Recent evidence put forth by our group and others suggests type 1 diabetes (T1D) pathogenesis involves a combination of immune, islet, and acinar pancreas defects. In addition to autoimmunity and β-cell death, it has become clear that T1D is characterized by a whole-organ pathology with reduced pancreas size, reduced exocrine enzyme levels in serum, and altered α- and β-cell function, including impaired insulin processing, even in the islet autoantibody positive (AAb+) pre-T1D condition. Hence, there is a need to understand each of these facets in concert, linking cellular phenotype and function, together with studies of the human pancreas tissue microenvironment, throughout T1D progression. We hypothesize that alterations to β-cell status and its surrounding environment are key determinants of impaired β-cell function, exocrine function, and infiltration (insulitis). We propose to assay islet and acinar tissue function using our novel pancreas slice culture platform (Aim 1a) to test (pro)hormone (proinsulin, insulin, glucagon) and enzyme (lipase, trypsinogen) secretion from T1D, AAb+, and control organ donor pancreata in response to established endocrine (glucose, arginine, KCl) and exocrine stimuli (cholecystokinin, carbachol). We will correlate these functional data with molecular features via scRNAseq (single cell RNA sequencing) with antibody-based CITEseq (Cellular Indexing of Transcriptomes and Epitopes) and scATACseq (single cell assay for transposase-accessible chromatin sequencing); this, for the purpose of cell identification together with transcriptomic and epigenomic analyses (Aims 1b). Pancreas slices will also be subjected to these same stimulatory conditions for live cellular imaging of Ca2+ signalling activity within islet and acinar tissue areas in real time (Aim 2a), then fixed and analyzed by imaging mass cytometry (IMC). We will assess in situ expression of 120 immune and pancreas cell markers with cellular resolution (Aim 2b), followed by spatial and temporal analysis of IMC data to determine how islet, immune and acinar cell phenotypes correlate with tissue and cellular function, using our histoCAT (histology topography cytometry analysis toolbox). This will enable computational analysis with 3D reconstruction from serial sections (Aim 2c). Finally, in Aim 3, human donor pancreas slices will be subjected to diabetogenic stimuli (inflammatory cytokines, glucotoxicity) and interventions targeting β-cell stress [imatinib (tyrosine kinase inhibitor), MSL-7 (autophagy enhancer), exenatide (GLP-1 receptor agonist)], and similarly evaluated by single cell and IMC profiling. With over 14 years of experience in procurement of transplant-quality human pancreata through the Network for Pancreatic Organ donors with Diabetes (nPOD), we are uniquely poised to perform the proposed studies. We expect to identify altered molecular pathways and tissue features linking β-cell, whole-islet, and acinar cell phenotypes with cellular function in AAb+ and T1D pancreata. We anticipate these same defects will arise in slices subjected to diabetogenic stimuli, providing a platform to test known and novel candidates for targeted intervention to reduce β-cell stress, restore islet and acinar cell function, as well as prevent disease progression.

The three principal investigators affiliated with this proposal have pioneered studies uncovering a potential role for the endocrine and exocrine pancreas in type 1 diabetes (T1D), including: 1) characterizing T1D development in organ donor pancreata (Atkinson); 2) the use of imaging mass cytometry (IMC) for simultaneous in situ detection of over 40 validated protein and mRNA molecules, now with 120 validated targets in human pancreas tissue (Bodenmiller); and 3) utilizing pancreas tissue slice culture to assess islet and acinar cell function by live cellular imaging of Ca2+ signaling, as well as endocrine hormone and exocrine enzyme secretion (Speier). Herein, we propose to apply these techniques, along with single cell transcriptomic and epigenomic profiling, in fresh organ donor pancreata to address the hypothesis that altered β-cell status and the surrounding microenvironment contribute to impaired insulin processing, altered islet and exocrine cell function, and insulitis during T1D progression. We expect these studies to link cellular dysfunction, phenotype, and organization in the pre-T1D and T1D conditions, thereby identifying an integrated T1D signature at the islet↔immune↔exocrine interface, providing novel insights into disease mechanisms and therapeutic interventions.