Publications by authors named "Diane C Saunders"

13 Publications

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Combinatorial transcription factor profiles predict mature and functional human islet α and β cells.

JCI Insight 2021 09 22;6(18). Epub 2021 Sep 22.

Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA.

Islet-enriched transcription factors (TFs) exert broad control over cellular processes in pancreatic α and β cells, and changes in their expression are associated with developmental state and diabetes. However, the implications of heterogeneity in TF expression across islet cell populations are not well understood. To define this TF heterogeneity and its consequences for cellular function, we profiled more than 40,000 cells from normal human islets by single-cell RNA-Seq and stratified α and β cells based on combinatorial TF expression. Subpopulations of islet cells coexpressing ARX/MAFB (α cells) and MAFA/MAFB (β cells) exhibited greater expression of key genes related to glucose sensing and hormone secretion relative to subpopulations expressing only one or neither TF. Moreover, all subpopulations were identified in native pancreatic tissue from multiple donors. By Patch-Seq, MAFA/MAFB-coexpressing β cells showed enhanced electrophysiological activity. Thus, these results indicate that combinatorial TF expression in islet α and β cells predicts highly functional, mature subpopulations.
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http://dx.doi.org/10.1172/jci.insight.151621DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8492318PMC
September 2021

From type 1 diabetes biology to therapy: The Human Islet Research Network.

Mol Metab 2021 12 3;54:101283. Epub 2021 Jul 3.

Department of Diabetes and Cancer Discovery Science, Arthur Riggs Diabetes and Metabolism Research Institute, Beckman Research Institute, City of Hope, Duarte, CA, USA.

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http://dx.doi.org/10.1016/j.molmet.2021.101283DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8711046PMC
December 2021

The Human Islet: Mini-Organ With Mega-Impact.

Endocr Rev 2021 Sep;42(5):605-657

Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.

This review focuses on the human pancreatic islet-including its structure, cell composition, development, function, and dysfunction. After providing a historical timeline of key discoveries about human islets over the past century, we describe new research approaches and technologies that are being used to study human islets and how these are providing insight into human islet physiology and pathophysiology. We also describe changes or adaptations in human islets in response to physiologic challenges such as pregnancy, aging, and insulin resistance and discuss islet changes in human diabetes of many forms. We outline current and future interventions being developed to protect, restore, or replace human islets. The review also highlights unresolved questions about human islets and proposes areas where additional research on human islets is needed.
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http://dx.doi.org/10.1210/endrev/bnab010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8476939PMC
September 2021

Coordinated interactions between endothelial cells and macrophages in the islet microenvironment promote β cell regeneration.

NPJ Regen Med 2021 Apr 6;6(1):22. Epub 2021 Apr 6.

Department of Medicine, Division of Diabetes, Endocrinology, and Metabolism, Vanderbilt University Medical Center, Nashville, TN, USA.

Endogenous β cell regeneration could alleviate diabetes, but proliferative stimuli within the islet microenvironment are incompletely understood. We previously found that β cell recovery following hypervascularization-induced β cell loss involves interactions with endothelial cells (ECs) and macrophages (MΦs). Here we show that proliferative ECs modulate MΦ infiltration and phenotype during β cell loss, and recruited MΦs are essential for β cell recovery. Furthermore, VEGFR2 inactivation in quiescent ECs accelerates islet vascular regression during β cell recovery and leads to increased β cell proliferation without changes in MΦ phenotype or number. Transcriptome analysis of β cells, ECs, and MΦs reveals that β cell proliferation coincides with elevated expression of extracellular matrix remodeling molecules and growth factors likely driving activation of proliferative signaling pathways in β cells. Collectively, these findings suggest a new β cell regeneration paradigm whereby coordinated interactions between intra-islet MΦs, ECs, and extracellular matrix mediate β cell self-renewal.
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http://dx.doi.org/10.1038/s41536-021-00129-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8024255PMC
April 2021

Pancreatlas: Applying an Adaptable Framework to Map the Human Pancreas in Health and Disease.

Patterns (N Y) 2020 Nov 5;1(8):100120. Epub 2020 Oct 5.

Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.

Human tissue phenotyping generates complex spatial information from numerous imaging modalities, yet images typically become static figures for publication, and original data and metadata are rarely available. While comprehensive image maps exist for some organs, most resources have limited support for multiplexed imaging or have non-intuitive user interfaces. Therefore, we built a Pancreatlas resource that integrates several technologies into a unique interface, allowing users to access richly annotated web pages, drill down to individual images, and deeply explore data online. The current version of Pancreatlas contains over 800 unique images acquired by whole-slide scanning, confocal microscopy, and imaging mass cytometry, and is available at https://www.pancreatlas.org. To create this human pancreas-specific biological imaging resource, we developed a React-based web application and Python-based application programming interface, collectively called Flexible Framework for Integrating and Navigating Data (FFIND), which can be adapted beyond Pancreatlas to meet countless imaging or other structured data-management needs.
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http://dx.doi.org/10.1016/j.patter.2020.100120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7691395PMC
November 2020

SARS-CoV-2 Cell Entry Factors ACE2 and TMPRSS2 Are Expressed in the Microvasculature and Ducts of Human Pancreas but Are Not Enriched in β Cells.

Cell Metab 2020 12 13;32(6):1028-1040.e4. Epub 2020 Nov 13.

Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA; VA Tennessee Valley Healthcare System, Nashville, TN 37212, USA; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA. Electronic address:

Isolated reports of new-onset diabetes in individuals with COVID-19 have led to the hypothesis that SARS-CoV-2 is directly cytotoxic to pancreatic islet β cells. This would require binding and entry of SARS-CoV-2 into β cells via co-expression of its canonical cell entry factors, angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2); however, their expression in human pancreas has not been clearly defined. We analyzed six transcriptional datasets of primary human islet cells and found that ACE2 and TMPRSS2 were not co-expressed in single β cells. In pancreatic sections, ACE2 and TMPRSS2 protein was not detected in β cells from donors with and without diabetes. Instead, ACE2 protein was expressed in islet and exocrine tissue microvasculature and in a subset of pancreatic ducts, whereas TMPRSS2 protein was restricted to ductal cells. These findings reduce the likelihood that SARS-CoV-2 directly infects β cells in vivo through ACE2 and TMPRSS2.
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http://dx.doi.org/10.1016/j.cmet.2020.11.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664344PMC
December 2020

SARS-CoV-2 Cell Entry Factors ACE2 and TMPRSS2 are Expressed in the Pancreas but are Not Enriched in Islet Endocrine Cells.

bioRxiv 2020 Oct 20. Epub 2020 Oct 20.

Reports of new-onset diabetes and diabetic ketoacidosis in individuals with COVID-19 have led to the hypothesis that SARS-CoV-2, the virus that causes COVID-19, is directly cytotoxic to pancreatic islet β cells. This would require binding and entry of SARS-CoV-2 into host β cells via cell surface co-expression of ACE2 and TMPRSS2, the putative receptor and effector protease, respectively. To define ACE2 and TMPRSS2 expression in the human pancreas, we examined six transcriptional datasets from primary human islet cells and assessed protein expression by immunofluorescence in pancreata from donors with and without diabetes. and transcripts were low or undetectable in pancreatic islet endocrine cells as determined by bulk or single cell RNA sequencing, and neither protein was detected in α or β cells from these donors. Instead, ACE2 protein was expressed in the islet and exocrine tissue microvasculature and also found in a subset of pancreatic ducts, whereas TMPRSS2 protein was restricted to ductal cells. The absence of significant ACE2 and TMPRSS2 co-expression in islet endocrine cells reduces the likelihood that SARS-CoV-2 directly infects pancreatic islet β cells through these cell entry proteins.
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http://dx.doi.org/10.1101/2020.08.31.275719DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7587777PMC
October 2020

Decreased pancreatic acinar cell number in type 1 diabetes.

Diabetologia 2020 07 9;63(7):1418-1423. Epub 2020 May 9.

Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, 7465 Medical Research Bldg IV, 2215 Garland Avenue, Nashville, TN, 37232-0475, USA.

Aims/hypothesis: Individuals with longstanding and recent-onset type 1 diabetes have a smaller pancreas. Since beta cells represent a very small portion of the pancreas, the loss of pancreas volume in diabetes is primarily due to the loss of pancreatic exocrine mass. However, the structural changes in the exocrine pancreas in diabetes are not well understood.

Methods: To characterise the pancreatic endocrine and exocrine compartments in diabetes, we studied pancreases from adult donors with type 1 diabetes compared with similarly aged donors without diabetes. Islet cell mass, islet morphometry, exocrine mass, acinar cell size and number and pancreas fibrosis were assessed by immunohistochemical staining. To better understand possible mechanisms of altered pancreas size, we measured pancreas size in three mouse models of insulin deficiency.

Results: Pancreases from donors with type 1 diabetes were approximately 45% smaller than those from donors without diabetes (47.4 ± 2.6 vs 85.7 ± 3.7 g), independent of diabetes duration or age of onset. Diabetic donor pancreases had decreased beta cell mass (0.061 ± 0.025 vs 0.94 ± 0.21 g) and reduced total exocrine mass (42.0 ± 4.9 vs 96.1 ± 6.5 g). Diabetic acinar cells were similar in size but fewer in number compared with those in pancreases from non-diabetic donors (63.7 ± 8.1 × 10 vs 121.6 ± 12.2 × 10 cells/pancreas), likely accounting for the difference in pancreas size. Within the type 1 diabetes exocrine tissue, there was a greater degree of fibrosis. The pancreases in three mouse models of insulin deficiency were similar in size to those in control mice.

Conclusions/interpretation: Pancreases from donors with type 1 diabetes are smaller than normal donor pancreases because exocrine cells are fewer in number rather than smaller in size; these changes occur early in the disease process. Our mouse data suggest that decreased pancreas size in type 1 diabetes is not directly caused by insulin deficiency, but the precise mechanism responsible remains unclear.
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http://dx.doi.org/10.1007/s00125-020-05155-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8403487PMC
July 2020

Integrated human pseudoislet system and microfluidic platform demonstrate differences in GPCR signaling in islet cells.

JCI Insight 2020 05 21;5(10). Epub 2020 May 21.

Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA.

Pancreatic islets secrete insulin from β cells and glucagon from α cells, and dysregulated secretion of these hormones is a central component of diabetes. Thus, an improved understanding of the pathways governing coordinated β and α cell hormone secretion will provide insight into islet dysfunction in diabetes. However, the 3D multicellular islet architecture, essential for coordinated islet function, presents experimental challenges for mechanistic studies of intracellular signaling pathways in primary islet cells. Here, we developed an integrated approach to study the function of primary human islet cells using genetically modified pseudoislets that resemble native islets across multiple parameters. Further, we developed a microperifusion system that allowed synchronous acquisition of GCaMP6f biosensor signal and hormone secretory profiles. We demonstrate the utility of this experimental approach by studying the effects of Gi and Gq GPCR pathways on insulin and glucagon secretion by expressing the designer receptors exclusively activated by designer drugs (DREADDs) hM4Di or hM3Dq. Activation of Gi signaling reduced insulin and glucagon secretion, while activation of Gq signaling stimulated glucagon secretion but had both stimulatory and inhibitory effects on insulin secretion, which occur through changes in intracellular Ca2+. The experimental approach of combining pseudoislets with a microfluidic system allowed the coregistration of intracellular signaling dynamics and hormone secretion and demonstrated differences in GPCR signaling pathways between human β and α cells.
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http://dx.doi.org/10.1172/jci.insight.137017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7259531PMC
May 2020

Serotonin Regulates Adult β-Cell Mass by Stimulating Perinatal β-Cell Proliferation.

Diabetes 2020 02 5;69(2):205-214. Epub 2019 Dec 5.

Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea

A sufficient β-cell mass is crucial for preventing diabetes, and perinatal β-cell proliferation is important in determining the adult β-cell mass. However, it is not yet known how perinatal β-cell proliferation is regulated. Here, we report that serotonin regulates β-cell proliferation through serotonin receptor 2B (HTR2B) in an autocrine/paracrine manner during the perinatal period. In β-cell-specific knockout ( βKO) mice, perinatal β-cell proliferation was reduced along with the loss of serotonin production in β-cells. Adult βKO mice exhibited glucose intolerance with decreased β-cell mass. Disruption of in β-cells also resulted in decreased perinatal β-cell proliferation and glucose intolerance in adulthood. Growth hormone (GH) was found to induce serotonin production in β-cells through activation of STAT5 during the perinatal period. Thus, our results indicate that GH-GH receptor-STAT5-serotonin-HTR2B signaling plays a critical role in determining the β-cell mass by regulating perinatal β-cell proliferation, and defects in this pathway affect metabolic phenotypes in adults.
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http://dx.doi.org/10.2337/db19-0546DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6971487PMC
February 2020

Human islets expressing HNF1A variant have defective β cell transcriptional regulatory networks.

J Clin Invest 2019 01 3;129(1):246-251. Epub 2018 Dec 3.

Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA.

Using an integrated approach to characterize the pancreatic tissue and isolated islets from a 33-year-old with 17 years of type 1 diabetes (T1D), we found that donor islets contained β cells without insulitis and lacked glucose-stimulated insulin secretion despite a normal insulin response to cAMP-evoked stimulation. With these unexpected findings for T1D, we sequenced the donor DNA and found a pathogenic heterozygous variant in the gene encoding hepatocyte nuclear factor-1α (HNF1A). In one of the first studies of human pancreatic islets with a disease-causing HNF1A variant associated with the most common form of monogenic diabetes, we found that HNF1A dysfunction leads to insulin-insufficient diabetes reminiscent of T1D by impacting the regulatory processes critical for glucose-stimulated insulin secretion and suggest a rationale for a therapeutic alternative to current treatment.
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http://dx.doi.org/10.1172/JCI121994DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6307934PMC
January 2019

Ectonucleoside Triphosphate Diphosphohydrolase-3 Antibody Targets Adult Human Pancreatic β Cells for In Vitro and In Vivo Analysis.

Cell Metab 2019 03 15;29(3):745-754.e4. Epub 2018 Nov 15.

Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37240, USA; Department of Medicine, Division of Diabetes, Endocrinology, and Metabolism, Vanderbilt University Medical Center, Nashville, TN 37232, USA; VA Tennessee Valley Healthcare, Nashville, TN 37212, USA. Electronic address:

Identification of cell-surface markers specific to human pancreatic β cells would allow in vivo analysis and imaging. Here we introduce a biomarker, ectonucleoside triphosphate diphosphohydrolase-3 (NTPDase3), that is expressed on the cell surface of essentially all adult human β cells, including those from individuals with type 1 or type 2 diabetes. NTPDase3 is expressed dynamically during postnatal human pancreas development, appearing first in acinar cells at birth, but several months later its expression declines in acinar cells while concurrently emerging in islet β cells. Given its specificity and membrane localization, we utilized an NTPDase3 antibody for purification of live human β cells as confirmed by transcriptional profiling, and, in addition, for in vivo imaging of transplanted human β cells. Thus, NTPDase3 is a cell-surface biomarker of adult human β cells, and the antibody directed to this protein should be a useful new reagent for β cell sorting, in vivo imaging, and targeting.
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http://dx.doi.org/10.1016/j.cmet.2018.10.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6402969PMC
March 2019

S-nitrosothiol signaling regulates liver development and improves outcome following toxic liver injury.

Cell Rep 2014 Jan 2;6(1):56-69. Epub 2014 Jan 2.

Genetics Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA; Harvard Stem Cell Institute, Cambridge, MA 02138, USA; Gastroenterology Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA; Gastrointestinal Cancer Center, Dana-Farber Cancer Institute, Boston, MA 02115, USA; Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA. Electronic address:

Toxic liver injury is a leading cause of liver failure and death because of the organ's inability to regenerate amidst massive cell death, and few therapeutic options exist. The mechanisms coordinating damage protection and repair are poorly understood. Here, we show that S-nitrosothiols regulate liver growth during development and after injury in vivo; in zebrafish, nitric-oxide (NO) enhanced liver formation independently of cGMP-mediated vasoactive effects. After acetaminophen (APAP) exposure, inhibition of the enzymatic regulator S-nitrosoglutathione reductase (GSNOR) minimized toxic liver damage, increased cell proliferation, and improved survival through sustained activation of the cytoprotective Nrf2 pathway. Preclinical studies of APAP injury in GSNOR-deficient mice confirmed conservation of hepatoprotective properties of S-nitrosothiol signaling across vertebrates; a GSNOR-specific inhibitor improved liver histology and acted with the approved therapy N-acetylcysteine to expand the therapeutic time window and improve outcome. These studies demonstrate that GSNOR inhibitors will be beneficial therapeutic candidates for treating liver injury.
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http://dx.doi.org/10.1016/j.celrep.2013.12.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4008725PMC
January 2014
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