88 research outputs found
Matrix Revolutions: A Trinity of Defined Substrates for Long-Term Expansion of Human ESCs
No full textRecently in Nature Biotechnology, Rodin et al. (2010), Melkoumian et al. (2010), and Villa-Diaz et al. (2010) described defined, nonxenogenic substrates that support long-term self-renewal of human embryonic stem cells (hESCs). Used in conjunction with defined media, these substrates will facilitate expansion of hESCs for therapeutic applications
Electron–hole superfluidity in strained Si/Ge type II heterojunctions
No full textExcitons are promising candidates for generating superfluidity and Bose–Einstein condensation (BEC) in solid-state devices, but an enabling material platform with in-built band structure advantages and scaling compatibility with industrial semiconductor technology is lacking. Here we predict that spatially indirect excitons in a lattice-matched strained Si/Ge bilayer embedded into a germanium-rich SiGe crystal would lead to observable mass-imbalanced electron–hole superfluidity and BEC. Holes would be confined in a compressively strained Ge quantum well and electrons in a lattice-matched tensile strained Si quantum well. We envision a device architecture that does not require an insulating barrier at the Si/Ge interface, since this interface offers a type II band alignment. Thus the electrons and holes can be kept very close but strictly separate, strengthening the electron–hole pairing attraction while preventing fast electron–hole recombination. The band alignment also allows a one-step procedure for making independent contacts to the electron and hole layers, overcoming a significant obstacle to device fabrication. We predict superfluidity at experimentally accessible temperatures of a few Kelvin and carrier densities up to ~6 × 1010 cm−2, while the large imbalance of the electron and hole effective masses can lead to exotic superfluid phases.QCD/Scappucci La
A facile in vitro platform to study cancer cell dormancy under hypoxic microenvironments using CoCl2
No full textAbstract Background While hypoxia has been well-studied in various tumor microenvironments, its role in cancer cell dormancy is poorly understood, in part due to a lack of well-established in vitro and in vivo models. Hypoxic conditions under conventional hypoxia chambers are relatively unstable and cannot be maintained during characterization outside the chamber since normoxic response is quickly established. To address this challenge, we report a robust in vitro cancer dormancy model under a hypoxia-mimicking microenvironment using cobalt chloride (CoCl2), a hypoxia-mimetic agent, which stabilizes hypoxia inducible factor 1-alpha (HIF1α), a major regulator of hypoxia signaling. Methods We compared cellular responses to CoCl2 and true hypoxia (0.1% O2) in different breast cancer cell lines (MCF-7 and MDA-MB-231) to investigate whether hypoxic regulation of breast cancer dormancy could be mimicked by CoCl2. To this end, expression levels of hypoxia markers HIF1α and GLUT1 and proliferation marker Ki67, cell growth, cell cycle distribution, and protein and gene expression were evaluated under both CoCl2 and true hypoxia. To further validate our platform, the ovarian cancer cell line OVCAR-3 was also tested. Results Our results demonstrate that CoCl2 can mimic hypoxic regulation of cancer dormancy in MCF-7 and MDA-MB-231 breast cancer cell lines, recapitulating the differential responses of these cell lines to true hypoxia in 2D and 3D. Moreover, distinct gene expression profiles in MCF-7 and MDA-MB-231 cells under CoCl2 treatment suggest that key cell cycle components are differentially regulated by the same hypoxic stress. In addition, the induction of dormancy in MCF-7 cells under CoCl2 treatment is HIF1α-dependent, as evidenced by the inability of HIF1α-suppressed MCF-7 cells to exhibit dormant behavior upon CoCl2 treatment. Furthermore, CoCl2 also induces and stably maintains dormancy in OVCAR-3 ovarian cancer cells. Conclusions These results demonstrate that this CoCl2-based model could provide a widely applicable in vitro platform for understanding induction of cancer cell dormancy under hypoxic stress
Model-guided engineering of DNA sequences with predictable site-specific recombination rates
No full textSite-specific recombination (SSR) is an important tool in synthetic biology, but its applications are limited by the inability to predictably tune SSR reaction rates. Here, using quantitative high-throughput experiments and machine learning, the authors achieve rational control of a DNA attachment site sequence to predictably modulate site-specific recombination rates both in vitro and in cells
Freezing Responses in DMSO-Based Cryopreservation of Human iPS Cells: Aggregates Versus Single Cells
No full textRapid retinoic acid-induced trophoblast cell model from human induced pluripotent stem cells
No full textAbstract A limited number of accessible and representative models of human trophoblast cells currently exist for the study of placentation. Current stem cell models involve either a transition through a naïve stem cell state or precise dynamic control of multiple growth factors and small-molecule cues. Here, we demonstrated that a simple five-day treatment of human induced pluripotent stem cells with two small molecules, retinoic acid (RA) and Wnt agonist CHIR 99021 (CHIR), resulted in rapid, synergistic upregulation of CDX2. Transcriptomic analysis of RA + CHIR-treated cells showed high similarity to primary trophectoderm cells. Multipotency was verified via further differentiation towards cells with syncytiotrophoblast or extravillous trophoblast features. RA + CHIR-treated cells were also assessed for the established criteria defining a trophoblast cell model, and they possess all the features necessary to be considered valid. Collectively, our data demonstrate a facile, scalable method for generating functional trophoblast-like cells in vitro to better understand the placenta
Abstract B52: Inhibition of ovarian cancer spheroid adhesion using graphene oxide nanomaterials
No full textHuman embryonic stem cell-derived keratinocytes exhibit an epidermal transcription program and undergo epithelial morphogenesis in engineered tissue constructs
No full textHuman embryonic stem (hES) cells are an attractive source of cellular material for scientific, diagnostic, and
potential therapeutic applications. Protocols are now available to direct hES cell differentiation to specific lineages
at high purity under relatively defined conditions; however, researchers must establish the functional
similarity of hES cell derivatives and associated primary cell types to validate their utility. Using retinoic acid to
initiate differentiation, we generated high-purity populations of keratin 14þ (K14) hES cell-derived keratinocyte
(hEK) progenitors and performed microarray analysis to compare the global transcriptional program of hEKs
and primary foreskin keratinocytes. Transcriptional patterns were largely similar, though gene ontology analysis
identified that genes associated with signal transduction and extracellular matrix were upregulated in hEKs. In
addition, we evaluated the ability of hEKs to detect and respond to environmental stimuli such as Ca2þ, serum,
and culture at the air–liquid interface. When cultivated on dermal constructs formed with collagen gels and
human dermal fibroblasts, hEKs survived and proliferated for 3 weeks in engineered tissue constructs. Maintenance
at the air–liquid interface induced stratification of surface epithelium, and immunohistochemistry results
indicated that markers of differentiation (e.g., keratin 10, involucrin, and filaggrin) were localized to
suprabasal layers. Although the overall tissue morphology was significantly different compared with human
skin samples, organotypic cultures generated with hEKs and primary foreskin keratinocytes were quite similar,
suggesting these cell types respond to this microenvironment in a similar manner. These results represent an
important step in characterizing the functional similarity of hEKs to primary epithelia.National Institute of Biomedical Imaging and Bioengineering (U.S.) (Grant 1R01EB007534)National Science Foundation (U.S.) (Grant EFRI-0735903)National Institutes of Health (U.S.). Biotechnology Training Fellowshi
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