng Part C Methods 2012; 19:156-65. [PMID: 22838642 DOI: 10.1089/ten.tec.2012.0150] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Human embryonic stem cells (hESCs) are a promising cell source for tissue engineering and regenerative medicine, but before they can be used in therapies, we must be able to accurately identify the state and progeny of hESCs. One of the most commonly used methods for identification is flow cytometry. Many flow cytometry applications use antibodies to detect the amount of antigen present on/in a cell. This allows for the identification of unique cell populations or the tracking of expression changes within a population during differentiation. The results are typically presented as a percentage of positively expressing cells (%Pos) for a marker of choice, relative to a negative control. However, this reporting term is vulnerable to distortion from outliers and inaccuracy from loss of information about the population's fluorescence intensity. In this article, we describe an alternate strategy that uses the normalized median fluorescence intensity (nMFI), in which the MFI of the stained sample is normalized to the MFI of the negative control, as the reporting term to more accurately describe a population of cells in culture. We observed that nMFI provides a more accurate representation for the quality of a starting population and comparing data of different experimental runs. In addition, we demonstrated that the nMFI is a more sensitive measure of pluripotent and differentiation markers expression changes during hESC differentiation into three germ layer lineages.
Collapse
|
6
|
Lin W, Oh SKW, Choo ABH, George AJT. Activated T cells modulate immunosuppression by embryonic-and bone marrow-derived mesenchymal stromal cells through a feedback mechanism. Cytotherapy 2011; 14:274-84. [PMID: 22136295 DOI: 10.3109/14653249.2011.635853] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND AIMS Human embryonic stem cell (hESC)-derived mesenchymal stromal cells (MSC) (hESC-MSC) are an alternative source of MSC to bone marrow (BM)-derived MSC (BM-MSC), which are being investigated in clinical trials for their immunomodulatory potential. hESC-MSC have the advantage of being consistent because each batch can be generated from hESC under defined conditions. In contrast, BM-MSC have a limited proliferative capacity. METHODS The ability to suppress the proliferation of anti-CD3/CD28-stimulated CD4 (+) T cells by hESC-MSC was compared with adult BM-MSC and neonatal foreskin fibroblast (Fb). RESULTS hESC-MSC suppress the proliferation of CD4 (+) T cells in both contact and transwell systems, although inhibition is less in the transwell system. hESC-MSC are approximately 2-fold less potent (67 cells/100 T cells) than BM-MSC and Fb (37 and 34 cells/100 T cells, respectively) at suppressing T-cell proliferation by 50% in a transwell [inhibitory concentration(IC)(50)]. The anti-proliferative effect is not contact-dependent but requires the presence of factors such as interferon (IFN)-γ produced by activated T cells. IFN-γ induces the expression of indoleamine-2,3-dioxygenase (IDO) in hESC-MSC, BM-MSC and Fb, contributing to their immunosuppressive property. CONCLUSIONS The feedback loop between MSC or Fb and activated T cells may limit the immunosuppressive effects of MSC and Fb to sites containing ongoing immunologic or inflammatory responses where activated T cells induce the up-regulation of IDO and immunomodulatory properties of MSC and Fb. These data demonstrate that hESC-MSC may be evaluated further as an allogeneic cell source for therapeutic applications requiring immunosuppression.
Collapse
|
7
|
Amps K, Andrews PW, Anyfantis G, Armstrong L, Avery S, Baharvand H, Baker J, Baker D, Munoz MB, Beil S, Benvenisty N, Ben-Yosef D, Biancotti JC, Bosman A, Brena RM, Brison D, Caisander G, Camarasa MV, Chen J, Chiao E, Choi YM, Choo ABH, Collins D, Colman A, Crook JM, Daley GQ, Dalton A, De Sousa PA, Denning C, Downie J, Dvorak P, Montgomery KD, Feki A, Ford A, Fox V, Fraga AM, Frumkin T, Ge L, Gokhale PJ, Golan-Lev T, Gourabi H, Gropp M, Lu G, Hampl A, Harron K, Healy L, Herath W, Holm F, Hovatta O, Hyllner J, Inamdar MS, Irwanto AK, Ishii T, Jaconi M, Jin Y, Kimber S, Kiselev S, Knowles BB, Kopper O, Kukharenko V, Kuliev A, Lagarkova MA, Laird PW, Lako M, Laslett AL, Lavon N, Lee DR, Lee JE, Li C, Lim LS, Ludwig TE, Ma Y, Maltby E, Mateizel I, Mayshar Y, Mileikovsky M, Minger SL, Miyazaki T, Moon SY, Moore H, Mummery C, Nagy A, Nakatsuji N, Narwani K, Oh SKW, Oh SK, Olson C, Otonkoski T, Pan F, Park IH, Pells S, Pera MF, Pereira LV, Qi O, Raj GS, Reubinoff B, Robins A, Robson P, Rossant J, Salekdeh GH, Schulz TC, Sermon K, Sheik Mohamed J, Shen H, Sherrer E, Sidhu K, Sivarajah S, Skottman H, Spits C, Stacey GN, Strehl R, Strelchenko N, Suemori H, Sun B, Suuronen R, Takahashi K, Tuuri T, Venu P, Verlinsky Y, Ward-van Oostwaard D, Weisenberger DJ, Wu Y, Yamanaka S, Young L, Zhou Q. Screening ethnically diverse human embryonic stem cells identifies a chromosome 20 minimal amplicon conferring growth advantage. Nat Biotechnol 2011; 29:1132-44. [PMID: 22119741 PMCID: PMC3454460 DOI: 10.1038/nbt.2051] [Citation(s) in RCA: 427] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 10/26/2011] [Indexed: 02/07/2023]
Abstract
The International Stem Cell Initiative analyzed 125 human embryonic stem (ES) cell lines and 11 induced pluripotent stem (iPS) cell lines, from 38 laboratories worldwide, for genetic changes occurring during culture. Most lines were analyzed at an early and late passage. Single-nucleotide polymorphism (SNP) analysis revealed that they included representatives of most major ethnic groups. Most lines remained karyotypically normal, but there was a progressive tendency to acquire changes on prolonged culture, commonly affecting chromosomes 1, 12, 17 and 20. DNA methylation patterns changed haphazardly with no link to time in culture. Structural variants, determined from the SNP arrays, also appeared sporadically. No common variants related to culture were observed on chromosomes 1, 12 and 17, but a minimal amplicon in chromosome 20q11.21, including three genes expressed in human ES cells, ID1, BCL2L1 and HM13, occurred in >20% of the lines. Of these genes, BCL2L1 is a strong candidate for driving culture adaptation of ES cells.
Collapse
|
8
|
Chen AK, Chen X, Choo ABH, Reuveny S, Oh SKW. Expansion of human embryonic stem cells on cellulose microcarriers. CURRENT PROTOCOLS IN STEM CELL BIOLOGY 2011; Chapter 1:Unit 1C.11. [PMID: 20814936 DOI: 10.1002/9780470151808.sc01c11s14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
This unit describes the routine maintenance and expansion of undifferentiated human embryonic stem cells (hESC) on cellulose microcarriers. Conventionally, hESCs have been maintained on feeder cells or extracellular matrix-coated two-dimensional tissue culture plates. The expansion of hESC on a tissue culture platform is limited by the available surface area and the requirement of repetitive subculturing to reach the required cell yield. Here, we show that expansion of hESC can be carried out in a three-dimensional suspension culture using Matrigel-coated cellulose microcarriers. hESCs from a tissue culture plate can be seeded directly onto the microcarriers; hESC microcarrier culture is passaged and expanded by mechanical dissociation of the cells without enzyme. Expansion of the culture in a 100-ml spinner flask is also described. Long-term culture of hESC on the microcarriers maintains typical pluripotent markers (OCT-4, Tra-1-60, and SSEA-4) and stable karyotype. Spontaneous differentiations of microcarrier-maintained hESCs in vitro (embryoid body formation) and in vivo (teratoma formation in SCID mouse) have demonstrated formation of the three germ layers. These protocols can also be applied equally well to human induced pluripotent stem cells.
Collapse
|
9
|
Leung HW, Chen A, Choo ABH, Reuveny S, Oh SKW. Agitation can induce differentiation of human pluripotent stem cells in microcarrier cultures. Tissue Eng Part C Methods 2010; 17:165-72. [PMID: 20698747 DOI: 10.1089/ten.tec.2010.0320] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
One of the factors that can impact human embryonic stem cell expansion in stirred microcarrier culture reactors is mechanical stress caused by agitation. Therefore, we have investigated the effects of agitation on human embryonic stem cell growth and expression of pluripotent markers. Agitation of HES-2 cell line in microcarrier cultures in stirred spinner and agitated six-well plates did not affect expression of pluripotent markers, cell viability, and cell doubling times even after seven passages. However, HES-3 cell line was found to be shear sensitive, showing downregulation of three pluripotent markers Oct-4, mAb 84, and Tra-1-60, and lower cell densities in agitated as compared with static cultures, even after one passage. Cell viability was unaffected. The HES-3-agitated cultures showed increased expression of genes and proteins of the three germ layers. We were unable to prevent loss of pluripotent markers or restore doubling times in agitated HES-3 microcarrier cultures by addition of five different known cell protective polymers. In addition, the human induced pluripotent cell line IMR90 was also shown to differentiate in agitated conditions. These results indicate that the effect of agitation on cell growth and differentiation is cell line specific. We assume that the changes in the growth and differentiation of the agitation-sensitive (HES-3) cell line do not result from the effect of shear stress directly on cell viability, but rather by signaling effects that influence the cells to differentiate resulting in slower growth.
Collapse
|
10
|
Ding VMY, Ling L, Natarajan S, Yap MGS, Cool SM, Choo ABH. FGF-2 modulates Wnt signaling in undifferentiated hESC and iPS cells through activated PI3-K/GSK3beta signaling. J Cell Physiol 2010; 225:417-28. [PMID: 20506199 DOI: 10.1002/jcp.22214] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Fibroblast growth factor-2 (FGF-2) is widely used to culture human embryonic stem cells (hESC) and induced pluripotent stem (iPS) cells. Despite its importance in maintaining undifferentiated hESC phenotype, a lack of understanding in the role of FGF-2 still exists. Here, we investigate the signaling events in hESC following the addition of exogenous FGF-2. In this study, we show that hESC express all forms of fibroblast growth factor receptors (FGFRs) which co-localize on Oct3/4 positive cells. Furthermore, downregulation of Oct3/4 in hESC occurs following treatment with an FGFR inhibitor, suggesting that FGF signaling may regulate Oct3/4 expression. This is also observed in iPS cells. Also, downstream of FGF signaling, both mitogen activated protein kinase (MAPK) and phosphoinositide 3-kinase pathways (PI3-K) are activated following FGF-2 stimulation. Notably, inhibition of MAPK and PI3-K signaling using specific kinase inhibitors revealed that activated PI3-K, rather than MAPK, can mediate pluripotent marker expression. To understand the importance of PI3-K activation, activation of Wnt/beta-catenin by FGF-2 was investigated. Wnt signaling had been implicated to have a role in maintaining of pluripotent hESC. We found that upon FGF-2 stimulation, GSK3beta is phosphorylated following which nuclear translocation of beta-catenin and TCF/LEF activation occurs. Interestingly, inhibition of the Wnt pathway with Dikkopf-1 (DKK-1) resulted in only partial suppression of the FGF-2 induced TCF/LEF activity. Prolonged culture of hESC with DKK-1 did not affect pluripotent marker expression. These results suggest that FGF-2 mediated PI3-K signaling may have a direct role in modulating the downstream of Wnt pathway to maintain undifferentiated hESC.
Collapse
|
11
|
Yap LYW, Li J, Phang IY, Ong LT, Ow JZE, Goh JCH, Nurcombe V, Hobley J, Choo ABH, Oh SKW, Cool SM, Birch WR. Defining a threshold surface density of vitronectin for the stable expansion of human embryonic stem cells. Tissue Eng Part C Methods 2010; 17:193-207. [PMID: 20726687 DOI: 10.1089/ten.tec.2010.0328] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Current methodology for pluripotent human embryonic stem cells (hESCs) expansion relies on murine sarcoma basement membrane substrates (Matrigel™), which precludes the use of these cells in regenerative medicine. To realize the clinical efficacy of hESCs and their derivatives, expansion of these cells in a defined system that is free of animal components is required. This study reports the successful propagation of hESCs (HES-3 and H1) for > 20 passages on tissue culture-treated polystyrene plates, coated from 5 μg/mL of human plasma-purified vitronectin (VN) solution. Cells maintain expression of pluripotent markers Tra1-60 and OCT-4 and are karyotypically normal after 20 passages of continuous culture. In vitro and in vivo differentiation of hESC by embryoid body formation and teratoma yielded cells from the ecto-, endo-, and mesoderm lineages. VN immobilized on tissue culture polystyrene was characterized using a combination of X-ray photoemission spectroscopy, atomic force microscopy, and quantification of the VN surface density with a Bradford protein assay. Ponceau S staining was used to measure VN adsorption and desorption kinetics. Tuning the VN surface density, via the concentration of depositing solution, revealed a threshold surface density of 250 ng/cm², which is required for hESCs attachment, proliferation, and differentiation. Cell attachment and proliferation assays on VN surface densities above this threshold show the substrate properties to be equally viable.
Collapse
|
12
|
Ng VY, Ang SN, Chan JX, Choo ABH. Characterization of epithelial cell adhesion molecule as a surface marker on undifferentiated human embryonic stem cells. Stem Cells 2010; 28:29-35. [PMID: 19785009 DOI: 10.1002/stem.221] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Human embryonic stem cells (hESCs) have the capacity to remain pluripotent and self-renew indefinitely. To discover novel players in the maintenance of hESCs, we have previously reported the generation of monoclonal antibodies that bind to cell surface markers on hESCs, and not to mouse embryonic stem cells or differentiated embryoid bodies. In this study, we have identified the antigen target of one such monoclonal antibody as the epithelial cell adhesion molecule (EpCAM). In undifferentiated hESCs, EpCAM is localized to Octamer 4 (OCT4)-positive pluripotent cells, and its expression is down-regulated upon differentiation. To further understand its biological function in hESCs, endogenous EpCAM expression was silenced using small interfering RNA. EpCAM knockdown had marginal negative effects on OCT4 and TRA-1-60 expression, however cell proliferation was decreased by >40%. Examination of lineage marker expression showed marked upregulation of endoderm and mesoderm genes in EpCAM-silenced cells, under both pluripotent and differentiating conditions. These results were validated using a hESC line whose EpCAM expression has been stably knocked down. Data from the stable line confirmed that downregulation of EpCAM decreases cell growth and increases gene expression in the endoderm and mesoderm lineages. In vivo, hESCs lacking EpCAM were able to form teratomas containing tissues representing the three germ layers, and gene expression analysis yielded marked increase in the endoderm marker alpha fetoprotein compared with control. Together these data demonstrate that EpCAM is a surface marker on undifferentiated hESCs and plays functional roles in proliferation and differentiation.
Collapse
|
13
|
Boersema PJ, Foong LY, Ding VMY, Lemeer S, van Breukelen B, Philp R, Boekhorst J, Snel B, den Hertog J, Choo ABH, Heck AJR. In-depth qualitative and quantitative profiling of tyrosine phosphorylation using a combination of phosphopeptide immunoaffinity purification and stable isotope dimethyl labeling. Mol Cell Proteomics 2009; 9:84-99. [PMID: 19770167 DOI: 10.1074/mcp.m900291-mcp200] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Several mass spectrometry-based assays have emerged for the quantitative profiling of cellular tyrosine phosphorylation. Ideally, these methods should reveal the exact sites of tyrosine phosphorylation, be quantitative, and not be cost-prohibitive. The latter is often an issue as typically several milligrams of (stable isotope-labeled) starting protein material are required to enable the detection of low abundance phosphotyrosine peptides. Here, we adopted and refined a peptidecentric immunoaffinity purification approach for the quantitative analysis of tyrosine phosphorylation by combining it with a cost-effective stable isotope dimethyl labeling method. We were able to identify by mass spectrometry, using just two LC-MS/MS runs, more than 1100 unique non-redundant phosphopeptides in HeLa cells from about 4 mg of starting material without requiring any further affinity enrichment as close to 80% of the identified peptides were tyrosine phosphorylated peptides. Stable isotope dimethyl labeling could be incorporated prior to the immunoaffinity purification, even for the large quantities (mg) of peptide material used, enabling the quantification of differences in tyrosine phosphorylation upon pervanadate treatment or epidermal growth factor stimulation. Analysis of the epidermal growth factor-stimulated HeLa cells, a frequently used model system for tyrosine phosphorylation, resulted in the quantification of 73 regulated unique phosphotyrosine peptides. The quantitative data were found to be exceptionally consistent with the literature, evidencing that such a targeted quantitative phosphoproteomics approach can provide reproducible results. In general, the combination of immunoaffinity purification of tyrosine phosphorylated peptides with large scale stable isotope dimethyl labeling provides a cost-effective approach that can alleviate variation in sample preparation and analysis as samples can be combined early on. Using this approach, a rather complete qualitative and quantitative picture of tyrosine phosphorylation signaling events can be generated.
Collapse
|
14
|
Wu SM, Choo ABH, Yap MGS, Chan KKK. Role of Sonic hedgehog signaling and the expression of its components in human embryonic stem cells. Stem Cell Res 2009; 4:38-49. [PMID: 19836325 DOI: 10.1016/j.scr.2009.09.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 09/07/2009] [Accepted: 09/08/2009] [Indexed: 02/08/2023] Open
Abstract
Human embryonic stem cells (hESC) are characterized by their ability to self-renew and differentiate into all cell types of the body, making them a valuable resource for regenerative medicine. Yet, the molecular mechanisms by which hESC retain their capacity for self-renewal and differentiation remain unclear. The Hedgehog signaling pathway plays a pivotal role in organogenesis and differentiation during development, and is also involved in the proliferation and cell-fate specification of neural stem cells and neural crest stem cells. As there has been no detailed study of the Sonic hedgehog (SHH) signaling pathway in hESC, this study examines the expression and functional role of SHH during hESC self-renewal and differentiation. Here, we show the gene and protein expression of key components of the SHH signaling pathway in hESC and differentiated embryoid bodies. Despite the presence of functioning pathway components, SHH plays a minimal role in maintaining pluripotency and regulating proliferation of undifferentiated hESC. However, during differentiation with retinoic acid, a GLI-responsive luciferase assay and target genes PTCH1 and GLI1 expression reveal that the SHH signaling pathway is highly activated. Besides, addition of exogenous SHH to hESC differentiated as embryoid bodies increases the expression of neuroectodermal markers Nestin, SOX1, MAP2, MSI1, and MSX1, suggesting that SHH signaling is important during hESC differentiation toward the neuroectodermal lineage. Our findings provide a new insight in understanding the SHH signaling in hESC and the further development of hESC differentiation for regenerative medicine.
Collapse
|
15
|
Oh SKW, Choo ABH. Human embryonic stem cells: technological challenges towards therapy. Clin Exp Pharmacol Physiol 2007; 33:489-95. [PMID: 16700884 DOI: 10.1111/j.1440-1681.2006.04397.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. Human embryonic stem cells (hESC) hold promise for overcoming many diseases because they provide a potential source for many of the slow-growing cell types needed for effective tissue repair, such as the dopaminergic neural cells for Parkinson's disease or the pancreatic islet cells needed to relieve diabetic patients of their daily insulin injections. 2. Human embryonic stem cells can be characterized by several surface antigen markers, transcription factors and enzymes, as well as their ability to differentiate into cells representative of the three germ layers, both in vivo and in vitro. 3. Significant progress has been made in defining the feeder-free and serum-free conditions needed for the culture of hESC. The fibroblast growth factor-2 and transforming growth factor-b signalling pathways appear to be important in maintaining self-renewal and preventing differentiation, respectively. 4. Several important quality controls, including karyotyping, immunogenicity and murine viral assays, will have to be established to monitor the production of hESC for therapeutic purposes. 5. Methods of expansion and differentiation of hESC are still in their infancy and the efficiency of these processes needs to be significantly enhanced.
Collapse
|
16
|
Adewumi O, Aflatoonian B, Ahrlund-Richter L, Amit M, Andrews PW, Beighton G, Bello PA, Benvenisty N, Berry LS, Bevan S, Blum B, Brooking J, Chen KG, Choo ABH, Churchill GA, Corbel M, Damjanov I, Draper JS, Dvorak P, Emanuelsson K, Fleck RA, Ford A, Gertow K, Gertsenstein M, Gokhale PJ, Hamilton RS, Hampl A, Healy LE, Hovatta O, Hyllner J, Imreh MP, Itskovitz-Eldor J, Jackson J, Johnson JL, Jones M, Kee K, King BL, Knowles BB, Lako M, Lebrin F, Mallon BS, Manning D, Mayshar Y, McKay RDG, Michalska AE, Mikkola M, Mileikovsky M, Minger SL, Moore HD, Mummery CL, Nagy A, Nakatsuji N, O'Brien CM, Oh SKW, Olsson C, Otonkoski T, Park KY, Passier R, Patel H, Patel M, Pedersen R, Pera MF, Piekarczyk MS, Pera RAR, Reubinoff BE, Robins AJ, Rossant J, Rugg-Gunn P, Schulz TC, Semb H, Sherrer ES, Siemen H, Stacey GN, Stojkovic M, Suemori H, Szatkiewicz J, Turetsky T, Tuuri T, van den Brink S, Vintersten K, Vuoristo S, Ward D, Weaver TA, Young LA, Zhang W. Characterization of human embryonic stem cell lines by the International Stem Cell Initiative. Nat Biotechnol 2007; 25:803-16. [PMID: 17572666 DOI: 10.1038/nbt1318] [Citation(s) in RCA: 782] [Impact Index Per Article: 43.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Accepted: 05/31/2007] [Indexed: 11/09/2022]
Abstract
The International Stem Cell Initiative characterized 59 human embryonic stem cell lines from 17 laboratories worldwide. Despite diverse genotypes and different techniques used for derivation and maintenance, all lines exhibited similar expression patterns for several markers of human embryonic stem cells. They expressed the glycolipid antigens SSEA3 and SSEA4, the keratan sulfate antigens TRA-1-60, TRA-1-81, GCTM2 and GCT343, and the protein antigens CD9, Thy1 (also known as CD90), tissue-nonspecific alkaline phosphatase and class 1 HLA, as well as the strongly developmentally regulated genes NANOG, POU5F1 (formerly known as OCT4), TDGF1, DNMT3B, GABRB3 and GDF3. Nevertheless, the lines were not identical: differences in expression of several lineage markers were evident, and several imprinted genes showed generally similar allele-specific expression patterns, but some gene-dependent variation was observed. Also, some female lines expressed readily detectable levels of XIST whereas others did not. No significant contamination of the lines with mycoplasma, bacteria or cytopathic viruses was detected.
Collapse
|
17
|
Chen S, Choo ABH, Nai-Dy W, Heng-Phon T, Oh SKW. Knockdown of Oct-4 or Sox-2 Attenuates Neurogenesis of Mouse Embryonic Stem Cells. Stem Cells Dev 2007; 16:413-20. [PMID: 17610371 DOI: 10.1089/scd.2006.0099] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
We employed a stromal-derived inducing activity (SDIA) model of neurogenesis to investigate the effects of targeted knockdown of Oct-4 and Sox-2 by short interfering RNAs (siRNAs) in mouse embryonic stem (mES) cells. Quantitative real-time PCR showed 40-90% knockdown of specific transcripts with cognate Oct-4 or Sox-2 siRNA transfection compared to FAM-labeled negative control (FAM) siRNA or mock transfection and was confirmed at the protein level by western blot analyses. Upon differentiation using PA6 SDIA co-cultures, neurogenesis is significantly diminished in Oct-4 or Sox-2-targeted mES cells. It was observed that 45 +/- 12%, 65 +/- 13%, and 90 +/- 8% of the colonies were stained with neuron-specific beta-tubulin III in Oct-4, Sox-2, and FAM siRNA transfected mES cells, respectively, with similar results observed using neural inducing factors collected from the surface of PA6. Together, our results extend observations for a role of Oct-4 in SDIA and implicate a similar role for Sox-2.
Collapse
|
18
|
Oh SKW, Choo ABH. Human embryonic stem cell technology: large scale cell amplification and differentiation. Cytotechnology 2006; 50:181-90. [PMID: 19003078 PMCID: PMC2798940 DOI: 10.1007/s10616-005-3862-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2005] [Accepted: 10/07/2005] [Indexed: 12/11/2022] Open
Abstract
Embryonic stem cells (ESC) hold the promise of overcoming many diseases as potential sources of, for example, dopaminergic neural cells for Parkinson’s Disease to pancreatic islets to relieve diabetic patients of their daily insulin injections. While an embryo has the innate capacity to develop fully functional differentiated tissues; biologists are finding that it is much more complex to derive singular, pure populations of primary cells from the highly versatile ESC from this embryonic parent. Thus, a substantial investment in developing the technologies to expand and differentiate these cells is required in the next decade to move this promise into reality. In this review we document the current standard assays for characterising human ESC (hESC), the status of ‘defined’ feeder-free culture conditions for undifferentiated hESC growth, examine the quality controls that will be required to be established for monitoring their growth, review current methods for expansion and differentiation, and speculate on the possible routes of scaling up the differentiation of hESC to therapeutic quantities.
Collapse
|
19
|
Ding V, Choo ABH, Oh SKW. Deciphering the Importance of Three Key Media Components in Human Embryonic Stem Cell Cultures. Biotechnol Lett 2006; 28:491-5. [PMID: 16614931 DOI: 10.1007/s10529-006-0005-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Accepted: 01/06/2006] [Indexed: 12/21/2022]
Abstract
Development of a serum free, feeder-free (SFFF) culture platform for human embryonic stem cells (hESC) will be important for the expansion of hESC for future cell therapy applications. However, currently, culture of hESC consists of a combination of basal media, basic fibroblast growth factor (bFGF), serum replacer (SR) and conditioned media (CM) from feeders, and it is unclear which components of the mixture are absolutely critical in the maintenance of hESC. To evaluate the relative contributions of these media components in the development of SFFF culture, each was systematically eliminated and pluripotency assayed by dual embryonic stem cell markers, Oct-4 and TRA-1-60. We concluded that SR was the most critical component in the platform, followed by bFGF and CM produced by feeders, where down-regulation of Oct-4 occurred after 2, 5 and 5 passages, respectively, upon their withdrawal from the complete media.
Collapse
|
20
|
Oh SKW, Fong WJ, Teo Y, Tan HL, Padmanabhan J, Chin ACP, Choo ABH. High density cultures of embryonic stem cells. Biotechnol Bioeng 2005; 91:523-33. [PMID: 16044469 DOI: 10.1002/bit.20650] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Embryonic stem cells (ESC) have the unique ability to differentiate into a variety of tissue types. However, the realization of regenerative medicine will require the production of large quantities of ESC which subsequently have to be differentiated into the final phenotype. Thus, we sought to develop a simple and scaleable bioprocess to increase densities of ESC to achieve this goal. Using mouse embryonic stem cells (mESC) as a model, by combining automated feeding and culture of mESC on petriperm dishes, cell densities were enhanced up to 6.4 x 10(6) cells/cm2 compared to conventional petri dish culture which only reached 0.2 to 1.4 x 10(6) cells/cm2. It was found that mESC from all experiments maintained excellent viability, pluripotency, and genetic stability after growing for 6 days in petriperm cultures with automated feeding. The expression of Oct-4 transcription factor was observed in all cultures, mESC formed embryoid bodies in differentiated cultures and teratomas in SCID mice, confirming their pluripotency, and karyotype of the cultures was normal. This culture method was stable for routine passaging and a second mESC cell line was shown to perform in a similar manner on petriperm with automated feeding. This work represents an important step towards achieving high density cultures of ESC.
Collapse
|
21
|
Demangel C, Zhou J, Choo ABH, Shoebridge G, Halliday GM, Britton WJ. Single chain antibody fragments for the selective targeting of antigens to dendritic cells. Mol Immunol 2004; 42:979-85. [PMID: 15829289 DOI: 10.1016/j.molimm.2004.09.034] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2004] [Accepted: 09/21/2004] [Indexed: 10/26/2022]
Abstract
In order to target antigens (Ags) selectively to dendritic cells (DC), we derived single chain antibody fragments (scFvs) from NLDC-145 and N418, two monoclonal antibodies binding the mouse dendritic cell-restricted surface molecules DEC-205 and CD11c. Recombinant hexahistidine-tagged forms of the scFvs (scNLDC and scN418) were efficiently produced in a baculovirus expression system. Both scFvs bound DEC-205(+) Langerhans cells and CD11c(+) fetal skin-derived dendritic cells (FSDCs) comparably to their parental antibodies. Immunization of C57BL/6 mice with a DNA vaccine encoding a model protein antigen fused to scNLDC stimulated specific immune responses in both the humoral and cellular compartments, in contrast to DNA vaccines expressing scN418-targeted or untargeted antigen. Our results show that antigen targeting to DCs via a DEC-205 binding scFv leads to enhanced immunogenicity. Further, this work suggests that scFvs fused to protein antigens and delivered as DNA vaccines may provide a generic means for delivering vaccinal molecules to selected cell populations.
Collapse
|
22
|
Choo ABH, Padmanabhan J, Chin ACP, Oh SKW. Expansion of pluripotent human embryonic stem cells on human feeders. Biotechnol Bioeng 2004; 88:321-31. [PMID: 15486939 DOI: 10.1002/bit.20247] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Human embryonic stem cells (HES) hold great potential for regenerative medicine because of their ability to differentiate to any cell type. However, a limitation is that HES cells require a feeder layer to stay undifferentiated. Routinely, mouse embryonic fibroblast is used. However, for therapeutic applications, contamination with mouse cells may be considered unacceptable. In this study, we evaluated three commercially available human foreskin feeder (HF) lines for their ability to support HES cell growth in media supplemented with serum or serum replacer. HES cells on HF in serum replacer-supplemented media were cultured for >30 passages. They remained undifferentiated, maintained a normal karyotype, and continued to be positive for the pluripotent markers Oct-4, SOX-2, SSEA-4, GCTM-2, Tra-1-60, Tra-1-81, and alkaline phosphatase. In vivo, HES cells formed teratomas in SCID mouse models that represent the three embryonic germ layers. In contrast, HES cells cultured on HF in serum-supplemented media differentiated after three passages. Morphologically, the cells became cystic with a loss of intracellular Oct-4. We have successfully adapted and cultured undifferentiated HES cells on three human feeder lines for >30 passages. No difficulties were observed with the exception of serum in the media. This study reveals a safe and accessible source for feeders for HES cell research and potential therapeutic applications.
Collapse
|
23
|
Choo ABH, Dunn RD, Broady KW, Raison RL. Soluble expression of a functional recombinant cytolytic immunotoxin in insect cells. Protein Expr Purif 2002; 24:338-47. [PMID: 11922749 DOI: 10.1006/prep.2001.1589] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously described the production of a recombinant melittin-based cytolytic immunotoxin (IT), scFv-mel-FLAG, in bacterial cells. While the IT exhibited specific cytotoxicity for a human lymphoblastoid cell line, HMy2, yields from expression were low. Here, we describe a baculovirus expression system for the overexpression and secretion of scFv-mel-FLAG. A novel snake phospholipase A2 inhibitor signal peptide was used to aid in the secretion of the immunotoxin. Sf21 insect cells infected with the recombinant virus secreted soluble scFv-mel-FLAG into the culture medium from which it was purified directly on an affinity column. The final yield of scFv-mel-FLAG was estimated at 3-5 mg/L, which was an improvement of 30-fold compared to expression in the prokaryotic system. The cell binding characteristics of the recombinant IT were assessed by flow cytometry using the antigen expressing cell line HMy2. ScFv-mel-FLAG bound specifically to HMy2 cells in direct binding assays and this binding was completely inhibited in the presence of an excess of soluble antigen. Significant cytotoxicity for HMy2 cells, measured by leakage of cytosolic LDH, was also observed for the IT at a concentration of 60 pmol/10(4) cells. Cytotoxicity was concentration dependent and was specific for antigen-positive cells. Thus the baculovirus expression system, under the control of a novel secretion signal, can be used for the production of soluble and functional recombinant cytolytic immunotoxins. To our knowledge, this is the first report of expression of a recombinant immunotoxin in the baculovirus expression vector system.
Collapse
|
24
|
Oh SKW, Chua FKF, Choo ABH. Intracellular responses of productive hybridomas subjected to high osmotic pressure. Biotechnol Bioeng 1995; 46:525-35. [DOI: 10.1002/bit.260460605] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|