Figure 6. Increased trypsin activity was the cause of severe pancreatitis in PRSS1^R122H mice.

(A) Enzymatically inactive Dead-PRSS1^R122H (PRSS1^Dead) transgene construct was developed by introducing a S200T point mutation into PRSS1^R122H using recombineering technology. (B) In response to cerulein, Dead-PRSS1^R122H generated the same amount of active trypsin as C57BL/6 mice. Mean ± SEM (n = 3). ***P < 0.001; 1-way ANOVA with Tukey’s test. (C) Schema of cerulein-induced AP in PRSS1^Dead and PRSS1^R122H mice. (D) Enlarged pancreata were observed in PRSS1^R122H mice but not in PRSS1^Dead mice 24 hours after cerulein induction (n = 10). (E) Comparison of pancreatic edema (pancreas-to-body weight ratio) 24 hours after cerulein induction. Mean ± SEM (n = 10). ***P < 0.001; 2-tailed unpaired Student’s t test. (F) Comparison of serum amylase level 24 hours after cerulein induction. Mean ± SEM (n = 10). ***P < 0.001; 2-tailed unpaired Student’s t test. (G) Cerulein caused more severe AP in PRSS1^R122H mice than in PRSS1^Dead mice. Representative images of H&E staining 24 hours after cerulein induction are shown (n = 10). Scale bars: 200 μm. (H) Overall histology score of AP from PRSS1^R122H mice and PRSS1^Dead mice. Mean ± SEM (n = 10). ***P < 0.001; 2-tailed unpaired Student’s t test. (I) To investigate cerulein-induced CP in PRSS1^R122H and PRSS1^Dead mice, the mice were sacrificed 7 days after cerulein induction. (J) Seven days after cerulein induction, all the pancreata from PRSS1^R122H mice shrank (indicating CP), but all the pancreata from PRSS1^Dead mice appeared to be normal (n = 8). (K) The pancreas-to-body weight ratio 7 days after cerulein indicated that the pancreata in PRSS1^R122H mice were much smaller than those in PRSS1^Dead mice. Mean ± SEM (n = 8). ***P < 0.001; 2-tailed unpaired Student’s t test. (L) At day 7, histologic examination (H&E staining) demonstrated chronic damage in PRSS1^R122H mice, whereas the pancreata of PRSS1^Dead mice were normal (n = 8). Scale bars: 200 μm.