Transplant recipients generally require lifelong treatment with immunosuppressive medication to prevent rejection of the graft by their immune system. Inhibitors of the enzyme calcineurin,... Show moreTransplant recipients generally require lifelong treatment with immunosuppressive medication to prevent rejection of the graft by their immune system. Inhibitors of the enzyme calcineurin, including cyclosporin A and tacrolimus, constitute a very potent class of immunosuppressants that has revolutionized transplant medicine. However, their reputation has been showing cracks due to the severe side-effects associated with long-term use of these drugs, including an explosively increased risk of developing skin cancer. The pathophysiological mechanism of this phenomenon is not known, although a number of hypotheses have been put forward. In this dissertation, we show that oxidative stress, mainly derived from exposure to UVA radiation, may locally augment the effects of the calcineurin inhibitors; we propose that overly strong suppression of calcineurin activity may result in malignancy formation due to disruption of tumor-suppressive signaling pathways or disturbed immunosurveillance in skin. Show less
Pancreas transplantation and islet of Langerhans transplantation are potential solutions to treat patients with type 1 diabetes. However, pancreas grafts are scarce and there is a shortage of donor... Show morePancreas transplantation and islet of Langerhans transplantation are potential solutions to treat patients with type 1 diabetes. However, pancreas grafts are scarce and there is a shortage of donor pancreata relative to the number of patients needing a transplant. The aim of this thesis was to further optimize pancreas graft survival in pancreas transplantation and to optimize islet isolation outcomes in islet of Langerhans transplantation, leading to better use of available organs. The focus in pancreas transplantation should be on optimizing recipients to improve graft survival and on improving quality of pancreata procured by centers not performing pancreas transplantation (for example, by training procurement surgeons to optimize pancreas procurement, thereby increasing the number of transplantable organs. In islets transplantation, it is recommended that the reporting of donor, pancreas and isolation factors should become more standardized, which would enable us to determine more accurately which factors are important predictors for islet isolation outcome. Furthermore, if more biomedical factors (e.g. the presence of hyperemic islets) would be reported in addition to the other factors, we would be able to assess the independent effect of these biomedical factors for islet isolation outcome and eventually the effect on islet transplantation in the clinical setting. Show less
This thesis reports the isolation, characterization and allotransplantation in porcine retina of ciliary epithelium (CE)-derived cells, also known as retinal stem cells (RSCs). The self-renewal... Show moreThis thesis reports the isolation, characterization and allotransplantation in porcine retina of ciliary epithelium (CE)-derived cells, also known as retinal stem cells (RSCs). The self-renewal capacity and differentiation potential of these cells in vitro and in vivo makes them candidate donors in cell replacement approaches for treating retinal degenerative diseases. The use of pig as the animal model should facilitate translation of these findings to applications for human conditions. The work described in this thesis shows that cultures of self-renewing cells can be obtained in vitro from the newborn porcine CE and that these cells can differentiate into retinal and RPE phenotypes both in vitro and in vivo after transplantation in adult pigs. However, the nature and physiological role of these cells in potential endogenous repair mechanisms still remain to be explored. Notably, their remarkable plasticity in vitro makes them an interesting cell model to study this phenomenon of recent identification. Show less
This thesis describes the clinical significance of thebiomarker C4d, a split product of the complement system, in several manifestations of systemic autoimmunediseases such as SLE and... Show moreThis thesis describes the clinical significance of thebiomarker C4d, a split product of the complement system, in several manifestations of systemic autoimmunediseases such as SLE and antiphospholipid syndrome. The findings in this thesis suggest that this biomarker might be of use in unraveling disease mechanisms where complement activation is involved, as well as serving as a diagnostic tool to detect patients at risk of antibody mediated tissue injury Show less
