Endogenous suppression of WNT signalling in human embryonic stem cells leads to low differentiation propensity towards definitive endoderm

Low differentiation propensity towards a targeted lineage can significantly hamper the utility of individual human pluripotent stem cell (hPSC) lines in biomedical applications. Here, we use monolayer and micropatterned cell cultures, as well as transcriptomic profiling, to investigate how variability in signalling pathway activity between human embryonic stem cell lines affects their differentiation efficiency towards definitive endoderm (DE). We show that endogenous suppression of WNT signalling in hPSCs at the onset of differentiation prevents the switch from self-renewal to DE specification. Gene expression profiling reveals that this inefficient switch is reflected in NANOG expression dynamics. Importantly, we demonstrate that higher WNT stimulation or inhibition of the PI3K/AKT signalling can overcome the DE commitment blockage. Our findings highlight that redirection of the activity of Activin/NODAL pathway by WNT signalling towards mediating DE fate specification is a vulnerable spot, as disruption of this process can result in poor hPSC specification towards DE

Spectrum of gluten-related disorders: consensus on new nomenclature and classification

A decade ago celiac disease was considered extremely rare outside Europe and, therefore, was almost completely ignored by health care professionals. In only 10 years, key milestones have moved celiac disease from obscurity into the popular spotlight worldwide. Now we are observing another interesting phenomenon that is generating great confusion among health care professionals. The number of individuals embracing a gluten-free diet (GFD) appears much higher than the projected number of celiac disease patients, fueling a global market of gluten-free products approaching $2.5 billion (US) in global sales in 2010. This trend is supported by the notion that, along with celiac disease, other conditions related to the ingestion of gluten have emerged as health care concerns. This review will summarize our current knowledge about the three main forms of gluten reactions: allergic (wheat allergy), autoimmune (celiac disease, dermatitis herpetiformis and gluten ataxia) and possibly immune-mediated (gluten sensitivity), and also outline pathogenic, clinical and epidemiological differences and propose new nomenclature and classifications

Surface Science of DNA Adsorption onto Citrate-Capped Gold Nanoparticles

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Langmuir copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see Zhang, X., Servos, M. R., & Liu, J. (2012). Surface Science of DNA Adsorption onto Citrate-Capped Gold Nanoparticles. Langmuir, 28(8), 3896–3902. https://doi.org/10.1021/la205036pSingle-stranded DNA can be adsorbed by citrate capped gold nanoparticles (AuNPs), resulting in increased AuNP stability, which forms the basis of a number of biochemical and analytical applications, but the fundamental interaction of this adsorption reaction remains unclear. In this study, we measured DNA adsorption kinetics, capacity, and isotherms, demonstrating that the adsorption process is governed by electrostatic forces. The charge repulsion among DNA strands and between DNA and AuNPs can be reduced by adding salt, reducing pH or by using noncharged peptide nucleic acid (PNA). Langmuir adsorption isotherms are obtained, indicating the presence of both adsorption and desorption of DNA from AuNPs. While increasing salt concentration facilitates DNA adsorption, the desorption rate is also enhanced in higher salt due to DNA compaction. DNA adsorption capacity is determined by DNA oligomer length, DNA concentration, and salt. Previous studies indicated faster adsorption of short DNA oligomers by AuNPs, we find that once adsorbed, longer DNAs are much more effective in protecting AuNPs from aggregation. DNA adsorption is also facilitated by using low pH buffers and high alcohol concentrations. A model based on electrostatic repulsion on AuNPs is proposed to rationalize the DNA adsorption/desorption behavior.University of Waterloo || Canadian Foundation for Innovation || Ontario Ministry of Research & Innovation || Canadian Institutes of Health Research || Natural Sciences and Engineering Research Council |

Controlled Organization of Cell Fates in Spatially Confined Stem Cell Populations

During embryonic development, cells divide and differentiate over space and time as instructed by their environment to create complex, functionally diverse tissues. Our understanding of the underlying orchestrating rules is incomplete, but recent studies have started to reveal how to instruct cultured pluripotent cell populations to undergo similar developmental-like organizational events. Here, we induce spatially polarized cell fate organization in micropatterned colonies, previously only reported for non-adherent or locally induced cell populations. Underlying this discovery was the augmentation of our micropatterning high-throughput platform through the development of analytical frameworks to automate the quantification of heterogeneous cell responses. These developments enabled rapid hypotheses generation and testing, which enabled new insights into the underlying biology of how and when cell fate organization occurs. Specifically, we developed analytical frameworks to accurately identify colonies of cells within an image and localization of positively expressing regions within these, which enabled automatic quantification of spatial fate organization. We show that when mouse pluripotent stem cells are differentiated on micropatterns towards gastrulation-like fates, their normally symmetrical spatial organization of cell fates can be modified by changing the micropattern diameter and cell density. By differentiating cells at low to medium density on circular micropatterns of 200-300 um in diameter, we induce polarized organization of primitive streak-like and anterior epiblast-like cells, reminiscent of how these populations are localized during development. We study the emergence of this organization using live imaging and found that polarization occurs largely due to reorganization within the colony post-induction. Overall, our results show that system size, both in terms of colony geometry and cell number at the time of differentiation, is critical for polarized cell fate organization. We hypothesize that this could indicate a need for developmentally relevant system sizes in polarization of micropatterned colonies, and that it might be driven by initial heterogeneities in colony morphology or cell fate distribution, or minor fluctuation that are allowed to amplify and perturb a homogeneous state. These insights on how to control and quantify fate organization in cell populations can advance both our understanding of developmental processes and how to create complex tissues with regenerative engineering.Ph.D

The Environmental Outcome of Emissions-intensive Economic Growth: A Critical Look at Official Growth Projections for Sweden up to the Year 2000

Implications for carbon dioxide, sulphur dioxide and nitrogen oxides emissions from the Swedish government's medium-term economic projections are assessed, considering Sweden's environmental goals. Data from the first environmental accounting matrix of Sweden are exploited within the framework of the interindustry model to give emission multipliers for various components of aggregate demand. In view of these emission multipliers, it is evident that the outlined macro-economic development does not conform with Sweden's environmental goals. The oil price and the structural changes assumed in the economic projections stress still further the need for strong environmental policy measures to attain the emission goals. The allocation of total expenditure is shown here to be a critical factor for bringing down the emissions to accepted levels.Emission multipliers, macro-economic projections, emission/GDP ratio, environmental goals,