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

GPR30 is a potential player between islet cells and ductal HCO3- secretion

The primary role of pancreatic ductal HCO3- secretion is to prevent premature activation of digestive enzymes and to provide a vehicle for the delivery of enzymes to the duodenum. In addition, HCO3-is responsible for the neutralization of gastric juice and protect against the formation of protein plugs and viscous mucus. Due to this multifaceted role of HCO3- in the pancreas, its altered functioning can greatly contribute to the development of various exocrine diseases. It is well known that the exocrine and endocrine pancreas interact lively with each other, but not all details of this relationship are known. An interesting finding of a recent study by Jo-Watanabe et al. is that the G protein-coupled oestrogen receptor, GPR30, which is expressed in the endocrine pancreas, can be also activated by HCO3-. This raises the possibility that ductal cells play a key role not only in the exocrine pancreas, but presumably also in endocrine function through HCO3- secretion.

Role of CFTR in diabetes-induced pancreatic ductal fluid and HCO3 - secretion

Type 1 diabetes is a disease of the endocrine pancreas; however, it also affects exocrine function. Although most studies have examined the effects of diabetes on acinar cells, much less is known regarding ductal cells, despite their important protective function in the pancreas. Therefore, we investigated the effect of diabetes on ductal function. Diabetes was induced in wild-type and cystic fibrosis transmembrane conductance regulator (CFTR) knockout mice following an i.p. administration of streptozotocin. Pancreatic ductal fluid and HCO3 - secretion were determined using fluid secretion measurements and fluorescence microscopy, respectively. The expression of ion transporters was measured by real-time PCR and immunohistochemistry. Transmission electron microscopy was used for the morphological characterization of the pancreas. Serum secretin and cholecystokinin levels were measured by an enzyme-linked immunosorbent assay. Ductal fluid and HCO3 - secretion, CFTR activity, and the expression of CFTR, Na+ /H+ exchanger-1, anoctamine-1 and aquaporin-1 were significantly elevated in diabetic mice. Acute or chronic glucose treatment did not affect HCO3 - secretion, but increased alkalizing transporter activity. Inhibition of CFTR significantly reduced HCO3 - secretion in both normal and diabetic mice. Serum levels of secretin and cholecystokinin were unchanged, but the expression of secretin receptors significantly increased in diabetic mice. Diabetes increases fluid and HCO3 - secretion in pancreatic ductal cells, which is associated with the increased function of ion and water transporters, particularly CFTR. KEY POINTS: There is a lively interaction between the exocrine and endocrine pancreas not only under physiological conditions, but also under pathophysiological conditions The most common disease affecting the endocrine part is type-1 diabetes mellitus (T1DM), which is often associated with pancreatic exocrine insufficiency Compared with acinar cells, there is considerably less information regarding the effect of diabetes on pancreatic ductal epithelial cells, despite the fact that the large amount of fluid and HCO3 - produced by ductal cells is essential for maintaining normal pancreatic functions Ductal fluid and HCO3 - secretion increase in T1DM, in which increased cystic fibrosis transmembrane conductance regulator activation plays a central role. We have identified a novel interaction between T1DM and ductal cells. Presumably, the increased ductal secretion represents a defence mechanism in the prevention of diabetes, but further studies are needed to clarify this issue.

Pancreas and islet morphology in cystic fibrosis: clues to the etiology of cystic fibrosis-related diabetes

Cystic fibrosis (CF) is a multi-organ disease caused by loss-of-function mutations in CFTR (which encodes the CF transmembrane conductance regulator ion channel). Cystic fibrosis related diabetes (CFRD) occurs in 40-50% of adults with CF and is associated with significantly increased morbidity and mortality. CFRD arises from insufficient insulin release from β cells in the pancreatic islet, but the mechanisms underlying the loss of β cell function remain understudied. Widespread pathological changes in the CF pancreas provide clues to these mechanisms. The exocrine pancreas is the epicenter of pancreas pathology in CF, with ductal pathology being the initiating event. Loss of CFTR function results in ductal plugging and subsequent obliteration. This in turn leads to destruction of acinar cells, fibrosis and fatty replacement. Despite this adverse environment, islets remain relatively well preserved. However, islet composition and arrangement are abnormal, including a modest decrease in β cells and an increase in α, δ and γ cell abundance. The small amount of available data suggest that substantial loss of pancreatic/islet microvasculature, autonomic nerve fibers and intra-islet macrophages occur. Conversely, T-cell infiltration is increased and, in CFRD, islet amyloid deposition is a frequent occurrence. Together, these pathological changes clearly demonstrate that CF is a disease of the pancreas/islet microenvironment. Any or all of these changes are likely to have a dramatic effect on the β cell, which relies on positive signals from all of these neighboring cell types for its normal function and survival. A thorough characterization of the CF pancreas microenvironment is needed to develop better therapies to treat, and ultimately prevent CFRD.

TRPC3 Regulates Islet Beta-Cell Insulin Secretion

Insulin release is tightly controlled by glucose-stimulated calcium (GSCa) through hitherto equivocal pathways. This study investigates TRPC3, a non-selective cation channel, as a critical regulator of insulin secretion and glucose control. TRPC3's involvement in glucose-stimulated insulin secretion (GSIS) is studied in human and animal islets. TRPC3-dependent in vivo insulin secretion is investigated using pharmacological tools and Trpc3-/- mice. TRPC3's involvement in islet glucose uptake and GSCa is explored using fluorescent glucose analogue 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-D-glucose and calcium imaging. TRPC3 modulation by a small-molecule activator, GSK1702934A, is evaluated in type 2 diabetic mice. TRPC3 is functionally expressed in human and mouse islet beta cells. TRPC3-controlled insulin secretion is KATP -independent and primarily mediated by diacylglycerol channel regulation of the cytosolic calcium oscillations following glucose stimulation. Conversely, glucose uptake in islets is independent of TRPC3. TRPC3 pharmacologic inhibition and knockout in mice lead to defective insulin secretion and glucose intolerance. Subsequently, TRPC3 activation through targeted small-molecule enhances insulin secretion and alleviates diabetes hallmarks in animals. This study imputes a function for TRPC3 at the onset of GSIS. These insights strengthen one's knowledge of insulin secretion physiology and set forth the TRPC3 channel as an appealing candidate for drug development in the treatment of diabetes.

Glycemia and β-cell function before and after elexacaftor/tezacaftor/ivacaftor in youth and adults with cystic fibrosis

Background

Diabetes is prevalent among people with CF (PwCF) and associated with worse clinical outcomes. CFTR modulators are highly effective in improving the disease course of CF. However, the effects of elexacaftor/tezacaftor/ivacaftor (ETI) on glucose metabolism in PwCF are unclear.

Methods

Twenty youth and adults with CF underwent frequently sampled oral glucose tolerance tests (fsOGTT) before and after ETI initiation. Glucose, insulin, and C-peptide were collected at 0, 10, 30, 60, 90, and 120 min after 1.75 g/kg (max 75 g) of dextrose. HbA1c and continuous glucose monitoring (CGM) were collected in a subset. Estimates of insulin secretion (C-peptide index), insulin resistance (HOMA2 IR and IS(OGTT Cpep)), and β-cell function (C-peptide oral disposition index, oDIcoeo), were compared before and after ETI.

Results

Participants were a median (IQR) of 20.4 (14.1, 28.6) years old, 75 % male. Follow-up occurred 10.5 (10.0, 12.3) months after ETI initiation. BMI z-score increased from 0.3 (-0.3, 0.8) to 0.8 (0.4, 1.5), p = 0.013 between visits. No significant differences were observed in glucose tolerance, glucose area under the curve, nor fsOGTT glucose concentrations before and after ETI. Median (IQR) C-peptide index increased from 5.7 (4.1, 8.3) to 8.8 (5.5, 10.8) p = 0.013 and HOMA2 IR increased (p < 0.001), while oDIcoeo was unchanged (p = 0.67). HbA1c decreased from 5.5 % (5.5, 5.8) to 5.4 % (5.2, 5.6) (p = 0.003) while CGM variables did not change.

Conclusions

BMI z-score and measures of both insulin resistance and insulin secretion increased within the first year of ETI initiation. β-cell function adjusted for insulin sensitivity (oDIcoeo) did not change.

Association Between Baseline Uric Acid and the Risk of Acute Pancreatitis: A Prospective Cohort Study

OBJECTIVES

The aim of the study is explore the association between serum uric acid (UA) and acute pancreatitis (AP) risk in a Chinese population.

METHODS

We included 124,316 participants who enrolled in the Kailuan cohort from 2006 to 2009. We fitted Cox models to estimate the correlation between UA and AP.

RESULT

During an average follow-up of 11.97 years (standard deviation, 2.16 years), 396 AP developed. The incidence rates from quartile 1 to quartile 4 of AP were 20.76, 18.78, 30.58, and 36.79 per 100,000 person-years, respectively. Multivariate analysis showed a significantly increased risk in quartile 3 (hazard ratio [HR], 1.42; 95% confidence interval [CI], 1.05-1.91) and quartile 4 (HR, 1.61; 95% CI, 1.19-2.17) compared with quartile 1. The association may be modified by alcohol use (P for interaction = 0.017). The quartile 4 group with excessive alcohol consumption showed an enormously increased risk of AP (HR, 9.09; 95% CI, 1.18-70.21) than those without (HR, 1.46; 95% CI, 1.07-2.00).

CONCLUSIONS

Elevated serum UA is an independent risk factor for AP. Surveillance of serum UA, especially among heavy drinkers, may be helpful for AP prevention.

Calcium imaging in intact mouse acinar cells in acute pancreas tissue slices

The physiology and pathophysiology of the exocrine pancreas are in close connection to changes in intra-cellular Ca²⁺ concentration. Most of our knowledge is based on in vitro experiments on acinar cells or acini enzymatically isolated from their surroundings, which can alter their structure, physiology, and limit our understanding. Due to these limitations, the acute pancreas tissue slice technique was introduced almost two decades ago as a complementary approach to assess the morphology and physiology of both the endocrine and exocrine pancreas in a more conserved in situ setting. In this study, we extend previous work to functional multicellular calcium imaging on acinar cells in tissue slices. The viability and morphological characteristics of acinar cells within the tissue slice were assessed using the LIVE/DEAD assay, transmission electron microscopy, and immunofluorescence imaging. The main aim of our study was to characterize the responses of acinar cells to stimulation with acetylcholine and compare them with responses to cerulein in pancreatic tissue slices, with special emphasis on inter-cellular and inter-acinar heterogeneity and coupling. To this end, calcium imaging was performed employing confocal microscopy during stimulation with a wide range of acetylcholine concentrations and selected concentrations of cerulein. We show that various calcium oscillation parameters depend monotonically on the stimulus concentration and that the activity is rather well synchronized within acini, but not between acini. The acute pancreas tissue slice represents a viable and reliable experimental approach for the evaluation of both intra- and inter-cellular signaling characteristics of acinar cell calcium dynamics. It can be utilized to assess many cells simultaneously with a high spatiotemporal resolution, thus providing an efficient and high-yield platform for future studies of normal acinar cell biology, pathophysiology, and screening pharmacological substances.

Islet Function in the Pathogenesis of Cystic Fibrosis-Related Diabetes Mellitus

Cystic fibrosis-related diabetes mellitus (CFRD) is the most common non-pulmonary co-morbidity in cystic fibrosis (CF). CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR), which leads to aberrant luminal fluid secretions in organs such as the lungs and pancreas. How dysfunctional CFTR leads to CFRD is still under debate. Both intrinsic effects of dysfunctional CFTR in hormone secreting cells of the islets and effects of exocrine damage have been proposed. In the current review, we discuss these non-mutually exclusive hypotheses with a special focus on how dysfunctional CFTR in endocrine cells may contribute to an altered glucose homeostasis. We outline the proposed role of CFTR in the molecular pathways of β-cell insulin secretion and α-cell glucagon secretion, and touch upon the importance of the exocrine pancreas and intra-pancreatic crosstalk for proper islet function.

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

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

Tumor-insular Complex in Neoadjuvant Treated Pancreatic Ductal Adenocarcinoma Is Associated With Higher Residual Tumor

The tumor microenvironment in pancreatic ductal adenocarcinoma (PDAC) plays a vital role in treatment response, and therefore, patient survival. We and others have observed an intimate association of neoplastic ductal cells with non-neoplastic islet cells, recapitulating the ductoinsular complex. We define this phenomenon as tumor-insular complex (TIC). Herein, we describe the clinicopathologic characteristics of TIC in neoadjuvant treated PDAC cases for the first time. We retrospectively reviewed the pathology of 105 cases of neoadjuvant treated PDAC resected at our institution. TIC was noted in 35 cases (33.3%), the mean tumor bed size was 2.7±1.0 cm, mean percentage of residual tumor 40±28% and mean Residual Tumor Index (RTI) (an index previously established as a prognostic parameter by our group) was 1.1±1.0. TIC was significantly associated with perineural invasion (P=0.001), higher tumor bed size (P=0.007), percentage of residual tumor (P=0.009), RTI (P=0.001), ypT stage (P=0.045), and poor treatment response, grouped by a previously established criteria (P=0.010). Using our prior binary reported prognostic cutoff for RTI of ≤0.35 and >0.35, TIC was associated with a RTI >0.35 (P=0.002). Moreover, patients who did not receive neoadjuvant radiation were associated with a higher frequency of TIC (P=0.003). In this cohort, RTI but not TIC was also shown to be a significant independent prognosticator for recurrence-free survival and overall survival on multivariate analysis. In conclusion, TIC is significantly associated with a more aggressive neoplasm which shows a poor treatment response. Further studies will be needed to better understand the tumor biology of TICs.

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

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

Survival in a bad neighborhood: pancreatic islets in cystic fibrosis

In cystic fibrosis (CF), ductal plugging and acinar loss result in rapid decline of exocrine pancreatic function. This destructive process results in remodeled islets, with only a modest reduction in insulin producing β cells. However, β-cell function is profoundly impaired, with decreased insulin release and abnormal glucose tolerance being present even in infants with CF. Ultimately, roughly half of CF subjects develop diabetes (termed CF-related diabetes, CFRD). Importantly, CFRD increases CF morbidity and mortality via worsening catabolism and pulmonary disease. Current accepted treatment options for CFRD are aimed at insulin replacement, thereby improving glycemia as well as preventing nutritional losses and lung decline. CFRD is a unique form of diabetes with a distinct pathophysiology that is as yet incompletely understood. Recent studies highlight emerging areas of interest. First, islet inflammation and lymphocyte infiltration are common even in young children with CF and may contribute to β-cell failure. Second, controversy exists in the literature regarding the presence/importance of β-cell intrinsic functions of CFTR and its direct role in modulating insulin release. Third, loss of the CF transmembrane conductance regulator (CFTR) from pancreatic ductal epithelium, the predominant site of its synthesis, results in paracrine effects that impair insulin release. Finally, the degree of β-cell loss in CFRD does not appear sufficient to explain the deficit in insulin release. Thus, it may be possible to enhance the function of the remaining β cells using strategies such as targeting islet inflammation or ductal CFTR deficiency to effectively treat or even prevent CFRD.

The Interface of Pancreatic Cancer With Diabetes, Obesity, and Inflammation: Research Gaps and Opportunities: Summary of a National Institute of Diabetes and Digestive and Kidney Diseases Workshop

A workshop on "The Interface of Pancreatic Cancer with Diabetes, Obesity, and Inflammation: Research Gaps and Opportunities" was held by the National Institute of Diabetes and Digestive and Kidney Diseases on October 12, 2017. The purpose of the workshop was to explore the relationship and possible mechanisms of the increased risk of pancreatic ductal adenocarcinoma (PDAC) related to diabetes, the role of altered intracellular energy metabolism in PDAC, the mechanisms and biomarkers of diabetes caused by PDAC, the mechanisms of the increased risk of PDAC associated with obesity, and the role of inflammatory events and mediators as contributing causes of the development of PDAC. Workshop faculty reviewed the state of the current knowledge in these areas and made recommendations for future research efforts. Further knowledge is needed to elucidate the basic mechanisms contributing to the role of hyperinsulinemia, hyperglycemia, adipokines, and acute and chronic inflammatory events on the development of PDAC.

Diabetes mellitus secondary to pancreatic diseases (type 3c): The effect of smoking on the exocrine-endocrine interactions of the pancreas

The present study was conducted to ascertain how cigarette smoke affects the exocrine-endocrine interactions of the human pancreas with diabetes mellitus secondary to pancreatic diseases (type 3c). Blood has been collected from smoking and non-smoking healthy individuals as well as from patients with diagnosed chronic pancreatitis and diabetes type 3c. The concentrations of interleukin-6, endothelin-1 and insulin in the plasma were determined by enzyme-linked immunosorbent assay (ELISA) tests. The activities of amylase and lipase in the serum, as well as the lipid profile, creatinine, uric acid and urea concentrations, were measured using colorimetric methods. Samples of normal pancreatic tissue and chronic pancreatitis were verified histopathologically and then interleukin-6, endothelin-1, insulin and glucagon were localized by immunohistochemical staining using a monoclonal anti-human antibody. The highest levels of interleukin-6 and endothelin-1 and the lowest levels of insulin and glucagon intensity from the immunostaining were observed in smoking patients with diabetes. In all smoking patients with pancreatitis and diabetes, there was a significant elevation in interleukin-6 and endothelin-1 concentration and amylase and lipase activities, hyperlipidaemia and a lower value of estimated glomerular filtration rate and blood urea nitrogen when compared to non-smokers. Our study confirmed that smoking exerts a pro-inflammatory effect and disturbs the exocrine-endocrine interactions of the pancreas.

Cold-perfusion decellularization of whole-organ porcine pancreas supports human fetal pancreatic cell attachment and expression of endocrine and exocrine markers

Despite progress in the field of decellularization and recellularization, the outcome for pancreas has not been adequate. This might be due to the challenging dual nature of pancreas with both endocrine and exocrine tissues. We aimed to develop a novel and efficient cold-perfusion method for decellularization of porcine pancreas and recellularize acellular scaffolds with human fetal pancreatic stem cells. Decellularization of whole porcine pancreas at 4°C with sodium deoxycholate, Triton X-100 and DNase efficiently removed cellular material, while preserving the extracellular matrix structure. Furthermore, recellularization of acellular pieces with human fetal pancreatic stem cells for 14 days showed attached and proliferating cells. Both endocrine (C-peptide and PDX1) and exocrine (glucagon and α-amylase) markers were expressed in recellularized tissues. Thus, cold-perfusion can successfully decellularize porcine pancreas, which when recellularized with human fetal pancreatic stem cells shows relevant endocrine and exocrine phenotypes. Decellularized pancreas is a promising biomaterial and might translate to clinical relevance for treatment of diabetes.

Alkaline pH induces IRR-mediated phosphorylation of IRS-1 and actin cytoskeleton remodeling in a pancreatic beta cell line

Secretion of mildly alkaline (pH 8.0-8.5) juice to intestines is one of the key functions of the pancreas. Recent reports indicate that the pancreatic duct system containing the alkaline juice may adjoin the endocrine cells of pancreatic islets. We have previously identified the insulin receptor-related receptor (IRR) that is expressed in islets as a sensor of mildly alkaline extracellular media. In this study, we show that those islet cells that are in contact with the excretory ducts are also IRR-expressing cells. We further analyzed the effects of alkaline media on pancreatic beta cell line MIN6. Activation of endogenous IRR but not of the insulin receptor was detected that could be inhibited with linsitinib. The IRR autophosphorylation correlated with pH-dependent linsitinib-sensitive activation of insulin receptor substrate 1 (IRS-1), the primary adaptor in the insulin signaling pathway. However, in contrast with insulin stimulation, no protein kinase B (Akt/PKB) phosphorylation was detected as a result of alkali treatment. We observed overexpression of several early response genes (EGR2, IER2, FOSB, EGR1 and NPAS4) upon alkali treatment of MIN6 cells but those were IRR-independent. The alkaline medium but not insulin also triggered actin cytoskeleton remodeling that was blocked by pre-incubation with linsitinib. We propose that the activation of IRR by alkali might be part of a local loop of signaling between the exocrine and endocrine parts of the pancreas where alkalinization of the juice facilitate insulin release that increases the volume of secreted juice to control its pH and bicabonate content.

Hyaluronic Acid/Collagen Hydrogel as an Alternative to Alginate for Long-Term Immunoprotected Islet Transplantation<sup/>

Alginate has long been the material of choice for immunoprotection of islets due to its low cost and ability to easily form microspheres. Unfortunately, this seaweed-derived material is notoriously prone to fibrotic overgrowth in vivo, resulting in premature graft failure. The purpose of this study was to test an alternative, hyaluronic acid (HA-COL), for in vitro function, viability, and allogeneic islet transplant outcomes in diabetic rats. In vitro studies indicated that the HA-COL gel had diffusion characteristics that would allow small molecules such as glucose and insulin to enter and exit the gel, whereas larger molecules (70 and 500 kDa dextrans) were impeded from diffusing past the gel edge in 24 h. Islets encapsulated in HA-COL hydrogel showed significantly improved in vitro viability over unencapsulated islets and retained their morphology and glucose sensitivity for 28 days. When unencapsulated allogeneic islet transplants were administered to the omentum of outbred rats, they initially were normoglycemic, but by 11 days returned to hyperglycemia. Immunohistological examination of the grafts and surrounding tissue indicated strong graft rejection. By comparison, when using the same outbred strain of rats, allogeneic transplantation of islets within the HA-COL gel reversed long-term diabetes and prevented graft rejection in all animals. Animals were sacrificed at 40, 52, 64, and 80 weeks for evaluation, and all were non-diabetic at sacrifice. Explanted grafts revealed viable islets in the transplant site as well as intact hydrogel, with little or no evidence of fibrotic overgrowth or cellular rejection. The results of these studies demonstrate great potential for HA-COL hydrogel as an alternative to sodium alginate for long-term immunoprotected islet transplantation.

Reciprocal stimulation of pancreatic acinar and stellate cells in a novel long-term in vitro co-culture model

BACKGROUND/OBJECTIVES

Pancreatic stellate cells (PSCs) are the key fibrogenic cells in the pancreas. Acinar cell injury is known to trigger PSC activation. To facilitate the experimental analysis of the crosstalk between acinar cells and PSCs, an in vitro system for their long-term co-cultivation was developed.

MATERIALS AND METHODS

PSCs and acinar cells capable of retaining their secretory phenotype in long-term in vitro culture were obtained from mouse pancreata. A dual-chamber co-culture model was built in 24-well format with acinar cells seeded in the wells and PSCs in tissue culture inserts. Acinar cell-3T3 fibroblast co-cultures served as controls. After 4-day maintenance, the acinar compartment was analyzed for cell morphology, secretory capability, necrosis (HMGB1), apoptosis (TUNEL) and inflammation (NFκB). PSCs were analyzed for migratory activity and extracellular matrix (ECM) protein expression. The results were compared to parallel monocultures.

RESULTS

Acinar cells in monoculture and in co-culture with fibroblasts exhibited a healthy monolayer arrangement and an ability to respond to 0.1 nM caerulein stimulus by increased amylase release. Co-culture with PSCs caused marked changes in acinar cell morphology and rendered them insensitive to secretagogue stimulus. Activation of NFκB and necrotic changes, but not apoptosis, were identified in co-cultured acinar cells. Co-culture increased the migratory activity and ECM protein expression of PSCs.

CONCLUSIONS

Humoral interactions between acinar and PSCs in co-culture were shown to reciprocally affect their cellular functions. With its two separable cell compartments the co-culture system provides a versatile culture setting that allows independent manipulation and analysis of both cell types.

Effects of allogenic fetal pancreatic tissue transplantation on regeneration of islet cells in recipient rats with alloxan-induced diabetes mellitus

The linear parameters and number of Langerhans islets were evaluated in rats with alloxaninduced diabetes mellitus after transplantation of fetal pancreatic tissue to the anterior chamber of the eye. The islets significantly increased in size by week 3 after surgery and a trend to an increase in their number was observed.

Exocrine pancreatic insufficiency in diabetic patients: prevalence, mechanisms, and treatment

Pancreas is a doubled-entity organ, with both an exocrine and an endocrine component, reciprocally interacting in a composed system whose function is relevant for digestion, absorption, and homeostasis of nutrients. Thus, it is not surprising that disorders of the exocrine pancreas also affect the endocrine system and vice versa. It is well-known that patients with chronic pancreatitis develop a peculiar form of diabetes (type III), caused by destruction and fibrotic injury of islet cells. However, less is known on the influence of diabetes on pancreatic exocrine function. Pancreatic exocrine insufficiency (PEI) has been reported to be common in diabetics, with a prevalence widely ranging, in different studies, in both type I (25-74%) and type II (28-54%) diabetes. A long disease duration, high insulin requirement, and poor glycemic control seem to be risk factors for PEI occurrence. The impact of pancreatic exocrine replacement therapy on glycemic, insulin, and incretins profiles has not been fully elucidated. The present paper is aimed at reviewing published studies investigating the prevalence of PEI in diabetic patients and factors associated with its occurrence.

The ductal origin of structural and functional heterogeneity between pancreatic islets

Islets form in the pancreas after the first endocrine cells have arisen as either single cells or small cell clusters in the epithelial cords. These cords constitute the developing pancreas in one of its earliest recognizable stages. Islet formation begins at the time the cords transform into a branching ductal system, continues while the ductal system expands, and finally stops before the exocrine tissue of ducts and acini reaches its final expansion. Thus, islets continuously arise from founder cells located in the branching and ramifying ducts. Islets arising from proximal duct cells locate between the exocrine lobules, develop strong autonomic and sensory innervations, and pass their blood to efferent veins (insulo-venous efferent system). Islets arising from cells of more distal ducts locate within the exocrine lobules, respond to nerve impulses ending at neighbouring blood vessels, and pass their blood to the surrounding acini (insulo-acinar portal system). Consequently, the section of the ductal system from which an islet arises determines to a large extent its future neighbouring tissue, architecture, properties, and functions. We note that islets interlobular in position are frequently found in rodents (rats and mice), whereas intralobularly-located, peripheral duct islets prevail in humans and cattle. Also, we expound on bovine foetal Laguesse islets as a prominent foetal type of type 1 interlobular neuro-insular complexes, similar to neuro-insular associations frequently found in rodents. Finally, we consider the probable physiological and pathophysiological implications of the different islet positions within and between species.

Purinergic signalling and diabetes

The pancreas is an organ with a central role in nutrient breakdown, nutrient sensing and release of hormones regulating whole body nutrient homeostasis. In diabetes mellitus, the balance is broken-cells can be starving in the midst of plenty. There are indications that the incidence of diabetes type 1 and 2, and possibly pancreatogenic diabetes, is rising globally. Events leading to insulin secretion and action are complex, but there is emerging evidence that intracellular nucleotides and nucleotides are not only important as intracellular energy molecules but also as extracellular signalling molecules in purinergic signalling cascades. This signalling takes place at the level of the pancreas, where the close apposition of various cells-endocrine, exocrine, stromal and immune cells-contributes to the integrated function. Following an introduction to diabetes, the pancreas and purinergic signalling, we will focus on the role of purinergic signalling and its changes associated with diabetes in the pancreas and selected tissues/organ systems affected by hyperglycaemia and other stress molecules of diabetes. Since this is the first review of this kind, a comprehensive historical angle is taken, and common and divergent roles of receptors for nucleotides and nucleosides in different organ systems will be given. This integrated picture will aid our understanding of the challenges of the potential and currently used drugs targeted to specific organ/cells or disorders associated with diabetes.

The evaluation of serum amylase in the patients of type 2 diabetes mellitus, with a possible correlation with the pancreatic functions

BACKGROUND

Diabetes mellitus is a chronic metabolic disorder which is associated with hyperglycaemia. It is caused by a derangement in the secretion or function of the endocrinal portion of the pancreas. There is a close anatomical and functional relationship between its exocrine and endocrine portions. To address this issue, the current study was designed to evaluate the blood glucose and the amylase levels of diabetic patients as representatives of the two portions of the pancreas respectively.

AIMS AND OBJECTIVES

The aim of the present study was to determine the blood glucose, serum amylase and the serum lipid profile in known cases of type 2 Diabetes Mellitus and to compare and correlate these parameters with those of age and sex matched healthy controls.

MATERIAL AND METHODS

One hundred ten patients of type 2 Diabetes mellitus, who were already diagnosed and were taking treatment, were included in this study. 30 age and sex matched healthy individuals were recruited as the control group in our study. Fasting venous blood samples were collected from the patients as well as the controls and they were analysed by using an automated analyser for blood glucose, serum amylase and the lipid profile (serum triglycerides, total cholesterol, high density lipoproteins and low density lipoproteins). The results were analyzed statistically by using the Student's "t" test and correlation coefficients.

RESULTS

Significantly low serum amylase levels were found in the diabetic patients as compared to those in the healthy controls (p value <0.001). Also, the levels of fasting serum total cholesterol, triglycerides and the low density lipoproteins were significantly higher in the patients as compared to those in the controls, with p values of <0.05, <0.001 and <0.001 respectively. The HDL (high density lipoprotein) level was found to be lower in the diabetic patients (p value <0.001).

CONCLUSIONS

From our study, it was concluded that in type 2 Diabetes mellitus, wherever the blood glucose level was higher, the serum amylase activity was found to be significantly lower. This reflected the derangement in the endocrine-exocrine axis of the pancreas, as a disease which affected any portion of an organ would affect the adjoining area of that organ functionally. This fact must be kept in mind while the patients are treated.

The fractal spatial distribution of pancreatic islets in three dimensions: a self-avoiding growth model

The islets of Langerhans, responsible for controlling blood glucose levels, are dispersed within the pancreas. A universal power law governing the fractal spatial distribution of islets in two-dimensional pancreatic sections has been reported. However, the fractal geometry in the actual three-dimensional pancreas volume, and the developmental process that gives rise to such a self-similar structure, has not been investigated. Here, we examined the three-dimensional spatial distribution of islets in intact mouse pancreata using optical projection tomography and found a power law with a fractal dimension of 2.1. Furthermore, based on two-dimensional pancreatic sections of human autopsies, we found that the distribution of human islets also follows a universal power law with a fractal dimension of 1.5 in adult pancreata, which agrees with the value previously reported in smaller mammalian pancreas sections. Finally, we developed a self-avoiding growth model for the development of the islet distribution and found that the fractal nature of the spatial islet distribution may be associated with the self-avoidance in the branching process of vascularization in the pancreas.

Dual origin, development, and fate of bovine pancreatic islets

Endocrine cells are evident at an early stage in bovine pancreatic development when the pancreas still consists of primitive epithelial cords. At this stage, the endocrine cells are interspersed between the precursor cells destined to form the ductulo-acinar trees of later exocrine lobules. We here demonstrate that, in bovine fetuses of crown rump length ≥ 11 cm, the endocrine cells become increasingly segregated from the developing exocrine pancreas by assembly into two units that differ in histogenesis, architecture, and fate. Small numbers of 'perilobular giant islets' are distinguishable from larger numbers of 'intralobular small islets'. The two types of islets arise in parallel from the ends of the ductal tree. Aside from differences in number, location, and size, the giant and small islets differ in cellular composition (predominantly insulin-synthesising cells vs. mixtures of endocrine cells), morphology (epithelial trabeculae with gyriform and rosette-like appearance vs. compact circular arrangements of endocrine cells), and in their relationships to intrapancreatic ganglia and nerves. A further difference becomes apparent during the antenatal period; while the 'interlobular small islets' persist in the pancreata of calves and adult cattle, the perilobular giant islets are subject to regression, characterised by involution of the parenchyma, extensive haemorrhage, leukocyte infiltration (myeloid and T-cells) and progressive fibrotic replacement. In conclusion, epithelial precursor cells of the ductolo-acinar tree may give rise to populations of pancreatic islets with different histomorphology, cellular composition and fates. This should be taken into account when using these cells for the generation of pancreatic islets for transplantation therapy.

Immunohistochemical localization of somatostatin and pancreatic polypeptide in smokers with chronic pancreatitis

Recent studies have demonstrated a significant role of tobacco smoking in the development of chronic pancreatitis. Although there are published papers on the effects of cigarette smoking on insulin secretion in patients, no data are available on the effects of smoking on pancreatic endocrine cells secreting somatostatin and pancreatic polypeptide. The aim of the study was to evaluate the effects of cigarette smoking on endocrine pancreatic function by immunolocalization of somatostatin and pancreatic polypeptide in the pancreas from smokers and non-smoking patients with chronic pancreatitis in comparison with healthy controls. The LSAB2-HRP technique with polyclonal antibodies was used for the immunolocalization of somatostatin and pancreatic polypeptide in histological preparations of the pancreas. The intensity of immunohistochemical reaction was calculated with digital image analysis. The study demonstrated increased numbers of somatostatin (D) secreting cells and pancreatic polypeptide (PP) cells and their altered location in pancreatic islets and parenchyma of smoking patients with chronic pancreatitis, as compared to non-smoking patients and healthy controls. Smoking patients showed significantly higher immunostaining of the hormones in the pancreas compared to non-smoking patients and healthy persons. This study indicates that smoking may play a significant role in the development of endocrine disturbances in the development of chronic pancreatitis.

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

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

The Renin-angiotensin system and reactive oxygen species: implications in pancreatitis

SIGNIFICANCE

The renin-angiotensin system (RAS) is a circulating hormonal system involved in the regulation of blood pressure and circulating fluid electrolytes. Recent findings have revealed that locally generated angiotensin (Ang) II plays a pivotal role in normal physiology as well as pathophysiology in various tissues and organs, including the pancreas. This review article summarizes current progress that has been made in elucidating the putative roles of Ang II in both acute and chronic pancreatitis.

RECENT ADVANCES

A convergence of evidence suggests that the underlying mechanism may involve reactive oxygen species (ROS)-generating systems, such as nicotinamide adenine dinucleotide phosphate oxidase, and subsequent elevation of proinflammatory and profibrogenic gene expression as well as protein activity. More importantly, Ang II-induced ROS interacts with other ROS-generating systems to positively feed-forward the ROS-induced signaling.

CRITICAL ISSUES AND FUTURE DIRECTIONS

Advances in basic research indicate that RAS blockers may provide potential therapeutic role for the management of pancreatic inflammation and, more importantly, pancreatitis-associated complications. Genetic alterations resulting from a malfunction in the epigenetic control of pancreatic RAS could be a causative factor in the development of pancreatitis.

Transcriptomes of the major human pancreatic cell types

AIMS/HYPOTHESIS

We sought to determine the mRNA transcriptome of all major human pancreatic endocrine and exocrine cell subtypes, including human alpha, beta, duct and acinar cells. In addition, we identified the cell type-specific distribution of transcription factors, signalling ligands and their receptors.

METHODS

Islet samples from healthy human donors were enzymatically dispersed to single cells and labelled with cell type-specific surface-reactive antibodies. Live endocrine and exocrine cell subpopulations were isolated by FACS and gene expression analyses were performed using microarray analysis and quantitative RT-PCR. Computational tools were used to evaluate receptor-ligand representation in these populations.

RESULTS

Analysis of the transcriptomes of alpha, beta, large duct, small duct and acinar cells revealed previously unrecognised gene expression patterns in these cell types, including transcriptional regulators HOPX and HDAC9 in the human beta cell population. The abundance of some regulatory proteins was different from that reported in mouse tissue. For example, v-maf musculoaponeurotic fibrosarcoma oncogene homologue B (avian) (MAFB) was detected at equal levels in adult human alpha and beta cells, but is absent from adult mouse beta cells. Analysis of ligand-receptor interactions suggested that EPH receptor-ephrin communication between exocrine and endocrine cells contributes to pancreatic function.

CONCLUSIONS/INTERPRETATION

This is the first comprehensive analysis of the transcriptomes of human exocrine and endocrine pancreatic cell types-including beta cells-and provides a useful resource for diabetes research. In addition, paracrine signalling pathways within the pancreas are shown. These results will help guide efforts to specify human beta cell fate by embryonic stem cell or induced pluripotent stem cell differentiation or genetic reprogramming.

Expression and localization of paxillin in rat pancreas during development

AIM: To investigate the expression and localization of paxillin in rat pancreas during development.

METHODS: Pancreata from Sprague Dawley rat fetuses, embryos, young animals, and adult animals were used in this study. Expression levels of paxillin in pancreata of different development stages were detected by reverse transcription polymerase chain reaction and Western blotting. To identify the cell location of paxillin in the developing rat pancreas, immunohistochemistry and double-immunofluorescent staining were performed using antibodies for specific cell markers and paxillin, respectively.

RESULTS: The highest paxillin mRNA level was detected at E15.5 (embryo day 15.5) following a decrease in the later developmental periods (P < 0.05 vs E18.5, P0 and adult, respectively), and a progressively increased paxillin protein expression through the transition from E15.5 to adult was detected. The paxillin positive staining was mainly localized in rat islets of Langerhans at each stage tested during pancreas development.

CONCLUSION: The dynamic expression of paxillin in rat pancreas from different stages indicates that paxillin might be involved in some aspects of pancreatic development.

A novel explant outgrowth culture model for mouse pancreatic acinar cells with long-term maintenance of secretory phenotype

The development of in vitro models able to support the long-term viability and function of acinar cells is critical for exploring pancreatic pathophysiology. Despite considerable efforts, no long-term culture models for non-transformed pancreatic acini exist. Our aim was to develop and validate culture conditions for this purpose. An explant outgrowth culture design was established in which mouse pancreatic explants were cultured at the gas-liquid interphase. An enriched culture medium, pH 7.8, was employed to promote the selective outgrowth of acinar cells and to support their differentiated phenotype. After 7 days, the outgrown primary acinar cells were subcultured and maintained up to an additional 7 days as secondary monolayers on tissue culture plastic. Measurements of basal and caerulein-induced amylase secretion, phase-contrast microscopy and immunohistochemical analyses were used to characterize the cultures. Explants retained their pancreatic cytoarchitecture for 2 days in vitro. A triphasic dose response to caerulein was detected in 7-day primary cultures. The maximal rate of secretion was 1.2-fold versus basal (p=0.009) and 1.7-fold versus 1 pM caerulein (p=0.014). In secondary cultures the response was biphasic with maximal rates of secretion being 1.9-fold in 3- to 4-day cultures at 0.01 nM (p=0.049) and 2-fold in 6- to 7-day cultures at 0.1 nM (p=0.003). The present culture model provides a means to obtain functionally competent normal mouse acinar cells for long-term in vitro experimentation.

Insulin receptor-related receptor as an extracellular alkali sensor

The insulin receptor-related receptor (IRR), an orphan receptor tyrosine kinase of the insulin receptor family, can be activated by alkaline media both in vitro and in vivo at pH >7.9. The alkali-sensing property of IRR is conserved in frog, mouse, and human. IRR activation is specific, dose-dependent and quickly reversible and demonstrates positive cooperativity. It also triggers receptor conformational changes and elicits intracellular signaling. The pH sensitivity of IRR is primarily defined by its L1F extracellular domains. IRR is predominantly expressed in organs that come in contact with mildly alkaline media. In particular, IRR is expressed in the cell subsets of the kidney that secrete bicarbonate into urine. Disruption of IRR in mice impairs the renal response to alkali loading attested by development of metabolic alkalosis and decreased urinary bicarbonate excretion in response to this challenge. We therefore postulate that IRR is an alkali sensor that functions in the kidney to manage metabolic bicarbonate excess.

Visualization of mouse pancreas architecture using MR microscopy

Pancreatic diseases, which include diabetes, pancreatitis, and pancreatic cancer, are often difficult to detect and/or stage, contributing to a reduced quality of life and lifespan for patients. Thus, there is need for a technology that can visualize tissue changes in the pancreas, improve understanding of disease progression, and facilitate earlier detection in the human population. Because of low spatial resolution, current clinical magnetic resonance imaging (MRI) at low field strength has yet to fully visualize the exocrine, endocrine, vascular, and stromal components of the pancreas. We used high field strength magnetic resonance microscopy (μMRI) to image mouse pancreas ex vivo without contrast agents at high spatial resolution. We analyzed the resulting high-resolution images using volume rendering to resolve components in the pancreas, including acini, islets, blood vessels, and extracellular matrix. Locations and dimensions of pancreatic components as seen in three-dimensional μMRI were compared with histological images, and good correspondence was found. Future longitudinal studies could expand on the use of in vivo μMRI in mouse models of pancreatic diseases. Capturing three-dimensional structural changes through μMRI could help to identify early cellular and tissue changes associated with pancreatic disease, serving as a mode of improved detection in the clinic for endocrine and exocrine pathologies.

Transthyretin, identified by proteomics, is overabundant in pancreatic juice from pancreatic carcinoma and originates from pancreatic islets

Analyses of pancreatic juice by proteomics have identified many proteins that are overabundant in pancreatic cancer (PC) juice. The mechanism by which secretion of these proteins occur remains unclear. Pancreatic juice was collected from patients with three pancreatic diseases: PC, chronic pancreatitis (CP), and simple choledocholithiasis (CDS), and analyzed by 2-DE, MALDI-TOF/MS, and Western blot. Five PC cell lines, 30 PC tissues and their corresponding adjacent pancreatic tissues were used to validate the expression of genes which code for overabundant proteins in PC juice. The mRNA and protein levels were measured by RT-PCR and immunohistochemistry, respectively. Using proteomics, it was demonstrated that the protein transthyretin (TTR) was upregulated more than 2-fold in PC juice compared with CP and CDS, while apolipoprotein A-I, lithostathine, and regenerating islet-derived 1 beta precursor were downregulated more than 2-fold. Western blots confirmed that TTR was overabundant in the PC juice. However, TTR mRNA was not detected in any of the five PC cell lines, and was only detected in islet cells. By microscopy, it was shown that islet architecture was almost completely destroyed, and the islet's maximum diameter appeared larger in PC tissues than in normal. Some overabundant proteins in PC juice, such as TTR expressed only in islets, leak into the pancreatic ductal system due to hyperplasia and architectural damage in PC tissues. The destruction of organ and tissue architecture by tumor growth may result in novel tumor markers even if the markers are not secreted directly by tumor cells.

Neurogenin 3 and neurogenic differentiation 1 are retained in the cytoplasm of multiple endocrine neoplasia type 1 islet and pancreatic endocrine tumor cells

OBJECTIVES

To investigate if transcription factors involved in pancreatic differentiation and regeneration are present in pancreatic endocrine tumors and if they are differentially expressed in normal pancreas compared with multiple endocrine neoplasia type 1 (MEN1) nontumorous pancreas.

METHODS

The expression of neurogenin 3 (NEUROG3), neurogenic differentiation 1 (NEUROD1), POU class 3 homeobox 4 (POU3F4), pancreatic duodenal homeobox factor 1 (PDX1), ribosomal protein L10 (RPL10), delta-like 1 homolog (Drosophila; DLK1), and menin was analyzed by immunohistochemistry in normal pancreas and pancreatic endocrine tumors from 6 patients with MEN1 and 16 patients with sporadic tumors, as well as pancreatic specimens from Men1 heterozygous and wild type mice. Quantitative polymerase chain reaction was performed in a subset of human tumors.

RESULTS

Tumors and MEN1 nontumorous endocrine cells showed a prominent cytoplasmatic NEUROG3 and NEUROD1 expression. These factors were significantly more expressed in the cytoplasm of Men1 heterozygous mouse islet cells compared with wild type islets; the latter showed an exclusively nuclear reactivity. The degree of Pou3f4, Rpl10, and Dlk1 immunoreactivities differed significantly between islets of heterozygous and wild type mice. The expressions of RPL10 and NEUROD1 were prominent in the MEN1 human and heterozygous mouse exocrine pancreas. Insulinomas had significantly higher PDX1 and DLK1 messenger RNA levels compared with other tumor types.

CONCLUSIONS

Transcription factors involved in pancreatic development show altered expression and subcellular localization in MEN1 nontumorous pancreas and pancreatic endocrine tumors.

Attenuation of endocrine-exocrine pancreatic communication in type 2 diabetes: pancreatic extracellular matrix ultrastructural abnormalities

Ultrastructural observations reveal a continuous interstitial matrix connection between the endocrine and exocrine pancreas, which is lost due to fibrosis in rodent models and humans with type 2 diabetes mellitus (T2DM). Widening of the islet-exocrine interface appears to result in loss of desmosomes and adherens junctions between islet and acinar cells and is associated with hypercellularity consisting of pericytes and inflammatory cells in T2DM pancreatic tissue. Organized fibrillar collagen was closely associated with pericytes, which are known to differentiate into myofibroblasts-pancreatic stellate cells. Of importance, some pericyte cellular processes traverse both the connecting islet-exocrine interface and the endoacinar interstitium of the exocrine pancreas. Loss of cellular paracrine communication and extracellular matrix remodeling fibrosis in young animal models and humans may result in a dysfunctional insulino-acinar-ductal-incretin gut hormone axis, resulting in pancreatic insufficiency and glucagon-like peptide deficiency, which are known to exist in prediabetes and overt T2DM in humans.

Sustained insulin secretory response in human islets co-cultured with pancreatic duct-derived epithelial cells within a rotational cell culture system

AIMS/HYPOTHESIS

Loss of the trophic support provided by surrounding non-endocrine pancreatic cell populations underlies the decline in beta cell mass and insulin secretory function observed in human islets following isolation and culture. This study sought to determine whether restoration of regulatory influences mediated by ductal epithelial cells promotes sustained beta cell function in vitro.

METHODS

Human islets were isolated according to existing protocols. Ductal epithelial cells were harvested from the exocrine tissue remaining after islet isolation, expanded in monolayer culture and characterised using fluorescence immunocytochemistry. The two cell types were co-cultured under conventional static culture conditions or within a rotational cell culture system. The effect of co-culture on islet structural integrity, beta cell mass and insulin secretory capacity was observed for 10 days following isolation.

RESULTS

Human islets maintained under conventional culture conditions exhibited a characteristic loss in structural integrity and functional viability as indicated by a diminution of glucose responsiveness. By contrast, co-culture of islets with ductal epithelial cells led to preserved islet morphology and sustained beta cell function, most evident in co-cultures held within the rotational cell culture system, which showed a significantly (p < 0.05) greater insulin secretory response to elevated glucose compared with control islets. Similarly, insulin/protein ratio data suggested that the presence of ductal epithelial cells is beneficial for the maintenance of beta cell mass.

CONCLUSIONS/INTERPRETATION

The data indicate a supportive role for ductal epithelial cells in islet viability. Further characterisation of the regulatory influences may lead to novel strategies to improve long-term beta cell function both in vitro and following islet transplantation.

Topographical associations between islet endocrine cells and duct epithelial cells in the adult human pancreas

OBJECTIVES

The pancreatic ducts, endocrine islets and exocrine acini are three functionally related components. From birth to adulthood, the islets and ducts are regarded as independent entities. The objective of this study is to investigate the topographical associations between the islet endocrine cells and duct epithelial cells in the adult human pancreas.

MATERIALS AND METHODS

Panels of immunomarkers for the exocrine acinar cells (amylase), duct cells [cytokeratin 19 (CK19)], endocrine cells (chromogranin A, neurone specific enolase, synaptophysin) and islet hormones (glucagon, insulin, somatostatin, pancreatic polypeptide) were applied to sequential pancreatic tissue sections obtained from autopsy specimens of 10-nondiabetic human adults. Double immunofluorescent staining with CK19 and islet hormones was performed to confirm the islet to duct interrelationship.

RESULTS

Sequential sectioning and immunostaining showed that 45% of the 172 islets examined appeared as single endocrine cell units or small clusters of < 10 endocrine cells on at least one plane of section. A topographical association was found between the islet endocrine cells and duct epithelial cells. Topographical associations with CK 19-stained duct cells occurred in 10.9% of the islet insulin-containing beta-cells and in 8.9% of the islet glucagon-producing alpha-cells. The frequency of topographical associations increased toward the more distally located duct systems. The CK19-stained duct cells and amylase-labelled acinar cells were less frequently in association with other islet hormone-producing cells.

CONCLUSIONS

Topographical associations between islet endocrine cells and pancreatic duct cells are frequent in adult human pancreas. The islet-duct association suggests possible functional interactions between the two interrelated pancreatic compartments.

Ultrastructure of islet microcirculation, pericytes and the islet exocrine interface in the HIP rat model of diabetes

CONTEXT

The transgenic human islet amyloid polypeptide (HIP) rat model of type 2 diabetes mellitus (T2DM) parallels the functional and structural changes in human islets with T2DM.

OBJECTIVE

The transmission electron microscope (TEM) was utilized to observe the ultrastructural changes in islet microcirculation.

METHODS

Pancreatic tissue from male Sprague Dawley rats (2, 4, 8, 14 months) were used as controls (SDC) and compared to the 2-, 4-, 8- and 14-month-old HIP rat models.

RESULTS

The 2-month-old HIP model demonstrated no islet or microcirculation remodeling changes when compared to the SDC models. The 4-month-old HIP model demonstrated significant pericapillary amyloid deposition and diminution of pericyte foot processes as compared to the SDC models. The 8-month-old model demonstrated extensive islet amyloid deposition associated with pericyte and beta-cell apoptosis when compared with SDC. The 14-month-old HIP model demonstrated a marked reduction of beta-cells and intra-islet capillaries with near complete replacement of islets by amyloidoses. Increased cellularity in the region of the islet exocrine interface was noted in the 4- to 14-month-old HIP models as compared to SDC. In contrast to intra-islet capillary rarefaction there was noticeable angiogenesis in the islet exocrine interface. Pericytes seemed to be closely associated with collagenosis, intra-islet adipogenesis and angiogenesis in the islet exocrine interface.

CONCLUSION

The above novel findings regarding the microcirculation and pericytes could assist researchers and clinicians in a better morphological understanding of T2DM and lead to new strategies for prevention and treatment of T2DM.

Purinergic receptors in the endocrine and exocrine pancreas

The pancreas is a complex gland performing both endocrine and exocrine functions. In recent years there has been increasing evidence that both endocrine and exocrine cells possess purinergic receptors, which influence processes such as insulin secretion and epithelial ion transport. Most commonly, these processes have been viewed separately. In beta cells, stimulation of P2Y(1) receptors amplifies secretion of insulin in the presence of glucose. Nucleotides released from secretory granules could also contribute to autocrine/paracrine regulation in pancreatic islets. In addition to P2Y(1) receptors, there is also evidence for other P2 and adenosine receptors in beta cells (P2Y(2), P2Y(4), P2Y(6), P2X subtypes and A(1) receptors) and in glucagon-secreting alpha cells (P2X(7), A(2) receptors). In the exocrine pancreas, acini release ATP and ATP-hydrolysing and ATP-generating enzymes. P2 receptors are prominent in pancreatic ducts, and several studies indicate that P2Y(2), P2Y(4), P2Y(11), P2X(4) and P2X(7) receptors could regulate secretion, primarily by affecting Cl(-) and K(+) channels and intracellular Ca(2+) signalling. In order to understand the physiology of the whole organ, it is necessary to consider the full complement of purinergic receptors on different cells as well as the structural and functional relation between various cells within the whole organ. In addition to the possible physiological function of purinergic receptors, this review analyses whether the receptors could be potential therapeutic targets for drug design aimed at treatment of pancreatic diseases.

Isletopathy in Type 2 diabetes mellitus: implications of islet RAS, islet fibrosis, islet amyloid, remodeling, and oxidative stress

This review focuses primarily on islet structural and functional changes related to an activated islet renin- angiotensin system (RAS), islet oxidative-redox imbalance, the concurrence of islet fibrosis (pericapillary, intra- and peri-islet), and islet amyloid deposition (pericapillary, intra- and peri-islet). The islet-acinar-portal vascular pathway and the emerging important anatomical and functional region, the islet-exocrine interface, are also discussed. Because there is an associated histopathological islet disease in type 2 diabetes mellitus (T2DM), the term isletopathy is discussed in detail. The isletopathy in T2DM is equally important as the other complications of diabetes. Special stains and special lighting (bright field and crossed polarized light) are utilized, along with light and transmission electron microscopy, in order to better understand islet structural remodeling in T2DM. The importance of an isletopathy in T2DM is supported by numerous remodeling changes within the islet and the islet-exocrine interface. While some of the structural findings are only preliminary observations, additional investigation in this area should lead to the development of new pathophysiological concepts and new therapies regarding the prevention and treatment of T2DM.

Nestin expression in adult and developing human kidney

Nestin is considered a marker of neurogenic and myogenic precursor cells. Its arrangement is regulated by cyclin-dependent kinase 5 (CDK5), which is expressed in murine podocytes. We investigated nestin expression in human adult and fetal kidney as well as CDK5 presence in adult human podocytes. Confocal microscopy demonstrated that adult glomeruli display nestin immunoreactivity in vimentin-expressing cells with the podocyte morphology and not in cells bearing the endothelial marker CD31. Glomerular nestin-positive cells were CDK5 immunoreactive as well. Western blotting of the intermediate filament-enriched cytoskeletal fraction and coimmunoprecipitation of nestin with anti-CDK5 antibodies confirmed these results. Nestin was also detected in developing glomeruli within immature podocytes and a few other cells. Confocal microscopy of experiments conducted with antibodies against nestin and endothelial markers demonstrated that endothelial cells belonging to capillaries invading the lower cleft of S-shaped bodies and the immature glomeruli were nestin immunoreactive. Similar experiments carried out with antibodies raised against nestin and alpha-smooth muscle actin showed that the first mesangial cells that populate the developing glomeruli expressed nestin. In conclusion, nestin is expressed in the human kidney from the first steps of glomerulogenesis within podocytes, mesangial, and endothelial cells. This expression, restricted to podocytes in mature glomeruli, appears associated with CDK5.