Local islet remodelling associated with duct lesion-islet complex in adult human pancreas

AIMS/HYPOTHESIS

Islets are thought to be stably present in the adult human pancreas to maintain glucose homeostasis. However, identification of the pancreatic intraepithelial neoplasia (PanIN)-islet complex in mice and the presence of PanIN lesions in adult humans suggest that similar remodelling of islet structure and environment may occur in the human pancreas. To identify islet remodelling in a clinically related setting, we examine human donor pancreases with 3D histology to detect and characterise the human PanIN-islet complex.

METHODS

Cadaveric donor pancreases (26-65 years old, n = 10) were fixed and sectioned (350 μm) for tissue labelling, clearing and microscopy to detect local islet remodelling for 3D analysis of the microenvironment. The remodelled microenvironment was subsequently examined via microtome-based histology for clinical assessment.

RESULTS

In nine pancreases, we identified the unique peri-lobular islet aggregation associated with the PanIN lesion (16 lesion-islet complexes detected; size: 3.18 ± 1.34 mm). Important features of the lesion-islet microenvironment include: (1) formation of intra-islet ducts, (2) acinar atrophy, (3) adipocyte association, (4) inflammation (CD45⁺), (5) stromal accumulation (α-SMA⁺), (6) increase in Ki-67 proliferation index but absence of Ki-67⁺ alpha/beta cells and (7) in-depth and continuous duct-islet cell contacts, forming a cluster. The duct-islet cell cluster and intra-islet ducts suggest likely islet cell neogenesis but not replication.

CONCLUSIONS/INTERPRETATION

We identify local islet remodelling associated with PanIN-islet complex in the adult human pancreas. The tissue remodelling and the evidence of inflammation and stromal accumulation suggest that the PanIN-islet complex is derived from tissue repair after a local injury.

Neurog3 misexpression unravels mouse pancreatic ductal cell plasticity

In the context of type 1 diabetes research and the development of insulin-producing β-cell replacement strategies, whether pancreatic ductal cells retain their developmental capability to adopt an endocrine cell identity remains debated, most likely due to the diversity of models employed to induce pancreatic regeneration. In this work, rather than injuring the pancreas, we developed a mouse model allowing the inducible misexpression of the proendocrine gene Neurog3 in ductal cells in vivo. These animals developed a progressive islet hypertrophy attributed to a proportional increase in all endocrine cell populations. Lineage tracing experiments indicated a continuous neo-generation of endocrine cells exhibiting a ductal ontogeny. Interestingly, the resulting supplementary β-like cells were found to be functional. Based on these findings, we suggest that ductal cells could represent a renewable source of new β-like cells and that strategies aiming at controlling the expression of Neurog3, or of its molecular targets/co-factors, may pave new avenues for the improved treatments of diabetes.

Role of pancreatic duct cell in beta cell neogenesis: A mini review study

Today diabetes mellitus is known as main threatening for health society. Beta cells have pivotal role in energy homeostasis by balance in blood glucose. Proliferation and neogenesis are two factors for preservation of beta cell mass but these have lower rate during adulthood rather than neonatal. Beta cell destruction occurs during diabetes that leads to hyperglycemia. Continues production of beta cell is a therapeutic strategy to keep normal blood glucose and pancreatic duct cell can be one of the sources of new beta cells. Here, we reviewed the role of pancreatic duct cell in production of beta cell based on a chronological order of conducted studies.

FGF-2b and h-PL Transform Duct and Non-Endocrine Human Pancreatic Cells into Endocrine Insulin Secreting Cells by Modulating Differentiating Genes

Background: Diabetes mellitus (DM) is a multifactorial disease orphan of a cure. Regenerative medicine has been proposed as novel strategy for DM therapy. Human fibroblast growth factor (FGF)-2b controls β-cell clusters via autocrine action, and human placental lactogen (hPL)-A increases functional β-cells. We hypothesized whether FGF-2b/hPL-A treatment induces β-cell differentiation from ductal/non-endocrine precursor(s) by modulating specific genes expression. Methods: Human pancreatic ductal-cells (PANC-1) and non-endocrine pancreatic cells were treated with FGF-2b plus hPL-A at 500 ng/mL. Cytofluorimetry and Immunofluorescence have been performed to detect expression of endocrine, ductal and acinar markers. Bromodeoxyuridine incorporation and annexin-V quantified cells proliferation and apoptosis. Insulin secretion was assessed by RIA kit, and electron microscopy analyzed islet-like clusters. Results: Increase in PANC-1 duct cells de-differentiation into islet-like aggregates was observed after FGF-2b/hPL-A treatment showing ultrastructure typical of islets-aggregates. These clusters, after stimulation with FGF-2b/hPL-A, had significant (p < 0.05) increase in insulin, C-peptide, pancreatic and duodenal homeobox 1 (PDX-1), Nkx2.2, Nkx6.1, somatostatin, glucagon, and glucose transporter 2 (Glut-2), compared with control cells. Markers of PANC-1 (Cytokeratin-19, MUC-1, CA19-9) were decreased (p < 0.05). These aggregates after treatment with FGF-2b/hPL-A significantly reduced levels of apoptosis. Conclusions: FGF-2b and hPL-A are promising candidates for regenerative therapy in DM by inducing de-differentiation of stem cells modulating pivotal endocrine genes.

Delivery of TAT/PTD-Fused Proteins/Peptides to Islets via Pancreatic Duct

Delivering cytoprotective proteins/peptides into pancreata prior to islet isolation through protein transduction (PT) is a novel strategy to enhance the yield of viable transplantable islets. Previous work has shown that the protein transduction domain PTD-5 efficiently transduced islets via the pancreatic duct. TAT/PTD is a well-characterized PTD with the capability to cross even the hemato–encephalic barrier. In this study, we investigated the utilization of the 11-aa TAT protein transduction domain (TAT/PTD) to deliver peptides or proteins of different sizes ranging from 1.2 to 120 kDa, as the TAT/PTD and TAT/PTD-BH4 peptide, or the TAT/PTD–β-galactosidase fusion protein, into islets through the pancreatic duct. Using flow cytometry analysis we found that TAT/PTD derivatives transduced practically 100% of the islet cell population. Moreover, confocal laser scanning microscopy in live, nonfixed islets confirmed these results assessing transduction of TAT/PTD molecules into intact nondisaggregated islets. TAT–β-galactosidase peptide conjugated to FITC was not compartment selective, as both cytoplasmic and nucleic cellular compartments were positively stained. Furthermore, TAT–β-galactosidase peptide delivery was highly effective, as even cells located in the inner core region of the islets were transduced. Finally, transduced TAT–β-galactosidase fusion protein was biologically active after islet isolation and manipulation, and islet insulin secretion capability was not compromised by peptide transduction. These findings suggest that the transduction of chimeric TAT/PTD proteins can represent an efficient tool of molecular delivery independent of the size, to enhance or modify a specific phenotype at the nuclei or cytoplasmic level.

β-Cell dedifferentiation, reduced duct cell plasticity, and impaired β-cell mass regeneration in middle-aged rats

Limitations in β-cell regeneration potential in middle-aged animals could contribute to the increased risk to develop diabetes associated with aging. We investigated β-cell regeneration of middle-aged Wistar rats in response to two different regenerative stimuli: partial pancreatectomy (Px + V) and gastrin administration (Px + G). Pancreatic remnants were analyzed 3 and 14 days after surgery. β-Cell mass increased in young animals after Px and was further increased after gastrin treatment. In contrast, β-cell mass did not change after Px or after gastrin treatment in middle-aged rats. β-Cell replication and individual β-cell size were similarly increased after Px in young and middle-aged animals, and β-cell apoptosis was not modified. Nuclear immunolocalization of neurog3 or nkx6.1 in regenerative duct cells, markers of duct cell plasticity, was increased in young but not in middle-aged Px rats. The pancreatic progenitor-associated transcription factors neurog3 and sox9 were upregulated in islet β-cells of middle-aged rats and further increased after Px. The percentage of chromogranin A+/hormone islet cells was significantly increased in the pancreases of middle-aged Px rats. In summary, the potential for compensatory β-cell hyperplasia and hypertrophy was retained in middle-aged rats, but β-cell dedifferentiation and impaired duct cell plasticity limited β-cell regeneration.

Intraislet Pancreatic Ducts Can Give Rise to Insulin-Positive Cells

A key question in diabetes research is whether new β-cells can be derived from endogenous, nonendocrine cells. The potential for pancreatic ductal cells to convert into β-cells is a highly debated issue. To date, it remains unclear what anatomical process would result in duct-derived cells coming to exist within preexisting islets. We used a whole-mount technique to directly visualize the pancreatic ductal network in young wild-type mice, young humans, and wild-type and transgenic mice after partial pancreatectomy. Pancreatic ductal networks, originating from the main ductal tree, were found to reside deep within islets in young mice and humans but not in mature mice or humans. These networks were also not present in normal adult mice after partial pancreatectomy, but TGF-β receptor mutant mice demonstrated formation of these intraislet duct structures after partial pancreatectomy. Genetic and viral lineage tracings were used to determine whether endocrine cells were derived from pancreatic ducts. Lineage tracing confirmed that pancreatic ductal cells can typically convert into new β-cells in normal young developing mice as well as in adult TGF-β signaling mutant mice after partial pancreatectomy. Here the direct visual evidence of ducts growing into islets, along with lineage tracing, not only represents strong evidence for duct cells giving rise to β-cells in the postnatal pancreas but also importantly implicates TGF-β signaling in this process.

Potassium channels in pancreatic duct epithelial cells: their role, function and pathophysiological relevance

Pancreatic ductal epithelial cells play a fundamental role in HCO3 (-) secretion, a process which is essential for maintaining the integrity of the pancreas. Although several studies have implicated impaired HCO3 (-) and fluid secretion as a triggering factor in the development of pancreatitis, the mechanism and regulation of HCO3 (-) secretion is still not completely understood. To date, most studies on the ion transporters that orchestrate ductal HCO3 (-) secretion have focussed on the role of Cl(-)/HCO3 (-) exchangers and Cl(-) channels, whereas much less is known about the role of K(+) channels. However, there is growing evidence that many types of K(+) channels are present in ductal cells where they have an essential role in establishing and maintaining the electrochemical driving force for anion secretion. For this reason, strategies that increase K(+) channel function may help to restore impaired HCO3 (-) and fluid secretion, such as in pancreatitis, and therefore provide novel directions for future pancreatic therapy. In this review, our aims are to summarize the types of K(+) channels found in pancreatic ductal cells and to discuss their individual roles in ductal HCO3 (-) secretion. We will also describe how K(+) channels are involved in pathophysiological conditions and discuss how they could act as new molecular targets for the development of therapeutic approaches to treat pancreatic diseases.

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.

Genomic alterations link Rho family of GTPases to the highly invasive phenotype of pancreas cancer

Pancreas ductal adenocarcinoma (PDAC) is a highly lethal cancer that typically presents as advanced, unresectable disease. This invasive tendency, coupled with intrinsic resistance to standard therapies and genome instability, are major contributors to poor long-term survival. The genetic elements governing the invasive propensity of PDAC have not been well elucidated. Here, in the course of validating resident genes in highly recurrent and focal amplifications in PDAC, we have identified Rio Kinase 3 (RIOK3) as an amplified gene that alters cytoskeletal architecture as well as promotes pancreatic ductal cell migration and invasion. We determined that RIOK3 promotes its invasive activities through activation of the small G protein, Rac. This genomic and functional link to Rac signaling prompted a genome wide survey of other components of the Rho family network, revealing p21 Activated Kinase 4 (PAK4) as another amplified gene in PDAC tumors and cell lines. Like RIOK3, PAK4 promotes pancreas ductal cell motility and invasion. Together, the genomic and functional profiles establish the Rho family GTP-binding proteins as integral to the hallmark invasive nature of this lethal disease.

CFTR gene transfer to human cystic fibrosis pancreatic duct cells using a Sendai virus vector

Cystic fibrosis (CF) is a fatal inherited disease caused by the absence or dysfunction of the CF transmembrane conductance regulator (CFTR) Cl- channel. About 70% of CF patients are exocrine pancreatic insufficient due to failure of the pancreatic ducts to secrete a HCO3- -rich fluid. Our aim in this study was to investigate the potential of a recombinant Sendai virus (SeV) vector to introduce normal CFTR into human CF pancreatic duct (CFPAC-1) cells, and to assess the effect of CFTR gene transfer on the key transporters involved in HCO3- transport. Using polarized cultures of homozygous F508del CFPAC-1 cells as a model for the human CF pancreatic ductal epithelium we showed that SeV was an efficient gene transfer agent when applied to the apical membrane. The presence of functional CFTR was confirmed using iodide efflux assay. CFTR expression had no effect on cell growth, monolayer integrity, and mRNA levels for key transporters in the duct cell (pNBC, AE2, NHE2, NHE3, DRA, and PAT-1), but did upregulate the activity of apical Cl-/HCO3- and Na+/H+ exchangers (NHEs). In CFTR-corrected cells, apical Cl-/HCO3- exchange activity was further enhanced by cAMP, a key feature exhibited by normal pancreatic duct cells. The cAMP stimulated Cl-/HCO3- exchange was inhibited by dihydro-4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (H2-DIDS), but not by a specific CFTR inhibitor, CFTR(inh)-172. Our data show that SeV vector is a potential CFTR gene transfer agent for human pancreatic duct cells and that expression of CFTR in CF cells is associated with a restoration of Cl- and HCO3- transport at the apical membrane.

Stem cells therapy for type 1 diabetes

In this article, we have reviewed the developments of studies of stem cells therapy for type 1 diabetes since this century. Review of the literature was based on computer searches (PubMed) and our studies. Type 1 diabetes can now be ameliorated by islet transplantation, but this treatment is restricted by the scarcity of islet tissue. Hopes for a limitless supply of a substitute for primary islets of Langerhans and progress in stem cell biology have led to research into the feasibility of stem/progenitor cells to generate insulin-producing cells to use in replacement therapies for diabetes. An increasing body of evidence indicated that, in addition to embryonic stem cells, several potential adult stem/progenitor cells, derived from pancreas, liver, spleen, and bone marrow could differentiate into insulin-producing cells in vitro or in vivo. However, significant controversy currently exists in this field. Moreover, safe suppression of autoimmunity or specific tolerance to auto-antigens for patients with type 1 diabetes must be achieved before this promising new technology can lead to a great progress in clinical practice. To prevent type 1 diabetes through genetic engineering of hematopoietic stem cells represents another new strategy. Much basic research is still required.

Functional association of the morphogenic factors with the clusterin for the pancreatic beta-cell differentiation

Several differentiation or morphogenic factors have known to be involved in the developmental process of endocrine pancreas. However, mechanism of action and functional relation of these molecules are not well elucidated particularly in beta-cell formation from adult pancreatic stem cells. We hypothesized that adult pancreatic stem cells could be activated by the functional resumption of the morphogenic factors that were involved in embryonic development of pancreas in the duct system under the specific conditions such as tissue injuries. Besides the well-established genes including Pdx-1 and Ngn-3, we propose the nestin and clusterin as the new morphogenic factors for beta-cell neogenesis and their functional associations. We found extensive in vivo formation of ductules showing a higher replicating ability following the experimental tissue injury. These neogenic ductules were lined with low epithelial cells positive for the nestin, which has been known as neuronal stem cell marker. In in vitro culture, the nestin-rich epithelial cells of the neogenic ductules also displayed extensive self-replication leading to monolayer of epithelial cell explants and transformed into the insulin secreting beta cells as well as duct cells. Thus, we depicted them as nestin-positive duct stem (NPDS) cells. We found a neogenesis specific protein 'clusterin' in the regenerating pancreatic tissues with concomitant increase of Pdx-1 and Ngn-3 expression. The protein is expressed predominantly in the neogenic pancreas undergoing differentiation. In vitro over-expression of the clusterin gene strongly induces beta-cell transformation from neogenic ductal cells. Insulin expression, both insulin mRNA and peptide levels, was increased and showed glucose dependent manner by ectopic expression of clusterin upon the culture of neogenic ductules when compared to the mock-transfected control, implying that the duct cells transformed functional beta cells. We observed that clusterin over-expression led to up-regulation of Pdx-1 and Ngn-3, and clusterin levels were increased upon the transfection of cDNAs of Pdx-1 or Ngn-3, suggesting a close functional association of these morphogenic factors. In conclusion, we suggest that adult pancreatic stem cells can be recapitulated for neogenesis of insulin secreting beta cells not only by reactivation Pdx-1 and Ngn-3, the classical differentiation factors for pancreas development, but also by the intervention of new morphogenic factors including nestin and clusterin. In particular, by modulation of Pdx-1 and Ngn-3, clusterin induces remarkable differentiation of the functional beta cells secreting insulin in response to glucose stimulation.

Human fibroblast growth factor receptor 1-IIIb is a functional fibroblast growth factor receptor expressed in the pancreas and involved in proliferation and movement of pancreatic ductal cells

OBJECTIVES

The possible functions of the human IIIb-messenger RNA splice variant of fibroblast growth factor (FGF) receptor 1 (FGFR-1 IIIb) are yet to be delineated. In this study, the expression and functionality of the human FGFR-1 IIIb were characterized in the pancreas.

METHODS

In situ hybridization with a specific FGFR-1 IIIb probe in human pancreatic tissues demonstrated that FGFR-1 IIIb localized in normal pancreatic acinar and in ductal-like pancreatic cancer cells. To further assess the potential role of this receptor, a full-length human FGFR-1 IIIb was stably expressed in TAKA-1 pancreatic ductal cells not expressing endogenous FGFR-1.

RESULTS

The FGFR-1 IIIb-expressing TAKA-1 cells synthesized a glycosylated 110-kd protein capable of inducing proliferation on incubation with exogenous FGF-1, -2, and -4. These effects were paralleled by tyrosine phosphorylation of FGFR substrate 2 and association of FGFR substrate 2 with FGFR-1 IIIb. The FGF-1, -2, and -10 induced the activation of p44/42 mitogen-activated protein kinase (MAPK), p38 MAPK, and c-Jun N-terminal kinase. Pharmacological inhibition revealed that FGF-induced proliferation was dependent on the concomitant activation of p44/42 MAPK and c-Jun N-terminal kinase. The FGFR-1 IIIb expression enhanced single-cell movement and plating efficacy.

CONCLUSIONS

Our results demonstrate that the human FGFR-1 IIIb variant is a functional FGFR expressed in the pancreas that can alter pancreatic functions that regulate proliferation, adhesion, and movement.

Differentiation of affinity-purified human pancreatic duct cells to beta-cells

To test whether pancreatic duct cells are in vitro progenitors, they were purified from dispersed islet-depleted human pancreatic tissue using CA19-9 antibody. The purified fraction was almost entirely CK19+ with no insulin+ cells, whereas the unpurified cells (crude duct) were 56% CK19+ and 0.4% insulin+ of total cells (0.7% of CK19+ cells). These cells were expanded as monolayers, aggregated under serum-free conditions, and transplanted into normoglycemic NOD/SCID mice. In crude duct grafts, insulin+ cells increased to 6.1% of CK19+ cells. Purified duct cells had slow expansion and poor aggregation, as well as engraftment. The addition of 0.1% cultured stromal cells improved these parameters. These stromal cells contained no CK19+ cells and no insulin by either quantitative RT-PCR or immunohistochemistry; stromal cell aggregates and grafts contained no insulin+ cells. Aggregation of purified duct plus stromal preparations induced insulin+ cells (0.1% of CK19+ cells), with further increase to 1.1% in grafts. Insulin mRNA mirrored these changes. In these grafts, all insulin+ cells were in duct-like structures, while in crude duct grafts, 85% were. Some insulin+ cells coexpressed duct markers (CK19 and CA19-9) and heat shock protein (HSP)27, a marker of nonislet cells, suggesting the transition from duct. Thus, purified duct cells from adult human pancreas can differentiate to insulin-producing cells.

Evaluation of pancreatic endocrine and exocrine function in patients with autoimmune pancreatitis

OBJECTIVES

Up to now, the characteristics of pancreatic endocrine and exocrine functions in autoimmune pancreatitis (AIP) are still unclear. The aim of this study is to evaluate pancreatic functions in AIP compared with those of chronic pancreatitis (CP).

METHODS

Twelve patients with AIP and 25 patients with CP were examined for exocrine and endocrine pancreas. Exocrine function was evaluated by a secretin test. Concerning endocrine function, insulin secretion (C-peptide response) was examined with the glucagon tolerance test and glucagon secretion was examined with the arginine tolerance test. Pathological examination of pancreatic tissues was done on the operative specimens of AIP and CP that could not be clinically excluded from pancreatic cancer.

RESULTS

For the secretin test, 8.3% of patients with AIP showed 1-factor abnormality, which was a reduction in volume, and 41.7% showed 2-factor abnormalities, which were a reduction in volume and amylase output. On the other hand, 44.0% of patients with CP showed only 1-factor abnormality, which was the reduction in the maximum bicarbonate concentration. Autoimmune pancreatitis accompanied with diabetes mellitus showed a reduction both in DeltaC-peptide response (beta-cell response) and Deltaglucagon (alpha-cell response). Histologically, AIP showed lymphoplasmatic cells infiltration surrounding the pancreatic ducts, but basement membranes were intact. Moreover, basement membranes of the duct were injured in CP. Furthermore, islet cells in AIP were revealed as almost intact even though they were surrounded by fibrosis.

CONCLUSIONS

These findings indicate that exocrine dysfunction with AIP is different from CP because AIP induces stenosis of the pancreatic ducts, but ductal cells that possess the function of bicarbonate secretion are intact, and that endocrine dysfunction with AIP was secondary pancreatic diabetes.

Effect of Slc26a6 deletion on apical Cl-/HCO3- exchanger activity and cAMP-stimulated bicarbonate secretion in pancreatic duct

The role of Slc26a6 (PAT1) on apical Cl-/HCO3- exchange and bicarbonate secretion in pancreatic duct cells was investigated using Slc26a6 null and wild-type (WT) mice. Apical Cl-/HCO3- exchange activity was measured with the pH-sensitive dye BCECF in microperfused interlobular ducts. The HCO3(-)-influx mode of apical [Cl-]i/[HCO3-]o exchange (where brackets denote concentration and subscripts i and o denote intra- and extracellular, respectively) was dramatically upregulated in Slc26a6 null mice (P < 0.01 vs. WT), whereas the HCO3(-)-efflux mode of apical [Cl-]o/[HCO3-]i exchange was decreased in Slc26a6 null mice (P < 0.05 vs. WT), suggesting the unidirectionality of the Slc26a6-mediated HCO3- transport. Fluid secretory rate in interlobular ducts were comparable in WT and Slc26a6 null mice (P > 0.05). In addition, when pancreatic juice was collected from whole animal in basal and secretin-stimulated conditions, neither juice volume nor its pH showed differences between WT and Slc26a6 null mice. Semiquantitative RT-PCR demonstrated more than fivefold upregulation in Slc26a3 (DRA) expression in Slc26a6 knockout pancreas. In conclusion, these results point to the role of Slc26a6 in HCO3- efflux at the apical membrane and also suggest the presence of a robust Slc26a3 compensatory upregulation, which can replace the function of Slc26a6 in pancreatic ducts.

Role of FGF1, FGF2 and FGF7 in the development of the pancreas from control and streptozotocin-treated hamsters

Although progress has been made with respect to the growth and transcription factors implicated in pancreatic development, many questions remain unsolved. It has been established that during embryonic life, both endocrine and acinar cells are derived from pancreatic epithelial precursor cells. Growth factors control the proliferation of precursor cells and their ability to differentiate into mature cells, both in pre-natal and in early post-natal life. Pancreatic development during the early post-natal period is an area of great interest for many scientists. In this study we have examined the structure characteristics, functional and proliferative activity of control and diabetic hamster pancreatic ductal, exocrine and beta cells, following treatment with FGFs 1, 2 and 7 in vitro. Light and electron microscopic studies indicated active synthetic processes in these cells under the influence of the investigated FGFs. In our experimental model of diabetes, the labelling index of the cells was significantly higher than in corresponding control groups of hamsters. We established that FGF2 at a concentration of 10 ng/l was responsible for the most prominent effect on ductal cells and beta cells in the diabetic groups. FGF1 at a concentration of 10 ng/l displayed the highest stimulatory effect on exocrine cells in the diabetic groups at post-natal day 10. Taken together these data strongly suggest that FGF1 and FGF2 induce proliferation of pancreatic epithelial cells during the early post-natal period whereas FGF7 is not strictly specific for pancreatic cell proliferation.

Evidence for the homeostatic regulation of induced beta cell mass expansion

AIMS/HYPOTHESIS

Diabetes results from an insufficient insulin-secreting beta cell mass. Restoration of beta cell mass through pharmaceutically induced endogenous beta cell mass expansion may revolutionise diabetes therapy. However, it remains to be determined whether the induced beta cell mass expansion is under homeostatic regulation.

METHODS

Beta cell mass expansion rates were derived from three separate studies of continuous stimulation of islet neogenesis, including the partial duct obstruction of euglycaemic Syrian hamsters, administration of a pentadecapeptide with the same amino acid sequence as residues 104-118 of islet neogenesis-associated protein (INGAP(104-118)) to euglycaemic Syrian hamsters, as well as to euglycaemic CD-1 mice. The incidence of islet neogenesis, average beta cell size, and beta cell replication and apoptotic rates were determined.

RESULTS

Partial duct obstruction led to a approximately 2.5-fold increase in endocrine tissue at day 56 (p<0.05). From day 0 to day 7 the average rate of change of islet area was 12.7% per day, and this rate decreased to 5.3% per day from day 7 to day 42, and to 2.8% per day from day 42 to day 56. Administration of INGAP(104-118) to adult hamsters led to a 31% increase in total beta cell mass at day 30 (p=0.031). From day 0 to day 10 the average rate of beta cell mass expansion was 148 mug/day, whereas from day 10 to day 30 it decreased to 45 mug/day. INGAP(104-118) administration to adult CD-1 mice resulted in an approximately twofold increase in beta cell mass after 31 days (p=0.021). However, at day 90, there was no significant difference vs age-matched control mice (p=0.30), even though the neogenic beta cell mass was approximately fourfold greater (p=0.026). Beta cell replication was decreased by 56% (p<0.048), whereas beta cell apoptosis was fourfold greater (p<0.003) in 90-day INGAP(104-118)-treated mice compared with age-matched control mice.

CONCLUSIONS/INTERPRETATION

These data indicate that in the presence of ongoing islet neogenesis, homeostatic regulatory mechanisms intervene to regulate beta cell mass according to the prevailing metabolic requirements.

Neogenesis and proliferation of beta-cells induced by human betacellulin gene transduction via retrograde pancreatic duct injection of an adenovirus vector

Betacellulin (BTC) has been shown to have a role in the differentiation and proliferation of beta-cells both in vitro and in vivo. We administered a human betacellulin (hBTC) adenovirus vector to male ICR mice via retrograde pancreatic duct injection. As a control, we administered a beta-galactosidase adenovirus vector. In the mice, hBTC protein was mainly overexpressed by pancreatic duct cells. On immunohistochemical analysis, we observed features of beta-cell neogenesis as newly formed insulin-positive cells in the duct cell lining or islet-like cell clusters (ICCs) closely associated with the ducts. The BrdU labeling index of beta-cells was also increased by the betacellulin vector compared with that of control mice. These results indicate that hBTC gene transduction into adult pancreatic duct cells promoted beta-cell differentiation (mainly from duct cells) and proliferation of pre-existing beta-cells, resulting in an increase of the beta-cell mass that improved glucose tolerance in diabetic mice.

Stimulation of cAMP signalling allows isolation of clonal pancreatic precursor cells from adult mouse pancreas

AIMS/HYPOTHESIS

Duct cells of the pancreas are thought to include latent progenitors of islet endocrine cells that can be induced to differentiate by appropriate morphogens. Here we developed a method for isolating pancreatic ductal epithelial cells from adult mice that overcomes the shortcomings of previous methods.

MATERIALS AND METHODS

Pancreatic ductal cells were grown in serum-free DMEM/F12 medium in the presence of cholera toxin or 8-bromo-cyclic adenosine monophosphate, which is known to be an intracellular cAMP generator. Single cell cloning was performed by limiting dilution in serum-free medium.

RESULTS

The isolated clonal cells expressed high levels of cytokeratin and Ipf1 (formerly known as Pdx-1). Adenovirus-mediated expression of ngn3 (also known as Neurog3) and Ptf1a in these cells induced expression of insulin and somatostatin, and of carboxypeptidase A, respectively. Furthermore, albumin production was induced by dexamethasone or by long-term culture in serum-containing medium.

CONCLUSIONS/INTERPRETATION

Stimulation of the cAMP-dependent signalling allowed us to isolate clonal pancreatic ductal cells from adult mice. These cells are able to partially differentiate into endocrine cells, exocrine cells and hepatocyte-like cells and are therefore considered to have the characteristics of endodermal progenitor cells.

The impact of the mTOR inhibitor sirolimus on the proliferation and function of pancreatic islets and ductal cells

AIMS/HYPOTHESIS

The Edmonton Protocol for islet transplantation has provided hope for type 1 diabetic patients. However, this protocol requires lifelong immunosuppression, specifically sirolimus, a cellular antiproliferate. The effect of sirolimus on human pancreatic ductal cells (HDCs) is not known. This may be important since HDCs are believed to be islet precursors. Since neonatal porcine islets (NPIs), which contain many ductal precursor cells, could be a potential clinical source of islets, we also tested the effects of sirolimus on this tissue.

METHODS

HDCs (n=4), NPIs (n=9) and human islets (n=5) were cultured with and without sirolimus (20 ng/ml) for 6 days.

RESULTS

HDCs and NPIs cultured with sirolimus showed a 50 and 28% decrease, respectively, in cell number relative to control (p<0.05). Control cultures expanded 1.65- and 2.44-fold relative to time 0. Decreases in cell number of sirolimus-treated HDCs were not due to apoptosis as measured by TUNEL staining. No functional effects on human islets or NPIs were observed following static incubation with high glucose. Treatment of syngeneically transplanted and naïve BALC/c mice with sirolimus resulted in altered OGTT profiles with prolonged elevation of hyperglycaemia and weight gain. There was no difference in graft and organ insulin content between treatment groups.

CONCLUSIONS/INTERPRETATION

Our results indicate that sirolimus decreases ductal cell numbers in culture and alters glucose-stimulated insulin secretion in vivo. The administration of sirolimus to islet transplant recipients is likely to impair graft function as a result of decreasing ductal neogenesis and induction of insulin resistance.

Development of an in vitro pancreatic tissue model to study regulation of islet neogenesis associated protein expression

Restoration of a functional beta-cell mass in a patient with diabetes may hold the key for curing the disease. In recent years, there has been increasing interest in the development of new strategies to induce beta-cell regeneration and new islet formation in situ and a role for Reg proteins has been suggested. One such protein, islet neogenesis associated protein (INGAP), is a member of the Reg3 family of proteins and has been shown to induce islet neogenesis. Elucidation of the mechanisms and factors involved in the regulation of expression of INGAP and related proteins is, therefore, of great importance. Here, we report the establishment of the first in vitro tissue model of INGAP expression that consists of epithelial cystic structures derived from hamster pancreatic acinar tissue cultured in collagen matrix. The objective of this study was to characterize INGAP expression in this model and to investigate the role of pro-inflammatory cytokines and growth factors. Using quantitative reverse transcriptase PCR, we show that INGAP expression correlates with cyst formation and size suggesting the involvement of intra-luminal pressure associated with cyst growth. We also demonstrate for the first time that INGAP gene expression was significantly induced by treatment with interleukin (IL)-6 and further enhanced by a combination of IL-6 with dexamethazone and nicotinamide. Additionally, our data suggest that the effect of IL-6 on INGAP expression is mediated via the JAK/STAT3 signaling pathway. In summary, the in vitro model of INGAP expression described here represents an important step in the development of strategies for the use of INGAP and related proteins as islet neogenic agents in the pharmacotherapy of both type-1 and type-2 diabetes.

Formation of pancreatic duct epithelium from bone marrow during neonatal development

Recent reports suggest that bone marrow-derived cells engraft and differentiate into pancreatic tissue at very low frequency after pancreatic injury. All such studies have used adult recipients. The aim of our studies was to investigate the potential of bone marrow to contribute to the exocrine and endocrine components of the pancreas during the normal rapid growth of the organ that occurs during the neonatal period. Five to ten million bone marrow cells from adult, male, transgenic, green fluorescent protein (GFP) mice were injected into neonatal nonobese diabetic/severely compromised immunodeficient/beta2microglobulin-null mice 24 hours after birth. Two months after bone marrow transplantation, pancreas tissue was analyzed with fluorescence immunohistochemistry and fluorescence in situ hybridization (FISH). Co-staining of GFP, with anticytokeratin antibody, and with FISH for the presence of donor Y chromosome indicated that up to 40% of ducts (median 4.6%) contained epithelial cells derived from donor bone marrow. In some of these donor-derived ducts, there were clusters of large and small ducts, all comprised of GFP+ epithelium, suggesting that whole branching structures were derived from donor bone marrow. In addition, rare cells that coexpressed GFP and insulin were found within islets. Unlike pancreatic damage models, no bone marrow-derived vascular endothelial cells were found. In contrast to the neonatal recipients, bone marrow transplanted into adult mice rarely generated ductal epithelium or islet cells (p<.05 difference between adult and neonate transplants). These findings demonstrate the existence in bone marrow of pluripotent stem cells or epithelial precursors that can migrate to the pancreas and differentiate into complex organ-specific structures during the neonatal period.

Application of in situ ductal perfusion to facilitate isolation of high-quality RNA from mouse pancreas

A technique to isolate high-quality intact RNA from murine pancreas is described. This technique involves in situ ductal perfusion of the pancreas with an RNase inhibitor prior to removal of the organ for RNA extraction. In this way, the pancreatic RNases are inhibited in situ allowing good yields of intact RNA, suitable for studies on pancreatic gene transcription by real-time PCR or microarray analysis, to be obtained in a reliable way.

Pancreatobiliary afferent recordings in the anaesthetised Australian possum

The sensory innervation to the pancreatobiliary system is poorly characterized. Afferent signals from the gastrointestinal tract and biliary tree are transmitted to the central nervous system via the vagus and spinal nerves. We aimed to record afferent discharge in order to characterize the vagal and splanchnic afferent signals from the possum upper gastrointestinal tract, biliary tree and pancreas. In 21 anaesthetised possums nerve fibres were teased from the vagus or splanchnic nerve for multi-unit recording. Mechanical stimuli consisted of balloon distension of the gallbladder and duodenum (2-7 ml) and fluid distension (0-20 mm Hg) of the bile or pancreatic ducts. Approximately 60% of fibres from all nerves displayed spontaneous discharge. Spinal afferent responses to mechanical stimuli were infrequent (n=13). Increased discharge occurred in response to duodenal (12/99 fibres) or gallbladder (7/96 fibres) distension, but not to bile duct (0/73 fibres) or pancreatic duct (0/51 fibres) distension. Vagal afferent responses to distension of the duodenum or stomach (5-30 ml) were more common (n=8). Increased discharge was recorded in response to duodenal (49/134 fibres), or gastric (22/70 fibres) distension. Responses to gallbladder distension were less frequent (6/99 fibres) and as with the spinal afferent no response to bile duct (0/66) or pancreatic duct (0/70) distension were recorded. We conclude that mechanosensitive afferents in the pancreatobiliary system are relatively rare, particularly within the ducts, and/or that they are adapted to monitor stimuli other than luminal distension.

Is the rat pancreas an appropriate model of the human pancreas?

During my lifetime in pancreatic research, rat and mouse have largely replaced dog and cat in experimental studies. However, as this review clearly demonstrates, the anatomy, physiology and molecular cell biology of the rat pancreas (and also probably the mouse pancreas) differ substantially from those in humans. Indeed, they differ more in rat/mouse than any other common laboratory species. These differences may be irrelevant if one is using the pancreas as a generic model in which to study, say, acinar cell exocytosis or signalling. But if one is interested in more specific aspects of human pancreatic function, especially ductal function, in health and disease, in my opinion the simple answer to the question posed by the title of this article is no: other species are more appropriate.

Islet formation and regeneration

OBJECTIVE

To explore the mechanisms of differentiation and development of pancreatic endocrine cells as well as pancreatic regeneration.

METHODS

Human embryonic pancreatic tissue at 7-14 weeks of gestation was collected. Diabetes mellitus rat model was induced with 65 mg/kg of streptozotocin. Insulin, glucagon, somatostatin, nestin, and cytokeratin 19 (CK19) of pancreatic tissues were observed by immunohistochemistry.

RESULTS

At 9 weeks of gestation, pancreatic epithelial cells began to co-express insulin, glucagon, somatostatin, and CK19 before migration. Islet cells gradually congregated along with the increase of aging, and at 14 weeks of gestation histological examination showed islet formation. At 12 weeks of gestation, nestin-positive cells could be seen in the pancreatic mesenchyme. During early embryogenesis, islet cells of pancreatic ducts co-expressed insulin, glucagon, and somatostatin. During pancreatic regeneration after damage, nestin expression of islet cells increased.

CONCLUSION

In the early stage of embryogenesis, islet cells of primary pancreatic ducts can be differentiated to multipotential endocrine cells before migration. During tissue regeneration, pancreatic stem cells may differentiate and proliferate to form pancreatic islet.

Characterization of H+ and HCO3- transporters in CFPAC-1 human pancreatic duct cells

AIM: To characterize H⁺ and HCO₃^- transporters in polarized CFPAC-1 human pancreatic duct cells, which were derived from a cystic fibrosis patient with the ΔF508 CFTR mutation.

METHODS: CFPAC-1 cells were seeded at high density onto permeable supports and grown to confluence. The cells were loaded with the pH-sensitive fluorescent dye BCECF, and mounted into a perfusion chamber, which allowed the simultaneous perfusion of the basolateral and apical membranes. Transmembrane base flux was calculated from the changes in intracellular pH and the buffering capacity of the cells.

RESULTS: Our results showed differential permeability to HCO₃^-/CO₂ at the apical and basolateral membranes of CFPAC-1 cells. Na⁺/HCO₃^- co-transporters (NBCs) and Cl^-/HCO₃^- exchangers (AEs) were present on the basolateral membrane, and Na⁺/H⁺ exchangers (NHEs) on both the apical and basolateral membranes of the cells. Basolateral HCO₃^- uptake was sensitive to variations of extracellular K⁺ concentration, the membrane permeable carbonic anhydrase (CA) inhibitors acetazolamide (100 µmol/L) and ethoxyzolamide (100 µmol/L), and was partially inhibited by H₂-DIDS (600 µmol/L). The membrane-impermeable CA inhibitor 1-N-(4-sulfamoylphenylethyl)-2,4,6-trimethylpyridine perchlorate did not have any effect on HCO₃^- uptake. The basolateral AE had a much higher activity than that in the apical membrane, whereas there was no such difference with the NHE under resting conditions. Also, 10 µmol/L forskolin did not significantly influence Cl^-/HCO₃^- exchange on the apical and basolateral membranes. The administration of 250 µmol/L H₂-DIDS significantly inhibited the basolateral AE. Amiloride (300 µmol/L) completely inhibited NHEs on both membranes of the cells. RT-PCR revealed the expression of pNBC1, AE2, and NHE1 mRNA.

CONCLUSION: These data suggest that apart from the lack of CFTR and apical Cl^-/HCO₃^- exchanger activity, CFPAC-1 cells express similar H⁺ and HCO₃^- transporters to those observed in native animal tissue.

Diffusion-weighted MR imaging in the evaluation of pancreatic exocrine function before and after secretin stimulation

OBJECTIVES

To evaluate diffusion weighted MR imaging before and after secretin stimulation in the assessment of pancreatic exocrine function in the setting of chronic pancreatitis.

METHODS

Nine patients with severe chronic pancreatitis and sixteen patients without chronic pancreatitis but with a history of chronic alcohol consumption were enrolled in the chronic pancreatitis and risk groups, respectively. Thirty-eight patients without any pancreatic disease or history of alcohol consumption were included in the control group. Diffusion weighted images were obtained before and after secretin administration in all patients. The peak ADC values and times were determined and intergroup differences were compared. A receiver operating characteristic curve (ROC) was used to identify the cutoff values of the peak ADC times for discrimination of control group from risk and chronic pancreatitis groups.

RESULTS

In the control group, a peak increase in ADC value of 57-120% (median: 75%) was observed between 90 s and 4 min (median: 2 min) after administration of secretin (Pattern 1). In the risk group, in 13 patients, a peak increase of 52-150% was observed between 4 and 8 min (median: 7 min; Pattern 2). Peak times were significantly longer in risk group (p < 0.01). In three patients in the risk group, and in all patients in the chronic pancreatitis group, no ADC peak was observed within 10 min following secretin administration (Pattern 3). Using a peak time of 4 min as the cut-off value, a sensitivity of 100% and specificity of 94.7% were achieved in discriminating the control group from the combined risk and chronic pancreatitis groups.

CONCLUSION

Diffusion-weighted MR imaging before and after secretin administration could yield clinically useful information for detecting pathophysiologic alterations in the setting of chronic pancreatitis.

Expression and function of leukaemia inhibitory factor and its receptor in normal and regenerating rat pancreas

AIMS/HYPOTHESIS

It was recently reported that culturing adult exocrine cells in the presence of epidermal growth factor and leukaemia inhibitory factor (LIF) resulted in their transdifferentiation into endocrine beta cells. The aim of this study was to examine the expression and function of LIF in the pancreas.

MATERIALS AND METHODS

We studied the expression of LIF and its receptor components, LIF-receptor-beta and gp130, by immunohistochemistry, western blotting and RT-PCR in normal rat pancreas, pancreas with duct ligation-induced islet neogenesis, and in pancreatic cell cultures. Isolated duct fragments were cultured in the presence of LIF and a janus kinase 2 (JAK2) inhibitor.

RESULTS

LIF was detected by immunohistochemistry, western blot and RT-PCR in the ducts of the normal pancreas. Both LIF-receptor-beta and gp130 were detected by RT-PCR in the pancreas. Immunostaining revealed gp130 exclusively in the ducts and centro-acinar cells. After duct ligation-induced tissue injury, upregulation of LIF and its receptor occurred in rat pancreas. Metaplastic exocrine cells also started to express LIF and this was increased after alloxan treatment. Signalling via LIF-receptor-beta/gp130 involves the JAK/signal transducer and activator of transcription (STAT) pathway. LIF induced increased activation of STAT3 in pancreatic cells. In isolated duct fragments, addition of LIF resulted in a significant increase in duct cell proliferation, while a specific inhibitor of the JAK/STAT signalling pathway inhibited proliferation.

CONCLUSION/INTERPRETATION

Our observations show that LIF and its receptor are expressed in cells from pancreatic ducts. The cytokine plays a role in pancreatic physiology, controls duct cell proliferation and is involved in repair processes following pancreatic injury.

Serum amylase, pancreatic stents, and pancreatitis after sphincter of Oddi manometry

BACKGROUND

Serum amylase levels 2 hours after ERCP predict postprocedure pancreatitis. The value of serum amylase measurements after sphincter of Oddi manometry (SOM) and the effect of pancreatic-duct stent placement on serum amylase are unknown.

METHODS

Records were reviewed for 88 SOM patients who had serum amylase measured 2 hours after the procedure. Post-SOM pancreatitis was defined as pain with a >3-fold elevation of serum amylase on the morning after SOM. "Possible pancreatitis" was defined as pain with a <3-fold elevation of serum amylase on the morning after SOM.

RESULTS

Post-SOM pancreatitis and possible pancreatitis each occurred in 13% of the study cohort. Post-SOM pancreatitis was associated with the absence of a pancreatic stent and occurred in 0% of patients without a stent who had normal 2-hour serum amylase vs. 67% with elevated 2-hour serum amylase (p < 0.01). Among patients who received a stent, pancreatitis occurred in 6%, regardless of whether the 2-hour serum amylase was elevated. Possible pancreatitis occurred mainly in patients who received stents, and it also was associated with elevation of the 2-hour serum amylase.

CONCLUSIONS

Elevation of the serum amylase level 2 hours after SOM predicts post-SOM pancreatitis but only in patients who do not receive a pancreatic stent. Among patients who received a stent, elevated 2-hour serum amylase levels predict subsequent findings that may be caused by attenuated pancreatitis.

Relationship between papillary fibrosis and patency of the accessory pancreatic duct

A study of structure and function of the minor duodenal papilla was carried out on 36 autopsy specimens of the human duodenopancreas. An original perfusion method with manometric control was developed for testing the minor papilla patency, i.e. resistency to intraductal pressure. According to this test, all the specimens were classified as: Type I: non-patent (45%); Type II: patent under normal, physiological pressure (36%); and Type III: patent under increased pressure (19%). After that, the whole minor papilla specimens underwent longitudinal sectioning with HE staining. Light microscopy showed various degrees of fibrosis (mild-45%, moderate-29%, and severe-26%). The correlation between the fibrosis and the patency was significant: papillae with lower degrees of fibrosis were more patent and vice versa. Further, the pancreatic tissue in the Santorini segment of the pancreatic head followed the same manner. No apparent sphincter of the minor papilla was found in any of the specimens analyzed.

Short-term Stimulation Studies on Neonatal Pig Pancreatic Duct-derived Cell Monolayers

Short-term stimulation with insulinotropic factors may induce morphologic and functional changes in primary ductal cell cultures as a potential source of stem cells. We sought to assess the capacity of hepatocyte growth factor (HGF) to induce expression and maturation of proteins--PDX-1 and GLUT-2--and the subsequent beta-cell secretory profiles. HGF, which is involved in pancreatic development, may induce islet beta-cell neogenesis. Primary ductal cell monolayers were cultured in Click's + FBS 10% at 37 degrees C until tissue confluence. The medium was enriched with HGF (10 ng/mL for different periods); controls were treated for similar times with normal culture medium. At the end of the study, three-dimensional islet-like cell aggregates were observed in both conditions. In all conditions immunostaining studies showed positivity for the major endocrine-phenotype cell markers: insulin, PDX-1, glucokinase, and GLUT-2. Furthermore, treatment with HGF for short periods induced the expression of a functionally active, phosphorylated isoform of PDX-1. Finally, we observed that under basal conditions the cells initially and progressively released proinsulin throughout 5 days in all settings. Thereafter proinsulin was gradually replaced by insulin in the culture medium, reflecting a maturation progress. This pattern of insulin maturation and release was more evident when the cells were continuously stimulated with HGF for 12 days. The employed stimuli seemed to differentiate the original ductal cell layers toward endocrine cell phenotypes that synthesize and release proinsulin and subsequently insulin. HGF seems to provide a more efficient differentiation.

P2Y2 and P2Y4 receptors regulate pancreatic Ca(2+)-activated K+ channels differently

Extracellular ATP is an important regulator of transepithelial transport in a number of tissues. In pancreatic ducts, we have shown that ATP modulates epithelial K+ channels via purinergic receptors, most likely the P2Y2 and P2Y4 receptors, but the identity of the involved K+ channels was not clear. In this study, we show by RT-PCR analysis that rat pancreatic ducts express Ca(2+)-activated K+ channels of intermediate conductance (IK) and big conductance (BK), but not small conductance (SK). Possible interactions between P2Y receptors and these Ca(2+)-activated K+ channels were examined in co-expression experiments in Xenopus laevis oocytes. K+ channel activity was measured electrophysiologically in oocytes stimulated with UTP (0.1 mM). UTP stimulation of oocytes expressing P2Y4 receptors and BK channels resulted in a 30% increase in the current through the expressed channels. In contrast, stimulation of P2Y2 receptors led to a 20% inhibition of co-expressed BK channel activity, a response that was sensitive to TEA. Furthermore, co-expression of IK channels with P2Y4 and P2Y2 receptors resulted in a large hyperpolarization and 22-fold and 5-fold activation of currents by UTP, respectively. Taken together, this study shows that there are different interactions between the subtypes of P2Y purinergic receptors and different Ca(2+)-activated K+ channels.

In vitro modeling of human pancreatic duct epithelial cell transformation defines gene expression changes induced by K-ras oncogenic activation in pancreatic carcinogenesis

Genetic analysis of pancreatic ductal adenocarcinomas and their putative precursor lesions, pancreatic intraepithelial neoplasias (PanIN), has shown a multistep molecular paradigm for duct cell carcinogenesis. Mutational activation or inactivation of the K-ras, p16(INK4A), Smad4, and p53 genes occur at progressive and high frequencies in these lesions. Oncogenic activation of the K-ras gene occurs in >90% of pancreatic ductal carcinoma and is found early in the PanIN-carcinoma sequence, but its functional roles remain poorly understood. We show here that the expression of K-ras(G12V) oncogene in a near diploid HPV16-E6E7 gene immortalized human pancreatic duct epithelial cell line originally derived from normal pancreas induced the formation of carcinoma in 50% of severe combined immunodeficient mice implanted with these cells. A tumor cell line established from one of these tumors formed ductal cancer when implanted orthotopically. These cells also showed increased activation of the mitogen-activated protein kinase, AKT, and nuclear factor-kappaB pathways. Microarray expression profiling studies identified 584 genes whose expression seemed specifically up-regulated by the K-ras oncogene expression. Forty-two of these genes have been reported previously as differentially overexpressed in pancreatic cancer cell lines or primary tumors. Real-time PCR confirmed the overexpression of a large number of these genes. Immunohistochemistry done on tissue microarrays constructed from PanIN and pancreatic cancer samples showed laminin beta3 overexpression starting in high-grade PanINs and occurring in >90% of pancreatic ductal carcinoma. The in vitro modeling of human pancreatic duct epithelial cell transformation may provide mechanistic insights on gene expression changes that occur during multistage pancreatic duct cell carcinogenesis.

Association between endocrine pancreas and ductal system. More than an epiphenomenon of endocrine differentiation and development?

Traditional histological descriptions of the pancreas distinguish between the exocrine and the endocrine pancreas, as if they were two functionally distinct glands. This view has been proven incorrect and can be considered obsolete. Interactions between acinar and islet tissues have been well established through numerous studies that reveal the existence of anatomical and functional relationships between these compartments of the gland. Less attention, however, has traditionally been paid to the relationships occurring between the endocrine pancreas and the ductal system. Associations between islet tissue and ducts are considered by most researchers as only a transient epiphenomenon of endocrine development. This article reviews the evidence that has emerged in the last 10 years demonstrating the existence of stable, close, and systematic relationships between these two pancreatic compartments. Functional and pathophysiological implications are considered, and the existence of an "acinar-duct-islet" axis is put forward. The pancreas appears at present to be an integrated organ composed of three functionally related components of well-orchestrated endocrine and exocrine physiological responses.

Toll-like receptor 4 detected in exocrine pancreas and the change of expression in cerulein-induced pancreatitis

OBJECTIVES

To detect Toll-like receptor 4 (TLR4) expression and distribution in rat pancreas and the change of TLR4 expression in cerulein-induced pancreatitis (CIP).

METHODS

Acute pancreatitis was induced by subcutaneous injections of cerulein at a total dose of 20 microg/kg. Immunohistochemistry (IHC) was used to detect and localize TLR4 in rat pancreas, and real-time reverse transcription-polymerase chain reaction (RT-PCR) was used to quantitatively determine the expression of TLR4 mRNA in CIP.

RESULTS

IHC showed the presence of TLR4 in rat pancreas, and its distribution was specifically localized to pancreatic ductal epithelium, vascular endothelium, and islet. No TLR4 staining was detected in exocrine acinar cells. Real-time RT-PCR results revealed low-level TLR4 mRNA expression in the rat pancreas, and the change of TLR4 in CIP only developed within the first 4 hours, which is a rapid up-regulation process that peaks at the first hour. TLR4 mRNA was sustained at baseline level from 4 to 24 hours.

CONCLUSIONS

TLR4 protein was expressed in pancreas and localized to epithelial (pancreatic duct) or endothelial (vessels) tissues; TLR4 responded favorably to the inflammatory process, and the change of expression was characterized as a rapid up-regulation in the early stage of CIP.

Oncogenic K-ras drives cell cycle progression and phenotypic conversion of primary pancreatic duct epithelial cells

We have established a primary pancreatic duct epithelial cell culture (PDEC) system to investigate the relationship between oncogenic activation of K-ras and pancreatic ductal tumorigenesis. We have found that the acute introduction of physiological levels of oncogenic K-ras (K-rasV12) into quiescent PDECs stimulates S-phase entry and induces a pronounced increase in cell size. Both effects are dependent on the functional integrity of the phosphatidylinositol 3'-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway. In addition, K-rasV12 promotes the loss of epithelial E-cadherin and the gain of mesenchymal N-cadherin in PDEC. Our observations indicate that the oncogenic activation of K-ras is sufficient to elicit mitogenic and morphogenic responses in pancreatic ductal cells and hence is likely to play an instructive role in the initiation of pancreatic ductal adenocarcinoma.

Rapid purification of human ductal cells from human pancreatic fractions with surface antibody CA19-9

Generating human insulin-secreting cells for cell therapy of diabetes represents a highly competitive world challenge. Human ductal cells can give rise to islets in vivo and in vitro. The goal of this study was to devise a rapid sorting method to highly purify human ductal cells from pancreatic tissue using a pan-ductal membrane antibody carbohydrate antigen 19-9 (CA19-9). Human pancreatic sections confirmed antibody specificity. The human exocrine fraction (30% ductal cells) was sorted with magnetic bead technology or by FACS. Immunocytochemistry post-sorting determined ductal cell content. The manual magnetic bead technique resulted in 74%+/-2 (n = 4) CA19 positive cells. Whereas the automated AutoMACS technique (n = 5) yielded 92.6%+/-0.5 CA19-9 positive cells with only a minor beta cell contamination (0.2%+/-0.03); cell yield post-sorting was 12.9%+/-2.5 (1.69+/-0.41 x 10(6) cells) with 51.7%+6.5 (n = 5) viability post-sorting. The FACS (n = 6) resulted in 97.1%+/-0.82 CA19-9 positive cells, a cell yield of 25.5%+/-5.6 (5.03+/-1.0 x 10(6)), with 72.1%+/-6.1 viability post-sorting.

CD40 expression on human pancreatic duct cells: role in nuclear factor-kappa B activation and production of pro-inflammatory cytokines

AIMS/HYPOTHESIS

Human pancreatic duct cells are closely associated with islet beta cells, and contaminate islet suspensions transplanted in Type 1 diabetes mellitus patients. Activated duct cells produce cytotoxic mediators and possibly contribute to the pathogenesis of Type 1 diabetes mellitus or islet graft rejection. As CD40 transduces activation signals involved in inflammatory and immune disorders, we investigated CD40 expression on duct cells and their response to CD40 engagement.

METHODS

CD40 expression on human pancreatic duct cells was analysed by flow cytometry and immunohistochemical analyses. To assess the function of CD40 expression on duct cells, activation of the transcription factor nuclear factor-kappa B was determined using electrophoretic mobility shift assay and ELISA. Cytokine mRNA levels were quantified by real-time RT-PCR, and protein levels by Luminex technology.

RESULTS

Isolated human pancreatic duct cells and Capan-2 cell lines were found to express constitutively CD40. The expression of CD40 on duct cells was confirmed in vivo on human normal and pathological pancreatic specimens. CD40 ligation on Capan-2 cells induced rapid nuclear factor-kappa B activation, and supershift assays demonstrated that p50/p65 heterodimers and p50/p50 homodimers were present in the activated complexes in the nucleus. This activation was accompanied by tumour necrosis factor-a and interleukin-1beta mRNA accumulation. Tumour necrosis factor-alpha protein secretion was confirmed in CD40-activated Capan-2 cells and in isolated human pancreatic duct cells.

CONCLUSIONS/INTERPRETATION

Interaction between activated T lymphocytes expressing CD40 ligand and duct cells expressing CD40 may contribute to the immune responses involved in Type 1 diabetes mellitus and islet graft rejection. Interfering with CD40-mediated duct cell activation could alleviate beta cell damage of immune origin.

Expression of pancreatic duodenal hoemobox-1 in pancreatic islet neogenesis after surgical wrapping in rats

BACKGROUND

Surgical wrapping (SW) of the pancreas causes islet neogenesis in rodents. Pancreatic duodenal hoemobox-1 (PDX-1) is one of the transcriptional factors needed by pancreatic stem cells to develop a mature pancreas. The purpose of this study was to determine whether islet neogenesis arises from ductal cells and whether PDX-1 is involved in this process.

METHODS

SW consisted of nonocclusive wrapping of the pancreas in rats. The wrapped pancreas was then harvested, insulin content was measured, and immunohistochemical analysis for insulin, cytokeratin, and PDX-1 was performed.

RESULTS

The endocrine area of the wrapped pancreas significantly increased after SW. Double immunostaining identified cells positive for both insulin and cytokeratin in or along the epithelial cell lining of the ductal structures and in the centroacinar cells. PDX-1-positive cells were detected in both control islets and islets examined after SW, but these cells were observed in the exocrine area only after SW. Double staining also showed that cells positive for PDX-1 but negative for insulin were present in the exocrine area 1 day after SW and that cells positive for both PDX-1 and insulin had developed 3 days after SW.

CONCLUSIONS

In the process of adult islet neogenesis after SW, cells in the acini and ductal structures developed into PDX-1-expressing cells, supposedly progenitor cells, which in turn became insulin-producing cells and thus might be the origin of small islets.

Control of pancreatic exocrine secretion via muscarinic receptors: which subtype(s) are involved? A review

The present report gives an overview of the experimental, pharmacological and molecular investigations that have been undertaken during the past two decades to characterize and identify the muscarinic receptor subtype(s) involved in the cholinergic control of pancreatic exocrine secretion in humans and different animal species. The results published in the literature clearly indicate that both M1 and M3 receptors contribute to the regulation of pancreatic enzyme secretion, although contradictory conclusions have been drawn from secretory studies using specific M1 and M3 receptor antagonists in vivo and in vitro. Binding studies using specific M1 and M3 receptor antagonists have supported the existence of both M1 and M3 receptors on pancreatic acinar cells, which was confirmed by the demonstration of specific mRNA for both receptor subtypes in rat pancreatic acinar cells. In addition, experimental evidence exists that nonacinar (possibly presynaptic) M1 receptors also contribute to the control of pancreatic enzyme secretion. The role of the different muscarinic receptor subtypes in the control of pancreatic fluid and bicarbonate output, however, still needs to be clarified. Future research should cover the evaluation of the relative contribution of the different receptor subtypes to the regulation of pancreatic exocrine function, the localization of the receptors involved as well as possible species differences.

Basolateral anion transport mechanisms underlying fluid secretion by mouse, rat and guinea-pig pancreatic ducts

Fluid secretion by interlobular pancreatic ducts was determined by using video microscopy to measure the rate of swelling of isolated duct segments that had sealed following overnight culture. The aim was to compare the HCO(3)(-) requirement for secretin-evoked secretion in mouse, rat and guinea-pig pancreas. In mouse and rat ducts, fluid secretion could be evoked by 10 nm secretin and 5 microm forskolin in the absence of extracellular HCO(3)(-). In guinea-pig ducts, however, fluid secretion was totally dependent on HCO(3)(-). Forskolin-stimulated fluid secretion by mouse and rat ducts in the absence of HCO(3)(-) was dependent on extracellular Cl(-) and was completely inhibited by bumetanide (30 microm). It was therefore probably mediated by a basolateral Na(+)-K(+)-2Cl(-) cotransporter. In the presence of HCO(3)(-), forskolin-stimulated fluid secretion was reduced approximately 40% by bumetanide, approximately 50% by inhibitors of basolateral HCO(3)(-) uptake (3 microm EIPA and 500 microm H(2)DIDS), and was totally abolished by simultaneous application of all three inhibitors. We conclude that the driving force for secretin-evoked fluid secretion by mouse and rat ducts is provided by parallel basolateral mechanisms: Na(+)-H(+) exchange and Na(+)-HCO(3)(-) cotransport mediating HCO(3)(-) uptake, and Na(+)-K(+)-2Cl(-) cotransport mediating Cl(-) uptake. The absence or inactivity of the Cl(-) uptake pathway in the guinea-pig pancreatic ducts may help to account for the much higher concentrations of HCO(3)(-) secreted in this species.

Rescue of defective pancreatic secretion in cystic-fibrosis cells by suppression of a novel isoform of phospholipase C

BACKGROUND

Cystic fibrosis is caused by mutations in the gene encoding an ion-transport protein, the cystic-fibrosis transmembrane conductance regulator (CFTR). Defective secretion of anions is the primary cause of many of the clinical manifestations of cystic fibrosis, including pancreatic insufficiency. We aimed to identify a molecular mechanism from which a new method to circumvent defective pancreatic secretion could be derived.

METHODS

Multiple-human-tissue RT-PCR and semiquantitative RT-PCR analyses were used to examine gene expression. An antisense technique was used in conjunction with radioimmunoassay, Fura-2 spectrofluorometry, immunohistochemistry, and the short-circuit current technique (Ussing chamber) for elucidation of gene function and its application in rescuing defective pancreatic secretion.

FINDINGS

We cloned a newly identified gene, NYD-SP27, which has structural similarity to an isoform of phospholipase C. NYD-SP27 was expressed endogenously in human pancreatic-duct cells and upregulated in cystic fibrosis. Suppression of NYD-SP27, by transfection of its antisense into human cystic-fibrosis pancreatic-duct cells, resulted in augmentation of phospholipase-C-coupled calcium-ion release and protein kinase C activity, improvement in the amount of mutated CFTR reaching the plasma membrane, and restoration of cAMP-activated pancreatic anion secretion.

INTERPRETATION

NYD-SP27 exerts an inhibitory effect on phospholipase-C-coupled processes that depend on calcium ions and protein kinase C, including CFTR trafficking and function. Its upregulation in pancreatic-duct cells may reveal a previously unsuspected defect in cystic fibrosis contributing to pancreatic insufficiency, and thus represents a new target for pharmacological intervention in cystic fibrosis.

P2X7 receptor activates extracellular signal-regulated kinases ERK1 and ERK2 independently of Ca2+ influx

P2X7 nucleotide receptors modulate a spectrum of cellular events in various cells including epithelia, such as exocrine pancreas. Although the pharmacology and channel properties of the P2X7 receptors have been studied intensively, signal transduction pathways are relatively unknown. In this study we applied a heterologous expression system of rat P2X7 receptors in HEK-293 cells. We followed the receptor expression and function using the enhanced green fluorescent protein (EGFP) tag, activation of intracellular proteins and increases in cellular Ca2+. EGFP-P2X7 receptors localized to the plasma membrane, clusters within the membrane and intracellularly. Stimulation of P2X7 receptors in HEK-293 cells led to an activation of extracellular signal-regulated kinases ERK1 and ERK2 and this activation was seen after just 1 min of stimulation with ATP. Using C- and N-terminal P2X7-receptor mutants we show that the N-terminus is important in activation of ERKs, whereas deletion of the last 230 amino acids in the C-terminus did not effect ERK activation. On the other hand, Ca2+ entry was impaired in C-terminal but not in N-terminal mutants. In cell suspensions prepared from rat pancreas we show that P2X7 receptors also activate ERK1 and ERK2, indicating that these signalling pathways are also turned on in native epithelium.

[Functional radiographic anatomy of the terminal sphincter duct of the biliary pancreatic system]

The improvement of techniques of surgical operations on the bile ducts, especially on their terminal portion, as well as on the pancreas generates a need in deeper knowledge of the function of terminal sphincters of ducts--the general bile and main pancreatic ducts, and Oddi's sphincter that regulate the ingress of bile and pancreatic juice in the digestive tract lumen. This knowledge will make it possible to determine the most adequate variant of treatment, which is closest to the physiological one, in each particular case.

Netrin-1 expression in fetal and regenerating rat pancreas and its effect on the migration of human pancreatic duct and porcine islet precursor cells

AIMS/HYPOTHESIS

We investigated the expression and function of netrin-1, a diffusible laminin-like protein known to regulate neuronal-cell migration in the pancreas. We questioned whether this factor regulates migration of pancreatic epithelial cells and whether this could be involved in islet neogenesis.

METHODS

We studied fetal and adult rat pancreas wherein duct ligation induced islet neogenesis. Netrin-1 expression was analysed by RT-PCR, western blot and immunohistochemistry. In vitro cell migration was measured with a human pancreatic duct cell line (CAPAN-2) and with fetal porcine islet cells. We also studied the expression of two netrin-receptors, neogenin and deleted in colorectal cancer.

RESULTS

We found a transient expression of netrin-1 mRNA and protein in fetal pancreas from E15 to E18, and in adult pancreas after duct ligation. In normal adult pancreas there was very little netrin-1 expression. Netrin-1 expression was observed both in endocrine and exocrine cells. At the immunohistochemical level, it was expressed by islet cells during tissue regeneration. We could show that netrin-1 increases the migration of fetal islet cells and of a ductal cell line, mainly via a chemokinetic effect. From the two well-established netrin receptors, DCC and neogenin, we only found neogenin to be expressed in the pancreas. Neogenin expression coincided with the period of netrin-1 up-regulation.

CONCLUSION/INTERPRETATION

Netrin-1 is involved in pancreatic morphogenesis and tissue remodelling and plays a role in the regulation of duct-cell and fetal-islet cell migration. This can be of importance in islet regeneration, where migration of islet precursors takes place.

PDX-1 protein containing its own antennapedia-like protein transduction domain can transduce pancreatic duct and islet cells

The pancreatic and duodenal homeobox factor-1 (PDX-1), also known as IDX-1/STF-1/IPF1, a homeodomain-containing transcription factor, plays a central role in regulating pancreatic development and insulin gene transcription. Furthermore, even in adults, PDX-1 is associated with islet neogenesis and differentiation of insulin-producing cells from progenitor cells. Here, we report for the first time that PDX-1 protein can permeate cells due to an Antennapedia-like protein transduction domain sequence in its structure and that transduced PDX-1 functions similarly to endogenous PDX-1; it binds to the insulin promoter and activates its expression. PDX-1 protein can also permeate into isolated pancreatic islets, which leads to stimulation of insulin gene expression. Moreover, PDX-1 protein transduced into cultures of pancreatic ducts, thought to be islet progenitor cells, induces insulin gene expression. These data suggest that PDX-1 protein transduction could be a safe and valuable strategy for enhancing insulin gene transcription and for facilitating differentiation of ductal progenitor cells into insulin-producing cells without requiring gene transfer technology.