A novel animal model of severe pancreatitis in mice and its differences to the rat

Experimental Acute Pancreatitis Models: History, Current Status, and Role in Translational Research

Acute pancreatitis is a potentially severe inflammatory disease that may be associated with a substantial morbidity and mortality. Currently there is no specific treatment for the disease, which indicates an ongoing demand for research into its pathogenesis and development of new therapeutic strategies. Due to the unpredictable course of acute pancreatitis and relatively concealed anatomical site in the retro-peritoneum, research on the human pancreas remains challenging. As a result, for over the last 100 years studies on the pathogenesis of this disease have heavily relied on animal models. This review aims to summarize different animal models of acute pancreatitis from the past to present and discuss their main characteristics and applications. It identifies key studies that have enhanced our current understanding of the pathogenesis of acute pancreatitis and highlights the instrumental role of animal models in translational research for developing novel therapies.

Murine Models of Acute Pancreatitis: A Critical Appraisal of Clinical Relevance

Acute pancreatitis (AP) is a severe disease associated with high morbidity and mortality. Clinical studies can provide some data concerning the etiology, pathophysiology, and outcomes of this disease. However, the study of early events and new targeted therapies cannot be performed on humans due to ethical reasons. Experimental murine models can be used in the understanding of the pancreatic inflammation, because they are able to closely mimic the main features of human AP, namely their histologic glandular changes and distant organ failure. These models continue to be important research tools for the reproduction of the etiological, environmental, and genetic factors associated with the pathogenesis of this inflammatory pathology and the exploration of novel therapeutic options. This review provides an overview of several murine models of AP. Furthermore, special focus is made on the most frequently carried out models, the protocols used, and their advantages and limitations. Finally, examples are provided of the use of these models to improve knowledge of the mechanisms involved in the pathogenesis, identify new biomarkers of severity, and develop new targeted therapies.

Experimental Models in Syrian Golden Hamster Replicate Human Acute Pancreatitis

The hamster has been shown to share a variety of metabolic similarities with humans. To replicate human acute pancreatitis with hamsters, we comparatively studied the efficacy of common methods, such as the peritoneal injections of caerulein, L-arginine, the retrograde infusion of sodium taurocholate, and another novel model with concomitant administration of ethanol and fatty acid. The severity of pancreatitis was evaluated by serum amylase activity, pathological scores, myeloperoxidase activity, and the expression of inflammation factors in pancreas. The results support that the severity of pathological injury is consistent with the pancreatitis induced in mice and rat using the same methods. Specifically, caerulein induced mild edematous pancreatitis accompanied by minimal lung injury, while L-arginine induced extremely severe pancreatic injury including necrosis and neutrophil infiltration. Infusion of Na-taurocholate into the pancreatic duct induced necrotizing pancreatitis in the head of pancreas and lighter inflammation in the distal region. The severity of acute pancreatitis induced by combination of ethanol and fatty acids was between the extent of caerulein and L-arginine induction, with obvious inflammatory cells infiltration. In view of the advantages in lipid metabolism features, hamster models are ideally suited for the studies of pancreatitis associated with altered metabolism in humans.

A new experimental rat model of pancreatitis using Ecballium elaterium

BACKGROUND

We originally aimed to determine the beneficial effects of Ecballium Elaterium (EE) on acute pancreatitis; however, we observed negative effects of EE on the pancreas. Thus, we used EE in rats to generate a new model of pancreatitis, which we compared with other established pancreatitis models.

METHODS

A total of 32 Wistar albino rats were used. Rats were divided into 4 groups, each of which contained 8 rats. Group 1 (Control), Group 2 (L-Arginine (LA), Group 3 (LA + EE), Group 4 (EE): Twenty-four hours after that serum parameters were analyzed in the collected blood. Blood samples were transported on mice to the Biochemistry Laboratory following cardiac puncture. The levels of amylase, interleukin (IL)-6, interleukin (IL) 1-β (IL-1β), malondialdhyde (MDA), tumor necrosis factor (TNF)-α, total antioxidant status (TAS), and total oxidant status (TOS) were analyzed. Histopathological analysis: The pancreas and lung tissue samples obtained from the rats. Edema, inflammation, vacuolization, and necrosis of the pancreas were assessed using a scoring system ranging from 0 to 4. Edema, hemorrhage and inflammation of the lung tissue were evaluated using a scoring system ranging from 0 to 3.

RESULTS

Histopathological analysis revealed that edema, inflammation, necrosis, and hemorrhage were significantly higher in the LA + EE group than in the control group. Moreover, necrosis was higher in the rats that received LA and EE compared to the rats that received only LA or EE. Increases in inflammatory mediator levels, including IL-6, IL-1β, TNF-α, MDA, and TOS, were observed in all groups as compared to the control group. Moreover, lower TAS levels were detected in all groups but the control group. The increase in IL-1β and TNF-α levels and the decrease in TAS were statistically significant in all groups (P < 0.05).

CONCLUSIONS

EE may be used to create a successful acute pancreatitis (AP) model, resulting in edema, necrosis, hemorrhage, and inflammation of the pancreas. The major advantage of this model is that it does not require laparotomy, and can be implemented with only an intraperitoneal injection (IP). Moreover, EE may be combined with other agents, such as LA, to create severe pancreatitis. Further molecular studies are warranted to determine the underlying effects of EE on the pancreas.

Diagnostic value of surfactant protein-a in severe acute pancreatitis-induced acute respiratory distress syndrome

Background

The complexity of multiple-item criteria in acute respiratory distress syndrome (ARDS) often causes inconvenience for physicians in the management of patients with severe acute pancreatitis (SAP). We evaluated whether serum SP-A levels in the presence of diffuse alveolar damage (DAD) can be qualitatively assessed for diagnosis of SAP-induced ARDS.

Material/Methods

Eighty rats were randomly divided into 2 groups (n=40 each) – the sham-operated (SO) group and the SAP group – and then randomly subdivided into 4 subgroups in a time-course manner. Furthermore, rats in the SAP group were subdivided into the SAP induced-ARDS group (ARDS group) and the SAP without ARDS group (non-ARDS group) according to the diagnostic standard of ARDS. The diagnostic cut-off values of SP-A for SAP-induced ARDS were determined by the receiver operating characteristic curve (ROC).

Results

Serum SP-A levels in Baseline, SO group, SAP group, ARDS group, and non-ARDS group were 43.15±14.29, 51.91±16.99, 193.4±35.37, 198.0+29.73, and 185.7±43.21 ug/ml, respectively. The best cut-off value for the serum SP-A level for the diagnosis of SAP-induced ARDS was 150 ug/ml and the area under the ROC curve of SP-A was 0.88. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of SP-A in the diagnosis of SAP-induced ARDS were 100.0%, 81.8%, 71.4%, 100.0%, and 87.5%, respectively.

Conclusions

Serum SP-A levels may allow the detection of SAP-induced ARDS and may help to support the clinical diagnosis of ARDS. The optimal serum SP-A cut-off value to discriminate SAP-induced ARDS and other groups (SO group and non-ARDS group) is around 150 ug/ml.

Time course of intestinal barrier function injury in a sodium taurocholate-induced severe acute pancreatitis in rat model

OBJECTIVE

The aims of this study were to clarify the kinetics of intestinal barrier function impairment in sodium taurocholate-induced severe acute pancreatitis (SAP) models and to explore an appropriate concentration of sodium taurocholate and a suitable time point for further study.

METHODS

In total, 104 rats were randomly divided into four groups: the normal control group (n = 8) receiving no treatment, the sham-operation group (n = 32), the 2.5% and 5% sodium taurocholate-treated SAP groups (n = 32 for each group) which were induced via a retrograde injection of 2.5% or 5% sodium taurocholate into the pancreatic duct. Histological examination, serum D-lactate and endotoxin levels and the incidence of bacteria translocation were recorded to assess the intestinal mucosal injury.

RESULTS

Pancreatitis models were successfully established in both the 2.5% and 5% sodium taurocholate-treated groups. The dosage of sodium taurocholate used to induce pancreatitis was positively correlated with the degree of intestinal mucosal injury. The most severe damage to intestinal barrier was observed 24 h after surgery in the 2.5% sodium taurocholate-treated group and 48 h after surgery in the 5% sodium taurocholate-treated group, respectively.

CONCLUSION

Based on the success rate of the model, the mortality and the impairment of intestinal barrier function, we conclude that 24 h after a retrograde injection of 2.5% sodium taurocholate may be the most appropriate time point to study intestinal barrier injury in SAP rats.

Acute pancreatitis: The stress factor

Acute pancreatitis is an inflammatory disorder of the pancreas that may cause life-threatening complications. Etiologies of pancreatitis vary, with gallstones accounting for the majority of all cases, followed by alcohol. Other causes of pancreatitis include trauma, ischemia, mechanical obstruction, infections, autoimmune, hereditary, and drugs. The main events occurring in the pancreatic acinar cell that initiate and propagate acute pancreatitis include inhibition of secretion, intracellular activation of proteases, and generation of inflammatory mediators. Small cytokines known as chemokines are released from damaged pancreatic cells and attract inflammatory cells, whose systemic action ultimately determined the severity of the disease. Indeed, severe forms of pancreatitis may result in systemic inflammatory response syndrome and multiorgan dysfunction syndrome, characterized by a progressive physiologic failure of several interdependent organ systems. Stress occurs when homeostasis is threatened, and stressors can include physical or mental forces, or combinations of both. Depending on the timing and duration, stress can result in beneficial or harmful consequences. While it is well established that a previous acute-short-term stress decreases the severity of experimentally-induced pancreatitis, the worsening effects of chronic stress on the exocrine pancreas have received relatively little attention. This review will focus on the influence of both prior acute-short-term and chronic stress in acute pancreatitis.

Upregulation of IL-1β, IL-6, and CCL-2 by a novel mouse model of pancreatic ischemia-reperfusion injury

BACKGROUND

Little is known about the immunologic events surrounding pancreatic ischemia-reperfusion injury (IRI) because of a lack of established experimental models. The purpose of this study was to develop a mouse model for pancreatic IRI to serve as a basis for the immunologic characterization of pancreatic organ damage at transplantation.

METHODS

Reversible ischemia was surgically induced by vascular isolation of the distal pancreas for 0, 10, 20, or 30 min. Mice receiving laparotomy without clamping served as sham-operated controls. After reperfusion, mice were serially assayed for biochemical and histologic evidence of inflammation, proinflammatory cytokine and chemokine production, and inflammatory gene upregulation.

RESULTS

After induction of pancreatic IRI, serum amylase and lactate dehydrogenase peaked at 6 hr and returned to baseline by 120 hr after injury in all groups. Mice undergoing 30 min of IRI demonstrated the greatest biochemical evidence of inflammation. Histologic scoring similarly demonstrated marked inflammation in mice subjected to 30-min IRI compared with controls. Serum cytokine/chemokine analysis demonstrated significant upregulation of granulocyte colony-stimulating factor, interferon γ, tumor necrosis factor α, interleukin (IL)-2, IL-1β, IL-6, chemokine (C-C motif) ligand-2, chemokine (C-C motif) ligand-5, chemokine (C-X-C motif) ligand-1, and macrophage inflammatory protein 2. A similar upregulation of ccl2, il1b, il6, fos, hspa1a, hspd1, and cd14 gene expression was detected by real-time polymerase chain reaction analysis of pancreatic tissue.

CONCLUSIONS

This novel model of distal pancreatic IRI in the mouse demonstrates time-limited pancreatic inflammation and injury by histologic and biochemical indices. Inflammation may be, in part, a result of the immunologic effects of IL-1β, IL-6, and CCL-2. This model provides a method by which immunologic mechanisms of pancreatic IRI can be elucidated.

Efficacy of celecoxib in the treatment of severe acute pancreatitis in rats

AIM: To investigate the efficacy of celecoxib in the treatment of severe acute pancreatitis (SAP) in rats and explore potential mechanisms involved.

METHODS: A total of 135 Sprague-Dawley rats were used in this study, of which 75 were randomly and equally divided into three groups (SAP model control group, low-dose and high-dose celecoxib treatment groups) to investigate the survival rate, and 60 were randomly and equally divided into four groups (sham operation group, SAP model control group and low-dose and high-dose celecoxib treatment groups) to detect pancreatic histopathological changes, serum tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) levels, and pancreatic expression of cyclooxygenase-2 (COX-2). SAP was induced in rats by retrograde injection of sodium taurocholate into the biliopancreatic duct. The histopathological changes in the pancreas of rats were evaluated using a semi-quantitative scoring method. The changes in serum TNF-α, IL-1β and IL-6 levels at different time points were measured by enzyme-linked immunosorbent assay (ELISA). The expression of COX-2 mRNA in the pancreas was detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: Celecoxib ameliorated pancreatic pathological damage in SAP rats. High-dose celecoxib could significantly mitigate edema at 24 hours (2.28 ± 0.30 vs 2.73 ± 0.22, P < 0.05), acinar necrosis at 12 and 24 hours (2.03 ± 0.15 vs 2.48 ± 0.24 and 2.09 ± 0.10 vs 2.65 ± 0.25, respectively; both P < 0.05), and inflammatory cell infiltration at 12 and 24 hours (1.80 ± 0.22 vs 2.51 ± 0.17 and 1.57 ± 0.26 vs 2.20 ± 0.22, respectively; both P < 0.05). The levels of serum TNF-α, IL-1β and IL-6 in SAP rats were significantly higher than those in normal control mice at all time points. After celecoxib treatment, the levels of serum TNF-α, IL-1β and IL-6 significantly decreased in SAP rats, especially prominent in the high-dose group (P < 0.05). Celecoxib treatment could also improve the survival rate of SAP rats (16% vs 52%, P < 0.05).

CONCLUSION: Celecoxib can ameliorate pathological damage in the pancreas of SAP rats possibly by inhibiting the production of serum TNF-α, IL-1β and IL-6 and the expression of COX-2 in the pancreas.