Embryoid body culture of mouse embryonic stem cells using microwell and micropatterned chips

Blastomeres of 8-cell mouse embryos differ in their ability to generate embryonic stem cells and produce lines with different transcriptional signatures

Embryonic stem cell (ESC) derivation from single blastomeres of 8-cell mouse embryos results in lower derivation rates than that from whole blastocysts, raising a biological question about the developmental potential of sister blastomeres. We aimed to assess the ability of 8-cell blastomeres to produce epiblast cells and ESC lines after isolation, and the properties of the resulting lines. Our results revealed unequal competence among sister blastomeres to produce ESC lines. At least half of the blastomeres possess a lower potential to generate ESCs, although culture conditions and blastomeres plasticity can redirect their non-pluripotent fate towards the epiblast lineage, allowing us to generate up to seven lines from the same embryo. Lines originated from the same embryo segregated into two groups according to their transcriptional signatures. While the expression of genes related to pluripotency and development was higher in one group, no differences were found in their trilineage differentiation ability. These results may help to improve our understanding of the ESC derivation process from single blastomeres and cell fate determination in the preimplantation mouse embryos.

Promotion of Cyst Formation from a Renal Stem Cell Line Using Organ-Specific Extracellular Matrix Gel Format Culture System

Researchers have long awaited the technology to develop an in vitro kidney model. Here, we establish a rapid fabricating technique for kidney-like tissues (cysts) using a combination of an organ-derived extracellular matrix (ECM) gel format culture system and a renal stem cell line (CHK-Q cells). CHK-Q cells, which are spontaneously immortalized from the renal stem cells of the Chinese hamster, formed renal cyst-like structures in a type-I collagen gel sandwich culture on day 1 of culture. The cysts fused together and expanded while maintaining three-dimensional structures. The expression of genes related to kidney development and maturation was increased compared with that in a traditional monolayer. Under the kidney-derived ECM (K-ECM) gel format culture system, cyst formation and maturation were induced rapidly. Gene expressions involved in cell polarities, especially for important material transporters (typical markers Slc5a1 and Kcnj1), were restored. K-ECM composition was an important trigger for CHK-Q cells to promote kidney-like tissue formation and maturation. We have established a renal cyst model which rapidly expressed mature kidney features via the combination of K-ECM gel format culture system and CHK-Q cells.

Advancing models of neural development with biomaterials

Human pluripotent stem cells have emerged as a promising in vitro model system for studying the brain. Two-dimensional and three-dimensional cell culture paradigms have provided valuable insights into the pathogenesis of neuropsychiatric disorders, but they remain limited in their capacity to model certain features of human neural development. Specifically, current models do not efficiently incorporate extracellular matrix-derived biochemical and biophysical cues, facilitate multicellular spatio-temporal patterning, or achieve advanced functional maturation. Engineered biomaterials have the capacity to create increasingly biomimetic neural microenvironments, yet further refinement is needed before these approaches are widely implemented. This Review therefore highlights how continued progression and increased integration of engineered biomaterials may be well poised to address intractable challenges in recapitulating human neural development.

Effects of Fruquintinib on the Pluripotency Maintenance and Differentiation Potential of Mouse Embryonic Stem Cells

Mouse embryonic stem cells (mESCs) can maintain self-renewal and differentiate into any cell type of the three primary germ layers. The vascular endothelial growth factor (VEGF) is involved in the regulation of mESC differentiation and induces the activation of a series of kinase responses and several cell signaling pathways by binding to its respective transmembrane receptors, vascular endothelial growth factor receptor VEGFR1, and VEGFR2. Fruquintinib is a selective inhibitor of VEGFRs, and we used it to investigate the effects on the maintenance of pluripotency and differentiation potential of mESCs in this study. Our results showed that fruquintinib-treated cells expressed higher levels of pluripotent markers, including Oct4, Nanog, Sox2, and Esrrb under serum and leukemia inhibitory factor (LIF) condition, whereas the expression of phosphorylated Erk1/2 was restricted. Mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (MEK) signaling inhibitor (PD0325901) and glycogen synthase kinase 3 (GSK3) signaling inhibitor (CHIR99021) (also known as 2i) enable cells to maintain naive pluripotency with LIF, and fruquintinib can also promote cells to maintain naive pluripotent state even under serum/LIF condition, whereas VEGF addition limits the pluripotency characteristics in serum/LIF mESCs. Furthermore, fruquintinib could inhibit the three-germ layer establishment in embryoid body formation and maintain the undifferentiated characteristics of mESCs, indicating that fruquintinib could promote the maintenance of naive pluripotency and inhibit early differentiation programs.

Gene expression patterns of neurotrophin receptors during neuronal differentiation of human exfoliated deciduous teeth

OBJECTIVE

In the current study, we aimed to investigate the expression profile of TrkA, TrkB, TrkC, and p75NTR neurotrophin receptors because of their roles in the functional differentiation of human exfoliated deciduous teeth (SHED) cells into neural-like cells before and after differentiation of SHED cells into neural-like cells.

DESIGN

Total RNAs isolated from dental pulp tissue, SHED cells, and neural-like cells were reverse transcribed into complementary DNA. Neurotrophin receptor expression at mRNA and protein levels were compared in these three cell types by means of real-time PCR and western blot methods.

RESULTS

TrkA mRNA increased (713.6 ± 251.5) significantly (p < 0.01) in neural-like cells difference from SHED and TrkB mRNA enhanced to 3618 times in these cells. The expression pattern of TrkC was very similar to the pattern of TrkA, and B. p75NTR mRNA increased 41.99 ± 21.61 fold in neural-like cells and 9.805 ± 4.06 fold in SHED cells. Almost the same pattern was observed for the expression of these receptors at the protein levels. Alterations with different grades and trends in neurotrophin receptors mRNA and protein expression levels were observed in these cells.

CONCLUSION

Neurotrophin receptors are important in the existence and differentiation of SHED cells into neuron cells. Therefore, because of the neurogenic potential and accessibility of SHED cells, derived cells from SHED cells can be distinguished as an ideal source for tissue engineering.

Enhanced sample filling and discretization in thermoplastic 2D microwell arrays using asymmetric contact angles

Sample filling and discretization within thermoplastic 2D microwell arrays is investigated toward the development of low cost disposable microfluidics for passive sample discretization. By using a high level of contact angle asymmetry between the filling channel and microwell surfaces, a significant increase in the range of well geometries that can be successfully filled is revealed. The performance of various array designs is characterized numerically and experimentally to assess the impact of contact angle asymmetry and device geometry on sample filling and discretization, resulting in guidelines to ensure robust microwell filling and sample isolation over a wide range of well dimensions. Using the developed design rules, reliable and bubble-free sample filling and discretization is achieved in designs with critical dimensions ranging from 20 μm to 800 μm. The resulting devices are demonstrated for discretized nucleic acid amplification by performing loop-mediated isothermal amplification for the detection of the mecA gene associated with methicillin-resistant Staphylococcus aureus.

A multiple-funnels cell culture insert for the scale-up production of uniform cell spheroids

Introduction

Formation of cell spheres is an important procedure in biomedical research. A large number of high-quality cell spheres of uniform size and shape are required for basic studies and therapeutic applications. Conventional approaches, including the hanging drop method and suspension culture, are used for cell sphere production. However, these methods are time consuming, cell spheres cannot be harvested easily, and it is difficult to control the size and geometry of cell spheres. To resolve these problems, a novel multiple-funnel cell culture insert was designed for size controlling, easy harvesting, and scale-up production of cell spheres.

Methods

The culture substrate has 680 micro-funnels with a 1-mm width top, 0.89 mm depth, and 0.5 mm square bottom. Mouse embryonic stem cells were used to test the newly developed device. The seeded embryonic stem cells settled at the downward medium surface toward the bottom opening and aggregated as embryoid bodies (EBs). For cell sphere harvest, the bottom of the culture insert was put in contact with the medium surface in another culture dish, and the medium in the device flowed down with cell spheres by hydrostatic pressure.

Results

Compact cell spheres with uniform size and shape were collected easily. The diameter of the spheres could be controlled by adjusting the seeding cell density. Spontaneous neural differentiation (nestin and Tju1) and retinoic acid-induced endodermal differentiation (Pdx-1 and insulin I) were improved in the EBs produced using the new insert compared to those in EBs produced by suspension culture.

Conclusions

This novel cell culture insert shall improve future studies of cell spheres and benefit clinical applications of cell therapy.

A Novel, Well-Resolved Direct Laser Bioprinting System for Rapid Cell Encapsulation and Microwell Fabrication

A direct laser bioprinting (DLBP) system is introduced in this work. The DLBP system applies visible-laser-induced photo-crosslinking at a wavelength of 405 nm using the photoinitiator VA-086. It is shown that such a system can fabricate vertical structures with fine features (less than 50 µm) and high cell viability (greater than 95%). Experimental characterizations and theoretical simulations are presented, and good agreement is seen between the experiments and theory. The DLBP system is applied to the fabrication of (1) cell-laden hydrogel microgrids, (2) hydrogel microwells, as well as a test of (3) cell encapsulation, and (4) cell seeding. The DLBP system is found to be a promising tool for bioprinting.

Asymmetricity Between Sister Cells of Pluripotent Stem Cells at the Onset of Differentiation

Various somatic stem cells divide asymmetrically; however, it is not known whether embryonic stem cells (ESCs) divide symmetrically or asymmetrically, not only while maintaining an undifferentiated state but also at the onset of differentiation. In this study, we observed single ESCs using time-lapse imaging and compared sister cell pairs derived from the same mother cell in either the maintenance or differentiation medium. Mouse ESCs were cultured on E-cadherin-coated glass-based dishes, which allowed us to trace single cells. The undifferentiated cell state was detected by green fluorescent protein (GFP) expression driven by the Nanog promoter, which is active only in undifferentiated cells. Cell population analysis using flow cytometry showed that the peak width indicating distribution of GFP expression broadened when cells were transferred to the differentiation medium compared to when they were in the maintenance medium. This finding suggested that the population of ESCs became more heterogeneous at the onset of differentiation. Using single-cell analysis by time-lapse imaging, we found that although the total survival ratio decreased by changing to differentiation medium, the one-live-one-dead ratio of sister cell pairs was smaller compared with randomly chosen non-sister cell pairs, defined as an unsynchronized cell pair control, in both media. This result suggested that sister cell pairs were more positively synchronized with each other compared to non-sister cell pairs. The differences in interdivision time (the time interval between mother cell division and the subsequent cell division) between sister cells was smaller than that between non-sister cell pairs in both media, suggesting that sister cells divided synchronously. Although the difference in Nanog-GFP intensity between sister cells was smaller than that between non-sister cells in the maintenance medium, it was the same in differentiation medium, suggesting asymmetrical Nanog-GFP intensity. These data suggested that ESCs may divide asymmetrically at the onset of differentiation resulting in heterogeneity.

Advances in microfluidic devices made from thermoplastics used in cell biology and analyses

Silicon and glass were the main fabrication materials of microfluidic devices, however, plastics are on the rise in the past few years. Thermoplastic materials have recently been used to fabricate microfluidic platforms to perform experiments on cellular studies or environmental monitoring, with low cost disposable devices. This review describes the present state of the development and applications of microfluidic systems used in cell biology and analyses since the year 2000. Cultivation, separation/isolation, detection and analysis, and reaction studies are extensively discussed, considering only microorganisms (bacteria, yeast, fungi, zebra fish, etc.) and mammalian cell related studies in the microfluidic platforms. The advantages/disadvantages, fabrication methods, dimensions, and the purpose of creating the desired system are explained in detail. An important conclusion of this review is that these microfluidic platforms are still open for research and development, and solutions need to be found for each case separately.

Compartmentalized microfluidic perfusion system to culture human induced pluripotent stem cell aggregates

Microfluidic perfusion systems enable small-volume cell cultures under precisely controlled microenvironments, and are typically developed for cell-based high-throughput screening. However, most such systems are designed to manipulate dissociated single cells, not cell aggregates, and are thus unsuitable to induce differentiation in human induced pluripotent stem cells (hiPSCs), which is conventionally achieved by using cell aggregates to increase cell-cell interactions. We have now developed a compartmentalized microfluidic perfusion system with large flow channels to load, culture, and observe cell aggregates. Homogeneously sized cell aggregates to be loaded into the device were prepared by shredding flat hiPSC colonies into squares. These aggregates were then seeded into microchambers coated with fibronectin and bovine serum albumin (BSA) to establish adherent and floating cultures, respectively, both of which are frequently used to differentiate hiPSCs. However, the number of aggregates loaded in fibronectin-coated microchambers was much lower than in BSA-coated microchambers, suggesting that fibronectin traps cell aggregates before they reach the chambers. Accordingly, hiPSCs that reached the microchambers subsequently adhered. In contrast, BSA-coated microchambers did not allow cell aggregates to adhere, but were sufficiently deep to prevent cell aggregates from flowing out during perfusion of media. Immunostaining for markers of undifferentiated cells showed that cultures on both fibronectin- and BSA-coated microchambers were successfully established. Notably, we found that floating aggregates eventually adhered to surfaces coated with BSA upon differentiation, and that differentiation depends on the initial size of aggregates. Collectively, these results suggest that the microfluidic system is suitable for manipulating hiPSC aggregates in compartmentalized microchambers.

3-D Microwell Array System for Culturing Virus Infected Tumor Cells

Cancer cells have been increasingly grown in pharmaceutical research to understand tumorigenesis and develop new therapeutic drugs. Currently, cells are typically grown using two-dimensional (2-D) cell culture approaches, where the native tumor microenvironment is difficult to recapitulate. Thus, one of the main obstacles in oncology is the lack of proper infection models that recount main features present in tumors. In recent years, microtechnology-based platforms have been employed to generate three-dimensional (3-D) models that better mimic the native microenvironment in cell culture. Here, we present an innovative approach to culture Kaposi’s sarcoma-associated herpesvirus (KSHV) infected human B cells in 3-D using a microwell array system. The results demonstrate that the KSHV-infected B cells can be grown up to 15 days in a 3-D culture. Compared with 2-D, cells grown in 3-D had increased numbers of KSHV latency-associated nuclear antigen (LANA) dots, as detected by immunofluorescence microscopy, indicating a higher viral genome copy number. Cells in 3-D also demonstrated a higher rate of lytic reactivation. The 3-D microwell array system has the potential to improve 3-D cell oncology models and allow for better-controlled studies for drug discovery.

Self-organizing human cardiac microchambers mediated by geometric confinement

Tissue morphogenesis and organ formation are the consequences of biochemical and biophysical cues that lead to cellular spatial patterning in development. To model such events in vitro, we use PEG-patterned substrates to geometrically confine human pluripotent stem cell colonies and spatially present mechanical stress. Modulation of the WNT/β-catenin pathway promotes spatial patterning via geometric confinement of the cell condensation process during epithelial–mesenchymal transition, forcing cells at the perimeter to express an OCT4+ annulus, which is coincident with a region of higher cell density and E-cadherin expression. The biochemical and biophysical cues synergistically induce self-organizing lineage specification and creation of a beating human cardiac microchamber confined by the pattern geometry. These highly defined human cardiac microchambers can be used to study aspects of embryonic spatial patterning, early cardiac development and drug-induced developmental toxicity.

Organogenesis is orchestrated by biochemical and biophysical stimuli. Here, Ma et al. generate a micro-patterned surface that provides mechanical cues which, when combined with biochemical signals, drive human pluripotent stem cells' differentiation into beating cardiac microchambers resembling primitive hearts.

Imprinted expression in cystic embryoid bodies shows an embryonic and not an extra-embryonic pattern

A large subset of mammalian imprinted genes show extra-embryonic lineage (EXEL) specific imprinted expression that is restricted to placental trophectoderm lineages and to visceral yolk sac endoderm (ysE). Isolated ysE provides a homogenous in vivo model of a mid-gestation extra-embryonic tissue to examine the mechanism of EXEL-specific imprinted gene silencing, but an in vitro model of ysE to facilitate more rapid and cost-effective experiments is not available. Reports indicate that ES cells differentiated into cystic embryoid bodies (EBs) contain ysE, so here we investigate if cystic EBs model ysE imprinted expression. The imprinted expression pattern of cystic EBs is shown to resemble fetal liver and not ysE. To investigate the reason for this we characterized the methylome and transcriptome of cystic EBs in comparison to fetal liver and ysE, by whole genome bisulphite sequencing and RNA-seq. Cystic EBs show a fetal liver pattern of global hypermethylation and low expression of repeats, while ysE shows global hypomethylation and high expression of IAPEz retroviral repeats, as reported for placenta. Transcriptome analysis confirmed that cystic EBs are more similar to fetal liver than ysE and express markers of early embryonic endoderm. Genome-wide analysis shows that ysE shares epigenetic and repeat expression features with placenta. Contrary to previous reports, we show that cystic EBs do not contain ysE, but are more similar to the embryonic endoderm of fetal liver. This explains why cystic EBs reproduce the imprinted expression seen in the embryo but not that seen in the ysE.

Effect of separation distance on the growth and differentiation of mouse embryoid bodies in micropatterned cultures

Embryoid body (EB) culture has been widely used for in vitro differentiation of embryonic stem (ES) cells. Micropatterning of cultures is a promising technique for regulating EB development, because it allows for controlling the EB size and the distance between neighboring EBs. In this study, we examined the relationship of EB separation distance to their growth and differentiation using a micropatterned chip. The basic chip design consisted of 91 gelatin spots (300 μm in diameter) in a hexagonal arrangement on a glass substrate that served as the cell adhesion area; the region without gelatin spots was modified with polyethylene glycol to create the non-adhesion area. Two similar chips were fabricated with distances between gelatin spots of 500 and 1500 μm. Mouse ES cells adhered on the gelatin spots and then proliferated to form EBs. When the EB-EB distance was at 1500 μm, their size and the expression of developmental gene markers were almost the same for all EBs on the chip. This indicated that interference between neighboring EBs was avoided. In contrast, when the EB-EB distance was at 500 μm, the size of EBs located in the inside region of the chip was smaller than that in the outside region. Additionally, in the inside region, hepatic differentiation of EB cells was increased over cardiac and vascular differentiation. These results indicate that the distance between EBs is an important factor in the regulation of their growth and differentiation.

Microwell arrays for uniform-sized embryoid body-mediated endothelial cell differentiation

Embryonic stem (ES) cell is of great interest cell source in regenerating tissue constructs. We hypothesized that the interaction of cell-extracellular matrices (ECMs) would enable the control of ES cell differentiation pathway. We fabricated the hydrogel microwell array system to regulate uniform-sized embryoid bodies (EBs) and replate into various ECM components (e.g., gelatin, collagen I, fibronectin, laminin, and Matrigel). We demonstrated that collagen I and laminin largely induced ES cell-derived endothelial cell differentiation compared to gelatin. We also characterized ECMs-dependent endothelial cell differentiation by evaluating the endothelial gene expression, showing that Flk1 endothelial gene was highly expressed on collagen I. We also demonstrated the effect of the integrin on uniform-sized EBs-derived endothelial cell differentiation, showing that integrin α1 was largely expressed on laminin. Therefore, the cell-ECM interaction could be potentially powerful for controlling the uniform-sized EBs-derived endothelial cell differentiation.

Expression of BAF57 in ovarian cancer cells and drug sensitivity

The SMARCE1 (SWI / SNF-related, matrix-associated, and actin-dependent regulator of chromatin, subfamily e, member 1) encodes BAF57 protein. Previously, we reported that BAF57 is a predictive marker of endometrial carcinoma. In this study, we investigated BAF57 expression in ovarian cancer cell lines and their sensitivities to cisplatin, doxorubicin, paclitaxel, and 5-fluorouracil. BAF57 expression was strongly correlated with sensitivities to cisplatin, doxorubicin, and 5-fluorouracil in 10 ovarian cancer cell lines. Paclitaxel sensitivity was also correlated with BAF57 expression, but without significance. In A2780 ovarian cancer cells, knockdown of BAF57 using specific siRNA increased cell cycle arrest at G₁ phase and the sensitivities to these anticancer agents. cDNA microarray analysis of A2780 cells transfected with BAF57 siRNA showed that 134 genes were positively regulated by BAF57, including ATP-binding cassette, sub-family G (WHITE), member 2 (ABCG2) encoding breast cancer resistance protein (BCRP). We confirmed that knockdown of BAF57 decreased BCRP expression in ovarian cancer cells by Western blot analysis, and that ABCG2 gene expression might be regulated transcriptionally. These results suggested that BAF57 is involved in ovarian cancer cell growth and sensitivity to anticancer agents, and that BAF57 may be a target for ovarian cancer therapy.

A method to recapitulate early embryonic spatial patterning in human embryonic stem cells

Embryos allocate cells to the three germ layers in a spatially ordered sequence. Human embryonic stem cells (hESCs) can generate the three germ layers in culture; however, differentiation is typically heterogeneous and spatially disordered. We show that geometric confinement is sufficient to trigger self-organized patterning in hESCs. In response to BMP4, colonies reproducibly differentiated to an outer trophectoderm-like ring, an inner ectodermal circle and a ring of mesendoderm expressing primitive-streak markers in between. Fates were defined relative to the boundary with a fixed length scale: small colonies corresponded to the outer layers of larger ones. Inhibitory signals limited the range of BMP4 signaling to the colony edge and induced a gradient of Activin-Nodal signaling that patterned mesendodermal fates. These results demonstrate that the intrinsic tendency of stem cells to make patterns can be harnessed by controlling colony geometries and provide a quantitative assay for studying paracrine signaling in early development.

Effect of single-oocyte culture system on in vitro maturation and developmental competence in mice

Purpose

To investigate whether single-culture systems influence the quality of in vitro-matured oocytes, we examined the maturation and developmental competence of oocytes obtained by grouped in vitro maturation (IVM) or single IVM.

Methods

In vitro-matured oocytes were obtained using the culture drop (CD) method for the grouped IVM experiments, and the CD and hanging drop (HD) method for the single IVM experiments. To evaluate oocyte developmental competence, we performed in vitro fertilization and culture, and counted the number of blastocysts. To evaluate the oocyte cytoplasmic maturation, we measured the maturation promoting factor (MPF) expression levels.

Results

Oocytes cultured singly had lower maturity and developmental competence than the grouped IVM oocytes. However, enhanced oocyte fertility and blastocyst quality was achieved by the HD single IVM method. Additionally, the MPF activity level increased in all culture methods, compared to the control; however, it lagged behind nuclear maturation.

Conclusions

These results suggest that the HD method is efficient for single IVM.

Detachably assembled microfluidic device for perfusion culture and post-culture analysis of a spheroid array

Microfluidic devices permit perfusion culture of three-dimensional (3D) tissue, mimicking the flow of blood in vascularized 3D tissue in our body. Here, we report a microfluidic device composed of a two-part microfluidic chamber chip and multi-microwell array chip able to be disassembled at the culture endpoint. Within the microfluidic chamber, an array of 3D tissue aggregates (spheroids) can be formed and cultured under perfusion. Subsequently, detailed post-culture analysis of the spheroids collected from the disassembled device can be performed. This device facilitates uniform spheroid formation, growth analysis in a high-throughput format, controlled proliferation via perfusion flow rate, and post-culture analysis of spheroids. We used the device to culture spheroids of human hepatocellular carcinoma (HepG2) cells under two controlled perfusion flow rates. HepG2 spheroids exhibited greater cell growth at higher perfusion flow rates than at lower perfusion flow rates, and exhibited different metabolic activity and mRNA and protein expression under the different flow rate conditions. These results show the potential of perfusion culture to precisely control the culture environment in microfluidic devices. The construction of spheroid array chambers allows multiple culture conditions to be tested simultaneously, with potential applications in toxicity and drug screening.

Generating size-controlled embryoid bodies using laser direct-write

Embryonic stem cells (ESCs) have the potential to self-renew and differentiate into any specialized cell type. One common method to differentiate ESCs in vitro is through embryoid bodies (EBs), three-dimensional cellular aggregates that spontaneously self-assemble and generally express markers for the three germ layers, endoderm, ectoderm, and mesoderm. It has been previously shown that both EB size and 2D colony size each influence differentiation. We hypothesized that we could control the size of the EB formed by mouse ESCs (mESCs) by using a cell printing method, laser direct-write (LDW), to control both the size of the initial printed colony and the local cell density in printed colonies. After printing mESCs at various printed colony sizes and printing densities, two-way ANOVAs indicated that the EB diameter was influenced by printing density after three days (p = 0.0002), while there was no effect of the printed colony diameter on the EB diameter at the same timepoint (p = 0.74). There was no significant interaction between these two factors. Tukey's honestly significant difference test showed that high-density colonies formed significantly larger EBs, suggesting that printed mESCs quickly aggregate with nearby cells. Thus, EBs can be engineered to a desired size by controlling printing density, which will influence the design of future differentiation studies. Herein, we highlight the capacity of LDW to control the local cell density and colony size independently, at prescribed spatial locations, potentially leading to better stem cell maintenance and directed differentiation.

Novel triblock co-polymer nanofibre system as an alternative support for embryonic stem cells growth and pluripotency

Conventionally, embryonic stem cells (ESCs) are cultured on gelatin or over a mitotically inactivated monolayer of mouse embryonic fibroblasts (MEFsi). Considering the lack of versatile, non-animal-derived and inexpensive materials for that purpose, we aimed to find a biomaterial able to support ESC growth in a pluripotent state that avoids the need for laborious and time-consuming MEFsi culture in parallel with mouse ESC (mESC) culture. Undifferentiated mESCs were cultured in a new nanofibre material designed for ESC culture, which is based on the self-assembly of a triblock co-polymer, poly(ethyleneglycol-β-trimethylsilyl methacrylate-β-methacrylic acid), conjugated with the peptide glycine-arginine-glycine-aspartate-serine, to evaluate its potential application in ESC research. The morphology, proliferation, viability, pluripotency and differentiation potential of mESCs were assessed. Compared to conventional stem cell culture methodologies, the nanofibres promoted a higher increase in mESCs number, enhanced pluripotency and were able to support differentiation after long-term culture. This newly developed synthetic system allows the elimination of animal-derived matrices and provides an economic method of ESC culture, made of a complex network of nanofibres in a scale similar to native extracellular matrices, where the functional properties of the cells can be observed and manipulated. Copyright © 2013 John Wiley & Sons, Ltd.

Size Regulation of Chondrocyte Spheroids Using a PDMS-Based Cell Culture Chip

Cartilage self-repair is limited due to a lack of blood supply and the low mitosis rate of chondrocytes. A tissue engineering approach using cells and biomaterials has the potential to treat cartilage injury. Threedimensional cellular aggregates are an excellent model for mimicking condensation and chondrogenic differentiation in vitro. We developed a technique for constructing spheroids utilizing a polydimethylsiloxane (PDMS)-based culture chip. The objective of this study is to determine how the initial cell density on a culture chip affects the chondrogenic ATDC5 cell differentiation. We demonstrate how culture chips having arrays of multicavities are able to generate high numbers of uniform spheroids rapidly and simultaneously with narrow size distribution. Spheroids are collected easily and noninvasively. Higher cell seeding density on the culture chip enhances chondrogenic cell differentiation. These results suggest the usefulness of this chip in engineering 3D cellular constructs with high functionality for tissue engineering.

Characterization of mouse embryoid bodies cultured on microwell chips with different well sizes

Microwell chip culture is a promising technique for the generation of homogenous embryoid bodies (EBs). In this study, we focused on the relationship between microwell size and mouse EB properties. The basic chip design was 195 microwells in a triangular arrangement on a polymethylmethacrylate plate with a surface modified by polyethylene glycol to render it nonadhesive, and 4 similar chips were fabricated with microwell diameters of 400, 600, 800, and 1000 μm. The cell proliferation rate of EBs in larger microwells was higher than that of EBs in smaller microwells. The decrease in the expression levels of undifferentiated marker genes (Oct3/4 and Nanog) in larger microwells was faster than that in smaller microwells. The expression of hepatic (transthyretin and alpha-fetoprotein), cardiac (Nkx2.5 and alpha-myosin heavy chain), and vascular (fetal liver kinase-1; Flk1) markers in larger microwells was higher than that in smaller microwells. The expression levels of differentiation markers except Flk1 in the chip with a diameter of 1000 μm were similar to those in hanging drop culture. However, Flk1 expression in microwell chip was markedly lower than that in hanging drop culture, suggesting that microwell chip culture promotes differentiation of hepatic and cardiac lineages. Furthermore, glucose consumption and lactate production were higher in smaller microwells, suggesting that the culture proceeds under anaerobic conditions in smaller microwells. These results indicate that the difference in microwell size affects the proliferation and differentiation of embryonic stem cells, and that microwell culture is a promising technique to control EB properties.

Multiparameter analyses of three-dimensionally cultured tumor spheroids based on respiratory activity and comprehensive gene expression profiles

Multicellular spheroids of human breast cancer cells (MCF-7) formed with two different three-dimensional (3D) culture methods were evaluated in detail on the basis of respiratory activity and high-throughput gene expression analysis. The spheroids formed with poly(dimethylsiloxane) (PDMS) microwell arrays indicated significant restriction of the spheroid size, whereas their respiratory activity was 2-fold greater than that formed with the hanging drop culture method. Fluidigm BioMark dynamic array was used for comprehensive and quantitative real-time polymerase chain reaction (qRT-PCR) analysis on the samples whose respiratory activity had been measured. Genes involved in cellular senescence and glucose metabolism indicated significantly higher values for the PDMS microwell culture method than for the hanging drop culture method (P<0.05). Interestingly, samples formed with the PDMS microwell culture method showed stronger responses for glycolysis than those formed with the hanging drop method. These results illustrate the power of multiparameter analysis to characterize multicellular spheroids cultured in different microenvironments even if they have the same morphology.

Spatial pattern dynamics of 3D stem cell loss of pluripotency via rules-based computational modeling

Pluripotent embryonic stem cells (ESCs) have the unique ability to differentiate into cells from all germ lineages, making them a potentially robust cell source for regenerative medicine therapies, but difficulties in predicting and controlling ESC differentiation currently limit the development of therapies and applications from such cells. A common approach to induce the differentiation of ESCs in vitro is via the formation of multicellular aggregates known as embryoid bodies (EBs), yet cell fate specification within EBs is generally considered an ill-defined and poorly controlled process. Thus, the objective of this study was to use rules-based cellular modeling to provide insight into which processes influence initial cell fate transitions in 3-dimensional microenvironments. Mouse embryonic stem cells (D3 cell line) were differentiated to examine the temporal and spatial patterns associated with loss of pluripotency as measured through Oct4 expression. Global properties of the multicellular aggregates were accurately recapitulated by a physics-based aggregation simulation when compared to experimentally measured physical parameters of EBs. Oct4 expression patterns were analyzed by confocal microscopy over time and compared to simulated trajectories of EB patterns. The simulations demonstrated that loss of Oct4 can be modeled as a binary process, and that associated patterns can be explained by a set of simple rules that combine baseline stochasticity with intercellular communication. Competing influences between Oct4+ and Oct4- neighbors result in the observed patterns of pluripotency loss within EBs, establishing the utility of rules-based modeling for hypothesis generation of underlying ESC differentiation processes. Importantly, the results indicate that the rules dominate the emergence of patterns independent of EB structure, size, or cell division. In combination with strategies to engineer cellular microenvironments, this type of modeling approach is a powerful tool to predict stem cell behavior under a number of culture conditions that emulate characteristics of 3D stem cell niches.

Polyester μ-assay chip for stem cell studies

The application of microfluidic technologies to stem cell research is of great interest to biologists and bioengineers. This is chiefly due to the intricate ability to control the cellular environment, the reduction of reagent volume, experimentation time and cost, and the high-throughput screening capabilities of microscale devices. Despite this importance, a simple-to-use microfluidic platform for studying the effects of growth factors on stem cell differentiation has not yet emerged. With this consideration, we have designed and characterized a microfluidic device that is easy to fabricate and operate, yet contains several functional elements. Our device is a simple polyester-based microfluidic chip capable of simultaneously screening multiple independent stem cell culture conditions. Generated by laser ablation and stacking of multiple layers of polyester film, this device integrates a 10 × 10 microwell array for cell culture with a continuous perfusion system and a non-linear concentration gradient generator. We performed numerical calculations to predict the gradient formation and calculate the shear stress acting on the cells inside the device. The device operation was validated by culturing murine embryonic stem cells inside the microwells for 5 days. Furthermore, we showed the ability to maintain the pluripotency of stem cell aggregates in response to concentrations of leukemia inhibitory factor ranging from 0 to ∼1000 U/ml. Given its simplicity, fast manufacturing method, scalability, and the cell-compatible nature of the device, it may be a useful platform for long-term stem cell culture and studies.

Cancer susceptibility and embryonic lethality in Mob1a/1b double-mutant mice

Mps one binder 1a (MOB1A) and MOB1B are key components of the Hippo signaling pathway and are mutated or inactivated in many human cancers. Here we show that intact Mob1a or Mob1b is essential for murine embryogenesis and that loss of the remaining WT Mob1 allele in Mob1a(Δ/Δ)1b(tr/+) or Mob1a(Δ/+)1b(tr/tr) mice results in tumor development. Because most of these cancers resembled trichilemmal carcinomas, we generated double-mutant mice bearing tamoxifen-inducible, keratinocyte-specific homozygous-null mutations of Mob1a and Mob1b (kDKO mice). kDKO mice showed hyperplastic keratinocyte progenitors and defective keratinocyte terminal differentiation and soon died of malnutrition. kDKO keratinocytes exhibited hyperproliferation, apoptotic resistance, impaired contact inhibition, enhanced progenitor self renewal, and increased centrosomes. Examination of Hippo pathway signaling in kDKO keratinocytes revealed that loss of Mob1a/b altered the activities of the downstream Hippo mediators LATS and YAP1. Similarly, YAP1 was activated in some human trichilemmal carcinomas, and some of these also exhibited MOB1A/1B inactivation. Our results clearly demonstrate that MOB1A and MOB1B have overlapping functions in skin homeostasis, and exert their roles as tumor suppressors by regulating downstream elements of the Hippo pathway.

Microfabricated polyester conical microwells for cell culture applications

Over the past few years there has been a great deal of interest in reducing experimental systems to a lab-on-a-chip scale. There has been particular interest in conducting high-throughput screening studies using microscale devices, for example in stem cell research. Microwells have emerged as the structure of choice for such tests. Most manufacturing approaches for microwell fabrication are based on photolithography, soft lithography, and etching. However, some of these approaches require extensive equipment, lengthy fabrication process, and modifications to the existing microwell patterns are costly. Here we show a convenient, fast, and low-cost method for fabricating microwells for cell culture applications by laser ablation of a polyester film coated with silicone glue. Microwell diameter was controlled by adjusting the laser power and speed, and the well depth by stacking several layers of film. By using this setup, a device containing hundreds of microwells can be fabricated in a few minutes to analyze cell behavior. Murine embryonic stem cells and human hepatoblastoma cells were seeded in polyester microwells of different sizes and showed that after 9 days in culture cell aggregates were formed without a noticeable deleterious effect of the polyester film and glue. These results show that the polyester microwell platform may be useful for cell culture applications. The ease of fabrication adds to the appeal of this device as minimal technological skill and equipment is required.