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

Pancreatic enzymes digest obstructive meconium from cystic fibrosis pig intestines

Introduction

Meconium ileus (MI) is a life-threatening obstruction of the intestines affecting ∼15% of newborns with cystic fibrosis (CF). Current medical treatments for MI often fail, requiring surgical intervention. MI typically occurs in newborns with pancreatic insufficiency from CF. Meconium contains mucin glycoprotein, a potential substrate for pancreatic enzymes or mucolytics. Our study aim was to determine whether pancreatic enzymes in combination with mucolytic treatments dissolve obstructive meconium using the CF pig model.

Methods

We collected meconium from CF pigs at birth and submerged it in solutions with and without pancreatic enzymes, including normal saline, 7% hypertonic saline, and the reducing agents N-acetylcysteine (NAC) and dithiothreitol (DTT). We digested meconium at 37 °C with agitation, and measured meconium pigment release by spectrophotometry and residual meconium solids by filtration.

Results and discussion

In CF pigs, meconium appeared as a solid pigmented mass obstructing the ileum. Meconium microscopically contained mucus glycoprotein, cellular debris, and bile pigments. Meconium fragments released pigments with maximal absorption at 405 nm after submersion in saline over approximately 8 h. Pancreatic enzymes significantly increased pigment release and decreased residual meconium solids. DTT did not improve meconium digestion and the acidic reducing agent NAC worsened digestion. Pancreatic enzymes digested CF meconium best at neutral pH in isotonic saline. We conclude that pancreatic enzymes digest obstructive meconium from CF pigs, while hydrating or reducing agents alone were less effective. This work suggests a potential role for pancreatic enzymes in relieving obstruction due to MI in newborns with CF.

ALKBH5 suppresses autophagic flux via N6-methyladenosine demethylation of ZKSCAN3 mRNA in acute pancreatitis

BACKGROUND

Increasing evidence has demonstrated that N6-methyladenosine (m6A) RNA modification plays an essential role in a wide range of pathological conditions. Impaired autophagy is a critical hallmark of acute pancreatitis (AP).

AIM

To explore the role of the m6A modification of ZKSCAN3 in the regulation of autophagy in AP.

METHODS

The AP mouse cell model was established by cerulein-treated mouse pancreatic acinar cells (MPC-83), and the results were confirmed by the levels of amylase and inflammatory factors. Autophagy activity was evaluated by specific identification of the autophagy-related microstructure and the expression of autophagy-related genes. ZKSCAN3 and ALKBH5 were knocked down to study the function in AP. A m6A RNA binding protein immunoprecipitation assay was used to study how the m6A modification of ZKSCAN3 mRNA is regulated by ALKBH.

RESULTS

The increased expression of amylase and inflammatory factors in the supernatant and the accumulation of autophagic vacuoles verified that the AP mouse cell model was established. The downregulation of LAMP2 and upregulation of LC3-II/I and SQSTM1 demonstrated that autophagy was impaired in AP. The expression of ZKSCAN3 was upregulated in AP. Inhibition of ZKSCAN3 increased the expression of LAMP2 and decreased the expression of the inflammatory factors, LC3-II/I and SQSTM1. Furthermore, ALKBH5 was upregulated in AP. Knockdown of ALKBH5 downregulated ZKSCAN3 expression and restored decreased autophagic flux in AP. Notably, the bioinformatic analysis revealed 23 potential m6A modification sites on ZKSCAN3 mRNA. The m6A modification of ZKSCAN3 mRNA was significantly decreased in AP. Knockdown of ALKBH5 increased the modification of ZKSCAN3 mRNA, which confirmed that ALKBH5 upregulated ZKSCAN3 expression in a m6A-dependent manner.

CONCLUSION

ALKBH5 inhibits autophagic flux through m6A demethylation of ZKSCAN3 mRNA in AP, thereby aggravating the severity of the disease.

Innovative Experimental Ultrasound and US-Related Techniques Using the Murine Model in Pancreatic Ductal Adenocarcinoma: A Systematic Review

Pancreatic ductal adenocarcinoma (PDAC) is a cancer with one of the highest mortality rates in the world. Several studies have been conductedusing preclinical experiments in mice to find new therapeutic strategies. Experimental ultrasound, in expert hands, is a safe, multifaceted, and relatively not-expensive device that helps researchers in several ways. In this systematic review, we propose a summary of the applications of ultrasonography in a preclinical mouse model of PDAC. Eighty-eight studies met our inclusion criteria. The included studies could be divided into seven main topics: ultrasound in pancreatic cancer diagnosis and progression (n: 21); dynamic contrast-enhanced ultrasound (DCE-US) (n: 5); microbubble ultra-sound-mediated drug delivery; focused ultrasound (n: 23); sonodynamic therapy (SDT) (n: 7); harmonic motion elastography (HME) and shear wave elastography (SWE) (n: 6); ultrasound-guided procedures (n: 9). In six cases, the articles fit into two or more sections. In conclusion, ultrasound can be a really useful, eclectic, and ductile tool in different diagnostic areas, not only regarding diagnosis but also in therapy, pharmacological and interventional treatment, and follow-up. All these multiple possibilities of use certainly represent a good starting point for the effective and wide use of murine ultrasonography in the study and comprehensive evaluation of pancreatic cancer.

Modeling type 2 diabetes in rats by administering tacrolimus

The prevalence of diabetes is rapidly increasing. The current number of diagnosed cases is ~422 million, expected to reach ~640 million by 2040. Type 2 diabetes, which constitutes ~95% of the cases, is characterized by insulin resistance and a progressive loss of β-cell function. Despite intense research efforts, no treatments are yet able to cure the disease or halt its progression. Since all existing animal models of type 2 diabetes have serious drawbacks, one is needed that represents the complete pathogenesis, is low cost and non-obese, and can be developed relatively quickly. The aim of this study was to evaluate a low-cost, non-obese model of type 2 diabetes engendered by administering a daily high dose of tacrolimus (an immunosuppressant) to Wistar rats for 4 weeks. The biochemical and antioxidant markers were measured at basal and after the 4-week tacrolimus treatment. At week 4, the values of these parameters closely resembled those observed in human type 2 diabetes, including fasting blood glucose at 141.5 mg/dL, blood glucose greater than 200 mg/dL at 120 min of the glucose tolerance test, blood glucose at varied levels in the insulin tolerance test, and elevated levels of cholesterol and triglyceride. The tacrolimus treatment produced hypoinsulinemia and sustained hyperglycemia, probably explained by the alteration found in pancreatic β-cell function and morphology. This model should certainly be instrumental for evaluating possible type 2 diabetes treatments, and for designing new immunosuppressants that do not cause pancreatic damage, type 2 diabetes, or new-onset diabetes after transplantation (NODAT).

Hemorheological and Microcirculatory Relations of Acute Pancreatitis

Acute pancreatitis still means a serious challenge in clinical practice. Its pathomechanism is complex and has yet to be fully elucidated. Rheological properties of blood play an important role in tissue perfusion and show non-specific changes in acute pancreatitis. An increase in blood and plasma viscosity, impairment of red blood cell deformability, and enhanced red blood cell aggregation caused by metabolic, inflammatory, free radical-related changes and mechanical stress contribute to the deterioration of the blood flow in the large vessels and also in the microcirculation. Revealing the significance of these changes in acute pancreatitis may better explain the pathogenesis and optimize the therapy. In this review, we give an overview of the role of impaired microcirculation by changes in hemorheological properties in acute pancreatitis.

Hypertriglyceridemia Acute Pancreatitis: Animal Experiment Research

In recent years, the number of acute pancreatitis cases caused by hypertriglyceridemia has increased gradually, which has caught the attention of the medical community. However, because the exact mechanism of hypertriglyceridemic acute pancreatitis (HTG-AP) is not clear, treatment and prevention in clinical practice face enormous challenges. Animal models are useful for elucidating the pathogenesis of diseases and developing and testing novel interventions. Therefore, animal experiments have become the key research means for us to understand and treat this disease. We searched almost all HTG-AP animal models by collecting many studies and finally collated common animals such as rats, mice and included some rare animals that are not commonly used, summarizing the methods to model spontaneous pancreatitis and induce pancreatitis. We sorted them on the basis of three aspects, including the selection of different animals, analyzed the characteristics of different animals, different approaches to establish hypertriglyceridemic pancreatitis and their relative advantages and disadvantages, and introduced the applications of these models in studies of pathogenesis and drug therapy. We hope this review can provide relevant comparisons and analyses for researchers who intend to carry out animal experiments and will help researchers to select and establish more suitable animal experimental models according to their own experimental design.

Laparoscopic Pancreatectomy in Rats: The Development of an Experimental Model

INTRODUCTION

several pancreatectomy techniques in rats have been described and utilized for research concerning the pancreas endocrine and exocrine functions. However, we did not find a description of any kind of laparoscopic pancreatectomy in rats in the consulted databases. The objective of this study is to describe a laparoscopic splenic lobe pancreatectomy in rats.

METHODS

ten Wistars rats weighting more then 300 g were operated for standardizing the laparoscopic pancreatosplenectomy technique, aided by previous descriptions of laparoscopic splenectomy and open pancreatectomy in rats. Adjustments have been progressively adopted for technical refinement.

RESULTS

In five animals a low-cost rat laparoscopic set was used. In other five animals we used a standard laparoscopic set. Three rats died early due to different causes: transection of the gastroesophageal junction, hemorrhagic shock and inadvertent colonic injury. The postoperative period of the other seven rats was uneventful until the seventh postoperative day.

DISCUSSION

laparoscopic distal pancreatectomy and splenectomy in rats is feasible and safe, even with a low-cost set, in which the results were alike the standard laparoscopic set.

Translating complexity and heterogeneity of pancreatic tumor: 3D in vitro to in vivo models

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive type of cancer with an overall survival rate of less than 7-8%, emphasizing the need for novel effective therapeutics against PDAC. However only a fraction of therapeutics which seemed promising in the laboratory environment will eventually reach the clinic. One of the main reasons behind this low success rate is the complex tumor microenvironment (TME) of PDAC, a highly fibrotic and dense stroma surrounding tumor cells, which supports tumor progression as well as increases the resistance against the treatment. In particular, the growing understanding of the PDAC TME points out a different challenge in the development of efficient therapeutics - a lack of biologically relevant in vitro and in vivo models that resemble the complexity and heterogeneity of PDAC observed in patients. The purpose and scope of this review is to provide an overview of the recent developments in different in vitro and in vivo models, which aim to recapitulate the complexity of PDAC in a laboratory environment, as well to describe how 3D in vitro models can be integrated into drug development pipelines that are already including sophisticated in vivo models. Hereby a special focus will be given on the complexity of in vivo models and the challenges in vitro models face to reach the same levels of complexity in a controllable manner. First, a brief introduction of novel developments in two dimensional (2D) models and ex vivo models is provided. Next, recent developments in three dimensional (3D) in vitro models are described ranging from spheroids, organoids, scaffold models, bioprinted models to organ-on-chip models including a discussion on advantages and limitations for each model. Furthermore, we will provide a detailed overview on the current PDAC in vivo models including chemically-induced models, syngeneic and xenogeneic models, highlighting hetero- and orthotopic, patient-derived tissues (PDX) models, and genetically engineered mouse models. Finally, we will provide a discussion on overall limitations of both, in vitro and in vivo models, and discuss necessary steps to overcome these limitations to reach an efficient drug development pipeline, as well as discuss possibilities to include novel in silico models in the process.

Profiles of Two Glycaemia Modifying Drugs on the Expression of Rat and Human Sulfotransferases

AIMS

To study the effects of blood glucose regulating compounds on human and rat sulfotransferases (SULTs) expressions.

BACKGROUND

Phase-II enzymes, sulfotransferases catalyze the sulfuryl-group-transfer to endogenous/exogenous compounds. The alteration of expressions of SULTs may have influence on the sulfation of its substrate and other biomolecules.

OBJECTIVES

The influence of the altered biotransformation might alter different biochemical events, drug-drug interactions and bioaccumulation or excretion pattern of certain drug.

METHODS

In this brief study, diabetes-inducing drug streptozotocin (STZ; 10 or 50 mg/kg to male Sprague Dawley rat for 2 weeks) or hyperglycemia controlling drug tolbutamide (TLB 0.1 or 10μM to human hepato-carcinoma cells, HepG2 for 10 days) was applied and the SULTs expressions were verified. Extensive protein-protein (STa, SULT2A1/DHEAST) interactions were studied by the STRING (Search-Tool-for-the-Retrieval-of-Interacting Genes/Proteins) Bioinformatics-software.

RESULTS

Present result suggests that while STZ increased the STa (in rat) (dehydroepiandrosterone catalyzing SULT; DHEAST in human HepG2), tolbutamide decreased PPST (phenol catalyzing SULT) and DHEAST activity in human HepG2 cells. Moderate decreases of MPST (monoamine catalyzing SULT) and EST (estrogen catalyzing) activities are noticed in this case. STa/DHEAST was found to be highly interactive to SHBG/- sex-hormone-binding-globulin; PPARα/lipid-metabolism-regulator; FABP1/fatty-acid-binding-protein.

CONCLUSION

Streptozotocin and tolbutamide, these two glycaemia-modifying drugs demonstrated regulation of rat and human SULTs activities. The reciprocal nature of these two drugs on SULTs expression may be associated with their contrasting abilities in influencing glucose-homeostasis. Possible association of certain SULT-isoform with hepatic fat-regulations may indicate an unfocused link between calorie-metabolism and the glycemic-state of an individual. Explorations of this work may uncover the role of sulfation metabolism of specific biomolecule on cellular glycemic regulation.

Animal Models: Challenges and Opportunities to Determine Optimal Experimental Models of Pancreatitis and Pancreatic Cancer

At the 2018 PancreasFest meeting, experts participating in basic research met to discuss the plethora of available animal models for studying exocrine pancreatic disease. In particular, the discussion focused on the challenges currently facing the field and potential solutions. That meeting culminated in this review, which describes the advantages and limitations of both common and infrequently used models of exocrine pancreatic disease, namely, pancreatitis and exocrine pancreatic cancer. The objective is to provide a comprehensive description of the available models but also to provide investigators with guidance in the application of these models to investigate both environmental and genetic contributions to exocrine pancreatic disease. The content covers both nongenic and genetically engineered models across multiple species (large and small). Recommendations for choosing the appropriate model as well as how to conduct and present results are provided.

Morfologia do pâncreas da paca (Cuniculus paca, Linnaeus, 1766)

RESUMO Este trabalho se baseou na descrição morfológica da paca (Cuniculus paca), espécie selvagem pertencente à ordem dos roedores, típica de regiões tropicais, sendo o seu conhecimento anatômico detalhado muito importante para sua conservação, experimentação e comercialização, pois ainda são escassos na literatura os trabalhos sobre morfologia de espécies selvagens. Macroscopicamente, o pâncreas da paca é formado por lóbulos, organizados em ramificações difusas, e, microscopicamente, tal órgão possui uma camada de tecido conjuntivo frouxo, a partir da qual partem septos, que dividem a glândula em lóbulos, compostos de ácinos e ilhotas pancreáticas.

Genetically induced vs. classical animal models of chronic pancreatitis: a critical comparison

Chronic pancreatitis (CP) is an utmost complex disease that is pathogenetically linked to pancreas-intrinsic ( e.g., duct obstruction), environmental-toxic ( e.g., alcohol, smoking), and genetic factors. Studying such a complex disease naturally requires validated experimental models. In the past 2 decades, the various animal models of CP usually addressed either the pancreas-intrinsic ( e.g., the caerulein model), the environmental-toxic ( e.g., diet-induced models), or the genetic component of CP. As such, these models were far from mirroring CP in its full spectrum, and the correct choice of models was vital for valid scientific conclusions on CP. The quest for mechanistic, genetic models gave rise to models based on gene modification and transgene insertion, such as the PRSS1 and the IL-1β/IL-1β models. Recently, we witnessed the development of highly exciting models that rely on the importance of autophagy in CP, that is, the murine pancreas-specific Atg5 and LAMP2 knockout models. Today, critical comparison of these several models is more important than ever for guiding research on CP in an efficient direction. The present review outlines the characteristics of the new genetic models in comparison with the well-known classic models for CP, notes the caveats in the choice of models, and also indicates novel directions for model development.-Klauss, S., Schorn, S., Teller, S., Steenfadt, H., Friess, H., Ceyhan, G. O., Demir, I. K. Genetically induced vs. classical animal models of chronic pancreatitis: a critical comparison.

A novel acute necrotizing pancreatitis model induced by L-arginine in rats

OBJECTIVE

This study developed a novel protocol for creating an acute necrotizing pancreatitis model in rats using L-arginine.

METHODS

Anesthetic laparotomy was performed on the upper abdomen, and the pancreatic parenchyma of Sprague-Dawley rats was injected with 1 mL of sterilized L-arginine solution at 5 different locations in the experimental group. Specifically, 2 different injection points in the head and body of the pancreas were chosen randomly, and 1 injection point in the tail of the pancreas was chosen randomly. The parenchyma of the pancreas was injected with 200 μL of an L-arginine solution at each point. The optimal dose of L-arginine per rat was 0.4 g/kg.

RESULTS

Serum amylase activity increased significantly after targeted injection into the parenchyma of the pancreas. Pathological examination of the pancreas 24 hours after L-arginine injection revealed massive interstitial edema, apoptosis, and necrosis of acinar cells with an infiltration of neutrophils, granulocytes, and monocytes.

CONCLUSIONS

The present study developed an appropriate, workable, and reproducible rat model of acute necrotizing pancreatitis with higher survivability and success rates compared with previously published methods.

Structural similarities and differences between the human and the mouse pancreas

Mice remain the most studied animal model in pancreas research. Since the findings of this research are typically extrapolated to humans, it is important to understand both similarities and differences between the 2 species. Beside the apparent difference in size and macroscopic organization of the organ in the 2 species, there are a number of less evident and only recently described differences in organization of the acinar and ductal exocrine tissue, as well as in the distribution, composition, and architecture of the endocrine islets of Langerhans. Furthermore, the differences in arterial, venous, and lymphatic vessels, as well as innervation are potentially important. In this article, the structure of the human and the mouse pancreas, together with the similarities and differences between them are reviewed in detail in the light of conceivable repercussions for basic research and clinical application.

Ebselen reduces hyperglycemia temporarily-induced by diazinon: a compound with insulin-mimetic properties

The present study investigated the effect of ebselen (EB) against hyperglycemia induced by the organophosphate (OPI) diazinon (DI) in rats. The insulin-mimetic properties of EB were investigated in vitro with the aim of better understanding the hypoglycemic effect of this compound. The protective effect of EB against pancreatic and hepatic damage caused by DI in rats was also appraised. In the in vivo experiments, rats were pre-treated with a single injection of EB (50mg/kg, intraperitoneal, i.p.). Afterward, animals were treated with a single injection of DI (200 mg/kg, i.p.). The parameters indicative of pancreatic and hepatic damage such as, serum amylase, lipase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) activities as well as serum glucose levels, hepatic glycogen content and glucose-6-phosphatase (G6Pase) activity were determined. EB pre-treatment was effective in reducing serum amylase, lipase, AST, ALT, ALP, and LDH activities, protecting against pancreatic and hepatic damage. EB reduced hyperglycemia and increased hepatic glycogen content in animals exposed to DI. In the in vitro assays, EB (150 μM) or insulin (IN 10 μM, positive control) was incubated with either skeletal muscle or hepatic tissue with the aim of measuring glucose uptake, glycogen synthesis and glycogen breakdown. EB increased the glucose uptake in skeletal muscle, stimulated hepatic glycogen synthesis and inhibited glycogen breakdown in a similar way to IN. In conclusion, EB, possibly through its insulin-mimetic action, protected against pancreatic and hepatic damage caused by DI in rats.

Recombinant human activated protein C as a disease modifier in severe acute pancreatitis: systematic review of current evidence

BACKGROUND

The severity of organ failure caused by acute pancreatitis (AP) is the most important determinant of mortality in the disease. Recombinant human activated protein C (Drotrecogin Alfa; Xigris, APC, rhAPC) is the first drug to show a decrease in all-cause mortality due to multiple organ failure caused by sepsis. As the systemic inflammatory response syndrome (SIRS) that causes organ failure in early AP is similar to that caused by severe sepsis, the use of rhAPC in the management of AP has been investigated in experimental and clinical studies which are collated in this review.

METHODS

A literature review of published material identified from MEDLINE and EMBASE databases, for the period from January 1985 to January 2011, reporting rhAPC usage in AP.

RESULTS

3 of 4 experimental studies reported an improvement in outcome in animals with AP given rhAPC. The clinical randomized trial showed no improvement in outcome in the treatment arm.

CONCLUSION

The experimental evidence of disease amelioration in AP following intervention with rhAPC has not translated to the small clinical RCT. Given that there were only 16 patients in the treatment arm, further clinical evaluation is justified.

Bicarbonate transport by the human pancreatic ductal cell line HPAF

OBJECTIVES

The human pancreatic duct cell line, HPAF, has been shown previously to secrete Cl(-) in response to Ca(2+)-mobilizing stimuli. Our aim was to assess the capacity of HPAF cells to transport and secrete HCO3(-).

METHODS

HPAF cells were grown as confluent monolayers on permeable supports. Short-circuit current was measured by voltage clamp. Intracellular pH (pHi) was measured by microfluorometry in cells loaded with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF).

RESULTS

In HCO3(-)-free solutions, ATP-evoked changes in short-circuit current were inhibited by bumetanide, and the recovery of pHi from acid loading was abolished by 5-(N-ethyl-N-isopropyl)-amiloride (EIPA). In the presence of HCO3(-), ATP-evoked secretion was no longer inhibited by bumetanide, and there was a strong EIPA-insensitive recovery from acid loading, which was inhibited by 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonate (H2DIDS). ATP, but not forskolin, stimulated HCO3(-) efflux from the cells.

CONCLUSIONS

In the absence of HCO3(-), ATP-evoked Cl(-) secretion is driven by a basolateral Na(+)-K(+)-2Cl(-) cotransporter, and pH(i) is regulated by apical and basolateral Na(+)/H(+) exchangers. In the presence of HCO3(-), ATP-evoked secretion is sustained in the absence of Na(+)-K(+)-2Cl(-) cotransporter activity and is probably driven by basolateral Na(+)-HCO3(-) cotransport.

Development of a VX2 pancreatic cancer model in rabbits: a pilot study

PURPOSE

An animal model of pancreatic cancer that is large enough to permit imaging and catheterization would be desirable for interventional radiologists to develop novel therapies for pancreatic cancer. The purpose of this study was to test the hypothesis that the VX2 rabbit model of pancreatic cancer could be developed as a suitable platform to test future interventional therapies.

MATERIALS AND METHODS

The authors implanted and grew three pancreatic VX2 tumors per rabbit in six rabbits. Magnetic resonance (MR) imaging was performed at 2 weeks to confirm tumor growth. At 3 weeks, the authors selectively catheterized the gastroduodenal artery under guidance of x-ray digital subtraction angiography (DSA). T2-weighted anatomic imaging, diffusion-weighted MR imaging, and transcatheter intraarterial perfusion (TRIP) MR imaging were then performed. After imaging, tumors were confirmed at necropsy and histopathologically. Tumor sizes at 2 and 3 weeks were compared with a paired t test (P = .05).

RESULTS

VX2 pancreatic tumors were grown in all six rabbits. The difference between tumor sizes at 2 and 3 weeks (1.29 cm +/- 0.39 vs 1.91 cm +/- 0.50, respectively) was significant (P < .001). All tumors were confirmed to be located within pancreatic tissue via histopathologic analysis. DSA and TRIP MR imaging were successful in five rabbits. Diffusion-weighted and anatomic MR imaging were successful in all six rabbits.

CONCLUSIONS

The VX2 rabbit model of pancreatic cancer is feasible, as verified by imaging and pathologic correlation, and may be a suitable platform to test future interventional therapies.

Cellular localization of GDNF and its GFRalpha1/RET receptor complex in the developing pancreas of cat

Glial cell line-derived neurotrophic factor (GDNF) acts through RET receptor tyrosine kinase and its co-receptor GFRalpha1. In an effort to better understand the possible biological contribution of the GDNF and GFRalpha1/RET complex in pancreatic development, in this study we report the cellular localization of these proteins in the pancreas of domestic cat embryos and fetuses by immunocytochemical methods. In early embryos, GDNF, GFRalpha and RET immunoreactivity (IR) was localized in closely intermingled cells. GDNF and RET immunoreactive cells displayed chromogranin (an endocrine marker) and PGP 9.5 (a neuronal marker) IR, respectively. GFRalpha IR was present in both a few GDNF/chromogranin and RET/PGP 9.5 immunoreactive cells. In elderly fetuses, GDNF and GFRalpha IR were co-localized in glucagon cells and RET IR was detected in few neurons and never co-localized with GFRalpha or GDNF IR. In early embryos, the presence of GDNF IR in chromogranin immunoreactive cells and GFRalpha1/RET complex IR in PGP9.5 immunoreactive cells seems to suggest a paracrine action of GDNF contained in endocrine cell precursors on neuronal cell precursors expressing its receptor complex. The presence in different cell populations of RET and its co-receptor GFRalpha1 IR could be due to independent signaling of GRFalpha1. Thus, the co-presence of GDNF and GFRalpha1 in chromogranin and glucagon cells could lead to the hypothesis that GDNF can act in an autocrinal manner. In fetuses, RET IR was detected only in intrapancreatic ganglia. Because of the lack of GFRalpha1 IR in pancreatic innervation, RET receptor could be activated by other GFR alphas and ligands of GDNF family. In conclusion, these findings suggest that in differently aged embryos and fetuses the GDNF signal is differently mediated by RET and GFRalpha1.

Animal models in pancreatic surgery: a plea for pork

There has been resurgence in the utilization of larger animal models in medicine over the last decade, particularly in the field of pancreatic research. With increasing pressures to more accurately replicate the human model prior to clinical application, an ideal animal model is necessary. Previous work in larger species (dog, pig) in pancreatic surgery research has identified several key anatomical differences that have led us to conclude that perhaps the swine is a model better fit for more accurate human representation.

Pancreatic injury response is different depending on the method of resecting the parenchyma

OBJECTIVES

The present study was performed to compare the pancreatic injury response on the parenchymal resection either with ultrasonic scissors, electrocautery, or surgical scalpel.

METHODS

A 1 x 0.5 cm piece of rat pancreas was resected from side of the pancreas either with ultrasonic scissors (Harmonic Scalpel; UltraCision, Ethicon Endosurgery Inc., Cincinnati, OH) or electrocautery (Force FX; Valleylab, Tyco Healthcare Group LP, Boulder, CO) at two power levels, 1 and 3; 8W and 25W, respectively, or with surgical scalpel. Hemostasis was provided after surgical scalpel either with cellulose patch (Interceed; Johnson and Johnson Medical, Inc., New Brunswick, NJ), three stitches of 6-0 polydioxanone at tightness of 0.6N or fibrin glue (Tisseel Duo Quick; Baxter AG, Wien, Austria). Blood sample and pancreas specimens, both at the resection site and far away, were taken 1, 7, and 21 days postoperatively from exposed animals, sham operated animals (n = 18 in each) and from unexposed baseline animals (n = 5). Necrosis, edema, leukocyte infiltration, hemorrhage, vacuolization, and fibrosis were histologically assessed separately.

RESULTS

Each resection and sham operation induced similar increase in the amylase activity on day 1 with normalization by day 7. Resection with ultrasonic scissors and electrocautery induced more tissue injury to the pancreas than resection with surgical scalpel independent of the method for hemostasis. The injury, although somewhat milder in intensity, was also observed in parts of the pancreas located far away from the site of resection.

CONCLUSIONS

Of the compared methods, surgical scalpel resection plus cellulose patch or fibrin glue hemostasis induced the least histological changes in the pancreatic parenchyma. This injury response spread over the pancreas.

Cellular origins of adult human islet in vitro dedifferentiation

Cultured human islets can be dedifferentiated to duct-like structures composed mainly of cytokeratin+ and nestin+ cells. Given that these structures possess the potential to redifferentiate into islet-like structures, we sought to elucidate their specific cellular origins. Adenoviral vectors were engineered for beta-, alpha-, delta- or PP-cell-specific GFP expression. A double-stranded system was designed whereby cultures were infected with two vectors: one expressed GFP behind the cumate-inducible promoter sequence, and the other expressed the requisite transactivator behind the human insulin, glucagon, somatostatin or pancreatic polypeptide promoter. This system labels hormone+ cells in the islet in a cell-specific manner, allowing these cells to be tracked during the course of transformation from islet to duct-like structure. Post-infection, islets were cultured to induce dedifferentiation. Fluorescence microscopy demonstrated that alpha-, delta- and PP-cells contributed equally to the cytokeratin+ population, with minimal beta-cell contribution, whereas the converse was true for nestin+ cells. Complementary targeted cell ablation studies, using streptozotocin or similar adenoviral expression of the Bax (Bcl2-associated X protein) toxigene, validated these findings and suggested a redundancy between alpha-, delta- and PP-cells with respect to cytokeratin+ cell derivation. These results call into question the traditional understanding of islet cells as being terminally differentiated and provide support for the concept of adult islet morphogenetic plasticity.

PANCREATIC INJURY AFTER THORACOABDOMINAL AORTIC OCCLUSION IN A PORCINE MODEL

BACKGROUND

The aim of this study was to investigate pancreatic injury after 45 min of thoracoabdominal aortic occlusion in a porcine model.

METHODS

Twenty-four pigs were used. Six pigs underwent sham operation and 18 intravascular balloon thoracoabdominal aortic occlusions for 45 min. The animals were randomly killed at 12, 48 and 120 h after reperfusion. After killing, all pancreata were examined macroscopically for any signs of acute pancreatitis, whereas gland specimens were harvested for histological study to evaluate pancreatic injury (haematoxylin and eosin staining) and acinar cell apoptosis (Terminal deoxynucleotidyl transferase mediated dUTP Nick-End Labelling staining).

RESULTS

Pancreatic injury severity score was mildly increased in terms of oedematous features at 12 h after reperfusion, but normalized to sham levels by the second day and thereafter. Necrotic injury was not statistically significant at any time point. Acinar cell apoptotic index was mildly increased at 12 and 48 h, but showed a tendency to decrease towards sham levels by the fifth day. One animal developed acute pancreatitis.

CONCLUSION

Acute pancreatitis is unlikely to occur after 45 min of thoracoabdominal aortic occlusion. However, an early, mild oedematous and apoptotic injury that occurs subclinically seems to be a constant event. This injury might have clinical significance when combined with pre-existent pancreatic pathologies.

Vectorial bicarbonate transport by Capan-1 cells: a model for human pancreatic ductal secretion

Human pancreatic ducts secrete a bicarbonate-rich fluid but our knowledge of the secretory process is based mainly on studies of animal models. Our aim was to determine whether the HCO(3)(-) transport mechanisms in a human ductal cell line are similar to those previously identified in guinea-pig pancreatic ducts. Intracellular pH was measured by microfluorometry in Capan-1 cell monolayers grown on permeable filters and loaded with BCECF. Epithelial polarization was assessed by immunolocalization of occludin. Expression of mRNA for key electrolyte transporters and receptors was evaluated by RT-PCR. Capan-1 cells grown on permeable supports formed confluent, polarized monolayers with well developed tight junctions. The recovery of pH(i) from an acid load, induced by a short NH(4)(+) pulse, was mediated by Na(+)-dependent transporters located exclusively at the basolateral membrane. One was independent of HCO(3)(-) and blocked by EIPA (probably NHE1) while the other was HCO(3)(-)-dependent and blocked by H(2)DIDS (probably pNBC1). Changes in pH(i) following blockade of basolateral HCO(3)(-) accumulation confirmed that the cells achieve vectorial HCO(3)(-) secretion. Dose-dependent increases in HCO(3)(-) secretion were observed in response to stimulation of both secretin and VPAC receptors. ATP and UTP applied to the apical membrane stimulated HCO(3)(-) secretion but were inhibitory when applied to the basolateral membrane. HCO(3)(-) secretion in guinea-pig ducts and Capan-1 cell monolayers share many common features, suggesting that the latter is an excellent model for studies of human pancreatic HCO(3)(-) secretion.

The Role of Aquaporin Water Channels in Fluid Secretion by the Exocrine Pancreas

The mammalian exocrine pancreas secretes a near-isosmotic fluid over a wide osmolarity range. The role of aquaporin (AQP) water channels in this process is now becoming clearer. AQP8 water channels, which were initially cloned from rat pancreas, are expressed at the apical membrane of pancreatic acinar cells and contribute to their osmotic permeability. However, the acinar cells secrete relatively little fluid and there is no obvious defect in pancreatic function in AQP8 knockout mice. Most of the fluid secreted by the pancreas is generated by ductal epithelial cells, which comprise only a small fraction of the gland mass. In the human pancreas, secretion occurs mainly in the intercalated ducts, where the epithelial cells express abundant AQP1 and AQP5 at the apical membrane and AQP1 alone at the basolateral membrane. In the rat and mouse, fluid secretion occurs mainly in the interlobular ducts where AQP1 and AQP5 are again co-localized at the apical membrane but appear to be expressed at relatively low levels. Nonetheless, the transepithelial osmotic permeability of rat interlobular ducts is sufficient to support near-isosmotic fluid secretion at observed rates. Furthermore, apical, but not basolateral, application of Hg(2+) significantly reduces the transepithelial osmotic permeability, suggesting that apical AQP1 and AQP5 may contribute significantly to fluid secretion. The apparently normal fluid output of the pancreas in AQP1 knockout mice may reflect the presence of AQP5 at the apical membrane.