大学紹介

Allogeneic hematopoietic stem cell (HSC) transplantations from umbilical cord blood or autologous HSCs for gene therapy purposes are hampered by limited number of stem cells. To test the ability to expand HSCs in vitro prior to transplantation, two growth factor cocktails containing stem cell factor, thrombopoietin, fms-related tyrosine kinase-3 ligand (STF) or stem cell factor, thrombopoietin, insulin-like growth factor-2, fibroblast growth factor-1 (STIF) either with or without the addition of angiopoietin-like protein-3 (Angptl3) were used. Culturing HSCs in STF and STIF media for 7 days expanded long-term repopulating stem cells content in vivo by ∼6-fold and ∼10-fold compared to freshly isolated stem cells. Addition of Angptl3 resulted in increased expansion of these populations by ∼17-fold and ∼32-fold, respectively, and was further supported by enforced expression of Angptl3 in HSCs through lentiviral transduction that also promoted HSC expansion. As expansion of highly purified lineage-negative, Sca-1+, c-Kit+ HSCs was less efficient than less pure lineage-negative HSCs, Angptl3 may have a direct effect on HCS but also an indirect effect on accessory cells that support HSC expansion. No evidence for leukemia or toxicity was found during long-term follow up of mice transplanted with ex vivo expanded HSCs or manipulated HSC populations that expressed Angptl3. We conclude that the cytokine combinations used in this study to expand HSCs ex vivo enhances the engraftment in vivo. This has important implications for allogeneic umbilical cord-blood derived HSC transplantations and autologous HSC applications including gene therapy

Differences in farmers’ perception of opportunities for farm development

This paper empirically identifies differences between dairy farmers in their perception of opportunities for farm development. The construct ‘perceived Room for Manoeuvre’ (pRfM) is used which is defined as: ‘the opportunities perceived as viable in order to obtain a (substantial part of) business income’. A unique case study of 79 dairy farmers operating in a highly comparable socio-material context at the level of the case study allows for an empirical analysis of differences in the pRfM using a mix of quantitative and qualitative methods exploratory research, a questionnaire and in-depth interviews with stakeholders in farm development. Differences in the pRfM will likely affect the early phase of strategic decision making and consequently explain heterogeneity in farm development. Data analysis revealed the following three dimensions of pRfM: perception of the opportunity (1) to diversify; (2) to end production; and (3) to maximise production. These dimensions proved useful to explain heterogeneity in farm development and thus showed the importance of a subjective approach towards opportunity identification in farm development. This paper shows the need to view the farmer as entrepreneurial actor in the process of strategic decision making who interacts with the socio-material context of the farm

Three-fold embedding : Farm development in relation to its socio-material context

Abstract: Understanding heterogeneity in farm development strategies is important in order to design effective policies and support programs to increase the sustainability of agriculture in relation to its socio-material context. Using a unique case study of 102 dairy farmers in The Netherlands, all operating in a highly similar socio-material context, this paper studies the differences in the relation of farms with the socio-material context. To this end, the concept of three-fold embedding is developed and tested using the ideal-typical characteristics of three patterns of farm development that were identified in the case study: (1) maximising total milk production; (2) optimising milk production using mainly on-farm resources; and (3) diversified on-farm production. Three-fold embedding was conceptualised in relation to the following dimensions: (1) value chain relations; (2) socio-cultural relations; and (3) natural resource relations, while using a scale ranging from a Close to a Stretched set of relations. The concept of three-fold embedding proves to be useful to identify in a non-normative and non-binary manner meaningful differences between patterns of farm development. These differences relate to differences in opportunity identification and strategic decision-making. The concept supports a relational perspective in studying farm strategy development using a sociology of entrepreneurship approach.</p

Lentiviral gene therapy of murine hematopoietic stem cells ameliorates the Pompe disease phenotype

Pompe disease (acid alpha-glucosidase deficiency) is a lysosomal glycogen storage disorder characterized in its most severe early-onset form by rapidly progressive muscle weakness and mortality within the first year of life due to cardiac and respiratory failure. Enzyme replacement therapy prolongs the life of affected infants and supports the condition of older children and adults but entails lifelong treatment and can be counteracted by immune responses to the recombinant enzyme. We have explored the potential of lentiviral vector-mediated expression of human acid alpha-glucosidase in hematopoietic stem cells (HSCs) in a Pompe mouse model. After mild conditioning, transplantation of genetically engineered HSCs resulted in stable chimerism of approximately 35% hematopoietic cells that overexpress acid alpha-glucosidase and in major clearance of glycogen in heart, diaphragm, spleen, and liver. Cardiac remodeling was reversed, and respiratory function, skeletal muscle strength, and motor performance improved. Overexpression of acid alpha-glucosidase did not affect overall hematopoietic cell function and led to immune tolerance as shown by challenge with the human recombinant protein. On the basis of the prominent and sustained therapeutic efficacy without adverse events in mice we conclude that ex vivo HSC gene therapy is a treatment option worthwhile to pursue. (Blood. 2010; 115(26):5329-5337

Angptl3 overexpression promotes expansion of HSCs in Lin⁻ cell populations.

<p>(<b>A</b>) Western blotting analysis for Angptl3 expression in sorted Lin⁻ GFP⁺ cells 2 days following transduction with LV-Angptl3-GFP or the mock control LV-GFP lentiviral particles. (<b>B</b>) Total cell fold expansion and (<b>C</b>) fold increase in BFU-E or CFU-GM progenitor colonies from transduced Lin⁻ GFP⁺ cells as described under (A) that were cultured for 4 or 7 days. Results are shown relative to day 0, transduced sorted Lin⁻ cells. Mean values are obtained from 5 independent experiments. (<b>D</b>) Short-term colony forming unit assay (CFU- S). Lin⁻ GFP⁺ cells were sorted 2 days post transduction and immediately transplanted into lethally irradiated mice. Total numbers of CFU-S colonies in the spleen were counted after 12 days following transplantation (N = 10 mice). *<i>P</i>≤0.05.</p