Formation Of Tubular Complexes Research Articles

Clusterin is highly expressed in tubular complexes during spontaneous pancreatitis of spontaneous hypertensive rats.

Pancreatitis is an inflammatory disorder of pancreas which leads to varying degrees of pancreatic endocrine and exocrine dysfunction and manifests in either acute or chronic forms. Spontaneous pancreatitis in experimental animals has rarely been reported. Here, we found acute to chronic courses of spontaneous pancreatitis in spontaneously hypertensive rats (SHRs), showing the formation of tubular complexes (TCs) and enhanced islet regeneration. We investigated the expression pattern of clusterin in the pancreas of SHRs based on immunohistochemistry (IHC). IHC analysis revealed the strong expression of clusterin in dedifferentiated duct-like cells and regenerative islets of TCs. These results imply that clusterin might be involved in the formation of TCs and parenchymal regeneration during rat pancreatitis.

Luteolin inhibits pancreatitis‑induced acinar‑ductal metaplasia, proliferation and epithelial‑mesenchymal transition of acinar cells.

Luteolin, a flavone, has been demonstrated to have anti-cancer properties. In the current study, the effects of luteolin on certain carcinogenesis-associated changes induced by pancreatitis, which are significant risk factors for pancreatic cancer, were investigated. Male six-week-old C57BL6 mice used in the current study were divided into three groups; the control group, acute pancreatitis group and luteolin group. Intra-peritoneal injection of cearulein was performed in the acute pancreatitis group and luteolin group to induce acute pancreatitis whereas the luteolin group received intra-peritoneal injection of luteolin. The control group received intra-peritoneal injection of normal saline. Then, the expression of SOX9, phosphorylated (p-) STAT3, p-EGFR, cytokeratin-19, Ki67 and N-cadherin were determined by immunohistochemistry. Morphological changes of acinar cells were determined by hematoxylin and eosin staining. The mRNA expression of the epithelial-mesenchymal transition markers CDH1, CDH2, Slug, Zeb1, EpCAM, ZO1, Vimentin, Snail and Twist was determined by reverse transcription-quantitative polymerase chain reaction. It was identified that luteolin inhibits the formation of tubular complexes and ectopic expression of cytokeratin-19 and luteolin also decreased proteins of SOX9, p-STAT3 and p-EGFR. In addition, luteolin inhibits proliferation and epithelial-mesenchymal transition of acinar cells induced by acute pancreatitis. As tubular complex formation and ectopic expression of cytokeratin-19 were two prominent characters of acinar-ductal metaplasia, it was concluded that luteolin inhibits acinar-ductal metaplasia induced by pancreatitis and also inhibits pancreatitis-induced proliferation and epithelial-mesenchymal transition of acinar cells. Acinar-ductal metaplasia and proliferation have close associations with pancreatic carcinogenesis. It is suggested that luteolin has potential anti-pancreatic carcinogenesis effects and merits further investigation.

ER stress protein AGR2 precedes and is involved in the regulation of pancreatic cancer initiation

The mechanisms of initiation of pancreatic ductal adenocarcinoma (PDAC) are still largely unknown. In the present study, we analysed the role of anterior gradient-2 (AGR2) in the earliest stages of pancreatic neoplasia. Immunohistochemical analysis of chronic pancreatitis (CP) and peritumoral areas in PDAC tissues showed that AGR2 was present in tubular complexes (TC) and early pancreatic intraepithelial neoplasia (PanINs). Moreover, AGR2 was also found in discrete subpopulations of non-transformed cells neighbouring these pre-neoplastic lesions. In primary cells derived from human patient-derived xenograft (PDX) model, flow-cytometry revealed that AGR2 was overexpressed in pancreatic cancer stem cells (CSC) compared with non-stem cancer cells. In LSL-KrasG12D;Pdx1-Cre (KC) mouse model Agr2 induction preceded the formation of pre-neoplastic lesions and their development was largely inhibited by Agr2 deletion in engineered LSL-KrasG12D;Pdx1-Cre; Agr2−/− mice. In vitro, AGR2 expression was stimulated by tunicamycin-induced endoplasmic reticulum (ER) stress in both KRAS wild-type normal pancreas cells, as well as in KRAS mutated pancreatic cancer cells and was essential for ER homoeostasis. The unfolded protein response proteins GRP78, ATF6 and XBP1s were found expressed in CP and PDAC peritumoral tissues, but in contrast to AGR2, their expression was switched off during TC and PanIN formation. Real-time PCR and ELISA analyses showed that ER stress induced a pro-inflammatory phenotype in pancreatic normal, cancer and stellate cells. Moreover, AGR2 expression was inducible by paracrine transfer of ER stress and pro-inflammation between different pancreatic cell types. Our findings demonstrate that AGR2 induced in ER-stressed and inflammatory pre-neoplastic pancreas is a potential marker of cancer progenitor cells with an important functional role in PDAC initiation.

GNASR201H and KrasG12D cooperate to promote murine pancreatic tumorigenesis recapitulating human intraductal papillary mucinous neoplasm

Intraductal papillary mucinous neoplasm (IPMN), the most common pancreatic cystic neoplasm, is known to progress to invasive ductal adenocarcinoma. IPMNs commonly harbor activating somatic mutations in GNAS and KRAS, primarily GNAS(R201H) and KRAS(G12D). GNAS encodes the stimulatory G-protein α subunit (Gsα) that mediates a stimulatory signal to adenylyl cyclase to produce cyclic adenosine monophosphate (cAMP), subsequently activating cAMP-dependent protein kinase A. The GNAS(R201H) mutation results in constitutive activation of Gsα. To study the potential role of GNAS in pancreatic tumorigenesis in vivo, we generated lines of transgenic mice in which the transgene consisted of Lox-STOP-Lox (LSL)-GNAS(R201H) under the control of the CAG promoter (Tg(CAG-LSL-GNAS)). These mice were crossed with pancreatic transcription factor 1a (Ptf1a)-Cre mice (Ptf1a(Cre/+)), generating Tg(CAG-LSL-GNAS);Ptf1a(Cre/+) mice. This mouse line showed elevated cAMP levels, small dilated tubular complex formation, loss of acinar cells and fibrosis in the pancreas; however, no macroscopic tumorigenesis was apparent by 2 months of age. We then crossed Tg(CAG-LSL-GNAS);Ptf1a(Cre/+) mice with LSL-Kras(G12D) mice, generating Tg(CAG-LSL-GNAS);LSL-Kras(G12D);Ptf1a(Cre/+) mice. We used these mice to investigate a possible cooperative effect of GNAS(R201H) and Kras(G12D) in pancreatic tumorigenesis. Within 5 weeks, Tg(CAG-LSL-GNAS);LSL-Kras(G12D);Ptf1a(Cre/+) mice developed a cystic tumor consisting of marked dilated ducts lined with papillary dysplastic epithelia in the pancreas, which closely mimicked the human IPMN. Our data strongly suggest that activating mutations in GNAS and Kras cooperatively promote murine pancreatic tumorigenesis, which recapitulates IPMN. Our mouse model may serve as a unique in vivo platform to find biomarkers and effective drugs for diseases associated with GNAS mutations.

Abstract 4195: GNASR201H and KrasG12D cooperate to promote murine pancreatic tumorigenesis recapitulating human intraductal papillary mucinous neoplasm

Abstract Intraductal papillary mucinous neoplasm (IPMN) is the most common pancreatic cystic neoplasm, which is a precursor of the invasive ductal adenocarcinoma. IPMNs recurrently harbor activating somatic mutations in GNAS and KRAS, mostly GNASR201H and KRASG12D. GNAS encodes the stimulatory G-protein α subunit (Gsα) that mediates a stimulatory signal to adenylyl cyclase to produce cyclic AMP (cAMP), a second messenger activating cAMP dependent protein kinase (PKA). The GNASR201H mutation is known to result in constitutive activation of Gsα and its downstream signaling molecules, which induces expression of various genes including mucin genes. To study a role of GNAS in pancreatic tumourigenesis in vivo, we generated transgenic mice lines of which transgene is consisted of Lox-STOP-Lox (LSL)- GNASR201H under the control of the CAG promoter (Tg(CAG-LSL-GNAS)). The transgene contains genetic elements that inhibit transcription and translation of GNASR201H flanked by functional LoxP sites. These mice lines were crossed to pancreatic transcription factor 1 a (Ptf1a)-cre mice, and generated Tg(CAG-LSL-GNAS);Ptf1a-cre mice. This mouse line showed elevated cAMP levels and a compensatory upregulation of PKA in the pancreas. GNASR201H alone was not sufficient to induce tumourigenesis by 2 months of age, but small dilated tubular complex formation, loss of acinar cells, and fibrosis, which could be a very early phenotype of IPMN. To know a cooperative effect of GNASR201H and KRASG12D in pancreatic tumorigenesis, we crossed Tg(CAG-LSL-GNAS);Ptf1a-cre mice with LSL-KrasG12D mice. Tg(CAG-LSL-GNAS);LSL-KrasG12D;Ptf1a-cre mice developed multiple cysts consisting of marked dilated ducts lined with papillary dysplastic epithelia in the pancreas within 5 weeks, which recapitulated human IPMNs. Our data strongly suggest that mutated GNAS cooperating with mutated KRAS may sufficiently cause to develop IPMN. Citation Format: Toru Furukawa, Etsuko Tanji, Masaki Ohmuraya, Katsunobu Taki, Kimi Araki. GNASR201H and KrasG12D cooperate to promote murine pancreatic tumorigenesis recapitulating human intraductal papillary mucinous neoplasm. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4195. doi:10.1158/1538-7445.AM2015-4195

Chronic Pancreatitis with Acinar–Ductal Metaplasia and Ductal Dysplasia in a Horse

A 16-year-old Friesian gelding with relapsing colic was humanely destroyed during diagnostic laparotomy due to suspected abdominal neoplasia. On post-mortem examination, the pancreas appeared as a firm mass (20×8×8cm). The cut surface had a lobular structure with multiple cavities. Histological examination revealed severe chronic fibrosing pancreatitis with acinar-ductal metaplasia and duct dysplasia, which was considered to be the cause of the recurrent colic. Formation of tubular complexes within a background of acinar-ductal metaplasia is similar to the regressive lesions detected in the human pancreas in the context of inflammation, duct obstruction, cystic fibrosis and neoplasia. Pancreatic acinar-ductal metaplasia and ductal dysplasia are considered to be preneoplastic conditions in man and in the mouse.

Sa1793 Bile Acid-Induced Acute Pancreatitis in Mice Is Caused by Acinar Cell Leukotriene B4 Secretion Through a Calcium-Independent Pathway

Background: Understanding the mechanism of chronic pancreatitis (CP) is limited by the lack of mouse models that mimic progression of the disease. The current mouse model of CP involves causing 20 episodes of acute pancreatitis by administering cerulein (50μg/kg x7, hourly x twice weekly X 10 weeks) making it an expensive and time consuming model. Resulting chronic pancreatitis in this model tends to resolve. Here, we present a novel model for induction of CP based on an L-Arginine induced acute pancreatitis model previously developed by our group. Methods: Animals in the CP group underwent four L-arginine induced episodes of acute pancreatitis over a four week period. For each episode, animals were given two injections (one hour apart) of either saline or L-arginine (4.5 g/kg) followed by a saline injection 1 hour later. Animals were sacrificed at 7, 14 and 21 days after the last cycle of injections. The entire pancreas was dissected and weighed. Pancreatic tissue was processed for RNA, protein, histology and immunohistochemistry. Feces were collected and analyzed for fat content. Results: There was significant pancreatic atrophy on day 7 after completion of L-arginine induced episodes (70.5+12.6 mg in L-arginine injected vs. 243.8+2.9mg in saline injected animals, p <0.05). This atrophy persisted in animals sacrificed on day 14 and 21 after the last dose of L-arginine (88.0+25.3 mg at day 14 and 54.6+22.5 at day 21) in L-arginine treated animals. Histologically, in comparison to saline injected, Larginine treated animals showed destruction of acini, formation of tubular complexes, abnormal architecture, and fibro fatty replacement. In addition, Sirius red staining showed a significant increase in fibrosis in the L-arginine treated chronic pancreatitis group (day 7: 14.8+2.6%; day 14:15.9+3.9%; and day 21: 15.4+2.7%) compared to pancreas from control animals (1.4 + 0.1%).Furthermore, there was a significant increase in α-smooth muscle actin, desmin and, vimentin expression representing an increase in stellate cell activation and proliferation respectively. There was increase in inflammation as indicated by increase in expression of Cox-2 and nuclear localization of p65 in L-arginine treated animals as compared to control. We also observed an increase in fecal fat content in L-Arginine treated animals compared to control, although the animals were not on a high fat diet. Importantly, all the differences observed in the CP vs. normal groups persisted until at least three weeks after the last L-arginine injections. Conclusions: The L-arginine induced model of chronic pancreatitis is a relatively easy and inexpensive model which mimics all features of human chronic pancreatitis including pancreatic atrophy, fibrosis, inflammation, exocrine insufficiency and loss of architecture and the observed changes were stable.

Acinar-to-Ductal Metaplasia Induced by Adenovirus-Mediated Pancreatic Expression of Isl1

Tubular complexes (TCs) are aggregates of duct-like monolayered cells in the developing and regenerating pancreas. Recent studies showed that TCs have regenerative potential, including islet neogenesis. We previously delivered adenovirus vector (AdV) into exocrine cells of the pancreas by intra-common bile ductal (ICBD) injection, and found that AdV expressing Pdx1, a pancreas-specific transcription factor, causes TC formation and islet neogenesis. We also established RTF-Pdx1-EGFP mice, which ubiquitously express Pdx1 when tetracycline is removed from the drinking water. However, exogenous Pdx1 expression in adult RTF-Pdx1-EGFP mice did not cause any pathological changes in the pancreas during three weeks of observation after tetracycline withdrawal. To examine whether the host immune response induced by AdV was involved in TC formation, we delivered AdVs expressing pancreas-related transcription factors or an irrelevant protein into the pancreas of RTF-Pdx1-EGFP mice. Histological analyses showed that both AdV injection and Pdx1 expression are required for TC formation. We also analyzed the effects of these ICBD-injected AdVs. AdV expressing Isl1, a proendocrine transcription factor, effectively induced TC formation through acinar-to-ductal metaplasia, and exogenous Pdx1 expression facilitated this process. Considering the regenerative potential of TCs, a strategy that efficiently induces TC formation may lead to novel therapies for diabetes.

Su1251 Overexpression of EGFR in the Exocrine Pancreas Induces a Chronic Pancreatitis

Background and Aim: Chronic pancreatitis and pancreatic ductal adenocarcinoma (PDA) frequently overexpress epidermal growth factor receptor (EGFR) and EGF-family ligands. Although chronic pancreatitis is a risk factor for PDA, the relationship between chronic pancreatitis and PDA remains obscure. A critical obstacle to understanding the role of chronic pancreatitis in development of PDA is the lack of appropriate animal models for chronic pancreatitis with similar clinical courses as in human patients. Serine protease inhibitor Kazal type 1 (SPINK1: mouse homolog Spink3), which is also known as tumor associated trypsin inhibitor (TATI), is mainly produced in the pancreatic acinar cells. Recently, we showed that SPINK1 binds to EGFR to activate its downstream signaling. The present study aims to generate chronic pancreatitis model mice and assess the molecular events from chronic pancreatitis to PDA. Methods: 1) C57BL/6 female mice were repeatedly induced acute pancreatitis by using choline-deficient with ethionine (CDE) diet for 54 weeks. 2) To assess the molecular events caused by long term CDE diet treatment using Western blotting. 3) To further analyze the clinical importance of EGFR and SPINK1 in the chronic pancreatitis and PDA, we examined the expression of SPINK1 and EGFR. Immunohistochemical analyses were performed using human chronic pancreatitis and PDA samples. Results: 1) Histological evaluation revealed that chronic pancreatitis, characterized by acinar atrophy, fibrosis and well-developed tubular complexes (TCs), was observed after 24 wk of CDE-diet treatment. In spite of the severe pancreatic degeneration, neoplastic changes were not observed. 2) Expression of EGFR and its ligands (Spink3 and TGF α) and activation of K-Ras (GTP-Ras formation), which are frequently observed in human PDA, were indeed observed in parallel with TCs formation. In addition, cyclooxygenase-2 which induced by stimuli involved in inflammatory responses was also overexpressed. 3) In the human chronic pancreatitis samples, TCs were positive EGFR immunostaining. Furthermore, PDA cases were positive for both SPINK1 and EGFR immunoreactivity. Conclusion: We have successfully developed a chronic pancreatitis model with CDE diet. We also showed expression of EGFR and its potent ligands, phosphorylation of EGFR, and activation of K-Ras as the step of chronic inflammation. It was suggested that EGFR signaling cascades were important for the development from chronic pancreatitis to PDA. Howevere, chronic pancreatitis itself is not sufficient for the development of PDA. Further combinations of CDE-diet treatment with the administration of other promotion insults or genetic alterations may result in PDA development.

Su1252 Factors Predictive of Relapse, Cancer and Cyst Formation in Autoimmune Pancreatitis Patients

Background and Aim: Chronic pancreatitis and pancreatic ductal adenocarcinoma (PDA) frequently overexpress epidermal growth factor receptor (EGFR) and EGF-family ligands. Although chronic pancreatitis is a risk factor for PDA, the relationship between chronic pancreatitis and PDA remains obscure. A critical obstacle to understanding the role of chronic pancreatitis in development of PDA is the lack of appropriate animal models for chronic pancreatitis with similar clinical courses as in human patients. Serine protease inhibitor Kazal type 1 (SPINK1: mouse homolog Spink3), which is also known as tumor associated trypsin inhibitor (TATI), is mainly produced in the pancreatic acinar cells. Recently, we showed that SPINK1 binds to EGFR to activate its downstream signaling. The present study aims to generate chronic pancreatitis model mice and assess the molecular events from chronic pancreatitis to PDA. Methods: 1) C57BL/6 female mice were repeatedly induced acute pancreatitis by using choline-deficient with ethionine (CDE) diet for 54 weeks. 2) To assess the molecular events caused by long term CDE diet treatment using Western blotting. 3) To further analyze the clinical importance of EGFR and SPINK1 in the chronic pancreatitis and PDA, we examined the expression of SPINK1 and EGFR. Immunohistochemical analyses were performed using human chronic pancreatitis and PDA samples. Results: 1) Histological evaluation revealed that chronic pancreatitis, characterized by acinar atrophy, fibrosis and well-developed tubular complexes (TCs), was observed after 24 wk of CDE-diet treatment. In spite of the severe pancreatic degeneration, neoplastic changes were not observed. 2) Expression of EGFR and its ligands (Spink3 and TGF α) and activation of K-Ras (GTP-Ras formation), which are frequently observed in human PDA, were indeed observed in parallel with TCs formation. In addition, cyclooxygenase-2 which induced by stimuli involved in inflammatory responses was also overexpressed. 3) In the human chronic pancreatitis samples, TCs were positive EGFR immunostaining. Furthermore, PDA cases were positive for both SPINK1 and EGFR immunoreactivity. Conclusion: We have successfully developed a chronic pancreatitis model with CDE diet. We also showed expression of EGFR and its potent ligands, phosphorylation of EGFR, and activation of K-Ras as the step of chronic inflammation. It was suggested that EGFR signaling cascades were important for the development from chronic pancreatitis to PDA. Howevere, chronic pancreatitis itself is not sufficient for the development of PDA. Further combinations of CDE-diet treatment with the administration of other promotion insults or genetic alterations may result in PDA development.

Diabetes aggravates acute pancreatitis and inhibits pancreas regeneration in mice

It is well established that acute pancreatitis often causes diabetes and that a high blood glucose level associated with pancreatitis is a marker of poor prognosis. The aim of this study was to evaluate if diabetes merely reflects the severity of pancreatitis or whether it can also aggravate the progression of this disease in a vicious circle. Reversible acute oedematous pancreatitis was induced in untreated and streptozotocin-treated diabetic mice by injection of cerulein. Progression of pancreatitis was studied by immunohistochemistry, ELISA and various other enzyme assays. The production of regenerating islet-derived 3β (REG3β) was determined by western blot and immunohistochemistry. While cerulein treatment in non-diabetic mice resulted in acute pancreatitis followed by regeneration of the pancreas within 7 days, diabetes aggravated pancreatitis, inhibited the regeneration of the exocrine tissue and led to strong atrophy of the pancreas. The aggravation of pancreatitis by diabetes was characterised by decreased production of the anti-inflammatory protein REG3β, increased inflammation, augmented oedema formation and increased cell death during the acute phase of pancreatitis (p < 0.05). During the regenerative phase, diabetes augmented inflammation, increased cell death, reduced acinar cell expansion and increased the expansion of duct as well as interstitial cells, resulting in the formation of tubular complexes (p < 0.05). Administration of insulin reversed the observed phenotype in diabetic mice. Diabetes aggravates acute pancreatitis and suppresses regeneration of the exocrine tissue. Thus, diabetes is not just a concomitant phenomenon of pancreatitis, but can have a fundamental influence on the progression of acute pancreatitis.

Extensive Pancreas Regeneration Following Acinar-Specific Disruption of Xbp1 in Mice

Progression of diseases of the exocrine pancreas, which include pancreatitis and cancer, is associated with increased levels of cell stress. Pancreatic acinar cells are involved in development of these diseases and, because of their high level of protein output, they require an efficient, unfolded protein response (UPR) that mediates recovery from endoplasmic reticulum (ER) stress following the accumulation of misfolded proteins. To study recovery from ER stress in the exocrine organ, we generated mice with conditional disruption of Xbp1 (a principal component of the UPR) in most adult pancreatic acinar cells (Xbp1fl/fl). We monitored the effects of constitutive ER stress in the exocrine pancreas of these mice. Xbp1-null acinar cells underwent extensive apoptosis, followed by a rapid phase of recovery in the pancreas that included expansion of the centroacinar cell compartment, formation of tubular complexes that contained Hes1- and Sox9-expressing cells, and regeneration of acinar cells that expressed Mist1 from the residual, surviving Xbp1+ cell population. XBP1 is required for homeostasis of acinar cells in mice; ER stress induces a regenerative response in the pancreas that involves acinar and centroacinar cells, providing the needed capacity for organ recovery from exocrine pancreas disease.

Pancreatic Atrophy Due to Zinc Toxicosis in Two African Ostriches (Struthio camelus)

Two of three captive adult African ostriches exhibited inappetance and weakness. In spite of treatment, the two birds were euthanized because of lack of clinical improvement. Postmortem examination demonstrated exocrine pancreatic degeneration, necrosis, and atrophy. Grossly, one ostrich had a markedly diminished pancreatic mass. Histologically, there was massive pancreatic acinar (exocrine) atrophy, marked interstitial fibrosis, and tubular complex formation in one animal, and the second ostrich had active pancreatic acinar necrosis. Toxicologic testing revealed markedly elevated liver zinc levels in the first two birds, whereas the third ostrich had normal serum levels of zinc and continues without apparent disease. This form of zinc toxicosis, while previously reported in different avian species, has been only rarely described in ratites.

Chronic Pancreatitis in Mice by Treatment with Choline-Deficient Ethionine-Supplemented Diet

Although chronic pancreatitis is a risk factor for pancreatic ductal adenocarcinoma (PDA), the relationship between chronic pancreatitis and PDA remains obscure. A critical obstacle to understanding the role of chronic pancreatitis is the lack of animal models. To develop one such model, mice were fed long-term with a choline deficient ethionine-supplemented (CDE) diet. Histological evaluation revealed that chronic pancreatitis, characterized by acinar atrophy, fibrosis and well-developed tubular complexes (TCs), was observed after 24 weeks of CDE diet treatment. Furthermore, expression of epidermal growth factor receptor (EGFR) and its ligands; serine protease inhibitor Kazal type 3 (Spink3) and transforming growth factor alpha (TGF alpha) and activation of K-Ras (GTP-Ras formation), which are frequently observed in human PDA, were indeed observed in parallel with TCs formation. Neoplastic lesions were not found after 54 weeks of treatment, suggesting that a continuation of CDE diet or another insult is required for the development of PDA.

Morphological Changes of Pancreatic Ducts in Otsuka Long-Evans Tokushima Fatty Rats

To determine if pancreatic ductal changes characteristic of chronic pancreatitis occur in male Otsuka Long-Evans Tokushima Fatty (OLETF) rats and to elucidate the 3-dimensional structure of the pancreatic ducts in those rats. Male OLETF rats aged 10, 20, and 40 weeks were used. The pancreas was injected with a 120% barium sulfate suspension into the pancreatic ducts, after which radiograph images of the injected pancreas were taken using radiography of the soft parts. Conventional fixed pancreatic tissues were observed by the use of light and scanning electron microscopy, whereas corrosion casts of the pancreatic ducts were observed by the use of scanning electron microscopy. In 20- and 40-week-old male OLETF rats, deletion of acini and formation of tubular complexes and tortuous or helical, deformed, dilated pancreatic ducts were found, whereas the inner surfaces of pancreatic ducts had many craterlike depressions and long cilia. Male OLETF rats demonstrated the same morphological changes in pancreatic ductal lumina and histological changes in pancreatic tissues as the rats were subjected to pancreatic duct ligation. These results suggested that increased pancreatic duct pressure occurs in male OLETF rats and induces the chronic pancreatitis-like lesions, including the above-mentioned findings.

A new mouse model of pancreatic cancer: PTEN gets its Akt together

PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a negative regulator of the oncogenic PI3-K/Akt signaling pathway. Loss-of-function mutations of PTEN are seen in several human solid cancers. A murine model of conditional Pten inactivation in the pancreas is described that leads to acquisition of a profound metaplastic ductal phenotype accompanied by loss of differentiated acinar units. Evidence is presented for a centroacinar cell origin of the metaplastic "neoductules." These mice also develop invasive pancreatic adenocarcinomas at a low frequency, and provide a unique in vivo platform for exploring the role of PI3-K/Akt signaling in pancreatic neoplasia.

Transgenic overexpression of amphiregulin induces a mitogenic response selectively in pancreatic duct cells

Background & Aims: The epidermal growth factor (EGF) receptor family and the corresponding ligands are frequently overexpressed in pancreatic cancer. To compare the biological effects of transforming growth factor (TGF)-α and amphiregulin (AR) on growth and differentiation of the exocrine pancreas, we have generated transgenic mice overexpressing AR under control of the elastase promoter. Methods: Two independently generated transgenic mouse lines overexpress 50-, 43-, 28-, 26-, and 16-kilodalton AR forms in the pancreas. Results: Morphologic and immunohistochemical examinations suggest that small intralobular duct and centro-acinar cells proliferate in response to AR in these mice. AR transgenic mice display increased Ras, Erk1/2, cyclin D/CDK4, and cyclin E/CDK2 activity and G1/S progression in pancreatic duct cells. In contrast to TGF-α transgenic mice, AR neither induced tubular complex formation nor elicited a strong fibrogenic response. AR induced a slight induction of ErbB2 on duct cells, whereas TGF-α resulted in overexpression of the EGF receptor in cells within tubular complexes. Furthermore, AR and TGF-α displayed different effects on differentiation of isolated acini in vitro comparable to the situation in vivo. Conclusions: These data suggest that AR induces a mitogenic response selectively in small duct cells through activation of Ras, CDK2, and CDK4, respectively. The closely related EGF receptor ligands, AR and TGF-α, display different biological effects when overexpressed in the exocrine pancreas in vivo.GASTROENTEROLOGY 2002;122:1898-1912

Differential Effects of Caspase-1/Interleukin-1β–Converting Enzyme on Acinar Cell Necrosis and Apoptosis in Severe Acute Experimental Pancreatitis

There is recent experimental evidence that inhibition of caspase-1/interleukin-1β converting enzyme (ICE) significantly ameliorates overall severity and survival in severe acute experimental pancreatitis. However, little is known about the effects of this approach on the dynamics and mechanisms of local acinar cell damage, which we aimed to investigate in the present study. Severe acute pancreatitis (SAP) was induced by retrograde infusion of 4% sodium taurocholate in rats treated with isotonic saline or a highly selective, irreversible inhibitor of ICE. After 3, 6, and 24 hours, 3 and 7 days, acinar cell death by necrosis and apoptosis, as well as intrapancreatic and systemic interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) expression, was assessed. Treatment with the ICE inhibitor significantly reduced the extent of acinar cell necrosis accounting for major parenchymal destruction. In contrast, apoptosis was confined to the postacute course of the disease and was closely related to tubular complex formation, both remaining unchanged. Whereas intrapancreatic IL-1β mRNA expression was highly up-regulated in both treated and untreated animals, active IL-1β protein expression and subsequent neutrophil tissue infiltration was dramatically decreased in the ICE-inhibited group. Parallel to the onset of enhanced apoptotic acinar cell death and tubular complex formation, TNF-α mRNA and protein expression was up-regulated, with levels being lower in ICE inhibitor-treated rats. We conclude that activation of caspase-1/ICE plays a central role in the progression of acinar cell death by necrosis in SAP. Herein, IL-1β–mediated neutrophil infiltration seems to be a crucial step in enhanced cellular destruction. In contrast, acinar cell apoptosis contributes to ductal transformation and is independent of this mechanism, but may be influenced by TNF-α

Morphological changes and morphological-functional correlations in acute experimantal ischemia/reperfusion pancreatitis in rats. An important role of tubular complexes formation

Morphological changes and morphological-functional correlations in acute experimantal ischemia/reperfusion pancreatitis in rats. An important role of tubular complexes formation

Acinar cell apoptosis and the origin of tubular complexes in caerulein-induced pancreatitis.

The interrelationship between acinar cell apoptosis and tubular complex formation was examined in caerulein-induced pancreatitis using histology, immunohistochemistry, electron microscopy and DNA gel electrophoresis. Rats were given 8 hourly subcutaneous injections of caerulein, 24 micrograms/kg, for up to 2 days. Morphologically and biochemically typical apoptosis affected 4.6 and 8.9% of acinar cells at 1 and 2 days, respectively, resulting in removal of most acinar cells by 2 days. Consequently, pancreatic ducts, the lining cells expressing bcl-2 and therefore resistant to apoptosis, became much more closely approximated to form the basis of tubular complexes; small numbers of immunohistochemically discrete acinar cells in their lining were either pre-apoptotic resistant to it or newly formed. Proliferation of duct-like lining cells was associated with apoptosis, an increase in islet cells and acinar cell regeneration. There was evidence of duct to acinar cell differentiation but the main increase in acinar cell numbers appeared to derive from proliferation of newly formed acinar cells.