Epithelial cell proliferation and islet neogenesis in IFN-g transgenic mice

The effect of intrauterine growth restriction on the developing pancreatic immune system

Immune cells in the pancreas are known to participate in organ development. However, the resident pancreatic immune system has yet to be fully defined. Immune cells also play a role in pathology and are implicated in diseases such as diabetes induced by intrauterine growth restriction (IUGR). We hypothesized that the resident immune system is established during neonatal development and disrupted by IUGR. Using single cell RNAseq and flow cytometry we identified many immune cell populations in the near-term fetus (at embryologic day 22) and neonatal (postnatal day 1, 7, &14) islets, non-endocrine pancreas, and the spleen in the rat. Using flow cytometry, we observed the resident immune system is established during neonatal development in the pancreas and spleen. We identified 9 distinct immune populations in the pancreatic islets and 8 distinct immune populations in the spleen by single cell RNAseq. There were no sex-specific differences in the relative proportion of immune cells in the pancreas or spleen. Finally, we tested if IUGR disrupted the neonatal immune system using bilateral uterine artery ligation. We found significant changes to the percentage of CD11B+ HIS48- and CD8+ T cells in the islets and non-endocrine pancreas and in the spleen. IUGR-induced alterations were influenced by the tissue environment and the sex of the offspring. Future research to define the role of these immune cells in pancreatic development may identify disrupted pathways that contribute to the development of diabetes following IUGR.

Bone marrow stem cell-derived β-cells: New issue for diabetes cell therapy

This investigation aimed to establish the promising role of insulin-producing cells (IPCs) growing from bone marrow-mesenchymal stem cells (BM-MSCs) in relieving hyperglycemia induced in rats. BM-MSCs were differentiated into IPCs using three different protocols. The efficiency of BM-MSCs differentiation into IPCs in vitro was confirmed by detecting IPCs specific gene expression (Foxa-2, PDX-1 and Ngn-3) and insulin release assay. The in vivo study design included 3 groups of male Wistar rats; negative control group, diabetic group and IPCs-transfused group (5 ×106 cells of the most functional IPCs/rat). One month after IPCs infusion, serum glucose, insulin, c-peptide and visfatin levels as well as pancreatic glucagon level were quantified. Gene expression analysis of pancreatic Foxa-2 and Sox-17, IGF-1 and FGF-10 was done. Additionally, histological investigation of pancreatic tissue sections was performed. Our data clarified that, the most functional IPCs are those generated from BM-MSCs using differentiation protocol 3 as indicated by the significant up-regulation of Foxa-2, PDX-1 and Ngn-3 gene expression levels. These findings were further emphasized by releasing of a significant amount of insulin in response to glucose load. The transplantation of the IPCs in diabetic rats elicited significant decline in serum glucose, visfatin and pancreatic glucagon levels along with significant rise in serum insulin and c-peptide levels. Moreover, it triggered significant up-regulation in the expression levels of pancreatic Foxa-2, Sox-17, IGF-1 and FGF-10 genes versus the untreated diabetic counterpart. The histopathological examination of pancreatic tissue almost assisted the biochemical and molecular genetic analyses. These results disclose that the cell therapy holds potential to develop a new cure for DM based on the capability of BM-MSCs to generate β-cell phenotype using specific protocol.

Dynamic scRNA-seq of live human pancreatic slices reveals functional endocrine cell neogenesis through an intermediate ducto-acinar stage

Human pancreatic plasticity is implied from multiple single-cell RNA sequencing (scRNA-seq) studies. However, these have been invariably based on static datasets from which fate trajectories can only be inferred using pseudotemporal estimations. Furthermore, the analysis of isolated islets has resulted in a drastic underrepresentation of other cell types, hindering our ability to interrogate exocrine-endocrine interactions. The long-term culture of human pancreatic slices (HPSs) has presented the field with an opportunity to dynamically track tissue plasticity at the single-cell level. Combining datasets from same-donor HPSs at different time points, with or without a known regenerative stimulus (BMP signaling), led to integrated single-cell datasets storing true temporal or treatment-dependent information. This integration revealed population shifts consistent with ductal progenitor activation, blurring of ductal/acinar boundaries, formation of ducto-acinar-endocrine differentiation axes, and detection of transitional insulin-producing cells. This study provides the first longitudinal scRNA-seq analysis of whole human pancreatic tissue, confirming its plasticity in a dynamic fashion.

Molecular signaling in pancreatic ductal metaplasia: emerging biomarkers for detection and intervention of early pancreatic cancer

Pancreatic ductal metaplasia (PDM) is the transformation of potentially various types of cells in the pancreas into ductal or ductal-like cells, which eventually replace the existing differentiated somatic cell type(s). PDM is usually triggered by and manifests its ability to adapt to environmental stimuli and genetic insults. The development of PDM to atypical hyperplasia or dysplasia is an important risk factor for pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDA). Recent studies using genetically engineered mouse models, cell lineage tracing, single-cell sequencing and others have unraveled novel cellular and molecular insights in PDM formation and evolution. Those novel findings help better understand the cellular origins and functional significance of PDM and its regulation at cellular and molecular levels. Given that PDM represents the earliest pathological changes in PDA initiation and development, translational studies are beginning to define PDM-associated cell and molecular biomarkers that can be used to screen and detect early PDA and to enable its effective intervention, thereby truly and significantly reducing the dreadful mortality rate of PDA. This review will describe recent advances in the understanding of PDM biology with a focus on its underlying cellular and molecular mechanisms, and in biomarker discovery with clinical implications for the management of pancreatic regeneration and tumorigenesis.

Debates in Pancreatic Beta Cell Biology: Proliferation Versus Progenitor Differentiation and Transdifferentiation in Restoring β Cell Mass

In all forms of diabetes, β cell mass or function is reduced and therefore the capacity of the pancreatic cells for regeneration or replenishment is a critical need. Diverse lines of research have shown the capacity of endocrine as well as acinar, ductal and centroacinar cells to generate new β cells. Several experimental approaches using injury models, pharmacological or genetic interventions, isolation and in vitro expansion of putative progenitors followed by transplantations or a combination thereof have suggested several pathways for β cell neogenesis or regeneration. The experimental results have also generated controversy related to the limitations and interpretation of the experimental approaches and ultimately their physiological relevance, particularly when considering differences between mouse, the primary animal model, and human. As a result, consensus is lacking regarding the relative importance of islet cell proliferation or progenitor differentiation and transdifferentiation of other pancreatic cell types in generating new β cells. In this review we summarize and evaluate recent experimental approaches and findings related to islet regeneration and address their relevance and potential clinical application in the fight against diabetes.

Cotton rat (Sigmodon hispidus) develops metabolic disorders associated with visceral adipose inflammation and fatty pancreas without obesity

Obesity induces metabolic disorders such as type 2 diabetes, hypertension, and cardiovascular diseases and has become a global health concern. Recent studies imply that fat accumulation in nonadipose tissue correlates with metabolic disorders. However, there are no suitable animal models to evaluate this phenomenon. This study investigated the characteristics of metabolic disorders found in cotton rat (Sigmodon hispidus). Blood biochemical examinations revealed that cotton rats, predominantly males, developed hyperinsulinemia, hyperglycemia, and dyslipidemia when fed a normal diet. The islets increased in size through β-cell hyperplasia, which was associated with serum insulin level in both sexes, strongly indicating insulin resistance. In male cotton rats, oxidative stress was observed in β cells, and macrophage infiltration into the visceral white adipose tissue was reported, both of which were associated with serum insulin level without visceral obesity. In contrast, female cotton rats developed hyperinsulinemia without histopathological changes that were reported in males. Adipocytes were found to be accumulated in the pancreas but not in the liver of both sexes during aging. Pancreatic fat accumulation was associated with the serum insulin level only in females. Taken together, cotton rats developed metabolic disorders associated with visceral fat inflammation in the absence of obesity. In addition, pancreatic ectopic fat may also be related to the early stages of these conditions. Thus, the cotton rat may serve as a novel and useful model for metabolic disorders characterized by visceral adipose inflammation and ectopic fat accumulation in the pancreas without obesity.

Elevated Levels of Alpha Cells Emanating from the Pancreatic Ducts of a Patient with a Low BMI and Chronic Pancreatitis

Chronic pancreatitis (CP) is an inflammatory disease that causes progressive damage to the pancreatic parenchyma with irreversible morphological changes and fibrotic replacement of the gland. The risk factors associated with developing CP have been described as toxic (e.g., alcohol and tobacco); idiopathic (e.g., unknown); genetic, autoimmune, recurrent acute pancreatitis, and obstructive (the TIGAR-O system). Upon histological screening of the pancreata from a cohort of CP patients who had undergone pancreatectomy for the treatment of intractable pain in Leicester, UK, one sample showed a striking change in the morphological balance toward an endocrine phenotype, most notably there was evidence of substantial α cell genesis enveloping entire cross sections of ductal epithelium and the presence of α cells within the ductal lumens. This patient had previously undergone a partial pancreatectomy, had severe sclerosing CP, an exceptionally low body mass index (15.2), and diabetes at the time the pancreas was removed, and although these factors have been shown to induce tissue remodeling, such high levels of α cells was an unusual finding within our series of patients. Due to the fact that α cells have been shown to be the first endocrine cell type that emerges during islet neogenesis, future research profiling the factors that caused such marked α cell genesis may prove useful in the field of islet transplantation.

Neutralization Versus Reinforcement of Proinflammatory Cytokines to Arrest Autoimmunity in Type 1 Diabetes

As physiological pathways of intercellular communication produced by all cells, cytokines are involved in the pathogenesis of inflammatory insulitis as well as pivotal mediators of immune homeostasis. Proinflammatory cytokines including interleukins, interferons, transforming growth factor-β, tumor necrosis factor-α, and nitric oxide promote destructive insulitis in type 1 diabetes through amplification of the autoimmune reaction, direct toxicity to β-cells, and sensitization of islets to apoptosis. The concept that neutralization of cytokines may be of therapeutic benefit has been tested in few clinical studies, which fell short of inducing sustained remission or achieving disease arrest. Therapeutic failure is explained by the redundant activities of individual cytokines and their combinations, which are rather dispensable in the process of destructive insulitis because other cytolytic pathways efficiently compensate their deficiency. Proinflammatory cytokines are less redundant in regulation of the inflammatory reaction, displaying protective effects through restriction of effector cell activity, reinforcement of suppressor cell function, and participation in islet recovery from injury. Our analysis suggests that the role of cytokines in immune homeostasis overrides their contribution to β-cell death and may be used as potent immunomodulatory agents for therapeutic purposes rather than neutralized.

Pancreatic β Cell Regeneration as a Possible Therapy for Diabetes

Diabetes is the result of having inadequate supply of functional insulin-producing β cells. Two possible approaches for replenishing the β cells are: (1) replacement by transplanting cadaveric islets or β cells derived from human embryonic stem cells/induced pluripotent stem cells and (2) induction of endogenous regeneration. This review focuses on endogenous regeneration, which can follow two pathways: enhanced replication of existing β cells and formation of new β cells from cells not expressing insulin, either by conversion from a differentiated cell type (transdifferentiation) or differentiation from progenitors (neogenesis). Exciting progress on both pathways suggest that regeneration may have therapeutic promise.

Phenotypic plasticity in the pancreas: new triggers, new players

The pancreas has a very limited regenerative potential during homeostasis. Despite its quiescent nature, recent in vivo models suggest a certain degree of regeneration and cellular interconversion is possible within the adult pancreas. It has now become evident that cellular plasticity can be observed in essentially all cell types within the pancreas when provided with the right stress stimuli. In this review, we will focus on the latest findings uncovering phenotypic plasticity of different cell types in the pancreas, the molecular mechanisms behind such plasticity and how plasticity associated with pancreatic or non-pancreatic cells could be harnessed in the generation of new insulin-producing beta cells.

Generation of Islet-Like Hormone-Producing Cells In Vitro from Adult Human Pancreas

Transplantation of pancreatic islets can provide long-lasting insulin independence for diabetic patients, but the current islet supply is limited. Here we describe a new in vitro system that utilizes adult human pancreatic islet-enriched fractions to generate hormone-producing cells over 3–4 weeks of culture. By labeling proliferating cells with a retrovirus-expressing green fluorescent protein, we show that in this system hormone-producing cells are generated de novo. These hormone-producing cells aggregate to form islet-like cell clusters. The cell clusters, when tested in vitro, release insulin in response to glucose and other secretagogues. After transplantation into immunodeficient, nondiabetic mice, the islet-like cell clusters survive and release human insulin. We propose that this system will be useful as an experimental tool for investigating mechanisms for generating new islet cells from the postnatal pancreas, and for designing strategies to generate physiologically competent pancreatic islet cells ex vivo.

Smad2/3 Linker Phosphorylation Is a Possible Marker of Pancreatic Stem/Progenitor Cells in the Regenerative Phase of Acute Pancreatitis

OBJECTIVES

The aims of this study are to characterize cell proliferation and differentiation during regeneration after pancreatitis and pancreatic buds during development to evaluate the role of Smad2/3, phosphorylated at the specific linker threonine residues (pSmad2/3L-Thr) in positive cells.

METHODS

Male C57BL/6 mice received hourly intraperitoneal injections of cerulein and were analyzed after induced pancreatitis. Pancreatitis-affected tissue sections and pancreatic buds were immunostained for pSmad2/3L-Thr, with other markers thought to be stem/progenitor markers of the pancreas.

RESULTS

pSmad2/3L-Thr immunostaining-positive cells increased as the pancreatitis progressed. The expression of pSmad2/3L-Thr was seen in acinar cells and ductlike tubular complexes. These results suggest that pSmad2/3L-Thr is expressed during acinar-ductal metaplasia. Immunohistochemical colocalization of pSmad2/3L-Thr with Ki67 was never observed. pSmad2/3L-Thr-positive cells may remain in an undifferentiated state. During the pancreatic development process, pSmad2/3L-Thr was expressed as other markers. pSmad2/3L-Thr develops in duct structure of the undifferentiated cell population in the last part of viviparity that acinar structure is formed clearly.

CONCLUSIONS

pSmad2/3L-Thr expression occurs during acinar-ductal metaplasia after pancreatitis and may represent the contribution of stem cells and/or progenitor cells to the differentiation of the pancreas.

Pancreatic β-cell regeneration: Facultative or dedicated progenitors?

The adult pancreas is only capable of limited regeneration. Unlike highly regenerative tissues such as the skin, intestinal crypts and hematopoietic system, no dedicated adult stem cells or stem cell niche have so far been identified within the adult pancreas. New β cells have been shown to form in the adult pancreas, in response to high physiological demand or experimental β-cell ablation, mostly by replication of existing β cells. The possibility that new β cells are formed from other sources is currently a point of major controversy. Under particular injury conditions, fully differentiated pancreatic duct and acinar cells have been shown to dedifferentiate into a progenitor-like state, however the extent, to which ductal, acinar or other endocrine cells contribute to restoring pancreatic β-cell mass remains to be resolved. In this review we focus on regenerative events in the pancreas with emphasis on the restoration of β-cell mass. We present an overview of regenerative responses noted within the different pancreatic lineages, following injury. We also highlight the intrinsic plasticity of the adult pancreas that allows for inter-conversion of fully differentiated pancreatic lineages through manipulation of few genes or growth factors. Taken together, evidence from a number of studies suggest that differentiated pancreatic lineages could act as facultative progenitor cells, but the extent to which these contribute to β-cell regeneration in vivo is still a matter of contention.

Mechanisms of diabetic autoimmunity: II--Is diabetes a central or peripheral disorder of effector and regulatory cells?

Two competing hypotheses aiming to explain the onset of autoimmune reactions are discussed in the context of genetic and environmental predisposition to type 1 diabetes (T1D). The first hypothesis has evolved along characterization of the mechanisms of self-discrimination and attributes diabetic autoimmunity to escape of reactive T cells from central regulation in the thymus. The second considers frequent occurrence of autoimmune reactions within the immune homunculus, which are adequately suppressed by regulatory T cells originating from the thymus, and occasionally, insufficient suppression results in autoimmunity. Besides thymic dysfunction, deregulation of both effector and suppressor cells can in fact result from homeostatic aberrations at the peripheral level during initial stages of evolution of adaptive immunity. Pathogenic cells sensitized in the islets are efficiently expanded in the target tissue and pancreatic lymph nodes of lymphopenic neonates. In parallel, the same mechanisms of peripheral sensitization contribute to tolerization through education of naïve/effector T cells and expansion of regulatory T cells. Experimental evidence presented for each individual mechanism implies that T1D may result from a primary effector or suppressor immune abnormality. Disturbed self-tolerance leading to T1D may well result from peripheral deregulation of innate and adaptive immunity, with variable contribution of central thymic dysfunction.

Transgenic Expression of a Single Transcription Factor Pdx1 Induces Transdifferentiation of Pancreatic Acinar Cells to Endocrine Cells in Adult Mice

A promising approach to new diabetes therapies is to generate β cells from other differentiated pancreatic cells in vivo. Because the acinar cells represent the most abundant cell type in the pancreas, an attractive possibility is to reprogram acinar cells into β cells. The transcription factor Pdx1 (Pancreas/duodenum homeobox protein 1) is essential for pancreatic development and cell lineage determination. Our objective is to examine whether exogenous expression of Pdx1 in acinar cells of adult mice might induce reprogramming of acinar cells into β cells. We established a transgenic mouse line in which Pdx1 and EGFP (enhanced green fluorescent protein) could be inducibly expressed in the acinar cells. After induction of Pdx1, we followed the acinar cells for their expression of exocrine and endocrine markers using cell-lineage tracing with EGFP. The acinar cell-specific expression of Pdx1 in adult mice reprogrammed the acinar cells as endocrine precursor cells, which migrated into the pancreatic islets and differentiated into insulin-, somatostatin-, or PP (pancreatic polypeptide)-producing endocrine cells, but not into glucagon-producing cells. When the mice undergoing such pancreatic reprogramming were treated with streptozotocin (STZ), the newly generated insulin-producing cells were able to ameliorate STZ-induced diabetes. This paradigm of in vivo reprogramming indicates that acinar cells hold promise as a source for new islet cells in regenerative therapies for diabetes.

Proinflammatory Cytokines Induce Endocrine Differentiation in Pancreatic Ductal Cells via STAT3-Dependent NGN3 Activation

A major goal of diabetes research is to develop strategies that replenish pancreatic insulin-producing beta cells. One emerging strategy is to harness pancreatic plasticity-the ability of pancreatic cells to undergo cellular interconversions-a phenomenon implicated in physiological stress and pancreatic injury. Here, we investigate the effects of inflammatory cytokine stress on the differentiation potential of ductal cells in a human cell line, in mouse ductal cells by pancreatic intraductal injection, and during the progression of autoimmune diabetes in the non-obese diabetic (NOD) mouse model. We find that inflammatory cytokine insults stimulate epithelial-to-mesenchymal transition (EMT) as well as the endocrine program in human pancreatic ductal cells via STAT3-dependent NGN3 activation. Furthermore, we show that inflammatory cytokines activate ductal-to-endocrine cell reprogramming in vivo independent of hyperglycemic stress. Together, our findings provide evidence that inflammatory cytokines direct ductal-to-endocrine cell differentiation, with implications for beta cell regeneration.

Centroacinar cells: At the center of pancreas regeneration

The process of regeneration serves to heal injury by replacing missing cells. Understanding regeneration can help us replace cell populations lost during disease, such as the insulin-producing β cells lost in diabetic patients. Centroacinar cells (CACs) are a specialized ductal pancreatic cell type that act as progenitors to replace β cells in the zebrafish. However, whether CACs contribute to β-cell regeneration in adult mammals remains controversial. Here we review the current understanding of the role of CACs as endocrine progenitors during regeneration in zebrafish and mammals.

FGF1 Mediates Overnutrition-Induced Compensatory β-Cell Differentiation

Increased insulin demand resulting from insulin resistance and/or overnutrition induces a compensatory increase in β-cell mass. The physiological factors responsible for the compensation have not been fully characterized. In zebrafish, overnutrition rapidly induces compensatory β-cell differentiation through triggering the release of a paracrine signal from persistently activated β-cells. We identified Fgf1 signaling as a key component of the overnutrition-induced β-cell differentiation signal in a small molecule screen. Fgf1 was confirmed as the overnutrition-induced β-cell differentiation signal, as inactivation of fgf1 abolished the compensatory β-cell differentiation. Furthermore, expression of human FGF1 solely in β-cells in fgf1(-/-) animals rescued the compensatory response, indicating that β-cells can be the source of FGF1. Additionally, constitutive secretion of FGF1 with an exogenous signal peptide increased β-cell number in the absence of overnutrition. These results demonstrate that fgf1 is necessary and FGF1 expression in β-cells is sufficient for the compensatory β-cell differentiation. We further show that FGF1 is secreted during prolonged activation of cultured mammalian β-cells and that endoplasmic reticulum stress acts upstream of FGF1 release. Thus, the recently discovered antidiabetes function of FGF1 may act partially through increasing β-cell differentiation.

Discrete Element Framework for Modelling Extracellular Matrix, Deformable Cells and Subcellular Components

This paper presents a framework for modelling biological tissues based on discrete particles. Cell components (e.g. cell membranes, cell cytoskeleton, cell nucleus) and extracellular matrix (e.g. collagen) are represented using collections of particles. Simple particle to particle interaction laws are used to simulate and control complex physical interaction types (e.g. cell-cell adhesion via cadherins, integrin basement membrane attachment, cytoskeletal mechanical properties). Particles may be given the capacity to change their properties and behaviours in response to changes in the cellular microenvironment (e.g., in response to cell-cell signalling or mechanical loadings). Each particle is in effect an ‘agent’, meaning that the agent can sense local environmental information and respond according to pre-determined or stochastic events. The behaviour of the proposed framework is exemplified through several biological problems of ongoing interest. These examples illustrate how the modelling framework allows enormous flexibility for representing the mechanical behaviour of different tissues, and we argue this is a more intuitive approach than perhaps offered by traditional continuum methods. Because of this flexibility, we believe the discrete modelling framework provides an avenue for biologists and bioengineers to explore the behaviour of tissue systems in a computational laboratory.

Modelling is an important tool in understanding the behaviour of biological tissues. In this paper we advocate a new modelling framework in which cells and tissues are represented by a collection of particles with associated properties. The particles interact with each other and can change their behaviour in response to changes in their environment. We demonstrate how the propose framework can be used to represent the mechanical behaviour of different tissues with much greater flexibility as compared to traditional continuum based methods.

Cellular stress drives pancreatic plasticity

Controversy has long surrounded research on pancreatic beta cell regeneration. Some groups have used nonphysiological experimental methodologies to build support for the existence of pancreatic progenitor cells within the adult pancreas that constantly replenish the beta cell pool; others argue strongly against this mode of regeneration. Recent research has reinvigorated enthusiasm for the harnessing of pancreatic plasticity for therapeutic application--for example, the transdifferentiation of human pancreatic exocrine cells into insulin-secreting beta-like cells in vitro; the conversion of mouse pancreatic acinar cells to beta-like cells in vivo via cytokine treatment; and the potential redifferentiation of dedifferentiated mouse beta cells in vivo. Here, we highlight key findings in this provocative field and provide a perspective on possible exploitation of human pancreatic plasticity for therapeutic beta cell regeneration.

Development of the endocrine pancreas and novel strategies for β-cell mass restoration and diabetes therapy

Diabetes mellitus represents a serious public health problem owing to its global prevalence in the last decade. The causes of this metabolic disease include dysfunction and/or insufficient number of β cells. Existing diabetes mellitus treatments do not reverse or control the disease. Therefore, β-cell mass restoration might be a promising treatment. Several restoration approaches have been developed: inducing the proliferation of remaining insulin-producing cells, de novo islet formation from pancreatic progenitor cells (neogenesis), and converting non-β cells within the pancreas to β cells (transdifferentiation) are the most direct, simple, and least invasive ways to increase β-cell mass. However, their clinical significance is yet to be determined. Hypothetically, β cells or islet transplantation methods might be curative strategies for diabetes mellitus; however, the scarcity of donors limits the clinical application of these approaches. Thus, alternative cell sources for β-cell replacement could include embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells. However, most differentiated cells obtained using these techniques are functionally immature and show poor glucose-stimulated insulin secretion compared with native β cells. Currently, their clinical use is still hampered by ethical issues and the risk of tumor development post transplantation. In this review, we briefly summarize the current knowledge of mouse pancreas organogenesis, morphogenesis, and maturation, including the molecular mechanisms involved. We then discuss two possible approaches of β-cell mass restoration for diabetes mellitus therapy: β-cell regeneration and β-cell replacement. We critically analyze each strategy with respect to the accessibility of the cells, potential risk to patients, and possible clinical outcomes.

Implications of ghrelin and hexarelin in diabetes and diabetes-associated heart diseases

Ghrelin and its synthetic analog hexarelin are specific ligands of growth hormone secretagogue (GHS) receptor. GHS have strong growth hormone-releasing effect and other neuroendocrine activities such as stimulatory effects on prolactin and adrenocorticotropic hormone secretion. Recently, several studies have reported other beneficial functions of GHS that are independent of GH. Ghrelin and hexarelin, for examples, have been shown to exert GH-independent cardiovascular activity. Hexarelin has been reported to regulate peroxisome proliferator-activated receptor gamma (PPAR-γ) in macrophages and adipocytes. PPAR-γ is an important regulator of adipogenesis, lipid metabolism, and insulin sensitization. Ghrelin also shows protective effects on beta cells against lipotoxicity through activation of phosphatidylinositol-3 kinase/protein kinase B, c-Jun N-terminal kinase (JNK) inhibition, and nuclear exclusion of forkhead box protein O1. Acylated ghrelin (AG) and unacylated ghrelin (UAG) administration reduces glucose levels and increases insulin-producing beta cell number, and insulin secretion in pancreatectomized rats and in newborn rats treated with streptozotocin, suggesting a possible role of GHS in pancreatic regeneration. Therefore, the discovery of GHS has opened many new perspectives in endocrine, metabolic, and cardiovascular research areas, suggesting the possible therapeutic application in diabetes and diabetic complications especially diabetic cardiomyopathy. Here, we review the physiological roles of ghrelin and hexarelin in the protection and regeneration of beta cells and their roles in the regulation of insulin release, glucose, and fat metabolism and present their potential therapeutic effects in the treatment of diabetes and diabetic-associated heart diseases.

Aberrant innate immune activation following tissue injury impairs pancreatic regeneration

Normal tissue architecture is disrupted following injury, as resident tissue cells become damaged and immune cells are recruited to the site of injury. While injury and inflammation are critical to tissue remodeling, the inability to resolve this response can lead to the destructive complications of chronic inflammation. In the pancreas, acinar cells of the exocrine compartment respond to injury by transiently adopting characteristics of progenitor cells present during embryonic development. This process of de-differentiation creates a window where a mature and stable cell gains flexibility and is potentially permissive to changes in cellular fate. How de-differentiation can turn an acinar cell into another cell type (such as a pancreatic β-cell), or a cell with cancerous potential (as in cases of deregulated Kras activity) is of interest to both the regenerative medicine and cancer communities. While it is known that inflammation and acinar de-differentiation increase following pancreatic injury, it remains unclear which immune cells are involved in this process. We used a combination of genetically modified mice, immunological blockade and cellular characterization to identify the immune cells that impact pancreatic regeneration in an in vivo model of pancreatitis. We identified the innate inflammatory response of macrophages and neutrophils as regulators of pancreatic regeneration. Under normal conditions, mild innate inflammation prompts a transient de-differentiation of acinar cells that readily dissipates to allow normal regeneration. However, non-resolving inflammation developed when elevated pancreatic levels of neutrophils producing interferon-γ increased iNOS levels and the pro-inflammatory response of macrophages. Pancreatic injury improved following in vivo macrophage depletion, iNOS inhibition as well as suppression of iNOS levels in macrophages via interferon-γ blockade, supporting the impairment in regeneration and the development of chronic inflammation arises from aberrant activation of the innate inflammatory response. Collectively these studies identify targetable inflammatory factors that can be used to influence the development of non-resolving inflammation and pancreatic regeneration following injury.

Current status of regeneration of pancreatic β-cells

Newly generated insulin‐secreting cells for use in cell therapy for insulin‐deficient diabetes mellitus require properties similar to those of native pancreatic β‐cells. Pancreatic β‐cells are highly specialized cells that produce a large amount of insulin, and secrete insulin in a regulated manner in response to glucose and other stimuli. It is not yet explained how the β‐cells acquire this complex function during normal differentiation. So far, in vitro generation of insulin‐secreting cells from embryonic stem cells, induced‐pluripotent stem cells and adult stem/progenitor‐like cells has been reported. However, most of these cells are functionally immature and show poor glucose‐responsive insulin secretion compared to that of native pancreatic β‐cells (or islets). Strategies to generate functional β‐cells or a whole organ in vivo have also recently been proposed. Establishing a protocol to generate fully functional insulin‐secreting cells that closely resemble native β‐cells is a critical matter in regenerative medicine for diabetes. Understanding the physiological processes of differentiation, proliferation and regeneration of pancreatic β‐cells might open the path to cell therapy to cure patients with absolute insulin deficiency.

Macrophage/epithelium cross-talk regulates cell cycle progression and migration in pancreatic progenitors

Macrophages populate the mesenchymal compartment of all organs during embryogenesis and have been shown to support tissue organogenesis and regeneration by regulating remodeling of the extracellular microenvironment. Whether this mesenchymal component can also dictate select developmental decisions in epithelia is unknown. Here, using the embryonic pancreatic epithelium as model system, we show that macrophages drive the epithelium to execute two developmentally important choices, i.e. the exit from cell cycle and the acquisition of a migratory phenotype. We demonstrate that these developmental decisions are effectively imparted by macrophages activated toward an M2 fetal-like functional state, and involve modulation of the adhesion receptor NCAM and an uncommon "paired-less" isoform of the transcription factor PAX6 in the epithelium. Over-expression of this PAX6 variant in pancreatic epithelia controls both cell motility and cell cycle progression in a gene-dosage dependent fashion. Importantly, induction of these phenotypes in embryonic pancreatic transplants by M2 macrophages in vivo is associated with an increased frequency of endocrine-committed cells emerging from ductal progenitor pools. These results identify M2 macrophages as key effectors capable of coordinating epithelial cell cycle withdrawal and cell migration, two events critical to pancreatic progenitors' delamination and progression toward their differentiated fates.

Vaccination procedures against Coxsackievirus-induced heart disease

Coxsackievirus B3--a member of the picornavirus family--is one of the major causes of virus-induced acute or chronic heart disease. Despite the fact that the molecular structure of this pathogen has been characterized very precisely during the last 10 years, until recently, there was no virus-specific preventive or therapeutic procedure against Coxsackievirus B3-induced human heart disease in clinical use. However, using different murine model systems it has been demonstrated that classic as well as newly developed vaccination procedures are quite successful in preventing Coxsackievirus B3 infections. In particular, the application of an interferon-gamma-expressing recombinant Coxsackievirus variant against Coxsackievirus B3-induced myocarditis has been effective.

PDX1 in ducts is not required for postnatal formation of β-cells but is necessary for their subsequent maturation

Pancreatic duodenal homeobox-1 (Pdx1), a transcription factor required for pancreatic development and maintenance of β-cell function, was assessed for a possible role in postnatal β-cell formation from progenitors in the pancreatic ducts by selectively deleting Pdx1 from the ducts. Carbonic anhydrase II (CAII)(Cre);Pdx1(Fl) mice were euglycemic for the first 2 postnatal weeks but showed moderate hyperglycemia from 3 to 7 weeks of age. By 10 weeks, they had near-normal morning fed glucose levels but showed severely impaired glucose tolerance and insulin secretion. Yet the loss of Pdx1 did not result in decreased islet and β-cell mass at 4 and 10 weeks of age. Within the same pancreas, there was a mixed population of islets, with PDX1 and MAFA protein expression normal in some cells and severely diminished in others. Even at 10 weeks, islets expressed immaturity markers. Thus, we conclude that Pdx1 is not necessary for the postnatal formation of β-cells but is essential for their full maturation to glucose-responsive β-cells.

TNF-like weak inducer of apoptosis (TWEAK) promotes beta cell neogenesis from pancreatic ductal epithelium in adult mice

Aim/Hypothesis

The adult mammalian pancreas has limited ability to regenerate in order to restore adequate insulin production from multipotent progenitors, the identity and function of which remain poorly understood. Here we test whether the TNF family member TWEAK (TNF-like weak inducer of apoptosis) promotes β-cell neogenesis from proliferating pancreatic ductal epithelium in adult mice.

Methods

C57Bl/6J mice were treated with Fc-TWEAK and pancreas harvested at different time points for analysis by histology and immunohistochemistry. For lineage tracing, 4 week old double transgenic mice CAII-CreER^TM: R26R-eYFP were implanted with tamoxifen pellet, injected with Fc-TWEAK or control Ig twice weekly and analyzed at day 18 for TWEAK-induced duct cell progeny by costaining for insulin and YFP. The effect of TWEAK on pancreatic regeneration was determined by pancytokeratin immunostaining of paraffin embedded sections from wildtype and TWEAK receptor (Fn14) deficient mice after Px.

Results

TWEAK stimulates proliferation of ductal epithelial cells through its receptor Fn14, while it has no mitogenic effect on pancreatic α- or β-cells or acinar cells. Importantly, TWEAK induces transient expression of endogenous Ngn3, a master regulator of endocrine cell development, and induces focal ductal structures with characteristics of regeneration foci. In addition, we identify by lineage tracing TWEAK-induced pancreatic β-cells derived from pancreatic duct epithelial cells. Conversely, we show that Fn14 deficiency delays formation of regenerating foci after Px and limits their expansion.

Conclusions/Interpretation

We conclude that TWEAK is a novel factor mediating pancreatic β-cell neogenesis from ductal epithelium in normal adult mice.

Omeprazole and PGC-formulated heparin binding epidermal growth factor normalizes fasting blood glucose and suppresses insulitis in multiple low dose streptozotocin diabetes model

PURPOSE

Our objective was to develop novel nanocarriers (protected graft copolymer, PGC) that improve the stability of heparin binding EGF (HBEGF) and gastrin and then to use PGC-formulated HBEGF (PGC-HBEGF) and Omeprazole (+/- PGC-gastrin) for normalizing fasting blood glucose (FBG) and improving islet function in diabetic mice.

METHODS

HBEGF, PGC-HBEGF, Omeprazole, Omeprazole + PGC-HBEGF, Omeprazole + PGC-gastrin + PGC-HBEGF and epidermal growth factor (EGF) + gastrin were tested in multiple low dose streptozotocin diabetic mice.

RESULTS

Omeprazole + PGC-HBEGF normalized FBG and is better than EGF + gastrin at improving islet function and decreasing insulitis. Groups treated with Omeprazole, Omeprazole + PGC-HBEGF, or EGF + gastrin have significantly improved islet function versus saline control. All animals that received PGC-HBEGF had significantly reduced islet insulitis versus saline control. Non-FBG was lower for Omeprazole + PGC-gastrin + PGC-HBEGF but Omeprazole + PGC-HBEGF alone showed better FBG and glucose tolerance.

CONCLUSIONS

Omeprazole + PGC-HBEGF provides a sustained exposure to both EGFRA and gastrin, improves islet function, and decreases insulitis in multiple low dose streptozotocin diabetic mice. Although HBEGF or EGF elevates non-FBG, it facilitates a reduction of insulitis and, in the presence of Omeprazole, provides normalization of FBG at the end of treatment. The study demonstrates Omeprazole and PGC-HBEGF is a viable treatment for diabetes.

Isolation Efficiency of Mouse Pancreatic Stem Cells Is Age Dependent

Mouse pancreatic stem cells have been isolated from mouse pancreata. This study evaluated the efficacy of isolating mouse pancreatic stem cells using mice of different ages. The pancreata of newborn mice, 8-week-old mice, and 24-week-old mice were harvested and digested by using collagenase. The "duct-like" cells in the digested pancreatic tissue were then inoculated into 96-well plates, cloned by limiting dilution, and cultured in DMEM with 20% FBS. Pancreatic stem cells were isolated from the pancreata of all newborn mice, while cells could only be isolated from 10% of the pancreata of 8-week-old mice and could not be isolated from the pancreata of any 24-week-old mice. These data suggest that young mice may have some pancreatic stem cells and that older mice may only have a few pancreatic stem cells. These data also indicate that it is extremely difficult to isolate pancreatic stem cells from older mice, suggesting that future research focus its efforts on finding methods of isolating pancreatic stem cells from adult mice.

In vivo reprogramming of Sox9+ cells in the liver to insulin-secreting ducts

In embryonic development, the pancreas and liver share developmental history up to the stage of bud formation. Therefore, we postulated that direct reprogramming of liver to pancreatic cells can occur when suitable transcription factors are overexpressed. Using a polycistronic vector we misexpress Pdx1, Ngn3, and MafA in the livers of NOD-SCID mice rendered diabetic by treatment with streptozotocin (STZ). The diabetes is relieved long term. Many ectopic duct-like structures appear that express a variety of β-cell markers, including dense core granules visible by electron microscopy (EM). Use of a vector also expressing GFP shows that the ducts persist long after the viral gene expression has ceased, indicating that this is a true irreversible cell reprogramming event. We have recovered the insulin(+) cells by cell sorting and shown that they display glucose-sensitive insulin secretion. The early formed insulin(+) cells can be seen to coexpress SOX9 and are also labeled in mice lineage labeled for Sox9 expression. SOX9(+) cells are normally found associated with small bile ducts in the periportal region, indicating that the duct-like structures arise from this source. This work confirms that developmentally related cells can be reprogrammed by suitable transcription factors and also suggests a unique therapy for diabetes.

Non-β-cell progenitors of β-cells in pregnant mice

Pregnancy is a normal physiological condition in which the maternal β-cell mass increases rapidly about two-fold to adapt to new metabolic challenges. We have used a lineage tracing of β-cells to analyse the origin of new β-cells during this rapid expansion in pregnancy. Double transgenic mice bearing a tamoxifen-dependent Cre-recombinase construct under the control of a rat insulin promoter, together with a reporter Z/AP gene, were generated. Then, in response to a pulse of tamoxifen before pregnancy, β-cells in these animals were marked irreversibly and heritably with the human placental alkaline phosphatase (HP AP). First, we conclude that the lineage tracing system was highly specific for β-cells. Secondly, we scored the proportion of the β-cells marked with HP AP during a subsequent chase period in pregnant and non-pregnant females. We observed a dilution in this labeling index in pregnant animal pancreata, compared to nonpregnant controls, during a single pregnancy in the chase period. To extend these observations we also analysed the labeling index in pancreata of animals during the second of two pregnancies in the chase period. The combined data revealed statistically-significant dilution during pregnancy, indicating a contribution to new beta cells from a non-β-cell source. Thus for the first time in a normal physiological condition, we have demonstrated not only β-cell duplication, but also the activation of a non-β-cell progenitor population. Further, there was no transdifferentiation of β-cells to other cell types in a two and half month period following labeling, including the period of pregnancy.

The SDF-1α/CXCR4 axis is required for proliferation and maturation of human fetal pancreatic endocrine progenitor cells

The chemokine receptor CXCR4 and ligand SDF-1α are expressed in fetal and adult mouse islets. Neutralization of CXCR4 has previously been shown to diminish ductal cell proliferation and increase apoptosis in the IFNγ transgenic mouse model in which the adult mouse pancreas displays islet regeneration. Here, we demonstrate that CXCR4 and SDF-1α are expressed in the human fetal pancreas and that during early gestation, CXCR4 colocalizes with neurogenin 3 (ngn3), a key transcription factor for endocrine specification in the pancreas. Treatment of islet like clusters (ICCs) derived from human fetal pancreas with SDF-1α resulted in increased proliferation of epithelial cells in ICCs without a concomitant increase in total insulin expression. Exposure of ICCs in vitro to AMD3100, a pharmacological inhibitor of CXCR4, did not alter expression of endocrine hormones insulin and glucagon, or the pancreatic endocrine transcription factors PDX1, Nkx6.1, Ngn3 and PAX4. However, a strong inhibition of β cell genesis was observed when in vitro AMD3100 treatment of ICCs was followed by two weeks of in vivo treatment with AMD3100 after ICC transplantation into mice. Analysis of the grafts for human C-peptide found that inhibition of CXCR4 activity profoundly inhibits islet development. Subsequently, a model pancreatic epithelial cell system (CFPAC-1) was employed to study the signals that regulate proliferation and apoptosis by the SDF-1α/CXCR4 axis. From a selected panel of inhibitors tested, both the PI 3-kinase and MAPK pathways were identified as critical regulators of CFPAC-1 proliferation. SDF-1α stimulated Akt phosphorylation, but failed to increase phosphorylation of Erk above the high basal levels observed. Taken together, these results indicate that SDF-1α/CXCR4 axis plays a critical regulatory role in the genesis of human islets.

Hepatocyte growth factor is constitutively produced by donor-derived bone marrow cells and promotes regeneration of pancreatic beta-cells

Recent studies have demonstrated that the transplantation of bone marrow cells following diabetes induced by streptozotocin can support the recovery of pancreatic b-cell mass and a partial reversal of hyperglycemia. To address this issue, we examined whether the c-Met/hepatocyte growth factor (HGF) signaling pathway was involved in the recovery of b-cell injury after bone marrow transplantation (BMT). In this model, donor-derived bone marrow cells were positive for HGF immunoreactivity in the recipient spleen, liver, lung, and pancreas as well as in the host hepatocytes. Indeed, plasma HGF levels were maintained at a high value.The frequency of c-Met expression and its proliferative activity and differentiative response in the pancreatic ductal cells in the BMT group were greater than those in the PBS-treated group, resulting in an elevated number of endogenous insulin-producing cells. The induction of the c-Met/HGF signaling pathway following BMT promotes pancreatic regeneration in diabetic rats.

β-Cell Generation: Can Rodent Studies Be Translated to Humans?

β-cell replacement by allogeneic islet transplantation is a promising approach for patients with type 1 diabetes, but the shortage of organ donors requires new sources of β cells. Islet regeneration in vivo and generation of β-cells ex vivo followed by transplantation represent attractive therapeutic alternatives to restore the β-cell mass. In this paper, we discuss different postnatal cell types that have been envisaged as potential sources for future β-cell replacement therapy. The ultimate goal being translation to the clinic, a particular attention is given to the discrepancies between findings from studies performed in rodents (both ex vivo on primary cells and in vivo on animal models), when compared with clinical data and studies performed on human cells.

Pancreatic β-cells are generated by neogenesis from non-β-cells after birth

The mass of pancreatic β-cells is maintained throughout lifetime to control blood glucose levels. Although the major mechanism of the maintenance of β-cell mass after birth is thought to be selfreplication of pre-existing β-cells, it is possible that pancreatic β-cells are also generated from non-β-cells. Here, we address this issue by using the inducible Cre/loxP system to trace β-cells. We generated Ins2-CreERT2/R26R-YFP double knock-in mice, in which pancreatic β-cells can be labeled specifically and permanently upon injection of the synthetic estrogen analog tamoxifien, and then traced the β-cells by pulse and chase experiment in several different conditions. When β-cells were labeled in adults under physiological and untreated conditions, the frequency of the labeling (labeling index) was not altered significantly throughout the 12-month experimental period. In addition, the labeling index was not changed after ablation of β-cells by streptozotocin treatment. However, when tamoxifen was injected to pregnant mothers just before they gave birth, the labeling index in the neonates was decreased significantly around weaning, suggesting that β-cells are generated from non-β-cells. These results indicate that various mechanisms are involved in the maintenance of β-cells after birth, and that the present system using knock-in mice is useful for investigation of β-cell fate.

Sox9+ ductal cells are multipotent progenitors throughout development but do not produce new endocrine cells in the normal or injured adult pancreas

One major unresolved question in the field of pancreas biology is whether ductal cells have the ability to generate insulin-producing β-cells. Conclusive examination of this question has been limited by the lack of appropriate tools to efficiently and specifically label ductal cells in vivo. We generated Sox9CreER(T2) mice, which, during adulthood, allow for labeling of an average of 70% of pancreatic ductal cells, including terminal duct/centroacinar cells. Fate-mapping studies of the Sox9(+) domain revealed endocrine and acinar cell neogenesis from Sox9(+) cells throughout embryogenesis. Very small numbers of non-β endocrine cells continue to arise from Sox9(+) cells in early postnatal life, but no endocrine or acinar cell neogenesis from Sox9(+) cells occurs during adulthood. In the adult pancreas, pancreatic injury by partial duct ligation (PDL) has been suggested to induce β-cell regeneration from a transient Ngn3(+) endocrine progenitor cell population. Here, we identify ductal cells as a cell of origin for PDL-induced Ngn3(+) cells, but fail to observe β-cell neogenesis from duct-derived cells. Therefore, although PDL leads to activation of Ngn3 expression in ducts, PDL does not induce appropriate cues to allow for completion of the entire β-cell neogenesis program. In conclusion, although endocrine cells arise from the Sox9(+) ductal domain throughout embryogenesis and the early postnatal period, Sox9(+) ductal cells of the adult pancreas no longer give rise to endocrine cells under both normal conditions and in response to PDL.

β-cell regeneration: the pancreatic intrinsic faculty

Type I diabetes (T1D) patients rely on cumbersome chronic injections of insulin, making the development of alternate durable treatments a priority. The ability of the pancreas to generate new β-cells has been described in experimental diabetes models and, importantly, in infants with T1D. Here we discuss recent advances in identifying the origin of new β-cells after pancreatic injury, with and without inflammation, revealing a surprising degree of cell plasticity in the mature pancreas. In particular, the inducible selective near-total destruction of β-cells in healthy adult mice uncovers the intrinsic capacity of differentiated pancreatic cells to spontaneously reprogram to produce insulin. This opens new therapeutic possibilities because it implies that β-cells can differentiate endogenously, in depleted adults, from heterologous origins.

Implantation of bFGF-treated islet progenitor cells ameliorates streptozotocin-induced diabetes in rats

AIM

To examine whether implantation of islet preparation-derived proliferating islet cells (PIC) could ameliorate diabetes in rats.

METHODS

PIC were expanded from rat islet preparation by supplementation of basic fibroblast growth factor (bFGF) and implanted into rats with streptozotocin (STZ)-induced diabetes through the portal vein. Body weight and blood glucose levels were measured. Serum insulin levels were measured by radioimmunoassay. The presence of insulin-positive cells was determined by hematoxylin and immunohistochemical staining.

RESULTS

Cultured islet cells (CIC) were demonstrated to dedifferentiate in vitro, and the apoptosis ratios reached more than 50% by the 15th day post-isolation. PIC cells treated with bFGF (20 ng/mL) continued growing within 30 days after isolation, and no apoptotic cells were detected. Implantation of PIC into diabetic rats was capable of ameliorating diabetes, in terms of the restoration of euglycemia, weight gain, improved glucose response and elevated serum insulin levels for up to 130 days. Livers derived from PIC-implanted rats were examined for insulin expression and single insulin-positive cells. In addition, most islets of PIC-implanted STZ-induced diabetic rats were intact at 130 days post-transplantation and comparable to those of normal rats.

CONCLUSION

Implantation of bFGF-treated proliferating islet cells is a promising cellular therapeutic approach for diabetes.

Activation of pancreatic-duct-derived progenitor cells during pancreas regeneration in adult rats

The adult pancreas has considerable capacity to regenerate in response to injury. We hypothesized that after partial pancreatectomy (Px) in adult rats, pancreatic-duct cells serve as a source of regeneration by undergoing a reproducible dedifferentiation and redifferentiation. We support this hypothesis by the detection of an early loss of the ductal differentiation marker Hnf6 in the mature ducts, followed by the transient appearance of areas composed of proliferating ductules, called foci of regeneration, which subsequently form new pancreatic lobes. In young foci, ductules express markers of the embryonic pancreatic epithelium - Pdx1, Tcf2 and Sox9 - suggesting that these cells act as progenitors of the regenerating pancreas. The endocrine-lineage-specific transcription factor Neurogenin3, which is found in the developing embryonic pancreas, was transiently detected in the foci. Islets in foci initially resemble embryonic islets in their lack of MafA expression and lower percentage of beta-cells, but with increasing maturation have increasing numbers of MafA(+) insulin(+) cells. Taken together, we provide a mechanism by which adult pancreatic duct cells recapitulate aspects of embryonic pancreas differentiation in response to injury, and contribute to regeneration of the pancreas. This mechanism of regeneration relies mainly on the plasticity of the differentiated cells within the pancreas.

Adult pancreatic acinar cells give rise to ducts but not endocrine cells in response to growth factor signaling

Studies in both humans and rodents have found that insulin(+) cells appear within or near ducts of the adult pancreas, particularly following damage or disease, suggesting that these insulin(+) cells arise de novo from ductal epithelium. We have found that insulin(+) cells are continuous with duct cells in the epithelium that makes up the hyperplastic ducts of both chronic pancreatitis and pancreatic cancer in humans. Therefore, we tested the hypothesis that both hyperplastic ductal cells and their associated insulin(+) cells arise from the same cell of origin. Using a mouse model that develops insulin(+) cell-containing hyperplastic ducts in response to the growth factor TGFalpha, we performed genetic lineage tracing experiments to determine which cells gave rise to both hyperplastic ductal cells and duct-associated insulin(+) cells. We found that hyperplastic ductal cells arose largely from acinar cells that changed their cell fate, or transdifferentiated, into ductal cells. However, insulin(+) cells adjacent to acinar-derived ductal cells arose from pre-existing insulin(+) cells, suggesting that islet endocrine cells can intercalate into hyperplastic ducts as they develop. We conclude that apparent pancreatic plasticity can result both from the ability of acinar cells to change fate and of endocrine cells to reorganize in association with duct structures.

Epithelial progenitor 1, a novel factor associated with epithelial cell growth and differentiation

The growth and renewal of epithelial tissue is a highly orchestrated and tightly regulated process occurring in different tissue types under a variety of circumstances. We have been studying the process of pancreatic regeneration in mice. We have identified a cell surface protein, named EP1, which is expressed on the duct epithelium during pancreatic regeneration. Whereas it is not detected in the pancreas of normal mice, it is found in the intestinal epithelium of normal adult mice, as well as during pancreatic repair following cerulein-induced destruction of the acinar tissue. The distinctive situations in which EP1 is expressed, all of which share in common epithelial cell growth in the gastrointestinal tract, suggest that EP1 is involved in the growth and renewal of epithelial tissues in both the intestine and the pancreas.