Work described in this thesis was aimed to further understand the role of macrophages in acute cellular rejection of transplanted kidneys, and perform a pre-clinical assessment of the localization... Show moreWork described in this thesis was aimed to further understand the role of macrophages in acute cellular rejection of transplanted kidneys, and perform a pre-clinical assessment of the localization and efficacy of liposomal prednisolone. First, we explored the role of anti-inflammatory macrophages in the onset of acute cellular rejection using human biopsy samples. Here, we discovered that the presence of high levels of CD163+ macrophages was associated with a lower risk of rejection, in a population of patients with a high rate of delayed graft function. Subsequently, we identified the ability of liposomal prednisolone to target macrophages in the kidney using in vitro models of human macrophages, and their ability to accumulate in inflamed kidney tissue in vivo rat models of ischemia reperfusion injury in the kidney. Finally, we evaluated the treatment efficacy of liposomal prednisolone in a mouse model of cellular rejection following kidney transplantation. Here, we were able to show an improved efficacy of liposomal prednisolone in treating rejection, when compared to treatment with free prednisolone. Show less
Chronic energy surplus causes obesity and promotes insulin resistance and type 2 diabetes (T2D). A major contributor to insulin resistance is chronic, low-grade inflammation in metabolic tissues,... Show moreChronic energy surplus causes obesity and promotes insulin resistance and type 2 diabetes (T2D). A major contributor to insulin resistance is chronic, low-grade inflammation in metabolic tissues, also coined metaflammation. In this context, white adipose tissue and liver-resident innate and adaptive immune cells produce proinflammatory cytokines that exacerbate inflammation and inhibit canonical insulin signaling. Among them, macrophages and dendritic cells were shown to play central roles in metaflammation, although the environmental and cellular changes dictating proinflammatory activation in the context of obesity are not fully understood. This thesis describes novel mechanisms by which macrophages and dendritic cells control metabolic homeostasis in obese mice. In addition, we show that immunomodulatory molecules derived from parasitic worm eggs promote an immune response in metabolic tissues that maintains insulin sensitivity. Finally, we describe the pleiotropic beneficial effects of a novel plant-derived nutritional supplement on metaflammation and metabolic homeostasis in obese mice. Altogether, this work may provide new leads for interventions aimed at improving immunological control of metabolic dysfunctions. Show less
Transplantation is the golden standard for the treatment of end-stage renal disease. During this process, the transplanted organ is often damaged. In this thesis, we investigated whether activation... Show moreTransplantation is the golden standard for the treatment of end-stage renal disease. During this process, the transplanted organ is often damaged. In this thesis, we investigated whether activation of the complement system, part of our innate immune system, plays a local role. We reviewed that properdin, the only known positive regulator of the complement system, was detected in serum, plasma and urine from patients with various complement-mediated renal diseases. In protocol biopsies obtained 10 days after transplantation, properdin was found deposited in addition to complement activation markers. Next, we showed that dendritic cells secrete properdin and a decrease in properdin levels during dendritic cell- T-cell interaction resulted in reduced T-cell proliferation and activation. We also showed that properdin is able to bind to surfaces of both viable and dead cells, contributing to complement activation. Macrophages can also produce properdin and negative regulators factor H and its splice variant FHL-1. Increasing knowledge on complement factor production by other cells than hepatocytes, including immune cells, hints towards a local role of the complement system in various processes. These findings contribute to a better understanding of the local role of the complement system and are important for the applications of (new) complement-inhibiting drugs. Show less
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
For many years, cancer has been described as the accumulation of germinal and somatic mutations of the genome, impairing the function of tumor suppressor genes and stimulating oncogenes. Nowadays,... Show moreFor many years, cancer has been described as the accumulation of germinal and somatic mutations of the genome, impairing the function of tumor suppressor genes and stimulating oncogenes. Nowadays, it is commonly accepted that the tumor is not only a mass of malignant cells, rather than the result of a delicate network of interactions between tumor and stromal cells. Indeed, bidirectional communications between cancer cells and the surrounding microenvironment can strongly influence tumor development and progression. Stromal cells might support tumorigenesis, either via direct cell-cell contact mechanisms with tumor cells, or by releasing specific factors, including cytokines and growth factors in the surrounding extracellular matrix (ECM), with remodeling of the tumor microenvironment (TME) as a result.The aim of this thesis is to elucidate the delicate network of interactions between different TME components and tumor cells in prostate cancer (PCa) and oropharyngeal squamous cell carcinoma (OPSCC). 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
Hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease, is a rare genetic disorder, known for its endothelial dysplasia causing vessel malformations, severe nose bleeds and... Show moreHereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease, is a rare genetic disorder, known for its endothelial dysplasia causing vessel malformations, severe nose bleeds and internal bleedings. In the majority of patients mutations are found in genes belonging to the TGFβ superfamily, causing a disbalance in the TGFβ signaling pathway by haploinsufficiency of the remaining functional protein. In this thesis we studied different aims and approaches to influence HHT1-MNC homing and differentiation to restore their contribution to tissue repair. In various experimental methods inducing ischemic and/or direct tissue damage, we aimed to improve tissue repair in the Eng+/- mice. Using DPP4 inhibition, we increased the SDF1-CXCR4 homing mechanism, to restore the impaired homing capacity of the HHT1-MNCs. Furthermore, we focused on correcting the M1/M2 differentiation in Eng+/- mice. Via use of the BMP receptor inhibitor LDN we aimed to restore the skewed BMP/TGFβ signaling; stimulating the TGFβ pathway signaling to induce M2 differentiation. We concluded that DPP4 inhibition can be used to improve the HHT1 immune system and tissue repair, and is best used in concert with other drugs or therapies that stimulate cardiac or tissue repair, like anti-coagulants or cell therapy. Show less
This thesis focuses on the relationship between smoking and macrophages in chronic obstructive pulmonary disease (COPD), and on treatment with inhaled corticosteroids (ICS). Macrophages play an... Show moreThis thesis focuses on the relationship between smoking and macrophages in chronic obstructive pulmonary disease (COPD), and on treatment with inhaled corticosteroids (ICS). Macrophages play an important role in COPD, and constitute a heterogeneous population with pro- (Mf1) and anti-inflammatory (Mf2) cells. This thesis evaluated YKL-40 and CD163 as markers for Mf1 and Mf2, respectively. Peripheral airways contained more CD163-positive Mf2 compared to central airways. Smoking cessation skewed the macrophage phenotype towards Mf2 in the peripheral airways, but did not influence YKL-40 levels in sputum. Whereas smoking can induce structural alterations in extracellular matrix (ECM) components in the airways, no differences in ECM components in bronchial biopsies were found between current and ex-smokers with COPD. ICS treatment attenuates lung function decline and decreases airway inflammation in a subgroup of COPD patients. However, long-term ICS treatment did not change YKL-40 levels in sputum and serum. ICS increased deposition of several ECM proteins in the airways, which was correlated with improved lung function, suggesting prevention of airway collapse. Withdrawal of ICS after long-term treatment induced a relapse in lung function decline and increased airway inflammation in bronchial biopsies and sputum, suggesting that benefits of ICS do not persist after discontinuation of ICS. Show less
