Hanging Drop Culture Research Articles

Ex vivo culture of human fetal gonads: manipulation of meiosis signalling by retinoic acid treatment disrupts testis development.

What are the effects of experimentally manipulating meiosis signalling by addition of retinoic acid (RA) in cultured human fetal gonads? RA-treatment accelerated meiotic entry in cultured fetal ovary samples, while addition of RA resulted in a dysgenetic gonadal phenotype in fetal testis cultures. One of the first manifestations of sex differentiation is the initiation of meiosis in fetal ovaries. In contrast, meiotic entry is actively prevented in the fetal testis at this developmental time-point. It has previously been shown that RA-treatment mediates initiation of meiosis in human fetal ovary ex vivo. This was a controlled ex vivo study of human fetal gonads treated with RA in 'hanging-drop' tissue cultures. The applied experimental set-up preserves germ cell-somatic niche interactions and the investigated outcomes included tissue integrity and morphology, cell proliferation and survival and the expression of markers of meiosis and sex differentiation. Tissue from 24 first trimester human fetuses was included in this study, all from elective terminations at gestational week (GW) 7-12. Gonads were cultured for 2 weeks with and without addition of 1 µM RA. Samples were subsequently formalin-fixed and investigated by immunohistochemistry and cell counting. Proteins investigated and quantified included; octamer-binding transcription factor 4 (OCT4), transcription factor AP-2 gamma (AP2γ) (embryonic germ cell markers), SRY (sex determining region Y)-box 9 (SOX9), anti-Müllerian hormone (AMH) (immature Sertoli cell markers), COUP transcription factor 2 (COUP-TFII) (marker of interstitial cells), forkhead box L2 (FOXL2) (granulosa cell marker), H2A histone family, member X (γH2AX) (meiosis marker), doublesex and mab-3 related transcription factor 1 (DMRT1) (meiosis regulator), cleaved poly ADP ribose polymerase (PARP), cleaved Caspase 3 (apoptosis markers) and Ki-67 antigen (Ki-67) (proliferation marker). Also, proliferation was determined using a 5'-bromo-2'-deoxyuridine (BrdU) incorporation assay. A novel ex vivo 'hanging-drop' culture model for human fetal gonads was successfully established. Continued proliferation of cells without signs of increased apoptosis was observed after 2 weeks of culture. In cultured fetal ovaries treated with RA, an increased number of meiotic germ cells (P < 0.05) and DMRT1-positive oogonia initiating meiosis (P < 0.05) was observed, which is in agreement with a previous study. In fetal testes, RA-treatment resulted in a decreased number of gonocytes (P < 0.05), a reduced percentage of proliferating gonocytes (P < 0.05), altered expression pattern of the somatic cell markers AMH and COUP-TFII, as well as disrupted seminiferous cord structure and testis morphology. The number of samples included in this study was relatively small due to the limited availability of human fetal tissue. The hanging-drop culture, similarly to other organ culture approaches, allows studies of germ cell-somatic niche interactions and determination of effects after manipulating specific signalling pathways. Our novel finding of disrupted fetal testis development after treatment with RA indicates that abnormal meiosis regulation can potentially cause gonadal dysgenesis. Further studies will elucidate the exact mechanisms and timing of observed effects. This work was supported in part by an ESPE Research Fellowship, sponsored by Novo Nordisk A/S to A.Jø. Additional funding for this project was obtained from The Research Council of the Capital Region of Denmark (E.R.-D.M.), The Research Fund at Rigshospitalet (A.Ju. and J.E.N.), Familien Erichssens Fund (A.Jø.), Dagmar Marshalls Fund (A.Jø.) and Aase & Ejnar Danielsens Fund (A.Jø.). The authors have no conflicts of interest.

Development and Characterization of a Scaffold-Free 3D Spheroid Model of Induced Pluripotent Stem Cell-Derived Human Cardiomyocytes.

Cardiomyocytes (CMs) are terminally differentiated cells in the adult heart, and ischemia and cardiotoxic compounds can lead to cell death and irreversible decline of cardiac function. As testing platforms, isolated organs and primary cells from rodents have been the standard in research and toxicology, but there is a need for better models that more faithfully recapitulate native human biology. Hence, a new in vitro model comprising the advantages of 3D cell culture and the availability of induced pluripotent stem cells (iPSCs) of human origin was developed and characterized. Human CMs derived from iPSCs were studied in standard 2D culture and as cardiac microtissues (MTs) formed in hanging drops. Two-dimensional cultures were examined using immunofluorescence microscopy and western blotting, while the cardiac MTs were subjected to immunofluorescence, contractility, and pharmacological investigations. iPSC-derived CMs in 2D culture showed well-formed myofibrils, cell-cell contacts positive for connexin-43, and other typical cardiac proteins. The cells reacted to prohypertrophic growth factors with a substantial increase in myofibrils and sarcomeric proteins. In hanging drop cultures, iPSC-derived CMs formed spheroidal MTs within 4 days, showing a homogeneous tissue structure with well-developed myofibrils extending throughout the whole spheroid without a necrotic core. MTs showed spontaneous contractions for more than 4 weeks that were recorded by optical motion tracking, sensitive to temperature and responsive to electrical pacing. Contractile pharmacology was tested with several agents known to modulate cardiac rate and viability. Calcium transients underlay the contractile activity and were also responsive to electrical stimulation, caffeine-induced Ca(2+) release, and extracellular calcium levels. A three-dimensional culture using iPSC-derived human CMs provides an organoid human-based cellular platform that is free of necrosis and recapitulates vital cardiac functionality, thereby providing a new and promising relevant model for the evaluation and development of new therapies and detection of cardiotoxicity.

Abstract 5446: Continuous real-time measurement of live and dead cells in culture over multiple days

Abstract Recently developed assay technologies have made it possible to use a multi-well plate reader to estimate the number of live or dead cells in culture in real time over a period of days to monitor the effects of long term exposure to test substances. An advantage of the real time assay chemistries is that the cells remain viable and available for other measurements. The purpose of this study was to determine if the real time assay methods could be multiplexed with other assay endpoints and applied to three dimensional (3D) culture models. The measurement of the number of live cells in real time is accomplished by providing a pro-substrate that viable cells (but not dead cells) can convert into a substrate for a luciferase derived from a marine shrimp. The pro-substrate and luciferase can be added with a single reagent addition step and because they are not toxic, they can be incubated with cells in culture for up to three days. Live cell conversion of the pro-substrate into a substrate for luciferase results in a luminescent signal that is proportional to the number of live cells. The signal diminishes immediately upon cell death. Detection of dead cells in real time is accomplished by using a fluorogenic DNA binding dye that is non-permeant and thus non-toxic to live cells. The dye enters dead cells that have a compromised membrane, binds to DNA, and becomes fluorescent. We have demonstrated that the real time assays can be multiplexed to measure both live and dead cells in the same sample. We further demonstrate the use of these assays to measure viability of cells in 3D spheroids formed using the hanging drop culture technique. We also demonstrate multiplexing of real time assays with subsequent measurement of apoptosis or extraction of RNA for expression studies. Utilization of real time assay chemistries that are non-toxic enabled repeated recording of data in a kinetic mode from the same sample of cells which eliminated the need for duplicate cultures and provided flexibility during assay protocol development. The ability to multiplex real time assays improved overall lab efficiency by eliminating the need for duplicate cultures for each experiment. Citation Format: Terry Riss, Jolanta Vidugiriene, Sarah Duellman, Wenhui Zhou, Gediminas Vidugiris, Mike Valley, Jean Osterman, Ruslan Arbit, Laurent Bernad, Poncho Meisenheimer, James J. Cali. Continuous real-time measurement of live and dead cells in culture over multiple days. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5446. doi:10.1158/1538-7445.AM2015-5446

Isolation and Investigation of Presumptive Murine Lacrimal Gland Stem Cells.

Aqueous tear deficiency due to lacrimal gland insufficiency is one of the major causes of dry eye disease. In severe cases, such as Sjogren's syndrome, Stevens-Johnson syndrome, or ocular cicatricial pemphigoid, therapy with artificial tears is often insufficient to relieve severe discomfort, prevent progressive ocular surface disease, or enable visual rehabilitation by corneal transplantation. Cell or organ generation from stem cells, resulting in tear-like secretion, presents an option as a suitable alternative treatment. To obtain deeper insights into lacrimal gland stem cells we analyzed murine lacrimal glands for markers of pluripotency, self-renewal, and differentiation. A special, patented technique with mechanical and enzymatic digestion was used to generate high numbers of cells in vitro from murine lacrimal glands. These presumptive "murine lacrimal gland stem cells" ("mLGSCs") can be propagated as monolayer cultures over multiple passages. By means of RT-PCR, Western blot, and immunohistochemistry, markers of pluripotency and differentiation were demonstrated. Hanging drop culture was used to build organoid bodies from mLGSCs to investigate their spontaneous differentiation in three-dimensional culture with histology, immunohistochemistry, and transmission electron microscopy methods. Isolated mLGSCs were cultured over more than 65 passages. Murine lacrimal gland stem cells expressed markers of pluripotency such as Nanog, Sox2, Kruppel-like factor 4 (Klf4), as well as early-lineage markers of all three germ layers. Three-dimensional culture of these cells revealed their ability to differentiate into various cell types. Our results suggest that mLGSCs were isolated and cultured successfully. These cells have the ability to differentiate into all three germ layers. The results provide further insights into lacrimal gland stem cell physiology for engineering of a lacrimal gland construct to treat severe cases of tear deficiency in the future.

Formation of stable small cell number three-dimensional ovarian cancer spheroids using hanging drop arrays for preclinical drug sensitivity assays

BackgroundOvarian cancer grows and metastasizes from multicellular spheroidal aggregates within the ascites fluid. Multicellular tumor spheroids are therefore physiologically significant 3D in vitro models for ovarian cancer research. Conventional hanging drop cultures require high starting cell numbers, and are tedious for long-term maintenance. In this study, we generate stable, uniform multicellular spheroids using very small number of ovarian cancer cells in a novel 384 well hanging drop array platform. MethodsWe used novel tumor spheroid platform and two ovarian cancer cell lines (A2780 and OVCAR3) to demonstrate the stable incorporation of as few as 10 cells into a single spheroid. ResultsSpheroids had uniform geometry, with projected areas (42.60×103μm–475.22×103μm2 for A2780 spheroids and 37.24×103μm2–281.01×103μm2 for OVCAR3 spheroids) that varied as a function of the initial cell seeding density. Phalloidin and nuclear stains indicated cells formed tightly packed spheroids with demarcated boundaries and cell–cell interaction within spheroids. Cells within spheroids demonstrated over 85% viability. 3D tumor spheroids demonstrated greater resistance (70–80% viability) to cisplatin chemotherapy compared to 2D cultures (30–50% viability). ConclusionsOvarian cancer spheroids can be generated from limited cell numbers in high throughput 384 well plates with high viability. Spheroids demonstrate therapeutic resistance relative to cells in traditional 2D culture. Stable incorporation of low cell numbers is advantageous when translating this research to rare patient-derived cells. This system can be used to understand ovarian cancer spheroid biology, as well as carry out preclinical drug sensitivity assays.

Digital microfluidics for automated hanging drop cell spheroid culture.

Cell spheroids are multicellular aggregates, grown in vitro, that mimic the three-dimensional morphology of physiological tissues. Although there are numerous benefits to using spheroids in cell-based assays, the adoption of spheroids in routine biomedical research has been limited, in part, by the tedious workflow associated with spheroid formation and analysis. Here we describe a digital microfluidic platform that has been developed to automate liquid-handling protocols for the formation, maintenance, and analysis of multicellular spheroids in hanging drop culture. We show that droplets of liquid can be added to and extracted from through-holes, or "wells," and fabricated in the bottom plate of a digital microfluidic device, enabling the formation and assaying of hanging drops. Using this digital microfluidic platform, spheroids of mouse mesenchymal stem cells were formed and maintained in situ for 72 h, exhibiting good viability (>90%) and size uniformity (% coefficient of variation <10% intraexperiment, <20% interexperiment). A proof-of-principle drug screen was performed on human colorectal adenocarcinoma spheroids to demonstrate the ability to recapitulate physiologically relevant phenomena such as insulin-induced drug resistance. With automatable and flexible liquid handling, and a wide range of in situ sample preparation and analysis capabilities, the digital microfluidic platform provides a viable tool for automating cell spheroid culture and analysis.

Abstract 5272: The tumor suppressor, calcium sensing receptor, regulates proliferation and promotes differentiation in colon cancer

Abstract There is increasing evidence highlighting an inverse correlation between high dietary calcium intake and reduced risk of colorectal cancer. The classical role of the calcium sensing receptor (CaSR), a G protein coupled receptor, is regulation of calcium homeostasis in the parathyroid and kidney. In other tissue types, CaSR regulates different cellular processes like proliferation, differentiation, and apoptosis. We have demonstrated that CaSR expression is downregulated in colorectal cancer (CRC) leading us to hypothesize that loss of CaSR might provide a growth advantage to transformed cells, conferring them resistance to calcium-mediated growth inhibition. Therefore the aim of this study was to understand the role of CaSR in CRC. In vitro, HT29 (moderately differentiated) and Caco-2/15 (well differentiated) colon cancer cells were stably transfected with constructs to overexpress either the wild type CaSR (CaSRWT) or a dominant negative CaSR mutant (CaSRDN). The cells transfected with the CaSRWT construct grew significantly slower than the cells overexpressing the CaSRDN (Caco2-15: 40% slower; HT29: 50% slower; p&amp;lt;0.001) as assessed by cell counting. This effect was much more pronounced when cells were treated with the calcimimetic NPS R568, an allosteric modulator of the CaSR. Treating the cells with the calcilytic NPS 2143, a negative allosteric modulator of the receptor, we could reverse the antiproliferative effect. Furthermore, CaSRWT cells were more differentiated than CaSRDN cells as shown by the high Alkaline Phosphatase activity in culture (3-fold higher in Caco2-15; p&amp;lt;0.001). We also evaluated the tumor formation ability of these cells in hanging drop cultures. Indeed, CaSRDN formed large spheroids, whereas CaSRWT cells formed irregular shaped aggregates demonstrating a possible role of the CaSR in inhibiting tumor formation (in HT29 cells, CaSRDN spheroids had 10-fold increased volume compared with control cells; p&amp;lt;0.001). To translate these findings in vivo, we investigated the effects of global knock down of CaSR. Global ablation of CaSR in mice led to lethality within 1-2 weeks; therefore we analyzed the colon of ‘rescued’ CaSR-/PTH- double knockout mice, and compared them to colons of CaSR+/PTH- mice. CaSR-/PTH- mice had increased expression of proliferation related markers (for instance, 1.5-fold cell cycle division 6 (Cdc6) expression, p&amp;lt;0.01). Histological examination has revealed the presence of aberrant crypt foci in the colon of the double knockout mice. This suggests that loss of CaSR expression gives colon cancer cells a growth advantage during tumorigenesis. These data further our understanding of the molecular mechanism by which the CaSR protects colon epithelial cells from malignant transformation. These mechanisms, in part, account for the anti-neoplastic effects of calcium in the colon. Citation Format: Abhishek Aggarwal, Samawansha Tennakoon, Maximilian Wohlgenannt, Cedric Boudot, Romuald Mentaverri, Sabina Baumgartner-Parzer, Enikö Kállay. The tumor suppressor, calcium sensing receptor, regulates proliferation and promotes differentiation in colon cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5272. doi:10.1158/1538-7445.AM2014-5272

Unique characteristics of human mesenchymal stromal/progenitor cells pre-activated in 3-dimensional cultures under different conditions

Background aimsHuman mesenchymal stromal cells (MSCs) are being used in clinical trials, but the best protocol to prepare the cells for administration to patients remains unclear. We previously demonstrated that MSCs could be pre-activated to express therapeutic factors by culturing the cells in 3 dimensions (3D). We compared the activation of MSCs in 3D in fetal bovine serum containing medium and in multiple xeno-free media formulations. MethodsMSC aggregation and sphere formation was studied with the use of hanging drop cultures with medium containing fetal bovine serum or with various commercially available stem cell media with or without human serum albumin (HSA). Activation of MSCs was studied with the use of gene expression and protein secretion measurements and with functional studies with the use of macrophages and cancer cells. ResultsMSCs did not condense into tight spheroids and express a full complement of therapeutic genes in α-minimum essential medium or several commercial stem-cell media. However, we identified a chemically defined xeno-free media, which, when supplemented with HSA from blood or recombinant HSA, resulted in compact spheres with high cell viability, together with high expression of anti-inflammatory (prostaglandin E2, TSG-6 TNF-alpha induced gene/protein 6) and anti-cancer molecules (TRAIL TNF-related apoptosis-inducing ligand, interleukin-24). Furthermore, spheres cultured in this medium showed potent anti-inflammatory effects in a lipopolysaccharide-stimulated macrophage system and suppressed the growth of prostate cancer cells by promoting cell-cycle arrest and cell death. ConclusionsWe demonstrated that cell activation in 3D depends critically on the culture medium. The conditions developed in the present study for 3D culture of MSCs should be useful in further research on MSCs and their potential therapeutic applications.

Hanging drop cultures of human testis and testis cancer samples: a model used to investigate activin treatment effects in a preserved niche.

Background:Testicular germ cell tumours of young adults, seminoma or non-seminomas, are preceded by a pre-invasive precursor, carcinoma in situ (CIS), understood to arise through differentiation arrest of embryonic germ cells. Knowledge about the malignant transformation of germ cells is currently limited by the lack of experimental models. The aim of this study was to establish an experimental tissue culture model to maintain normal and malignant germ cells within their niche and allow investigation of treatment effects.Methods:Human testis and testis cancer specimens from orchidectomies were cultured in ‘hanging drops' and effects of activin A and follistatin treatment were investigated in seminoma cultures.Results:Testis fragments with normal spermatogenesis or CIS cells were cultured for 14 days with sustained proliferation of germ cells and CIS cells and without increased apoptosis. Seminoma cultures survived 7 days, with proliferating cells detectable during the first 5 days. Activin A treatment significantly reduced KIT transcript and protein levels in seminoma cultures, thereby demonstrating a specific treatment response.Conclusions:Hanging drop cultures of human testis and testis cancer samples can be employed to delineate mechanisms governing growth of normal, CIS and tumorigenic germ cells retained within their niche.

Improved physiological properties of gravity-enforced reassembled rat and human pancreatic pseudo-islets.

Previously we demonstrated the superiority of small islets vs large islets in terms of function and survival after transplantation, and we generated reaggregated rat islets (pseudo-islets) of standardized small dimensions by the hanging-drop culture method (HDCM). The aim of this study was to generate human pseudo-islets by HDCM and to evaluate and compare the physiological properties of rat and human pseudo-islets. Isolated rat and human islets were dissociated into single cells and incubated for 6-14 days by HDCM. Newly formed pseudo-islets were analysed for dimensions, morphology, glucose-stimulated insulin secretion (GSIS) and total insulin content. The morphology of reaggregated human islets was similar to that of native islets, while rat pseudo-islets had a reduced content of α and δ cells. GSIS of small rat and human pseudo-islets (250 cells) was increased up to 4.0-fold (p < 0.01) and 2.5-fold (p < 0.001), respectively, when compared to their native counterparts. Human pseudo-islets showed a more pronounced first-phase insulin secretion as compared to intact islets. GSIS was inversely correlated to islet size, and small islets (250 cells) contained up to six-fold more insulin/cell than large islets (1500 cells). Tissue loss with this new technology could be reduced to 49.2 ± 1.5% in rat islets, as compared to the starting amount. With HDCM, pseudo-islets of standardized size with similar cellular composition and improved biological function can be generated, which compensates for tissue loss during production. Transplantation of small pseudo-islets may represent an attractive strategy to improve graft survival and function, due to better oxygen and nutrient supply during the phase of revascularization. Copyright © 2014 John Wiley & Sons, Ltd.

Mouse embryonic stem cell differentiation into cardiomyocytes is inhibited by ethanol but only after the embryoid body stage (844.3)

Ethanol up to 0.5% is recommended for use as a solvent in mouse embryonic stem cell (mESC) differentiation assays such as the Embryonic Stem Cell Test. However, lower concentrations have been shown by some to alter mESC differentiation. In this study, we further explored the dose‐ and time‐dependent affects of ethanol on mESC differentiation into cardiomyocytes using the hanging drop culture method and J1 mESC. Among control cultures (no ethanol), rhythmically contracting cells were observed in cultures after 11 days at a frequency of 蠅64%. With continuous ethanol exposure, a significant (p 蠄 0.05) decrease in the fraction of cultures containing contracting cells was observed by 蠅68% at ethanol concentrations of 0.3% and higher and was accompanied by a 蠅30% loss of cells. With ethanol exposure during the first two days of culture only (the embryoid body stage), no significant change in the frequency of contracting cells per culture, or number of cells, was observed after 11 days at ethanol concentrations up to 0.5%. These results suggest that ethanol concentrations below 0.5% can reduce the frequency of contracting cells, at least in part, by reducing the number of cells during differentiation, and that the most sensitive time‐frame for ethanol toxicity is after the embryoid body stage.Grant Funding Source: Supported by NSF DUE‐0622421

Morphogenesis and alpha-tubulin gene of plasmodium in Didymium megalosporum

The morphogenesis of plasmodium in Didymium megalosporum was observed for the first time by hanging drop culture and 3% oat-agar culture under controlled conditions. The development of plasmodium was characteristic formation process of phaneroplasmodium. The mature plasmodium was white yellow or yellow green in color, and had an extending fan-like sheet at the front, followed by a network of veins. It could be easy to fuse into a bigger plasmodium during the formation and die at high temperature or starvation. In view of the important role of alpha-tubulin during the morphogenesis of plasmodium, we sequenced partial sequence of alpha-tubulin gene, a total length of 1,159bp, in this plasmodium. It had an intron area from 177 to 235bp, and the exon area had a similarity of 91% relative to altA locus of alpha-tubulin gene in Physarum polycephalum, the translated amino acid sequence was identical (100% match) between the two.

Preparation of anti-inflammatory mesenchymal stem/precursor cells (MSCs) through sphere formation using hanging-drop culture technique.

Herein, we describe a protocol for preparation of pre-activated anti-inflammatory human mesenchymal stem/precursor cells (MSCs) in 3-D culture without addition of exogenous chemicals or gene-transfer approaches. MSCs are an easily procurable source of multipotent adult stem cells with therapeutic potential largely attributed to their paracrine regulation of inflammation and immunity. However, the culture conditions to prepare the ideal MSCs for cell therapy remain elusive. Furthermore, the reported lag time for activation in experimental models has prompted investigations on pre-activating the cells prior to their administration. In this protocol, standard 2-D culture-expanded MSCs are activated by aggregation into 3-D spheres using hanging-drop cultures. MSC activation is evaluated by real-time PCR and/or ELISA for anti-inflammatory factors (TSG-6, STC-1, PGE2), and by a functional assay using lipopolysaccharide-stimulated macrophage cultures. Further, we elucidate methods to prepare MSC-sphere conditioned medium, intact spheres, and suspension of single cells from spheres for experimental and clinical applications.

Mouse-Induced Pluripotent Stem Cells Differentiate into Odontoblast-Like Cells with Induction of Altered Adhesive and Migratory Phenotype of Integrin

Methods for differentiating induced pluripotent stem (iPS) cells into odontoblasts generally require epithelial–mesenchymal interactions. Here, we sought to characterize the cells produced by a ‘hanging drop’ technique for differentiating mouse iPS cells into odontoblast-like cells that requires no such interaction. Cells were cultured by the hanging drop method on a collagen type-I (Col-I) scaffold (CS) combined with bone morphogenetic protein (BMP)-4 (CS/BMP-4) without an epithelial–mesenchymal interaction. We evaluated the expression of odontoblast-related mRNA and protein, and the proliferation rate of these cells using reverse-transcription polymerase chain reaction, immunofluorescence staining, and BrdU cell proliferation enzyme-linked immunosorbent assay, respectively. The differentiated cells strongly expressed the mRNA for dentin sialophosphoprotein (DSPP) and dentin matrix protein-1 (Dmp-1), which are markers of mature odontoblasts. Osteopontin and osteocalcin were not expressed in the differentiated cells, demonstrating that the differentiated iPS cells bore little resemblance to osteoblasts. Instead, they acquired odontoblast-specific properties, including the adoption of an odontoblastic phenotype, typified by high alkaline phosphatase (ALP) activity and calcification capacity. The cell-surface expression of proteins such as integrins α2, α6, αV and αVβ3 was rapidly up-regulated. Interestingly, antibodies and siRNAs against integrin α2 suppressed the expression of DSPP and Dmp-1, reduced the activity of ALP and blocked calcification, suggesting that integrin α2 in iPS cells mediates their differentiation into odontoblast-like cells. The adhesion of these cells to fibronectin and Col-I, and their migration on these substrata, was significantly increased following differentiation into odontoblast-like cells. Thus, we have demonstrated that integrin α2 is involved in the differentiation of mouse iPS cells into odontoblast-like cells using the hanging drop culture method, and that these cells have the appropriate physiological and functional characteristics to act as odontoblasts in tissue engineering and regenerative therapies for the treatment of dentin and/or dental pulp damage.

Dynamic compaction of human mesenchymal stem/precursor cells into spheres self-activates caspase-dependent IL1 signaling to enhance secretion of modulators of inflammation and immunity (PGE2, TSG6, and STC1).

Human mesenchymal stem/precursor cells (MSC) are similar to some other stem/progenitor cells in that they compact into spheres when cultured in hanging drops or on nonadherent surfaces. Assembly of MSC into spheres alters many of their properties, including enhanced secretion of factors that mediate inflammatory and immune responses. Here we demonstrated that MSC spontaneously aggregated into sphere-like structures after injection into a subcutaneous air pouch or the peritoneum of mice. The structures were similar to MSC spheres formed in cultures demonstrated by the increased expression of genes for inflammation-modulating factors TSG6, STC1, and COX2, a key enzyme in production of PGE2. To identify the signaling pathways involved, hanging drop cultures were used to follow the time-dependent changes in the cells as they compacted into spheres. Among the genes upregulated were genes for the stress-activated signaling pathway for IL1α/β, and the contact-dependent signaling pathway for Notch. An inhibitor of caspases reduced the upregulation of IL1A/B expression, and inhibitors of IL1 signaling decreased production of PGE2, TSG6, and STC1. Also, inhibition of IL1A/B expression and secretion of PGE2 negated the anti-inflammatory effects of MSC spheres on stimulated macrophages. Experiments with γ-secretase inhibitors suggested that Notch signaling was also required for production of PGE2 but not TSG6 or STC1. The results indicated that assembly of MSC into spheres triggers caspase-dependent IL1 signaling and the secretion of modulators of inflammation and immunity. Similar aggregation in vivo may account for some of the effects observed with administration of the cells in animal models.

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 1000μm. 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 1000μm 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.

Human stem cell-based three-dimensional microtissues for advanced cardiac cell therapies

Cardiac stem cell therapy has been proposed as a therapy option to treat the diseased myocardium. However, the low retention rate of transplanted single-cell suspensions remains a major issue of current therapy strategies. Therefore, the concept of scaffold-free cellular self-assembly into three-dimensional microtissues (3D-MTs) prior to transplantation may be beneficial to enhance retention and survival. We compared clinically relevant, human stem cell sources for their ability to generate 3D-MTs with particular regards to formation characteristics, proliferation-activity, viability and extracellular-matrix production. Single-cell suspensions of human bone marrow- and adipose tissue-derived mesenchymal stem cells (hBMMSCs and hATMSCs), Isl1+ cardiac progenitors derived from human embryonic stem cells (hESC-Isl1+ cells), and undifferentiated human induced pluripotent cells (hiPSCs) were characterized before to generate 3D-MTs using a hanging-drop culture. Besides the principal feasibility of cell-specific 3D-MT formation, a detailed head-to-head comparison between cell sources was performed using histology, immunocyto- and histo-chemistry as well as flow cytometry. Round-oval shaped and uniform 3D-MTs could be successfully generated from all cell types starting with a loose formation within the first 24 h that fully stabilized after 3 days and resulting in a mean 3D-MT diameter of 194.56 ± 18.01 μm (hBMMSCs), 194.56 ± 16.30 μm (hATMSCs), 159.73 ± 19.20 μm (hESC-Isl1+ cells) and 120.95 ± 7.97 μm (hiPSCs). While all 3D-MTs showed a homogenous cell distribution, hiPSC-derived 3D-MTs displayed a compact cell formation primarily located at the outer margin. hESC-Isl1+ and hiPSC-derived 3D-MTs maintained their proliferation-activity which was rather limited in the MSC-based 3D-MTs. All four 3D-MT types revealed a comparable viability in excess of 70% and showed a cell-specific expression profile being comparable to their single-cell counterparts. Extracellular matrix (ECM) production during 3D-MT formation was observed for all cell-specific 3D-MTs, with hiPSC-derived 3D-MTs being the fastest one. Interestingly, ECM distribution was homogenous for hATMSC- and hiPSC-based 3D-MTs, while it appeared to be primarily concentrated within in the center of hESC-Isl1+ and hBMMSC-based 3D-MTs. The results of this head-to-head comparative study indicated that 3D-MTs can be successfully generated from hESC-derived Isl1+ cells, hiPSCs and MSC lines upon hanging drop culture. Cell-specific 3D-MTs displayed sufficient viability and instant ECM formation. The concept of 3D-MT in vitro generation prior to cell transplantation may represent a promising delivery format for future strategies to enhance cellular engraftment and survival.

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.

LSI-based amperometric sensor for real-time monitoring of embryoid bodies

A large scale integration (LSI)-based amperometric sensor is used for electrochemical evaluation and real-time monitoring of the alkaline phosphatase (ALP) activity of mouse embryoid bodies (EBs). EBs were prepared by the hanging drop culture of embryonic stem (ES) cells. The ALP activity of EBs with various sizes was electrochemically detected at 400 measurement points on a Bio-LSI chip. The electrochemical measurements revealed that the relative ALP activity was low for large EBs and decreased with progress of the differentiation level of the ES cells. The ALP activity of the EBs was successfully monitored in real time for 3.5h, and their ALP activity in a glucose-free buffer decreased after 2h. To the best of our knowledge, this is the first report on the application of an LSI-based amperometric sensor for real-time cell monitoring over 3h. The chip is expected to be useful for the evaluation of cell activities.

Small cell ovarian carcinoma: genomic stability and responsiveness to therapeutics

BackgroundThe biology of small cell ovarian carcinoma of the hypercalcemic type (SCCOHT), which is a rare and aggressive form of ovarian cancer, is poorly understood. Tumourigenicity, in vitro growth characteristics, genetic and genomic anomalies, and sensitivity to standard and novel chemotherapeutic treatments were investigated in the unique SCCOHT cell line, BIN-67, to provide further insight in the biology of this rare type of ovarian cancer.MethodThe tumourigenic potential of BIN-67 cells was determined and the tumours formed in a xenograft model was compared to human SCCOHT. DNA sequencing, spectral karyotyping and high density SNP array analysis was performed. The sensitivity of the BIN-67 cells to standard chemotherapeutic agents and to vesicular stomatitis virus (VSV) and the JX-594 vaccinia virus was tested.ResultsBIN-67 cells were capable of forming spheroids in hanging drop cultures. When xenografted into immunodeficient mice, BIN-67 cells developed into tumours that reflected the hypercalcemia and histology of human SCCOHT, notably intense expression of WT-1 and vimentin, and lack of expression of inhibin. Somatic mutations in TP53 and the most common activating mutations in KRAS and BRAF were not found in BIN-67 cells by DNA sequencing. Spectral karyotyping revealed a largely normal diploid karyotype (in greater than 95% of cells) with a visibly shorter chromosome 20 contig. High density SNP array analysis also revealed few genomic anomalies in BIN-67 cells, which included loss of heterozygosity of an estimated 16.7 Mb interval on chromosome 20. SNP array analyses of four SCCOHT samples also indicated a low frequency of genomic anomalies in the majority of cases. Although resistant to platinum chemotherapeutic drugs, BIN-67 cell viability in vitro was reduced by >75% after infection with oncolytic viruses.ConclusionsThese results show that SCCOHT differs from high-grade serous carcinomas by exhibiting few chromosomal anomalies and lacking TP53 mutations. Although BIN-67 cells are resistant to standard chemotherapeutic agents, their sensitivity to oncolytic viruses suggests that their therapeutic use in SCCOHT should be considered.