A human endothelial cell feeder system that efficiently supports the undifferentiated growth of mouse embryonic stem cells

Characterization of Mesenchymal Stem Cell Differentiation within Miniaturized 3D Scaffolds through Advanced Microscopy Techniques

Three-dimensional culture systems and suitable substrates topographies demonstrated to drive stem cell fate in vitro by mechanical conditioning. For example, the Nichoid 3D scaffold remodels stem cells and shapes nuclei, thus promoting stem cell expansion and stemness maintenance. However, the mechanisms involved in force transmission and in biochemical signaling at the basis of fate determination are not yet clear. Among the available investigation systems, confocal fluorescence microscopy using fluorescent dyes enables the observation of cell function and shape at the subcellular scale in vital and fixed conditions. Contrarily, nonlinear optical microscopy techniques, which exploit multi-photon processes, allow to study cell behavior in vital and unlabeled conditions. We apply confocal fluorescence microscopy, coherent anti-Stokes Raman scattering (CARS), and second harmonic generation (SHG) microscopy to characterize the phenotypic expression of mesenchymal stem cells (MSCs) towards adipogenic and chondrogenic differentiation inside Nichoid scaffolds, in terms of nuclear morphology and specific phenotypic products, by comparing these techniques. We demonstrate that the Nichoid maintains a rounded nuclei during expansion and differentiation, promoting MSCs adipogenic differentiation while inhibiting chondrogenesis. We show that CARS and SHG techniques are suitable for specific estimation of the lipid and collagenous content, thus overcoming the limitations of using unspecific fluorescent probes.

Two-photon polymerized "nichoid" substrates maintain function of pluripotent stem cells when expanded under feeder-free conditions

Background

The use of pluripotent cells in stem cell therapy has major limitations, mainly related to the high costs and risks of exogenous conditioning and the use of feeder layers during cell expansion passages.

Methods

We developed an innovative three-dimensional culture substrate made of “nichoid” microstructures, nanoengineered via two-photon laser polymerization. The nichoids limit the dimension of the adhering embryoid bodies during expansion, by counteracting cell migration between adjacent units of the substrate by its microarchitecture. We expanded mouse embryonic stem cells on the nichoid for 2 weeks. We compared the expression of pluripotency and differentiation markers induced in cells with that induced by flat substrates and by a culture layer made of kidney-derived extracellular matrix.

Results

The nichoid was found to be the only substrate, among those tested, that maintained the expression of the OCT4 pluripotency marker switched on and, simultaneously, the expression of the differentiation markers GATA4 and α-SMA switched off. The nichoid promotes pluripotency maintenance of embryonic stem cells during expansion, in the absence of a feeder layer and exogenous conditioning factors, such as the leukocyte inhibitory factor.

Conclusions

We hypothesized that the nichoid microstructures induce a genetic reprogramming of cells by controlling their cytoskeletal tension. Further studies are necessary to understand the exact mechanism by which the physical constraint provided by the nichoid architecture is responsible for cell reprogramming. The nichoid may help elucidate mechanisms of pluripotency maintenance, while potentially cutting the costs and risks of both feed-conditioning and exogenous conditioning for industrial-scale expansion of stem cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0387-z) contains supplementary material, which is available to authorized users.

Damage-inducible intragenic demethylation of the human TP53 tumor suppressor gene is associated with transcription from an alternative intronic promoter

Wild-type TP53 exons 5-8 contain CpG dinucleotides that are prone to methylation-dependent mutation during carcinogenesis, but the regulatory effects of methylation affecting these CpG sites are unclear. To clarify this, we first assessed site-specific TP53 CpG methylation in normal and transformed cells. Both DNA damage and cell ageing were associated with site-specific CpG demethylation in exon 5 accompanied by induction of a truncated TP53 isoform regulated by an adjacent intronic promoter (P2). We then synthesized novel synonymous TP53 alleles with divergent CpG content but stable encodement of the wild-type polypeptide. Expression of CpG-enriched TP53 constructs selectively reduced production of the full-length transcript (P1), consistent with a causal relationship between intragenic demethylation and transcription. 450K methylation comparison of normal (TP53-wildtype) and cancerous (TP53-mutant) human cells and tissues revealed focal cancer-associated declines in CpG methylation near the P1 transcription start site, accompanied by rises near the alternate exon 5 start site. These data confirm that site-specific changes of intragenic TP53 CpG methylation are extrinsically inducible, and suggest that human cancer progression is mediated in part by dysregulation of damage-inducible intragenic CpG demethylation that alters TP53 P1/P2 isoform expression. © 2015 The Authors. Molecular Carcinogenesis Published by Wiley Periodicals, Inc.

The importance of three-dimensional scaffold structure on stemness maintenance of mouse embryonic stem cells

Revealing the mechanisms of cell fate regulation is important for scientific research and stem cell-based therapy. The traditional two-dimensional (2D) cultured mES cells are in a very different 2D niche from the in vivo equivalent-inner cell mass (ICM). Because the cell fate decision could be regulated by many cues which could be impacted by geometry, the traditional 2D culture system would hamper us from understanding the in vivo situations correctly. Three-dimensional (3D) scaffold was believed to provide a 3D environment closed to the in vivo one. In this work, three different scaffolds were prepared for cell culture. Several characters of mES cells were changed under 3D scaffolds culture compared to 2D, and these changes were mainly due to the alteration in geometry but not the matrix. The self-renewal of mES cells was promoted by the introducing of dimensionality. The stemness maintenance of mES was supported by all three 3D scaffolds without feeder cells in the long-time culture. Our findings demonstrated that the stemness maintenance of mES cells was promoted by the 3D geometry of scaffolds and this would provide a promising platform for ES cell research.

Proteomic Profiling of Secreted Proteins for the Hematopoietic Support of Interleukin-Stimulated Human Umbilical Vein Endothelial Cells

Human umbilical cord vein endothelial cells (HUVECs) secrete a number of factors that greatly impact the proliferation and differentiation of hematopoietic stem and progenitor cells (HSPCs). These factors remain largely unknown. Here, we report on the most comprehensive proteomic profiling of the HUVEC secretome and identified 827 different secreted proteins. Two hundred and thirty-one proteins were found in all conditions, whereas 369 proteins were identified only under proinflammatory conditions following IL-1β, IL-3, and IL-6 stimulation. Thirteen proteins including complement factor b (CFb) were identified only under IL-1β and IL-3 conditions and may potentially represent HSPC proliferation factors. The combination of bioinformatics and gene ontology annotations indicates the role of the complement system and its activation. Furthermore, CFb was found to be transcriptionally strongly upregulated. Addition of complement component 5b-9 (C5b-9) monoclonal antibody to the stem cell expansion assay was capable of significantly reducing their proliferation. This study suggests a complement-mediated cross-talk between endothelial cells and HSPCs under proinflammatory conditions.

Autogenic feeder free system from differentiated mesenchymal progenitor cells, maintains pluripotency of the MEL-1 human embryonic stem cells

Human embryonic stem cells (hESc) are known for its pluripotency and self renewal capability, thus possess great potential in regenerative medicine. However, the lack of suitable xenofree extracellular matrix substrate inhibits further applications or the use of hESc in cell-based therapy. In this study, we described a new differentiation method, which generates a homogeneous population of mesenchymal progenitor cells (hESc-MPC) from hESc via epithelial-mesenchymal transition. The extracellular matrix (ECM) proteins from hESc-MPC had in turn supported the undifferentiated expansion of hESc. Immunocytochemistry and flow cytometry characterization of hESc-MPC revealed the presence of early mesenchymal markers. Tandem mass spectometry analysis of ECM produced by hESc-MPC revealed the presence of a mixture of extracellular proteins which includes tenascin C, fibronectin, and vitronectin. The pluripotency of hESc (MEL-1) cultured on the ECM was maintained as shown by the expression of pluripotent genes (FoxD3, Oct-4, Tdgf1, Sox-2, Nanog, hTERT, Rex1), protein markers (SSEA-3, SSEA-4, TRA-1-81, TRA-1-60, Oct-4) and the ability to differentiate into cells representative of ectoderm, endoderm and mesoderm. In summary, we have established a xeno-free autogenic feeder free system to support undifferentiated expansion of hESc, which could be of clinical relevance.

Human foreskin fibroblast produces interleukin-6 to support derivation and self-renewal of mouse embryonic stem cells

Introduction

Embryonic stem cells (ESCs) provide an attractive cell source for basic research and disease treatment. Currently, the common culture system for mouse ESC requires mouse embryonic fibroblast (MEF) as a feeder layer supplemented with leukemia inhibitory factor (LIF). The drawbacks associated with MEF and the cost of LIF have motivated exploration of new feeder cell types to maintain self-renewal of mouse ESCs without the need of exogenous LIF. However, why these feeder cells could maintain ESCs at the undifferentiated state independent of exogenous LIF is unclear.

Methods

We derived mouse ESC lines using human foreskin fibroblast (HFF) in the absence of exogenous LIF. We also examined the dependence of HFF on the JAK-Stat3 pathway to maintain ESC identities and explored the potential molecular basis for HFF to support self-renewal of ESCs.

Results

HFF supported mouse ESC self-renewal superiorly to MEFs. Using the HFF system, multiple lines of mouse ESCs were successfully derived without addition of exogenous LIF and any small molecular inhibitors. These ESCs had capacities to self-renew for a long period of time and to differentiate into various cell types of the three germ layers both in vitro and in vivo. Moreover, the ESCs participated in embryonic development and contributed to germ cell lineages in the chimeric mouse. At a molecular level, HFF was dependent on the JAK-Stat3 pathway to maintain ESC self-renewal. The high level of interleukin-6 (IL-6) produced by HFF might be responsible for the exogenous LIF-independent effect.

Conclusion

This study describes an efficient, convenient and economic system to establish and maintain mouse ESC lines, and provides insights into the functional difference in the support of ESC culture between MEF and HFF.

Expansion of human embryonic stem cells: a comparative study

OBJECTIVES

Human embryonic stem cells (hESC) are promising for tissue engineering (TE) purposes due to their unique properties. However, current standard mechanical passaging techniques limit rates of possible TE experiments, as it is difficult to obtain high enough numbers of the cells for experimentation. In this study, several dissociative solutions and application methods are tested for their applicability to, and influence on, hESC culture and expansion.

MATERIALS AND METHODS

Expansion of two hESC lines, H1 and VUB01, subjected to different passaging techniques, was evaluated. Four dissociative solutions - TrypLE™ Express, Trypsin-EDTA, Cell Dissociation Solution and Accutase™- were combined with two application protocols. As reference conditions, manual and bead-based passaging techniques were used.

RESULTS

Results showed that use of Cell Dissociation Solution in combination with a slow adaptation protocol, generated the best expansion profile for both cell lines. The hESC single cell lines remained pluripotent, had good expansion profiles and were capable of differentiation into representatives of all three germ layers. Reproducibility of the results was confirmed by adaptation for three other hESC lines.

CONCLUSION

Use of Cell Dissociation Solution, combined with slow adaptation protocol, allows a fast switch from the mechanical passaging technique to a single-cell split technique, generating stable and robust hESC cell lines, which allow for large scale expansion of hESC for TE purposes.

Liver sinusoidal endothelial cells support the survival and undifferentiated growth of the CGR8 mouse embryonic stem cell line: possible role of leukemia inhibitory factor (LIF)

Murine embryonic stem cells (muESC) are maintained and expanded in vitro by culturing in the presence of leukemia inhibitory factor (LIF) or by coculturing on murine embryonic fibroblast (MEF). Previously we have shown that liver sinusoidal endothelial cells (LSEC) promote the survival, proliferation and differentiation of hematopoietic stem cells. In the present study we investigated whether LSEC might promote the survival and undifferentiated growth of muESC. For these purposes, muESC (CGR8 cell line) were cultured on LSEC monolayers (muESC/LSEC) or in the presence of conditioned medium from LSEC cultures (muESC/LSEC-CM), both in the absence of LIF. Microscopic observation showed the growth of undifferentiated ESC colonies in both muESC/LSEC or muESC/LSEC-CM cultures. A significant reduction in the growth of undifferentiated ESC colonies was observed when ESC were cultured in LSEC-CM previously incubated with anti-LIF. RT-PCR and Western blot analysis showed that LSEC constitutively express LIF at the mRNA and protein level. At different times of culture, muESC were harvested and analyzed for the expression of embryonic markers (SSEA-1 and Oct-4) and differentiation capacity. Flow cytometry analysis showed the presence of a higher percentage of muESC (>90%) expressing SSEA-1 in muESC/LSEC-CM, as compared with muESC/LSEC cocultures. muESC obtained from both types of cultures formed embryoid bodies in vitro, and form teratomas in testicles of mice. These results provide the first evidence that LSEC support the in vitro survival, self-renewal, undifferentiated growth and differentiation capacity of the muESC CGR8 cell line.

The promotion of stemness and pluripotency following feeder-free culture of embryonic stem cells on collagen-grafted 3-dimensional nanofibrous scaffold

The components of extracellular matrix (ECM) may substitute for feeder layers that promote the self-renewal pathways in embryonic stem cells. Surface modification of electrospun nanofibrous scaffolds have been studied to closely resemble natural ECMs and support in vitro and in vivo proliferation, pluripotency and differentiation of stem cells. In this study, we analyzed the maintenance of stemness and pluripotency of the mouse embryonic stem cell (mESC) following feeder-free culture on collagen-grafted polyethersulfone (PES-COL) electrospun nanofibrous scaffold. Our results showed that, the mESCs cultured for seven passages on PES-COL scaffolds had a typical undifferentiated morphology, enhanced proliferation, stable diploid normal karyotype, and continued expression of stemness and pluripotency-associated markers, Oct-4, Nanog, SSEA-1, and Alkaline phosphatase (ALP) in comparison with PES scaffolds and gelatin-coated plate. Moreover, these cells retained their in vitro and in vivo pluripotency. Our results indicated the enhanced infiltration and teratoma formation of mESCs in PES-COL. Collagen-grafted polyethersulfone nanofibrous scaffold has potential for feeder-free culture of pluripotent stem cells because of its 3-dimensional structure and bioactivity which enhance pluripotency, proliferation, differentiation, and infiltration of embryonic stem cells.

Human fetal liver stromal cells that overexpress bFGF support growth and maintenance of human embryonic stem cells

In guiding hES cell technology toward the clinic, one key issue to be addressed is to culture and maintain hES cells much more safely and economically in large scale. In order to avoid using mouse embryonic fibroblasts (MEFs) we isolated human fetal liver stromal cells (hFLSCs) from 14 weeks human fetal liver as new human feeder cells. hFLSCs feeders could maintain hES cells for 15 passages (about 100 days). Basic fibroblast growth factor (bFGF) is known to play an important role in promoting self-renewal of human embryonic stem (hES) cells. So, we established transgenic hFLSCs that stably express bFGF by lentiviral vectors. These transgenic human feeder cells — bFGF-hFLSCs maintained the properties of H9 hES cells without supplementing with any exogenous growth factors. H9 hES cells culturing under these conditions maintained all hES cell features after prolonged culture, including the developmental potential to differentiate into representative tissues of all three embryonic germ layers, unlimited and undifferentiated proliferative ability, and maintenance of normal karyotype. Our results demonstrated that bFGF-hFLSCs feeder cells were central to establishing the signaling network among bFGF, insulin-like growth factor 2 (IGF-2), and transforming growth factor β (TGF-β), thereby providing the framework in which hES cells were instructed to self-renew or to differentiate. We also found that the conditioned medium of bFGF-hFLSCs could maintain the H9 hES cells under feeder-free conditions without supplementing with bFGF. Taken together, bFGF-hFLSCs had great potential as feeders for maintaining pluripotent hES cell lines more safely and economically.

The efficacy of human placenta as a source of the universal feeder in human and mouse pluripotent stem cell culture

The use of a mouse embryonic fibroblast (MEF) feeder for culture of embryonic stem cells (ESCs) is a widely accepted method, regardless of the ESCs' origin and type. In this study, we performed the undifferentiated propagation of human ES cell lines (hESCs, H1, and HSF6) and mouse ES cell lines (mESCs, D3, and CE3), which were previously maintained on an MEF feeder, using human placenta-derived fibroblast-like cell (HPC) feeders originated from chorionic villi of women who had undergone therapeutic abortion due to known maternal disease that is aggravated by pregnancy. Moreover, we tried to introduce the HPC feeder for the establishment of inducible pluripotent stem cells (iPSCs) from human placental mesenchymal stem cells (MSCs). On the HPC feeder we were able to propagate ESCs and iPSCs colonies as an undifferentiated state up to the 50th passage and 20th passage, respectively. Maintenance of undifferentiated ESCs was identified by the expression of ALP, SSEA-1, SSEA-4, TRA-81, TRA-60, Oct-4, Nanog, or Rex-1. Also, addition of leukemia inhibitory factor was not required for undifferentiated propagation of mESCs on the HPC feeder. The efficiency and expression of three germ layer markers of embryoid bodies (EBs) from ESCs were satisfactory in both the MEF and HPC group. EBs formed from iPSCs were scant, and differentiation to the three germ layers was identifiable by reverst transcription-polymerase chain reactio (RT-PCR) only in the HPC group. In conclusion, the HPC feeder can efficiently support the undifferentiated propagation of hESCs, mESCs, and iPSCs, suggesting that human placenta may be a useful source of universal feeder cells for hESC, mESC, and iPSC culture.