Pathophysiologic studies of experimental chronic pancreatitis in rats induced by injection of zein-oleic acid-linoleic acid solution into the pancreatic duct

Mesenchymal stem cells in fibrotic diseases-the two sides of the same coin

Fibrosis is caused by extensive deposition of extracellular matrix (ECM) components, which play a crucial role in injury repair. Fibrosis attributes to ~45% of all deaths worldwide. The molecular pathology of different fibrotic diseases varies, and a number of bioactive factors are involved in the pathogenic process. Mesenchymal stem cells (MSCs) are a type of multipotent stem cells that have promising therapeutic effects in the treatment of different diseases. Current updates of fibrotic pathogenesis reveal that residential MSCs may differentiate into myofibroblasts which lead to the fibrosis development. However, preclinical and clinical trials with autologous or allogeneic MSCs infusion demonstrate that MSCs can relieve the fibrotic diseases by modulating inflammation, regenerating damaged tissues, remodeling the ECMs, and modulating the death of stressed cells after implantation. A variety of animal models were developed to study the mechanisms behind different fibrotic tissues and test the preclinical efficacy of MSC therapy in these diseases. Furthermore, MSCs have been used for treating liver cirrhosis and pulmonary fibrosis patients in several clinical trials, leading to satisfactory clinical efficacy without severe adverse events. This review discusses the two opposite roles of residential MSCs and external MSCs in fibrotic diseases, and summarizes the current perspective of therapeutic mechanism of MSCs in fibrosis, through both laboratory study and clinical trials.

Animal models of pancreatitis: Can it be translated to human pain study?

Chronic pancreatitis affects many individuals around the world, and the study of the underlying mechanisms leading to better treatment possibilities are important tasks. Therefore, animal models are needed to illustrate the basic study of pancreatitis. Recently, animal models of acute and chronic pancreatitis have been thoroughly reviewed, but few reviews address the important aspect on the translation of animal studies to human studies. It is well known that pancreatitis is associated with epigastric pain, but the understanding regarding to mechanisms and appropriate treatment of this pain is still unclear. Using animal models to study pancreatitis associated visceral pain is difficult, however, these types of models are a unique way to reveal the mechanisms behind pancreatitis associated visceral pain. In this review, the animal models of acute, chronic and un-common pancreatitis are briefly outlined and animal models related to pancreatitis associated visceral pain are also addressed.

Animal models of chronic pancreatitis

Animal models for CP in rats can be classified into 2 groups: one is noninvasive or nonsurgical models and the other is invasive or surgical models. Pancreatic injury induced by repetitive injections of supramaximal stimulatory dose of caerulein (Cn) or by intraductal infusion of sodium taurocholate (NaTc) recovered within 14 days, whereas that caused by repetitive injection of arginine or by intraductal infusion of oleic acid was persistent. However, the destroyed acinar tissues were replaced by fatty tissues without fibrosis. Transient stasis of pancreatic fluid flow by 0.01% agarose and minimum injury of the pancreatic duct by 0.1% NaTc solution induced progressive pancreatic injury although one alone is insufficient to cause persistent pancreatic injury. However, the damaged tissue was replaced by fatty tissue without fibrosis. Continuous pancreatic ductal hypertension (PDH) caused diffuse interlobular and intralobular fibrosis closely resembling human CP.

Camostat, an oral trypsin inhibitor, reduces pancreatic fibrosis induced by repeated administration of a superoxide dismutase inhibitor in rats

BACKGROUND AND AIM

An oral trypsin inhibitor, camostat (CM), has a beneficial effect on chronic pancreatitis, but its mechanism is not yet fully understood. Recently, pancreatic stellate cells (PSC) have been reported to play an essential role in pancreatic fibrosis. An experimental model of pancreatic fibrosis induced by a superoxide dismutase (SOD) inhibitor (diethyldithiocarbamate [DDC]) was developed in rats. Thus, the effect of an oral trypsin inhibitor on pancreatic fibrosis and PSC was investigated.

METHODS

Pancreatic fibrosis was induced in rats using DDC (DDC rats). DDC + CM rats were administered DDC, and subsequently were fed a diet containing CM. Immunohistochemistry of the pancreas was performed with monoclonal anti-alpha-smooth muscle actin (alpha-SMA) antibody and anti-desmin antibody.

RESULTS

The DDC rats showed a significant increase in alpha-SMA-positive cells or desmin-positive cells compared with control rats. These significant increases in the fibrotic area improved after treatment with CM. The level of prolyl hydroxylase in the pancreas, which significantly increased as a result of DDC, decreased after treatment with CM.

CONCLUSION

Camostat has a beneficial effect on pancreatic fibrosis induced by the administration of a SOD inhibitor, which inhibits the proliferation and activation of PSC.

Molecular cloning and characterization of chymopasin, a novel serine protease from rat pancreas

INTRODUCTION

Pancreas secretes many enzymes for food digestion into the pancreatic juice. We cloned a novel serine protease, chymopasin, from rat pancreas.

AIMS

To know the localization of this enzyme in the pancreas and to analyze the enzymatic characteristics.

METHODOLOGY

We cloned chymopasin cDNA using 3' and 5' RACEs. Northern blot and in situ hybridization were used to study the expression of this enzyme. Recombinant chymopasin protein produced by was analyzed by Western blot using specific antibody, and its enzymatic characteristics were examined using commercially available synthetic substrates, fibrin and gelatin.

RESULTS

The open reading frame of rat chymopasin consisted of 792 bp encoding 264 amino acid residues. The deduced amino acid sequence contained the essential catalytic triad characteristic of the serine protease family. There was no putative N-glycosylation site. The amino acid sequence of rat chymopasin showed 54.5% identity to rat chymotrypsin B. Northern blot analysis showed that the transcript was strongly expressed in the pancreas. In situ hybridization with digoxigenin-labeled cRNA probe showed that the positive signals were observed in the acinar cells, but not in the islet or duct cells. Chymopasin protein was detected in the pancreas homogenate and bile-pancreatic juice. Further, cerulein stimulated the secretion of rat chymopasin into bile-pancreatic juice.

CONCLUSION

These results suggested that rat chymopasin might be a digestive enzyme secreted from the acinar cells. From the enzyme assay using synthetic substrates, the purified recombinant chymopasin expressed in showed chymotrypsin-like activity. In addition, rat recombinant chymopasin showed fibrinolytic and gelatinolytic activities. These results suggested a role in the pathogenesis of pancreatic damage.

Effect of camostat mesilate on the expression of pancreatitis-associated protein (PAP), p8, and cytokines in rat spontaneous chronic pancreatitis

An oral protease inhibitor, camostat mesilate (CM) has been used clinically for chronic pancreatitis (CP) in Japan, but it lacks enough scientific evidence of its effectiveness. The aim of this study was to analyze the effect of CM on the gene expressions of pancreatitis-associated protein (PAP), p8, and cytokines such as interleukin-6 and transforming growth factor-beta1 in spontaneous CP model (WBN/Kob rats). CM (10 mg/100 g body weight), mixed in MB-3 diet, was administered orally and gene expressions were analyzed by reverse transcription-polymerase chain reaction. In untreated WBN/Kob rats, the gene expressions of all the four factors peaked at 12 weeks, whereas they were significantly suppressed in the CM-treated rats. CM significantly increased the body weight and pancreatic wet weight, and it significantly inhibited inflammatory changes and fibrosis of the pancreas. These results suggest that CM inhibits pancreatic inflammation and fibrosis through the suppression of gene expressions of PAP, p8, and cytokines in CP.

Increased intestinal phospholipase A(2) activity catalyzed by phospholipase B/lipase in WBN/Kob rats with pancreatic insufficiency

Male WBN/Kob rats derived from the Wistar strain spontaneously develop chronic pancreatitis as late as 3 months old. To assess the degree of disease severity, we compared the lipolytic enzyme levels in pancreas of 2-, 4-, and 6-month-old WBN/Kob rats fed isocaloric no fat (NF) and high fat (HF, 57% of total calories) diets and its pathology. Diet treatment did not significantly affect lipase and group Ib phospholipase A(2) (PLA(2)) levels in the pancreas at all ages. Development of chronic pancreatitis at the age of 4 and 6 months was consistent with the tendency of decreasing group Ib PLA(2) specific content determined by enzyme immunoassay and lipase activity, and the decreased number of group Ib PLA(2)-positive acinar cells. Pancreatic lipase and group Ib PLA(2) levels of 4-month-old WBN/Kob rats were significantly lower than those of control Wistar rats at age 4 months irrespective of diet. This allowed us to adopt 4-month-old WBN/Kob rats as a model of pancreatic insufficiency, which could be a useful tool to examine the role of gastrointestinal enzymes in lipid digestion. Ca(2+)-independent PLA(2) activity of brush border membrane-associated phospholipase B/lipase (PLB/LIP) in ileal mucosa increased significantly in 4-month-old WBN/Kob rats while its content and transcript levels remained constant, suggesting its activation at the enzyme level. In WBN/Kob rats fed the HF diet at age 4 months, PLA(2) activity catalyzed by PLB/LIP in the proximal ileal mucosa was four times the total PLA(2) activity in the intestinal lumen. These results indicate that PLB/LIP compensates for the depletion of pancreatic lipolytic enzymes in WBN/Kob rats with pancreas insufficiency.

Immunohistochemical characterization of pancreatic tumors induced by dimethylbenzanthracene in rats

Dimethylbenzanthracene (DMBA) induces pancreatic adenocarcinomas in rats 9 months after carcinogen exposure, with precursor lesions (tubular complexes) developing 1 month after initiation of treatment. Because previous studies have suggested an acinar cell of origin for these tumors, we investigated the expression pattern of ductal, acinar, and islet cell markers in these cancers to gain insight into their phenotype and cell of origin. Pancreatic neoplasms were induced in rats by implantation of DMBA into the head of the pancreas. Lesions studied included 10 early tubular complexes (DMBA for 2 weeks), 8 tubular complexes (DMBA for 1 month), and 10 adenocarcinomas (DMBA for 9 months). Normal rat pancreas served as a control. For comparison, 5 human ductal adenocarcinomas were also evaluated. Immunohistochemistry with ductal (keratin, cytokeratin 19, cytokeratin 20), acinar (chymotrypsin), and islet (chromogranin A) cell markers was performed to analyze the tissues. Rat tubular complexes and adenocarcinomas revealed strong expression of keratin, cytokeratin 19, and cytokeratin 20 in the cytoplasm of all neoplastic cells, absence of chymotrypsin, and rare immunoreactivity to chromogranin A. Human adenocarcinomas showed strong expression of keratin and cytokeratin 19 in all neoplastic cells, expression of cytokeratin 20 in 5-20% of cells, and absence of chymotrypsin and chromogranin A. Pancreatic adenocarcinomas induced by DMBA in rats express markers consistent with a ductal phenotype, as observed in human tumors. Ductal marker expression in early tumor stages suggests a ductal cell of origin.