Purpose of Review Novel 3D organoid culture techniques have enabled long-term expansion of pancreatic tissue. This review comprehensively summarizes and evaluates the applications of primary tissue... Show morePurpose of Review Novel 3D organoid culture techniques have enabled long-term expansion of pancreatic tissue. This review comprehensively summarizes and evaluates the applications of primary tissue-derived pancreatic organoids in regenerative studies, disease modelling, and personalized medicine.Recent Findings Organoids derived from human fetal and adult pancreatic tissue have been used to study pancreas development and repair. Generated adult human pancreatic organoids harbor the capacity for clonal expansion and endocrine cell formation. In addition, organoids have been generated from human pancreatic ductal adenocarcinoma in order to study tumor behavior and assess drug responses.Summary Pancreatic organoids constitute an important translational bridge between in vitro and in vivo models, enhancing our understanding of pancreatic cell biology. Current applications for pancreatic organoid technology include studies on tissue regeneration, disease modelling, and drug screening. Show less
Eggers, R.; Winter, F. de; Arkenaar, C.; Tannemaat, M.R.; Verhaagen, J. 2019
The aim of this thesis was to investigate the feasibility of multimodal visualization techniques to observe adult stem cells, in particular HFBSCs, in the living animal. Due to the novelty of... Show moreThe aim of this thesis was to investigate the feasibility of multimodal visualization techniques to observe adult stem cells, in particular HFBSCs, in the living animal. Due to the novelty of HFBSCs in the field of inner ear research, a series of proof-of-principle experiments have been undertaken to investigate if these cells can undergo neuronal differentiation, tolerate genetic modification with lentiviral constructs containing the genes coding for reporter proteins, and tolerate subsequent loading with nanoparticles in vitro. In addition, it was of importance to examine if HFBSCs do integrate into modiolar tissue and if they can be visualized in the cochlea of the guinea pig. Lastly, we performed in vivo studies to investigate the ototoxic effect of ouabain in guinea pigs and the behavior of HFBSCs in mice with traumatic brain injury. Show less
Hydrogen peroxide (H2O2) is produced following injury and is required for regeneration. However, how H2O2 coordinates multiple signalling pathways required for regeneration is not known. Protein... Show moreHydrogen peroxide (H2O2) is produced following injury and is required for regeneration. However, how H2O2 coordinates multiple signalling pathways required for regeneration is not known. Protein-tyrosine phosphatases (PTPs) are regulators of signal transduction, reversing the phosphorylation of substrates, and are essential for many cellular processes. PTPs are also highly sensitive to reversible oxidation-mediated inhibition by H2O2.My research identified that some, but not all, PTPs become oxidized following amputation of the zebrafish caudal fin, and implicates PTPs that are oxidized as necessary for the regenerative process. Furthermore, I delineated that the PTPs Shp2 and Pten are required for the regenerative outgrowth phase of regeneration, and that Shp2 and Pten have a role in driving MAPK signalling and balancing PI3K signalling, respectively, during this phase. Show less
The development of methods for the genetic modification of plants a few decades ago has provided a tremendous boost for molecular plant science. Crop plants have been generated that are... Show moreThe development of methods for the genetic modification of plants a few decades ago has provided a tremendous boost for molecular plant science. Crop plants have been generated that are resistant to insects or herbicides, or that produce useful sugars or healthy nutrients. Although the ban on growing GM crops in Europe has considerably limited the application of GM technologies, they have still contributed considerably to fundamental plant science. Especially by using the natural and very efficient mechanism of DNA transfer by the soil born bacterium Agrobacterium tumefaciens, many collections of mutant lines of model plant species such as Arabidopsis and rice have been generated, in which genes are disrupted or overexpressed by the insertion of an Agrobacterium transfer DNA (T-DNA) construct. These collections have been used in forward or reverse genetics studies to unravel the function of a gene or a family of genes in plant defense or development, and to identify the key regulators in these processes. The study described in this thesis focused on the use of one of these key regulators, the Arabidopsis AT-HOOK MOTIF NUCLEAR LOCALIZED PROTEIN 15/REJUVENATOR (AHL15/RJV), to alter developmental processes such as flowering, senescence and regeneration. Show less
In this thesis, in close collaboration with my research colleagues, I have shown that T-cell recruitment in both spontaneous autoimmune diabetes and islet transplantation requires presence... Show more In this thesis, in close collaboration with my research colleagues, I have shown that T-cell recruitment in both spontaneous autoimmune diabetes and islet transplantation requires presence of a cognate antigen, which could be used as an argument in favour of further pursuing antigen-specific therapies. We have shown that recurrent diabetes in an islet transplantation model is driven by memory auto reactive T-cells and this latter finding has contributed to the present testing of immune suppressive drugs that indeed address recurrent autoimmunity, to improve outcome in clinical islet transplantation. We have designed and tested a novel auto-immune diabetes cell line tracing model for future testing of the regenerative capacity of islet-cells. We have shown that immune evasion protects beta-cells from autoimmune T-cell attack in vivo. Currently different immune evasion techniques, such as islet encapsulation are being tested in the clinic. We have shown that recall immunity is preserved in spite of high dose anti-CD3 treatment, adding to the safety of high dose anti-CD3 treatment as an immune modulator agent in the treatment of T1DM. Show less
This thesis is dedicated to the study of random walks in dynamic random environments. These are models for the motion of a tracer particle in a disordered medium, which is called a static random... Show moreThis thesis is dedicated to the study of random walks in dynamic random environments. These are models for the motion of a tracer particle in a disordered medium, which is called a static random environment if it stays constant in time, or dynamic otherwise. The evolution of the random walk is defined by assigning to it random jump rates which depend locally on the random environment. Such models belong to the greater area of \emph{disordered systems}, and have been studied extensively since the early seventies in the physics and mathematics literature. The goal is to understand the scaling properties, as time goes to infinity, of the path of the random walk. Several results are available in the literature for dynamic random environments which are uniformly elliptic and have uniform and fast enough mixing in space-time. However, very little is known when either of these conditions fail. In this thesis, we study examples of such situations, namely, non-elliptic cases in Chapter 2, a dynamic random environment with fast but non-uniform mixing in Chapter 4, and a dynamic random environment with both slow and non-uniform mixing in Chapters 3 and 5. Show less
The aim of this thesis was to investigate the expression, and function of genes associated with remodelling and regeneration in the zebrafish model species. Here, we studied the role of cell... Show moreThe aim of this thesis was to investigate the expression, and function of genes associated with remodelling and regeneration in the zebrafish model species. Here, we studied the role of cell populations, defined by their expression of markers, in bone regeneration and remodelling in zebrafish embryos and adult zebrafish scales. We used mesoporous silica nanoparticles to carry cytokines, known to activate hematopoietic cells into osteoclasts, into tissues of the living embryo. We further investigated the role of genes such as matrix metalloproteinases in regeneration of adult zebrafish scales. These genes are known to be involved in matrix degradation and have been found to be expressed in mammalian osteoclasts. We studied both by in situ hybridisation and immunocytochemistry the presence of mononucleated and multinucleated mmp-9 positive cells on the episquamal side of adult zebrafish scales. Finally we studied the regeneration of the caudal fin of zebrafish embryos with a special emphasis on the effect of glucocorticoids on regeneration and wound healing. Glucocorticoids in this case mimic stress conditions in the embryos, thus helping understand the effect of early exposure to stress on wound healing and tissue Remodelling. Show less
While currently available therapeutic options for the treatment of acute myocardial infarction are sufficient for the treatment of symptoms, the underlying causes usually remain unresolved, being... Show moreWhile currently available therapeutic options for the treatment of acute myocardial infarction are sufficient for the treatment of symptoms, the underlying causes usually remain unresolved, being loss of electrically active, contractile, myocardial tissue. Recently, extensive research has been performed in the field of cell and gene therapy. The ultimate aim of these therapies is to __heal__ the infarcted area on a more biological basis, by repopulating the damaged area with __new__ cells that contribute to proper cardiac function, including electrical activation of the myocardium. In order to comprehend the potential therapeutic value and hazard of cell modification and transplantation for ischemic heart diseases, one should consider the heart as a highly integrative, electromechanical organ. Therefore, the aim of this thesis was to explore, from a mechanistic and electrophysiological point of view, the integrative and functional aspects of cell modification and transplantation as therapeutic options to cure the damaged, ischemic heart. Show less
In this thesis, the possibilities and limitations of cell-based therapies after spinal cord injury are explored. Particularly, the potential of adult derived neural progenitor cell (NPC) grafts to... Show moreIn this thesis, the possibilities and limitations of cell-based therapies after spinal cord injury are explored. Particularly, the potential of adult derived neural progenitor cell (NPC) grafts to function as a permissive substrate for axonal regeneration was investigated. It was found that syngenic adult derived neural progenitor cells are able to survive transplantation in the acutely lesioned spinal cord and differentiate into glial phenotypes. When co-grafted with fibroblasts, glial fibrillary acidic protein expressing grafted NPC are able to replace the lesion defect and are able to induce contact mediated axon guidance and regenerative sprouting. NPC that are co-grafted with highly purified Schwann cells however migrate away from the lesion site, which is paralleled with a reduced axonal outgrowth. A close investigation of NPC that are transduced to express ectopic genes by using different viral vectors revealed that in vivo gene expression in genetically engineered neural progenitor cells is temporally limited and mostly restricted to undifferentiated NPC. Finally, MRI imaging at 17.6 Tesla was used to in vivo monitor structural changes following spinal cord injury in rats, enabling future longitudinal studies that allow direct correlation of structure with function. Show less
