The glioma microenvironment harbors a variety of immune cells including innate immune cells such as monocytes, macrophages and microglia. Microglia are the major innate immune cells present in the... Show moreThe glioma microenvironment harbors a variety of immune cells including innate immune cells such as monocytes, macrophages and microglia. Microglia are the major innate immune cells present in the glioma microenvironment. Communication between glioma and these immune cells is crucial to maintain a tumor-promoting environment. In this thesis the role of a specific type of communication is described. In detail, the consequence of extracellular communication from glioma to the innate immune cells is studied, this includes the transferring of messages (including miRNAs) through extracellular vesicles. In addition, the changes that these cells undergo in the presence of a tumor is documented. Show less
Abnormal vascular physiology and precipitating inflammatory pathways underlie many different diseases, including hemorrhage, stroke, vascular dementia and even cancer. Pluripotent stem cells (PSCs)... Show moreAbnormal vascular physiology and precipitating inflammatory pathways underlie many different diseases, including hemorrhage, stroke, vascular dementia and even cancer. Pluripotent stem cells (PSCs) can now be derived by reprogramming from any individual so that it is possible in principle to derive all somatic cells of the human body that would normally be difficult to access. In this thesis, I studied the derivation of myeloid cells from human induced pluripotent stem cells (hiPSCs) to model the inflammatory component of vascular disease and characterized the development path of hiPSC-derived endothelial cells (hiPSC-ECs) which form the vascular walls. Functional defects in either of these cell types can cause or exacerbate vascular disease. I then used these cell types to gain insight into the mechanisms underlying two genetic diseases: Hereditary Hemorrhagic Telangiectasia (HHT) which is caused by mutations in a gene called Endoglin expressed on cells of the vascular wall and inflammatory macrophages, and a vascular tumor called Pseudomyogenic hemangioendothelioma (PHE) in which endothelial cells are thought to be the tumor cell of origin. I developed new differentiation protocols to generate inflammatory cells from hiPSC, characterized these cells functionally and used Next-Generation Sequencing and bioinformatic analysis to gain insight into the molecular pathways controlling development of one particular type of endothelial cells from hiPSC and the underlying tumorigenic mechanisms of PHE. Show less
Atherosclerosis is one of the primary causes of cardiovascular disease; the number one cause of death in the western society. Atherosclerotic plaque formation is a dynamic multi-cellular process... Show moreAtherosclerosis is one of the primary causes of cardiovascular disease; the number one cause of death in the western society. Atherosclerotic plaque formation is a dynamic multi-cellular process where regulation of different genes essentially determines the activity of the different cell types involved. Gene expression is regulated, amongst others, by epigenetic processes. Epigenetic mechanisms change the accessibility of the DNA sequence and is thought to form a link between environmental factors and gene expression. Epigenetics may therefor play an important role in atherosclerosis pathology. The research described in this thesis evaluated the role of epigenetic regulation on various aspects of atherosclerosis pathology. It was found that the epigenetic H3K27Me3-mark was reduced in later stages of the disease. Monocytes differentiating into dendritic cells and macrophages (an important process in atherosclerosis pathology) showed higher transcription of the epigenetic regulatory gene KMT1c. Specifically blocking this gene resulted in reduction of DC-SIGN (a dendritic cell specific molecule) expression. By specifically blocking other epigenetic proteins, CCR5 (a molecule important to monocyte migration) was re-expressed on cells which did not express CCR5. This shows that epigenetic regulation is an important process in atherosclerosis pathology and might prove to be novel pharmacological target for treatment of atherosclerosis. Show less
The work described in this thesis focussed on the modes of action of maggot therapy in chronic wounds, especially related to the inflammatory phase of wound healing. For this purpose, the effect of... Show moreThe work described in this thesis focussed on the modes of action of maggot therapy in chronic wounds, especially related to the inflammatory phase of wound healing. For this purpose, the effect of maggot excretions and/or secretions on microbiological, haematological and immunological processes was investigated. The results showed that maggot excretions/secretions breakdown biofilms of both Gram-positive and Gram-negative bacteria, exposing them to the immune system, antibiotics, and ingestion and subsequent degradation by the maggots. Furthermore, proteases in maggot secretions enhance debridement by increasing the fibrinolytic activity of wound components and by degrading matrix components directly. Additionally, maggot secretions inhibit the pro-inflammatory responses of phagocytes but do not affect their ability to ingest and intracellularly kill micro-organisms. Finally, secretions induce the production of growth factors essential for angiogenesis. In conclusion, the results described in this thesis provide new insights into the modes of action of maggot therapy in chronic wounds. The success of maggot therapy may be explained by the broad spectrum of processes that are modulated by maggot secretions. Show less
