Experimental Models of Pancreatitis

Acute pancreatitis is an inflammatory disease characterized by interstitial edema, inflammatory cell infiltration, and acinar cell necrosis, depending on its severity. Regardless of the extent of tissue injury, acute pancreatitis is a completely reversible process with evident normal tissue architecture after recovery. Its pathogenic mechanism has been known to be closely related to intracellular digestive enzyme activation. In contrast to acute pancreatitis, chronic pancreatitis is characterized by irreversible tissue damage such as acinar cell atrophy and pancreatic fibrosis that results in exocrine and endocrine insufficiency. Recently, many studies of chronic pancreatitis have been prompted by the discovery of the pancreatic stellate cell, which has been identified and distinguished as the key effector cell of pancreatic fibrosis. However, investigations into the pathogenesis and treatment of pancreatitis face many obstacles because of its anatomical location and disparate clinical course. Due to these difficulties, most of our knowledge on pancreatitis is based on research conducted using experimental models of pancreatitis. In this review, several experimental models of pancreatitis will be discussed in terms of technique, advantages, and limitations.

The Effects of Combined Treatment with an HMG-CoA Reductase Inhibitor and PPARgamma Agonist on the Activation of Rat Pancreatic Stellate Cells

BACKGROUND/AIMS: Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) and peroxisome proliferator-activated receptor gamma (PPARgamma) ligands can modulate cellular differentiation, proliferation, and apoptosis through various pathways. It has been shown that HMG-CoA reductase inhibitors and PPARgamma agonists separately inhibit pancreatic stellate cell (PaSC) activation. We studied the effects of a combination of both types of drugs on activated PaSCs via platelet-derived growth factor (PDGF), which has not previously been reported. The present study was performed to elucidate the underlying mechanisms of these effects by focusing on the impact of the signaling associated with cell-cycle progression. METHODS: Primary cultures of rat PaSCs were exposed to simvastatin and troglitazone. Proliferation was quantified using the BrdU method, and cell-cycle analysis was performed using a fluorescent activated cell sorter. The protein expression levels of smooth muscle actin (SMA), extracellular signal-regulated kinase (ERK), and a cell cycle machinery protein (p27Kip1) were investigated using Western blot analysis. RESULTS: Simvastatin reversed the effects of PDGF on cell proliferation in a dose-dependent manner. The combination of a low concentration of simvastatin (1 mM) and troglitazone (10 mM) synergistically reversed the effects of PDGF on cell proliferation but had no effect on cell viability. The expression of a-SMA was markedly attenuated by combining the two drugs, which blocked the cell cycle beyond the G0/G1 phase by reducing the levels of phosphorylated ERK and reversed the expression of p27Kip1 interrupted by PDGF. CONCLUSIONS: Simvastatin and troglitazone synergistically inhibited cell proliferation in activated PaSCs by blocking the cell cycle beyond the G0/G1 phase. This inhibition was due to the synergistic modulation of the ERK pathway and the cell cycle machinery protein p27Kip1.

Involvement of Nuclear Factor Kappa B in High-Fat Diet-Related Pancreatic Fibrosis in Rats

BACKGROUND/AIMS: High-fat diets contribute to pancreatic fibrogenesis, but the pathogenesis remains unclear. This study investigated the role of nuclear factor kappa B (NF-kappaB) in high-fat diet-induced pancreatic fibrosis in rats. METHODS: Male Wistar rats were fed a high-fat diet or standard normal chow for 20 weeks. Pancreatic fibrosis was determined by Sirius red staining. Immunohistochemical staining, reverse transcription-polymerase chain reaction and Western blotting were used to identify NF-kappaB-associated genes or protein expressions. RESULTS: Inflammation, fat deposition, pancreatic stellate cell activation and fibrosis were observed in the pancreases of the high-fat diet group. NF-kappaB subunit p65 (NF-kappaB/p65) expression was localized to the nucleus, and intercellular adhesion molecule 1 (ICAM-1) was over-expressed. Pancreatic gene expression levels of NF-kappaB/p65, ICAM-1 and tumor necrosis factor alpha were all elevated significantly in rats fed a high-fat diet compared with control rats. Western blotting also revealed significantly increased levels of ICAM-1 and nuclear NF-kappaB/p65 in rats fed high-fat diets comparison with control rats. CONCLUSIONS: NF-kappaB is involved in high-fat diet-related pancreatic fibrosis.

Etiology, Pathogenesis and Natural Course of Chronic Pancreatitis / 대한내과학회지

The etiology of chronic pancreatitis varies greatly as demonstrated in the TIGAR-O classification. However, due to the lack of correlation and reproducibility between the etiologic factors and the presentation of the disease, it is presumed that individual sensitivity such as genetic predisposition would play an important role in its pathogenesis. Although our understanding on the pathophysiology of chronic pancreatitis is still far from being adequate, we are gaining more insights on its underlying mechanism through active researches related to pancreatic stellate cells, and molecular/genetic studies. Since the clinical manifestations of chronic pancreatitis show significant variation according to its cause, stages of the disease, and presence of local complications, controversy still remains regarding the natural course of chronic pancreatitis and warrants further study. At present, it is generally agreed that acute pancreatitis, recurrent acute pancreatitis, and chronic pancreatitis lie on the same spectrum of the disease.

The effect of anti-hypertensive drugs on the obstructive pancreatitis in rats / Efeitos de fármacos anti-hipertensivos sobre pancreatite obstrutiva em ratos

PURPOSE: To investigate the effect of ACE inhibitor, lisinopril and AT1 blocker, losartan, on the obstructive pancreatitis in rat. METHODS: Acute pancreatitis in rats (n=21) was induced for a common hepatic duct were ligated proximal to its entry into the pancreas and the common bile - pancreatic duct were also ligated near its junction with the duodenum, under ether anesthesia, after which the abdomen were closed. The animals was divided in tree groups, being two treated and control group. The animals was treated with Losartan and Lisinopril at the dose of 10µg/Kg body weight per day, i.p., in a proportional volume, for five days, before and after treatement. RESULTS: The inflammation, collagen deposition in the pancreas of treated animals were smaller, suggesting that the use of antihypertensive agents interfered positively in the depletion of the injury of the pancreas. Scythe showed a correlation between activity of pancreatic stellate cells (PSCs) lower in treated animals when compared to control. CONCLUSION: The pancreatic stellate cells strength are involved in collagen production during acute pancreatitis and why antihypertensive drugs such as lisinopril and losartan may possibly have beneficial effects in reducing pancreatic fibrosis in models of experimental obstructive pancreatitis.

OBJETIVO: Investigar o efeito de um inibidor da ECA, lisinopril e bloqueador AT1, losartan, a pancreatite obstrutiva em ratos. MÉTODOS: Pancreatite aguda em ratos (n = 21) foi induzida por um ducto hepático comum foram ligados proximal à sua entrada no pâncreas e da bílis comum - ducto pancreático também foram ligados perto de sua junção com o duodeno, sob anestesia com éter, após o que abdome foram fechadas. Os animais foram divididos em três grupos, sendo dois tratados eo grupo controle. Os animais foram tratados com lisinopril e losartan na dose de 10µg/Kg de peso corporal por dia, IP, em um volume proporcional, por cinco dias, antes e depois do tratamento com. RESULTADOS: A inflamação, deposição de colágeno no pâncreas de animais tratados foram menores, sugerindo que o uso de agentes anti-hipertensivos interferiram positivamente na diminuição da lesão do pâncreas. Este estudo mostrou uma correlação entre a atividade das células pancreáticas estreladas (CSP) menor nos animais tratados quando comparados ao control. CONCLUSÃO: A força das células pancreáticas estreladas está envolvida na produção de colágeno durante a pancreatite aguda e por medicamentos anti-hipertensivos, tais como lisinopril e losartan pode eventualmente ter efeitos benéficos na redução da fibrose do pâncreas em modelos experimentais de pancreatite obstrutiva.

Pancreatic stellate cells and alcohol induced chronic pancreatitis in albino rats: histological and immunohistochemical study

Pancreatic stellate cells [PaSCs] are myofibroblast-like cells found in the areas of pancreas that have exocrine function. The aim of the present work was to study the pancreatic stellate cells in the exocrine pancreas and to explain their role in pancreatic fibrosis associated with chronic alcoholic pancreatitis. Forty adult male rats were used in this study. The animals were divided into two groups; control and experimental. The experimental group was given alcohol by intragastric tube daily for 8 weeks. At the end of the experiment the animals were sacrificed and the pancreatic tissue was taken, processed and semithin and paraffin sections were obtained. Paraffin sections were stained with H and E, Mallory trichrome and immunohistochemical stains for detection of alpha smooth muscle actin [alpha-SMA] in PaSCs. Eight weeks after alcohol administration, the pancreatic tissue was traversed by thick connective tissue septa. The interlobular ducts were thickened, distorted and dilated. Some pancreatic acini were distorted, dilated and showed vacuolation and degeneration of their acinar cells. PaSCs were detected in three main sites like in control pancreas; periacinar, periductal and perivascular, but they showed an apparent increase in their number, decrease in their lipid droplets and transformtion into myofibroblast like cells with marked expression of alpha-SMA especially in the fibrotic areas. From the present work it was concluded that the cells which were detected seem to be the pancreatic stellate cells which could play an important role in the development of pancreatic fibrosis associated with alcoholic chronic pancreatitis. Therefore, understanding the biology of PaSCs may offers potential therapeutic targets for the treatment and prevention of these diseases

Chronic Pancreatitis with Fibrogenesis / 한양의대학술지

Chronic pancreatitis is an ongoing inflammatory disorder characterized by irreversible destruction of the pancreas associated with disabling chronic pain and permanent loss of exocrine and endocrine function. Fibrosis and loss of acinar cell mass in the pancreas are characteristic findings in chronic pancreatitis, and pancreatic fibrosis is suggested to contribute to the irreversibility of the disease Over the past several decades, several theories have emerged to explain the pathogenesis and evolution of pancreatitis. These models provide conceptual frameworks that are not mutually exclusive, but at times are mutually contradictory. The role of pancreatic fibrogenesis in response to various forms of pancreatic injury and the relationship of fibrogenesis in response to the progression from acute to chronic form is emphasized within the sentinel acute pancreatitis event (SAPE) model of chronic pancreatitis. Studies on pancreatic fibrogenesis have been given new impetus, largely because of the identification and characterization of stellate-shaped cells in the pancreas. In the normal pancreas, pancreatic stellate cells (PSC) exist in a quiescent state. However in pancreatic injury, the PSCs are activated so that they exhibit increased proliferation, transformation onto myofibroblast-like cells and synthesize increased amounts of the extracellular matrix proteins that form fibrous tissues. Therefore, the PSCs have a central role in pancreatic fibrogenesis. Over the past several decades, the pathogenesis of chronic pancreatitis has been studied. However, the pathogenesis of chronic pancreatitis is unclear. Therefore, further studies would be needed to clarify the pathogenesis of chronic pancreatitis..