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Type 1 diabetes (T1D) is characterized by elevated glucose levels as a consequence of loss of insulin secretion by endocrine beta cells in the islets of Langerhans in the pancreas. In T1D it is well established that the insulin-producing beta cells are destroyed by an auto-immune attack. Early T1D beta cells are characterized by upregulation of HLA class 1, endoplasmic reticulum stress and apoptosis, which can all be evoked within an inflammatory environment (Kracht et al. 2017; Marroqui et al. 2017). However, the trigger for these events remains elusive.
Pilot electron microscopy studies revealed the cellular mixing of acinar cells from the exocrine pancreas, which produce digestive enzymes, with the endocrine cells within the islets of Langerhans in the early stages of T1D in both human patient material (manuscript in preparation) and a T1D rat model (Scotuzzi et al. 2017). The cause of this endocrine-exocrine cell mixing is unknown. Moreover, T1D patients have a reduced pancreas organ weight, which cannot be explained only by the loss of islets, since islets comprise just a few percent of the total pancreas. Furthermore, increased immune cell infiltrates have been found in the exocrine pancreas, suggesting a role for the exocrine pancreas in the pathogenesis of T1D.
Interactions between the exocrine and endocrine pancreas in the development of T1D have gained increasing attention, and include reports on immune infiltrates in the exocrine pancreas during T1D and a reduced total pancreatic weight in T1D patients compared to controls (Campbell-Thompson, Rodriguez-Calvo, and Battaglia 2015; Campbell-Thompson et al. 2016). We hypothesize that initial damage to exocrine cells in the pancreas causes the release of (auto)digestive proteins, which subsequently trigger beta cell stress that ultimately result in an autoimmune response that is characteristic for T1D.
The overall aim of the project is to investigate the interactions between exocrine acinar cells and endocrine beta cells in the early pathogenesis of type 1 diabetes and the potential role in triggering T1D.
Advanced electron microscopy (EM), color EM that will allow high throughput analysis of Islet morphology up to the ultrastructural level and that allows discrimination of cellular hormones versus enzymes will be applied as described before (Scotuzzi, 2017; Ravelli 2013).
A patient-specific human pancreas cell culture model for the study of exocrine-endocrine interactions will be developed. For this Induced pluripotent stem cells (iPSC) will be generated from fresh urine-derived cells donated by healthy control individuals and (HLA genotyped) patients diagnosed with Type 1 diabetes. The iPSC will be differentiated to exocrine acinar cells and endocrine beta cells according to published protocols. 3D co-culture systems will be used to study exocrine-endocrine cell interactions. The responses of patient- or control-derived beta cells on exocrine lysate will be studied using cytokine and chemokine production (ELISA, RT-PCR).
Patient-derived induced pluripotent stem cells and thereof derived exocrine and endocrine pancreatic cells allow the investigation of patient-specific disease pathogenesis and responsiveness to therapeutic interventions.
Patient-derived induced pluripotent stem cells and thereof derived exocrine and endocrine pancreatic cells allow: