Development of a cell encapsulation technology for the production of functional, micro-encapsulated pancreatic islets for transplantation

Previously held under moratorium from 8 August 2019 until 9 December 2021Diabetes type 1 is an autoimmune disease in which the patient’s own immune system destroys the insulin producing β-cells, located in the pancreatic islets. Without enough insulin production, the blood glucose levels of the patient rise, which can lead to damages of blood vessels and nerves, blindness or even seizures and comas. For some patients that have trouble maintaining normoglycaemia allogeneic islet transplantation has become an alternative treatment option. Patients with these transplanted islets are no longer prone to hypoglycaemic episodes and can sometimes become completely insulin independent. However, this success is not long-lived. The life span of the transplanted islets is limited due to the host’s immune responses and the toxicity of modern immunosuppressive agents. In this thesis, islet encapsulation for clinical transplantation is investigated and further developed. Islet encapsulation can protect the islets from the immune system, without the aid of the immunosuppressants. The construction and optimization of a micro-encapsulator that can be used to create encapsulations is described, as well as the multiple parameters to create small, uniform encapsulations. To further enhance the biocompatibility and immunoprotective properties of alginate hydrogel, alginate was purified to eliminate most of the impurities and tested for its permeability. Encapsulating pancreatic islets in this purified alginate showed encouraging results, with the islets remaining viable and functional longer than their control counterparts. Larger islets can develop necrotic cores within encapsulations, due to the lack of vascularization. To create smaller islets out of dissociated larger islets, a single-step encapsulation and aggregation method was developed, that unfortunately was not suitable for islet cells, but was capable of developing functional hepatic organoids out of HepaRG cells, that could be used for drug testing. Finally, a proof of principle was given for the creation of pancreatic islet patches using 3D bioprinting methods.Diabetes type 1 is an autoimmune disease in which the patient’s own immune system destroys the insulin producing β-cells, located in the pancreatic islets. Without enough insulin production, the blood glucose levels of the patient rise, which can lead to damages of blood vessels and nerves, blindness or even seizures and comas. For some patients that have trouble maintaining normoglycaemia allogeneic islet transplantation has become an alternative treatment option. Patients with these transplanted islets are no longer prone to hypoglycaemic episodes and can sometimes become completely insulin independent. However, this success is not long-lived. The life span of the transplanted islets is limited due to the host’s immune responses and the toxicity of modern immunosuppressive agents. In this thesis, islet encapsulation for clinical transplantation is investigated and further developed. Islet encapsulation can protect the islets from the immune system, without the aid of the immunosuppressants. The construction and optimization of a micro-encapsulator that can be used to create encapsulations is described, as well as the multiple parameters to create small, uniform encapsulations. To further enhance the biocompatibility and immunoprotective properties of alginate hydrogel, alginate was purified to eliminate most of the impurities and tested for its permeability. Encapsulating pancreatic islets in this purified alginate showed encouraging results, with the islets remaining viable and functional longer than their control counterparts. Larger islets can develop necrotic cores within encapsulations, due to the lack of vascularization. To create smaller islets out of dissociated larger islets, a single-step encapsulation and aggregation method was developed, that unfortunately was not suitable for islet cells, but was capable of developing functional hepatic organoids out of HepaRG cells, that could be used for drug testing. Finally, a proof of principle was given for the creation of pancreatic islet patches using 3D bioprinting methods