A mouse model of severe acute pancreatitis induced with caerulein and lipopolysaccharide

Abstract

Aim: To establish a non-traumatic, easy to induce and reproducible mouse model of severe acute pancreatitis (SAP) induced with caerulein and lipopolyasccharide (LPS).

Methods: Thirty-two healthy mature NIH female mice were selected and divided at random into four groups (each of 8 mice), i.e., the control group (NS group), the caerulein group (Cn group), the lipopolysaccharide group (LPS group), and the caerulein+LPS group (Cn+LPS group). Mice were injected intraperitoneally with caerulein only, or LPS only, and caerulein and LPS in combination. All the animals were then killed by neck dislocation three hours after the last intraperitoneal injection. The pancreas and exo-pancreatic organs were then carefully removed for microscopic examination. And the pancreatic acinus was further observed under transmission electron microscope (TEM). Pancreatic weight, serum amylase, serum nitric oxide (NO) concentration, superoxide dismutase (SOD) and malondialdehyde (MDA) concentration of the pancreas were assayed respectively.

Results: (1) NS animals displayed normal pancreatic structure both in the exocrine and endocrine. In the LPS group, the pancreas was slightly edematous, with the infiltration of a few inflammatory cells and the necrosis of the adjacent fat tissues. All the animals of the Cn group showed distinct signs of a mild edematous pancreatitis characterized by interstitial edema, infiltration of neutrophil and mononuclear cells, but without obvious parenchyma necrosis and hemorrhage. In contrast, the Cn+LPS group showed more diffuse focal areas of nonviable pancreatic and hemorrhage as well as systemic organ dysfunction. According to Schmidt's criteria, the pancreatic histologic score showed that there existed significant difference in the Cn+LPS group in the interstitial edema, inflammatory infiltration, parenchyma necrosis and parenchyma homorrhage in comparison with those of the Cn group, LPS group and NS group (P<0.01 or P<0.05). (2) The ultrasturcture of acinar cells was seriously damaged in the Cn+LPS group. Chromatin margination of nuclei was present, the number and volume of vacuoles greatly increased. Zymogen granules (ZGs) were greatly decreased in number and endoplasmic reticulum exhibited whorls. The swollen mitochondria appeared, the crista of which was decreased in number or disappeared. (3) Pancreatic weight and serum amylase levels in the Cn +LPS was significantly higher than those of the NS group and the LPS group respectively (P<0.01 or P<0.05). However, the pancreatic wet weight and serum amylase concentration showed no significant difference between the Cn+LPS group and the Cn group. (4) NO concentration in the Cn+LPS group was significantly higher than that of NS group, LPS group and Cn group(P<0.05 or P<0.01). (5) The SOD and MDA concentration of the pancreas in the Cn+LPS group were significantly higher than those of NS, LPS and Cn groups (P<0.05 or P<0.01).

Conclusion: The mouse model of severe acute pancreatitis could be induced with caerulein and LPS, which could be non-traumatic and easy to induce, reproducible with the same pathological characteristics as those of SAP in human, and could be used in the research on the mechanism of human SAP.

Figure 1

In the LPS group, the pancreas was slightly edemamous. ×100.

Figure 2

Microscopic section of the pancreas from the Cn group, showing the features of acute edematous pancreatitis notably interstitial edema. ×100.

Figure 3

In the Cn+LPS group, more diffuse focal areas of nonviable pancreatic parenchyma appeared obviously. ×100.

Figure 4

The histological change of the exo-pancreatic organs in the Cn+LPS group. A: Renal cells were swollen; ×100; B: The vacuoliza-tion of liver cells; ×400; C: A lot of erythrocyte and inflammatory cells also infiltrated in the cavity of pulmonary alveolus. ×100.

Figure 5

A few cytoplastic vacuoles formed in acinar cells in the LPS group. × 10000.

Figure 6

In the Cn group, a few cytoplastic vacuoles in acinar cell appeared, and ZGs were decreased in number. The RER and the mitochondria was slightly swollen. × 10000.

Figure 7

The ultrastructure change of the pancreatic acinus in the Cn+LPS group. A: Chromatin margination of nuclei was present, the swollen mitochondria appeared; × 7000; B: the number of vacuoles greatly increased and their volume also greatly increased; × 7000; C: the endoplasmic reticulum exhibited whorls; × 14000; D: The crista of mitochondria was decreased or disappeared. × 20000.

Figure 8

Comparison of NO concentration between groups(^-x ± s) (n = 8). ^aP < 0.01, vs NS group; ^bP < 0.01, vs LPS group; ^cP < 0.05,vs Cn group.