Abstract
BACKGROUNDPathophysiology of type 1 diabetes (T1D) is illustrated by pancreatic islet infiltration of inflammatory lymphocytes, including CD8+ T cells; however, the molecular factors mediating their recruitment remain unknown. We hypothesized that single-cell RNA-sequencing (scRNA-Seq) analysis of immune cell populations isolated from islets of NOD mice captured gene expression dynamics providing critical insight into autoimmune diabetes pathogenesis.METHODSPancreatic sections from human donors were investigated, including individuals with T1D, autoantibody-positive (aAb+) individuals, and individuals without diabetes who served as controls. IHC was performed to assess islet hormones and both novel and canonical immune cell markers that were identified from unbiased, state-of-the-art workflows after reanalyzing murine scRNA-Seq data sets.RESULTSComputational workflows identified cell adhesion molecule 1–mediated (Cadm1-mediated) homotypic binding among the most important intercellular interactions among all cell clusters, as well as Cadm1 enrichment in macrophages and DCs from pancreata of NOD mice. Immunostaining of human pancreata revealed an increased number of CADM1+glucagon+ cells adjacent to CD8+ T cells in sections from T1D and aAb+ donors compared with individuals without diabetes. Numbers of CADM1+CD68+ peri-islet myeloid cells adjacent to CD8+ T cells were also increased in pancreatic sections from both T1D and aAb+ donors compared with individuals without diabetes.CONCLUSIONIncreased detection of CADM1+ cells adjacent to CD8+ T cells in pancreatic sections of individuals with T1D and those who were aAb+ validated workflows and indicated CADM1-mediated intercellular contact may facilitate islet infiltration of cytotoxic T lymphocytes and serve as a potential therapeutic target for preventing T1D pathogenesis.FUNDINGThe Johns Hopkins All Children’s Foundation Institutional Research Grant Program, the National Natural Science Foundation of China (grant 82071326), and the Deutsche Forschungsgemeinschaft (grants 431549029–SFB1451, EXC2030–390661388, and 411422114-GRK2550).
Highlights
Type 1 diabetes (T1D) is characterized by hyperglycemia resulting from the autoimmune destruction of the insulin-expressing beta-cells of the pancreas [1,2,3]
Cadm1 expression in macrophages and dendritic cells isolated from the pancreas of non-obese diabetic (NOD) mice, a model of autoimmune diabetes [25]. Consistent with these observations, numbers of peri-islet CADM1+CD68+ myeloid cells adjacent to CD8+ T-cells were increased in pancreatic sections from both type 1 diabetes (T1D) and aAb+ human subjects compared to non-diabetic subjects indicating
Single-cell RNA sequencing analysis was performed on 42,140 total cells isolated from pancreatic islets from the non-obese diabetic (NOD) autoimmune mouse model at ages 4, 8, and 15 weeks to capture the progression of the disease [25]
Summary
Type 1 diabetes (T1D) is characterized by hyperglycemia resulting from the autoimmune destruction of the insulin-expressing beta-cells of the pancreas [1,2,3]. Important advances have been made in identifying islet cell molecules that are targeted during the autoimmune response during T1D, including the native protein and epitopes of proinsulin [9,10,11,12,13], islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) [14], GAD65 [15], insulinoma-associated antigen 2 (IA-2) [16], chromogranin [17], and islet-amyloid polypeptide [18] Despite this progress in understanding islet pathology during T1D [6, 7, 19], key conceptual gaps still remain in understanding the mechanisms that instigate immune cell infiltration and their recognition of beta cells. We hypothesized that single-cell RNA-sequencing (scRNA-Seq) analysis of immune cell populations isolated from islets of non-obese diabetic (NOD) mice captured gene expression dynamics providing critical insight into autoimmune diabetes pathogenesis
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