An Obstructive Chronic Pancreatitis Model Established Through Electrocoagulation

There are many methods for building animal models of chronic pancreatitis, including intraperitoneal injection of sodium and the ligation of pancreatic duct, which have their limitations. Our team recently developed a new electrocoagulation model of chronic pancreatitis in mice, which has advantage that it doesn't require long-injection drugs or difficult method to master. And they can easily establish a chronic pancreatitis model.

The use of electrical coagulation to induce chronic pancreatitis in mice provides a more convenient and experimental model, offering a promising avenue for future research in this field. To begin, place the anesthetized mouse on a heating pad to maintain body temperature. Using a trimmer, shave the hair between the chest and lower abdomen.

Next, use scissors to make a two-centimeter-long incision in the central abdomen, followed by a one-centimeter incision between the upper abdomen and the xiphoid process. Use an abdominal expander to locate the area of the pancreas for electrocoagulation. Using a sterile cotton swab, identify the duodenum from the rear of the left upper abdomen and turn it to visualize the bile duct connecting the liver.

Temporarily occlude the proximal common bile duct using a microvascular clip to prevent retrograde infusion into the liver. Connect the 0.25 by 0.35-millimeter polyethylene pipe to a 0.25-millimeter needle and pierce the ampulla-surrounding area, aiming for the large duodenal papilla. Insert the tube into the papilla and pass it halfway into the bile duct, then stop the entry.

Start the infusion pump, and infuse 0.2%methylene blue solution until the pancreatic duct becomes blue. After infusion, pull the polyethylene tube out and remove the microvascular clip. Use sterile cotton swabs to fix the pancreas, and direct the electrocoagulation knife to the blue-colored area.

After setting the operating parameters of electrocoagulation, use pure copper as the electrode material and apply treatment to the pancreas for two to three seconds while avoiding blood vessels. Continue electrocoagulation until the methylene blue-stained region changes color to yellow or brown. When the blue staining solution is no longer visible in the pancreas, stop the electrocoagulation.

After the surgery, place the mouse in a polyethylene box lined with bedding material. After electrocoagulation of the pancreatic duct, anesthetize the mouse and place it on an operating platform. To collect blood through the orbital plexus, gently hold the skin on the back to create a slight protrusion of the eyeball.

Then, place the end of a capillary tube in the corner of the eye and gently insert it under the eyeball at an angle of 30 to 45 degrees. Rotate the capillary until blood starts to flow. After blood collection, close the eyelids by applying gentle pressure with gauze.

Centrifuge the blood at 1, 200g for 15 minutes and collect the supernatant in a new tube. Measure amylase, bilirubin, and hyaluronic acid using commercially available kits, following the manufacturer's recommendations. Next, place the euthanized mouse on the operating table set at four degrees Celsius.

Using scissors and forceps, make a V incision in the abdominal wall to expose the abdominal cavity. Remove the pancreas and divide it into three parts for staining. Fix the pancreas in 4%polyformaldehyde solution, then embed the fixed pancreas into paraffin for sectioning.

Cut the paraffin blocks into 0.5-millimeter-thick sections and stain them with hematoxylin and eosin, as well as with Masson's stain for immunohistochemical analysis. Observe the stained pancreatic tissue under a light microscope. Hematoxylin-eosin staining showed scattered pancreatic acinar cells and evidence of chronic pancreatitis in the electrocoagulation group on day 14.

On day 28, signs of tissue recovery and reversal of pathology in the pancreatic acinar cells were observed. Masson's staining revealed significantly more fibrosis in the electrocoagulation group compared to the sham group. Immunohistochemical staining showed elevated alpha one, type one collagen and alpha smooth muscle actin levels in the electrocoagulation group, indicating a higher degree of chronic pancreatitis.

Hyaluronic acid levels increased in the electrocoagulation group, peaking around day 21, while remaining stable in the sham group. The bilirubin levels rose significantly by day 14 in the electrocoagulation group, showing a peak around day 21, whereas the sham group showed no changes. Amylase levels in the electrocoagulation group spiked on day 14, followed by a decline by day 28, with the sham group showing little variation.