Zebrafish pancreas development

An accurate understanding of the molecular events governing pancreas development can have an impact on clinical medicine related to diabetes, obesity and pancreatic cancer, diseases with a high impact in public health. Until 1996, the main animal models in which pancreas formation and differentiation could be studied were mouse and, for some instances related to early development, chicken and Xenopus. Zebrafish has penetrated this field very rapidly offering a new model of investigation; by joining functional genomics, genetics and in vivo whole mount visualization, Danio rerio has allowed large scale and fine multidimensional analysis of gene functions during pancreas formation and differentiation.

The role of glucagon-like peptide 1 in glucose homeostasis and in other aspects of human physiology

This paper reviews the structure, function, and pathophysiology of glucagon-like peptide 1 (GLP-1). It describes the physiology and pathophysiology of the incretin axis, of which GLP-1 is a component, as well as the biosynthesis, secretion, activity, and degradation of this intestinal hormone. Effects of GLP-1 on the endocrine function of the pancreas, cardiovascular system, central nervous system, and on water-electrolyte balance have been also presented.

Transgenic and other experimental models of pancreas and islet damage

To unravel the cellular and molecular mechanisms involved in beta-cell renewal and expansion throughout life, several different experimental models were devised in the past. A number of experimental approaches and transgenic models have been engineered to trigger specifically pancreatic injury and thus explore regeneration. Globally, three main strategies are followed to induce pancreas damage: surgical, chemical and genetic. Some of the most relevant studies regarding these three approaches are briefly summarized in this short overview. Although significant progress has been achieved in recent years, there is much room for improving our understanding of many fundamental processes regulating beta-cell mass maintenance.

Clinical utility of anion gap in deciphering acid-base disorders

The anion gap (AG) measurement is a very useful tool in the evaluation of patients with acid-base disorders. Once metabolic acidosis is identified, AG will provide the important first step in the differential diagnosis of disorders that either increase the AG and those that leave the AG unchanged. Delta gap is the comparison between change (delta) in the AG and the change (delta) in bicarbonate (HCO(3)(-)). Delta ratio, defined as delta AG:delta HCO(3)(-) is usually 1:1 in patients with an uncomplicated high AG acidosis. A value below 1:1 suggests a combined high and normal AG acidosis. A value above 2:1 suggests a combined metabolic alkalosis and a high AG acidosis. Urine AG (unmeasured anions-unmeasured cations) is an indirect estimate of the urine NH(4)(+) excretion. It is typically negative in patients with normal AG metabolic acidosis secondary to diarrhoea. Utilisation of AG calculations helps clinicians in identifying and treating acid-base disorders.

Effects of insulin-like growth factor-1 and donor age on transplantation of porcine neonatal pancreatic cell clusters

Porcine neonatal pancreatic cell clusters (NPCCs) isolated from 1- to 3-day-old pigs cured diabetic nude mice more than 14 weeks after transplantation. To shorten the latent period between transplantation and reversal of hyperglycemia, we investigated the effects of insulin-like growth factor-1 (IGF-1) and NPCCs isolated from 1-month-old pigs after transplantation. Pig pancreata were cut into fragments, collagenase digested, and then cultured. Three hundred and 2000 NPCCs were transplanted under the kidney capsule of nondiabetic and diabetic nude mice, respectively. After transplantation, the graft-bearing kidneys were removed to measure insulin content. NPCCs isolated from 1- to 3-day-old pigs were cultured with or without IGF-1 for 6 days. The stimulation index was not significantly different between the 2 groups at 1, 2, or 4 weeks. Moreover, at 4 weeks after transplantation of 300 NPCCs to nondiabetic nude mice yielded comparable graft insulin content as the recipients of NPCCs precultured with or without IGF-1. Two thousand cultured NPCCs isolated from 1-to 3-day-old pigs or 1-month-old pigs were transplanted into diabetic nude mice. The blood glucose levels of diabetic recipients in both groups decreased at the same rate after transplantation, achieving normoglycemia at 8 weeks. The graft insulin content at 12 weeks was not different between the 2 groups. Our data indicated that isolated NPCCs cultured with IGF-1 showed no beneficial effects on insulin secretion and transplantation; NPCCs isolated from 1-to 3-day-old and 1-month-old pigs displayed similar effects on transplantation.

Identification, sequencing, and cellular localization of hepcidin in guinea pig (Cavia porcellus)

Hepcidin, a cysteine-rich peptide hormone with antimicrobial and iron-regulatory activity, plays a central role in regulating iron metabolism during inflammation, hypoxia, iron deficiency, and iron overload. The aim of this study was to isolate and sequence the guinea pig hepcidin gene and show peptide's tissue distribution to identify the guinea pig as good animal model to study the regulation and function of hepcidin. The guinea pig hepcidin cDNA contains a 252 bp open reading frame encoding for an 83 amino acid protein with eight highly conserved cysteine residues. Phylogenetic analyses showed that guinea pig hepcidin was more related to human and chimpanzee than to rodents like mouse or rat. RT-PCR studies revealed that hepcidin mRNA was most abundant in liver, less ample in pancreas, heart, and kidney and not detectable in lung and biliary system. Western blot analyses showed a distinct immunoreactive band of approximately 8 kDa, consistent with the predicted size of prohepcidin, and revealed that guinea pig hepcidin protein is synthesized predominantly in the liver, and with lower expression in kidney, heart, and pancreas. Immunohistochemical studies showed hepcidin predominantly at the basolateral membrane domain of hepatocytes in periportal regions. In pancreas, hepcidin immunoreactivity was confined to endocrine islets of Langerhans, while hepcidin was seen in tubules, but not in the glomeruli in the kidney. Our data identify guinea pig as a convenient model organism to study the role of hepcidin, given the remarkable sequence similarity and tissue distribution pattern largely identical to human.

The pancreatic beta-cell in the islet and organ community

The endocrine pancreas consists of highly vascularized and innervated endocrine mini-organs--the islets of Langerhans. These contain multiple types of hormone-producing cells, including the insulin-secreting beta-cell. The major task of the fully differentiated beta-cell is the tight regulation of blood glucose levels by secreting insulin into the blood stream. This requires molecular features to measure glucose and produce, process, and release insulin by exocytosis. Now multiple interactions with endocrine and nonendocrine islet cells as well as with other organs have been shown to affect the developing as well as the mature beta-cell. Therefore, failure of any of these interactions can inhibit beta-cell differentiation and glucohomeostasis. Here we review recent reports on intrapancreatic cell-cell interactions as well as signals derived from extrapancreatic organs that affect the pancreatic beta-cell.

Dynamics of beta-cell turnover: evidence for beta-cell turnover and regeneration from sources of beta-cells other than beta-cell replication in the HIP rat

Type 2 diabetes is characterized by hyperglycemia, a deficit in beta-cells, increased beta-cell apoptosis, and islet amyloid derived from islet amyloid polypeptide (IAPP). These characteristics are recapitulated in the human IAPP transgenic (HIP) rat. We developed a mathematical model to quantify beta-cell turnover and applied it to nondiabetic wild type (WT) vs. HIP rats from age 2 days to 10 mo to establish 1) whether beta-cell formation is derived exclusively from beta-cell replication, or whether other sources of beta-cells (OSB) are present, and 2) to what extent, if any, there is attempted beta-cell regeneration in the HIP rat and if this is through beta-cell replication or OSB. We conclude that formation and maintenance of adult beta-cells depends largely ( approximately 80%) on formation of beta-cells independent from beta-cell duplication. Moreover, this source adaptively increases in the HIP rat, implying attempted beta-cell regeneration that substantially slows loss of beta-cell mass.

Body mass index of pancreatic donors: a decisive factor for human islet isolation

Despite improvements in islet isolation techniques, islet transplantation remains unpredictable as a method for reliably rendering human type I diabetic recipients normoglycemic. Advances in immunosuppression to prevent primary nonfunction, to promote engraftment and to prevent rejection should improve success rates. However, factors influencing the isolation process remain incompletely defined. During our experience, the donor's nutritional status as well as other donor characteristics were noted to be associated with islet isolation success. Thus, in this study, we tried to clarify whether the body mass index of the human pancreatic donor affects islet isolation yield and viability. In lean donors we found significantly lower islet yields in comparison with normal and obese donors and a significantly lower islet viability compared to obese donors. Obese donor islets had a significantly higher insulin secretory capacity than lean and normal donor islets. In summary, islet yield and viability were improved selecting pancreata from obese donors associated with a BMI > 24 for islet preparation. We hypothesize that, on the one hand, the increased distribution of fat in pancreata of obese donors possibly can facilitate the release of islets during the collagenase digestion, and, on the other hand, pancreata of obese donors contain more islets than pancreata of lean donors. These data underline the decisive influence of the pancreas donor's body mass index on successful human islet isolation. The body mass index should be noted as a potential predictor of success of islet preparations.

New sources of beta-cells for treating diabetes

The treatment of diabetes by islet transplantation is presently hampered by the shortage of organ donors. The generation of insulin-producing cells is therefore a major objective in the long-term goal of curing diabetes. Alternative sources of pancreatic beta-cells include existing pancreatic cells, embryonic stem cells, and cells from other tissues such as liver. This commentary considers evidence for two new sources of beta-cells: intrahepatic biliary epithelial cells and gall bladder epithelium. These observations raise the possibility that a patient's own cells may be used as a source of insulin-producing cells for cell replacement in diabetes.

Akt and PTEN: beta-cell mass and pancreas plasticity

The capacity of pancreatic beta-cells to adapt to insulin resistance is crucial for glucose homeostasis and is a factor in the development of type 2 diabetes. The insulin receptor substrate (insulin receptor 2/phosphoinositide 3-kinase [PI3K]) pathway plays a crucial part in regulating beta-cell mass and function. The serine-threonine kinase Akt, also known as protein kinase B, is one of the major downstream targets of the PI3K pathway and is negatively regulated by phosphatase and tensin homologue deleted on chromosome 10. This Akt signaling pathway has recently been implicated in cell-cycle progression and survival of pancreatic beta-cells. Understanding the mechanisms that link Akt to modulation of beta-cell mass, function and plasticity will positively affect treatment of human diabetes.

Effect of exopolysaccharides on the hydrolysis of beta-lactoglobulin by Lactobacillus acidophilus CRL 636 in an in vitro gastric/pancreatic system

An analysis of the peptides generated by hydrolysis of BLG by nonproliferating cells of the strain Lactobacillus acidophilus CRL 636 was carried out. The effect of polysaccharides (pectin, and two EPS synthesized by two Streptococcus thermophilus strains, EPS1190 and EPS804) on BLG digestibility using an in vitro gastric/pancreatic system was analyzed. Polysaccharides are commonly used in the dairy industry to improve food texture; these hydrocolloids may interact with proteins, affecting their digestibility. Nonproliferating cells of Lb. acidophilus CRL 636 were able to hydrolyze 52% of BLG. Twenty-six resulting peptides with molecular masses in the range 544-4119 Da were identified by LC-MS/MS. These peptides resulted mostly from the hydrolysis of the more accessible N-terminal part of BLG. Degradation of BLG by pepsin was poor (8%). When BLG was previously hydrolyzed by Lb. acidophilus CRL 636, peptic hydrolysis was of 54.8%, while when pectin and EPS1190 were added, hydrolysis was higher (58.2 and 57.2%, respectively). Peptides crossing 8 kDa dialysis membranes after trypsin/chymotrypsin hydrolysis were analyzed by HPSEC. The produced peptides were smaller when BLG was hydrolyzed previously by the Lb. acidophilus strain. Moreover, in the presence of pectin, the amount of the larger peptide (3.5 kDa) observed in the size exclusion chromatograms was considerably decreased. Our studies showed that prehydrolysis of BLG by Lb. acidophilus CRL 636 had a positive influence on BLG digestibility and that polysaccharides may change the peptide profile yielded by trypsin/chymotrypsin hydrolysis, releasing smaller size peptides, which are known to be less immune-reactive. Moreover, Lb. acidophilus CRL 636 was able to hydrolyze the main epitopes (41-60, 102-124, and 149-162) of BLG, reducing its allergenic content.

Prenatal nicotine exposure and the programming of metabolic and cardiovascular disorders

Presently, a growing interest is focused on the origins of the "Metabolic Syndrome", a cluster of several metabolic disorders linking obesity, dyslipidemia, hypertension and type 2 diabetes mellitus. Clearly, genetic predisposition and deleterious lifestyle, including low physical activity and hypercaloric alimentation, have an influence on the occurrence of the Metabolic Syndrome. However, recent data suggest that the Metabolic Syndrome could also be "programmed" during intrauterine life by diverse insults to the growing foetus. Nicotine is the main stimulant and dependence-forming alkaloid found in tobacco, and despite medical advice, statistics show that 20-30% of female smokers continue the habit during gestation, representing around 10% of all pregnancies. In consequence, nicotine is one of the most universally dangerous chemicals to which developing foetuses are exposed. The present review focuses on recent epidemiological surveys and experimental animal studies that provide evidences indicating that pre- and postnatal nicotine exposure might be a contributing factor for the occurrence of metabolic disorders later in life.

'Now we have to use the skills we have developed in cell physiological studies to attack the most crucial problems in pancreatic pathology': an interview with Ole H. Petersen, Medical Research Council Professor of Physiology, University of Liverpool, UK. [Interview by Martín E Fernández-Zapico]

Dr. Ole Petersen is one of the world's leading physiologists working on signal-transduction mechanisms in pancreatic acinar cells. He discovered local apical Ca(2+) signals as important regulators of acinar secretion. His work has been widely recognized, most importantly by his election as Fellow of The Royal Society in 2000 and more recently last year, when Queen Elizabeth II appointed him Commander of the Order of the British Empire (CBE) for 'Services to Science'. In this interview for Pancreatology, Dr. Petersen shares his life experiences as an innovative investigator of exocrine pancreatic function.

Developmental biology of the pancreas

In this review, I summarize some aspects of murine pancreas development, with particular emphasis on the analysis of the ontogenetic relationships between different pancreatic cell types. Lineage analyses allow the identification of the progenitor cells from which mature cell types arise. The identification and successful in vitro culture of putative pancreatic stem cells is highly relevant for future cell replacement therapies in diabetic patients.

Human fetal pancreatic insulin-producing cells proliferate in vitro

There have been considerable efforts towards understanding the potential of human pancreatic endocrine cells to proliferate and transition into mesenchymal cell populations. Since rodent studies have demonstrated that mouse insulin-producing cells do not proliferate in vitro, a similar possibility has been considered for human islet endocrine cells. Considering the inherent differences in mouse and human pancreatic islets, we decided to assess the potential of human fetal pancreatic insulin-producing cells to proliferate in vitro. We studied the proliferative potential of human fetal pancreatic islet-derived populations from second or third trimester fetal pancreas and characterized the cells that grow out during their expansion. We have used seven different approaches including in situ hybridization and immunostaining, quantitative estimation of multiple gene transcripts in populations as well as in single cells, clonal analysis of islet cells, assessment of heritable marks of active insulin promoter, and thymidine analog-based lineage tracing. Our studies demonstrate that human fetal pancreatic insulin-producing cells proliferate in vitro to generate mesenchymal cell populations. Interestingly, epigenetic modifications that mark open chromatin conformation of insulin promoter regions are retained even after a million fold expansion/proliferation in vitro. These findings demonstrate that hormone-producing cells in pancreatic islets proliferate in vitro and retain epigenetic marks that characterize an active insulin promoter. Such in vitro-derived mesenchymal cells may be of potential use in cell-replacement therapy for diabetes.

Identification and action of N-myc downstream regulated gene 4 A2 in rat pancreas

Pancreatic islets and acinar tissue develop from duct epithelium and share expression of several transcription factors and other molecular markers also involved with the development of neural tissues. We examined rat pancreatic tissue from fetal life until adulthood for the expression of N-myc downstream regulated gene 4 (Ndrg4), a gene shown to be expressed during neuronal cell differentiation. Isolated pancreatic ducts from neonatal rats were maintained in culture and gave rise to clusters of cells expressing nestin (NES) and PDX-1, which subsequently contained immunoreactive glucagon. Using reverse transcription PCR (RT-PCR), we identified mRNA expression and immunoreactive protein presence for NDRG4 in cultured duct-derived cells, and brain of neonatal rats. By PCR cloning of the ductal cell-derived DNA the molecular form of NDRG4 expressed in pancreatic ducts and ARIP rat pancreatic cells was identified as NDRG4A2, and its presence in intact pancreas of fetal and neonatal rats was demonstrated by immunohistochemistry. Incubation of ARIP cells with glucagon-like polypeptide-1 (GLP-1), increased the expression of NDRG4A2 and PDX-1, while decreasing DNA synthesis and promoting the appearance of glucagon-positive cells. This inhibitory effect of GLP-1 on DNA synthesis and the stimulatory effect on endocrine differentiation were reversed when the translation of NDRG4A2 was prevented using siRNA. These findings indicate that NDRG4A2 is expressed in pancreatic duct cells under GLP-1 control and may be related to a reduction in proliferation and the onset of the pancreas cell differentiation.

Differentiation of COPAS-sorted non-endocrine pancreatic cells into insulin-positive cells in the mouse

AIMS/HYPOTHESIS

The regenerative process in the pancreas is of particular interest, since insulin-producing beta cells are lost in diabetes. Differentiation of new beta cells from pancreatic non-endocrine cells has been reported in vivo and in vitro, a finding that implies the existence of pancreatic stem/progenitor cells. However, while tissue-specific stem cells are well documented in skin, intestine and testis, pancreatic stem cells have been elusive. We hypothesised that pancreatic stem/progenitor cells within the non-endocrine fraction could be a source of new islets in vitro.

METHODS

To test if there were such cells within the pancreas, we generated pancreatic cell aggregates from tissue remaining after islet isolation from mouse insulin promoter 1-green fluorescent protein (MIP-GFP) mice. To eliminate any contamination of insulin-positive cells, we deleted all GFP-positive aggregates using COPAS Select and cultured with Matrigel. Immunohistochemistry, quantitative real-time PCR and single-cell nested RT-PCR were performed to confirm formation of insulin-producing cells.

RESULTS

The GFP-negative cells were expanded as monolayers and then differentiated into three-dimensional cystic structures. After 1 week of culture, GFP-positive cells were found as clusters or single cells. By quantitative real-time PCR, no insulin mRNA was detected immediately after COPAS sorting, but after differentiation insulin mRNA of the whole preparation was 1.91 +/- 0.31% that of purified MIP-GFP beta cells. All GFP-positive cells expressed insulin 1; most expressed insulin 2, pancreas duodenum homeobox-1 and cytokeratin 19 by single cell nested RT-PCR.

CONCLUSIONS/INTERPRETATION

Our data support the concept that within the exocrine (acinar and ductal) pancreas of the adult mouse there are cells that can give rise to insulin-positive cells in vitro.

Focus is key to becoming an expert in any field of research. An interview with Prof. Howard A. Reber, chief of gastrointestinal surgery, and director of the Ronald S. Hirshberg Pancreatic Cancer Research Laboratory, University of California Los Angeles (UCLA), Los Angeles, Calif., USA. Interview by Martín E. Fernández-Zapico

Dr. Howard Reber is a world-renowned pancreatologist in the area of basic pancreatic physiology and the management of pancreatic diseases. He was leader in the development of the current recommendation for the treatment of pancreatic cancer. In this interview for Pancreatology, Dr. Reber shares his life experiences as a scientist in pancreatic research. and IAP.

The role of the endocannabinoid system in the regulation of energy expenditure

Endocannabinoids, a lipid-derived signaling system, regulate appetite and motivation to eat via effects in the hypothalamus and nucleus accumbens. Not all the effects of endocannabinoids on fat mass can be explained by the regulation of food intake alone. Endocannabinoids and their receptors are located in areas of the central nervous system and multiple peripheral tissues involved in the regulation of intermediary metabolism and energy expenditure. In addition to regulating food intake by both central and peripherally mediated effects, endocannabinoids modify glucose and lipid metabolism so as to promote energy storage via lipogenesis and reduce energy expenditure. The endocannabinoid system appears to be overactive in obesity and may serve to maintain fat mass and underlies some of the metabolic consequences of obesity. Inhibition of the cannabinoid type-1 receptor ameliorates the effects of endocannabinoids on food intake and energy metabolism; lipogenesis is inhibited, lipolysis, fatty acid oxidation and glucose uptake increase.

[Regulation of pancreatic exosecretion]

The review contains the materials on scientific literature, research results of the author and his colleagues about organization of pancreatic exosecretion activity. Peptidegric regulatory mechanisms and pancreatic exosecretion of the hydrolytic enzymes, their participation in adaptation of the pancreatic enzymatic discharge to the nutrient composition of duodenal chyme are underlined.

Glucokinase, the pancreatic glucose sensor, is not the gut glucose sensor

AIMS/HYPOTHESIS

The incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotrophic peptide (GIP) are released from intestinal endocrine cells in response to luminal glucose. Glucokinase is present in these cells and has been proposed as a glucose sensor. The physiological role of glucokinase can be tested using individuals with heterozygous glucokinase gene (GCK) mutations. If glucokinase is the gut glucose sensor, GLP-1 and GIP secretion during a 75 g OGTT would be lower in GCK mutation carriers compared with controls.

METHODS

We compared GLP-1 and GIP concentrations measured at five time-points during a 75 g OGTT in 49 participants having GCK mutations with those of 28 familial controls. Mathematical modelling of glucose, insulin and C-peptide was used to estimate basal insulin secretion rate (BSR), total insulin secretion (TIS), beta cell glucose sensitivity, potentiation factor and insulin secretion rate (ISR).

RESULTS

GIP and GLP-1 profiles during the OGTT were similar in GCK mutation carriers and controls (p = 0.52 and p = 0.44, respectively). Modelled variables of beta cell function showed a reduction in beta cell glucose sensitivity (87 pmol min(-1) m(-2) [mmol/l](-1) [95% CI 66-108] vs 183 pmol min(-1) m(-2) [mmol/l](-1) [95% CI 155-211], p < 0.001) and potentiation factor (1.5 min [95% CI 1.2-1.8] vs 2.2 min [95% CI 1.8-2.7], p = 0.007) but no change in BSR or TIS. The glucose/ISR curve was right-shifted in GCK mutation carriers.

CONCLUSIONS/INTERPRETATION

Glucokinase, the major pancreatic glucose sensor, is not the main gut glucose sensor. By modelling OGTT data in GCK mutation carriers we were able to distinguish a specific beta cell glucose-sensing defect. Our data suggest a reduction in potentiation of insulin secretion by glucose that is independent of differences in incretin hormone release.

[Functional morphology of aging]

The review provides the analysis of the research results in the field of the study of the mechanisms of aging involution, which are connected with the peculiar properties of the expression of signaling molecules participating in intercellular communications in the different organs and tissues.

Evaluation of the degree of pancreas activity in piglets from sows fed enzymatic stimulating complex

One of the possibilities for estimating pancreas activity is the estimation of zymogene granule content in pancreatic follicular cells. In the present study, the degree of pancreatic activity was measured in piglets from sows receiving enzymatic stimulating complex throughout pregnancy and during the lactation period. The pancreas was collected for ultrastructural examination from 1-day-old and 21-day-old piglets. The enzyme preparation influenced the ultrastructural structure of the piglet pancreas, but the secretory cells in these animals did not confirm a more intensive course of creation and maturation processes. The accumulation of granules in extra-secretory pancreatic cells was observed, with a large volume of these granules and granular crinophagy observed in older piglets. The findings indicate a slow process of granule release, which may be the result of overproduction, lower requirements for enzymes contained in the granules, or both.

The homeodomain-interacting protein kinase 2 regulates insulin promoter factor-1/pancreatic duodenal homeobox-1 transcriptional activity

The homeodomain transcription factor insulin promoter factor (IPF)-1/pancreatic duodenal homeobox (PDX)-1 plays a crucial role in both pancreas development and maintenance of beta-cell function. Targeted disruption of the Ipf1/Pdx1 gene in beta-cells of mice leads to overt diabetes and reduced Ipf1/Pdx1 gene expression results in decreased insulin expression and secretion. In humans, mutations in the IPF1 gene have been linked to diabetes. Hence, the identification of molecular mechanisms regulating the transcriptional activity of this key transcription factor is of great interest. Herein we analyzed homeodomain-interacting protein kinase (Hipk) 2 expression in the embryonic and adult pancreas by in situ hybridization and RT-PCR. Moreover, we functionally characterized the role of HIPK2 in regulating IPF1/PDX1 transcriptional activity by performing transient transfection experiments and RNA interference. We show that Hipk2 is expressed in the developing pancreatic epithelium from embryonic d 12-15 but that the expression becomes preferentially confined to pancreatic endocrine cells at later developmental stages. Moreover, we show that HIPK2 positively influences IPF1/PDX1 transcriptional activity and that the kinase activity of HIPK2 is required for this effect. We also demonstrate that HIPK2 directly phosphorylates the C-terminal portion of IPF1/PDX1. Taken together, our data provide evidence for a new mechanism by which IPF1/PDX1 transcriptional activity, and thus possibly pancreas development and/or beta-cell function, is regulated.

The physiology of rodent beta-cells in pancreas slices

Beta-cells in pancreatic islets form complex syncytia. Sufficient cell-to-cell electrical coupling seems to ensure coordinated depolarization pattern and insulin release that can be further modulated by rich innervation. The complex structure and coordinated action develop after birth during fast proliferation of the endocrine tissue. These emergent properties can be lost due to various reasons later in life and can lead to glucose intolerance and diabetes mellitus. Pancreas slice is a novel method of choice to study the physiology of beta-cells still embedded in their normal cellulo-social context. I present major advantages, list drawbacks and provide an overview on recent advances in our understanding of the physiology of beta-cells using the pancreas slice approach.

Amyloid formation results in recurrence of hyperglycaemia following transplantation of human IAPP transgenic mouse islets

AIMS/HYPOTHESIS

Islet transplantation is a potential cure for diabetes; however, rates of graft failure remain high. The aim of the present study was to determine whether amyloid deposition is associated with reduced beta cell volume in islet grafts and the recurrence of hyperglycaemia following islet transplantation.

METHODS

We transplanted a streptozotocin-induced mouse model of diabetes with 100 islets from human IAPP (which encodes islet amyloid polypeptide) transgenic mice that have the propensity to form islet amyloid (n = 8-12) or from non-transgenic mice that do not develop amyloid (n = 6-10) in sets of studies that lasted 1 or 6 weeks.

RESULTS

Plasma glucose levels before and for 1 week after transplantation were similar in mice that received transgenic or non-transgenic islets, and at that time amyloid was detected in all transgenic grafts and, as expected, in none of the non-transgenic grafts. However, over the 6 weeks following transplantation, plasma glucose levels increased in transgenic but remained stable in non-transgenic islet graft recipients (p < 0.05). At 6 weeks, amyloid was present in 92% of the transgenic grafts and in none of the non-transgenic grafts. Beta cell volume was reduced by 30% (p < 0.05), beta cell apoptosis was twofold higher (p < 0.05), and beta cell replication was reduced by 50% (p < 0.001) in transgenic vs non-transgenic grafts. In summary, amyloid deposition in islet grafts occurs prior to the recurrence of hyperglycaemia and its accumulation over time is associated with beta cell loss.

CONCLUSIONS/INTERPRETATION

Islet amyloid formation may explain, in part, the non-immune loss of beta cells and recurrence of hyperglycaemia following clinical islet transplantation.

'The mentor's quality determines the probability of success of the young researcher'. An interview with Prof. Makoto Otsuki. Interview by Martín E Fernández-Zapico

In this interview, Professor Makoto Otsuki points out the importance of mentorship during young researchers' development. Dr. Otsuki, a Professor and Chair of the Third Department of Internal Medicine at the University of Occupational and Environmental Health, has contributed significantly to the field of pancreatic physiology. In addition, his epidemiological research has been fundamental for understanding the pathogenesis of pancreatitis and establishment of the guidelines for its diagnosis and improvement of case fatality.

Wnt signaling: relevance to beta-cell biology and diabetes

Interest in the importance of Wnt signaling in diabetes has risen after identification of the transcription factor TCF7L2, a component of this pathway, as a strong risk factor for type 2 diabetes. Here, we review emerging new evidence that Wnt signaling influences endocrine pancreas development and modulates mature beta-cell functions including insulin secretion, survival and proliferation. Alterations in Wnt signaling might also impact other metabolic tissues involved in the pathogenesis of diabetes, with TCF7L2 proposed to modulate adipogenesis and regulate GLP-1 production. Together, these studies point towards a role for Wnt signaling in the pathogenesis of type 2 diabetes, highlighting the importance of further investigation of this pathway to develop new therapies for this disease.

Renin inhibition attenuates insulin resistance, oxidative stress, and pancreatic remodeling in the transgenic Ren2 rat

Emerging evidence indicates that pancreatic tissue expresses all components of the renin-angiotensin system. However, the functional role is not well understood. This investigation examined renin inhibition on pancreas structure/function in the transgenic Ren2 rat harboring the mouse renin gene, a model of tissue renin overexpression. Renin is the rate-limiting step in the generation of angiotensin II (Ang II), which stimulates the generation of reactive oxygen species in a variety of tissues. Overexpression of renin in Ren2 rats results in hypertension, insulin resistance, and cardiovascular and renal damage. Young (6-7 wk old) insulin-resistant male Ren2 and age-matched insulin sensitive Sprague Dawley rats were treated with the renin inhibitor, aliskiren (50 mg/kg.d by ip injection), or placebo for 21 d. At 21 d, the Ren2 demonstrated insulin resistance with increased islet insulin, Ang II, and reduced total insulin receptor substrate (IRS)-1, IRS-2, and Akt immunostaining. There was increased islet nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and subunits (p47(phox) and Rac1) as well as increased nitrotyrosine immunostaining (each P < 0.05). These functional abnormalities were associated with a disordered islet architecture; increased islet-exocrine interface, pericapillary fibrosis, and structurally abnormal mitochondria and content in endocrine and exocrine pancreas. In vivo treatment with aliskiren normalized systemic insulin resistance and islet insulin, Ang II, NADPH oxidase activity/subunits, and nitrotyrosine and improved total IRS-1 and Akt phosphorylation (each P < 0.05) as well as islet/exocrine structural abnormalities. Collectively, these data suggest that pancreatic functional/structural changes are driven, in part, by tissue renin-angiotensin system-mediated increases in NADPH oxidase and reactive oxygen species generation, abnormalities attenuated with direct renin inhibition.

Assessment of in vitro differentiation of bovine pancreatic tissue in insulin-expressing cells

CONTEXT

Expansion and culture of beta cell progenitors in vitro may represent an alternative to the use of differentiated beta cells from donor pancreata.

OBJECTIVE

The aim of our study was to investigate to what extent exocrine or endocrine pancreatic cells can be differentiated in insulin-producing cells in vitro.

SETTING

Bovine exocrine tissue (n=4) and islets (n=4) were cultured in DMEM with serum.

INTERVENTIONS

After 7 days, the cells were trypsinized and cultured in the same medium for cell proliferation, or in DMEM/F-12 containing growth factors to induce cell differentiation.

MAIN OUTCOME MEASURE

Proliferating capacity after 4 weeks in culture. In addition, insulin expression was evaluated by RT-PCR and by immunohistochemical staining.

RESULTS

After 4 weeks of culture, cells from exocrine tissue showed a 69.5+/-10.0 fold increase, while cells from islets showed a 31.2+/-11.4 fold increase (P=0.059). In differentiating medium, monolayers from exocrine and islet tissue were organized into islet-like structures containing cells which stained positively for insulin. Morphometrical analysis and RT-PCR confirmed the presence of insulin in the cells at the protein and the mRNA level.

CONCLUSIONS

In our experimental conditions, cells from pancreatic tissue proliferated and differentiated in insulin-containing cells. However, the level of insulin as well as mRNA expression is only a small fraction of that shown by fresh islets. Only selective identification of cell precursors may allow efficient generation of insulin-producing cells in vitro.

Minireview: pancreatic progenitor cells--recent studies

Past studies of pancreatic progenitor cell biology relied mostly on histological analyses. Recent studies, using genetic labeling and tracing of progenitors, direct single cell analyses, colony assays, and enrichment of the minor population of progenitor cells through the use of cell surface markers, have strongly suggested that pancreatic progenitor cells with various frequency and lineage potentials, including the multipotent progenitors that give rise to endocrine, exocrine, and duct cells, exist in the developing and adult pancreas. In this review, it is therefore proposed that pancreatic progenitor cells may be organized in a hierarchy, in which the most primitive pan-pancreatic multipotent progenitors are at the top and rare, and the monopotent progenitors are at the bottom and abundant. This model may explain why only drastic injuries lead to effective activation of the progenitor cell compartment of the higher hierarchy, whereas under steady state, pregnancy, and milder injuries, recruitment of preexisting mature cells or their immediate monopotent progenitors could be sufficient to restore metabolic homeostasis. It is also proposed that the morphologically defined ductal cells are likely to be functionally heterogeneous and that endocrine progenitor cell activity should be determined based on functional analyses rather than histological locations.

Cystic fibrosis: impaired bicarbonate secretion and mucoviscidosis

For more than 20 years, the abnormally thick mucus (mucoviscidosis) in cystic fibrosis has been widely shown to be linked to a genetic defect in the cystic fibrosis transmembrane conductance regulator Cl(-) channel. The defect is widely thought to cause mucus to become dehydrated as a result of basic defects in Cl(-) dependent fluid transport. However, this widely held explanation is inconsistent with the known physiological properties and functions of organs affected by cystic fibrosis. During the process of releasing highly condensed mucins from intracellular granules, Ca(2+) and H(+) cations must be removed to enable the mucins to expand by as much as 1000 times, forming extracellular mucus-gel networks. Over the past few years, that HCO(3)(-) transport is also defective in patients with cystic fibrosis has become apparent. I propose that HCO(3)(-) is crucial to normal mucin expansion because it forms complexes with these cations. Thus, because HCO(3)(-) secretion is defective in cystic fibrosis, mucins in organs affected by cystic fibrosis tend to remain aggregated, poorly solubilised, and less transportable. If the hypothesis is valid, pathogenesis in cystic fibrosis could be due as much to defective transport of HCO(3)(-) as to defective Cl(-) transport.

Interleukin-10 Gene Transfection of Donor Pancreas Grafts Protects against Rejection after Heterotopic Pancreas Transplantation in a Rat Model

OBJECTIVE

The aim of this study was to assess the effect of immunoregulatory cytokine interleukin-10 (IL-10) gene therapy on pancreas tissue rejection in a heterotopic pancreas transplantation model.

BACKGROUND

Modulation of inflammatory responses by anti-inflammatory cytokines (e.g., IL-10) has been suggested to minimize organ rejection. In this context, modulation of cytokines using gene therapy could be a new therapeutic modality in preventing organ rejection.

METHODS

The study was performed using male inbred Wistar rats as recipients and Sprague-Dawley rats as donors. 24 h before transplantation, groups of rats, named IL-10 (n = 20) and green fluorescent protein (GFP, n = 20), were injected with viral vectors Ad5CMVhIL10 or Ad5CMVGFP. Sham-operated rats (n = 20) underwent saline injection only before transplantation. The pancreatic tissue from each of these donor rats was subsequently transplanted into the corresponding groups of streptozotocin-induced diabetic recipient rats. Recipients were thus transfected with either IL-10 (n = 20), GFP-only carrying viral vectors (n = 20) or no viral vectors (normal saline, n = 20). A selected number of animals from each recipient group (n = 5) was sacrificed at weekly intervals for 3 weeks and some were further followed up to 12 weeks before sacrifice. Histological assessment of the pancreatic tissue was made based on rejection and GFP expression. Blood glucose levels were checked daily in all groups until sacrifice. Upon sacrifice, serum cytokine and insulin levels were measured. Histopathological correlations between blood glucose levels, serum insulin levels and serum IL-10 levels were made.

RESULTS

IL-10 gene therapy significantly attenuated pancreas rejection compared to controls, provided more normal blood glucose levels and elevated plasma insulin levels. Upon assumed natural deactivation of transferred viruses after 4 weeks, differences between groups in terms of rejection, blood glucose and insulin levels disappeared.

CONCLUSION

These findings suggest that IL-10 gene therapy significantly reduced pancreas rejection.

Transcription factor expression in the developing human fetal endocrine pancreas

AIMS/HYPOTHESIS

Morphological changes that occur during pancreatic endocrine cell differentiation have been shown in rodent systems to be dependent on sequential alterations in transcription factor expression. However, similar data for humans have been limited. The aim of the present study was to provide a connection between pancreatic morphology, transcription factor gene expression and protein localisation during human fetal development.

METHODS

Human fetal pancreases were examined at early (8-12 weeks of fetal age), middle (14-16 weeks) and late (19-21 weeks) stages, using immunohistological, microarray and qRT-PCR analyses.

RESULTS

We observed a significant decrease in pancreatic duodenal homeobox 1 (PDX-1)(+)/cytokeratin 19(+) cells (p < 0.001), with a simultaneous increase in PDX-1(+)/insulin(+) cells from 8 to 21 weeks (p < 0.05). Increased PDX-1/insulin co-localisation within islet clusters was noted, while no co-expression of PDX-1 with glucagon was found, suggesting that loss of PDX-1 is essential for alpha cell formation. Given that neurogenin 3 (NGN3) expression is critical for establishing the endocrine cell programme in the rodent pancreas, we examined its expression pattern and co-localisation in PDX-1(+), insulin(+) and glucagon(+) cells. Co-localisation of NGN3 with PDX-1, insulin and glucagon was noted during early development, with significant decreases in middle and late stages (p < 0.001). Our microarray and co-localisation analyses of transcription factors linked to NGN3 demonstrated that ISL1 transcription factor (ISL1), neurogenic differentiation 1 (NEUROD1), NK2 related transcription factor related, locus 2 (NKX2-2) and paired box gene 6 (PAX6) were upregulated during development and present in all four endocrine cell types, while NK6 related transcription factor related, locus 1 (NKX6-1) was expressed exclusively in beta cells.

CONCLUSIONS/INTERPRETATION

This study is an important step towards identifying key molecular factors involved in development of the human fetal endocrine pancreas.

The diabetic phenotype in HNF4A mutation carriers is moderated by the expression of HNF4A isoforms from the P1 promoter during fetal development

OBJECTIVE

Mutations in the alternatively spliced HNF4A gene cause maturity-onset diabetes of the young (MODY). We characterized the spatial and developmental expression patterns of HNF4A transcripts in human tissues and investigated their role as potential moderators of the MODY phenotype.

RESEARCH DESIGN AND METHODS

We measured the expression of HNF4A isoforms in human adult tissues and gestationally staged fetal pancreas by isoform-specific real-time PCR. The correlation between mutation position and age of diagnosis or age-related penetrance was assessed in a cohort of 190 patients with HNF4A mutations.

RESULTS

HNF4A was expressed exclusively from the P2 promoter in adult pancreas, but from 9 weeks until at least 26 weeks after conception, up to 23% of expression in fetal pancreas was of P1 origin. HNF4A4-6 transcripts were not detected in any tissue. In whole pancreas, HNF4A9 expression was greater than in islets isolated from the endocrine pancreas (relative level 22 vs. 7%). Patients with mutations in exons 9 and 10 (absent from HNF4A3, HNF4A6, and HNF4A9 isoforms) developed diabetes later than those with mutations in exons 2-8, where all isoforms were affected (40 vs. 24 years; P = 0.029). Exon 9/10 mutations were also associated with a reduced age-related penetrance (53 vs. 10% without diabetes at age 55 years; P < 0.00001).

CONCLUSIONS

We conclude that isoforms derived from the HNF4A P1 promoter are expressed in human fetal, but not adult, pancreas, and that their presence during pancreatic development may moderate the diabetic phenotype in individuals with mutations in the HNF4A gene.

'To be successful in research, you must ask questions which may not be answered in five, ten or more years'. An interview with Dr. Paul D. Webster III, emeritus professor of medicine, Medical College of Georgia, Augusta, Ga., USA. Interview by Martín E. Fernández-Zapico

Dr. Paul Webster is a pioneer in the field of pancreatic secretion. His work has been instrumental for the cellular characterization of this pancreatic function under physiological or disease conditions. He is a co-founder of the American Pancreatic Association, a landmark action that will certainly benefit future generations in pancreatology. In this interview, Dr. Webster discusses the importance of mentorship and gives advice for young investigators entering pancreatic research. and IAP.

A modified CZ-1 preserving solution for organ transplantation: comparative study with UW preserving solution

BACKGROUND

The University of Wisconsin colloid based preserving solution (UW solution) is the most efficient preserving solution for multiorgan transplantation. Unfortunately, unavailability of delayed organ preserving solutions hindered further progression of cardinal organ transplantation in China. In this study, we validated an organ preserving Changzheng Organ Preserving Solution (CZ-1 solution) and compared it with UW solution.

METHODS

A series of studies were conducted on how and how long CZ-1 solution could preserve the kidneys, livers, hearts, lungs and pancreas of New Zealand rabbits and SD rats. Morphology of transplanted organs was studied by visible microscopy and electron microscopy; biochemical and physiological functions and the survival rate of the organs during prolonged cold storage were studied.

RESULTS

There was no significant difference between CZ-1 and UW solutions in preserving the kidneys, livers, hearts or lungs of rabbits; kidneys, livers, intestinal mucosa or pancreases of SD rats or five deceased donors' testicles. In some aspects, such as preserving rabbits' hearts, rats' intestinal mucosa and pancreases, the effect of CZ-1 solution was superior to UW solution. CZ-1 could safely preserve kidneys for 72 hours, livers for 24 hours, hearts for 18 hours and lungs for 8 hours for SD rats. Twelve kidneys preserved in cold CZ-1 solution for 22 - 31 hours were transplanted successfully and the mean renal function recovery time was (3.83 +/- 1.68) days.

CONCLUSIONS

CZ-1 solution is as effective as UW solution for organ preservation. The development of CZ-1 solution not only reduces costs and improves preservation of organs, but also promotes future development of organ transplantation in China.

PDX-1 functions as a master factor in the pancreas

Various pancreatic transcription factors are involved in pancreas development and beta-cell differentiation. Among them, pancreatic and duodenal homeobox factor-1 (PDX-1) plays a crucial role in pancreas development and beta-cell differentiation, and maintaining mature beta-cell function. MafA is a recently isolated beta-cell-specific transcription factor and functions as a potent activator of insulin gene transcription. These pancreatic transcription factors also play a crucial role in inducing surrogate beta-cells from non-beta-cells and thus could be therapeutic targets for diabetes. On the other hand, under diabetic conditions, expression and/or activities of PDX-1 and MafA in beta-cells are reduced, which leads to suppression of insulin biosynthesis and secretion. Thus, it is likely that alteration of such transcription factors explains, at least in part, the molecular mechanism for beta-cell glucose toxicity found in diabetes.

Dietary phytoestrogens activate AMP-activated protein kinase with improvement in lipid and glucose metabolism

OBJECTIVE

Emerging evidence suggests that dietary phytoestrogens can have beneficial effects on obesity and diabetes, although their mode of action is not known. Here, we investigate the mechanisms mediating the action of dietary phytoestrogens on lipid and glucose metabolism in rodents.

RESEARCH DESIGN AND METHODS

Male CD-1 mice were fed from conception to adulthood with either a high soy-containing diet or a soy-free diet. Serum levels of circulating isoflavones, ghrelin, leptin, free fatty acids, triglycerides, and cholesterol were quantified. Tissue samples were analyzed by quantitative RT-PCR and Western blotting to investigate changes of gene expression and phosphorylation state of key metabolic proteins. Glucose and insulin tolerance tests and euglycemic-hyperinsulinemic clamp were used to assess changes in insulin sensitivity and glucose uptake. In addition, insulin secretion was determined by in situ pancreas perfusion.

RESULTS

In peripheral tissues of soy-fed mice, especially in white adipose tissue, phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase was increased, and expression of genes implicated in peroxisomal fatty acid oxidation and mitochondrial biogenesis was upregulated. Soy-fed mice also showed reduced serum insulin levels and pancreatic insulin content and improved insulin sensitivity due to increased glucose uptake into skeletal muscle. Thus, mice fed with a soy-rich diet have improved adipose and glucose metabolism.

CONCLUSIONS

Dietary soy could prove useful to prevent obesity and associated disorders. Activation of the AMPK pathway by dietary soy is likely involved and may mediate the beneficial effects of dietary soy in peripheral tissues.

Endocannabinoids: some like it fat (and sweet too)

There is growing interest in the commercialisation of the CB(1) receptor antagonist Rimonabant in Europe for the treatment of obesity and the metabolic syndrome. Clinical trials have shown that CB(1) receptor blockers are able to reduce not only food intake but also abdominal adiposity and its metabolic sequelae. Accordingly, CB(1) receptors, and tissue concentrations of endocannabinoids sufficient to activate them, are present in all brain and peripheral organs involved in the control of energy balance, including the hypothalamus, nucleus accumbens, pancreas, adipose tissue, skeletal muscle and liver. At the central level, the endocannabinoid system seems to play a dual role in the regulation of food intake by hedonic and homeostatic energy regulation. At the peripheral level, the endocannabinoid system seems to behave as a system that reduces energy expenditure and directs energy balance towards energy storage into fat. The emerging role of the endocannabinoid system in energy balance at both central and peripheral levels will be discussed in this review.

High levels of endogenous tumor necrosis factor-related apoptosis-inducing ligand expression correlate with increased cell death in human pancreas

OBJECTIVES

Type 1 diabetes (T1D) has been characterized by the T cell-mediated destruction of pancreatic beta cells. Although various members of the tumor necrosis factor (TNF) family, such as Fas ligand or TNF, have recently been implicated in the development of T1D, the lack of TNF-related apoptosis-inducing ligand (TRAIL) expression or function facilitates the onset of T1D. Thus, the goal of the present study was to investigate the expression profiles of TRAIL and its receptors in human pancreas.

METHODS

Pancreata of 31 patients were analyzed by immunohistochemistry using antibodies developed against TRAIL and its receptors. Apoptosis was confirmed by Annexin V-fluorescein isothiocyanate binding and terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end labeling assays.

RESULTS

Acinar cells displayed high levels of TRAIL and death receptor 4, but only low levels of death receptor 5. In contrast, only TRAIL and TRAIL decoy receptors (DcR1, DcR2) were detected in ductal cells. Similarly, Langerhans islets expressed only TRAIL and TRAIL decoy receptor. High levels of TRAIL expression in pancreas correlated with increased number of apoptotic cells.

CONCLUSIONS

Although the expression of TRAIL decoy receptors might be necessary for defense from TRAIL-induced apoptosis, high levels of TRAIL may provide protection for Langerhans islets from the immunological attack of cytotoxic T cells.

[Regeneration of the pancreas]

Pancreatic beta-cells possess a well-regulated insulin secretory property that maintains systemic glucose homeostasis. Although it has long been thought that differentiated beta-cells are nearly static, recent studies have shown that beta-cell mass dynamically changes throughout the lifetime. The beta-cell mass could be maintained by several mechanisms, including self-replication of pre-existing beta-cells, neogenesis from unidentified stem/progenitor cells, and transdifferentiation from differentiated duct or acinar cells. Recent studies have suggested that self-replication of pre-existing beta-cells is a major source for maintenance of beta-cell mass in adult pancreas. However, regeneration of beta-cells from non-beta-cells does occur under certain conditions, especially in vitro culture systems. In this article, recent progress of regenerative medicine of the pancreas is reviewed.

Immunohistochemical studies on the splenic lobe of the pancreas in young Japanese quails (Coturnix c. japonica)

The splenic lobe (Lobus splenicus) of the pancreas of young meat-type quails (Coturnix c. japonica) was examined by immunohistochemical and light microscopic methods. The endocrine cells are mainly grouped as alpha, beta and mixed islets. A large region consisting of alpha cells is located in the central region of the splenic lobe whereas numerous beta islets are detected in the periphery of the splenic lobe. Alpha islets are in the majority composed of toluidine blue positive A cells and a few toluidine blue negative D and / or avian pancreatic polypeptide (APP) endocrine cells. Beta islets contain only a few toluidine blue negative B and a few D cells. Immunohistochemical staining of the splenic lobe reveal in the centre of beta islets numerous insulin immunoreactive cells and scarcely in alpha islets, exocrine tissue and / or among acinar cells. Somatostatin immune-reactive cells form a circular layer in the periphery of beta islets whereas these cells are uniformly distributed throughout the alpha islet parenchyma and exocrine tissue. In conclusion, the morphology but also the endo- and exocrine functions of the splenic lobe of quails are similar to observations in other avian species such as chicken, duck, goose and pigeon.

[Cell lineage tracing of regenerating cells after partial pancreatectomy using pseudo-type retrovirus]

Pancreas is an important mixed gland having both endocrine and exocrine functions, and has been proven regeneration after injury. To explore the cell lineage tracing methods in pancreas in vivo and the regenerate cells source, we used pseudo-type retrovirus to transfect adult mouse pancreas which had been partially pancreatectomized by rubbing the kerf using a cotton stick saturated with retrovirus suspension then injecting 100 microL retrovirus suspension into pancreas, injecting 100 microL retrovirus by caudal vein, or interperitoneally injecting retrovirus respectively. The results showed that the method of rubbing the kerf then injection of retrovirus suspension into pancreas could more effectively mark the pancreatic cells than the caudal vein injection and the intraperitoneal injection did in vivo. Furthermore, this study also found that some acinus cells could accept injury stimulus signals to regenerate through resuming mitosis after pancreatic injury. This study establishes a cell lineage tracing method in pancreas in vivo using retrovirus and offers a clue for gene therapy of pancreatic diseases using retrovirus vectors.

Regulated beta-cell regeneration in the adult mouse pancreas

Several studies have shown that the adult pancreas possesses a limited potential for beta-cell regeneration upon tissue injury. One of the difficulties in studying beta-cell regeneration has been the lack of a robust, synchronized animal model system that would allow controlled regulation of beta-cell loss and subsequent proliferation in adult pancreas. Here we present a transgenic mouse regeneration model in which the c-Myc transcription factor/mutant estrogen receptor (cMycER(TAM)) fusion protein can be specifically activated in mature beta-cells. We have studied these transgenic mice by immunohistochemical and biochemical methods to assess the ablation and posterior regeneration of beta-cells. Activation of the cMycER(TAM) fusion protein results in synchronous and selective beta-cell apoptosis followed by the onset of acute diabetes. Inactivation of c-Myc leads to gradual regeneration of insulin-expressing cells and reversal of diabetes. Our results demonstrate that the mature pancreas has the ability to fully recover from almost complete ablation of all existing beta-cells. Our results also suggest the regeneration of beta-cells is mediated by replication of beta-cells rather than neogenesis from pancreatic ducts.