Endocrine Cell Types Research Articles

Isolated pancreatic islet yield and quality is inversely related to organ donor age in rats.

Pancreatic islets consist of several endocrine cell types that maintain glucose homeostasis. Type 1 diabetes (T1D) results from autoimmune-mediated destruction of insulin producing beta cells in pancreatic islets. Islet transplantation is a treatment for certain individuals with T1D. Islet transplantation in rodents, as an experimental model of the clinical scenario, requires consistency of islet quantity and quality to obtain reproducible results. In this study, we investigated the yield and function of the isolated islets from rats of different ages. Pancreata were harvested from young (10-20 week-old), intermediate (21-40 week-old) and old (>41 week-old) male rats and islets were isolated using a standard protocol. Islet number, morphometry, viability, function, and metabolism were characterized. Islet yield, normalized to body weight, decreased as a function of increasing donor age. Islets from pancreata from young animals were larger and less fragmented compared to islets from organs from intermediate and older animals. Islet viability following overnight culture was the same for islets derived from young and intermediate aged donors but less for islets from old donors. Glucose-stimulated insulin secretion was decreased in islets from older donors. Islet metabolism following glucose challenge, as measured by oxygen consumption, revealed that islets from old donors were metabolically slower and lagged in response to glucose-stimuli. These data demonstrate that increasing donor age has a negative impact on isolated islet yield and quality.

Random Matrix Analysis of Ca2+ Signals in β-Cell Collectives.

Even within small organs like pancreatic islets, different endocrine cell types and subtypes form a heterogeneous collective to sense the chemical composition of the extracellular solution and compute an adequate hormonal output. Erroneous cellular processing and hormonal output due to challenged heterogeneity result in various disorders with diabetes mellitus as a flagship metabolic disease. Here we attempt to address the aforementioned functional heterogeneity with comparing pairwise cell-cell cross-correlations obtained from simultaneous measurements of cytosolic calcium responses in hundreds of islet cells in an optical plane to statistical properties of correlations predicted by the random matrix theory (RMT). We find that the bulk of the empirical eigenvalue spectrum is almost completely described by RMT prediction, however, the deviating eigenvalues that exist below and above RMT spectral edges suggest that there are local and extended modes driving the correlations. We also show that empirical nearest neighbor spacing of eigenvalues follows universal RMT properties regardless of glucose stimulation, but that number variance displays clear separation from RMT prediction and can differentiate between empirical spectra obtained under non-stimulated and stimulated conditions. We suggest that RMT approach provides a sensitive tool to assess the functional cell heterogeneity and its effects on the spatio-temporal dynamics of a collective of beta cells in pancreatic islets in physiological resting and stimulatory conditions, beyond the current limitations of molecular and cellular biology.

A hydrogel platform for in vitro three dimensional assembly of human stem cell-derived islet cells and endothelial cells

Differentiation of stem cells into functional replacement cells and tissues is a major goal of the regenerative medicine field. However, one limitation has been organization of differentiated cells into multi-cellular, three-dimensional assemblies. The islets of Langerhans contain many endocrine and non-endocrine cell types, such as insulin-producing β cells and endothelial cells. Despite the potential importance of endothelial cells to islet function, facilitating interactions between endothelial cells and islet endocrine cell types already differentiated from human embryonic stem cells has been difficult in vitro. We have developed a strategy of assembling human embryonic stem cell-derived islet cells with endothelial cells into three-dimensional aggregates on a hydrogel. The resulting islet organoids express β cell and other endocrine markers and are functional, capable of undergoing glucose-stimulated insulin secretion. This assembly was not observed on traditional tissue culture plastic and in aggregates generated in suspension culture, highlighting how physical culture conditions greatly influence the interactions among these cell types. These results provide a platform for evaluating the effects of the islet tissue microenvironment on human embryonic stem cell-derived β cells and other islet endocrine cells to develop tissue engineered islets. Statement of SignificanceDifferentiation of insulin-producing cells and tissues from human pluripotent stem cells is being investigated for diabetes cell replacement therapies. Despite successes generating β cells, the cell type responsible for glucose-stimulated insulin secretion within the islets of Langerhans found in the pancreas, successful assembly with other non-endocrine cell types, particularly endothelial cells, has been technically challenging. The present study provides a platform for the assembly of endothelial cells with SC-β and other endocrine cells, producing islet organoids that are functional and express β cell markers, that can be used to study the islet microenvironment and islet tissue engineering.

Single-cell RNA Sequencing and Analysis of Human Pancreatic Islets.

Pancreatic islets comprise of endocrine cells with distinctive hormone expression patterns. The endocrine cells show functional differences in response to normal and pathological conditions. The goal of this protocol is to generate high-quality, large-scale transcriptome data of each endocrine cell type with the use of a droplet-based microfluidic single-cell RNA sequencing technology. Such data can be utilized to build the gene expression profile of each endocrine cell type in normal or specific conditions. The process requires careful handling, accurate measurement, and rigorous quality control. In this protocol, we describe detailed steps for human pancreatic islets dissociation, sequencing, and data analysis. The representative results of about 20,000 human single islet cells demonstrate the successful application of the protocol.

Distribution and co-expression patterns of specific cell markers of enteroendocrine cells in pig gastric epithelium

Although the pig is an accepted model species for human digestive physiology, no previous study of the pig gastric mucosa and gastric enteroendocrine cells has investigated the parallels between pig and human. In this study, we have investigated markers for each of the classes of gastric endocrine cells, gastrin, ghrelin, somatostatin, 5-hydroxytryptamine, histidine decarboxylase, and PYY cells in pig stomach. The lining of the proximal stomach consisted of a collar of stratified squamous epithelium surrounded by gastric cardiac glands in the fundus. This differs considerably from human that has only a narrow band of cardiac glands at its entrance, surrounded by a fundic mucosa consisting of oxyntic glands. However, the linings of the corpus and antrum are similar in pig and human. Likewise, the endocrine cell types are similar and similarly distributed in the two species. As in human, gastrin cells were almost exclusively in the antrum, ghrelin cells were most abundant in the oxyntic mucosa and PYY cells were rare. In the pig, 70% of enterochromaffin-like (ECL) cells in the antrum and 95% in the fundus contained 5-hydroxytryptamine (5-HT), higher proportions than in human. Unlike the enteroendocrine of the small intestine, most gastric enteroendocrine cells (EEC) did not contain colocalised hormones. This is similar to human and other species. We conclude that the pig stomach has substantial similarity to human, except that the pig has a protective lining at its entrance that may reflect the difference between a pig diet with hard abrasive components and the soft foods consumed by humans.

A whole organism small molecule screen identifies novel regulators of pancreatic endocrine development.

An early step in pancreas development is marked by the expression of the transcription factor Pdx1 within the pancreatic endoderm, where it is required for the specification of all endocrine cell types. Subsequently, Pdx1 expression becomes restricted to the β-cell lineage, where it plays a central role in β-cell function. This pivotal role of Pdx1 at various stages of pancreas development makes it an attractive target to enhance pancreatic β-cell differentiation and increase β-cell function. In this study, we used a newly generated zebrafish reporter to screen over 8000 small molecules for modulators of pdx1 expression. We found four hit compounds and validated their efficacy at different stages of pancreas development. Notably, valproic acid treatment increased pancreatic endoderm formation, while inhibition of TGFβ signaling led to α-cell to β-cell transdifferentiation. HC toxin, another HDAC inhibitor, enhances β-cell function in primary mouse and human islets. Thus, using a whole organism screening strategy, this study identified new pdx1 expression modulators that can be used to influence different steps in pancreas and β-cell development.

Comprehensive single cell mRNA profiling reveals a detailed roadmap for pancreatic endocrinogenesis.

Deciphering mechanisms of endocrine cell induction, specification and lineage allocation in vivo will provide valuable insights into how the islets of Langerhans are generated. Currently, it is ill defined how endocrine progenitors segregate into different endocrine subtypes during development. Here, we generated a novel neurogenin 3 (Ngn3)-Venus fusion (NVF) reporter mouse line, that closely mirrors the transient endogenous Ngn3 protein expression. To define an in vivo roadmap of endocrinogenesis, we performed single cell RNA sequencing of 36,351 pancreatic epithelial and NVF+ cells during secondary transition. This allowed Ngn3low endocrine progenitors, Ngn3high endocrine precursors, Fev+ endocrine lineage and hormone+ endocrine subtypes to be distinguished and time-resolved, and molecular programs during the step-wise lineage restriction steps to be delineated. Strikingly, we identified 58 novel signature genes that show the same transient expression dynamics as Ngn3 in the 7260 profiled Ngn3-expressing cells. The differential expression of these genes in endocrine precursors associated with their cell-fate allocation towards distinct endocrine cell types. Thus, the generation of an accurately regulated NVF reporter allowed us to temporally resolve endocrine lineage development to provide a fine-grained single cell molecular profile of endocrinogenesis in vivo.

2148-P: Islet Endocrine Cells Shows a Unique Pattern on Development and Growth of Each Cell Type in Human Subjects

Development and growth of islet endocrine cell volume are assumed to mainly depend on cell proliferation. In addition, the partial contribution of islet neogenesis and chromogranin A positive hormone negative cell (CPHN cell) is recently clarified. Detailed evaluation for the islet cell development and growth, however, is not well explored linking to the change of cell replication, neognesis and CPHN cell for each type of endocrine cells in human specimens. For this purpose, we recruited human autopsied pancreata, aged from 24 weeks old to 19 years old (n=32). Formalin-fixed paraffin embedded sections from pancreatic body were used for immunohistochemistry (IHC) and immunofluorescence (IF) analysis. The subjects were divided into 4 groups, Fetus (F: 24-31 weeks), Infant (I : 0-1 years), Child (C : 2-12 years) and Adolescence (A : 13-19 years). Quintuple-IHC with antibodies for glucagon, insulin, somatostatin, pp and Ki-67 was performed for the measurement of islet cell volume density (V) and replication status. Vαand Vβwere increased with age. Vβin A was more abundant than in F (p<0.01). On the other hand, Vδnegatively correlated with age (r=-0.701, p<0.01) and was more in F than in C and A (p<0.01). Ki-67 positive index for αand δ cells showed the highest in F (p<0.01), whereas that of β cells was the highest in I (p<0.01). Neogenic islet density, evaluated in IHC with an antibody for chromogranin A, showed negative correlation with age (r=-0.608, p<0.01). Double-IF with a cocktail of four kinds of antibodies for islet hormones and for chromogranin A was performed to evaluate VCPHN. CPHN cell was identified in both islets and neogenic islets. VCPHNwas more abundant in neogenic islets of F and I than those of C and A. Our results suggest that each kind of islet cell owns a unique pattern of the cell development and growth. In particular, neogenic islet and CPHN cell may play a role as the source of βcells in the later life. Disclosure S. Osonoi: None. H. Mizukami: None. K. Takahashi: None. K. Kudo: None. S. Yagihashi: None.

2151-P: Quantification of Tissue Structure in Human and Mouse Islets

The pancreatic islet is a complex tissue consisting of multiple endocrine cell types, capillaries, and a peri-islet basement membrane. The 3D organization of cells, blood vessels, and basement membrane (BM), enhances islet function by (1) supporting beta cell electrochemical coupling and synchronization through gap junctions between adjacent cells and (2) providing access to nutrients and integrin-mediated signals for beta cell survival and function through contact with capillaries and BM. Though a quantitative understanding of islet structure is lacking, there is strong evidence linking islet structural changes to diabetes progression. Studies of these changes in islet structure will enhance understanding of diabetes-related losses in islet function and lead to the development of new therapeutics for diabetic and prediabetic patients. Here, we present a novel method for quantitative analysis of islet structure in terms of local cell-cell and cell-BM interactions at endocrine cell plasma membrane surfaces. The number and surface area of individual cell-cell and cell-BM interfaces are measured from high-resolution 3D confocal images of human and mouse islets immunolabeled for endocrine cell markers, epithelial cell plasma membranes, and BM. These measurements quantify both cellular interconnectivity and access to signals supporting beta cell survival and function. We report a baseline quantification of structure for healthy adult human and mouse islets. These data both provide a definitive answer to the ongoing debate regarding the differences in structure between human and mouse islets and set the stage for future quantification of islet structure in diabetes. Disclosure O.A. Creasey: None. D. Elnatan: None. J.B. Sneddon: Advisory Panel; Spouse/Partner; Akouos. Advisory Panel; Self; Encellin. Advisory Panel; Spouse/Partner; Encellin. Consultant; Self; Semma Therapeutics, Inc. Z.J. Gartner: Stock/Shareholder; Self; Provenance, Scribe Biosciences. Funding National Institutes of Health; National Science Foundation Graduate Research Fellowship Program; National Science Foundation; University of California, San Francisco Center for Cellular Construction; University of California, San Francisco Diabetes Research Center

Single Cell Transcriptomic Analysis of Pancreatic β Cell Development and Differentiation from Pluripotent Stem Cells

Single cell genomics is a powerful tool to study cellular heterogeneity and discover novel cell types. Recent studies used single cell RNA sequencing (scRNA-seq) to analyze the transcriptomes of individual pancreatic islet cells. Islets are a complex mixture of endocrine cells and therefore represent an ideal tissue for single cell transcriptomic analysis. Adult human islets consist of five known endocrine cell types (α, β, δ, γ, ε) and multiple less well defined non-endocrine cells. In this review, we discuss the scRNA-seq studies performed on human fetal, adult, diseased and stem cell-derive islets in recent years. Since 2015, ~30,000 adult human islet cells have been analyzed using several scRNA-seq technologies. Studies provide a complete catalogue of all islet cell types (up to 14) and subtypes found throughout human development from fetus to adulthood. Islets from patients with Type 2 diabetes have also been analyzed with scRNA-seq unraveling multiple mechanisms of islet dysfunction. Advances in stem cell differentiation protocols and cell therapy manufacturing are bring stem cell-derived islets (SC-Islets) closer to clinical trials. In 2018, more than 60,000 SC-Islet cells were analyzed using scRNA-seq technologies. Lessons learned include SC-Islet cell populations, lineage trajectories and comparative analyses to adult human islet cell transcriptomes. Studies have also identified and characterized the non-islet, off-target cell populations revealing potential strategies for their elimination.

Development and Characteristics of Pancreatic Epsilon Cells.

Pancreatic endocrine cells expressing the ghrelin gene and producing the ghrelin hormone were first identified in 2002. These cells, named ε cells, were recognized as the fifth type of endocrine cells. Differentiation of ε cells is induced by various transcription factors, including Nk2 homeobox 2, paired box proteins Pax-4 and Pax6, and the aristaless-related homeobox. Ghrelin is generally considered to be a “hunger hormone” that stimulates the appetite and is produced mainly by the stomach. Although the population of ε cells is small in adults, they play important roles in regulating other endocrine cells, especially β cells, by releasing ghrelin. However, the roles of ghrelin in β cells are complex. Ghrelin contributes to increased blood glucose levels by suppressing insulin release from β cells and is also involved in the growth and proliferation of β cells and the prevention of β cell apoptosis. Despite increasing evidence and clarification of the mechanisms of ε cells over the last 20 years, many questions remain to be answered. In this review, we present the current evidence for the participation of ε cells in differentiation and clarify their characteristics by focusing on the roles of ghrelin.

Pancreatic Progenitors and Organoids as a Prerequisite to Model Pancreatic Diseases and Cancer.

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are characterized by their unique capacity to stepwise differentiate towards any particular cell type in an adult organism. Pluripotent stem cells provide a beneficial platform to model hereditary diseases and even cancer development. While the incidence of pancreatic diseases such as diabetes and pancreatitis is increasing, the understanding of the underlying pathogenesis of particular diseases remains limited. Only a few recent publications have contributed to the characterization of human pancreatic development in the fetal stage. Hence, most knowledge of pancreatic specification is based on murine embryology. Optimizing and understanding current in vitro protocols for pancreatic differentiation of ESCs and iPSCs constitutes a prerequisite to generate functional pancreatic cells for better disease modeling and drug discovery. Moreover, human pancreatic organoids derived from pluripotent stem cells, organ-restricted stem cells, and tumor samples provide a powerful technology to model carcinogenesis and hereditary diseases independent of genetically engineered mouse models. Herein, we summarize recent advances in directed differentiation of pancreatic organoids comprising endocrine cell types. Beyond that, we illustrate up-and-coming applications for organoid-based platforms.

Surgery for Gastroenteropancreatic Neuroendocrine Tumor Liver Metastases

AbstractGastroenteropancreatic-neuroendocrine tumors (GEP-NETs) arise from endocrine cell types along the luminal gastrointestinal tract and pancreas. Stage and grade are dominant predictors of outcome. Optimal management of localized, lower-grade GEP-NETs involves surgical resection, which is associated with excellent long-term survival. While high-grade disease is almost always associated with rapid disseminated progression, metastatic, well-differentiated GEP-NETs can progress slowly and are compatible with prolonged survival. Management of patients with an advanced spectrum of lower grade disease can include a range of systemic and local therapies and requires multidisciplinary collaboration. While controversy persists regarding the optimal scope and sequencing of therapy, surgical management can have a substantial impact alone or in combination with other therapies.

Single-cell transcriptomic analysis of pancreatic islets in health and type 2 diabetes

Studies on how pancreatic islets respond under physiological and pathological conditions are obtained mostly based on the analysis of whole-islet transcriptome. However, the measurement from the whole islets quantifies the average behaviour of dominant cell types, thereby making it difficult to understand the cell-type-specific changes. Recently, the advent of single-cell RNA sequencing (scRNA-seq) technique has generated valuable resource on islet biology and type 2 diabetes (T2D). This provides an opportunity to understand the different cell types/states at both the network and individual gene expression levels. Here, we inferred the gene regulatory networks (GRNs) of pancreatic cells from publicly available scRNA-seq data in healthy and T2D using single-cell regulatory network inference and clustering workflow. Clustering of cells based on GRNs identifies endocrine and exocrine cells and multiple stable cell states in each alpha, beta and ductal cells. The phenotypic variations in cell states due to obesity and T2D are indistinguishable. Therefore, the trajectory of cells in pseudotime was constructed based on the cell-type-specific gene expression using Monocle2. The analysis shows that continuous spectrum of cell states exists with phenotypic-dependent branching and donor cell–cell variability in endocrine and exocrine cell types. We characterized the genes that give rise to bifurcation in the trajectory. Our study demonstrates that the network and trajectory inference approaches can be used to better understand the behaviour of pancreatic cells in health and disease.

PACS-1 and adaptor protein-1 mediate ACTH trafficking to the regulated secretory pathway.

The regulated secretory pathway is a specialized form of protein secretion found in endocrine and neuroendocrine cell types. Pro-opiomelanocortin (POMC) is a pro-hormone that utilizes this pathway to be trafficked to dense core secretory granules (DCSGs). Within this organelle, POMC is processed to multiple bioactive hormones that play key roles in cellular physiology. However, the complete set of cellular membrane trafficking proteins that mediate the correct sorting of POMC to DCSGs remain unknown. Here, we report the roles of the phosphofurin acidic cluster sorting protein - 1 (PACS-1) and the clathrin adaptor protein 1 (AP-1) in the targeting of POMC to DCSGs. Upon knockdown of PACS-1 and AP-1, POMC is readily secreted into the extracellular milieu and fails to be targeted to DCSGs.

Gene Signature of the Human Pancreatic ε Cell.

The ghrelin-producing ε cell represents the fifth endocrine cell type in human pancreatic islets. The abundance of ε cells in adult pancreas is extremely low, which has hampered the investigation on the molecular pathways regulating the development and the function of this cell type. In this study, we explored the molecular features defining the function of pancreatic ε cells isolated from adult nondiabetic donors using single-cell RNA sequencing technology. We focus on transcription factors, cell surface receptors, and genes involved in metabolic pathways that contribute to regulation of cellular function. Furthermore, the genes that separate ε cells from the other islet endocrine cell types are presented. This study expands prior knowledge about the genes important for ε cell functioning during development and provides a resource to interrogate the transcriptome of this rare human islet cell type.

Expression pattern of delta-like 1 homolog in developing sympathetic neurons and chromaffin cells

Delta-like 1 homolog (DLK1) is a member of the epidermal growth factor (EGF)-like family and an atypical notch ligand that is widely expressed during early mammalian development with putative functions in the regulation of cell differentiation and proliferation. During later stages of development, DLK1 is downregulated and becomes increasingly restricted to specific cell types, including several types of endocrine cells. DLK1 has been linked to various tumors and associated with tumor stem cell features. Sympathoadrenal precursors are neural crest derived cells that give rise to either sympathetic neurons of the autonomic nervous system or the endocrine chromaffin cells located in the adrenal medulla or extraadrenal positions. As these cells are the putative cellular origin of neuroblastoma, one of the most common malignant tumors in early childhood, their molecular characterization is of high clinical importance. In this study we have examined the precise spatiotemporal expression of DLK1 in developing sympathoadrenal cells. We show that DLK1 mRNA is highly expressed in early sympathetic neuron progenitors and that its expression depends on the presence of Phox2B. DLK1 expression becomes quickly restricted to a small subpopulation of cells in sympathetic ganglia, while virtually all chromaffin cells in the adrenal medulla and the Organ of Zuckerkandl still express high levels of DLK1 at late gestational stages.

Non-secreting pituitary tumours characterised by enhanced expression of YAP/TAZ.

Tumours of the anterior pituitary can manifest from all endocrine cell types but the mechanisms for determining their specification are not known. The Hippo kinase cascade is a crucial signalling pathway regulating growth and cell fate in numerous organs. There is mounting evidence implicating this in tumour formation, where it is emerging as an anti-cancer target. We previously demonstrated activity of the Hippo kinase cascade in the mouse pituitary and nuclear association of its effectors YAP/TAZ with SOX2-expressing pituitary stem cells. Here, we sought to investigate whether these components are expressed in the human pituitary and if they are deregulated in human pituitary tumours. Analysis of pathway components by immunofluorescence reveals pathway activity during normal human pituitary development and in the adult gland. Poorly differentiated pituitary tumours (null-cell adenomas, adamantinomatous craniopharyngiomas (ACPs) and papillary craniopharyngiomas (PCPs)), displayed enhanced expression of pathway effectors YAP/TAZ. In contrast, differentiated adenomas displayed lower or absent levels. Knockdown of the kinase-encoding Lats1 in GH3 rat mammosomatotropinoma cells suppressed Prl and Gh promoter activity following an increase in YAP/TAZ levels. In conclusion, we have demonstrated activity of the Hippo kinase cascade in the human pituitary and association of high YAP/TAZ with repression of the differentiated state both in vitro and in vivo. Characterisation of this pathway in pituitary tumours is of potential prognostic value, opening up putative avenues for treatments.

Endocrine cell type sorting and mature architecture in the islets of Langerhans require expression of Roundabout receptors in \u03b2 cells

Pancreatic islets of Langerhans display characteristic spatial architecture of their endocrine cell types. This architecture is critical for cell-cell communication and coordinated hormone secretion. Islet architecture is disrupted in type-2 diabetes. Moreover, the generation of architecturally correct islets in vitro remains a challenge in regenerative approaches to type-1 diabetes. Although the characteristic islet architecture is well documented, the mechanisms controlling its formation remain obscure. Here, we report that correct endocrine cell type sorting and the formation of mature islet architecture require the expression of Roundabout (Robo) receptors in β cells. Mice with whole-body deletion of Robo1 and conditional deletion of Robo2 either in all endocrine cells or selectively in β cells show complete loss of endocrine cell type sorting, highlighting the importance of β cells as the primary organizer of islet architecture. Conditional deletion of Robo in mature β cells subsequent to islet formation results in a similar phenotype. Finally, we provide evidence to suggest that the loss of islet architecture in Robo KO mice is not due to β cell transdifferentiation, cell death or loss of β cell differentiation or maturation.

No Compensatory Increase in Non-ß Hormone Expressing Cells in the Pancreatic Duct Glands in Type 1 Diabetes

Longstanding type 1 diabetes (T1D) entails a near total loss of β cells secondary to autoimmunity, fibrosis and decreased total organ mass, but accumulating evidence suggests there may be an endogenous attempt to regenerate β cells. Pancreatic duct glands (PDGs) represent a distinct anatomical compartment of the pancreas, forming blind ending outpouchings from the main pancreatic duct and its branches. The PDG is purported to be a potential stem/progenitor cell niche. PDGs respond to inflammation in T1D by becoming activated, evidenced by a high frequency of epithelial cell replication and an increase in progenitor-like cells. Hence, we addressed the hypothesis that in T1D, perturbation of hormone-expressing endocrine cells in the interlobular ducts (ILD) and PDGs exist. Pancreatic sections from 10 T1D (disease duration 8-58 year) and 11 similarly aged control (ND) donors were evaluated for replication and expression of known pancreatic endocrine hormones in ducts and PDG. We confirmed increased duct and PDG replication in T1D (T1D vs. ND— ILD: 4.5 ± 1.8 vs. 0.8 ± 0.2%, p<0.05; PDG: 3.4 ± 1.3 vs. 0.4 ± 0.2%, p<0.05) and reduced frequency of insulin expressing cells (T1D vs. ND— ILD: 0.0 ± 0.0 vs. 0.4 ± 0.1%, p<0.001; PDGs: 0.± 0.07 vs. 2.4 ± 0.8%, p<0.05). No differences were found in the frequency of other known endocrine cell types (T1D vs. ND— ILD: Glucagon: 1.5 ± 0.7 vs. 2.1 ± 0.6%, Somatostatin: 1.2 ± 0.4 vs. 1.6 ± 0.3%, Pancreatic Polypeptide: 0.4 ± 0.2 vs. 1.3 ± 0.3%; PDGs: Glucagon: 0.9 ± 0.9 vs. 1.6 ± 1.0%, Somatostatin: 1.96 ± 0.8 vs. 3.7 ± 1.9%, Pancreatic Polypeptide: 1.7 ± 1.1 vs. 2.1 ± 0.8%; p=ns, all). These data suggest that increased cell replication and the deficiency of insulin expressing cells in the PDG compartment of subjects with T1D are not associated with a corresponding increase in non-insulin hormone-expressing endocrine cells. Furthermore, the consistent observation of increased cell replication in the ducts and PDGs in T1D may implicate regenerative mechanisms towards an exocrine cell fate. Disclosure S.S. Kulkarni: None. M.A. Atkinson: Other Relationship; Self; Patent Issued. A. Butler: None.